Why not to use Daly BMS with MPPT controllers
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- Опубликовано: 14 окт 2024
- After a charge controller failure, this BMS that has a sole purpose of battery protection failed to protect a lifepo4 battery. I show inside a Daly BMS and why you should not use with a mppt charge controller.
DONT USE A CHEAP CHARGE CONTROLLER, AND BLAME IT ON THE BMS..
Your charge controller doesn't down convert the voltage from 90 down to12v, 24v or 48v? If you are sending 90v straight to your BMS then what happened is not the BMS' fault.
Maybe buy a better charge controller. MidniteClassic150, 200 or 250.
True.
Well its over voltage protected. However this is only cell side. And if the mosfetts fail they short. So honestly i agree that its not the bms at fault
you and 17 others just don't get it: the CC failed, that's what it is about :/
@@raedy07 the constant power source you mean?
The “04” in the MOSFET part number suggests a 40V rating. This means it can stand off a charger voltage of about 70V (40V on top of the battery voltage). It would probably survive if you had 2 x 60 cell panels in series, but not if 2 x 72 cell panels.
Very interesting discovery! Sorry for your problem. That was an expensive find, but those of us out here using FET based BMS's are thankful for you sharing your data. I am now suspect of my FET based Heltec/JK BMS, if it has a similar risk profile.
Yes indeed it would. There are some suggestions in in the thread on diysolar of using a snubber type arrangement to be blow the fuse. I have switched to using relays.
Think again, the only suspect here was the guy who didn't configure the equipment properly . If you tune a carb wrong on a two stroke dirt bike the engine will burn up ! same problem here . all voltages are configurable for different batteries. he just doesn't know how or why to set these perameters up...
I am glad you posted your experience. I have a EV and I was thinking about connecting 3 of 16s BMS in series. Total system is 48 cells in series. I purchased few different types of BMS including QUCC BMS with a relay. My concern was 500 amps initially. Later learned about FET limitation as a HV switch. So relay based bms is a better choice. Also for people who are trying to blame charge controller only. Even expensive charge controllers fail. Also BMS is designed to protect the cells and it failed to do so here. I was also thinking a Surge protection device will be solution here but those are put at input and in your case for 150 plus volt. But how about a 50v Surge protection at the output. I was thinking about using 450v charge controller and this is a real concern and scenario. Thank you for provoking majority of us to think and make our system design safer.
These failure conditions are always interesting, but it doesn't sound like this was the BMS's fault this time. The BMS does have over-voltage protection, but it is designed for nominal over-voltage (i.e. normal max charging voltages), not insane over-voltage. You should never apply more than around 35V to a 24V BMS, ever. No matter what the model.
A FET generally cannot handle reverse polarity, it basically becomes a diode. That's why there are two of them with one reversed... one for each direction. There is also an absolute maximum voltage potential, which for the FETs on a 24V BMS is probably somewhere around 40V. It is not going to be 96V or anywhere near 96V. Almost all BMS's are FET based. These are far, far superior to relay-based BMS's. Relay based BMS's have severe longevity issues, particularly when the relay trips while significant current is being run.
So this leaves the charge controller as the cause. You kept bandying about 90V+ .... that's the problem right there. You should never, ever, even in your thoughts, apply a voltage that high to a 24V battery bank or 24V BMS. No charge controller configured for a 24V system should ever put that much voltage on its output, whether MPPT or PWM. It sounds like the charge controller is mis-configured or shorted out or something.
You need an inline fuse as well.
-Matt
Yes, as explained in video cc failed. My point is that like myself many people think their BMS will protect their battery against a cc failure by turning off. If the cc fails then the the BMS is unable to turn off. I now use relays on the solar inputs. I understand how and why FETs and everything works,I am a electronics tech. My beef is that the manual does not state what voltage the FETs are rated for. This video was to help others think about the possibility that they too are not protected against cc failures. Oh and it was appropriately fused.
Its all the BMS fault...this is a cascade fault event....the bms detected high voltage that can only be 2 or 3v over the threshold and disconneted the inverter and the CC altogether from the battery...now you have a CC riding freely at the pv VOC that , as well explained in the video, fried the bms causing it to no longer protect the battery from the CC overvoltage
wait... are you the -Matt that has made comments in the arstechnica discussion section?
