At what point does a battery need more than one BMS?

I’m finishing up a 12s4p 10.5 AH pack and I was just thinking that with most BMSs providing around 60ma of balance current, there has to be a point where that’s not enough to keep a given capacity in balance. Anyone have any insight into this?

How would one wire a second BMS? Just totally parallel with the first assuming they’re both charge-only?

If you use a charge only bms, it doesnt matter as long as you let the battery ‘charge’ longer than normal (Up to 100%+Lets say 1h).

When your cells are full, but not complete balanced, your bms will do the rest.

Didn’t someone on the forum have an issue with balancing at 60ma and the whole pack not balancing?

Yeah I seem to remember something like this. That’s why I was curious.

A pack only needs one BMS. You never have to use two.

Is it true then that a BMS can send current to only one parallel group if all the others are at 4.2v?

You could get a Bestech bms. they balance at 126ma. It’s still not a lot but its twice as fast as Battery Supports.


I don’t think you should ever need more than one BMS. just one good BMS

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