ThinkPad Computer Hardware Maintenance Manual

4. Remove the backup battery (see “Checking the battery
pack” on page 38).
5. Measure the voltage of the backup battery. See the
following figure.
Red (+)
Black (-)
Wire Voltage (V dc)
Red +2.5 to +3.2
Black Ground
v If the voltage is correct, replace the system board.
v If the voltage is not correct, replace the backup battery.
v If the backup battery discharges quickly after
replacement, replace the system board.
Checkout guide
40 R50/R50p, R51 Series