This is a great explaination especially to the begginner showing generally how a BMS works and why a BMS is important. It doesn't tackle the current limitations and temperature cutoff stuff so hopefully you can make a more advanced video tackling sizing a BMS and explain the other functions. Great content, sir.
Bottom balancing will result in a ragged end voltage and a balanced discharged voltage. Usually the ragged charged voltage is not a terrible difference but when you remove the charge it will bleed off the top and usually be quite balanced at fully charge resting voltage. Takes a bit to bleed off the charge voltage to a stable resting voltage. Usually around 3.35 volts.
That cell that is filling faster is your low capacity cell in the bunch. If you charge to 3.5 volts and your low cell goes to 3.65 your pack is fine and let the charge bleed off to static voltage and I bet you will see 3.35 or maybe 3.4 volts per cell. So all have the same capacity at this point and will all be equally balanced at the bottom if you don't let it go below 2.5 volts. Monitoring the voltages is fine. If you have a cell that reaches 3.65 volts long before the others and there is still a bit of time before your termination voltage is reached and if that difference puts that one cell above like 3.8 volts then you need to swap in a better battery that has a similar capacity if you want to go BMS free.
I am still on the fence about a BMS and in the end I bought a 100amp BMS with a Bluetooth module. (24v system, 100AH LIFEPO4). The application displays the individual cell voltage and pretty much all parameters can be changed. In the end I decided for a BMS because of the low voltage cut-off since the inverter is not connected to the solar load controller. It also does cell balancing (only 2amps so it might take a while for a 280ah cell, haha) so that is a bonus. It handles 60amps draw for about 45 mins without a problem but we'll have to see in the long run if it keeps operating. So far I am really impressed with it. And the phone app is kinda nice.
Great feedback, Peter. A BMS is a must! There is no way to keep these cells in balance without one. 2A balance current is a lot. Mine has only 250mA, I believe.
@@OffGridGarageAustralia Hi Andy. I touched both terminals on my battery with a spanner and it has dropped to 8v and wont work . Is it possible to change the BMS or did i destroy my battery. I hope you can help with some advice. Thank you my friend
@@thestoicloner It looks like you fried a cell. If I were you I'd dissassemble it and measure each cell individually. Very likely the BMS is fried too.
Great explanation! You can also top or bottom balance the cells as well. For using with off grid solar , most are now recommending top balancing. You can take your cells (In parallel) connect a DC Power Supply Variable 30V 10A to the bank and take them all up to 3.65v. Disconnect the cells and put them back in series and your done! Will Prowse has a great video on doing just this. Thanks for sharing!
I think the purpose of top/bottom balancing is to get the cells prepared to be installed into a pack. It's a starting point only. The idea (of top/bottom balancing, and NOT using a BMS) is to rely on the cells kind of bouncing around between the min and max voltage of the weakest cells, without using a BMS. But this is flawed long term, because cell properties will change over time, and you don't want to have an outage of your system while you top/bottom balance again. Doing a top/bottom balance at the beginning and then building your pack with a BMS, will give the BMS the best chance of doing it's job. If you introduce an additional active balancer into the mix, this will enhance the BMS by keeping cells balanced from each other, not just burning power into heat to lower the high cells. This gives you the maximum power out of the pack, but it will cost the most.
There is a better solution to the unbalanced pack. Use an active balancer equalizer capacitors board which take charge from the highest cell and dump it in the lowest cell. It will keep them within 5mv. The solar charger control the charge and the inverter control the discharge. If you want more energy from the sun in cloudy days use solar panels in series with 150v capable mppt chargers.
Are you sure about the active balancer claim - can you point us to specifications that show this feature of active balancers vs non active BMS? Personally, your comment and others making other ludicrous claims for active balancers reek of marketing hype.
@@MiniLuv-1984 While I have no way of knowing whether the OP was acting in good faith, I do distinctly remember Julian Ilett having a few videos on active balancers as opposed to passive/bottom/top balancers, to balance his supercap/ultracap banks. The ones I saw _I believe_ were roughly 6 months-1 year ago. Also vaguely remember a few videos on DIY Arduino projects accomplishing the same task, utilizing Digital-Analog Converters, for battery banks far in excess of typical series counts. I'm not certain whether he was part of those as well, or in misremembering other RUclipsrs. You know, I should probably examine this subject personally, if only to be more accurate regarding this topic in the future.
@@NightsReign Thanks NightsReign - I did watch Julian's coverage of active balancing, and I really like the idea of active balancing, but from what I've seen, power savings, and super accurate balancing are not founded in practical reality. I mean many BMS balance at 30 or 100mA - and for a short stretch of time to adapt the cell to that of the pack, now a quick and dirty, order of magnitude calculation tells me that to discharge say 100mV at 100mA amounts to 1mW and that may be for, I don't know, an hour? of the total charge time of the cell. With a 100AH cell, at 3.2V having 320Wh, to quibble over saving 1mWh sounds, like I mentioned, marketing hype rather than practical advice. This OP's comment sounded like active balancers are more precise "5mV" - what??? I don't normally react much to gibberish in comments, but this and other comments in this video really got under my skin. Again, thanks for responding, its great to discuss stuff with other commenter like yourself. When I'm wrong, I find out about it pretty quick and I do attempt to right my own wrongs (and there are many things I misunderstand or simply don't understand).
@@MiniLuv-1984 The other issue with only using an active balancer instead of a bms is that it lacks all the other safety features a proper bms provides, such as over charging, over discharging, over or under temperatures, too much charging current, too much discharging current, etc. If the balancer fails you'll only know if you have some other system monitoring it, if your charger fails and puts out too much voltage you'll only know when your pack fails, generally if your bms fails it simply disconnects the pack so long as its a decent quality one. So while an active balancer might help when used with a bms to handle larger swings in voltage than the BMS can do itself, it's just not a good solution all by itself because it leaves multiple ways for the batteries to be damaged.
@@MiniLuv-1984if I were not sure, I'll not be guiding people in the wrong direction. This one is 2A but for one of my 280ah 48v pack I am using 10A balancer to bring the pack within 5mv. ruclips.net/video/rQgOet7AH0I/видео.html. And of course these balancers aren't long lasting as BMS but you can get more power out of the pack. As for charging I use several makeskyblue which I can adjust my top voltage to 54v and the inverters cut off point is adjusted to 48v for the bottom limit.
sorry sir, if there is a weak cell in the row it will be the first which reaches the max. voltage and will also be the first which is at the lowest value decharging the battery. Only cutting off the process will help to rescue the weak cell not balancing.
i was thinking that the best connnection for batteries is in packs of four , a parallel of two in series . and that forms a block , for a scale up, next you go to four blocks . the reason behind this is to keep a uniform charge and discharge of the batteries ,without a single battery or more ,goes between two other batteries . and i think the measuring points for calculating where an error in the uniformity exists , are less .
Thank You for posting very useful information, and this leads to my power question on this subject. When I bring in a solar panel charge controller, how do I assure that the power controller is controlled by the BMS and the BMS dominates the charging process.
Wow, that's great. And brave. How often do you check them and I guess you use them right in the middle of the curve before they hit any steep sections?
@@OffGridGarageAustralia Hi It is with a lot of respect to you and not least the time you use on all the videos 👍 Nop... That is wrong, if you will run without BMS you need to bottom balancing all cells. You need to drain all the battery down to 2,75? V (down to the knee wher there is no energy pr. milli volt), get the last digit so close as possible on all cells and at same temperature. Measure one week later, if the difference is to high repeat the process until it is right, then you NEVER have to doo that again I have a battery pack 42 Cells from 2012 (Thunder Sky Cells 160 Ah) and it is running just fine, last checkup 1 week ago and all is just fine. So yes I check the cells now and then 1 - 3 yeas apart. It is used in my car and is charged at least once a week. Cell Voltage 3,65 - 2,95 (Charging current 50A. Regenerate breaking 150 A.) Maximum Discharge current 350 A It is imperative that the cells are bottom balanced, since you don't know the capacity of the cells. If you drain a top balance pack down to say 2,95 you might have a problem since the cell with the lowest capacity might be wrongly polarized and the cell is Dead. My cells variator about 15 Ah. If you or anyone wish to know more about bottom balancing, search for "jack rickard evtv" it is an olde video and unfortunately Jack is Dead. If you want to know more about lithium cels behavior and how much the drift search for "Professor Jeff Dahn (Dalhousie University") runingtim 1.13.30 This video will help almost any one to understand more about LiFePo4 cells. Enjoy the videos they are worthwhile !!!
