Acer Nitro 5 AN515-55 - Undetected Battery + Crashing under heavier load

[Rimeyrep]

Acer Nitro 5 AN515-55
Board: Compal LA-J891P rev.1.0B

Crashing under heavier load
Battery not detected
Working only with AC adapter plugged in

What happened:
Notebook crashed under load randomly. After several crashes throughout the week (after each crash it got worse and worse meaning crashes were happening more often) i found out it works just fine not plugged in AC charger only powered by battery so i was using it that way until battery was drained to 5%. When i plugged AC charger in battery wasn't charging so i restarted the machine hoping it will fix itself by some miracle . After turning it back on with my AC charger plugged in it windows showed "no battery detected/installed" down in system tray.

Next step: I sent laptop to Acer service centre (it was already out of warranty) hoping the quote for repair will be acceptable. They couldn't figure it out tried changing the battery but to no success and sent it back to me.

Having some experience with repair and moderate experience in soldering SMDs i disassembled it and found blown/fried MLCC caps PCZ39 and PCZ67 under PUZ2 circuit (mosfet driver NCP81151MNTBG). I replaced damaged caps with same specs ones and repaired damaged trace tested with multimeter for shorts around repaired trace and soldered caps if i didn't messed up and everithing was fine. I reassembled it and tried powering it on but all the issues mentioned above persisted. I tought that maybe those caps were just badly soldered and for a long time they were piece by piece losing contact with board but it seems it propably wasn't the case.

I have attached photos of fried caps and some schematics of mentioned components.

If someone have any ideas what to check next, what to measure ill be grateful i have access to my schools equipment in my spare time, things like multimeters, oscilloscopes, microscopes, PSUs, thermal cameras etc., also feel free to correct me if im wrong somewhere. I have boardview and full schematic of board, i can attach it if needed. (wasnt really sure if it is allowed )

Thanks for help!

[Stevedb]

Re: Acer Nitro 5 AN515-55 - Undetected Battery + Crashing under heavier load

Hi I would first check the first and second dcin mosfet for internal short. Probabably first mosfet is shorted. It is very common with acer nitro laptops.

[ktmmotocross]

Re: Acer Nitro 5 AN515-55 - Undetected Battery + Crashing under heavier load

Hi I would first check the first and second dcin mosfet for internal short. Probabably first mosfet is shorted. It is very common with acer nitro laptops.

offcourse it is common when u have short on VIN rail. Does not matter model or manufacturer

[Rimeyrep]

Re: Acer Nitro 5 AN515-55 - Undetected Battery + Crashing under heavier load

Hi so i finally found time to look at it. Thanks for the answers .
Yes, first DCIN mosfet was shot. I ordered new one, changed it, tried powering notebook on and sucsess, it worked.

Notebook is working correctly under heavy load and no longer turns off after few seconds.
Battery is no longer undetected battery light shines red BUT when i turned it on battery was showing 100% charge which is not correct because i remembered that i discharged it till 0% last time notebook was working. I peeled the foil on battery to measure it directly on the cells if they are fine. I measured around 2.8v on each of four cells so discharged for sure, but not dead. I tried to check if connector is good because it seemed little bit loose to me. GND wasn't making proper contact so i repaired it and tried again.
Turned it on again battery was showing 0% and battery indicator in windows was showing battery was charging BUT again after around 10s it stopped charging and just showed 0% and plugged in. Tried reinstalling battery drivers didn't help, tried plugging it unplugging and no succsess. I tried to measure battery on the cells and it was around 3.7v on cells so it was charging but not showing charging which is weird to me. I tried turning the laptop on, plugged in and i measured on the cells again and cells voltage was slowly creeping up so it was charging but again in windows it was showing 0% and just plugged in. I tried to let it just sit and "charge" for a bit but after about 15minutes notebook crashed restarted and showed no battery detected again in windows. Afterd plugging and unplugging battery and restart it is doing same thing again as before - so charging on the cells but in windows 0% no charging.

Is it possible the BQ charging IC is faulty or just battery is shot ? Do you guys have any idea what to check or some experience with this behaviour ?
Thanks

[Roman123]

Re: Acer Nitro 5 AN515-55 - Undetected Battery + Crashing under heavier load

With this behavior, the battery died by 95 percent. It is the batteries themselves. The EC communicates with the battery controller and tries to charge, but cannot do so and the battery controller turns off the charge. BQ has nothing to do with it.

[mon2]

Re: Acer Nitro 5 AN515-55 - Undetected Battery + Crashing under heavier load

Measure the voltage to ground of each pin on the battery contact - with the battery connected.

It is possible that the SMBUS (SDA / SCL) lines used to communicate with the battery management system (BMS) is defective from an ESD event. This check is to confirm the SDA / SCL lines are not stuck.

[Roman123]

Re: Acer Nitro 5 AN515-55 - Undetected Battery + Crashing under heavier load

If you have an oscilloscope, you can view the exchange on the SMBUS bus

[Roman123]

Re: Acer Nitro 5 AN515-55 - Undetected Battery + Crashing under heavier load

If it is possible to take the battery, you can try to replace it, this is the easiest.

[Rimeyrep]

Re: Acer Nitro 5 AN515-55 - Undetected Battery + Crashing under heavier load

So after a while i got to this again. Just writing to conclude this story

I measured SDA / SCL on battery connector when plugged it showed nothing. I found fitting used battery on local site simmilar to ebay so i just bought it. It came in about two weeks i plugged it in and it is working without and issue.

So the battery was dead possibly from faulty connector which wasnt making proper contact to GND or some ESD event as mentioned above.

I was using notebook for about a week without issue when it died again when playing games. No charge no power nothing. Opened it up - main power rail shorted insane. I was about to inject some low voltage to find a short with thermal camera when i saw a dodgy looking cap next to the caps i repaired (in first post). So i just unsoldered it and short was gone . Replaced it, also ofc first DCIN mosfet was destroyed again by the short so thanks god minimum order quantity was 5pcs .

Laptop is working again without issues. If another cap from this area (there are 4 rows of 3 caps next to each other) goes i will replace all of them as a precaution.

Thanks all for help.