Checking The Backup Battery - Lenovo ThinkPad T400 Hardware Maintenance Manual

Checking the backup battery

Do the following:
1. Power off the computer, and unplug the ac adapter from it.
2. Turn the computer upside down.
3. Remove the battery pack (see "1010 Battery pack" on page 84).
4. Remove the backup battery (see "1060 Backup battery" on page 92).
5. Measure the voltage of the backup battery. See the following figure.
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
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ThinkPad T400 and R400 Hardware Maintenance Manual
Red (+)
Black (-)
board.
Wire Voltage (V dc)
Red +2.5 to +3.2
Black Ground