I don’t run a bms myself but I only run 20-80%(mainly 60-80)of the battery. I topped balance and haven’t had any drift after 1 year so far(still 10mv). I’m running 18x 8s2p 70ah 24v bmw lithium batts. I would need 18 bms to correctly wire them up...no thanks lol. My Victron inventors and solar charger only charge up to 32v and my batteries need 33.6v for max charge. This means I will never be able to over charge. I check once a week with multimeter and thermal for hot spots once a month. You need to top balance with them all in parallel up to 3.65v then wire in series and charge max to 3.4v like you did. This will extend the life of your batts too.
It could be confirmation bias for me, but I've noticed that bottom balancing in parallel before charging to the top balancing voltage, helps optimize things somewhat, so the cells more accurately mirror the characteristics of each other once being reconfigured to series. Depending on your level of OCD and how important the project is, intermittently pausing the charge to allow time to rest, applying a load briefly, possibly repeating a rest interval, then resuming charging can yield dividends. My unmedicated ADHD and autism, among other neurodivergent issues mean I've gotta fully disengage whenever I can't remain hands-on, since allowing myself any opportunity to botch an experiment by overlooking something important will forever be my undoing... I don't have any firsthand experience with LiFePO4 chemistry, _but_ NiCd, NiMH, Li-Ion (cylinder/prismatic/pouch cells), LiPo, and Pb, seemed to have followed this trend for me in the past. From what I can deduce, when the paralleled cells are fully discharged, then allowed adequate recovery time before charging to full, the pesky tenancy of the top performing cells quiescently trickling a handful of nA to the rest of the pack...for seemingly *YEARS* _(or at least until your perfectionism melts your mind in aggravation),_ that issue appears essentially absent. I'm very curious though, what was the impetus for your settling on 32V inverters and such? It struck me as an arbitrarily peculiar voltage which I haven't seen much in the past. Is that maximum output voltage from your PV system?
Yes, that is absolutely correct, just 5 steps ahead ;) 3.4V would be my preferred voltage for these cells. I'm not expecting the balancer of the BMS will actually ever kick in with such a 'low' voltage. You could run such a Cellmeter8 for your pack too. Just be aware it sucks its energy from cell #1 and #2.
@@OffGridGarageAustralia No, *NOT* absolutely correct ... If he charges an 8S battery pack to 32 Volts, he certainly can OVER-CHARGE one cell while under charging the other 7 cells. Charging to only 32 Volts does *NOT* prevent over-charging of any one cell. Checking your cells "once per week" does not prevent a problem from occurring while you are asleep or while you are away from your home ...
OR, take multiple separate windings from a transformer (rectified etc) to each cell... the power transfer will scale relative to the voltage difference, so the cell with the lowest voltage will get the most current, and balancing will occur during the whole charge time... a cell with 0.2V left to go will get twice the current as a cell with 0.1V left to go, so they will all finish charging at the same time. This way, batteries that don't get chance to fully charge will still get balanced
I love this video! Human BMS I love it. It shows you exactly why you should use a BMS unless you want to do all that unnessary manual work but it is an excellent way to teach BMS tech.
Bms is indeed always needed, but balancer in some situations is not needed and can actually cause imbalance. I have made battery packs from samsung and panasonic 18650 cells and used them in high power diving lights for over decade, and especially Samsung cells tend to self balance over time, with voltages being very close to each others. If balancer is used, the differences grow bigger. I think this happens because there are natural fluctuation in cell voltages but capacity in long term decrades much more evenly. When using balancing, it is actually charging different cells with different capacity, causing different degredation over time. When cells are in parallel, each of them receive exactly same amp hours but possibly different watt hours.
I am 77 years old and have lots of experience with battery systems. always use series connection. never parallel. if you need more capacity make the cells higher capacity. where I retired we had 2 radio back up banks of 400 ah. 6 cells in series. they still met spec at 22 years old. no BMS at all. If you add a 2nd battery to your vehicle to run your ham stuff etc. add a circuit breaker in series with a N.O. relay that comes on with IGN(NOT ACC) so when the engine is running both batteries charge properly and when parked the 2nd battery can get run down but your vehicle will still start. NEVER use a battery charging splitter. the splitter causes both batteries to be undercharged and lots of trouble with that.
You don't need a BMS if you use a separate DC-DC buck converter for each cell only for charging. The advantage of this is you don't need to balance each cell, they will be always charged to the voltage set in converter.
Absolutely need a BMS :) For over-charge, over-discharge, and temp (hi/low) protection to cut-out a load. Balance as a feature of the BMS is good as well but not as important as the basic protections of a BMS.
Lol, great vid man! That cell checker if you hold down the right button it will go into balancer mode if you want to balance them while charging. Pretty handy cheap device. Another option out there if you want to get it to work a little more efficiently is to get an active balancer they take the voltage on the high cell and transfer it to the low cell instead of wasting the energy using a load resistor. Fairly cheap the only caveat is you need to have your own low voltage shutoff. I prefer a regular BMS with my smaller battery banks but as you go bigger the BMS can't handle the amperage. So options with a larger bank are to use a regular BMS and have it control a relay using the output wires. My setup I went with an active cell balancer and a low-voltage cut-off relay, Lots of options out there got to choose what works best for you.
@@OffGridGarageAustralia I wonder if it's simply a difference of models from the same manufacturer, or they mistook yours as an altogether different device?
8:00 the picture suggests that you can charge a lifepo4 battery to 4,2v. that is wrong and dangerous. you have to stop at 3,65v. I dont know what kind of diagramm you got there. lipo is 4,2v but the charge curve is different.
Yes, thank you. I've now blurred out the scale of the graph. It was more to explain the steep incline of the curve at the beginning and end of charging. But yeah, it could confuse people. Thanks for picking this up and letting me know.
I used to let connected one of those cell meters on my scooter battery 7S 25.4V 60 Ah and after some charge/discharge cycles I had cell nr 1 and nr 2 with a significant lower voltage relative to the other 5 cells. Finally I realized that the meter to power the circuits uses the 2 first cells. Now I only connect the meter cable for some minutes to check the voltage and no more problems with the balance of the 7 series. Thanks for your excellent videos. PS: Just bought a JK BMS 150 Amp for my 15 kWh solar battery pack and I am very happy with it. All the best from Portugal.😬
When you have only a 4 cell battery pack, it is easy to charging the cells individually, at your desired voltage and current to recharge them up again!! I first charge mine, as' a full battery, till almost reaches its limits, then finish off, just charging the individual cells to their full potential, thus keeping the cells balanced and ready for a further discharge. Regards George.
So true, a BMS is necessary. However people should be very wary that not all BMS's do the Balancing feature. Some will just disconnect the cell if it goes outside its parameters. Separate Balancer/Equaliser boards are available to add onto battery packs with a BMS not including this feature.
I believe the initial balancing maybe was a bit off. Charge the cells to 100%. Discharge a bitt individually to exactly the same voltage before disconnecting, then charge to 3,56V in parallell. I do bottom balancing, but that is the same thing, except for balancing at the low state. I managed to get them to meet at 2,5V at the same time. And since we have control over the top battery voltage, we can stop charging when the highest cell reach whatever you wish. If the balancing was good, that will be nearly the same every time. I try to not use BMS because I think it is a dumb fix to a problem that should be overcome otherwise. However, I have one that I will try.
Just connecting LFP cells i parallel will not balance them. To balance them (top balance) you have to charge them to 3.65V while connected in parallel.
Another thing to consider is temperature. The fact that the outside cells will be a couple of degrees warmer or colder will affect individual charging efficiency. Subtle but will over time lead to an imbalance.
I've got this battery in use for 6 months now and could never even measure a temperature increase while charging or discharging (max 60A discharge). But yeah, you're right, this could affect imbalance as well.
HAHA I love this, I came here ready to flame this video, but the mature viewer in me watched till the end. When I was first learning lifePo4 batteries, one of the first things I did was balance the batteries and then call it a day. Long story short, on a sunny day, the 100 AH batteries in a 4s config took a 40 amp charge and completely bulged out 2 out of the 4 batteries. I wanted to make sure someone wasn't spreading miss information, and you are doing an excellent job of helping teach why in deed you actually need one. Another good mention would be an active one (BMS) that moves power between cells, vs a passive one that burns off the higher cells as heat. I suppose a battery operator could use alligator clips to connect the high and low cells :) Great Job!
