I'm a firm believer to always isolate a battery when using a 220V AC charger, regardless whether using 1 or multiple battery systems. It simply eliminates any possible issues from occurring. Thanks for the heads up Andrew! :)
This is so critical: as is clearly shown by Andrew's example. It's also the safest approach. I'm also a bit surprised at the notion of using solar to charge the crank battery. I'm more used to using solar and DC/DC chargers to charge the house batteries and isolating the crank battery so there are no loads on the crank battery other than originally intended by the manufacturer. The alternator should always be sufficient to charge the crank battery. Some alternators supply a varying amount of current, depending on their temperature.
Same here. If I am going to charge my starter battery with AC charger or solar panel, I always disconnect the wires from the negative terminal of the starter battery first.
All good info Andrew, I have had many problems to solve with battery issues as well. But I must say that it has been about 50 years since I left an ignition turned on with the motor off. I always use the trigger wire and a solenoid to connect the BC-BC. Cheers! Good Stuff!
In my setup I have a breaker where your fuse is and I can quickly switch off the Aux circuit when I need to charge the main battery and often leave it off where not on trips just using the roof solar to keep the Aux topped up.
How is the apparent charging voltage being maintained? As soon as the 50amp charger turns on it should pull the voltage down to just the battery voltage plus a little for the amount of power the charger can put in. Unless the DC to DC charger is set to run down to 13.2V or something that shouldn’t let the starter battery discharge to below where it can crank over your cruiser. If it is set to a very low cut off Voltage there should be a way of turning that up, with your setup the charging voltage shouldn’t fall below about 14v. Try measuring the voltage at the starter battery with theAC to DC and the DC to DC chargers running
David Cocks yep I saw a bunch of comments saying they were doing the same thing and I definitely believe it but I don’t see why you would want it to keep charging down to less than 13.5v probably higher if you have a powerful alternator the little 70w one in my ute easily holds 13.5v at 50A draw (I checked) and that is where I set my minimum. I only have a 5A charger and a 50A charger for AC the 5A only adds about 0.25V if the DC to DC is working flat out. But I can see a 10A one allowing the battery to go down below 12V with a 50A DC to DC one running if the DC to DC goes down to a really low voltage before shutting off. (my DC to DC is a dodgy Chinese one with a potentiometer each for the charging voltage cut offs (start-stop, drop, fast charge, slow charge) and dip switches to select other stuff and it says it will do 45A but it only does about 30 on any battery setup I have tried it on.
The battery charger is sending 14v 10 amp into the battery The 14v triggers the dc/dc the drain The dc/dc is only looking for 13v so.even thoigh the main battery is dead flat the charger is providing that voltage signal It could maybe be set to trigger a fault because of low amperage input but currently they're only set to look for that voltage signal
Glen Collins, I do agree with you. It is impossible, voltage must drop the moment the load exceed the maximum Amp the AC charger can supply. But the question remains, how does the crank battery then discharge? It just does not make sense?
CampX4 & Outdoor TV it’s being pulled out of the battery by the red arc DCDC and milking it flat as the 10 amp ac charger is trying keep up with THE 50amp load pulling through to the auxiliary, whilst this is going on the ac charger constantly sees a huge hole, tries in vain to fill it and cranks max voltage and amps into the bottomless pit.
I have the solution for you Andrew. I tow a camper trailer and in it I have a redarc BCDC40 to charge the two 100 Ahr AGM deep cycle batteries simply because of the distance from the car alternator and the resulting voltage drop. The problem is exactly the same, if the batteries in the camper were not fully charged when you stopped the DC to DC would drain the auxiliary battery to charge them. To overcome this I have a 100 amp relay mounted in the back of the car prior to the anderson plug which is switched through an oil pressure switch so it will never charge from the cars auxiliary battery, in my case, unless the car is running, even if you leave the ignition on accidentally. Luckily I found this out when researching the wiring and installation of the dc to dc charger before the actual fitting and it works perfectly. You could do a similar thing in your vehicle.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
@@4xoverland I charge the aux batteries first. I have 360ah batteries charged via solar /Redarc BCDC1240. I also have a built in 30amp Victron mains charger, connected to the Aux batteries. If I ever need to charge the crank battery (which is rare) I have an alternator friendly switch to parallel the aux & crank batteries via 70mm2 cable (for extended electric winch use) , but it also doubles as a means of charging the crank battery when switched to parallel.
Andrew, this doesn't make sense. I have basically the same setup and haven't experienced this problem. Typically DC/DC Chargers will switch off and stop charging the aux battery when the input drops below 11.8 volts. They typically won't turn on unless the input voltage is above 13.1 volts. So when you connected your mains charger to the battery, yes the voltage would have risen above 13.1 volts and the DC/DC charger would have turned on. This is the same principle and operation of the old Voltage Sensing Relays (VSRs). However, it's understandable that your mains charger would not have been able to cope with the load (current draw) of both batteries (if both were discharged). But what should have happened, is that the voltage from your mains charger would have progressively dropped as it wouldn't have been able to maintain the output current required to charge both batteries. Once the mains battery (with mains charger connected) dropped below 11.8 volts, the DC/DC charger should have turned off. The mains charger would then have been able to again start charging the main battery and the internal resistance of the battery would start rising and so would its voltage (Ohms Law). Once it reached 13.1 volts, the DC/DC charger would kick in again, and the whole sequence would start again. The end result over time, should have been that both batteries would be fully charged. So what's happened in your situation is a bit of a mystery.
The charger would have been connected to the same terminal as the DC-DC, so the DC-DC would've been seeing the input voltage of the charger this draining the battery. The charger would've been giving the DC-DC a false voltage reading of the main battery. The only way to get around this is to disconnect the DC-DC
@@nickscurr7062 My understanding is that external charger was connected in parallel to both the main battery and the DC/DC charger. So I still ask the question, why didn't the DC/DC charger turn off when the main battery and external charger voltage dropped to 11.8 volts. The external charger and main battery cannot have different voltages when connected together. Is there something here I don't understand? (I used to be an electrician...but not a very good one...LOL!).
4 года назад+1
@@FastFless I'm afraid there is some "misunderstanding" between the DC/DC and the small charger (like pulse charging in the small charger that causes the voltage to raise repeatedly above the DC/DC switchoff levels). It is actually very unfortunate that both the devices are from Redarc and they don't work together!
@@FastFless , if the 10 amp charger was a simple linear constant current 10 amp device, then I believe it should be just as you have described. There must be something funny about the way the charger is delivering the charge that is tricking the DC/DC charger into staying on. It would be interesting to connect an oscilloscope and see exactly what is going on.
Not an issue with CTEK 250sa with smartpass check it out ! Have had ctek on my cars now for 7 years and never flat batteries, and my car is not a daily driver either.
CTEK also recommend attaching the float charger to the Aux battery side. The same can happen with CTEK if your float charger is able to lift the main battery voltage.
Thank you Andrew I have just discovered your channel. This should end a long running debate among my friends. I had warned one of my friends that sitting on the beach listening to the test cricket will flatten your battery. It had happened to me. I suspected the trigger wire as you explain but he was adamant that the load from the radio could not possibly drain his starter. Sure enough I had to give him a jump start but he still didn't believe it was the radio at fault. Now we know it was probably a flat auxiliary combined with the the trigger wire connecting the two batteries.
Love what you are doing with this series Andrew! Could you do a video on what compulsory maintenance we should be doing before trips? I am not very Mechanical savvy and would love a guide. Thanks.
Thanks for the info. In my situation I have my start battery purely for starting only. (Nothing connected besides low amp accessories on switches) the start battery will also be monitored. Then from my starter battery, it then connects to a smart isolator before connecting to my secondary battery. The second battery then has all the niknaks. This works only for older cars.
Many thanks for the heads up on this. Just a couple of weeks into a van to camper conversion. I will add in an isolator in the circuit just to be sure. I was always taught never to leave the ignition on, that stems back to old petrol cars where depending where the points were your coil could burn out. We used to pull the coil wire off if we had to tow a dead car for the same reason.
I also have a Ctek 250sa DC to DC charger hooked up to a solar panel (because it's not a daily drive) it charges the 2nd battery and when that's charged it starts charging the start battery.
Exactly. Take any overflow from auxiliary battery bank back to the starter battery. I’m looking at a dual-sensing VSR for this purpose. The Jaycar one has cut-in at 13.3V and cut-out at 12.8V.
Great video, Andrew and some excellent tips for us all. I'm using a manual cutoff switch in the dash for the DC-DC charger so that I can override the charger even when igintion is on.
I was installing a BCDC 1225 this weekend, and found your clip pretty interesting. My install was in a camper, and it got me thinking… This issue looks like the starter battery needs to be better isolated from the house battery, and possibly it makes sense to treat it like a camper install and use a solenoid or an SBI to only link them when the ignition is on?
U should have ur BCDC charger on the trigger switch u mentioned. The trigger switch can also be connected to a wire that only receives voltage when the car is running. U could also add a breaker so as the BCDC charger doesn’t see the voltage when ur trying to charge ur main......
I love DC-DC chargers, but thought it to be common sense to isolate the primary and aux batteries before connecting a 220V charger anywhere in the system, even if charging the aux battery/s and the DC-DC charger won't let current through to the primary. I always run a 12V 60A circuit breaker between the two battery systems, this way you can even use two 220V chargers at the same time to maintain both sets of batteries whilst the vehicle is not in use for some time.
Andrew, possible solution, mount a solar panel on your garage roof and run cables down for easy connect on to the yellow cable (solar input) on the Redarc. When the Redarc sense solar input, it will not accept input from the main battery. Therefore, as long as you only have your 10amp start battery charger on at the same time as the solar connected to the aux, then you will effectively have separated charging of batteries. Regards, Sean
Another, solution, in the red line between the start battery and the Redarc, add an old style silver 100 amp continuous duty solenoid (the type we all used to used in simple dual battery set ups years ago) then trigger this from the windscreen wiper motor. Then, the start battery can only feed the Redarc when the engine is running.
i have no problems,my dc todc charger wont draw onece it reaches 10.5 volts,plus i use a dedicated deep cycle battery charger,it will charge two 120 amp hour batters plus the start battry,correct your set up.you may need a voltage sensative relay.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
NOTE. I chatted to the guys at Redarc and with Heiner. There is no mystery why this happened. It happened exactly why I said it did. It's a perfectly logical explanation. This is not a Redarc issue. I'm just using Redarc DC-chargers in my setup. All DC-DC chargers will do this because they rely on reading the voltage across the main battery to turn on. And if you use a trigger cable from the ignition, the start battery can be discharged if the ignition is left on, with the same result. The solution is very simple: if you have a DC-DC charger, if you want to charge the batteries without the engine running, charge the auxiliary battery first. What could be simpler?
