Hey everyone, I'm dealing with some 12Ah battery packs that are starting to have dead or unbalanced cells. I've come across some posts suggesting that when rebuilding these packs, I need to replace the battery management system (BMS) because it supposedly won't work post-rebuild. Is this true? Also, do the BMS units vary between different capacities, like from 5Ah to 12Ah? Any insights would be appreciated!
4 Answers
I think you meant BMS (Battery Management System)? It's usually embedded in the circuit board. Technically, it doesn’t need to be replaced unless it’s causing issues. Balancing the cells might solve your imbalance problem, and you can do that with the right tools. But be warned, I’ve rebuilt a few batteries, and the BMS often doesn’t manage cell balancing at all, even though it’s supposed to. So keep that in mind!
Yeah, Milwaukee used to offer rebuild services for $115 if the pack is out of warranty. If you're doing it yourself, factor in the costs for new cells and you’ll need a spot welder along with some skills. It’s tough when batteries fail, and I learned that the hard way by draining mine too deeply while using it inappropriately.
I'm not exactly sure what a BMC is, but my uncle has been rebuilding battery packs as a hobby for about four years now. He usually just replaces all the cells instead of just the dead ones since the others tend to fail soon after. He prefers using Samsung cells for better durability. As for the BMS, I haven’t seen him replace that part, and the packs seem to function fine after refreshing the cells.