Great video, the biggest issue I have is that most BMS devices have very limited current capabilities to discharge a cell and when you have high capacity cells like you show here (maybe 240Ah) they can struggle to bleed off the charge.
I thought the same but it's all about finding the right settings and over time even a small discharge and balancing will work. My BMS does only 0.2A balancing and it can balance all 16 280Ah cells down to 1-3mV deviation.
I'm using 12V Lifepo4 7Ah batteries that are designed for use in a UPS. They have built-in BMS which keeps the cells balanced and also provide over, under and short circuit protection! I have them wired up in series for 48V which also needed some sort of balancing so what I did was to use an MPPT charge controller for each 12V battery, that way each battery pack will be charged separately as the charge controller is adjustable for the maximum voltage! I have tried the same thing with 18650 lithium ion batteries in series, I have been charging them to 4.2V each at the same time, some stop charging earlier and some later but they never go over and they are automatically balanced! Not sure if you understand what I have done, picture it as a series of car batteries, now take a few 240V car battery chargers and connect one charger to each battery and turn on all the chargers! They might be all in series but because they are being charged individually, they will always be in balance and you never have to check on them. The MPPT charge controller that I'm using is from eBay, it's just a circuit board with no enclosure! I think that they cost $10AU with $5 shipping, they are rated for 100W so for me that means a total of 400W of charging, they can also be paralleled for twice the current output and they have a potentiometer to tune it exactly to the solar panel that you are using for maximum power point tracking! And they track extremely fast! I have had others where I would wonder what they were doing because they were so slow! You see the sunshine come out and it's like it's thinking about what it's doing! No so with this little thing! As soon as there's ambient light first thing in the morning, it's already on and trying to charge... Higher voltage is so much more efficient, with the 48V system, I just had to use 4 12V Led Down lights per room which meant that I didn't have to use thick cables to carry the current to the lights... And because my batteries are small and in their standard UPS style case, they are cheap if I need to get more storage capacity! They cost $70AU each as opposed to $500 each if I chose to go with higher capacity from the beginning! And because I'm using multiple smaller batteries, I can charge and discharge at higher current without causing them to heat up and becoming damaged so basically if I could get away with just four $500 batteries to cover everything that I need, I would prefer to get 8 at half the size, you can charge them twice as fast...
Active charger i am a fan of Cost very little an keep bank perfectly balanced , charger an inverter needs to be set correctly as lose protection that a Bms may give
Thank You Andy for showing us this cell meter 8. Its would be nice to have a independent control monitor beside the BMS, ideal for people like me who suffer from cell phone allergies ; )
@@OffGridGarageAustralia Thank you, yes there are "overwhelming fancy looking" displays for my Jikong BMS, but they cost 6AUD more and they are less convenient to operate. The Cellmeter8 costs less than 10AUD here on Lazada. It fits perfect for my 24V battery and I get some redundancy this way for more security : )
One of the better explanations of how/why a bms is needed, I would also imagine some capacity is lost when one cell gets to the maximum voltage and all the rest are somewhere below and in a large bank this could add up to a noticeable amount.
The heat is much better since I covered the whole garage i solar panels. It can get up to 35° in summer inside the garage for a few hours though but cools down during the night again. BSA?
Me personally I would rather use a balance charger than to use a bms l. Then have a cell monitor with a buzzer alarm when a particular cells drops to say 2.7 volts.
Most likely I'm not home if the battery is fully charged or discharged. A buzzer will not work in this case. You always want a BMS for your battery to protect it.
Good morning Mr Andy. Thanks for this well explained video on why a BMS is needed. I have a JBD BMS who will not allow charge or discharge and this happened after my 24V LIFEPO4 DIY battery drained to zero percent (0%) (from Xiaoxing app). When the BMS is connected to the SCC, the voltage will rise quickly and register full charge delivering 0 amps. I charge it directly via the SCC to about 36% (3.23v per cell) )and still the BMS did not start. When I connected the load via inverter the voltage of 25.9V quickly drained to 17.3v and the inverter disconnected. The specs of the BMS is (AP 20S006 20S 200A). I tested charging the battery pack directly with SCC and also discharging with an inverter and it works. It means it is the BMS that is the issue. Kindly help with the solution. Attached is the picture of the BMS model too. Thanks
So, when I have a JK BMS (1A active balancing) bind to my cells and connect a "dumb" charger (= simple power supply) with two cables - I will not need to be the BMS operator? Meaning: with a BMS connected to the pack, I will not need an intelligent (= pricy) charger, right? Thank you for your very good & funny videos!
I would be looking at a balancing current of the BMS of at least 500mA, most only do about 10 to 20ma and be able to data log the voltages between the cells
@@OffGridGarageAustralia I am using Stuart Pittaway.s setup, It is a DIY open source BMS, I have used it in a few of these my bank builds, just search Stuart Pittaway in RUclips, or look at my RUclips channel for some of them.
I’ve been going through the same journey, minus the solar panels. I tried to charge my 280ah cells to 3.65 to do a capacity test. I have 16. I became impatient and hooked them up to my 48v hybrid inverter, without a bms. I figured it would be ok if I charge to 3.5v and then top off with my bench supply. Terrible mistake :( I had a cell charge to almost 5v! A couple were over 4v while the rest were at 3.34. Very expensive mistake.
Yikes!! How _"impatient"_ are we talking here? Lmao Was this a stress test for the full battery pack, following your individual capacity tests, *or* did you basically pull them from the delivery box, crudely lash them together in series, flip the switch, and wander away for several hours...? 😬🤔
@@NightsReign lol No, I did wire them in parallel first and tried to top balance them for two days. But I was getting nowhere fast. All the voltages matched prior to charging with the inverter. I just couldn’t get the cells past 3.3v. I actually tried for two nights to charge them on the hybrid inverter. The first night the inverter stopped charging at 53.1v, which was roughly 3.3v per cell. The second night, I kept messing with the settings and restarting it to get it to charge to around 57.5v, but it only charged to 54v. I didn’t babysit the charging because I assumed that the pack was balanced and all cells would charge at about the same rate. I assumed wrong. I was pissed I couldn’t get them to charge fully at first. But when I noticed one cell looking like a metal balloon, I became very grateful the inverter cut off. I was able to discharge the overcharged batteries pretty quickly, but the other cells are only at 3.34v now. I’m now trying to source one cell to replace the one that looks like a bomb. But it looks like I’ll have to pay a minimum of 4 cells at 3x the cost if I want something quickly.
Hello, haha yes this ALWAYS happens to me as well, whenever want to work on the solar system... snow... u have a MASSIVE advantage in AUSTRALIA (always above 10°C) vs GERMANY (0°C) because BATTERIES HATE 0°C :D
Andy, pls check which method your new BMS uses to balance the cells. Most common method used by BMS-es is to drain the most charged cell into "heat" - if this is your case, an active balancer would be recomanded to be used, in addition to your BMS (as posted by Will Prowse on his YT-channel). The active balancer does it's work by charging the cells with lower voltage from those with higher one - so it is a more economical method. In this situation a BMS is no longer needed since the loading is taken care by the charge controller and the discharging by the inverter and the balancing by the active balancer - BUT, the usage of a BMS would be an additional safety net!
If you are charging your Lithium iron phosphate batteries with a manual charger (16s), can you hook up the negative cable of your charger to your Daly BMS black lead (p-) cable? I guess I’m asking if it works, will it hurt the BMS? Will the BMS limit the constant voltage charger that is designed to charge 16 s to 58.4vdc?
The charger should always be connected to the P- of the BMS. In case one cell runs off and spikes with a high voltage, the BMS will turn of the charger. That's all the BMS will do. It won't limit anything but only turns of charging or discharging at the lower end as per set voltages. Does that makes sense?
I think that no BMS is not a good idea. The batteries are too expensive. Have at least a watchdog running to disconnect in case things get out of hand. There are many cheap ways to do this. Even with an arduino and a couple of mux shields. Check the voltage of one cell every second. Sound a warning if things worsen. Disconnect the battery pack if things get really bad. You don't need to do any balancing usually. Just accept that the lowest cell capacity dictates end of charge/discharge. Return the worst cell to the vendor, if it is out of spec and get a new one. Or add a little 18650 to that cell (fused!), to add to that individual cells capacity.
lol...When using Lithium cells in series you ALWAYS need a BMS. People with experience like myself know this..especially with LifePo4 that you have there...the more you cycle the cells especially on deep discharge the more the cells will start to vary because they wont all be the same resistance. Also, on deep discharges once a cell gets to a safe low voltage cutoff the BMS stops the discharge and in the case of charging, the charge if one cell gets to the safe upper limit of charge. By the way...that little device might be able to discharge ONE of those prismatic cells .01 volt in..oh...a week maybe???..They are good for monitoring the cell difference in your pack for sure and thats the main function in a pack like you have.
