Ok sorry if this is a long post I just want to include all of the information. I have had about 5 batteries since I got my rc truck and they all suffered similar fates. It all started about 4-5 years ago when I got an exceed rc infinitive brushless truck for my birthday. It worked fine at first, but battery life was short. It came with a 8.4V 3000mAh NiMh battery. (Note: all batteries I had were 7 cell NiMh batteries) I went out and got a second battery, this one being an 8.4 volt 5000mAh NiMh Onyx battery. About this time I was also given a Traxxas ez peak charger and swapped from the original connectors to Traxxas connectors. They onyx battery lasted a few charges/discharges and then didn’t work at its normal power. I felt the battery afterwards and some of the cells were hot while others were cold/room temp instead the entire battery being warm. Needless to say, I took it back and exchanged it for an 8.4V 5000mAh Venom battery, which then suffered the exact same fate. I took that one back and exchanged it again for the same battery except this one worked. After a couple times of me using it, I took it outside in the middle of winter to mess around in the snow, and the battery suffered the same fate, where some of the cells stayed cold and other got hot, except this time the ones that got hot got so damn hot the plastic around some of the cells melted, while some of the other cells stayed normal temp. I take that battery out, and put in the one that came with the car from the factory, because that battery has lasted forever, AND IT DOES THE EXACT SAME THING AS THE VENOM BATTERY BEFORE IT. So now I don’t have a single battery and I’m trying to figure out what the hell is going on. I am pretty good at the mechanical stuff, but when it comes to the electrical stuff I am just a dumpster fire. I know it’s probably user error so don’t bash me for it just please tell me what I’m doing right/wrong and/or how to fix it. Thanks it advance.
PS. I would include picture but apparently I need 10 posts so if there is a work around for that lmk. Thanks

The mechanical stuff seems to be fine, but how would I check the electrical stuff like the esc?

So I went into a local hobby store and the guy there said that my speed controller was draining my battery too fast/too much, and that I would probably need a new speed controller. Does this sound right to you, and is there a way to test this too? I’m sorry for asking a bunch, but when it comes to electronics I know next to nothing.

So I tested my speed controller with a multimeter and it was only running about 8-10 amps full throttle, so I went back and to him the speed controller wasn’t the problem, what else could I be. He looked at my rc car and without hesitation said that the whole system was originally meant to run more power than what the battery could provide. It originally came with that NiMh battery but it also came from an off brand website and was really cheap, so I’m guessing the battery it had was dirt cheap just like he truck. Anyway, I decided to try out a venom 2S lipo. All I had to do was change the settings on my esc so it had a cut-off and away I went. After the first run, it was all good. The battery wasn’t at all hot and the truck now has a lot of power. You wouldn’t think that the difference between an 8.4v NiMh and a 7.4v lipo would be that much but this heavy 4x4 truck now does wheelies like it’s nothing. It’s almost as if the truck was meant to run a lipo the whole time. (I did have to heavily modify the battery holder though). There’s no heat issues while charging or discharging, and power is continuous. I’ve probably drove it 4-5 times already and there’s no problems whatsoever. This lipo battery (so far) has lasted longer than the NiMh batteries.