Just follow the wiring diagram like everyone else and use the ignition trigger wire to turn the system on. If the ignition is turned off, no problem. Not sure why anyone would leave the key turned to ignition if the car isn't running.
So the solution - if you need to charge the start battery is to disconnect "aux" battery - before or after the BCDC - before charging the start battery (a good use case for a simple disconnect). (my BCDC Redarc 1225D is on Anderson connectors.) (NB - Redarc calls their system "Battery Charger Direct Current - BCDC, others call their units "Direct Current to Direct Current" Charger - DC-DC) Blue Trigger cable is specifically for low voltage / smart alternators.
I don't know if in any car. But in my VW T5 there is a D+ wire, which is a "alternator running" signal. From the factory the second battery charges only when the alternator is running. So not on ingnition. I thought there is a signal cable like this in any car.
Fascinating! Thanks for sharing your knowledge. This situation is certainly not one that people would immediately expect to occur. I’m about to design and roll out a system into a 4WD van and I will certainly put an isolation switch between the crank battery and my custom goodies - even just if starting with jumper leads etc I don’t want the aux system taking some of that load away.
Oh - before I forget, and hopefully this helps someone - I reckon if you want to hook up that ACC wire to trigger the DCDC, hook it up to Ignition / ON position instead. That way if you’re sitting in the car in ACC mode listening to the radio, your crank battery isn’t being drained to charge the aux battery.
Well spotted Andrew. This is a big problem with DC-DC chargers. The charger will continue to run when the car is switched off as the cut off input voltage is 12.4v. Once the input drops below 12.4v the charger will stop until it reaches 13.4, however this often means your primary/starter battery is sitting around %70 SoC which is not a good place to be when it comes to starting big engines. For example: You have a 110A alternator, 100A isolated aux battery, a BCDC1240 charger, and a fridge. You pack the fridge a few days before going away and its on full time to get to temperature. The only driving you're doing is to the shops and back, perhaps an hour a day. If it's just bussing around locally, your alternator never gets consistent high RPM so its average output is around 30-50A (most are
I honestly thought everyone knew this....The clue is in the ‘voltage sensing’ aspect of the DC-DC. Also, DC-DC does not charge at 50 amps. That is simply the maximum it can charge at. The charge delivered depends on the aux battery’s state of discharge.
I typically see 5ish amps from my alternator? Would you say thats pretty low? I do have issues with power as dashboard and electrics turn off 10mins into night driving and come back on with battery light
great info, Thank you! I am in the process of switching over my dual battery system due to the Tacoma smart alternator. This time I will place my second battery in the bed with a DC/DC charger............
Hi Andrew. I'd suggest re- approaching Redarc with regards to apsolute clarification as to this blue wire and voltage cut off. Someone has to be wrong, otherwise state of the art Redarc starts to look like well outdated Redarc (and any other dcdc charger that works in a similar way). I truly believe it's not Redarc as instructions despite not being so clear, suggest it's all down to this blue wire not being connected. Now a great video would be to connect the blue wire and do the same test, then try with the ignition left on to test voltage cut out, or as the case may be no voltage cut out with a mains charger connected.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
@@4xoverland Yes true, it is a simple solution. However I'm more thinking along the lines of alternator output - I'm running a smart alternator as fitted by Mr Toyota, if I remember correctly you have changed yours or was that just the Africa terrain tamer build? So a smart alternator can drop output to something like 8 or 9 volts, is there a scinario where by your starter battery can be fully charged in the eyes of the smart alternator however your aux batteries are near depleted and the dcdc charger pulls your starter battery down to a point where by it can no longer start your engine despite the alternator still effectively charging? My theory is the smart alternator should be smart enough to figure this out and fast enough/be able to provide enough amps to starter battery to cope. Scinario 2 - your alternator becomes defective and cannot provide enough amps to keep your starter battery topped up, the dcdc charger will happily help kill the starter battery much quicker, this drops to a point where your vehicle electrics cannot run and your lose engine and all "factory" vehicle power. (It would happen anyway but the dcdc has made it happen much quicker. O.k. alternator failure isn't that common without warning and if it did happen your red dash charge light comes on so you can pull the dcdc fuse and potentially divert solar power to give the starter battery some form of charge - that would be pretty pointless in the U.K though, with our weather! Perhaps I'm overthinking the perfect storm combination? I think I'm into my 6th or 7th year of unbroken patreon support for you Andrew. Keep doing what you are doing, we all get a great amount from your videos. I truly like the fact you are unbiased and not worried about saying the truth. Do you have any future trips planned with Mr Paul Marsh? Stay safe and let's ride this storm out one way or another...
Andrew, I realise you've identified the issue, but here's a suggestion for the future. I've fitted an Enerdrive 240v charger in the canopy of my Silverado. It has 3 separate "channels" for charging 3 separate banks of batteries. I have a somewhat similar set-up to you... A Redarc BCDC1225L and solar panels on the roof of the camper. When I plug the 240 volt cable into the caravan-style receptacle, the Enerdrive charges the Lithium battery, which is set to Channel One (in the canopy) first. It has the ability to choose what type of battery is being charged. Once the lithium battery is charged, it then turns its attention the Channel Two, which is the twin under-bonnet starting batteries. To achieve this latter function, I've simply tapped the Channel Two supply line into the cable that supplies the BCDC with its power from the front batteries. In your case, if you go ahead with another lithium battery (inside the canopy of your truck), then you can utilise all three separate channel of the Enerdrive. If you're interested in my Chevy, here's a write-up that was done a year or so ago: loaded4x4.com.au/issue-002#61
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
Good to know. I knew there was a reason why I hooked up the optional manual disconnect switch. Thanks! In my case I’m charging a travel trailer with the tow vehicle - so the protocol needs to be always unplug the umbilicals when not needed.
VIDEO RESPONSE to Andrew: please search for "Dual battery charging issues VR: 4XO DC-DC CHARGER WARNING. Avoid a runaway discharge." on youtube. Shows what some DC-DC chargers do when configured in similar circumstances.
@@gotoylc This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
@@blastar55m3 This is a very obvious setup issue. There’s a relatively simple device to install to prevent, 100%, this particular issue from ever happening. Unfortunately I do not know Andrews full setup, so perhaps the setup is not correct correct, or there’s an item overlooked and not installed. Andrews setup diagram would be useful on this issue.
Thanks Andrew, I was wondering what my problem was as the Main battery was often low on voltage. After watching your vid I went and checked my set up and it was so. I am now going to instal a relay controlled by ingnition to circumvent this.
It may be worth noting that every time you charge this way you are depleting the crank battery far too much even if you leave it on for the full cycle. It's being drained way down then recharged slowly, bad practice. Better to charge house batteries separately.
If you pull 50amps from you starter battery, the voltage on the starter battery will quickly drop below 12.8V (or whatever) and your DCDC charger should sense that and switch off. Charger is puttting 10amps across, pull out 50amps - voltage will drop quickly. Mine does (Projecta DCDC). Why doesn't yours?
I think in this case the Battery charger was keeping the Main battery at a high enough voltage for the BCDC to keep pulling current out - it probably cycled several times sucking all the input "juice" out of the main battery. - could be wrong. (leaving it "nearly flat" over the charging time)
@@brianostwald802 Dead right Brian, I use the simple old smart voltage solenoid No Worries, why complicate a simple need with an expensive & complicated piece of Bling Mate.
Jason Shepherd The voltage at the battery needs to lower than 12.7 for 10 seconds before the dcdc will shut off as it has a delay built in. Even if the ac charger dipped in voltage under load it would sense it and crank up voltage to compensate within that time window of 10 seconds and kick it up over 12.7 + , therefore dcdc charger keeps on pulling the load.
@@aussiedrifter he needs the DC DC because he's running a lithium battery. The alternator with a VSR would cook the lithium battery BMS or the cells quickly plus the battery may even burn the alternator.
Another good video thanks Andrew. What I did was to install an old school 2nd battery solenoid, the old silver can type which only activates when the ignition is on. And yes you do have to charge the deep cycle separately if it is low. Cheers.
blue wire has to go to ignition so the battery charges from alternator when ignition is on and solar/external chargers when ignition is off. If you leave the ignition on by accident, the start battery will only drain until it reaches the cutoff voltage and then switch itself off as per usual. The only time you will run into trouble this way, is if you have an external charger/solar AND leave the ignition on. Maybe look at the official redarc wiring diagrams or speak to them before you start blaming the charger for your own mistakes
Dion. I know you want to have a go at me here, but you are making several incorrect assumptions. The first one is that I didn't check with Redarc. I did. And they confirmed my assumptions face to face. The others is that you are incorrect with regard to how DC-chargers work. The point is simply, if a charger is attached, the cut-off voltage is not reached until the battery is almost fully discharged. May be check things before you start blaming me for your inability to accept that you don't know everything.
@@4xoverland My bad mate, just read through the manual and I thought the blue wire was a trigger in the sense that it would turn the unit on and off (same as the blue override wire in the sbi12). It actually just adjusts the voltage at which the unit will turn on and off. I just couldn't get my head around the fact that a simple on/off trigger isn't a function of these fancy dc-dc chargers
@@Infuri96 No worries. Like everyone, I'm just trying to get my head around these things and share what I learn. Handling baseless accusations is the single most difficult part of sharing knowledge and experience on RUclips.
This is really a new problem when the auxiliary battery is Lithium. Previously the AGMs commonly used would rarely accept 50 amps charge, no matter what the rating of the DC-DC charger. The solution is simple - if you can afford Redarc 50A DC-DC charger (most of us can't, and are perfectly well served with a 20A unit) you can afford a 50A AC battery charger. End of issue. You can also wire up a dash switch into the IGN trigger wire so you can manually override on those occasions when you need to leave the IGN on for long periods.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
Will this happen with duel sensing dc to dc Chargers my solar input on the dc to dc will also charge the start battery no need to connect solar to the start battery
Makes perfect sense, thanks. Simply put, attaching the external battery charger brings the voltage of the main battery over the 'turn on' voltage for the BCDC. The BCDC will start pulling current from the main to charge the Aux. It does so at a rate higher than is being supplied to the main battery from the external charger. If I ever do need to charge my main from an external charger, I will pull the fuse from between the main battery and the BCDC. Probably a good idea if jumping from one battery to another. Cheers
Thanks for the video. I will now put an Anderson plug in my engine bay connecting from my main battery to my dc to dc charger so I can unplug it if I need to charge main battery.
One can also add a switch on the positive lead connecting the redarc to your start battery. Turn it on or off to disconect the redarc to the starter battery and charge it without. Anyways, thanks for sharing the experience, dmuch preferablento learn it from you than in the trail.