Probably the most significant content. This video should be modernized or at least remastered and re released again. Excellent! Now tell us more about paralleling cells und one series bus voltage please. ✌️♥️👍
This is a great video, but quick question. If I were to build a 8s4p battery, would I need 4 8s BMS hooked up to each block? Same if I put the same cells into a 48V 16s2p. Would I need 2 16sbms? Or would I need a 32cell BMS I can hook up to each individual cell?
For new, balanced cells, if you slow charge and discharge (0.2C max) they should take a lot of cycles to drift. I this case, you don't need a BMS (for this purpose). A simple meter like you showed, preferably with an alarm, would be adequate to warn you to manually balance the cells when needed.
@@MiniLuv-1984 . If that is the case, and they were perfectly balanced before the test, they are not matched (meaning they have different capacities/internal resistance), and should not be put in the same bank. Matched cells, previously balanced will NOT drift by this much, specially with such low C rate. I have seem boat installs without BMS (boats have a lot of sub 1 second peak discharges, a 300+ Amp BMS is hard to find and very expensive, the 100Amp ones go into over current protection straight away), cycled everyday, be fairly balanced (within 0.1v) after 6 months of use. Of course I'm not against the use of a BMS. With high C rates and/or unmatched cells, it is a necessity.
@@paial I have A123 cells in a 4S2P configuration in a homemade powerbank and in three years I have balanced them twice - and that was only for fun rather than necessity. I agree, if they are well matched and you don't overstress them, and you keep an eye on them, you don't necessarily need a BMS.
I’m new at this, but, confused, my MPPT cannot have the battery disconnected while solar panels are connected, doing so will damage the MPPT charge controller. So i think an active balancer is what I need. The charge controller and the inverter should be the only way things get shut off automatically. So I need to top balance my batteries and then find the best setting for the overall voltage to stop charging. And also the same with the inverter as far as discharging goes.
I've been running my 12 200 ah Winston pack for four years, on exakt the same cheap PROGRAMMEBLE WINCONG PWM solar charger WITHOUT a BMS, works with no problem ( I first used a more expensive MPPT, but in my specific setup with has a lot of schading from trees ,the PWM with 2 100 watt panels in IN PARELLEL, gives the same or even more amps to the battery's, in my opinion you can get away with a cheap * PROGRAMMEBLE* PWM controller just as well, and as long as you do your initial TOP BALANCE RICHT THEY, DO NOT HAVE MUCH CELL VOLTAGE DRIFT ( as long as you don't charge higher than 13.5 volts total pack voltage) drifting only occurs at the edges of the charge curve ,so try to stay within 2.8 - 13.5 volts and your LiFEpo4 pack will have a save and healthy long live WITHOUT a BMS ( many BMS UNITS have actually to small resistors to effectily discharge those big capacity cells so a lot of " pumping" happens to get at even cell voltage) this by itself can shorten cell life and FOR UNDERVOLTAGE PROTECTION MY 2000 WATT INVERTER HAS DAT BUILD IN, SO I'M HAPPY WITHOUT THE CLUTTER of BMS wiring. this works of course for a stationary solar system good,on my EBIKE (WITH MUCH SMALLER lion cells) I do use a BMS ,for two reasons mainly. A. Lion is a potential dangerous chemistry ( Life ps4 is much more safe) and second, when biking I do not monitor pack voltage that well and can quicker arrive at total depleting the pack ( after Wich I must peddle so hard) Nice video btw, and thanks for showing
Great feedback, thanks a lot. I totally agree with you. I have planned to charge my cells to 3.35V only, so 13.4V in terms of a 12V pack. I could see exactly what you just described, the cells stay close together unless you exceed 3.4V. The they start to drift apart a lot. As we are trying to be as beginner friendly as possible, I will still recommend a BMS for the sake of protection the battery. Interesting finding you have with the PWM controller. I think your two panels in series with a MPPT could boost your current significantly?
@@OffGridGarageAustralia yes in series can give more efficient charging butt, only when there is no shading...in my case o ly one of my panels gets sometimes shaded ( in summer) by a big tree ,so after some experimenting I've found that parallel panels in combi with a PWM works just as good , AGAIN A BIG reason to switch to series is of course running long cable length, and easier expanding to more panels,( higher voltage/small amperage,cheaper cable, en less line power loss ,for a small setup like I'm using not so much benefit. I would like to emphasize especially for the newbies to FORGET ABOUT LEAD, nowedays, just when prices ( thanks to china) of LiFEpo4 starts dropping, it is foolish to stay with lead chemistry battery's, especially for solar, charging efficiency of a LiFEpo4 setup is way higher than even a good set of lead batteries, not to mention ,although more expensive upfront due to the very Long cycle life of litium ,the return on investment ( Roi) is way lower....
What an excellent explanation and demonstration of the function of a BMS. Thanks Andy.
Thanks Ben ☺️
Brilliant! I came here thinking I could avoid a BMS, but now you made it clear I need one (and entertaining at the same time)! I'm subscribing.
Thank you so much!
You can avoid a bms
This is a great explaination especially to the begginner showing generally how a BMS works and why a BMS is important. It doesn't tackle the current limitations and temperature cutoff stuff so hopefully you can make a more advanced video tackling sizing a BMS and explain the other functions. Great content, sir.
Thanks, I will show more of these BMS bowel once we set one up. But, yeah, there is more to it, than just balancing and voltage protection.
Thank you, Thank you, Thank you!!! This was the best (and funniest) explanation I have heard on the BMS. You have a great way of teaching.
Bottom balancing will result in a ragged end voltage and a balanced discharged voltage. Usually the ragged charged voltage is not a terrible difference but when you remove the charge it will bleed off the top and usually be quite balanced at fully charge resting voltage. Takes a bit to bleed off the charge voltage to a stable resting voltage. Usually around 3.35 volts.
That cell that is filling faster is your low capacity cell in the bunch. If you charge to 3.5 volts and your low cell goes to 3.65 your pack is fine and let the charge bleed off to static voltage and I bet you will see 3.35 or maybe 3.4 volts per cell. So all have the same capacity at this point and will all be equally balanced at the bottom if you don't let it go below 2.5 volts. Monitoring the voltages is fine. If you have a cell that reaches 3.65 volts long before the others and there is still a bit of time before your termination voltage is reached and if that difference puts that one cell above like 3.8 volts then you need to swap in a better battery that has a similar capacity if you want to go BMS free.
Good to see this content still available. Well explained Andy. Enjoy watching your videos.
I am still on the fence about a BMS and in the end I bought a 100amp BMS with a Bluetooth module. (24v system, 100AH LIFEPO4). The application displays the individual cell voltage and pretty much all parameters can be changed. In the end I decided for a BMS because of the low voltage cut-off since the inverter is not connected to the solar load controller. It also does cell balancing (only 2amps so it might take a while for a 280ah cell, haha) so that is a bonus. It handles 60amps draw for about 45 mins without a problem but we'll have to see in the long run if it keeps operating.
So far I am really impressed with it. And the phone app is kinda nice.
Great feedback, Peter. A BMS is a must! There is no way to keep these cells in balance without one. 2A balance current is a lot. Mine has only 250mA, I believe.
@@OffGridGarageAustralia Hi Andy. I touched both terminals on my battery with a spanner and it has dropped to 8v and wont work . Is it possible to change the BMS or did i destroy my battery. I hope you can help with some advice. Thank you my friend
@@thestoicloner It looks like you fried a cell. If I were you I'd dissassemble it and measure each cell individually. Very likely the BMS is fried too.
@@FBPrepping Thank you
Great explanation! You can also top or bottom balance the cells as well. For using with off grid solar , most are now recommending top balancing. You can take your cells (In parallel) connect a DC Power Supply Variable 30V 10A to the bank and take them all up to 3.65v. Disconnect the cells and put them back in series and your done! Will Prowse has a great video on doing just this. Thanks for sharing!
Thank Dan. The pack is balancing for the last 4 days already. It takes a while with the small DC buck converter I'm using...
I think the purpose of top/bottom balancing is to get the cells prepared to be installed into a pack. It's a starting point only.
