My Dell Inspiron stopped charging battery some months ago. BIOS stated that the power adapter could not be found. Still, the machine was powered by the mains, but not charging battery. I ordered me a new power adapter from ebay, arrived today, but machine still not charging.
I googled, and a Dell support article recommended updating BIOS. Still nothing. Googled some more and found this:
Seems to be a communication problem between the charger and the mother board. The communication goes over the thin middle pin inside the power jack.
I disassembled the computer, taking out the power jack board. Ohmed between the middle pin, and the contact going to the mother board. No contact with any pins. Re-soldered the middle pin of power jack. Ohmed again, with contact between power jack middle pin and the connector. Reassembled. Battery charging again!
You could also buy new power jack boards on ebay: http://search.ebay.com/dell-inspiron-1525-power-jack-board