mcristiani wrote:I keep getting welds popping off and then batteries out of sync and then dead groups again. I just don't get it.
If welds break, then there are twisting stresses on the pack itself that are moving cells around.
You'll want to secure the cells together so they cannot move, and then secure the pack so it cannot twist, and then the welds won't break.
BTW, with really good welds, when they break it's possible for them to rip chunks out of the cell cans, and cause the cells to either leak electrolyte or admit air and moisture into the cell--either one is fatal for the cell, so any cells damaged that way need to be removed even if they electrically appear to still be working at that time (because they *will* fail later).