Hp ZBook 17 g3 battery not charging issue

[Neddsme]

I have the laptop mentioned in the title and i am in a bit of a pickle. The laptop Power circuit got fried after someone messed with the charger and the DC input MOSFETS were toasted. I replaced them but now it turns on and works on charger only after bypassing the FETS, they dont turn even though the charger LED is ON. The bettery on the other hand no longer charges at all.

After a series of multimeter testing I concluded there is no more short but the BQ24780 chip is looking suspicious to me. Here are some voltage readings i think are relevant;
ACN ~ 19.7v
ACP ~ 19.7v
ACDRV ~ 0.4v
ACOK ~ 2.2v
ACDET ~ 2.6v
BATPRES ~ 0.0v (with or without battery)
BATSRC ~ 0.22v
BATDRV ~ 0.25v
SRN ~ 0.22v
SRP ~ 0.22v
ILIM ~ 3.37v
LODRV ~ 0.0v
REGN ~ 6.0v
BTST ~ 5.73v
HIDRV ~ 0.22v
PHASE ~ 0.22v
VCC ~ 19.15v

ACDRV & BATDRV resistance ~ 4.3Kohms

I have not worked much with this chip so I wouldnt know how a faulty one typically behaves. I dont have a spare on hand to simply try and replace it so it would be great to know if it definitely needs to be replaced or if its a different issue before i go ahead and purchase a replacement.

[mon2]

1) Do not bypass the DCin mosfets.

2) Are the DCin mosfets the proper ones for this charger IC? They should be N-channel type. Be sure they are soldered in the proper direction like the originals.

3) The gate voltge is driven by ACDRV on the charger IC. This ACDRV voltage should be ~25v = adapter voltage + REGN voltage = 19 + 6 = 25v. Only then will the 2 x DCin mosfets enable. Study the datasheet from TI to learn the conditions to drive the ACDRV voltage which is at 0v. Check CMSRC voltage.

4) Other voltages look ok. It is also possible that the charger IC believes there is an excessive current draw so it powers down the ACDRV voltage for safety. Confirm the full path resistance of ACP/ACN. Do the same for the battery charge leg current sense resistors. Each check with NO power / NO battery to the board.

[Neddsme]

Thanks for the swift reply!

1, the bypass of the DC-in was really just a hypothesis test on whether the laptop was dead and not a solution. I know very well the importance of the seemingly "unimpressive" DC-in FETs

2, Yes the FETs are known good N-type equivalents. and the drain of the FETs makes it next to impossible to solder it the wrong way, the drain is most of the pad.

3. the CMSRC voltage is at 0.22v

4, the ACP/ACN is both 100.5 ohms

5, the SRN/SRP is 0.1 ohms and 0.2 ohms

[piernov]

Measurements must be taken without the DC-in MOSFET bypass, otherwise they are meaningless.

[mon2]

4, the ACP/ACN is both 100.5 ohms

?? Confirm that this measurement is with the meter probes directly on ACP and ACN pins of the charger IC to measure the current sense path resistance. This measurement is too high if being measured in this manner. Remove all power during these resistance tests.

[mcplslg123]

Thanks for the swift reply!

1, the bypass of the DC-in was really just a hypothesis test on whether the laptop was dead and not a solution. I know very well the importance of the seemingly "unimpressive" DC-in FETs

2, Yes the FETs are known good N-type equivalents. and the drain of the FETs makes it next to impossible to solder it the wrong way, the drain is most of the pad.

3. the CMSRC voltage is at 0.22v

4, the ACP/ACN is both 100.5 ohms

5, the SRN/SRP is 0.1 ohms and 0.2 ohms

Do you mean resistance to Ground on ACP/ACN measured each at a time or you mean resistance between ACP/ACN pins?
If its the former,then you have short on main power rail ,ie, +19V rail.
If its the later option,then check continuity between ACP/ACN pins to CLR.

However, i think you mean the former option.

[Neddsme]

Measurements must be taken without the DC-in MOSFET bypass, otherwise they are meaningless.

Yes, i removed the bypass after verifying it turned on then started taking all these various measurements.

[Neddsme]

?? Confirm that this measurement is with the meter probes directly on ACP and ACN pins of the charger IC to measure the current sense path resistance. This measurement is too high if being measured in this manner. Remove all power during these resistance tests.

Unless I am doing it wrong, but the ACN and ACP pins on the IC have some resistors in series with the tracks on the path to the current sensing resistor. the current sense resistor measures 0.5 ohms on its own but measuring from the pins of the IC to the current sense points I get 100.5 ohms. And yes this is with power removed. the only measurements taken with power were voltage readings.

I am assuming there are 100 ohm resistors added to the path maybe? IDK

[Neddsme]

Do you mean resistance to Ground on ACP/ACN measured each at a time or you mean resistance between ACP/ACN pins?
If its the former,then you have short on main power rail ,ie, +19V rail.
If its the later option,then check continuity between ACP/ACN pins to CLR.

However, i think you mean the former option.

For the ACN/ACP measurements it was from the pins of the IC to the CLR.

Just to make sure I retook the measurements;
ACN/ACP to GND = OL
CLR ~ 2 ohms
ACN to ACP on the IC ~ 200.6 ohms
ACN/ACP to CLR ~ 100.5 ohms
The resistor in between CLR and IC ~ 100.4 ohms

There is no short to ground, just an "odd addition" of 100 ohm resistors to the ACN/ ACP path.

[piernov]

Then if 19V goes through the DC-in MOSFETs but ACDRV is not turning them on, most likely there's still a problem with the DC-in MOSFETs.

[mon2]

Any chance that you have the schematics for this laptop? Link it if available but post the schematic in the dedicated schematic forum. Respectively, check the resistors that should be present in the current sense path between ACP / ACN pins. Sounds high to me if @ 100R ohms.

[Neddsme]

Then if 19V goes through the DC-in MOSFETs but ACDRV is not turning them on, most likely there's still a problem with the DC-in MOSFETs.

NEW DEVELOPMENTS

Yes! as it turns out there was a broken track on CMSRC, probably it suffered some physical damage during disassembly.
After finding the anomaly and fixing it, there are some new readings now.
ACN ~ 19.7v
ACP ~ 19.7v
CMSRC ~ 19.7v
ACDRV ~ 25.4v
ACOK ~ 2.3v
ACDET ~ 2.7v
BATSRC ~ 12.0v
BATDRV ~11.99v
SRN ~ 11.98v
SRP ~ 11.99v
ILIM ~ 3.37v
LODRV ~ 0v
REGN ~ 6.0v
BTST ~ 5.74v
HIDRV~ 12.33v
PHASE ~ 12.01v
VCC ~ 19.16v

I don't know the specifics but i assume this looks like a good BQ chip. However the BATDRV, BATSRC, AND PHASE look off in my opinion but i could be wrong.
The battery is a 96Whr 11.4v nominal voltage battery which i assume charges at around 13.05VDC (info on the battery itself).

So 12.0v on the battery terminals looks kinda low to me. But this is with the battery unplugged. Infact all those readings above are with the battery unplugged. When the battery is plugged in the story is a bit worse;
The Battery terminals stay at around 0.22v for the first milliseconds after plugging in the charger, then it spikes to around 9.90v before it drops back down to 0.22v
During this time, the following readings are registered;
BATSRC ~ 0.22v
BATDRV ~ 0.25v
SRN ~ 0.22v
SRP ~ 0.22v
PHASE ~ 0.22v

The rest of the measurements are as before only the ones related to the battery change when the battery is connected.
The battery charging light also stays amber throughout when the battery is unplugged but turns off after that spike to 9.90v when the battery is connected which seems odd as if its shutting down the battery circuit on purpose.

Lastly, i tried taking a look at the battery itself. i found it in a discharged state. >2.7v each cell. I brought back up the cell voltage with a custom balance charger i have for other projects to around 3.8v on all cells which should wake up most batteries but in this case i fear maybe the battery is done for? IDK the battery pack was still in good shape pulling 4-5 hrs on a heavy system like this before the whole charger fiasco happened.
I tried pulling a battery report and I get a report which shows the battery with 15% and 530 cycles but no prior information as it was a fresh windows installation. My assumption is that there is still some life in the battery.

