820-2914 Battery problem

[hjpl]

Hello and congratulations to the whole team.
820-2914 clean board, no history available.
With only the battery connected: the device does not start, only green light, no signal from the BIL.
By connecting the charger: BIL starts working again, the device starts (without pressing the power button, as if there were no battery) but it restarts before completing the startup.
With just the charger: it starts and passes the ASD efi test without errors.
PPBUS_G3H 12.57 with and without battery
diode mode SCL/SDA 0.481/0.479 W - 0.509/0.508 W/O
SCL/SDA 3.46/3.42v W - 3.46/3.46v W/O
Resistance between pin 17/18 3.6 ohm, 27/28 20.9 ohm
U6900
1. 3.48v
4-5 3.46v
U6901
1-2. 3.32v
4-5. 3.48v
Thanks for your help.

 

[2informaticos]

"With only the battery connected... only green light"
Green light where, if the charger isn't connected?

I recommend you to test with known working battery (even old one).
The battery isn't recognized at all?

Does it restart in safe mode too?
If not, I suspect GPU issue; you can disable it for test.

 

[hjpl]

Sorry, I meant that if I insert a battery that is not fully charged the light stays green.
The battery in use works perfectly on other boards, however I have also tried other known working batteries with the same result.
With the battery inserted the Mac starts up as soon as I connect the charger (as if there were no battery) but it doesn't complete the startup, so I can't access the OS to check if the battery is recognized (do I have to hot plug the battery?).
By booting into safe mode I get a reboot.
Without battery the device starts and loads the OS without problems.

 

[2informaticos]

Check with charger and battery, disconnecting BIL.
Also check diode mode to ground at SYS_ONWIRE line; compare with good board, if possible.

Can you complete diagnostic mode with battery connected?

 

[hjpl]

Already checked with charger and battery disconnecting BIL, the device reboot itself.
Diode mode SYS_ONEWIRE 0.592 / good board 0.572
With battery connected the Efi diagnostic mode completed without errors, OS diagnostic run untill gpu test then reboot.
No change with Gpu disabled.

 

[2informaticos]

If GPU test fails, then that is a problem.
How did you disable GPU?

 

[hjpl]

Correction: with the GPU disabled the device starts but the working battery is reported as requiring replacement immediately and is not charged (on other working boards the status is normal and the charge works). As soon as you disconnect the power supply, the device turns off. I already tried with other working batteries.

 

[2informaticos]

Looks like you are using replacement battery.
I saw this symptom on 2915 boards with GPU disabled.
You should disable all dedicated graphics power supplies; vRAM and GPU.

Test with original battery, if possible.

 

[hjpl]

I'm actually using an original Apple A1383 battery. I disabled the gpu by modifying the bios and removing the R8911, the gpu shouldn't be powered, or am I wrong?
Can you tell me exactly which components to remove, please?

 

[2informaticos]

GPU has more power rails than its core.
These are mentioned on page 91 (GPU Rail Sequencing).
Now find corresponding page of each one and disable them.