Andrew, I believe there may be 2 possible issues causing this problem you either have a faulty Redarc DC-DC charger or the DC-DC charger may have a design flaw. When the DC-DC charger starts charging the Aux battery and it has a 50A capacity and the AC charger is only 10A this will cause voltage drop and the DC-DC charger will start draining you start battery as you have experienced, but what should immediately happen at this point (12.7V) is the DC-DC chargers low voltage cutout should trigger and stop charging the Aux battery until the starter battery voltage has recovered (13.2V) and then the cycle will continue. This would normally prevent the starter battery from being discharged which seems to not be occurring in your case. The AC charger should not be tricking the DC-DC charger, once more current is being drawn then the AC charger can supply the voltage of the circuit must drop, its physics. It seems the low voltage cutout on your DC-DC charger is not operating correctly. This leads me to believe your DC-DC charger either has a fault or a design flaw. I am happy to be proven wrong if this is not the case. It would be interesting to take some multi-meter readings of the system when this is occurring and see what is actually happening. All the best in solving this problem.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
@@4xoverland It's a problem, whether or not you think it is, and whether or not you're trying to solve it. If your DC-DC charger has a correctly functioning low voltage cutoff (and I would not buy one which does not, if ever using a battery as input) then it will NEVER drain the battery it is drawing from. You don't have a properly functioning low-voltage cutoff on your DC-DC charger, plain and simple. If that's what you intended when buying it, fine, it's performing exactly as you planned when it drains your battery, and there's no problem to solve. But why buy and set up a system to do that? Trick it into turning on as often as you want with a feeble AC charger boosting the vehicle battery voltage for a second, it should still shut off when the 50A draw drops the vehicle battery voltage of a half-dead battery a second later. Even then, you'd better hope that the DC-DC charger has some sort of timeout on restarting, or it might be hammering your battery a few times per second, for instance spending 0.1 seconds with your battery losing 40A, and 0.4 seconds gaining 10A. Over and over.
User-induced issue. There are many ways to do it correctly and one way to do it incorrectly (by triggering the dc-dc with a tiny mains charger on the starter side). Either isolate when shore charging starter batt with a tiny mains charger or use a mains charger of the appropriate size. Or charge aux back from mains with a dc-dc that maintains starter batt. Patient: it hurts when I do [this]! Doctor: stop doing it and it won't hurt anymore.
So this occurs when the DC/DC charger senses the (higher) voltage but not low current output of a small charger, and then "decides" to charge the auxiliary battery, which is in a state of discharge? Interesting problem
Thank you Andrew, I always follow your channel with great interest and I particularly appreciate your willingness to share freely your knowledge and insights. I would be equally keen to hear expert opinion from Redarc on your observations. Presuming you have this would you share those with us too perhaps?
Here’s what Redarc said.... In regards to the connection of the blue trigger wire on BCDC, the following needs to apply: 1) If your vehicle has a standard alternator type (fixed voltage), the blue wire can be left disconnected 2) If your vehicle has a smart alternator type (temeprature compensating or variable voltage), the blue wire needs to be connected to an ignition source 3) If you are unsure of what alternator type you have, it is best to connect the blue wire to ignition We have indeed seen the video mentioned and it does explain the connection of the blue wire, just not in great depth as to how it operates.
This is why i've always installed a DC-DC behind a separate VSR Or relay that is operated by the ignition When maintenance charging at home, i connect to the Aux Batt via an Anderson in the rear
Interesting. I can see how attaching a trickle charger would provide a falsely high voltage reading and cause the DC/DC system to start charging the camper batteries but I'm surprised that it doesn't detect subsequent voltage drops and then shut down again. I mean, your battery's sitting at, say, 12.7v, you connect the charger and the voltage will go up to, perhaps, 13.2v. The DC/DC system detects that increase, realises the starter battery is being charged and starts charging the camper batteries. Even with the charger connected, as the starter battery goes flat the detected voltage SHOULD drop from 13.2v to 13.1v and then to 13.0v and so on. You'd think that the DC/DC system would be capable of realising it was sucking out more leccy than was being pumped into the starter battery and shut down. Hope this isn't a sign of future electrical gremlins in your new truck. I've heard some horror stories about Lithium batteries from people who're smart enough to know what they're doing.
As an Electronic technician here is some good advice for you. Never , ever charge your battery in your vehicle with an ac wall charger while it is connected to your vehicles electronics. The reason is that if for what ever reason you would have a voltage increase from the mains power or thermal runaway then you would fry your vehicle electronics. Always remove the vehicle positive terminal from the battery. You can however jumpstart from another vehicle like you would be doing right now. DC to DC chargers is for DC to DC.... not AC to dc to dc.. If your vehicle battery only was flat then you will need approximately need 10 to 15 hours on 10 amps to charge the first battery. Adding more batteries does double and triple the charging time. For an example. Drawing 10 Amps for 2 hours from a 100 amp hour battery means that you have used about 20% capacity. Charging the same battery with 10 amps will not fully charge that battery within 2 hours because as the battery gets fuller, the amps drop to eventually you will only be charging at about 1 or 2 amps. The time taken to charge the battery will be at least 8 hours.
I am in the process of changing my VSR for a 20A DC-DC, I was planning on using a DPDT switch or relay so that by default the camping batteries, when above trigger voltage (ie being solar charged) will keep the start battery full. When the vehicle is started, the relay will be triggered (by ignition switch) and reconfigure the DCDC to charge the camping batteries effectively from the alternator.
Andrew keep the VSR and and the DC DC charger behind. It isn't costing you any extra. Just apply the following wiring from redarc as if your DC DC charger was not in the same vehicle and that way you have a redundancy for cut off circuit. www.redarc.com.au/wiring-diagrams/how-to-wire-bcdc-caravan-vehicle-variable-voltage-alternator I wired the my wife and mine car like that because hers has a smart alternator. The DC to DC charger is attached to the portable battery box. If I didn't add a VSR to my car the charger would be draining my main battery too much. For hers to work she needed a VSR anyway. It was that or adding a switch to the portable battery box to turn on/off the blue ignition wire of the charger. But there would have been the problem of forgetting to do it and either arriving to a destination in her car with a not fully charged battery box, or flattening my battery overnight because of the low DC DC charger voltage cut off.
Foretold is forewarned, thanks Andrew I would have killed my battery as well eventually and been scratching my head wondering why. And no doubt it would have been as the most inconvenient time imaginable. 👍
Connect the trigger wire through a relay. Pin 30 to key on power, 86 to key on power, pin 87a to dcdc trigger wire and 85 to alternator thin wire which grounds the battery warning on dash, so when alternator is working the DC DC will sense and turn on the charging.
Overland Drive I use the same dual charger system for aux and main battery, just leave a shore line plugged in and both batteries are charged and maintained, easy. Worth buying a decent dual charger
So in short, connecting an external charger to the main batt. is the same as turning the ignition switch to on. The DC-DC charger could not tell the difference.
Andrew, you've just proven (thank you) that a DC-DC-charger is a redundant piece of "bling". All one needs instead of a DC-DC-charger is simply a $30 BIG FAT DIODE . OK, assuming you're also charging from the Solar-Panels, then you need a regulator for them, but a decent Solar charge regulator will do that cheaper than the DC-DC bling. Reason I say this is that the vehicles Alternator is a regulated charger of ample output. Now, you *could* in theory just join the 2nd battery in parallel with the car battery, and they will both charge just fine . -But we both know why we do NOT do that! - because they will both go flat together, too. And THIS is what the $30 diode is for - it allows the charge to flow only in the direction of the 2nd battery and not out into the car battery. Your Alternator has plenty capacity to charge both batteries simultaneously. the DC-DC inbetween is only duplicating what the alternator itself does. Moreover, its just wasting energy in the process. Just replace it with a diode, (and a $1 fuse if you want to go "pro version" ) and you're set (so long as you have a little regulator between your Solars and the 2nd battery). I'm all for keeping things simple in the bush. I don't need to explain why. Thanks for a great channel.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
Good point. I am about to install a redarc DC/DC into my jeep with an AGM and LiFePO4 auxillary battery and I have been looking for a AC battery charger to do what you are doing.
Have a look at the company Traxide. There's works better than DC-DC chargers. Been around for 20yrs plus. Kept my dual battery variable voltage alternator 4wd charged for 7 yrs so far :)
So you are saying, when the engine is on, if the difference between the alternator output amps and draw from the main battery for various components are less than 50amps, still the main battery will discharge?
Good point, and correct. That’s why you need to match/balance all electrical equipment in your circuits. He said his alternator puts out 170A, so if all vehicle systems are using up to 120A maximum, then I guess he’s OK under alternator power. However, it sounds like it might be a contributing factor to his starter battery being drained. When he said he had a 50A dc-dc charger, I immediately thought that was overkill, unless his alternator can indeed keep up with total demands, and unless he has a bank of auxiliary batteries in the 200AH plus range. Very good point buddy.
Was kind-of aware of this but good to be told, probably could make a safety circuit for this but a Big Label on the charger will be the cheapest solution.
Interesting stuff, I shall check for this problem shortly! I noticed that your new vehicle has a cyclonic snorkel head/pre filter. What do you think of them? Will you be changing it? I'm considering switching from an air ram to a cyclonic head.
Maybe Im just thick headed, but I just installed a Renogy DC to DC charger and second battery. The charger only turns on when it sees more than 13.2v for 30 seconds. I dont know about you, but my 2001 Land Rover Discovery does not put out 13.2v with just the ignition in the "on" position. Only when the vehicle is actually running will it put out more than 13.8volts and after 30 seconds of seeing that voltage the DC charger will turn on. If the starter battery goes down to below 12.7 the unit shuts off. The Renogy unit also has solar inputs and unlike the Redarc. Once the aux battery is full. The unit uses the solar to trickle charge the starting battery!
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
I have exactly the same setup in my 4WD (third Redarc BCDC setup Ive had installed across 3 separate vehicles). The simple solution to counteract the problem you’ve described is to wire up the blue wire to ignition. Understand that if you leave the ignition on the Redarc BCDC device is then activated, however, how often will you leave your vehicle in ignition? Across the 3 4WDs I’ve owned I’ve never seen a need to leave in ignition.
Yep, blue wire goes to ignition so battery charges from alternator when ignition is on and solar/external chargers when ignition is off. If you leave the ignition on by accident, the start battery will only drain until it reaches the cutoff voltage and then switch itself off as per usual. The only time you will run into trouble this way, is if you have an external charger/solar AND leave the ignition on
Nice work Andrew, If I may my 2cts: trouble starts when manufactors paralel batteries; the solution is use more powerfull ( more current) chargers, actually like they do sizing the alternator; of course the batteries last less. ( it happened in the past with 6v and the trucks 12v) best, Pedro
I installed a switchable circuit breaker between the main battery and the DC to DC charger to separate the two Systems if I needed to. I did however learn the hard way about what you are talking about because I forgot to turn the switch off
I use the trigger cable on my Redarc even though I don't have a "smart" alternator and I have never had any problems. I occasionally leave the car on accessories to run the radio but this is fine as the ignition connection isn't triggered. It seems unlikely that anyone would leave the ignition on when the aux batteries are low as normally they would have solar connected or run the engine to charge them in that situation. If you leave the ignition on after driving for a while and then load up the aux battery then that would cause a problem but it also seems pretty unlikely. I have run my system for 2 years with no issues.