What are your thoughts, and what are other things i can check for?
Is the battery charging portion of the BQ chip acting like its supposed to or something is still not right?

[Neddsme]

Any chance that you have the schematics for this laptop? Link it if available but post the schematic in the dedicated schematic forum. Respectively, check the resistors that should be present in the current sense path between ACP / ACN pins. Sounds high to me if @ 100R ohms.

Unfortunately i don't have the schematic. that would have saved me a lot of guess work. I did a search on the forums and someone already posted a request for this specific model's schematic and boardview but nothing turned up so i didn't want to create a redundant thread. I am keeping tabs on that thread incase someone finds it.

As for the resistors, i am just as puzzled as u are why the implementation has 100 ohm resistors on it. the battery current sense path does not have these resistors only the AC side. A guess would be maybe coz its a heavy power system? it uses like a 150Watt adapter and using anything below that the system does not turn on at all. (I tried with 45W though so maybe 65W might work IDK. But this also means it can identify chargers as its supposed to making me believe the BQ chip is definitely alive)

[mon2]

ACOK looks low. Study this pin and locate a pull up resistor used to park this line. It should most likely be to a 3v3 rail but you have 2v3. This may be due to a defective always rail. Measure the voltage on each side of this resistor.

[piernov]

Yes! as it turns out there was a broken track on CMSRC, probably it suffered some physical damage during disassembly.

Still doesn't make a lot of sense because that would indeed confirm ACDRV wasn't working, but then the DC-in MOSFETs should have been turned off (at least the one placed with the body diode in reverse) and no voltage should have been measured after them.

Also the measurements must be taken again after charging the battery cells.

[Neddsme]

ACOK looks low. Study this pin and locate a pull up resistor used to park this line. It should most likely be to a 3v3 rail but you have 2v3. This may be due to a defective always rail. Measure the voltage on each side of this resistor.

Yes the 2.3v is coming from a rail with 3.38v. the resistor in between is 15K (resistance measured while power is disconnected).

[mon2]

ACOK is an open drain signal. If the charger believes the power adapter source is OK, then this output signal line will float. Then the park voltage will be based on the pull-up resistor + pull-up voltage (3v3) and the load on this line. On a good board, this line should be ~3v3 but you have 2v3.

Remove all power. Measure the resistance to ground of this same ACOK pin. Also check it in diode mode. Meter in DIODE mode. Red meter probe to ground. Black meter probe on ACOK pin. Post both measurements. Perhaps someone using this ACOK status is defective.

[Neddsme]

Still doesn't make a lot of sense because that would indeed confirm ACDRV wasn't working, but then the DC-in MOSFETs should have been turned off (at least the one placed with the body diode in reverse) and no voltage should have been measured after them.

Also the measurements must be taken again after charging the battery cells.

Yes that's true. The DC-in mosfet source and drain was shorted. I didnt pick that up initially because it did not short to ground. I replaced it along with fixing the CMSRC track.

This circuit is becoming a bunch of spaghetti now. a schematic would have made things a bit simpler lol.

The battery pack is perfectly balanced at 3.69v but does not output voltage
from the report it shows 10% charge. could it be locked?

[Neddsme]

ACOK is an open drain signal. If the charger believes the power adapter source is OK, then this output signal line will float. Then the park voltage will be based on the pull-up resistor + pull-up voltage (3v3) and the load on this line. On a good board, this line should be ~3v3 but you have 2v3.

Remove all power. Measure the resistance to ground of this same ACOK pin. Also check it in diode mode. Meter in DIODE mode. Red meter probe to ground. Black meter probe on ACOK pin. Post both measurements. Perhaps someone using this ACOK status is defective.

In diode mode there is .463 voltage drop

in resistance it reads 12.4K

[mon2]

Yes. Test with a known good battery. Amazon? The ACOK voltage is lower than normal. Perhaps consider to replace the pull-up resistor with another. The value is not critical. Test with a 10k or 4k7 or 2k7, etc.