I have about 10 of these power tool battery packs that wont charge. I think if i pull out dead cells, swap some around and balance the working ones i can get some of them working. They are all out of warranty.
The battery cells are welded to a bus bar. I’m not even sure i can solder the cells back on. What i want to do is make it so i can easily swap the cells around in the packs.
I’m imagining 3d printing a box that fits around the existing pack/controller/tool connection with springs to make the connection to each cell and wires to the control board.
Does this already exist? Is it a terrible idea? Get some callipers, learn CAD and get going? Is there anyone interested in making this? i imagine people might buy it?
I’ve found it possible to cut the old welded tabs off with a utility knife cutting through the weld, but I don’t recommend it because if it fails it could be nasty. Damaging to you and your surroundings. It’s not safe. I wore goggles and questioned my sanity while doing it. Then it turned out that none of then were particularly strong, even though some were better than others.
You’ll get higher resistance through springs. The normal thing is to get a spot welder that’s designed for this sort of thing. You don’t want to solder; paradoxically, that will damage the battery more; welding may be higher temperature, but it’s lower heat. The total thermal energy of a tiny burst of current to melt the metal together at the surface is a lot lower than slowly heating a bunch of metal up to solder melting temperature. Soldering them could be hazardous to your health.