Asus ROG G751JY No Power (Short)

[mon2]

My bad. We should have just selected the BATDRV pin on the charger IC inside the boardview file and this would then highlight the 4k resistor in series with the battery mosfet. That is, using this approach, the battery mosfet is @ PQ8803.

Remove all power. Meter in resistance mode.

Measure the resistance across this mosfet like before:

source & drain
source & gate
gate & drain

Post each measurement. No adapter / no battery during these tests.

[TheWizard]

No worries man. I appreciate the help.

At PQ8803..

Source to Drain = 4.34 kohm
Source to Gate = 2.068 mohm
Gate to Drain = OL

[mon2]

Source to Drain = 4.34 kohm

This could be the show stopper. At this time, flux and carefully remove this mosfet off the board. Be careful to not disturb the other parts in the same area - low air pressure is recommended. After this part is removed, attach your battery and power adapter again to test the state of the charger. Leave this mosfet off the logic board.

[TheWizard]

Okay. Seeing as how the mosfet is right beside two electrolytic capacitors.. I normally just put heavy kapton tape around them and heat from bottom of board as much as i can then advance to top. Don't want to pop one of them caps. Any other ideas?

[mon2]

Do your thing with the kapton tape and also suggest to cover it to the best you can with aluminum foil. Use the smallest nozzle you can to remove this component. To me, with the reported readings, this mosfet appears to be leaky and should be replaced. Proof will be when you measure the same component on your work table after it cools down and/or test if the charger functions properly with the battery.

[TheWizard]

Mosfet is removed.

- Connected battery to motherboard
- Connected AC Adapter to motherboard
- +v reads 13.90v

Does not seem to be a change.

[mon2]

- +v reads 13.90v

Is this a stable voltage? Check the voltage on the battery when it is on your work table. What voltage do you measure with the meter on ground & +V (3 pins) on the raw battery itself?

That is, the charger IC is most likely creating the 13v9 to charge the battery. Does this voltage stop after a few seconds? What does Windows report for this battery?

Do confirm the SMBUS lines on this battery connector - the SDA & SCL lines should be ~3v3 for each to ground.

[TheWizard]

Yes. Voltage is stable.

Raw battery voltage is 13.90v. Voltage is constant.

I would have to reassemble to know what Windows shows for battery detection.

I believe you are referring to where the orange and blue wires run into the battery connector when you state SDA and SCL lines. Those are 3.25v to ground.

Should I reassemble and see what the battery indicates in Windows? Or do you want to test something else first? I still have Mosfet off.

[mon2]

Does the battery light indicate that the battery is being charged? Or does so and then halts charging after a small period of time? If yes, test with the other battery as well.

Then remove the battery and all power. Meter in resistance mode again. Check the HIGH SIDE and LOW SIDE mosfets that dial up the battery charge voltage. We can use the boardview diagram again to assist us.

[TheWizard]

So you want me to reassemble the laptop then and test without the mosfet we removed connected? Just confirming.

i have not reassembled yet. But connected old battery to board and was only drawing a little over 1v. Connected the New battery and was drawing our 13.90v again.

Connected old battery and AC adapter. That receives 0.814v from +V pins of connector.

[Vesko356]

At this stage my advice is to test the laptop with another known good battery first. Often replacement non original batteries are faulty out of the box, and that may be also the case here.

[TheWizard]

Vesko356,
Thanks for joining the party. This battery was purchased from ifixit. When i first recieved it last week the battery ran the laptop a couple days on its own in testing phases. I believe the New battery is good. Just feel there is something messed up with the charging circuit somehow.

[mon2]

I too agree that testing with a fresh known good battery is worthwhile. Amazon USA has a few in stock so you could test by tomorrow.

Carefully check the voltage to ground of the smbus sda and scl lines but on the charger ic. Be extra careful so the probe does not short other pins. Next, remove all power. Meter in resistance mode. One meter probe on the charger ic sda pin; other probe on the sda pin on the battery connector. What is the resistance?

Repeat for the scl pin checking. It is the charger ic that communicates with the battery bms board for charging.

[TheWizard]

Yeah i just paid 60 dollars for this one last week. I could send back the battery to ifixit for an exchange.

Check the voltage to ground of these lines with battery and ac adapter connected or just ac?

The resIstance measurement you mention will be hard to perform. The charger IC is on the back of the board and the battery connector is on the front.

Should i try assembling and seeing what Windows says with PQ8803 mosfet removed?

[TheWizard]

mon2,
The SDA and SCL lines read 3.2v. I just requested an RMA for the New battery i received from ifixit as well. We will see what they say.

[mon2]

With a good battery, the charger ic should take the adapter voltage and lower it to a safe voltage to charge the battery pack. At this time you are only measuring the battery voltage and not the charge voltage created by the charger ic. It is possible that the charge voltage is there but then turned off due to some faulty condition. If the battery bms is faulty, the charging will stop. From the posts, you will probably see the same condition in Windows but you can test it while these batteries are in your possession.

[TheWizard]

Okay sounds good. I will test today and report back with my findings. Thank you.

[TheWizard]

One thing i wanted to point out though.

mon2,
Where we removed PQ8803. I took a reading and the gate pad of where that mosfet would sit is reading 1.73. Shouldn't that be like a 0.45 or so voltage drop instead?

[TheWizard]

Assembled without mosfet. Laptop has the same symptoms as before. Battery will boot up and run laptop when AC Adapter is not connected. Laptop recognizes when AC is connected. Windows starts to indicate charge then drops after like 10-20 secs.

[jasko_jacker]

The battery chip is driven by the host, have you tried reprogramming the bios or ec (if it doesn't it self reprograms