Hi Andrew, in your opinion, how can we avoid drain out the starter battery ? By not connecting the ACC wire(if not smart alternator)? or simply add a switch by the starter battery and switch it off if turn on ACC (engine offf)? So, if someone never leave the ACC 'on' whatever condition it is, the starter battery won't be fltten, it this correct? By different manufacturers, is your findings applies to all of them? (Renogy, Atempower, Redarc, Hisae, Projecta....)? What if there is a solar panel connected with 5-10A current presented? thanks !!
What if you put a switch in the cabin to control when the charger is allowed to operate, normally it would be in the ON position so it can operate as per normal, but if you want to do work on the car with ignition on, for a period of time the switch will disable the charger, maybe a red flashing light also when it's "off" to warn you so you don't get to the destination and it's wasn't charging because you forgot to turn it back on ?
When Redarc fuse circuit was closed, the voltage drop at the main battery went to 12.7v (as 50amp would no doubt collapse the main battery voltage, thus disengaging Redarc), then presumably the external charger (10amp) was able to bring main battery up to 13.2v in a short period (thus Reengaging the Redarc). Conclusion being that multiple cycling of the Redarc engaging and disengaging slowly depleted the charge state of the main battery. However, if you waited sufficiently long enough and just left the AC charger going, this whole process would have been unknown to you. But it is actually happening, probably to a lot people who have this setup. One possible solution, a single rectifier/isolator between Alternator and you battery system and then wire your Redarc to the Alternator positive. Result, Redarc will never switch on unless alternator is producing power.
I was looking at the Redarc wiring guide that indicates a resettable fuse should be used in the setup. Therefore to charge each of the batteries wouldn't you just break the fuse during the charging cycle and therefore only charge the one you want?
Loved the way you explained this. Just a thought, doesn't this come down to the rule of using a battery charger that is of equal or higher current rating than that of the largest charger device in the vehicle circuit active at that time of charging?
4 года назад
I'm just curious. Since You have lithium battery at back, it would charge fast during drive. Is home charging for battery maintenance purposes only? Right now im buying DC/DC charger and after your video i think about redesign my wiring and leaving inside cyrix ct. As always, thanks for great video.
@4xoverland My solar panels are currently removed for vehicle maintenance so I have been charging exactly how you do (did). I have been monitoring voltage and current with the following observations. When the supply (crank) battery is at 14v with engine running the DC/DC charges at full current. With only a mains charger connected to the supply battery it's voltage drops and the DC/DC tapers off the current delivered to the lithium. (while still in bulk stage) It finds equilibrium at 7 amps and happily charges everything to float. This happens to be the exact amount of current my Ctek 7.0 is delivering to the supply battery. My DC/DC is not redarc. I would suggest either a setup error, a firmware problem or a bad design DC/DC charger.
For some reason I tend to believe that Redarc know more about this stuff than you so I’ll just keep mine as it is thank you, wired as per instructions from the factory. Haven’t had a problem yet
On an isolator setup redarc sbi12, charging both a start and dual purpose marine stoaway at the same time off a battery maintainer at 2amps. I have been separating them when stored in the shed would that be harmful with both on the one. Got a better 5amp victron one that would be easier to just plug into and do both. I know the isolator isn't as efficient but for a basic under bonnet setup that I wanted to be able to jump start myself it works good enough. Also add those large fuses are not the greatest usually the holders cannot stand up to the current, midi are far better and easier to store as spares
Awesome video, I get it. I am also having another weird problem. After using the fridge for the day and I get back in and drive, my dash lights start coming on. I am sure this is the computer shutting things down for lack of power. Sometimes it is when I underrate. When the second battery if full there is never any problems. I have 120 series Prado 3lt desire. I have wonded about the Alternator but am now wondering about the dcdc charger. Any thoughts?
Just installed one of the BCDC 40 amp redarc's can someone tell me how hot they normally get. During bulk charging mine gets Hot! All else seems well, charging normally etc... Thank you
Sounds like these expensive systems have plenty of traps if not set up or used right. For now, I just have a really cheap set up of the main battery for all the original vehicle systems (1970s Land Rover, so very basic), and a second battery for accessories like power sockets, stereo, auxiliary lights, seat and screen heating and so on, any thing not essential to driving. They’re linked by a heavy relay which it triggered by the alternator diode pack (dash warning light terminal on the back of the alternator). It works very simply, so the batteries are isolated unless the alternator is providing a charge. I want to add solar for the auxiliary battery. The primary shouldn’t need it - main systems are drawing power if the vehicle isn’t being used, and in such an unlikely event, the engine could be started by jumping (a hard wired isolator connecting only for emergencies) from the auxiliary battery. There is a lot to be said for simplicity.
Hence why I run a manual reset circuit breaker to my DCDC to stop it running while maintenance charger is on starter battery. There is always pros and cons even with circuit breakers and probably best to use a manual reset breaker in a dcdc charger case as an auto reset could keep toggling all day long if there’s a fault until it either burns it self out or something else happens. Another issue with circuit breakers and especially on a hot day under a the hot bonnet with high current is they can trip based on too much heat even if there is no over current or fault situation. Probably the most reliable type of system would be the midi fuse but then can’t break the circuit without maybe also installing a switch.
I have a TS800 DC/DC converter which has a vibrationsensor to check if engine is running, works fine, also when ac charger is hooked up. Except on a long trip on a ferry where it completely drained the starter battery 🤔
You need a battery isolator between the two batteries so that when the main engine starting battery gets to fully charged then the rear battery is connected in parallel as one battery . Then the charger or the alternator only has to charge around half the potential amp hour capacity at a time . As soon as the isolator detects current draw and voltage drop on the main battery it shuts down and isolates the rear battery . Most have a jump start button that allows you to jump start from the rear battery if the main battery is dead . It also allows you to drain the rear battery running something but not drain the main starting battery . In any dual battery system it's better if both batteries are the same type and also very close in their amp hour capacity . I am not a fan of DC to DC chargers but if you use different chemistry batteries then they are needed . I could be wrong but I think they can overwork the alternator . Also not a fan of lithium batteries especially inside the cab . Just do a search for lithium battery fires in cars . AGM battery much safer and hold their charge well also cheaper but heavier .
Yeah that is interesting, so the AC charger is keeping the voltage up which the redarc thinks means the alternator is on and thus switches on the DC to DC system. And then the DC to DC charger does its thing and demands lots of amps to charge second battery and that then drops the starter. So that blue cable is for sure one answer, you could put a relay against the car being in gear and ignition on if you wanted. OR you could put an isolator between the alternator (with correct current rating) and the starter battery, and sense the DC-DC charger from the alternator side, you could then charge the starter and the DC-DC wouldnt know about it, and when the alternator spins the isolator would energise and charging will work like normal, You could still join the batteries together if you needed(because you will energise the isolator),and could sense both (If the redarc actually cares). Just my quick thoughts.
If the trigger wire was hooked up to ignition on Source you would not have this problem Or just charge your auxiliary battery and let it trickle charge back to the starting once it stopped off
Hi Andrew sorry if you've already mentioned this but i don't remember, are you going to fit one of those sealed water cooled alternators to the new truck to illuminate to dust, dirt and water crossing problems and make it more reliable, I imagine there very expensive but it also maybe peaces of mind too mate. Seeya Rob
Andrew, have you explored the capabilities of combination of CTEK SMARTPASS 120S & CTEK D250 (total of 140 amps) batteries management system? You may want to consider reviewing some of the Swedish CTEK products. It might be useful in the situation with two power sources, e.g. vehicle alternator and solar panels.
I believe you will agree that it is not a good practice to connect multiple charging sources directly to either the Primary battery or Secondary battery. Multiple batteries and multiple charging sources must be managed in desirable manner using a controller or management system
I know the CTek systems very well. Used them for years. This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
4xoverland Then edit your video accordingly. As it is, it sounds like you’re blaming the equipment, when all the equipment was doing exactly as it was designed to do.
I would have been interested in what the voltage was doing, it must of been bouncing up and down as the charger started up and the power supply fails and restarts.
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I'm a firm believer to always isolate a battery when using a 220V AC charger, regardless whether using 1 or multiple battery systems. It simply eliminates any possible issues from occurring. Thanks for the heads up Andrew! :)
This is so critical: as is clearly shown by Andrew's example. It's also the safest approach. I'm also a bit surprised at the notion of using solar to charge the crank battery. I'm more used to using solar and DC/DC chargers to charge the house batteries and isolating the crank battery so there are no loads on the crank battery other than originally intended by the manufacturer. The alternator should always be sufficient to charge the crank battery. Some alternators supply a varying amount of current, depending on their temperature.
Same here. If I am going to charge my starter battery with AC charger or solar panel, I always disconnect the wires from the negative terminal of the starter battery first.
All good info Andrew, I have had many problems to solve with battery issues as well. But I must say that it has been about 50 years since I left an ignition turned on with the motor off. I always use the trigger wire and a solenoid to connect the BC-BC. Cheers! Good Stuff!
In my setup I have a breaker where your fuse is and I can quickly switch off the Aux circuit when I need to charge the main battery and often leave it off where not on trips just using the roof solar to keep the Aux topped up.
How is the apparent charging voltage being maintained? As soon as the 50amp charger turns on it should pull the voltage down to just the battery voltage plus a little for the amount of power the charger can put in.
Unless the DC to DC charger is set to run down to 13.2V or something that shouldn’t let the starter battery discharge to below where it can crank over your cruiser.
If it is set to a very low cut off Voltage there should be a way of turning that up, with your setup the charging voltage shouldn’t fall below about 14v.
Try measuring the voltage at the starter battery with theAC to DC and the DC to DC chargers running
Mine does just the same as Andrew says
David Cocks yep I saw a bunch of comments saying they were doing the same thing and I definitely believe it but I don’t see why you would want it to keep charging down to less than 13.5v probably higher if you have a powerful alternator the little 70w one in my ute easily holds 13.5v at 50A draw (I checked) and that is where I set my minimum. I only have a 5A charger and a 50A charger for AC the 5A only adds about 0.25V if the DC to DC is working flat out. But I can see a 10A one allowing the battery to go down below 12V with a 50A DC to DC one running if the DC to DC goes down to a really low voltage before shutting off.
(my DC to DC is a dodgy Chinese one with a potentiometer each for the charging voltage cut offs (start-stop, drop, fast charge, slow charge) and dip switches to select other stuff and it says it will do 45A but it only does about 30 on any battery setup I have tried it on.
