I have a ton of these things, and they are all bad. I’ve opened at least 20 and tried about anything one can imagine, and am usually good at finding a battery fix except for these and Ridgid batteries. I’ve come across a few different issues, sometimes it is the temperature sticker that kills the circuit, sometimes the sole capacitor is blown, sometimes it is just one of the rectifying capacitors, or sometimes there is no apparent flaw in the battery. I’ve tried giving it a boost, I’ve tried balancing the cells, and the only thing I’ve done that works is bootlegging the negative out past the firmware and soldering it to the last cell in the parallel (2) 20v batteries. The major catch is while it will charge, and discharge, it will catch fire because it doesn’t know when to stop taking a charge, you have to charge for no more than 30 min, and let it rest for 30 min. Not a real fix. Similar to Ridgid batteries, except you can get lucky and solder the bad and good rectifiers together to complete the circuit on a Ridgid without issue and it continue to work as it should. But with the 40v, just throwing bad signals out constantly. Anyone have a clue or recommendation on what I might be overlooking?