[TKO-Wildcard]

I just recently received a M4 today and I was testing it out with a Sanyo NiCad 9.6v 1400 mah nunchuck battery. Heres the problem: I plugged the battery in and fired one shot and left the battery for five minutes still connected. I came back and realized that the battery is extremely hot, and I completely disconnect it. This being 20 minutes ago from when this post goes up, the battery is still extremely warm. I remember a similar incident last year where I fired an M4 with a different nunchuck battery and left it for 30 minutes on a table. In the previoud incided the other battery had melted the wrapping around the battery and seemed to be leaking out some sort of liquid. Seeing how this has happened on 2 seperate and completely independant cases, I'm wondering if I'm doing something wrong with the batteries.