Battery Misbehavior

I have Presario 1210CA which originally came With Win95, I have installed WinXP with no problems. I had a battery problem when I was using Win95, therefore I opted for WinXP which didn't help. Battery is not charging fully. I tried charging after fully draining the battery in safe mode but it stops charging after 20%. I tried updated the Battery Controller patch from Compaq website but didn't helped much just charging somewhat faster then before. When battery stops charging I pulls the Power plug and reinserts it, then it shows blinking arrow towards battery and after some time it reaches next mark of 30%, it do it till it goes to 100%. But when I uses my notebook on battery system goes to standby on just 70% and when I insert the power plug it starts charging from 0% again. My notebook supports APM but i couldn't find APM in device manager under System Devices. I also tried reinstalling WinXP but couldn't find APM again under System Devices, please help. Battery is NiMH type.