Acer 4752G (10267-4) Laptop Not Charging Repair

 Laptop Model: Acer 4752G

 

Board Number: 10267-4

 

Fault: It can be turned on and used normally with the power supply or battery, but the battery is not recognized and cannot be charged, the charging light does not light up, and the battery is not detected when entering the system.

Maintenance Process:

 Open the drawing, find the battery identification signal BAT_IN#, plug in the battery and measure 2.4V, which is obviously wrong and normal is 0V.

Then find the problem, BAT_IN# is connected to 4 places, pull-up resistor, EC, resistor, and Zener diode. First, I measured the resistance of PRN3901 to be 33 ohms. I found the pull-up resistor and measured it online to be 3.3K. I thought the resistance had become smaller and replaced it with a new 100K resistor, but the result was still the same.

 

　　Then directly remove the pull-up resistor and then measure BAT_IN#, and there is still a voltage of 2.4V. If you think about it carefully, it may be a problem with the exclusion resistor. The BAT_SCL and BAT_SDA connected to the exclusion resistor have 3.3V. After removing the exclusion resistor, the voltage is gone.

Install three 33 ohm resistors and measure the voltage on BAT_IN#, which is normal.

Then I installed the 100K pull-up resistor, but BAT_IN# has voltage again, which is very strange! The voltage comes from the pull-up resistor.

 

Change the pull-up resistor to 300K and BAT_IN# becomes 0.14V. Then change the resistor to 1M. The result is BAT_IN# is 0.05V. Plug in the battery and it can be charged. Install and test everything. All normal.

Happy Repairing !