The idea (of top/bottom balancing, and NOT using a BMS) is to rely on the cells kind of bouncing around between the min and max voltage of the weakest cells, without using a BMS.
But this is flawed long term, because cell properties will change over time, and you don't want to have an outage of your system while you top/bottom balance again.
Doing a top/bottom balance at the beginning and then building your pack with a BMS, will give the BMS the best chance of doing it's job.
If you introduce an additional active balancer into the mix, this will enhance the BMS by keeping cells balanced from each other, not just burning power into heat to lower the high cells. This gives you the maximum power out of the pack, but it will cost the most.
On your cellmeter, push cell and mode button together and it's supposed to balance them. Not a BMS replacement but usefull anyway.
Thank you, sir.
There is a better solution to the unbalanced pack. Use an active balancer equalizer capacitors board which take charge from the highest cell and dump it in the lowest cell. It will keep them within 5mv. The solar charger control the charge and the inverter control the discharge. If you want more energy from the sun in cloudy days use solar panels in series with 150v capable mppt chargers.
Are you sure about the active balancer claim - can you point us to specifications that show this feature of active balancers vs non active BMS?
Personally, your comment and others making other ludicrous claims for active balancers reek of marketing hype.
@@MiniLuv-1984 While I have no way of knowing whether the OP was acting in good faith, I do distinctly remember Julian Ilett having a few videos on active balancers as opposed to passive/bottom/top balancers, to balance his supercap/ultracap banks. The ones I saw _I believe_ were roughly 6 months-1 year ago.
Also vaguely remember a few videos on DIY Arduino projects accomplishing the same task, utilizing Digital-Analog Converters, for battery banks far in excess of typical series counts.
I'm not certain whether he was part of those as well, or in misremembering other RUclipsrs.
You know, I should probably examine this subject personally, if only to be more accurate regarding this topic in the future.
@@NightsReign Thanks NightsReign - I did watch Julian's coverage of active balancing, and I really like the idea of active balancing, but from what I've seen, power savings, and super accurate balancing are not founded in practical reality.
I mean many BMS balance at 30 or 100mA - and for a short stretch of time to adapt the cell to that of the pack, now a quick and dirty, order of magnitude calculation tells me that to discharge say 100mV at 100mA amounts to 1mW and that may be for, I don't know, an hour? of the total charge time of the cell.
With a 100AH cell, at 3.2V having 320Wh, to quibble over saving 1mWh sounds, like I mentioned, marketing hype rather than practical advice. This OP's comment sounded like active balancers are more precise "5mV" - what??? I don't normally react much to gibberish in comments, but this and other comments in this video really got under my skin. Again, thanks for responding, its great to discuss stuff with other commenter like yourself. When I'm wrong, I find out about it pretty quick and I do attempt to right my own wrongs (and there are many things I misunderstand or simply don't understand).
@@MiniLuv-1984 The other issue with only using an active balancer instead of a bms is that it lacks all the other safety features a proper bms provides, such as over charging, over discharging, over or under temperatures, too much charging current, too much discharging current, etc. If the balancer fails you'll only know if you have some other system monitoring it, if your charger fails and puts out too much voltage you'll only know when your pack fails, generally if your bms fails it simply disconnects the pack so long as its a decent quality one. So while an active balancer might help when used with a bms to handle larger swings in voltage than the BMS can do itself, it's just not a good solution all by itself because it leaves multiple ways for the batteries to be damaged.
@@MiniLuv-1984if I were not sure, I'll not be guiding people in the wrong direction. This one is 2A but for one of my 280ah 48v pack I am using 10A balancer to bring the pack within 5mv. ruclips.net/video/rQgOet7AH0I/видео.html. And of course these balancers aren't long lasting as BMS but you can get more power out of the pack. As for charging I use several makeskyblue which I can adjust my top voltage to 54v and the inverters cut off point is adjusted to 48v for the bottom limit.
You are wonderful. I am learning from your experience. Keep on.
Greetings from Saudi Arabia.
Thank you for your feedback!
sorry sir, if there is a weak cell in the row it will be the first which reaches the max. voltage and will also be the first which is at the lowest value decharging the battery. Only cutting off the process will help to rescue the weak cell not balancing.
Awesome||| thank you for the simple easy to understand explanation. I like how you used the lights as a load to explain what the bms does internally.
By the way I like the phrase “what the frog”
Thanks a lot for your feedback, Bobby. Much appreciated.
i was thinking that the best connnection for batteries is in packs of four , a parallel of two in series . and that forms a block , for a scale up, next you go to four blocks .
the reason behind this is to keep a uniform charge and discharge of the batteries ,without a single battery or more ,goes between two other batteries .
and i think the measuring points for calculating where an error in the uniformity exists , are less .
Thank You for posting very useful information, and this leads to my power question on this subject. When I bring in a solar panel charge controller, how do I assure that the power controller is controlled by the BMS and the BMS dominates the charging process.
I’ve been running my 4s Calb 180ah cells without bms for over 3 years. Top balanced once at the start and they are still within .02 v of each other
Wow, that's great. And brave. How often do you check them and I guess you use them right in the middle of the curve before they hit any steep sections?
@@OffGridGarageAustralia Hi It is with a lot of respect to you and not least the time you use on all the videos 👍
Nop... That is wrong, if you will run without BMS you need to bottom balancing all cells.
You need to drain all the battery down to 2,75? V (down to the knee wher there is no energy pr. milli volt), get the last digit so close as possible on all cells and at same temperature. Measure one week later, if the difference is to high repeat the process until it is right, then you NEVER have to doo that again
I have a battery pack 42 Cells from 2012 (Thunder Sky Cells 160 Ah) and it is running just fine, last checkup 1 week ago and all is just fine. So yes I check the cells now and then 1 - 3 yeas apart.
It is used in my car and is charged at least once a week.
Cell Voltage 3,65 - 2,95 (Charging current 50A. Regenerate breaking 150 A.) Maximum Discharge current 350 A
It is imperative that the cells are bottom balanced, since you don't know the capacity of the cells. If you drain a top balance pack down to say 2,95 you might have a problem since the cell with the lowest capacity might be wrongly polarized and the cell is Dead.
My cells variator about 15 Ah.
If you or anyone wish to know more about bottom balancing, search for "jack rickard evtv" it is an olde video and unfortunately Jack is Dead.
If you want to know more about lithium cels behavior and how much the drift search for "Professor Jeff Dahn (Dalhousie University") runingtim 1.13.30 This video will help almost any one to understand more about LiFePo4 cells.
Enjoy the videos they are worthwhile !!!
A brilliant way to explain the importance of a BMS. Thank you.
You are welcome!
I don’t run a bms myself but I only run 20-80%(mainly 60-80)of the battery. I topped balance and haven’t had any drift after 1 year so far(still 10mv). I’m running 18x 8s2p 70ah 24v bmw lithium batts. I would need 18 bms to correctly wire them up...no thanks lol. My Victron inventors and solar charger only charge up to 32v and my batteries need 33.6v for max charge. This means I will never be able to over charge. I check once a week with multimeter and thermal for hot spots once a month.
You need to top balance with them all in parallel up to 3.65v then wire in series and charge max to 3.4v like you did. This will extend the life of your batts too.
It could be confirmation bias for me, but I've noticed that bottom balancing in parallel before charging to the top balancing voltage, helps optimize things somewhat, so the cells more accurately mirror the characteristics of each other once being reconfigured to series. Depending on your level of OCD and how important the project is, intermittently pausing the charge to allow time to rest, applying a load briefly, possibly repeating a rest interval, then resuming charging can yield dividends.
My unmedicated ADHD and autism, among other neurodivergent issues mean I've gotta fully disengage whenever I can't remain hands-on, since allowing myself any opportunity to botch an experiment by overlooking something important will forever be my undoing...
I don't have any firsthand experience with LiFePO4 chemistry, _but_ NiCd, NiMH, Li-Ion (cylinder/prismatic/pouch cells), LiPo, and Pb, seemed to have followed this trend for me in the past.
From what I can deduce, when the paralleled cells are fully discharged, then allowed adequate recovery time before charging to full, the pesky tenancy of the top performing cells quiescently trickling a handful of nA to the rest of the pack...for seemingly *YEARS* _(or at least until your perfectionism melts your mind in aggravation),_ that issue appears essentially absent.
I'm very curious though, what was the impetus for your settling on 32V inverters and such? It struck me as an arbitrarily peculiar voltage which I haven't seen much in the past.
Is that maximum output voltage from your PV system?