What brand and model was the solar charge controller? The reason I ask is that some MPPT charge controllers will have MOV's and a fuse right before the output to help with transients and controller failures. If they start dumping more than say 60v out the MOVs will clamp and blow the internal fuse to protect the devices down stream.
+1 to this. What MPPT? Important to understand mitigating factors.
It was a esmart. Will the MOVs really go at such a low voltage? I thought they would only serve for lighting surge protection or on AC input for higher line volatges... I am thinking about building a big crowbar circuit that I can put on output of all my charge controllers. A TVS or a SCR that can handle a 100A or so briefly to blow the fuses. I will have a bit more of a look at MOVs maybe I can find a appropriate one. It would be convenient to be able to use a MOSFET based BMS.
Daly says you can put 4 12 volt bms' in series for a 48 volt system. So it's probably a safe bet to say they can handle 60, possibly even 70 volts before shorting. I have taken apart both 12 volt and a 48 volt daly and the mosfets all have the same markings. So I assume they all use the same mosfets, no matter the voltage range. But expecting it to handle 90 volts is asking a little much. I'd have to put blame on your charge controller, not the bms.
Maybe using a high voltage sense that triggers a relay to short or open the solar input of the charge controller. You never want to open the battery side of a charge controller while sun is powering it. They can autoset set for a different voltage and fry too. I have a small resistor across the charge port to B- so the charge controller stays awake even if it trips overvoltage.
I have a battery monitor ordered with capability of switching relays on and off for overcharge etc, definitely going to be also fitting a cutout relay as an added safety feature, note, I also have a daly bms and not too impressed with its balancing.
Yes this may be a decent solution. The new diybms current monitor by Stuart Pittaway could do this too.
Thanks a lot for taking this aftermath video. It is pretty interesting and make at least aware of the potential danger we all are messing around. Thanks mate!
May I ask a question as I have ordered some lifepo4 batteries and currently do my research. Question would a fuse or breaker helps. I always under rate my fuses and breakers just in case, that is why I ask the questions. Oh one more question, how are you managing your system now?
No. Fuse circuit breaker etc is not the issue here. As stated what I am saying is that don't rely on your BMS to protect overcharge events if you are using solar string voltages beyond 60v. Currently using HV relays controlled by a seperate BMS to disconnect the solar incoming if a cell goes too high. Once balanced it should never trigger unless a charge controller fail.
@@jasondevine6014 please 🙏 can you post this setup? I would really love to learn from it
BMS,battery management system. it is used to manage battery, it doesn't give protection to over voltage charge. it is to protect battery for overcharge/undervoltage the battery. so it doesn't make sense for me if you hope BMS can protect from over voltage charge. unless the name is battery charge controller, so i assume it should control the voltage input and output.. :)
ONCE AGAIN, he said CC FAILED !
If higher voltage then stated is required on the battery to controller why not just build a voltage monitor circuit that trips a relay if voltage is above a set voltage like 35v
Are you saying that your MPPT solar charge controller failed and passed full v9ltage and current to the BMS? I understand that the bms did not open circuit because the voltage was above what it was rated to protect. My question is what kind of MPPT failed? I have had them fail but never pass current after failure. This is alarming. I have repurposed Tesla lithium ion NMC batteries.
If my BMS modules fail I would have a thermal runaway event. I have Midnite Classic, Outback Flexmax and Tristar in my main house system. I sure would like to know which MPPT CC failed and passed current. Thanks.
Esmart 3. When you consider the design of a mppt it is basically a buck converter so easily they can fail in the shorted state, some however have a crowbar protection circuit built in. So yes that is the point, we need to consider what could happen. I didn't here and it lead to a disastrous result.
I wonder what is your solar panel array looks like. What is your total power and what is each panel's power. Perhaps it is just safer to do paralles on your solar cells to use a low voltage input to the system?
Also what is your MPPT charger? I am using a Victron one and seems working nicely.
Otherwise you might want to check out the QUCC bms and they have some are using relays not mosfets. It might be more safer for your application.
Did you have any protection on the battery side? A fuse or a DC breaker? The BMS got 4x the V it is rated for. No surprise it has blown.
