ThinkBook 15 G3 ACL Not Charging Battery - LA-K602P Board

[kodox]

since i couldn't find schematic or boardview for this model (LA-K062P), i use closest board model found here https://www.badcaps.net/forum/troubl...-and-boardview

the schematic share same marking for each component, using same PD-Controller, same BQ25710, the only different is the battery cell used. LA-K061P uses 3S battery while LA-K062P use 4S battery per schematic.
what i've done:
- flashing the bios
- replace battery with new one
- replace bq25710 and all related mosfet to it
but nothing changed, new battery will drain even with charger pluged-in.

some weird symptom:
with battery unplug:
- sytem not turning on
- voltage on PLB1 around 4.5-6v
- voltage on PUB1 pins:
- pin 1, 2 & 3 -> 20v
- pin 4 -> 0v
- pin 18 -> 4 - 4.2v
- pin 22 -> 0v
- pin 28 -> 6v

with battery attached
- sytem can turned on
- voltage on PLB1 is 20v
- voltage on PUB1 pins:
- pin 1, 2 & 3 -> 20v
- pin 4 -> 3.2v
- pin 18 -> 4 - 4.2v
- pin 22 -> same with batery voltage
- pin 28 -> 6v

after inspecting schematic & tracing pin 8 of PUB1, found what i think it's a PRB23, removed from the circuit and it measure exactly the same value as LA-K061P schematic (43.2K) and doing calculation of this divider it's a same value as i measured earlier on PUB1 at pin 18 and it said for 4S battery while the unit i worked using 3S battery. the owner said it started about a month ago, he realized that the battery not charging when pluged in charger and sometime the laptop turned off by itself. that's make me wonder why it can charge the battery before while those divider are meant for 4S battery?

anyone could point where to look? i attached picture from another thinkbook schematic using same bq chip and 3S battery

[mon2]

What is the voltage marked on the battery?

What is the voltage to ground of the battery at the battery connector?

Review the VCC power pin on this BQ charger IC. Often there will be a dual common cathode diode used to power the charger IC. Test that this part is not defective.

[kodox]

voltage marked on the battery: 11.1V (Nominal) & 13.3V (Max. Charge Voltage)

voltage at the battery connector: 12.5V (first time testing after replacing BQ IC & mosfets) & 11.8V (before start posting)

on datasheet there were no pin marked as VCC in this BQ sir

[mon2]

- pin 22 -> 0v

This means the power adapter voltage is not reaching the main power rail of +16.8VB. Without a battery, the charger IC should regulate the input voltage of 20V to a lower safe voltage to power the logic board. Same reason as to why the battery is not charging.

Have the mosfets @ PQB1 & PQB2 been replaced?

Pin #4 (CHRG_OK) is an open-drain signal that is being parked to the logic '1' = OK by REGN voltage (which is ok). Only if the charger voltage is NOT ok, then the charger IC will pull-this line LOW. When using only the adapter, Pin #4 is LOW so this needs to be investigated.

Is the power adapter the original power adapter and suitable to power this logic board?

[kodox]

the unit i worked on use 3S battery, i think it should have 12.6V on main power rail sir, the schematic on first post it's LA-K061P and it uses 4S battery that's why it 's written as +16.8VB on main power rail

on the first post i wrote "replace bq25710 and all related mosfet to it"

at first plug power adapter pin #4 (CHRG_OK) has 3.2V but after 1-2 second it pulled low (0V), measure resistance to gnd (without any power applied to the board) it's on range between 20-30 kilo ohm, even i tried removing capacitor C255 near UEC1 it still pulled low after 1-2 seconds

i tried all type of power adapter that has type-c connector that known good on other board but the result still same, last step i tried injecting 20V on VIN_MUX rail and the result remain the same again

[kodox]

found the culprit!!!
it was replacement mosfet for PQB2, at first i'm using QA3118 mosfet assuming it has a bigger "ID" based on datasheet, after replacing it twice without resulting any progress i ordered same part number that came with the board.
upon arrival immediatelly changed the QA3118 and voila, the board came alive even without battery attached & would charge the battery from 0% to 100% without issue (except for heat).

hope this help someone with same case

[mon2]

Good that you have it working.

What is the original part number of that was onboard? A higher rated valid replacement part should also have worked but will run cooler.

[kodox]

original mosfet is using AONY36354, yes i thought so, higher rated mosfet should do the job without issue. but not in my case and i don't know why, it drive me nutz for almost a month so wrapped it up as soon as the unit working, thank's all for help