Legion 5 15ACH6H not charging

[trepachka]

Perhaps, someone could provide insight regarding the issue I am having with a Legion 5 15ACH6H laptop (Ryzen 7 5800H / RTX 3060)

The laptop came in with a blown charging ic BQ24780S. Pin 1,2,3 pads were ripped out. Also, the current sensing resistor on Pin 28 was showing over 200 ohms. I restored the damaged pads, replaced the ic chip and the current sensing resistor.
Computer is working but only on AC adapter or on the battery but not when they are both plugged. The AC adapter gets cut off and the machine runs on the battery alone. Interesting that in Windows the battery charge percentage always remains 100% no matter what and when asked to provide the details on the battery condition, the system reports the battery has only 50% of its original capability. I tried the battery in another computer and the battery percentage showed something like 18% and almost 97% of its remaining capacity which is correct. I tried another battery with the same results.

I replaced the EC chip, BQ chip and all battery side mosfets just in case without any change. I am looking for assistance. Thanks

[mon2]

Test the voltage on the SMBUS / I2C lines on the BQ24780S. The BMS uses these lines to offer the battery details and the 100% charge status is often linked to issues with these lines.

[trepachka]

Where do I test the voltage? On the BQ chip side or EC chip?

[mon2]

SMBUS / I2C lines on the BQ24780S

These same lines are available on the battery pack connector. Test each line on the battery connector. If you wish, you can even test in resistance mode. Disconnect the battery; disconnect the power adapter and use resistance mode to ground. Specifically, testing if the SCL/SDA lines are shorted or not. If not shorted, then power up and test the voltage to ground of the same SCL/SDA lines. If shorted, the local ESD diodes are suspects and should be fluxed and removed. Then test again.

[trepachka]

Both EC_SMCA (pin 5) and EC_SMDA (pin 6) measure 400K resistance. Whether on the charger alone or battery, both pins are showing steady 3.2V

[mon2]

Test the resistance from the battery connector to the actual charger ic for the same sda and scl lines. Post their measurements. Not at my desk but perhaps there are series resistors in their path. If there are voltage level shifters in series then a different game.

[trepachka]

I get 100 ohms from the battery connector to the charger ic on both pins. Based on the schematics, there is a 100 oms resistor connecting 2 points. Both pins have 3.2 V.

I get orange charging light but the battery is not being charged.

[mon2]

Are you confident that the battery is suitable for this motherboard? Suggest to test another known good battery unless your other test board is 100% the same model.

[mon2]

Also review the dual diode that is often present on the VCC pin of the BQ24780S. Confirm this dual diode is not defective.

[trepachka]

Sorry, I was out of town and was unable to get back to you. The dual diode appears to be fine. It gets both the AC and battery voltage. The AC voltage of 20V flows out. When on battery only, it passes battery voltage as well. I tried a different battery with the same result. I have another similar model. It charges both batteries with no issues.

Should I try reflashing the bios, perhaps?