Lenovo ThinkPad X41 Tablet MT 1866 Hardware Maintenance Manual page 47

5. Measure the voltage of the backup battery. See the
following figure.
Red (+)
Black (-)
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.
Wire Voltage (V dc)
Red +2.5 to +3.2
Black Ground
General descriptions
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