IBM Thinkpad R51 reboots when on battery power

Ed Rhodes

Dec 25, 2014
My IBM Thinkpad R51 has a bizarre problem. As long as I keep it plugged in, it's fine. When I unplug it, the battery icon says 2 hours, but the computer runs for a few minutes and then reboots. The reboot shows the IBM Thinkpad screen, then the Windows XP screen but when it tries to boot the "Welcome" screen, I get a blue screen of death and the computer completely locks up. I have to push the power button to shut down, plug the computer in and start it up again.
Without further info, I'm thinking a few possibilities; 1) Primary battery is failing, 2) CMOS battery is failing, 3) Power distribution is failing (may be blown capacitor).
How old is the laptop?
How old is the primary battery?
Has the CMOS battery ever been changed?