One thing is very important from your video: the cells blow but did not start a fire.
If that were a Li-ion/NMC battery then that would burn like hell.
Yes, but what is its maximum voltage that it can switch? That seems to be missing from the documentation that I can see. I think this situation is possible for many people as most run mppt controllers. The job of the BMS is to protect the battery in these failure mode cases. But yes lifepo4 is much safer than lion and thankfully so. The batteries actually still appear to work, although I will not trust these particular cells in any critical situation now that they have been so abused. It was no fault of the cells themselves. The overpressure vent did blow.
@@jasondevine6014 Yep, the BMS protection has a limit. A 24V BMS max has 40V MOSFET-s. Everything over it will damage it.
The crowbar circuit also not the perfect solution. If too less current then will not blow battery DC fuse. I am not sure it will even blow the Solar DC fuse.
I did not find an ideal relay solution either for my 48V with inverter/charger. If separate charger then Victron Battery Protector can work.
How did the MPPT die? What was the cause? Never saw an MPPT allowing the raw solar power to flow through.
How long did the MPPT overcharge the battery?
@@mrzed6597 where did you find 40v? I even opened the failed BMS but was not able to see a data sheet for the Chinese FETs.. the mppt is just a buck converter so if high side FET fails... I am now using diybms. I am using mechanical relays at moment but am testing my own relays with FETs rated for 200v. Should be ok besides lighting of course. I think that if a crowbar circuit was low enough impedance the output caps in the solar controller should have enough to blow the output fuse.
@@jasondevine6014 I am just guessing the 40V for the Daly. I use Heltec active BMS (and forget to check the mosfets on it :D ).
Some 48V MPP Solar PIP inverters have 75V IRFB3077PbF MOSFETs. There was even a topic where some replaced them with 100V SUP70040E-GE3-ND or CSD19535KCS MOSFETs.
I am not sure about relays. They can fail too. Connectors can burn together. If you have a good solution I will check it out :)
What type of mppt do you have.
Splendid! You need a camera tripod though.
thanks for charing! awesome information
Would it then be better to use a higher voltage battery pack and BMS? Operating closer to the system voltage of the panels?
Well yes but that is not always practical. I generally run 48v for house size and 24v for camper. If you go higher than 48v then you really need to start doing special safety precautions for all DC connections.
@@jasondevine6014 My pack and inverter are 48v aswell, I haven't gotten around to setting up solar yet...thanks for the lesson!
@@jasondevine6014 presumably a BMS capable of a range of series cells would be more resilient. for example, one that can do 8-24 S should be able to handle 100V in normal operation (if it is capable of both Li-Ion and LiFePo4).
Would it be possible to use around 30V zener diod with dummy load to dump the overvoltage?
Only as a trigger control voltage.
Sure you can. But this is a lot of power. You would need something like 500W of zener diodes(that's a lot of 10W ones), which would also make a nice heater.
I'm not sure you're define the charging voltage on mppt before like maximum 30V ?
The 90V coming to BMS through inverter is it possible that inverter failure?
every bms have a voltage they can't protect from, i guess that's why you still put a fuse between the battery and the mppt, i guess the fuse will trigger because of the voltage différence ? theyre will be a lot of amp going in ... what was the Charge controller brand?
i have 3 BMS and the Daly is the worse, it does not count the current going out if the inverter is connected to B- and the needle never moves down; (it will m ve up when the Sun comes out) if it was at,say,75%, it stays at 75% even until the battery is down at 0% (it shutts off at the voltages we set it to, though); if i connect the inverter to P-, when the battery is fully charged, then the BMS shutts off and the whole house suddenly goes "dark"; the JK BMS LEARNS to correlate voltages with SOC and does it very well; i repair,build, and sell inverters and i do not sell Daly any more.
Why arnt you showing your MPPT?
Ding, ding, ding. It’s one of those top secret Aliblabla “blowouts”, purchased during the Chinese New Year specials, with free shipping, three gold tokens and a toy giraffe.
Exactly, so everyone can treat it like a Covid19 carrier.
Bms is only there to balance cells in a series configuration. It’s purpose is not to protect cells from over voltage if supplied outside of specification. You should have had a fuse or circuit breaker between the power supply and the bms which would have protected against this issue. It would be the same for all bms.