The battery charger is sending 14v 10 amp into the battery
The 14v triggers the dc/dc the drain
The dc/dc is only looking for 13v so.even thoigh the main battery is dead flat the charger is providing that voltage signal
It could maybe be set to trigger a fault because of low amperage input but currently they're only set to look for that voltage signal
Glen Collins, I do agree with you. It is impossible, voltage must drop the moment the load exceed the maximum Amp the AC charger can supply. But the question remains, how does the crank battery then discharge? It just does not make sense?
CampX4 & Outdoor TV it’s being pulled out of the battery by the red arc DCDC and milking it flat as the 10 amp ac charger is trying keep up with THE 50amp load pulling through to the auxiliary, whilst this is going on the ac charger constantly sees a huge hole, tries in vain to fill it and cranks max voltage and amps into the bottomless pit.
I have the solution for you Andrew.
I tow a camper trailer and in it I have a redarc BCDC40 to charge the two 100 Ahr AGM deep cycle batteries simply because of the distance from the car alternator and the resulting voltage drop. The problem is exactly the same, if the batteries in the camper were not fully charged when you stopped the DC to DC would drain the auxiliary battery to charge them.
To overcome this I have a 100 amp relay mounted in the back of the car prior to the anderson plug which is switched through an oil pressure switch so it will never charge from the cars auxiliary battery, in my case, unless the car is running, even if you leave the ignition on accidentally. Luckily I found this out when researching the wiring and installation of the dc to dc charger before the actual fitting and it works perfectly. You could do a similar thing in your vehicle.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
@@4xoverland I charge the aux batteries first. I have 360ah batteries charged via solar /Redarc BCDC1240. I also have a built in 30amp Victron mains charger, connected to the Aux batteries. If I ever need to charge the crank battery (which is rare) I have an alternator friendly switch to parallel the aux & crank batteries via 70mm2 cable (for extended electric winch use) , but it also doubles as a means of charging the crank battery when switched to parallel.
This is what the green lite on the charger is.
Visual indication that the charger is active.
Mount the unit appropriately.
Andrew, this doesn't make sense. I have basically the same setup and haven't experienced this problem.
Typically DC/DC Chargers will switch off and stop charging the aux battery when the input drops below 11.8 volts. They typically won't turn on unless the input voltage is above 13.1 volts. So when you connected your mains charger to the battery, yes the voltage would have risen above 13.1 volts and the DC/DC charger would have turned on. This is the same principle and operation of the old Voltage Sensing Relays (VSRs).
However, it's understandable that your mains charger would not have been able to cope with the load (current draw) of both batteries (if both were discharged).
But what should have happened, is that the voltage from your mains charger would have progressively dropped as it wouldn't have been able to maintain the output current required to charge both batteries. Once the mains battery (with mains charger connected) dropped below 11.8 volts, the DC/DC charger should have turned off.
The mains charger would then have been able to again start charging the main battery and the internal resistance of the battery would start rising and so would its voltage (Ohms Law). Once it reached 13.1 volts, the DC/DC charger would kick in again, and the whole sequence would start again. The end result over time, should have been that both batteries would be fully charged.
So what's happened in your situation is a bit of a mystery.
The charger would have been connected to the same terminal as the DC-DC, so the DC-DC would've been seeing the input voltage of the charger this draining the battery. The charger would've been giving the DC-DC a false voltage reading of the main battery. The only way to get around this is to disconnect the DC-DC
Kim Flesser 240v charger pumps out a constant 13+ volts across the terminal therefore dcdc keeps charging..
@@nickscurr7062 My understanding is that external charger was connected in parallel to both the main battery and the DC/DC charger. So I still ask the question, why didn't the DC/DC charger turn off when the main battery and external charger voltage dropped to 11.8 volts. The external charger and main battery cannot have different voltages when connected together. Is there something here I don't understand? (I used to be an electrician...but not a very good one...LOL!).
@@FastFless I'm afraid there is some "misunderstanding" between the DC/DC and the small charger (like pulse charging in the small charger that causes the voltage to raise repeatedly above the DC/DC switchoff levels). It is actually very unfortunate that both the devices are from Redarc and they don't work together!
@@FastFless , if the 10 amp charger was a simple linear constant current 10 amp device, then I believe it should be just as you have described. There must be something funny about the way the charger is delivering the charge that is tricking the DC/DC charger into staying on. It would be interesting to connect an oscilloscope and see exactly what is going on.
Not an issue with CTEK 250sa with smartpass check it out ! Have had ctek on my cars now for 7 years and never flat batteries, and my car is not a daily driver either.
That solution will also charge the start battery by solar when aux battery is full.
CTEK also recommend attaching the float charger to the Aux battery side. The same can happen with CTEK if your float charger is able to lift the main battery voltage.
Ģg^g^gg^^v
Thank you Andrew I have just discovered your channel. This should end a long running debate among my friends. I had warned one of my friends that sitting on the beach listening to the test cricket will flatten your battery. It had happened to me. I suspected the trigger wire as you explain but he was adamant that the load from the radio could not possibly drain his starter. Sure enough I had to give him a jump start but he still didn't believe it was the radio at fault. Now we know it was probably a flat auxiliary combined with the the trigger wire connecting the two batteries.
Love what you are doing with this series Andrew! Could you do a video on what compulsory maintenance we should be doing before trips? I am not very Mechanical savvy and would love a guide. Thanks.
Thanks for the info. In my situation I have my start battery purely for starting only. (Nothing connected besides low amp accessories on switches) the start battery will also be monitored. Then from my starter battery, it then connects to a smart isolator before connecting to my secondary battery. The second battery then has all the niknaks. This works only for older cars.
Many thanks for the heads up on this. Just a couple of weeks into a van to camper conversion. I will add in an isolator in the circuit just to be sure. I was always taught never to leave the ignition on, that stems back to old petrol cars where depending where the points were your coil could burn out. We used to pull the coil wire off if we had to tow a dead car for the same reason.
I run the trigger wire through a switch and to 12v+ that way I control when the DC-DC is on.
Hi i do similar ,plug into cig plug and works fine, cheers terry.
What happens when you use solar and the car is off
@@Nathansillav My solar batteries are separate from the vehicle, so it functions the same if the car is on or off.
I also have a Ctek 250sa DC to DC charger hooked up to a solar panel (because it's not a daily drive) it charges the 2nd battery and when that's charged it starts charging the start battery.
Exactly. Take any overflow from auxiliary battery bank back to the starter battery. I’m looking at a dual-sensing VSR for this purpose. The Jaycar one has cut-in at 13.3V and cut-out at 12.8V.
Great video, Andrew and some excellent tips for us all. I'm using a manual cutoff switch in the dash for the DC-DC charger so that I can override the charger even when igintion is on.
I was installing a BCDC 1225 this weekend, and found your clip pretty interesting. My install was in a camper, and it got me thinking… This issue looks like the starter battery needs to be better isolated from the house battery, and possibly it makes sense to treat it like a camper install and use a solenoid or an SBI to only link them when the ignition is on?
U should have ur BCDC charger on the trigger switch u mentioned. The trigger switch can also be connected to a wire that only receives voltage when the car is running. U could also add a breaker so as the BCDC charger doesn’t see the voltage when ur trying to charge ur main......
I love DC-DC chargers, but thought it to be common sense to isolate the primary and aux batteries before connecting a 220V charger anywhere in the system, even if charging the aux battery/s and the DC-DC charger won't let current through to the primary.
I always run a 12V 60A circuit breaker between the two battery systems, this way you can even use two 220V chargers at the same time to maintain both sets of batteries whilst the vehicle is not in use for some time.
Agree Dirk, Isolation prevents any 'oops moments' , simple and effective. :)
Agreed. Circuit breaker to isolate. Simple and effective.
Andrew, possible solution, mount a solar panel on your garage roof and run cables down for easy connect on to the yellow cable (solar input) on the Redarc. When the Redarc sense solar input, it will not accept input from the main battery. Therefore, as long as you only have your 10amp start battery charger on at the same time as the solar connected to the aux, then you will effectively have separated charging of batteries.
Regards, Sean
Another, solution, in the red line between the start battery and the Redarc, add an old style silver 100 amp continuous duty solenoid (the type we all used to used in simple dual battery set ups years ago) then trigger this from the windscreen wiper motor. Then, the start battery can only feed the Redarc when the engine is running.
i have no problems,my dc todc charger wont draw onece it reaches 10.5 volts,plus i use a dedicated deep cycle battery charger,it will charge two 120 amp hour batters plus the start battry,correct your set up.you may need a voltage sensative relay.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
NOTE. I chatted to the guys at Redarc and with Heiner. There is no mystery why this happened. It happened exactly why I said it did. It's a perfectly logical explanation. This is not a Redarc issue. I'm just using Redarc DC-chargers in my setup. All DC-DC chargers will do this because they rely on reading the voltage across the main battery to turn on. And if you use a trigger cable from the ignition, the start battery can be discharged if the ignition is left on, with the same result. The solution is very simple: if you have a DC-DC charger, if you want to charge the batteries without the engine running, charge the auxiliary battery first. What could be simpler?
Just follow the wiring diagram like everyone else and use the ignition trigger wire to turn the system on. If the ignition is turned off, no problem. Not sure why anyone would leave the key turned to ignition if the car isn't running.
So the solution - if you need to charge the start battery is to disconnect "aux" battery - before or after the BCDC - before charging the start battery (a good use case for a simple disconnect). (my BCDC Redarc 1225D is on Anderson connectors.)
(NB - Redarc calls their system "Battery Charger Direct Current - BCDC, others call their units "Direct Current to Direct Current" Charger - DC-DC)
Blue Trigger cable is specifically for low voltage / smart alternators.
4xoverland would a circuit breaker with switch work? Install near the mains battery and when you put on the charger flip the switch on /off
I don't know if in any car. But in my VW T5 there is a D+ wire, which is a "alternator running" signal. From the factory the second battery charges only when the alternator is running. So not on ingnition. I thought there is a signal cable like this in any car.
@@kadmow seems like redarc are handicapping themselves for no apparent reason
Fascinating! Thanks for sharing your knowledge. This situation is certainly not one that people would immediately expect to occur. I’m about to design and roll out a system into a 4WD van and I will certainly put an isolation switch between the crank battery and my custom goodies - even just if starting with jumper leads etc I don’t want the aux system taking some of that load away.
Oh - before I forget, and hopefully this helps someone - I reckon if you want to hook up that ACC wire to trigger the DCDC, hook it up to Ignition / ON position instead. That way if you’re sitting in the car in ACC mode listening to the radio, your crank battery isn’t being drained to charge the aux battery.
Well spotted Andrew.
