which batteries are getting hot? the AA Duracells? Or the rechargable one on your bit? I have a 4 AA battery charger like the one in the pic and none of my Bits have suffered – or had warm batteries. I have 1, 2 and 3 cell bits. I had a couple of hot batteries cos the earth wire on the PCB was loose and that made my 2 celled bit’s batteries really HOT! In fact, I ruined the nicads and had to replace both of them.