Dual Cell is being weird

[Zephyranthes]

I almost lost my car today. I've been having problems with my dual celler. I was charging it on my controller conversion and the inner battery started hissing so I took it out as fast as possible afraid it would explode. The 2nd battery wasn't warm at all. They are connected in series. What's wrong with the battery?

[funkymonkey]

What voltage you charging the cells with?

Also, is one cell less capacity than the other?

[Zephyranthes]

I was charging on 3v. Both batteries were the same. I was using the Tomy ones.

[dabigpig]

i had a single cell compleatly stock car make hissing poping crackeling sounds after i changed the batterys in my controler so i bought 2 kit racers and am in the process of doing a dual cell mod