Yes, that is absolutely correct, just 5 steps ahead ;)
3.4V would be my preferred voltage for these cells. I'm not expecting the balancer of the BMS will actually ever kick in with such a 'low' voltage.
You could run such a Cellmeter8 for your pack too. Just be aware it sucks its energy from cell #1 and #2.
@@OffGridGarageAustralia No, *NOT* absolutely correct ... If he charges an 8S battery pack to 32 Volts, he certainly can OVER-CHARGE one cell while under charging the other 7 cells. Charging to only 32 Volts does *NOT* prevent over-charging of any one cell. Checking your cells "once per week" does not prevent a problem from occurring while you are asleep or while you are away from your home ...
Always learn more when I watch your videos! Thanks, J
First explanation of a BMS that made sense to me. Thanks!
OR, take multiple separate windings from a transformer (rectified etc) to each cell... the power transfer will scale relative to the voltage difference, so the cell with the lowest voltage will get the most current, and balancing will occur during the whole charge time... a cell with 0.2V left to go will get twice the current as a cell with 0.1V left to go, so they will all finish charging at the same time. This way, batteries that don't get chance to fully charge will still get balanced
I love this video! Human BMS I love it. It shows you exactly why you should use a BMS unless you want to do all that unnessary manual work but it is an excellent way to teach BMS tech.
Bms is indeed always needed, but balancer in some situations is not needed and can actually cause imbalance. I have made battery packs from samsung and panasonic 18650 cells and used them in high power diving lights for over decade, and especially Samsung cells tend to self balance over time, with voltages being very close to each others. If balancer is used, the differences grow bigger.
I think this happens because there are natural fluctuation in cell voltages but capacity in long term decrades much more evenly. When using balancing, it is actually charging different cells with different capacity, causing different degredation over time.
When cells are in parallel, each of them receive exactly same amp hours but possibly different watt hours.
Thanks so very much for the details and explaining the BMS.
0:58
Come to Pakistan...
Here in Summer you can use 14 hours Solar panels and in winter 10 hours.
Thanks, Andy. This video was very clear about how a BMS works. You just topped up my knowledge. Have a nice day.
Thanks, you too!
I am 77 years old and have lots of experience with battery systems. always use series connection. never parallel. if you need more capacity make the cells higher capacity. where I retired we had 2 radio back up banks of 400 ah. 6 cells in series. they still met spec at 22 years old. no BMS at all. If you add a 2nd battery to your vehicle to run your ham stuff etc. add a circuit breaker in series with a N.O. relay that comes on with IGN(NOT ACC) so when the engine is running both batteries charge properly and when parked the 2nd battery can get run down but your vehicle will still start. NEVER use a battery charging splitter. the splitter causes both batteries to be undercharged and lots of trouble with that.
You don't need a BMS if you use a separate DC-DC buck converter for each cell only for charging.
The advantage of this is you don't need to balance each cell, they will be always charged to the voltage set in converter.
Yes, you can charge each cell individually with it's own 'charger'. But you should not connect these converters all to the same power source 🔥
Absolutely need a BMS :) For over-charge, over-discharge, and temp (hi/low) protection to cut-out a load. Balance as a feature of the BMS is good as well but not as important as the basic protections of a BMS.
Yes, I absolutely agree.
sh*t can happen no matter how careful you are, so just use BMS. Ur battery are expensive
This is exactly what he is saying at the end of the clip. Obviously you have not watched to the end.
需要我的喇叭吗
Lol, great vid man! That cell checker if you hold down the right button it will go into balancer mode if you want to balance them while charging. Pretty handy cheap device. Another option out there if you want to get it to work a little more efficiently is to get an active balancer they take the voltage on the high cell and transfer it to the low cell instead of wasting the energy using a load resistor. Fairly cheap the only caveat is you need to have your own low voltage shutoff. I prefer a regular BMS with my smaller battery banks but as you go bigger the BMS can't handle the amperage. So options with a larger bank are to use a regular BMS and have it control a relay using the output wires. My setup I went with an active cell balancer and a low-voltage cut-off relay, Lots of options out there got to choose what works best for you.
Thanks for the feedback. If I hold down the right button it goes into discharge mode...
@@OffGridGarageAustralia I wonder if it's simply a difference of models from the same manufacturer, or they mistook yours as an altogether different device?
Sorry yes different than mine. They look the similar but mine is a 5-in-1 Cell Meter. Made by Tenergy.
Thanks you, brilliant explanation for a BMS.
When I finally got to your sick sense of humor, I couldnt help but laugh!
😂 got you, ey?
8:00 the picture suggests that you can charge a lifepo4 battery to 4,2v. that is wrong and dangerous. you have to stop at 3,65v. I dont know what kind of diagramm you got there. lipo is 4,2v but the charge curve is different.
Yes, thank you. I've now blurred out the scale of the graph. It was more to explain the steep incline of the curve at the beginning and end of charging. But yeah, it could confuse people. Thanks for picking this up and letting me know.
We have wall to wall sunshine today perfect for test, but temp will be about 30C
I used to let connected one of those cell meters on my scooter battery 7S 25.4V 60 Ah and after some charge/discharge cycles I had cell nr 1 and nr 2 with a significant lower voltage relative to the other 5 cells. Finally I realized that the meter to power the circuits uses the 2 first cells. Now I only connect the meter cable for some minutes to check the voltage and no more problems with the balance of the 7 series.
Thanks for your excellent videos.
PS: Just bought a JK BMS 150 Amp for my 15 kWh solar battery pack and I am very happy with it.
All the best from Portugal.😬
When you have only a 4 cell battery pack, it is easy to charging the cells individually, at your desired voltage and current to recharge them up again!! I first charge mine, as' a full battery, till almost reaches its limits, then finish off, just charging the individual cells to their full potential, thus keeping the cells balanced and ready for a further discharge. Regards George.
Don't cells in series settle into voltage equilibrium (about 24hrs) on their own anyway?
hi.... very clear "how to and why" video.. thank you!!!
You're welcome!
So true, a BMS is necessary. However people should be very wary that not all BMS's do the Balancing feature. Some will just disconnect the cell if it goes outside its parameters. Separate Balancer/Equaliser boards are available to add onto battery packs with a BMS not including this feature.
I believe the initial balancing maybe was a bit off. Charge the cells to 100%. Discharge a bitt individually to exactly the same voltage before disconnecting, then charge to 3,56V in parallell. I do bottom balancing, but that is the same thing, except for balancing at the low state. I managed to get them to meet at 2,5V at the same time. And since we have control over the top battery voltage, we can stop charging when the highest cell reach whatever you wish. If the balancing was good, that will be nearly the same every time. I try to not use BMS because I think it is a dumb fix to a problem that should be overcome otherwise. However, I have one that I will try.
Great video! Love the dry humor!
Just connecting LFP cells i parallel will not balance them. To balance them (top balance) you have to charge them to 3.65V while connected in parallel.
Another thing to consider is temperature. The fact that the outside cells will be a couple of degrees warmer or colder will affect individual charging efficiency. Subtle but will over time lead to an imbalance.
I've got this battery in use for 6 months now and could never even measure a temperature increase while charging or discharging (max 60A discharge). But yeah, you're right, this could affect imbalance as well.
HAHA I love this, I came here ready to flame this video, but the mature viewer in me watched till the end. When I was first learning lifePo4 batteries, one of the first things I did was balance the batteries and then call it a day.
Long story short, on a sunny day, the 100 AH batteries in a 4s config took a 40 amp charge and completely bulged out 2 out of the 4 batteries. I wanted to make sure someone wasn't spreading miss information, and you are doing an excellent job of helping teach why in deed you actually need one.
Another good mention would be an active one (BMS) that moves power between cells, vs a passive one that burns off the higher cells as heat.
I suppose a battery operator could use alligator clips to connect the high and low cells :)
Great Job!
Great video, the biggest issue I have is that most BMS devices have very limited current capabilities to discharge a cell and when you have high capacity cells like you show here (maybe 240Ah) they can struggle to bleed off the charge.
I thought the same but it's all about finding the right settings and over time even a small discharge and balancing will work. My BMS does only 0.2A balancing and it can balance all 16 280Ah cells down to 1-3mV deviation.
yes I used one of these on my homemade ebike battery Shawn McCarthy showed me on his channel.u don't need a bms if you monitor your batteries he said
You could always keep the 3.6V bank in parallel and use some kind of inverter to generate the 13.6V to 48V you need for your purpose.
Uhm, probably not, the currents would be BIG. I mean really big!!!
