all depends what you charged it at?. You need to condition the battery 1st thats a 24 hour charge at a 1/10 of a amp them get to to 1 amp.. or the battery wont last as long as it could... Yes its common for a newly charged Nixx battery to get hot warm. never leave any battery unattended..
If your charging it up at 1A, they do tend to get pretty warm at the end of the charge. Even at .5A, they get pretty warm, but 1A seems to heat them up more.