Dell G3 15 3500 - Battery bug (black screen and flashing keyboard backlight)

[HTR-Informatique]

Hello,

YouTube video of the problem encountered: https://youtube.com/shorts/q7TLNv36LUo

I am a pro and I have a problem that I have never seen despite my 7.5 years of experience on my own and my thousands of repairs, on a customer's Dell G3 15 3500.

On this PC I have already changed the complete palmrest because the keyboard was no longer working properly.

I also changed the screen because the PC fell and the screen was broken.

I changed the battery with a new and original battery.

I also had corrosion/oxidation on the power supply part of the RAM, but it is cleaned, and no more worries.

The problem I have now is that the PC works without any problems on the mains, but when I unplug the charger, the screen goes black and I have the keyboard backlight flashing, Caps Lock LED that stays on.

I just have to reconnect the charger, so that the PC restarts and works again without problems.

I have already exchanged the battery with the seller, always a new and original Dell battery.

The worst thing is that the PC charges very well and is able to work on battery.

I just have to do a CMOS clear, and the PC works without problems on battery.

But, I do not change any BIOS settings, I put the PC on battery, after the CMOS clear, I turn it off, black screen and keyboard backlight flashing.

I force stop it with the button, I turn it back on, on battery, same problem: black screen, keyboard backlight flashing and Caps Lock LED lit steadily.

I put the charger, the PC works without any problems.

The BIOS is in version 1.32.

I tried to reinstall Windows, same problem.

The problem also occurs when the PC is in the BIOS.

I do all the DELL tests, no problems.

The BIOS sees the original Dell 240W charger and the battery, charged to 100% and in excellent health.

I tried to modify different BIOS settings but nothing works.

I tried to downgrade to 1.31 (I can't go back further for security reasons, DELL limits), but the same.

I do electronic repairs/microsoldering on laptop motherboards, but in this case, it's not just a problem with a MOSFET/HS charging chip because the PC charges and can still run on battery, just after a CMOS clear.

I really don't see where the problem could come from.

I have already tested 4 BIOS from Electronic Repair School: new BIOS, clean ME, NVRAM, as well as 2 BIOS from Badcaps.
Only the second one from Badcaps allows you to start the PC, all the others are black screen, but I always have the same battery problem.
The BIOS have 5 white LEDs and 3 orange in the worst case and black screen.

Now even with a clear CMOS I can no longer start on battery.

Thanks in advance.

[mon2]

Share the voltage to ground on each pin of the battery connector. Connect both, the battery and power adapter.

[HTR-Informatique]

PINS 1, 2, 3 : 16,7V
4 : 3,3V
5 : 3,3V
6 : 0V
7: 0V
8, 9, 10 : GND

[HTR-Informatique]

Up ?

[mon2]

Battery smbus lines are not shunted. Trace the same smbus lines to the charger chip pins. Confirm there is no disconnect.

Link the schematics if available in the schematics forum.

Is there a cmos / rtc battery onboard? If yes, test with a fresh one.

[HTR-Informatique]

So yes, there is a CR2032 battery, but it's OK, I even tested with another one, or without, same.
Afterwards, an SMBus problem, I thought about it, but I upgraded/downgraded the EC via the different BIOS on the Dell site, still the same.
On Windows in addition, the battery communicates well, I have the charge LED, the battery charges, I have the battery level, the time remaining before full charge.
In addition, with a CLEAR CMOS, I can immediately, after the CLEAR CMOS start on battery, and everything works, I have the remaining autonomy time.
So well, right now even with a CLEAR CMOS I can no longer start the PC on battery.
The PC tries to turn on on battery, the keyboard turns on/off in a loop but nothing, and as soon as I plug in the charger, the PC starts without problem.
So that's why this problem is incomprehensible to me.
I don't think there are any problems with SMBus communication then, but I can check yes.
Before I just had to do a CLEAR CMOS, it worked immediately after, but if I turned off the PC and turned it back on on battery, I had the keyboard that turned on/off in a loop, and I had to put the charger in to start.

[the Benninger]

In your case, I would start looking at the components with a thermal camera to see if I notice any components heating up too much before starting the light show.

[mon2]

Schematics?

What is the voltage to ground of RTC_DET#?

EC is the MEC1416 @ UE1?

Check the power rails when using the battery and when using the adapter.

Test the MEC_XTAL1 / MEC_XTAL2 and XTAL for operation.

CMOS parameters will be stored inside the EC which is battery backed by the CR2032. If you have to reset the CMOS contents to allow for a boot, the battery and/or the MEC1416 are suspects. Perhaps the EC RAM is defective? The MEC1416 appears to be available through standard distribution like Mouser / DK / Microchip online. Do not believe this EC requires to be programmed by internal flash.

Suggest to review the voltage on each pin of the charger IC with the adapter and battery; then with the battery only. Post the list of pins with their netnames (pin function) for a review.