This is a big problem with DC-DC chargers. The charger will continue to run when the car is switched off as the cut off input voltage is 12.4v. Once the input drops below 12.4v the charger will stop until it reaches 13.4, however this often means your primary/starter battery is sitting around %70 SoC which is not a good place to be when it comes to starting big engines.
For example: You have a 110A alternator, 100A isolated aux battery, a BCDC1240 charger, and a fridge. You pack the fridge a few days before going away and its on full time to get to temperature. The only driving you're doing is to the shops and back, perhaps an hour a day. If it's just bussing around locally, your alternator never gets consistent high RPM so its average output is around 30-50A (most are
I honestly thought everyone knew this....The clue is in the ‘voltage sensing’ aspect of the DC-DC. Also, DC-DC does not charge at 50 amps. That is simply the maximum it can charge at. The charge delivered depends on the aux battery’s state of discharge.
I typically see 5ish amps from my alternator? Would you say thats pretty low? I do have issues with power as dashboard and electrics turn off 10mins into night driving and come back on with battery light
Yeah, if only charging at 5 A most of the time you seem to have an alternator or bad starting battery issue.
great info, Thank you! I am in the process of switching over my dual battery system due to the Tacoma smart alternator. This time I will place my second battery in the bed with a DC/DC charger............
Hi Andrew. I'd suggest re- approaching Redarc with regards to apsolute clarification as to this blue wire and voltage cut off. Someone has to be wrong, otherwise state of the art Redarc starts to look like well outdated Redarc (and any other dcdc charger that works in a similar way). I truly believe it's not Redarc as instructions despite not being so clear, suggest it's all down to this blue wire not being connected. Now a great video would be to connect the blue wire and do the same test, then try with the ignition left on to test voltage cut out, or as the case may be no voltage cut out with a mains charger connected.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
@@4xoverland Yes true, it is a simple solution. However I'm more thinking along the lines of alternator output - I'm running a smart alternator as fitted by Mr Toyota, if I remember correctly you have changed yours or was that just the Africa terrain tamer build? So a smart alternator can drop output to something like 8 or 9 volts, is there a scinario where by your starter battery can be fully charged in the eyes of the smart alternator however your aux batteries are near depleted and the dcdc charger pulls your starter battery down to a point where by it can no longer start your engine despite the alternator still effectively charging? My theory is the smart alternator should be smart enough to figure this out and fast enough/be able to provide enough amps to starter battery to cope.
Scinario 2 - your alternator becomes defective and cannot provide enough amps to keep your starter battery topped up, the dcdc charger will happily help kill the starter battery much quicker, this drops to a point where your vehicle electrics cannot run and your lose engine and all "factory" vehicle power. (It would happen anyway but the dcdc has made it happen much quicker. O.k. alternator failure isn't that common without warning and if it did happen your red dash charge light comes on so you can pull the dcdc fuse and potentially divert solar power to give the starter battery some form of charge - that would be pretty pointless in the U.K though, with our weather!
Perhaps I'm overthinking the perfect storm combination? I think I'm into my 6th or 7th year of unbroken patreon support for you Andrew. Keep doing what you are doing, we all get a great amount from your videos. I truly like the fact you are unbiased and not worried about saying the truth.
Do you have any future trips planned with Mr Paul Marsh? Stay safe and let's ride this storm out one way or another...
Andrew, I realise you've identified the issue, but here's a suggestion for the future. I've fitted an Enerdrive 240v charger in the canopy of my Silverado. It has 3 separate "channels" for charging 3 separate banks of batteries. I have a somewhat similar set-up to you... A Redarc BCDC1225L and solar panels on the roof of the camper.
When I plug the 240 volt cable into the caravan-style receptacle, the Enerdrive charges the Lithium battery, which is set to Channel One (in the canopy) first. It has the ability to choose what type of battery is being charged.
Once the lithium battery is charged, it then turns its attention the Channel Two, which is the twin under-bonnet starting batteries. To achieve this latter function, I've simply tapped the Channel Two supply line into the cable that supplies the BCDC with its power from the front batteries.
In your case, if you go ahead with another lithium battery (inside the canopy of your truck), then you can utilise all three separate channel of the Enerdrive.
If you're interested in my Chevy, here's a write-up that was done a year or so ago: loaded4x4.com.au/issue-002#61
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
Good to know. I knew there was a reason why I hooked up the optional manual disconnect switch. Thanks!
In my case I’m charging a travel trailer with the tow vehicle - so the protocol needs to be always unplug the umbilicals when not needed.
VIDEO RESPONSE to Andrew: please search for "Dual battery charging issues VR: 4XO DC-DC CHARGER WARNING. Avoid a runaway discharge." on youtube.
Shows what some DC-DC chargers do when configured in similar circumstances.
Im not sure how you have done that .. but that is a setup issue .. its not a problem with DC to DC chargers buddies .. laughs .. oh dear
Key Maker quite agreed. Setup issue. But can be solved if one wants. For me no.
@@gotoylc This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
@@gotoylc if you understand how electricity works, you'll find that he is correct. It's not a setup issue
@@blastar55m3 This is a very obvious setup issue. There’s a relatively simple device to install to prevent, 100%, this particular issue from ever happening.
Unfortunately I do not know Andrews full setup, so perhaps the setup is not correct correct, or there’s an item overlooked and not installed. Andrews setup diagram would be useful on this issue.
Thanks Andrew, I was wondering what my problem was as the Main battery was often low on voltage. After watching your vid I went and checked my set up and it was so. I am now going to instal a relay controlled by ingnition to circumvent this.
No need to do that just put your battery charger On your house battery Once it Topped off it'll backfeed to your starting battery And charge it
It may be worth noting that every time you charge this way you are depleting the crank battery far too much even if you leave it on for the full cycle. It's being drained way down then recharged slowly, bad practice. Better to charge house batteries separately.
Yes, that's a better procedure / good practice.
J M or get a DC to DC with a more appropriate cutoff voltage if you can’t change it in the settings.
If you pull 50amps from you starter battery, the voltage on the starter battery will quickly drop below 12.8V (or whatever) and your DCDC charger should sense that and switch off. Charger is puttting 10amps across, pull out 50amps - voltage will drop quickly. Mine does (Projecta DCDC). Why doesn't yours?
I think in this case the Battery charger was keeping the Main battery at a high enough voltage for the BCDC to keep pulling current out - it probably cycled several times sucking all the input "juice" out of the main battery. - could be wrong. (leaving it "nearly flat" over the charging time)
Use a smart amp solenoid simple men
@@brianostwald802 Dead right Brian, I use the simple old smart voltage solenoid No Worries, why complicate a simple need with an expensive
& complicated piece of Bling Mate.
Jason Shepherd
The voltage at the battery needs to lower than 12.7 for 10 seconds before the dcdc will shut off as it has a delay built in. Even if the ac charger dipped in voltage under load it would sense it and crank up voltage to compensate within that time window of 10 seconds and kick it up over 12.7 + , therefore dcdc charger keeps on pulling the load.
@@aussiedrifter he needs the DC DC because he's running a lithium battery. The alternator with a VSR would cook the lithium battery BMS or the cells quickly plus the battery may even burn the alternator.
Another good video thanks Andrew. What I did was to install an old school 2nd battery solenoid, the old silver can type which only activates when the ignition is on. And yes you do have to charge the deep cycle separately if it is low. Cheers.
blue wire has to go to ignition so the battery charges from alternator when ignition is on and solar/external chargers when ignition is off. If you leave the ignition on by accident, the start battery will only drain until it reaches the cutoff voltage and then switch itself off as per usual. The only time you will run into trouble this way, is if you have an external charger/solar AND leave the ignition on. Maybe look at the official redarc wiring diagrams or speak to them before you start blaming the charger for your own mistakes
Dion. I know you want to have a go at me here, but you are making several incorrect assumptions. The first one is that I didn't check with Redarc. I did. And they confirmed my assumptions face to face. The others is that you are incorrect with regard to how DC-chargers work. The point is simply, if a charger is attached, the cut-off voltage is not reached until the battery is almost fully discharged. May be check things before you start blaming me for your inability to accept that you don't know everything.
@@4xoverland My bad mate, just read through the manual and I thought the blue wire was a trigger in the sense that it would turn the unit on and off (same as the blue override wire in the sbi12). It actually just adjusts the voltage at which the unit will turn on and off. I just couldn't get my head around the fact that a simple on/off trigger isn't a function of these fancy dc-dc chargers
@@Infuri96 No worries. Like everyone, I'm just trying to get my head around these things and share what I learn. Handling baseless accusations is the single most difficult part of sharing knowledge and experience on RUclips.
That‘s a very good one, have never thought about that. Thank you for sharing that one.
This is really a new problem when the auxiliary battery is Lithium. Previously the AGMs commonly used would rarely accept 50 amps charge, no matter what the rating of the DC-DC charger. The solution is simple - if you can afford Redarc 50A DC-DC charger (most of us can't, and are perfectly well served with a 20A unit) you can afford a 50A AC battery charger. End of issue. You can also wire up a dash switch into the IGN trigger wire so you can manually override on those occasions when you need to leave the IGN on for long periods.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
helpful, i have asked the victron guys if it would do this with the orion dc to dc charger
Glad you shared this. Thank you Andrew.
Will this happen with duel sensing dc to dc Chargers my solar input on the dc to dc will also charge the start battery no need to connect solar to the start battery
Thanks for the video Andrew, I remembered the tip a couple of weeks ago when I had to charge my start battery.
Makes perfect sense, thanks. Simply put, attaching the external battery charger brings the voltage of the main battery over the 'turn on' voltage for the BCDC. The BCDC will start pulling current from the main to charge the Aux. It does so at a rate higher than is being supplied to the main battery from the external charger. If I ever do need to charge my main from an external charger, I will pull the fuse from between the main battery and the BCDC. Probably a good idea if jumping from one battery to another. Cheers
Thanks for the video. I will now put an Anderson plug in my engine bay connecting from my main battery to my dc to dc charger so I can unplug it if I need to charge main battery.
One can also add a switch on the positive lead connecting the redarc to your start battery. Turn it on or off to disconect the redarc to the starter battery and charge it without.
Anyways, thanks for sharing the experience, dmuch preferablento learn it from you than in the trail.
Awesome detective work ASPW. How many people have been caught out by this in COVID. I now realise that is what has happened to me two weeks ago.
Andrew, I believe there may be 2 possible issues causing this problem you either have a faulty Redarc DC-DC charger or the DC-DC charger may have a design flaw.
When the DC-DC charger starts charging the Aux battery and it has a 50A capacity and the AC charger is only 10A this will cause voltage drop and the DC-DC charger will start draining you start battery as you have experienced, but what should immediately happen at this point (12.7V) is the DC-DC chargers low voltage cutout should trigger and stop charging the Aux battery until the starter battery voltage has recovered (13.2V) and then the cycle will continue. This would normally prevent the starter battery from being discharged which seems to not be occurring in your case.