No it was fused. You don't understand the issue.
@@jasondevine6014 hmmm possibly not but why would any BMS be able to shunt any voltage which is what I thought you were saying? Or was it you wernt concerned about the BMS but the fact it still passed high voltage on to the batteries.. Which if that was your point then I agree the DALY is not up to spec? Possibly in proper overall design the high voltage should have been caught before the BMS??
@@tigertoo01 my complaint is that Daly do not provide max voltage ratings. My point is a warning that many people consider the BMS as a switch able to turnoff the battery should something go wrong but as shown here, a simple and common problem of charge controller failure will not cause any fuses to blow and the BMS will not be able to protect. The BMS will only turn off a max of about 40v due to the FETs. This is not stated anywhere in manual and many dont think about this when connecting solar 70v mppt strings. This video is not a complaint about the Daly hardware but lack of specification and lack of consideration of what will happen should a single fault occur by the solar system installer, in this case, myself. No one is talking about this issue in their solar system designs. If you look at comments some good solutions have been suggested but a voltage triggered relay is simplest. I now use relay based BMS.
Have you looked at the Australian made (EV Power) BMS's? I think i will be going that way as i don't trust cheap chinese electronics. Their BCU RAPS has separate latching relays (240amp) for charge and load. It looks more expensive that a Daly but most people recomend sizing your Daly to double the current. In that case they are very similar price.
I had a look and yes that looks like a good alternative. Like I said I m using diybms now.
Can someone tag Will Prowse and Off-Grid Garage please. This needs to be investigated
What i have learned so far in the last 6 months is not too use Daly BMS and not to compress unless you you are going to kick those cells every day from 3.65 all the way down.
It just doesn't make sense because when you use a decent BMS and only 80% of the voltage range you get even 95% of it's capacity. Those last millivolts do not give you that much amps. You only shorten the life span of your cells.
put an relay controlled open close V contactor from shunt reading :)
How did the voltage get that high it should have switched off at about 30v then the volts can increase to 90 without damage
That's the problem. Solar panels will increase their voltage when not under load to VMax which means that for a mppt string maybe 80v or so. That's then too much for the FETs and they short.
I was about to order 5pcs of these Daly BMS. Could you elaborate what inverter ?
The inverter does not matter for what this video is about. Your inverter needs to match your loads and battery voltage.
@@jasondevine6014 I admire your patience here mate...
@@marcass100I was thinking the same thing. If it were me, I would probably have pulled the video by now.
I think a varistor and a fuse after the charging controller could solve the problem
A 40V fet has the breakdown at around 56V. If you pushed 90V on the pack means you have around 34V on the battery. You exceed the max rated cell voltage, and the 56V can be over the fets is limited by power dissipation capability. Anyway the 40V fet is more than enough for a 24V battery. BMS is well designed. Charge controller on the other hand is rubbish.
Yes, true if it is a 40v FET. My beef is that this is not advertised, explained in the manual or specs what voltage this FET is. Also many do not think about the issue of cc failure thinking the BMS will protect their battery like I did. The charge controller is the cause of the failure but thought the BMS will offer protection.
Use a contactor (it is fail-safe, but it has some idle consumption) or a shunt trip (no idle consumption but also not fail-safe)
Yes I have learnt my lesson. Relays on all solar inputs now.
@@jasondevine6014 What MPPT?
I'm confused.... Why was 90 volts going to your BMS?
Mppt panels 90v from panels... Cc shorted.
Lesson learned....All bms should have a Voc threshold published..if not then don't trust it....in this case the CC might have only spiked for a couple of seconds which is common even for the most expensive CC's... acid vrla sla or gel batteries won't see these spikes...but the bms will cut out the CC from the battery after only 1 second of these overvoltage situations letting the CC to ride freely at the pv Voc....and that's the concern...
Buy quality mppt scc and you won't have this issue. It's not your BMS fault.
What MPPT controller did you use?
A few are asking about what mppt controller. It was a esmart. But that is not the point. Any mppt controller runs at a higher solar input voltage and has the potential of failing. Is your battery really protected? The need is real to check the maximum voltage of solid state devices or use a mechanical relay. I have considered designing a crowbar circuit to put between charge controllers and BMS in order to blow the fuses if charge controller fails. This will allow a solid state BMS to be used safely with high input voltages.
