It may get a little warmer, but it probably isn't material.
The battery assembly is not exactly tiny, it is a 4.5AH NiMh pack, and it weighs over 2 pounds! Neither the thermal mass, or the surface is small. Only about 20% of the energy being used to charge appears as heat, so the assembly needs to get rid of about another 1.5 watts (total goes up to about 6 watts from 4.5 watts) if it charges at 2 amps instead of 1.5, so it is going to get warmer (maybe 10 degrees F), but that is about all. Even at 2 amps, going into a 4.5AH battery it is still 2+ hours for a full charge, so it is hardly a super fast charge. (not like 8 amps into a 2.5ah AA cell)..