Lenovo ThinkPad 770X Hardware Maintenance Manual for 770 series notebooks(Janu - 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