charging problem

My Ipaq 3950 seems to have a problem with the battery. When I put it in th
craddle on connect it to the mains it does not recharge although the main
battery power stays constant at a certain % (about 28%). Furthemore when I
connect it to the craddle it thinks like it is running on battery power
(back light directly stops).
If I connect my CF expansion pack with external battery to the 3950, the
external battery starts to recharge (looking at the orange flashing light at
the back) but this is not indicated in the battery settings software.
Who has an idea what is going on? (battery broken? charging print broken?)

thanks
William