Battery not charging in ASUS G532LWS Motherboard -> BQ24780S

[cope]

Hi everyone,

I have been working on a no power issue with my personal ASUS gaming laptop. It went dead a few months ago.

Some history:

Since then, I've found a blown mosfet on the GPU line which I replaced. It started up without a battery, then when I added the battery back it wouldn't start up again.

As a result, there were some blown components around the BQ chip. (The BQ chip itself - BQ24780S, the low side battery mosfet (shorted), and a resistor -> all replaced)

Now, with a new battery the system will start up and run off the battery. I can charge the battery by boosting the charge circuit with my bench supply, or directly charging it using my bench supply. I cannot get the voltage on the charge coil to go above battery voltage.

It also runs fine on the adapter with the battery present and missing.

The only thing remaining is figuring out why the chip is not charging the battery.

TL/DR -> I've almost got my dead laptop fixed but for some reason it won't start charging. I'm new to BQ chips so I have no idea what a healthy one looks like, though I've been watching lots of videos so I may know enough to be dangerous. I'd love some help troubleshooting the voltages/etc and see if I can figure out what's wrong with this circuit. Thanks!

Motherboard model: G532LWS
BQ Chip: BQ24780S

I'm attaching the schematic, boardview, and BQ datasheets I've been working off of.

[mon2]

Hi.

1) The schematic & BV files should be moved to the dedicated schematic forum so that they are easier to locate in the future.

2) Carefully measure the voltage to ground of BATPRES# (pin 15) on PU8900 (charger IC). This netname has a '#' suffix = ACTIVE LOW signal. So if this signal is a logic LOW = ~0 volts, then the battery is considered to be attached; otherwise is absent.

Q: Does the Windows OS detect the presence of the battery? It is possible that the BMS (controller board) inside the battery pack is defective. Have you tested with another known good battery? It should be available on Amazon and you can return it if it is not required.

[SMDFlea]

Link to schematics & boardviews https://www.badcaps.net/forum/troubl...atic-boardview

[cope]

Hi.

1) The schematic & BV files should be moved to the dedicated schematic forum so that they are easier to locate in the future.

2) Carefully measure the voltage to ground of BATPRES# (pin 15) on PU8900 (charger IC). This netname has a '#' suffix = ACTIVE LOW signal. So if this signal is a logic LOW = ~0 volts, then the battery is considered to be attached; otherwise is absent.

Q: Does the Windows OS detect the presence of the battery? It is possible that the BMS (controller board) inside the battery pack is defective. Have you tested with another known good battery? It should be available on Amazon and you can return it if it is not required.

I will look into posting them in the schematic forum, thank you. (EDIT: I see SMDFlea took care of this for me , thank you!)

The OS does detect the battery and shows the current battery level (6%), it also says it is charging but it does not actually charge.

I have measured all voltages on the BQ and written the voltages on the schematic. Attached to this message.

Pin 15 is 0V

This is with the battery connected and the adapter plugged in.

My factory battery has a blown fuse so the battery I have in is a replacement from Amazon that I ordered last week.

[mcplslg123]

Measure resistance between ACP/ACN pins of charging IC.
Measure voltage on dc -in mosfets on pin 1/4/8
ACOK/ACDET/REGN/SDA/SCL/VCC-voltage on these pins of charging Ic?

[cope]

Measure resistance between ACP/ACN pins of charging IC.
Measure voltage on dc -in mosfets on pin 1/4/8
ACOK/ACDET/REGN/SDA/SCL/VCC-voltage on these pins of charging Ic?

All charging IC voltages are written on the attached schematic picture above next to each pin in white text. But for those pins:

ACOK - 5.95V
ACDET - 2.7V
REGN - 6.01V
SDA - 3.24V
SCL - 3.25V
VCC - 19.63V

For ACP/ACN resistance I measured resistance across PC8902. -> 1.4 ohms

DC in voltage (PQ8901/PQ8902) has been ~25V on the gates and ~19.8V on source/drain (not near the laptop currently so this is ballpark, I can get exact numbers). It does run fine on the adapter (gets into windows, cpu doesn't throttle, GPU is recognized, etc)

[mon2]

Remove all power. Meter in lowest resistance mode. Measure the resistance between pins 18 (SRN) & 19 (SRP) on the charger IC. Perform this test directly at the pins of the charger IC PU8900.

Post your measurements.

[cope]

Remove all power. Meter in lowest resistance mode. Measure the resistance between pins 18 (SRN) & 19 (SRP) on the charger IC. Perform this test directly at the pins of the charger IC PU8900.

Post your measurements.

mon2 OK, on the chip itself I am getting 0L, but there's some flux from the resolder that might be getting in the way of the probes making contact. Are you thinking those pins may not be soldered to the board well? (totally possible, this is my first IC aside from practicing on a non-working board).

I'll clean it up and see if i can get any measurements. If still 0L should I try to reflow?

[mon2]

That is too low of a resistance measurement for the full current sense path of resistors. It should be ~20 ohms. Confirm it again.

Also, short the meter probes. What is the measurement? Then place the meter probes across resistor PR8912. Note the value. Repeat to test the resistance across PR8911. Each of these resistors should be ~10 ohms.

[cope]

That is too low of a resistance measurement for the full current sense path of resistors. It should be ~20 ohms. Confirm it again.

Also, short the meter probes. What is the measurement? Then place the meter probes across resistor PR8912. Note the value. Repeat to test the resistance across PR8911. Each of these resistors should be ~10 ohms.

mon2 Did you possibly see my first post? I accidentally measured across ACP-ACN instead of SRN-SRP (then edited the post).

On the chip pins (SRN-SRP) I am getting 0L (infinite resistance) between those two pins. The resistors themselves both measure ~10 ohms, and if I measure on the ic side between those resistors I get 20.5 ohms.

My probes measure 0.3 ohms.

I can put all of this on a picture if it helps, or put the resistances on the schematic like I did the voltages, let me know how I can make it more clear.

[mon2]

Measure the resistance path from pin # 2 of each of these resistors and the measurement should be ~20 ohms. If yes, this is good.

Then keep probing further but move only one meter probe directly onto the charger IC pin. You should still have ~20 ohms. Finally, move both meter probes onto the charger IC @ SRN / SRP and again, if all is well, you should have ~20 ohms. Be sure your pin # counting is correct. If you see a fault here - this is the root cause of this failure.

Yes, do post pics so we can all review the PCB tracks.

[mcplslg123]

Check PR8911/12 out of circuit.

[cope]

Measure the resistance path from pin # 2 of each of these resistors and the measurement should be ~20 ohms. If yes, this is good.

Then keep probing further but move only one meter probe directly onto the charger IC pin. You should still have ~20 ohms. Finally, move both meter probes onto the charger IC @ SRN / SRP and again, if all is well, you should have ~20 ohms. Be sure your pin # counting is correct. If you see a fault here - this is the root cause of this failure.

Yes, do post pics so we can all review the PCB tracks.

I looked closely at those pins and saw copper, so I ran a hot iron down that side to clean up the joints and the battery is charging now! 25% and climbing. Here's hoping it stops trying at 100%!

[mcplslg123]

The first thing i check in not charging case is resistance between ACN/ACP & SRN/SRP.

[cope]

The first thing i check in not charging case is resistance between ACN/ACP & SRN/SRP.

This time it seems like it must have been a bad connection between the SRN pin and the motherboard when I resoldered it. Cleaning up the solder joints has thus far solved the issue and the laptop is fully functional.

Thanks to everyone for their help!

[cope]

mon2 Are you aware of any reason that a low battery voltage would inhibit charging? After allowing it to drain and plugging it back in it is not charging and the battery is remaining at 6%.

I can charge the battery with my bench supply still so the fuse is still good.

[mon2]

Carefully measure the voltage to ground of pin # 21 on the charger IC = ILIM. This voltage defines the peak current that the charger will supply to charge the battery.

[cope]

Reading 1.182V on pin 1 of PC8911 which is P_CHG_ILIM_10 on the BV/schematic (I am nervous about measuring the pin directly with a charged board, I blew another cap a month back by bridging it to ground on accident).

[mon2]

The calculated value for this ILIM equates to the same. This measurement is ok.

[mon2]

When you 'drained' the battery - did the battery percentage ever change? Are you able to extract the battery serial #, etc. on Windows ? Arduino tools ? Just want to confirm that the SMBUS / I2C interface is not defective. You can also remove all power -> meter in DIODE mode -> measure the battery connector pins on the logic board and post each diode mode check. We are checking if the ESD diodes are shunted and may be causing goofy readings by the host SMBUS controller.