The AC charger should not be tricking the DC-DC charger, once more current is being drawn then the AC charger can supply the voltage of the circuit must drop, its physics.
It seems the low voltage cutout on your DC-DC charger is not operating correctly.
This leads me to believe your DC-DC charger either has a fault or a design flaw.
I am happy to be proven wrong if this is not the case.
It would be interesting to take some multi-meter readings of the system when this is occurring and see what is actually happening.
All the best in solving this problem.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple. When I learn something, I like to share it.
@@4xoverland It's a problem, whether or not you think it is, and whether or not you're trying to solve it.
If your DC-DC charger has a correctly functioning low voltage cutoff (and I would not buy one which does not, if ever using a battery as input) then it will NEVER drain the battery it is drawing from.
You don't have a properly functioning low-voltage cutoff on your DC-DC charger, plain and simple. If that's what you intended when buying it, fine, it's performing exactly as you planned when it drains your battery, and there's no problem to solve. But why buy and set up a system to do that?
Trick it into turning on as often as you want with a feeble AC charger boosting the vehicle battery voltage for a second, it should still shut off when the 50A draw drops the vehicle battery voltage of a half-dead battery a second later.
Even then, you'd better hope that the DC-DC charger has some sort of timeout on restarting, or it might be hammering your battery a few times per second, for instance spending 0.1 seconds with your battery losing 40A, and 0.4 seconds gaining 10A. Over and over.
User-induced issue. There are many ways to do it correctly and one way to do it incorrectly (by triggering the dc-dc with a tiny mains charger on the starter side).
Either isolate when shore charging starter batt with a tiny mains charger or use a mains charger of the appropriate size. Or charge aux back from mains with a dc-dc that maintains starter batt.
Patient: it hurts when I do [this]!
Doctor: stop doing it and it won't hurt anymore.
So this occurs when the DC/DC charger senses the (higher) voltage but not low current output of a small charger, and then "decides" to charge the auxiliary battery, which is in a state of discharge? Interesting problem
Thank you Andrew, I always follow your channel with great interest and I particularly appreciate your willingness to share freely your knowledge and insights. I would be equally keen to hear expert opinion from Redarc on your observations. Presuming you have this would you share those with us too perhaps?
Carl Tunstall shame his information is often incorrect, omits important details or is a bias of his ignorance (take the ARB TPMS video for instance)
Here’s what Redarc said.... In regards to the connection of the blue trigger wire on BCDC, the following needs to apply:
1) If your vehicle has a standard alternator type (fixed voltage), the blue wire can be left disconnected
2) If your vehicle has a smart alternator type (temeprature compensating or variable voltage), the blue wire needs to be connected to an ignition source
3) If you are unsure of what alternator type you have, it is best to connect the blue wire to ignition
We have indeed seen the video mentioned and it does explain the connection of the blue wire, just not in great depth as to how it operates.
This is why i've always installed a DC-DC behind a separate VSR
Or relay that is operated by the ignition
When maintenance charging at home, i connect to the Aux Batt via an Anderson in the rear
That is exactly how I wired mine as well (relay operated by ignition in my case)
Great lesson for us all, thanks Andrew
Interesting.
I can see how attaching a trickle charger would provide a falsely high voltage reading and cause the DC/DC system to start charging the camper batteries but I'm surprised that it doesn't detect subsequent voltage drops and then shut down again.
I mean, your battery's sitting at, say, 12.7v, you connect the charger and the voltage will go up to, perhaps, 13.2v.
The DC/DC system detects that increase, realises the starter battery is being charged and starts charging the camper batteries.
Even with the charger connected, as the starter battery goes flat the detected voltage SHOULD drop from 13.2v to 13.1v and then to 13.0v and so on.
You'd think that the DC/DC system would be capable of realising it was sucking out more leccy than was being pumped into the starter battery and shut down.
Hope this isn't a sign of future electrical gremlins in your new truck.
I've heard some horror stories about Lithium batteries from people who're smart enough to know what they're doing.
What about attaching the blue trigger wire to the alternators output wire? Just a guess.
As an Electronic technician here is some good advice for you. Never , ever charge your battery in your vehicle with an ac wall charger while it is connected to your vehicles electronics. The reason is that if for what ever reason you would have a voltage increase from the mains power or thermal runaway then you would fry your vehicle electronics. Always remove the vehicle positive terminal from the battery. You can however jumpstart from another vehicle like you would be doing right now. DC to DC chargers is for DC to DC.... not AC to dc to dc.. If your vehicle battery only was flat then you will need approximately need 10 to 15 hours on 10 amps to charge the first battery. Adding more batteries does double and triple the charging time. For an example. Drawing 10 Amps for 2 hours from a 100 amp hour battery means that you have used about 20% capacity. Charging the same battery with 10 amps will not fully charge that battery within 2 hours because as the battery gets fuller, the amps drop to eventually you will only be charging at about 1 or 2 amps. The time taken to charge the battery will be at least 8 hours.
I am in the process of changing my VSR for a 20A DC-DC, I was planning on using a DPDT switch or relay so that by default the camping batteries, when above trigger voltage (ie being solar charged) will keep the start battery full. When the vehicle is started, the relay will be triggered (by ignition switch) and reconfigure the DCDC to charge the camping batteries effectively from the alternator.
Andrew keep the VSR and and the DC DC charger behind. It isn't costing you any extra.
Just apply the following wiring from redarc as if your DC DC charger was not in the same vehicle and that way you have a redundancy for cut off circuit.
www.redarc.com.au/wiring-diagrams/how-to-wire-bcdc-caravan-vehicle-variable-voltage-alternator
I wired the my wife and mine car like that because hers has a smart alternator. The DC to DC charger is attached to the portable battery box. If I didn't add a VSR to my car the charger would be draining my main battery too much. For hers to work she needed a VSR anyway.
It was that or adding a switch to the portable battery box to turn on/off the blue ignition wire of the charger. But there would have been the problem of forgetting to do it and either arriving to a destination in her car with a not fully charged battery box, or flattening my battery overnight because of the low DC DC charger voltage cut off.
Foretold is forewarned, thanks Andrew I would have killed my battery as well eventually and been scratching my head wondering why. And no doubt it would have been as the most inconvenient time imaginable. 👍
Connect the trigger wire through a relay. Pin 30 to key on power, 86 to key on power, pin 87a to dcdc trigger wire and 85 to alternator thin wire which grounds the battery warning on dash, so when alternator is working the DC DC will sense and turn on the charging.
I thought 85 was the ground side of the relay...
@@Michael_Mears Ah, yes.. I just noticed the mistake. Corrected it now.
Aah, good ol' relays ....I like this 👍🏿
I have a Victron DC- DC on my two auxiliary batteries,with a 10amp smart charger connected direct. No problem with batterys, alwayes fully charged.
Overland Drive I use the same dual charger system for aux and main battery, just leave a shore line plugged in and both batteries are charged and maintained, easy. Worth buying a decent dual charger
So in short, connecting an external charger to the main batt. is the same as turning the ignition switch to on. The DC-DC charger could not tell the difference.
Andrew, you've just proven (thank you) that a DC-DC-charger is a redundant piece of "bling". All one needs instead of a DC-DC-charger is simply a $30 BIG FAT DIODE . OK, assuming you're also charging from the Solar-Panels, then you need a regulator for them, but a decent Solar charge regulator will do that cheaper than the DC-DC bling. Reason I say this is that the vehicles Alternator is a regulated charger of ample output. Now, you *could* in theory just join the 2nd battery in parallel with the car battery, and they will both charge just fine . -But we both know why we do NOT do that! - because they will both go flat together, too. And THIS is what the $30 diode is for - it allows the charge to flow only in the direction of the 2nd battery and not out into the car battery. Your Alternator has plenty capacity to charge both batteries simultaneously. the DC-DC inbetween is only duplicating what the alternator itself does. Moreover, its just wasting energy in the process. Just replace it with a diode, (and a $1 fuse if you want to go "pro version" ) and you're set (so long as you have a little regulator between your Solars and the 2nd battery). I'm all for keeping things simple in the bush. I don't need to explain why. Thanks for a great channel.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
@@4xoverland Fair enough. Either, as you say, charge the Aux batts first ... or ... get out more often - The problem we ALL have :-P
Good point. I am about to install a redarc DC/DC into my jeep with an AGM and LiFePO4 auxillary battery and I have been looking for a AC battery charger to do what you are doing.
you could use ignition wire vs voltage sensing on the DCDC
This is why I haven’t changed from my ‘old version’ SBI and use a mppt solar charger as well.
Have a look at the company Traxide. There's works better than DC-DC chargers.
Been around for 20yrs plus.
Kept my dual battery variable voltage alternator 4wd charged for 7 yrs so far :)
Hi, do you have a website for them?
So you are saying, when the engine is on, if the difference between the alternator output amps and draw from the main battery for various components are less than 50amps, still the main battery will discharge?
Good point, and correct. That’s why you need to match/balance all electrical equipment in your circuits. He said his alternator puts out 170A, so if all vehicle systems are using up to 120A maximum, then I guess he’s OK under alternator power. However, it sounds like it might be a contributing factor to his starter battery being drained. When he said he had a 50A dc-dc charger, I immediately thought that was overkill, unless his alternator can indeed keep up with total demands, and unless he has a bank of auxiliary batteries in the 200AH plus range. Very good point buddy.
Was kind-of aware of this but good to be told, probably could make a safety circuit for this but a Big Label on the charger will be the cheapest solution.
Hey Andrew, have you considered an Auto Conversion on your 79 for this build? What are your thoughts on an Auto 79?
Wouldn’t trickle charging a lithium battery like that not do it any good? I thought that’s why you need a specific charge profile for lithium.
could you put a redarc VSR in between starter and auxillary, that way the starter battery won't give juice to the aux?
Interesting stuff, I shall check for this problem shortly! I noticed that your new vehicle has a cyclonic snorkel head/pre filter. What do you think of them? Will you be changing it? I'm considering switching from an air ram to a cyclonic head.
Crazy. The auto-sensing circuit worked against you. Very informative. Thanks for the lesson.
Maybe Im just thick headed, but I just installed a Renogy DC to DC charger and second battery. The charger only turns on when it sees more than 13.2v for 30 seconds. I dont know about you, but my 2001 Land Rover Discovery does not put out 13.2v with just the ignition in the "on" position. Only when the vehicle is actually running will it put out more than 13.8volts and after 30 seconds of seeing that voltage the DC charger will turn on. If the starter battery goes down to below 12.7 the unit shuts off. The Renogy unit also has solar inputs and unlike the Redarc. Once the aux battery is full. The unit uses the solar to trickle charge the starting battery!
