Lenovo - M491 – Disassembling procedure – How to test the battery pack - How to test the charger – How to remove the bottom case

Lenovo M491

Power system checkout
To verify a power symptom, do the following:
1. Turn off the computer.
2. Remove the battery pack.
3. Connect the ac power adapter.
4. Check that power is supplied when you turn on the computer.
5. Turn off the computer.
6. Disconnect the ac power adapter and install the charged battery pack.
7. Check that the battery pack supplies power when you turn on the computer.
If you suspect a power problem, refer to the following topics for a checkout:
“Checking the ac power adapter”
“Checking operational charging”
“Checking the battery pack”
Checking the ac power adapter
If the computer fails only when the ac power adapter is used, refer to the information in this topic to check the ac power adapter.
If the power-on indicator does not turn on, check the power cord of the ac power adapter for correct continuity and installation.
To check the ac power adapter, do the following:
1. Unplug the ac power adapter cable from the computer.
2. Measure the output voltage across the plug of the ac power adapter cable. The correct voltages are shown in the following table

Note: The output voltage across pin 2 might differ from the voltage that you measure.

3. Depending on the voltage that you measure, do one of the following:
If the voltage is not correct, replace the ac power adapter

If the voltage is acceptable, do the following:
a. Replace the system board.
Note: Noise from the ac power adapter does not always indicate a defect.
Checking operational charging To check whether the battery pack charges properly during operation, do the following:
Note: Before you begin, install a discharged battery pack or a battery pack that has less than 50% of the total power remaining in the computer.
1. If the battery status indicator does not turn on, remove the battery pack and let it return to room temperature.
2. Reinstall the battery pack.
3. If the indicator still does not turn on, replace the battery pack.
Checking the battery pack
To check detailed battery status information on the operating systems, do the following:
7: Launch the Power Manager program and click the Battery tab.
8: Do one of the following:
Click Start > Solution Center > System > Battery.
Launch the Settings program from the Start screen, and then click Power.
To check the battery pack, do the following:
1. Turn off the computer and disconnect the ac power adapter.
2. Remove the battery pack and measure the voltage between battery terminals 1 (+) and 7 (-). The correct voltages are shown in the following table.

3. Measure the resistance between battery terminals 5 and 7. The resistance should be 4 to 30 KΩ. If the resistance is not correct, replace the battery pack.

4. Depending on the voltage that you measure, do one of the following:
If the voltage is less than +12.0 V dc, recharge the battery pack. If the voltage still is less than +12.0 V dc after recharging, replace the battery pack.

If the voltage is more than +12.0 V dc, discharge the battery pack until the voltage becomes less than +12.0 V dc and then recharge the battery pack. If the voltage still is less than +12.0 V dc after recharging, replace the battery pack.
Note: Recharging will take at least three hours, even if the battery status indicator does not turn on.
5. Replace the system board if the new battery pack is not charged.

DISASSEMBLING PROCEDURE 

How to remove Battery pack

Unlock the battery lock 1. Hold the battery latch in the unlocked position, and then remove the battery pack 2.

How to remove Bottom slot cover

Remove the screws 1, and then remove the bottom slot cover 2.

How to remove Base cover

Remove the screws 1 and 2.

Remove the base cover.