NiMH handles gentle overcharging gracefully. They generate a little bit of hydrogen, and the battery has an internal catalyst to convert it back. It can do th

NiMH handles gentle overcharging gracefully. They generate a little bit of hydrogen, and the battery has an internal catalyst to convert it back. It can do that indefinitely as long as it's at a low rate. When aggressively overcharged they may rupture, but they don't go up in flames like Li-ion does.