@@jasondevine6014 Was the controller common ground or positive? you think that matters?
I think it was common positive but no my point is that the mppt controller does not matter, a BMS should protect your batteries. The Daly has a voltage limit to do this that is not well documented. I still do not know exactly what voltage it can actually safely switch. I suspect maybe 40v for 24v BMS. So if your open circuit panel voltage into the mppt is higher than 40v you have a potential issue if your cc fails.
@@jasondevine6014 yea thats crazy. do they made a high voltage disconnect. i use daly on my 24v system
@@RodneySolarCircuits not really. Best bet is use a seperate relay based BMS for now. Something like the batrium or I use diybms
I'd rather blame the charge controller for destroying the BMS and the battery. when I plug in dc power supplies to the mains I expect that if they fail they don't go supplying 240V when they are stated to supply 12V
Ac to DC supplies don't fail short. They are isolated. Most buck converters/charge controllers aren't, save a few.
@@jasondevine6014 if it's expected then a DC monitoring relay should be a necessary safety device, just as surge protection devices and fuses/circuit breakers are.
@@dedsert9653 yes. And that is my point. No one is talking about the need for these.
Sure are a lot of "wannabee engineers" on here. Watching a dozen youtube videos is not a substitute for a true comprehensive understanding of electronic circuit design. Keep your day jobs, fellas.
Do you have anything constructive to add? What's your assessment of the situation?
Poorly designed, low-quality Chinese junk controller failed, damaging other components in the process. End of discussion. Listening to everybody give their advice about zener diodes and contactors and high-voltage disconnect safety devices without understanding the cause of the problem. It takes a few years in class and 10 or 20 years in the field to get really good at this stuff. It's great that hobbyists are learning new things. But it is kind of amusing to listen to them throw their opinion around like they have some kind of idea what they're talking about. And yes, I do have something constructive to add, but I already said it. Keep your day jobs.
Most all REAL MPPT charge controller will not short HV solar DC to the Battery out. Morningstar, Schneider,Midnight Solar, Victron. They are protected and will not short the HV DC to the LV battery side. They spend the big $$$ to UL testing and certification for a reason. Don't go cheap get UL, ETL or other tested gear and you real lesson will have been learned.
You do understand how buck regulators work? Unless the cc uses a isolated topology, which some may, they can short solar to DC bus.
@@jasondevine6014 I sure do! Solar and renewables are my Job. If you would have purchased a Schneider MPPT or Midnight solar MTTP with shunt trip breaker you would not have burned up the battery bank. Schneider is fully isolated Midnight has a internal protection circuit that trips the shunt. Batteries are expensive so why trust cheap China non UL / ETL tested gear to try and save a buck. If you really want to use cheap BMS and China controllers then spend a hundred bucks and install a Morningstar Relay driver and connect to a contactor so if the Batt voltage goes over a certain voltage it will open the contactor and isolate the charging circuit (and save the battery pack). I commend you for bringing this issue to light, so others can learn from it. But Saying the Daly BMS is the issue is not true. Poor system design and cost cutting by purchasing cheap China gear is the root cause, not the Daly.
@@williambryce8867 thanks. Good to know what controllers can handle this type of situation, unfortunately this information does not seem to be published for most ccs. You are right I am trying to highlight system design issues that many dont think of. As I stated the Daly was not faulty, but it was not published its max VOC. I have now started using diybms shunt that also offers over voltage external relay output.
@@jasondevine6014 Yes, I had to dig to see who has isolated MPPT's I think anything over 150V should be isolated. I cringe to think of having a 600V MPPT short to the battery. But, the industry is getting better. MorningStar and Victron are not isolated so you better use a contactor based BMS. I could not find any China made MPPT's that are isolated and given the cost none probably are. Thanks for your video, it does highlight the Issues with MPPT and ALL BMS systems. So need to make good choices to protect the $$$ batteries.
There should be a breaker or fuse on all of the devices...you cant and should not expect the bms to act as a fuse/breaker
Fuse would not have helped. Overvoltage event and yes was fitted with properly rated breakers.