But the distances could be very short. I think I may go this route.
I'm using 12V Lifepo4 7Ah batteries that are designed for use in a UPS. They have built-in BMS which keeps the cells balanced and also provide over, under and short circuit protection!
I have them wired up in series for 48V which also needed some sort of balancing so what I did was to use an MPPT charge controller for each 12V battery, that way each battery pack will be charged separately as the charge controller is adjustable for the maximum voltage!
I have tried the same thing with 18650 lithium ion batteries in series, I have been charging them to 4.2V each at the same time, some stop charging earlier and some later but they never go over and they are automatically balanced!
Not sure if you understand what I have done, picture it as a series of car batteries, now take a few 240V car battery chargers and connect one charger to each battery and turn on all the chargers! They might be all in series but because they are being charged individually, they will always be in balance and you never have to check on them.
The MPPT charge controller that I'm using is from eBay, it's just a circuit board with no enclosure! I think that they cost $10AU with $5 shipping, they are rated for 100W so for me that means a total of 400W of charging, they can also be paralleled for twice the current output and they have a potentiometer to tune it exactly to the solar panel that you are using for maximum power point tracking! And they track extremely fast! I have had others where I would wonder what they were doing because they were so slow! You see the sunshine come out and it's like it's thinking about what it's doing! No so with this little thing! As soon as there's ambient light first thing in the morning, it's already on and trying to charge...
Higher voltage is so much more efficient, with the 48V system, I just had to use 4 12V Led Down lights per room which meant that I didn't have to use thick cables to carry the current to the lights...
And because my batteries are small and in their standard UPS style case, they are cheap if I need to get more storage capacity! They cost $70AU each as opposed to $500 each if I chose to go with higher capacity from the beginning! And because I'm using multiple smaller batteries, I can charge and discharge at higher current without causing them to heat up and becoming damaged so basically if I could get away with just four $500 batteries to cover everything that I need, I would prefer to get 8 at half the size, you can charge them twice as fast...
Just ordered four cells off your link. Hope I get the same capacity tests as you did.
Thanks for your vids.
Thank you :)
@Dr SpaceMan
- Are you Off-Grid ?
@@vtorsi610 Nah I wish. Intend on using the pack to replace 3x200ah AGM batteries in a camper van.
Great job explaining BMS technology
This is the best and the funniest video I've seen today lol thanks a lot for the info.
Active charger i am a fan of Cost very little an keep bank perfectly balanced , charger an inverter needs to be set correctly as lose protection that a Bms may give
Indonesia, you can't be wrong
Thank You Andy for showing us this cell meter 8. Its would be nice to have a independent control monitor beside the BMS, ideal for people like me who suffer from cell phone allergies ; )
Some BMS now come with a display where you can check on the voltages of all cells...
@@OffGridGarageAustralia Thank you, yes there are "overwhelming fancy looking" displays for my Jikong BMS, but they cost 6AUD more and they are less convenient to operate. The Cellmeter8 costs less than 10AUD here on Lazada. It fits perfect for my 24V battery and I get some redundancy this way for more security : )
Learned a lot by from this video! Thanks. Keep it up
Thank you!
Without you Andy. I would be lost.
CHEERS MY UNMET FRIEND!
One of the better explanations of how/why a bms is needed, I would also imagine some capacity is lost when one cell gets to the maximum voltage and all the rest are somewhere below and in a large bank this could add up to a noticeable amount.
I like the way your garage/shed is set up. Does it get hot inside in summer? Plush, what does BSA stand for, Boy Scouts of America?
The heat is much better since I covered the whole garage i solar panels. It can get up to 35° in summer inside the garage for a few hours though but cools down during the night again.
BSA?
Me personally I would rather use a balance charger than to use a bms l. Then have a cell monitor with a buzzer alarm when a particular cells drops to say 2.7 volts.
Most likely I'm not home if the battery is fully charged or discharged. A buzzer will not work in this case. You always want a BMS for your battery to protect it.
17.7 min waisted that I will never get back! Thanks buddy!
i really HATE clickbaits....but this one got a thumbs up for being the most instructive one😊
Hahaha, thanks Alex. It's not real clickbait, right?
Hey thanks you've got me on me guard now
Good morning Mr Andy. Thanks for this well explained video on why a BMS is needed.
I have a JBD BMS who will not allow charge or discharge and this happened after my 24V LIFEPO4 DIY battery drained to zero percent (0%) (from Xiaoxing app). When the BMS is connected to the SCC, the voltage will rise quickly and register full charge delivering 0 amps. I charge it directly via the SCC to about 36% (3.23v per cell) )and still the BMS did not start. When I connected the load via inverter the voltage of 25.9V quickly drained to 17.3v and the inverter disconnected.
The specs of the BMS is (AP 20S006 20S 200A).
I tested charging the battery pack directly with SCC and also discharging with an inverter and it works.
It means it is the BMS that is the issue.
Kindly help with the solution.
Attached is the picture of the BMS model too.
Thanks
funny start... nice and informative vid (specially the $11 part and the frogs ":o)) ... thank you.
BATTERY MANAGEMENT SYSTEM OPERATOR nice one sir.
So, when I have a JK BMS (1A active balancing) bind to my cells and connect a "dumb" charger (= simple power supply) with two cables - I will not need to be the BMS operator? Meaning: with a BMS connected to the pack, I will not need an intelligent (= pricy) charger, right? Thank you for your very good & funny videos!
Thanks, you good teacher, for me.
Million thanks
You are welcome!
You have so many trees for poly or mono solar panels. Try thin film solar panels for power in all types of conditions, even partial shading
Great advice.
The bms operators job though, I tried that but I quit lol
Keep the economy going...you can probably get jobkeeper payments when the batteries are all balanced.
You can use an active balancer to avoid cell drifts... I do it so an it works perfect.
Post a URL link and price of your Active Balancer ...
...beste Erklärung die ich gehört habe. Danke
With your humanity glowing through the lens, gives hope to the world 🌎
I would be looking at a balancing current of the BMS of at least 500mA, most only do about 10 to 20ma and be able to data log the voltages between the cells
The QUCC BMS I now have does 200mA and works well with that.
@@OffGridGarageAustralia I am using Stuart Pittaway.s setup, It is a DIY open source BMS, I have used it in a few of these my bank builds, just search Stuart Pittaway in RUclips, or look at my RUclips channel for some of them.
Excellent video sir, many thanks for that information!
Glad it was helpful!
Very good informative video that easily explains why you need a BMS and how it works. Well done and thank you.
I’ve been going through the same journey, minus the solar panels. I tried to charge my 280ah cells to 3.65 to do a capacity test. I have 16. I became impatient and hooked them up to my 48v hybrid inverter, without a bms. I figured it would be ok if I charge to 3.5v and then top off with my bench supply.
Terrible mistake :( I had a cell charge to almost 5v! A couple were over 4v while the rest were at 3.34. Very expensive mistake.
Ouch!
Yikes!!
How _"impatient"_ are we talking here? Lmao
Was this a stress test for the full battery pack, following your individual capacity tests, *or* did you basically pull them from the delivery box, crudely lash them together in series, flip the switch, and wander away for several hours...? 😬🤔
@@NightsReign lol No, I did wire them in parallel first and tried to top balance them for two days. But I was getting nowhere fast. All the voltages matched prior to charging with the inverter. I just couldn’t get the cells past 3.3v.
I actually tried for two nights to charge them on the hybrid inverter. The first night the inverter stopped charging at 53.1v, which was roughly 3.3v per cell. The second night, I kept messing with the settings and restarting it to get it to charge to around 57.5v, but it only charged to 54v. I didn’t babysit the charging because I assumed that the pack was balanced and all cells would charge at about the same rate. I assumed wrong.
I was pissed I couldn’t get them to charge fully at first. But when I noticed one cell looking like a metal balloon, I became very grateful the inverter cut off. I was able to discharge the overcharged batteries pretty quickly, but the other cells are only at 3.34v now.
I’m now trying to source one cell to replace the one that looks like a bomb. But it looks like I’ll have to pay a minimum of 4 cells at 3x the cost if I want something quickly.
the best controller/bms i have found for lifepro4 is electrodacus as it monitors the single cells
Interesting stuff, if however the MPPT had a built in BMS which would be sensible and very cheap to impliment, no biggee.
use lithium titanium batteries, they are safer = less management
how many mini cells are in each battery pack
Hello, haha yes this ALWAYS happens to me as well, whenever want to work on the solar system... snow... u have a MASSIVE advantage in AUSTRALIA (always above 10°C) vs GERMANY (0°C) because BATTERIES HATE 0°C :D
A superb example of why you need a bms!
