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Re: (ET) Battery pack rebuild on E20



I remember the arguments/discussions on buddy pairs. One issue that happens is like the Bolt battery if one cell goes bad then the pack controller doesn't realize it just went from a 60ah pack to a 30ah pack that will seriously reverse the remaining cell if you go too low.

The recommended way was to build long strings and connect at the ends with a fuse to blow if too many cells failed. Being out of sync 1.2 to 3.6 volts would not cause a meltdown.

But I'm dumb, put the cells on a 3a charge and after an hour noticed only some of them were charging with others at 0v. Then realized the coloration on two of the cells had faded and I connected the middle of the string backwards. Rebuilt it, charging just those cells for an hour to get back to even then will charge overnight. Note: Flooded NiCDs don't like being reversed.

C

On 11/24/2023 4:13 PM, David Roden wrote:
The norm in the road-EV world, back when conversions ruled the roost, was
to "buddy-pair" 6-volt or 12-volt modules (connect them in parallel), then
connect the pairs in series.

I'm pretty sure that that's how s/p lithium batteries are made, too, though
it's been a while since I've cut open a laptop battery.

What you're doing sounds like the opposite - connecting cells in 2 or 3
series strings, then connecting the strings in parallel.


David Roden - Akron, Ohio, USA

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