Lenovo ideapad 5 windows 11 update disable charging circuit?

[bogart219]

Hello fellows. My Lenovo ideapad5 151al7 doesn't charge my battery, this seemed to happen right after an win 11 update, at least that is when I noticed it. I rolled back the update but it didn't matter. The laptop doesn't work off of the power adapter, which btw, I always leave plugged in and never really use the battery. New power adapter and battery, same problem. USB-c connector. The battery monitor in setup says "charger not installed", (but it is). Using a usb tester, with the battery plugged in it reads 20 volts but no current. With the battery unplugged it only reads 5 volts with no current. Not sure what to make of this. I never worked on a laptop motherboard before. any help and guidance would be greatly appreciated!

[mcplslg123]

Should 've mentioned mb markings and link schematic to get proper response.

This has nothing to do with win11 update.that may be a mere coincidence.

[bogart219]

Mcpisig, Thanks for responding. Yes I believe the motherboard number is 5B21H70694. I don't have the schematic for this laptop. I put a request in for one but no luck. What does the fact that with the battery plugged in the usb tester says 20 volts but with the battery unplugged it says only 5 volts. Does this tell you anything?

[m1ch43lzm]

Hi, the board number is here, it's not quite clear from the picture

Should be something like NM-****

From your part number (5B21H70694) /laptop model (15IAL7) i found this, please confirm

JS574 NM-E401

Please update your post on the schematics request forum with the proper info, someone may have it

[bogart219]

m1ch43lcm, yes I see that number stamped on the board, Js574 NM-E401 the number you found, Rev. 1.0 Thanks for the info!

[mcplslg123]

With only usb-c adapter connected, it is stuck at 5V-so definitely you have problem in PD controller/its firmware/charging circuit.
It should negotiate to 20V with adapter only.

[bogart219]

Yes, stuck at 5 volts. I was going to try some voltage injection on the main rail (1 volt, 1 amp), as soon as I determine where the main rail is at.I have a thermal camera. I've been watching a lot of Youtube videos by electronic repair school. I even have some freeze spray I can use to look for a hot component. I would like to try to fix it myself before taking it to a repair shop. This very educational. I'm 69 and love electronics. Thank you for any help you could provide!!

Here are some better pictures.

[mon2]

Found only a boardview file for this model. Can post it if needed.

PU5301 is your charger IC = BQ25710.

Carefully measure the voltage to ground on pin # 18 = CHARGE_PRES with the power adapter connected. This is the sense pin to gauge if the power adapter is connected or not.

Test with only the power adapter. Then test with both, the power adapter and battery connected. Post all measurements.

[bogart219]

Thanks Mom2, now were getting somewhere. I'll do those test and post them here. Thanks!

Testing to ground on BQ chip terminal 18.
With power adapter only = 0 volts
With power adapter and battery plugged in = 0 volts

[mon2]

Review the 2 voltage divider resistors that mate with pin #18.

PR5322 = should be ~33k ohms. Pin #1 should be mated to the raw adapter voltage so ~19v.
PR5328 = should be ~100k ohms. Pin # 2 should be to ground.

Together, they will lower the adapter voltage to a safe value to allow the charger IC to monitor the adapter presence. Ideally 2v7 or higher is the normal value here. With 0v, maybe one of the resistors is missing or is defective.

[m1ch43lzm]

I was going to try some voltage injection on the main rail (1 volt, 1 amp), as soon as I determine where the main rail is at.

No need to do that, your laptop already powers on from battery (the battery powers the main rail), voltage injection on the main rail is used only when the board has a short circuit (completely dead/no power)

The issue you have is that it's not negotiating 20v with the AC adapter / not charging

Can you try plugging in the charger (with the usb-c meter attached) in the other usb-c port?
Try both orientations

Also try plugging the usb-c meter itself (with nothing attached) to both ports, expected behavior is for the usb-c meter not to power on, unless you plug in a type-c device to the other end

I had a similar issue with a Yoga 9, where one of the usb-c ports had a bit of moisture/corrosion in it, it wouldn't charge from the port marked with the power cord symbol, showing 20v 0amp, but from the port next to it it would charge fine
And sometimes it wouldn't charge from the other port, but it would charge from the "damaged" port but only in one orientation, cleaning the ports solved the issue
i think this is by design, as some people would try to plug in 2 usb-c chargers at the same time...

