820-2850-A: battery not detected

[DrFalken]

Re: 820-2850-A: battery not detected

Replace U7000. These pins should not be 0V and pretty sure these pins are from an internal LDO that feeds from pin 2 as the input voltage.

If U7000 has been replaced or was faced with possible liquid damage, consider to flux and reflow the part to test again. Fairly inexpensive part from Aliexpress or other sources.

I'm replacing it again, maybe is defective or not perfectly soldered.
Will report very soon

[DrFalken]

Re: 820-2850-A: battery not detected

U7000 replaced, F7040 still removed
AC Adapter only (no battery) readings:
F7040 pad #1 = 12.54V dropping to almost 4V in 4-5 seconds then rising istantly to 12.54V and dropping again to 4V... (cycle)
F7040 pad #2 = 0.5V

[DrFalken]

Re: 820-2850-A: battery not detected

Put back F7040:
F7040 pad #1 = 12.54V
F7040 pad #2 = 12.54V
Solid green on the AC adapter and the fans started on their own

Laptop is booting now ! Thank you @mon2 !!!
Monday will check if the battery charging works and report back.

[DrFalken]

Re: 820-2850-A: battery not detected

Last minute update: the battery isn't yet detected.
What can I check monday ?

[mon2]

Re: 820-2850-A: battery not detected

Last minute update: the battery isn't yet detected.

Excellent on the update.

Do you see the battery charging symbol once you boot up normally ?

Does the battery have enough charge to operate the logic board (without the power adapter) ? Respectively, can this unit operate without the adapter (battery only) ?

If the battery is not detected, need to check on the I2C bus used to communicate with the battery pack. This is where D6950 is involved again.

With the adapter & battery connected - post the voltages on Q7055.

Post all voltages on the battery connector.

[DrFalken]

Re: 820-2850-A: battery not detected

Excellent on the update.

Do you see the battery charging symbol once you boot up normally ?

Does the battery have enough charge to operate the logic board (without the power adapter) ? Respectively, can this unit operate without the adapter (battery only) ?

If the battery is not detected, need to check on the I2C bus used to communicate with the battery pack. This is where D6950 is involved again.

With the adapter & battery connected - post the voltages on Q7055.

Post all voltages on the battery connector.

When I turn on with both battery and AC adapter there is an X on battery icon and isn't detected even on System information (see attached pic).
Magsafe led is solid green, never turn orange.
I think that the battery is empty, anyway I've tried battery only and laptop doesn't turn on (SIL blinking 5 times pressing check button).

Removed motherboard from chassis and connected battery only:
Q7055 pin #1-3 = 10.92V
Q7055 pin #4 = 3.96V
Q7055 pin #5 = 10.92V

Added AC adapter:
Q7055 pin #1-3 = 11.19V
Q7055 pin #4 = 4.69V
Q7055 pin #5 = 12.18V-12.20V

Suddenly, when I've plugged in AC adapter to measure voltages, the logic board turned on, fans spin at maximum speed and Magsafe led turned solid orange
After 2-3 minutes the Magsafe led turned solid green again and the fans are still at maximum speed.

J6950 readings in this moment (AC+battery, fans @max speed):
pin 1-2-3: 11.19V
pin 4: 3.38V
pin 5: 0
pin 6: 3.39V
pin 7-8-9: 0

Removing AC adapter the battery keeps powering the logic board (fan still @max speed): I suppose the battery charged a little bit.
Will put logic board back on chassis and report.

[mon2]

Re: 820-2850-A: battery not detected

Flux and carefully remove D6950 off the logic board. It is a very tiny part.

Test again.

[DrFalken]

Re: 820-2850-A: battery not detected

Flux and carefully remove D6950 off the logic board. It is a very tiny part.

Test again.

I've just put everything back, same issue (Magsafe led solid green, battery not detected)

Turned off.
Lifted battery keeping connected the battery cable to motherboard, plugged Magsafe and his led turned orange.
Turned on Macbook, now there's a little flash symbol over the battery icon: booting MacOS the battery is detected and now charged @ 8% (see attached pic)
I'm suspecting some bad connections between battery cable and J6950...
(charge is 14% in this moment)

[mon2]

Re: 820-2850-A: battery not detected

Very good. Do the pram reset to reset the parameters.

[DrFalken]

Re: 820-2850-A: battery not detected

Very good. Do the pram reset to reset the parameters.

Done but has the same behaviour.
When I put back the battery doesn't get recognized.
When lifted get detected and charged.
99% confident it's a connector (battery or logic board side ?) problem.
I'll further investigate starting from J6950's pins 4-5-6.

[DrFalken]

Re: 820-2850-A: battery not detected

Double checked J6950's pins 4-5-6 and also resoldered, same issue.
Currently the battery has a 100% charge.
The battery is detected and charged only when is lifted and the Macbook is able to turn on without AC adapter (battery only)
Conversely, when the battery is mounted in its seat Macbook turn on only with AC adapter (after is turned on I can unplug Magsafe and keeps working only with battery but doesn't detect it)
Could be battery issue ? (cable or plug)
Don't have another battery to check...

[mon2]

Re: 820-2850-A: battery not detected

Sounds like a contact / connector fault with the:

pin 4: 3.38V
pin 5: 0
pin 6: 3.39V

Since the battery is able to power the logic board when the magsafe is unplugged, the battery detection pins are the only factor. Review the above 3 pins.

[DrFalken]

Re: 820-2850-A: battery not detected

Sounds like a contact / connector fault with the:


Since the battery is able to power the logic board when the magsafe is unplugged, the battery detection pins are the only factor. Review the above 3 pins.

I've checked them on motherboard side, both under microscope and continuity mode
- J6950 pin#4 - R5281 pin#2
- J6950 pin#5 - R6980 pin#1
- J6950 pin#6 - R5280 pin#2
and are ok.

Also:
- J6950 pin#5 (SYS_DETECT_L) to GND = 9.86 KiloOhm


On the battery side (battery not connected to motherboard) voltages are:
- pin #4 - pin #9 (GND) = 0
- pin #5 - pin #9 (GND) = 0
- pin #6 - pin #9 (GND) = 0

[DrFalken]

Re: 820-2850-A: battery not detected

Last update: I've ordered a brand new battery, yesterday arrived and it's correctly detected without any issues.
Now it's fully charged.
Looks like the previous one was faulty or damaged.
Again, thank you @mon2 for everything !!!