820-00840 dont see the battery

Hi all!

I have 820-00840 board after liquid damage, the board was not starting but after some good clean it does start and but, seams to work as expected, how ever say the that the battery is not installed.

Any tips about where to start looking?
Unfortunately i dont have any spares battery for this one to try it out 😔

PPBUS is at 13.08v, and it take 300-700 ma
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Little update, battery connected, charge cable connected -> have 3.4 (pulsating) on SMBUS_SMC_5_G3H_SCL and SMBUS_SMC_5_G3H_SDA
However nothing on SYS_DETECT_L (not sure what it should be, still looking)

Battery connector ( disconnected from the board) shows only 1.6v
Thats lead me to bad battery. But not sure whay it say that it is not installed in system?


Staff member
Did you tight the special screw for battery power connector?
SYS_DETECT_L must have 0V; be sure R6950 is good.

If battery electronics circuit was affected by liquid, need to replace the battery.
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Yes the screw is tight
R6950 is 10kom as specified

The battery circuit dont look like being touch by liquid.. any ways to restart the battery?


Staff member
0.350 and 0.359 is not the same here!
Less than 0.5% diference usually for these lines.
If good, must check the machine with known good battery.

BTW, stop checking diode mode (nor resistance) with battery, or any other kind of power on the board.
Thank @2informaticos!

Will order a battery and try it out.

By the way, is battery from 820-01598 tha same? Can i try with this one? Seems to have the same connector but not sure if its the same pinout
Strange, when i connect the battery from 820-01598, the board does not start and i see the voltage start to go up from 5v and then the power supply shuts down and restart from 5volts and it does it in loop.. does that mean the board is not okay then?
Not sure, i will wait until i receive the replacement one (ordered with the palm rest since the keyboard is scrap as well) because 01598 board does not easily fit in to 00840 case.
I guess they blocked the compatibility on the software level...

By the way, screens are compatible between those two?
Ok, received the replacement battery(used, supposedly good), and i am getting the same behavior - voltage cycling from 5 to 0... with out a battery all start and work...

Any thoughts?

Compared diode mode reading on SDA/SCL with a board that do charge a battery just to be sure - same readings on both...
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Thank you @2informaticos
Thats exactly what i thought... so i switched the board around and unfortunatly i plugged shorted trackpad in tho the board with battery issue... not too long after i smelled burned L4800 😅
Well i guess its good, because if it was the repaired board with the wire bypass, who knows what could burn this time..
Anyways, the battery story become more and more strange:if i switch the board around, both seams to take some charge but the board with water damage do not want to start in the second mac( first it started and was staying on mac logo screen, now there is no life at all) but it take 20v 1.2amps.
The second board (witch had trackpad issue) does take 20v but stays at 0.23amp...
It does not start with the other screen connected aswell.. i guess maybe its deferent years..
Then i switched them back again just to be sure and its back to the same behavior then before... super strange...
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Staff member
1.2A is too much current for a board in off state; unless battery is connected and charging.

We should focus on one board at a time; must avoid any confusions...
Yes, 1.2amp was with battery connected.
Anyways, after playing some more and swaping around boards, the machine finally see the battery and work as expected. Still not sure what did that.

Will have to fix the burned L4800 on this one too how ever. What kind of wire would it take? How can i be sure that the issue wont come back?
Should i try to clean the board in ultrasonic or i can just live it the way it is since its all working? (Dont have my ultrasonic yet)


Staff member
Forget the UC; it should be used only when you note large (and many) areas affected by liquid.
Small corroded areas, as flux elimination too, must be done with toothbrush and alcohol.
No need to pass through UC, if board works good now.

To bypass L4800, use 0.03-0.1mm magnet wire.


Staff member
The enamel gets burnt in few seconds with the solder iron.
You don't need to clean entire wire, just its terminals for soldering.