Quote Originally Posted by Vodka View Post
here's my experimental LFP 8-series 24v pack. BMS is a jbd 7-14s with bluetooth (costs less than P900)

the cell sizes that are commonly available are 26700 (26mm dia, 70mm length), 32700, and 32140. so you just have to figure out which one fits your size constraints. the 26700 and 32700 cells are approx 100 each. but i have to warn you that these generic unbranded re-wrapped cells are hit and miss, the capacity can vary greatly between cells, so you may have to buy a lot of them and then use only the good ones, which means you'll have to do capacity tests on every cell you might be better off buying pre-made LFP battery for motorcycles or something like that



Much appreciated.

I don't need too much capacity because the UPS is designed for 9Ah SLAs that has a 50% DoD limit, so any 24V LFP that has at least that much Ah capacity (that can be run down to 80% DoD) should be sufficient in the runtime department. What is more important is the pack should be able to handle the continuous 700VA discharge (which is roughly 30-40A * 24V nominal). Though the actual load is nowhere near that, I'd like to keep a little bit of headroom for safety.

I've looked at 24V LFP packs but they are still quite rare. Especially if I'm working on a size constraint so it will fit inside the UPS. And also the reason I am considering building one rather than buying a ready-made pack, is because I don't have any idea how these packs were made... how good the quality of the innards are.