Charging the battery will warm it up. If it gets excessively hot, it may be faulty. The main cause of the heating is a high charge rate.If the pda uses Lithium batteries, it should be trickle charged to top it off. High capacity Nimh tend to warm up when charging and and some NiCad batteries do also. Most devices use a temperature sensor to determine when to switch from the fast charge rate to the trickle charge rate.