Depends on how fast you were charging it. If it was a "fast charge" ie. 2C or more then it should get hot. If you were "trickle charging" your battery at 0.5C then it shouldn't get too hot.
Basically the more amperage you're pushing to the battery the hotter it should get. Don't charge at too high of an amperage or you can damage the battery.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE