Lenovo ThinkPad 770 Hardware Maintenance Manual for 770 series notebooks(Janua - Page 44

Checking the Backup Battery, Power off the computer and unplug the AC Adapter

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CHECKOUT GUIDE Note In this case, the battery pack is over-discharged. It takes at least 3 hours to recharge the battery pack even if the indicator does not turn on. 4. If the voltage is still less than +11.0 V dc after recharging, replace the battery. 5. If the voltage is more than +11.0 V dc, measure the resistance between battery terminals 3 and 4. The resistance must be 4 to 30 K ohm. 6. If the resistance is not correct, replace the battery pack. If the resistance is correct, replace the system board. Checking the Backup Battery: Do the following: 1. Power off the computer and unplug the AC Adapter from the computer. 2. Turn the computer upside down. 3. Remove the backup battery (see "Removal and Replacement" section of each model). 4. Measure the voltage of the backup battery. See the following figure. Note Be careful not to measure the wrong side of the backup battery. Wire Red Black Voltage (V dc) +2.5 to +3.2 Ground If the voltage is correct, replace the system board. If the voltage is not correct, replace the backup battery. If the backup battery discharges quickly after replacement, replace the system board. 38

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CHECKOUT GUIDE
Note
In this case, the battery pack is over-discharged.
It takes at least 3 hours to recharge the battery
pack even if the indicator does not turn on.
4.
If the voltage is still less than
+
11.0 V dc after
recharging, replace the battery.
5.
If the voltage is more than
+
11.0 V dc, measure the
resistance between battery terminals 3 and 4.
The
resistance must be 4 to 30 K ohm.
6.
If the resistance is not correct, replace the battery
pack.
If the resistance is correct, replace the system
board.
Checking the Backup Battery:
Do the following:
1.
Power off the computer and unplug the AC Adapter
from the computer.
2.
Turn the computer upside down.
3.
Remove the backup battery (see “Removal and
Replacement” section of each model).
4.
Measure the voltage of the backup battery.
See the
following figure.
Note
Be careful not to measure the wrong side of the
backup battery.
±
If the voltage is correct, replace the system board.
±
If the voltage is not correct, replace the backup
battery.
±
If the backup battery discharges quickly after
replacement, replace the system board.
Wire
Voltage (V dc)
Red
+
2.5 to
+
3.2
Black
Ground
38