Macbook M1 A2337 EMC 3598 weird battery charging problem

[brockauly]

Hi guys,

If I unplugged the battery and the charger, then plug the battery then the charger, it charges without problem.
Then if I unplug the charger and plug it back, it won't charge anymore.
In the first case, main voltage is regulated at ~12.5V and charges the battery.
After unplugging the charger, main voltage drops to battery voltage at ~11.5V.
After replugging the charger, main voltage stays at ~11.5V and won't go up to ~12.5V again.

I found C520A (2.2µ after current sensor from USB-C source) completely burnt and removed it properly. I cleaned around and probed every signal around, I haven't found anything wrong.

Schematics and brd are available in https://www.badcaps.net/forum/troubl...creen-provisor.

Any idea ?
Thanks

[mon2]

Remove all power. Disconnect the battery. Meter in resistance mode. Measure the resistance across the battery mosfet at Q5625 (battery mosfet).

Test:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement. Each measurement should be hundreds of k ohms or higher. Otherwise, the mosfet may be defective.

[brockauly]

Thank you for your answer. I suppose you mean Q5265 which is indeed the battery mosfet.

Drain-gate : 12Mohm
Drain-source : inf.
source-gate : 3Mohm

I have also tried to measure everything accross the double mosfet q5230 and q5240 (difficult because pads unreachable, i measure on surrounding caps thank to the brd. Nothing is shorted.

[mon2]

Remove all power. Meter in resistance mode.

Measure the resistance across C5260. Meter probe on each end of this capacitor. We are checking the battery charge current full path resistance. Compare this value against the schematic values.

Repeat for C5220.

Post each measurement.

[brockauly]

C5260 2.2ohm
C5220 2.5ohm

resistance of probes when short-circuited : 0.2ohm

[mon2]

These looped current resistors are ok and match the schematic values for each.

Test the dual mosfets @ Q5230 and Q5240 using the resistance check method to confirm they are not shorted.

You will need to test the resistance across:

source / drain
source / gate
gate / drain

of each dual mosfet. Be sure to test both mosfets inside the one package. Each should be hundreds of k ohms or higher if the mosfet is ok.

[brockauly]

All are at least 3Mohm. I couldnt test two out of the four gates because the testpoint is unreachable with my probes. Q5240 pin 1 (CHGR_GATE_Q4) & Q5230 pin 8 (CHGR_GATE_Q2)