If you know how to configure the mppt controller voltages you wont have any problems . These systems are used all over the world with no problems when configured properly ! I hate it when people make video's about equipment , give it a bad report . and have no idea what or how to configure the equipment ! I really hope anyone who watches this video takes this into consideration .
Did you even listen to the video. Cc break sometimes. What happens then?
@@jasondevine6014 Your right , I am sorry I was so ignorant . Again , I'm sorry .
This is what happens when factory specs are not followed !
maybe your setting in scc matters..
Cheap charge controller plus cheap BMS = ruined battery
Such a waste of money . I have never encountered mppt failure. Simple - charge no more 50% of mppt rated power.
sooner or later all equipment will fail
@@raedy07 agree
If your MPPT controller has no "user programmable" threshold limits then you need a better MPPT. Yikes!
EXPENSIVE MISTAKE BRO , SORRY .
You're making a big mistake on the purpose of a BMS. If the voltage of your solar array (90v!?) has gone directly to your batteries, it's not the BMS's fault! The MPPT charge controller is the one to incriminate solely. His purpose is, precisely, to control the voltage that comes from your solar panels and redirects it to your batteries. In order to make his job, the BMS should get the right rated voltage it's designed for, that's all.
And how in the hell you get "90 something volts" from your solar panels for a 24v system? You should max out a 40v open circuit voltage!!
Why don't you show us your MPPT instead?
My point is that any mppt solar controller CAN fail..yes Chinese ones more often like in this case. You miss the point I am not wacking the Daly just saying many people don't think about what can happen yet think they have protected their battery with a BMS that disconnects when overcharged.... Well maybe depends on your panel voltage if you have a shorted cc.
@@jasondevine6014 Yep, MPPT charge controllers fail, sometimes, but never "blow up" batteries (with Bms in you case), unless you use Chinese cheap crap that doesn't have any circuit protection or, like it has been suggested, you made a mistake, either in the wiring sequence or in respect of the manufacturer' recommendations for your equipment.
Again, how in the hell you get "90 something volts"(0:48) from your solar panels for what it appears to be a 24v system?
Save more money, buy better charge controllers...ie MIdnite, Sol-Ark does me good.
@@fredericfray552 of course 90V, even cheap CC's handle 150V, expensive ones 400+V, what's your problem?? you want highV for a PV-array located far from batt-bank! he said IT FAILED !
@@raedy07 Here I am not arguing about the fact that you can have a greater PV voltage than your battery bank voltage. For e.g. I am on a 12v system and my victron mppt 100/20 can handle 48v, but i chose to have a 12v PV array just to be on the safe side, for convenience I could have 48v PV array instead, but we know what happens when mppts fail! But hey!, you want highV for a PV array located far from your battery bank, so be ready to blow bms+battery if CC fails! You will come and blame it on the bms...
Please update the title of this misleading video to "Why not to use any BMS with some unbranded MPPT controller which broke when I sent 90V to it" instead of doing a disservice to Daly. I'm surprised Daly haven't contacted you directly already for rubbishing their product when it had nothing to do with the BMS.
In this instance when you knew you'd be sending 90V to the MPPT, you should have placed a surge protector between the MPPT and the BMS.
Did you even understand what the video is about? Lookup failure mode analysis...
Mate, what does your troubleshooting method have to do with the fact you were using panels with an OCV of 90V and you knew this, and regardless decided to willy nilly hope that a BMS managing an 8S 24V battery would be able to surge protect your battery. When in reality you should have ensured the BMS would be protected by anything greater than 48V.
The fact that so many think BMS provides protection to the battery in terms of surge voltage is probably a problem in itself. If you look at the spec sheet or manual of the widely popular Overkill BMS, nowhere does it state the peak voltage the BMS can support.
Anyhow this brings me back to my original point. It's not the BMS at fault, but the MPPT controller itself, which you're still pretty coy about with its identity.
@@missingMBR he said 3months ago it was a esmart. wtf, all this people writing novels but can't be bothered to watch d vid properly. a CC is NOT SUPPOSED TO LET HV PASS !!!!
“When they go into c by bhnn b jbl n v V hav V by b mode” learn to speak please.
Stupid mistake but we all make them