I have the exway flex, it’s served me well for the last few years…but range is not great now and I’m thinking of replacing cells (came with Sony vtc6).
Of course, it uses exway’s custom bms and whatnot. My question is, what might happen if I were to replace the cells with higher capacity cells (with same or better discharge rating)?
Battery percentage indicator would of course be wrong but as far as I know, most of the BMS protection functions rely on voltage measurements, not the percentage estimates.
Has anyone here attempted something like this? Just looking for some insight before I buy 200 dollars worth of cells.
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The battery percentage indicator is probably just voltage based. so it won’t be affected much unless the discharge curve of the new cells is dramatically different. with most lion chemistries that’s not a big difference. (except lifepo4) and yeah the BMS most likely doesn’t care/know if the total capacity changes… they are usually voltage based.
If you have the skills it’s probably doable. but from this reddit thread, (2yo) it looks like it’s a tight little pack. with folded nickle series connections.
If you’ve never done a battery build before it might be best to get someone who has to help you.
for posterity, from redit thread:
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I actually took the pack apart myself and took some measurements, I’m confident I can cram 21700s in there with a bit of modification
I’m pretty sure this BMS is coulomb counting, it shows me exact capacity left, and I guess what I’m concerned about is, if the coulomb counter says the original 6000mAH is depleted, but the voltage says there is still capacity left, will the BMS limit output as a result of the coulomb counter and make the new higher capacity unusable?
And another question…on BMS units without a coulomb counter, wouldn’t the percentage change constantly with voltage sag or regen?
I see. if it’s fancy and doing columb counting. idk what it might do. it could learn the state of charge over a few cycles, or it could have a fixed value.
I doubt it’s coloumb counting. but I’m guessing.
and yeah voltage sag can show on a voltage based capacity gauges. but depending on the current draw and capabilities of the pack, it’s not always super obvious.
