Client: Hey, my batteries overheated and now the wireless mouse doesn't work.
Me (takes a look at it): Did you put the batteries in the right way?
Client: Of course
Me: that's very odd, I've never known batteries these days to overheat if used properly.
Client: ya, it was weird. I took it out of the charger and it was melted
Me: Were you using rechargeable batteries?
Client: Do you have to?