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Hi. I am planning a Defender conversion.

1244 Views 7 Replies 5 Participants Last post by  remy_martian
As I was thinking of having two separate battery packs. Do I need two separate BMS’s ?
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Yes and no.

Ideally yes.

Or, you can connect balance wires to both packs, but, microscopic differences in battery chemistry, under massive load, can perhaps overload those balance wires. Also, there's a lot of high potential running amok on those fragile wires. If one were to ever short, it could have the full voltage of the pack across it and whatever it shorts to. It's probably fine unless you're drag racing.

It's almost impossible. You'd really have to fabricate a situation in which it becomes a problem.

Basically this is long-distance parallel. It's fine, unless something causes a large voltage difference between a cell on one pack and its mate in the other pack, and then causes current to flow, which is more current than the wire can handle. I can't really think of a situation that could cause that, but, it could. A solution could be to just use beefier wires to do your long distance parallel, then they can handle it better. Bit of a goofy setup though.
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