Asus FX505DY - Battery not charging - BQ24780S

[Iherduleikgemz]

Hello everyone

I have been working on this laptop mentioned in the title, it initially had a shorted capacitor. After I replaced it, the thing started working again, but there is still another problem. The laptop was running off a charger, the battery was reporting 96% charge... but when I unplugged the charger, the laptop died. I've measured the battery voltage - 0V. I think it is locked. (Screenshot from batterymon, below).

I've ordered a new 3rd-party battery, but I think there's something wrong with it too - the laptop boots, but the battery isn't charging. Also, batterymon reports 0 mAh capacity (screenshot below, currently nearly discharged). I have also replaced the BQ24780S charger from a donor board, and replaced PQ8903, PQH8901 and PQL8901 (original 4C09B) with M3054M, because I accidentally shorted them due to my stupidity...

On another screenshot attached below, are my measurements of BQ24780S with charger only, and with both charger and replacement battery present.
Weird thing though, the "battery charging" LED is orange with and without replacement battery present. With the original locked battery it's white. Pin 15 BATPRES# is always low - 0V.

Can anybody please look at all of this and point me where to go next?

By tomorrow I should have:
- used, working original battery
- new BQ24780S
- 3x 4C09B.

[mon2]

In my opinion, you have fake batteries. Some of the battery details are present but many are missing which is wrong. This confirms the smbus is working but the bms is not sharing the serial number and other details. Any chance you still have the original? Try that battery and compare the same screen with the battery details. The fields should be fully populated on the battery information.

[Iherduleikgemz]

The second screenshot of batterymon with 96% charge is with the original ASUS battery that the laptop came with. But as I said there is 0V present on its terminals. (The cells are 4.03V)

[mon2]

Which version of the board do you have?

Maybe 2.0 or 2.1?

Is the tool you are using known to be compatible with this laptop? Sometimes, the BMS details are well hidden secrets. Personally studying the custom BMS found inside iphone batteries and they are using a single-wire protocol (different than Dallas / Maxim Semiconductor) and is based on the Texas Instruments (former Benchmarq) HDQ interface. Regardless, the internal battery controller is a custom part built by TI for Apple and with the 'SN' prefix so no public details are available on this device.

Also, review the dual diode @ PD8900.

Confirm this diode is not leaking.

[Iherduleikgemz]

FX505DY REV. 2.1

I don't know if the tool is compatible, I've only seen it being used in other threads. Any suggestions of what software should I use? Or can I provide any other infomation that can help?

edit:

I'm sorry, but how do I check the leakage? You mean the voltage drop? It's 0.274V between pin 1-3 and 2-3

[mon2]

Review the usual DCin mosfets. Remove all power. Meter in resistance mode.

Test the resistance across the mosfets. Each measurement should be hundreds of k ohms or higher else the part may be defective.

Test PQ8901 / PQ8902.

reference:

(review the charger sticky above by piernov) - often the 2nd DCin mosfet is found to be defective in such cases.

[Iherduleikgemz]

Both mosfets measure in M ohms in any possible way.

I'm gonna go and read the whole thread while I wait for the "new" used battery.

What do you think about my measurements of the charger IC? I've tried to compare them with the datasheet, but honestly working on this laptop is something new for me. I usually deal with dead bios, dead DCin mosfets, or simple shorts that I can diagnose quite easily.

[mon2]

Mostly ok but some of the voltages drop once the battery is attached.

review the dual diode @ PD8900.

Confirm this diode is not leaking.

[mcplslg123]

Its a simple case of original battery being "Locked" and the replacement is bad.
Just try with another battery from a more reliable source.

[Iherduleikgemz]

Yup, installing an original used battery solved the issue. The laptop is charging now. I've spent more time on this than i would like to admit.

Anyways, many thanks for help!

[mcplslg123]

Perhaps a liitle bit of more experience would've saved your time. This is how we all gain experience.