Note: Recharging will take at least 3 hours, even if the
indicator does not turn on.
If the voltage is still less than +11.0 V dc after
recharging, replace the battery.
4. If the voltage is more than +11.0 V dc, measure the
resistance between battery terminals 4 and 5. The
resistance must be 4 to 30 K .
If the resistance is not correct, replace the battery
pack. If the resistance is correct, replace the system
Checking the backup battery
Do the following:
1. Power off the computer, and unplug the ac adapter
2. Turn the computer upside down.
3. Remove the battery pack (see "1010 Battery pack" on
4. Remove the backup battery (see "Checking the battery
pack" on page 35).
5. Measure the voltage of the backup battery. See the
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.
ThinkPad T20, T21, T22, T23 (MT 2647/2648)
Voltage (V dc)
+2.5 to +3.2