IBM ThinkPad 340 Series Hardware Maintenance Manual page 85

Checking the Backup Battery
1. Carefully place the computer bottom-side up.
2. Remove the bottom cover.
3. Disconnect the battery connector from the system
board.
4. Measure the voltage of the backup battery. See the
following figure.
(Black)
Wire
Red
Black
If the voltage is correct, replace the system board.
If the voltage is not correct, the backup battery has
been discharged by a short circuit or it is defective.
Checking the Standby Battery
Note: Make sure that the battery pack is removed
from the computer before the standby battery
is removed.
1. Power-off the computer and unplug the AC adapter
cable from the computer.
2. Remove the battery pack.
3. Remove the indicator cover.
4. Disconnect the standby battery connector from the
voltage converter.
5. Plug the AC adapter cable into the computer and
power-on the computer.
6. Measure the output voltage at the connector on the
voltage converter. See the following figure.
ThinkPad 700, 700C, 720, 720C (9552)
(Red)
Voltage (V dc)
+2.5 to +3.7
Ground
75