HP Pavilion Power 15-cb G75A can't work on battery

[sopik78]

Hello,
I have an interesting issue with an HP Pavilion Power 15-cb011nc laptop. The laptop works perfectly fine with the AC adapter connected, charges the battery correctly to 100%, but when the power adapter is disconnected in Windows, it shuts down immediately. When trying to power it on using only the battery, it only shows the "HP" logo, and as soon as it starts booting the operating system, it shuts down immediately. However, the voltage on +VIN is stable and holds at approximately 17V, which means the MOSFET controlling the battery power is correctly open and supplying the main power rail.
The laptop came to me with a damaged DC-in connector; the center pin was broken. However, it was still charging. I have already replaced the DC-in connector.
The charging circuit uses a BQ738 controller, which appears to be working correctly.

I performed measurements with an oscilloscope, and when the shutdown occurs, there is no voltage spike on the main power rail; only a very slight drop in battery voltage is visible during the boot attempt. The SDA_CLK and DAT_CLK signals also show the expected behavior.

This simply doesn't make any sense to me.


Motherboard: G75A, DAG75AMBAD0, rev D

[mon2]

Have you tested with another known good battery?

[sopik78]

I don't have another battery available, and I have no way to test it elsewhere. However, it appears to be fine; the voltage is stable, and it charges correctly

[sopik78]

The problem has been resolved. The root cause was identified as a faulty Keyboard Controller (KBC), specifically the IT8987E chip. Following its replacement, the notebook now operates correctly on both AC power and battery power.