> You can be pretty liberal about cells in parallel, it's series that bites you. Yeah but at least the BMS he uses does balancing to (hopefully) keep the serie

> You can be pretty liberal about cells in parallel, it's series that bites you. Yeah but at least the BMS he uses does balancing to (hopefully) keep the series packs from going into dangerous voltage territory. A dodgy cell in a parallel pack however, there's no way a standard BMS can detect that, hence pre-install measuring and matching... of course you can go for individual cell protection as well or buy cells with built-in protection but the former is overcomplicated (and hard to get right) for a DIY project, and the latter not an option as the cells from vapes don't have a need for protection circuitry. Hence, matching is a must. > He's using a 5s arrangement, it looks like - so his 100w fast charging will only be around 5-6A, not 30A, which those wires will probably be OK with (though i would have picked something thicker myself) Fair point, but still, that's not looking remotely near the 0.5 mm² that one should use for 5-6 amps of current.