I have put together one small pack, 24 volt 50 ah, and am in the process of putting together a second 24 volt pack at 280 ah. I pre-charged with solar power, and then finished off the top balance with the power supply.
My power supply was also broken, and I planned on top balancing without, but after messaging the company, I received a replacement prior to the pre-charge beint finished. Had the power supply not shown up so quick, this is what I planned for a top balance with BMS only:
BLUF: Make sure your BMS balancing is actually enabled.
GIve the BMS time to work with a low balancing amps.
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I think you could be good with the BMS, with a could of caveats. Your BMS balancer needs to turn on to balance, and is also limited to whatever the specs or setting is. I just did a top balancing with a 100 ah overkill BMS for my 24 volt cells. The BMS does not top balance until cells reach 3.4 volts And charging. These are configurable, to all the time verse just charging and the voltage per cell is also adjustable.
So, what I’d recommend is to charge your battery to a per cell average of more than when your BMS turns on. My BMS turned on at 3.4, so my charging voltage was 3.43 volts Approximately per cell. At that point my BMS displayed balancing on the cells that were balancing. If you don’t trigger the BMS’s charging, there will be no balancing.
Second, is a BMS will not balance as well as a Heltec active balancer, at least not as quickly. I don’t know the amps the BMS pushes at, so with 26 AWG wires, I assume 1 amp. That means no more than 1 amp per hour. A 280 amp hour cell mismatched will take a quite a while to balance.
If it takes quite a while to balance, You may want to consider leaving Flost at the same voltage as bulk charge and have a slight load on in the daytime.
My point would be not to use the batteries for normal day to day loads until the BMS equalizes them, which could take days or more. 1 amp per cell balancing will take a long time for bigger packs if they are mismatched.
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To give you some stats of the 280 ah packs I just balanced, each of the two batteries was 24 volts and 280 ah, so 6720 wh. Each battery took about 4.2kw on the 24 volt 15 amp SCC for a pre-charge before being moved to the 3.65 10 amps top balance. THe power supply only needed 3 hours.
My cells were also grade A and really well matched.