Andy, pls check which method your new BMS uses to balance the cells. Most common method used by BMS-es is to drain the most charged cell into "heat" - if this is your case, an active balancer would be recomanded to be used, in addition to your BMS (as posted by Will Prowse on his YT-channel). The active balancer does it's work by charging the cells with lower voltage from those with higher one - so it is a more economical method.
In this situation a BMS is no longer needed since the loading is taken care by the charge controller and the discharging by the inverter and the balancing by the active balancer - BUT, the usage of a BMS would be an additional safety net!
But if the charge controller fails or a setting is not right... 🧨
@@OffGridGarageAustralia Therfore the "BUT" with capital letters 😉 in my comment
you got me there. position of BMS Operator taken :D
If you are charging your Lithium iron phosphate batteries with a manual charger (16s), can you hook up the negative cable of your charger to your Daly BMS black lead (p-) cable? I guess I’m asking if it works, will it hurt the BMS? Will the BMS limit the constant voltage charger that is designed to charge 16 s to 58.4vdc?
The charger should always be connected to the P- of the BMS. In case one cell runs off and spikes with a high voltage, the BMS will turn of the charger. That's all the BMS will do. It won't limit anything but only turns of charging or discharging at the lower end as per set voltages. Does that makes sense?
I think that no BMS is not a good idea. The batteries are too expensive. Have at least a watchdog running to disconnect in case things get out of hand. There are many cheap ways to do this. Even with an arduino and a couple of mux shields. Check the voltage of one cell every second. Sound a warning if things worsen. Disconnect the battery pack if things get really bad.
You don't need to do any balancing usually. Just accept that the lowest cell capacity dictates end of charge/discharge. Return the worst cell to the vendor, if it is out of spec and get a new one. Or add a little 18650 to that cell (fused!), to add to that individual cells capacity.
Colorado gets more sun than Florida the sunshine state . 300 plus days a year . Building my solar and battery bank always upgrading
lol...When using Lithium cells in series you ALWAYS need a BMS. People with experience like myself know this..especially with LifePo4 that you have there...the more you cycle the cells especially on deep discharge the more the cells will start to vary because they wont all be the same resistance. Also, on deep discharges once a cell gets to a safe low voltage cutoff the BMS stops the discharge and in the case of charging, the charge if one cell gets to the safe upper limit of charge. By the way...that little device might be able to discharge ONE of those prismatic cells .01 volt in..oh...a week maybe???..They are good for monitoring the cell difference in your pack for sure and thats the main function in a pack like you have.
i check balance once a month - balance if needed - 5 yrs off grid
How do you check? Let the BMS check or doing it manually?
Seems those lithium are still tricky I like old fashioned junkyard cheap but fair condition used and save $ I’ll never ever have
Probably the most significant content. This video should be modernized or at least remastered and re released again. Excellent!
Now tell us more about paralleling cells und one series bus voltage please.
✌️♥️👍
This is a great video, but quick question. If I were to build a 8s4p battery, would I need 4 8s BMS hooked up to each block? Same if I put the same cells into a 48V 16s2p. Would I need 2 16sbms? Or would I need a 32cell BMS I can hook up to each individual cell?
...and why I think one should hook both a passive BMS and an active BMS...
Herlich sympathisch und kompetent erklärt...Grüße aus Deutschland ^^
Excellent video, thank you for answering my questions!!!! 💪😉👍
Happy to help! Thank you.
For new, balanced cells, if you slow charge and discharge (0.2C max) they should take a lot of cycles to drift. I this case, you don't need a BMS (for this purpose).
A simple meter like you showed, preferably with an alarm, would be adequate to warn you to manually balance the cells when needed.
That is not what Andy just demonstrated. At 0.2C, for these cells, you are talking about 56A - he demonstrated substantial drift at 8A (~0.03C).
@@MiniLuv-1984 . If that is the case, and they were perfectly balanced before the test, they are not matched (meaning they have different capacities/internal resistance), and should not be put in the same bank. Matched cells, previously balanced will NOT drift by this much, specially with such low C rate. I have seem boat installs without BMS (boats have a lot of sub 1 second peak discharges, a 300+ Amp BMS is hard to find and very expensive, the 100Amp ones go into over current protection straight away), cycled everyday, be fairly balanced (within 0.1v) after 6 months of use. Of course I'm not against the use of a BMS. With high C rates and/or unmatched cells, it is a necessity.
ruclips.net/video/etFCo3fwm8U/видео.html
Another REAL WORLD example. 30 months of daily cycling, NO BALANCING, 0.02v unbalance.
@@paial Clearly, the cells used in this video ( by Off-Grid Garage ) are not matched ...
@@paial I have A123 cells in a 4S2P configuration in a homemade powerbank and in three years I have balanced them twice - and that was only for fun rather than necessity.
I agree, if they are well matched and you don't overstress them, and you keep an eye on them, you don't necessarily need a BMS.
I’m new at this, but, confused, my MPPT cannot have the battery disconnected while solar panels are connected, doing so will damage the MPPT charge controller. So i think an active balancer is what I need. The charge controller and the inverter should be the only way things get shut off automatically. So I need to top balance my batteries and then find the best setting for the overall voltage to stop charging. And also the same with the inverter as far as discharging goes.
Hilarious! Made my day! I'll use a BMS to skip the BS! Thank you for posting!
Hahaha , the REEL solution is a Good BMS that handle the different voltage
I've been running my 12 200 ah Winston pack for four years, on exakt the same cheap PROGRAMMEBLE WINCONG PWM solar charger WITHOUT a BMS, works with no problem ( I first used a more expensive MPPT, but in my specific setup with has a lot of schading from trees ,the PWM with 2 100 watt panels in IN PARELLEL, gives the same or even more amps to the battery's, in my opinion you can get away with a cheap * PROGRAMMEBLE* PWM controller just as well, and as long as you do your initial TOP BALANCE RICHT THEY, DO NOT HAVE MUCH CELL VOLTAGE DRIFT ( as long as you don't charge higher than 13.5 volts total pack voltage) drifting only occurs at the edges of the charge curve ,so try to stay within 2.8 - 13.5 volts and your LiFEpo4 pack will have a save and healthy long live WITHOUT a BMS ( many BMS UNITS have actually to small resistors to effectily discharge those big capacity cells so a lot of " pumping" happens to get at even cell voltage) this by itself can shorten cell life and FOR UNDERVOLTAGE PROTECTION MY 2000 WATT INVERTER HAS DAT BUILD IN, SO I'M HAPPY WITHOUT THE CLUTTER of BMS wiring.
this works of course for a stationary solar system good,on my EBIKE (WITH MUCH SMALLER lion cells) I do use a BMS ,for two reasons mainly. A. Lion is a potential dangerous chemistry ( Life ps4 is much more safe) and second, when biking I do not monitor pack voltage that well and can quicker arrive at total depleting the pack ( after Wich I must peddle so hard)
Nice video btw, and thanks for showing
Great feedback, thanks a lot. I totally agree with you. I have planned to charge my cells to 3.35V only, so 13.4V in terms of a 12V pack. I could see exactly what you just described, the cells stay close together unless you exceed 3.4V. The they start to drift apart a lot.
As we are trying to be as beginner friendly as possible, I will still recommend a BMS for the sake of protection the battery.
Interesting finding you have with the PWM controller. I think your two panels in series with a MPPT could boost your current significantly?
@@OffGridGarageAustralia yes in series can give more efficient charging butt, only when there is no shading...in my case o ly one of my panels gets sometimes shaded ( in summer) by a big tree ,so after some experimenting I've found that parallel panels in combi with a PWM works just as good , AGAIN A BIG reason to switch to series is of course running long cable length, and easier expanding to more panels,( higher voltage/small amperage,cheaper cable, en less line power loss ,for a small setup like I'm using not so much benefit.
I would like to emphasize especially for the newbies to FORGET ABOUT LEAD, nowedays, just when prices ( thanks to china) of LiFEpo4 starts dropping, it is foolish to stay with lead chemistry battery's, especially for solar, charging efficiency of a LiFEpo4 setup is way higher than even a good set of lead batteries, not to mention ,although more expensive upfront due to the very Long cycle life of litium ,the return on investment ( Roi) is way lower....
@@giottodiotto1 How much did you spend for your 12 @ 200Ah Winston cells ?