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
So what you are saying is that the DC to DC charger is sensing the 10A battery charger and not switching off and therefore draining the crank battery?
I have exactly the same setup in my 4WD (third Redarc BCDC setup Ive had installed across 3 separate vehicles). The simple solution to counteract the problem you’ve described is to wire up the blue wire to ignition. Understand that if you leave the ignition on the Redarc BCDC device is then activated, however, how often will you leave your vehicle in ignition? Across the 3 4WDs I’ve owned I’ve never seen a need to leave in ignition.
That sounds exactly what I thought, i have the same setup with the blue wire connected to an ignition source. No problems.
Yep, blue wire goes to ignition so battery charges from alternator when ignition is on and solar/external chargers when ignition is off. If you leave the ignition on by accident, the start battery will only drain until it reaches the cutoff voltage and then switch itself off as per usual. The only time you will run into trouble this way, is if you have an external charger/solar AND leave the ignition on
Nice work Andrew, If I may my 2cts: trouble starts when manufactors paralel batteries; the solution is use more powerfull ( more current) chargers, actually like they do sizing the alternator; of course the batteries last less. ( it happened in the past with 6v and the trucks 12v)
best, Pedro
Has your powertech unit ever started constantly beeping at full charge?
I installed a switchable circuit breaker between the main battery and the DC to DC charger to separate the two Systems if I needed to.
I did however learn the hard way about what you are talking about because I forgot to turn the switch off
I have a smart DC to DC that only connects when main battery is over 13.4 volts and disconnects when it drops below that.
I use the trigger cable on my Redarc even though I don't have a "smart" alternator and I have never had any problems.
I occasionally leave the car on accessories to run the radio but this is fine as the ignition connection isn't triggered.
It seems unlikely that anyone would leave the ignition on when the aux batteries are low as normally they would have solar connected or run the engine to charge them in that situation.
If you leave the ignition on after driving for a while and then load up the aux battery then that would cause a problem but it also seems pretty unlikely.
I have run my system for 2 years with no issues.
Hi Andrew, in your opinion, how can we avoid drain out the starter battery ? By not connecting the ACC wire(if not smart alternator)? or simply add a switch by the starter battery and switch it off if turn on ACC (engine offf)? So, if someone never leave the ACC 'on' whatever condition it is, the starter battery won't be fltten, it this correct? By different manufacturers, is your findings applies to all of them? (Renogy, Atempower, Redarc, Hisae, Projecta....)? What if there is a solar panel connected with 5-10A current presented? thanks !!
It could not be simpler . . Charge the auxiliary battery directly, and not via the start battery. Problem solved. It's that simple!
What if you put a switch in the cabin to control when the charger is allowed to operate, normally it would be in the ON position so it can operate as per normal, but if you want to do work on the car with ignition on, for a period of time the switch will disable the charger, maybe a red flashing light also when it's "off" to warn you so you don't get to the destination and it's wasn't charging because you forgot to turn it back on ?
When Redarc fuse circuit was closed, the voltage drop at the main battery went to 12.7v (as 50amp would no doubt collapse the main battery voltage, thus disengaging Redarc), then presumably the external charger (10amp) was able to bring main battery up to 13.2v in a short period (thus Reengaging the Redarc). Conclusion being that multiple cycling of the Redarc engaging and disengaging slowly depleted the charge state of the main battery. However, if you waited sufficiently long enough and just left the AC charger going, this whole process would have been unknown to you. But it is actually happening, probably to a lot people who have this setup. One possible solution, a single rectifier/isolator between Alternator and you battery system and then wire your Redarc to the Alternator positive. Result, Redarc will never switch on unless alternator is producing power.
I was looking at the Redarc wiring guide that indicates a resettable fuse should be used in the setup. Therefore to charge each of the batteries wouldn't you just break the fuse during the charging cycle and therefore only charge the one you want?
Any thinking man would.
Loved the way you explained this. Just a thought, doesn't this come down to the rule of using a battery charger that is of equal or higher current rating than that of the largest charger device in the vehicle circuit active at that time of charging?
I'm just curious. Since You have lithium battery at back, it would charge fast during drive.
Is home charging for battery maintenance purposes only? Right now im buying DC/DC charger and after your video i think about redesign my wiring and leaving inside cyrix ct.
As always, thanks for great video.
@4xoverland My solar panels are currently removed for vehicle maintenance so I have been charging exactly how you do (did). I have been monitoring voltage and current with the following observations. When the supply (crank) battery is at 14v with engine running the DC/DC charges at full current. With only a mains charger connected to the supply battery it's voltage drops and the DC/DC tapers off the current delivered to the lithium. (while still in bulk stage) It finds equilibrium at 7 amps and happily charges everything to float. This happens to be the exact amount of current my Ctek 7.0 is delivering to the supply battery. My DC/DC is not redarc. I would suggest either a setup error, a firmware problem or a bad design DC/DC charger.
For some reason I tend to believe that Redarc know more about this stuff than you so I’ll just keep mine as it is thank you, wired as per instructions from the factory. Haven’t had a problem yet
hi andrew, mate where do you connect the negetive clip? battery of chassis???
Battery. Always the battery.
On an isolator setup redarc sbi12, charging both a start and dual purpose marine stoaway at the same time off a battery maintainer at 2amps. I have been separating them when stored in the shed would that be harmful with both on the one. Got a better 5amp victron one that would be easier to just plug into and do both. I know the isolator isn't as efficient but for a basic under bonnet setup that I wanted to be able to jump start myself it works good enough. Also add those large fuses are not the greatest usually the holders cannot stand up to the current, midi are far better and easier to store as spares
Awesome video, I get it. I am also having another weird problem. After using the fridge for the day and I get back in and drive, my dash lights start coming on. I am sure this is the computer shutting things down for lack of power. Sometimes it is when I underrate. When the second battery if full there is never any problems. I have 120 series Prado 3lt desire. I have wonded about the Alternator but am now wondering about the dcdc charger. Any thoughts?
Just installed one of the BCDC 40 amp redarc's can someone tell me how hot they normally get. During bulk charging mine gets Hot! All else seems well, charging normally etc... Thank you
Sounds like these expensive systems have plenty of traps if not set up or used right. For now, I just have a really cheap set up of the main battery for all the original vehicle systems (1970s Land Rover, so very basic), and a second battery for accessories like power sockets, stereo, auxiliary lights, seat and screen heating and so on, any thing not essential to driving. They’re linked by a heavy relay which it triggered by the alternator diode pack (dash warning light terminal on the back of the alternator). It works very simply, so the batteries are isolated unless the alternator is providing a charge. I want to add solar for the auxiliary battery. The primary shouldn’t need it - main systems are drawing power if the vehicle isn’t being used, and in such an unlikely event, the engine could be started by jumping (a hard wired isolator connecting only for emergencies) from the auxiliary battery. There is a lot to be said for simplicity.
Since you're trying to centralise weight between the axles have you considered moving the start battery closer to the firewall?
Hence why I run a manual reset circuit breaker to my DCDC to stop it running while maintenance charger is on starter battery. There is always pros and cons even with circuit breakers and probably best to use a manual reset breaker in a dcdc charger case as an auto reset could keep toggling all day long if there’s a fault until it either burns it self out or something else happens. Another issue with circuit breakers and especially on a hot day under a the hot bonnet with high current is they can trip based on too much heat even if there is no over current or fault situation. Probably the most reliable type of system would be the midi fuse but then can’t break the circuit without maybe also installing a switch.
I have a TS800 DC/DC converter which has a vibrationsensor to check if engine is running, works fine, also when ac charger is hooked up. Except on a long trip on a ferry where it completely drained the starter battery 🤔
You need a battery isolator between the two batteries so that when the main engine starting battery gets to fully charged then the rear battery is connected in parallel as one battery . Then the charger or the alternator only has to charge around half the potential amp hour capacity at a time . As soon as the isolator detects current draw and voltage drop on the main battery it shuts down and isolates the rear battery . Most have a jump start button that allows you to jump start from the rear battery if the main battery is dead . It also allows you to drain the rear battery running something but not drain the main starting battery .
In any dual battery system it's better if both batteries are the same type and also very close in their amp hour capacity . I am not a fan of DC to DC chargers but if you use different chemistry batteries then they are needed . I could be wrong but I think they can overwork the alternator . Also not a fan of lithium batteries especially inside the cab . Just do a search for lithium battery fires in cars . AGM battery much safer and hold their charge well also cheaper but heavier .
Yeah that is interesting, so the AC charger is keeping the voltage up which the redarc thinks means the alternator is on and thus switches on the DC to DC system. And then the DC to DC charger does its thing and demands lots of amps to charge second battery and that then drops the starter. So that blue cable is for sure one answer, you could put a relay against the car being in gear and ignition on if you wanted. OR you could put an isolator between the alternator (with correct current rating) and the starter battery, and sense the DC-DC charger from the alternator side, you could then charge the starter and the DC-DC wouldnt know about it, and when the alternator spins the isolator would energise and charging will work like normal, You could still join the batteries together if you needed(because you will energise the isolator),and could sense both (If the redarc actually cares). Just my quick thoughts.
Sounds about right to me what you explained Marc.
If the trigger wire was hooked up to ignition on Source you would not have this problem Or just charge your auxiliary battery and let it trickle charge back to the starting once it stopped off
Hi Andrew sorry if you've already mentioned this but i don't remember, are you going to fit one of those sealed water cooled alternators to the new truck to illuminate to dust, dirt and water crossing problems and make it more reliable, I imagine there very expensive but it also maybe peaces of mind too mate. Seeya Rob
Done.
Why not run power supply from ALT directly to DCDC charger?
Andrew, have you explored the capabilities of combination of CTEK SMARTPASS 120S & CTEK D250 (total of 140 amps) batteries management system? You may want to consider reviewing some of the Swedish CTEK products. It might be useful in the situation with two power sources, e.g. vehicle alternator and solar panels.
I believe you will agree that it is not a good practice to connect multiple charging sources directly to either the Primary battery or Secondary battery. Multiple batteries and multiple charging sources must be managed in desirable manner using a controller or management system
I know the CTek systems very well. Used them for years. This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
Thanks for the warning Andrew. It sounds like the DC-DC charger is smart, but not smart enough.
This is not a problem I’m trying to solve. And neither is this a mystery as to why it happened. It can and will happen to anyone using a DC-DC setup. It's the nature of how DC chargers work. All of them with the exception of those relying only on a trigger wire. The solution is to charge the auxiliary batteries first. It's that simple.
4xoverland Then edit your video accordingly. As it is, it sounds like you’re blaming the equipment, when all the equipment was doing exactly as it was designed to do.
I would have been interested in what the voltage was doing, it must of been bouncing up and down as the charger started up and the power supply fails and restarts.
How is starter battery connected to second battery?