[bogart219]

Mom2, I was skeptical of my Ali express meter and redid the measurements with my Fluke, why seemed more accurate.

Testing to ground on BQ chip terminal 18.
With power adapter only = 0 volts
With power adapter and battery plugged in = 10.6 volts Battery voltage at JBAT1 terminal 1&2 = 10.6 volts

Resistor PR5322 = 30K
Resistor PR5328 = 70K

Mich43lzm, Tried plugging in to the other usb-c port, same thing 5 volts, same trying in both directions.
I blew out and cleaned both usb-c ports with contact cleaner, no difference.

[mon2]

Meter in resistance mode. Touch your meter probes together and you should have ~0R ohms.

Remove all power to the board. One meter probe on pin #18 of the BQ charger IC; other meter probe to the common short point between the 2 resistors under test (PR5322 & PR5328).

Confirm that you have ~0R ohms to this point. Test the voltage to ground at the same common point at these 2 resistors with the power adapter. You should have a lower signal voltage here created by the power adapter and these 2 resistors.

[bogart219]

Hey Mom2, could you explain what you mean by " common short point between the 2 resistors under test (PR5322 & PR5328)", I'm a little confused. Thanks!

[mon2]

The PCB trace that connects to pin #18 on the charger ic is mated to the 2 resistors. This midpoint connection must offer a low voltage here. Google ‘resistor based voltage divider calculator Digikey’. You will find a drawing and a calculator. Stuff 19v and the resistor values in ohms. The calculator will provide the expected voltage for pin #18.

[bogart219]

Mom2, by " midpoint : connection, do you mean that solder point that is circled in the picture? I have continuity between pin18 and pr5328 but no continuity between pin 18 and pr5322. It seems I'm not getting any voltage anywhere. I'm only getting 5 volts on the usb-c tester with the power adapter plugged in. Whent to the digikey site for the voltage divider, didn't understand it.

[mon2]

Can you read the topside markings of this PU5301 chip? Should have requested this earlier. Want to be 100% sure the charger IC is the same as the BV file reports.

See attached - my yellow lines. You must have conductivity from pin #18 to the yellow line end points - should be ~0R ohms otherwise there is a trace break somewhere on the board.

Confirm it.

On this note, the label of this pin has me following the wrong path. This pin #18 defines the battery pack charge voltage so for now, probably can be ignored. It is not the CHARGER_PRES - it is CHARGE_PRES.

See attached for a reference schematic for this charger IC. Your logic board will be very similar.

Confirm the voltage to ground for the following pins (with the power adapter) - be sure your meter probes are small enough for this task:

VBUS pin #1
ACN pin #2
ACP pin #3
VDDA pin #7
REGN pin #28

[bogart219]

Hey, with the chargeradapter plugged in and the battery disconnected, I get 0 volts to ground on those pins you had me check. This board says Rev. 1. that boardview file says Rev.10, if that matters.

The BQ chip says:

BQ25710
TI 238
A97V

Usb-c tester at 5 volts.

[mon2]

Ok. Remove all power. Meter in resistance mode. Measure the resistance to ground of pin #22 = VSYS. We are checking if there is a short on the main power rail.

[bogart219]

Good morning. Going by the boardview image of pin 22, measuring to ground reads approx. 2 meg.

Don't think I mentioned this but for clarity, with the battery plugged, the lappy works fine, it just won't charge the battery. With just the power adapter, it doesn't work at all. Also, I have just left the power adapter always plugged in, never using the battery really. Thanks