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Repair guides and disassembly information for the 14-inch MacBook Pro released in October of 2021, featuring Apple-designed M1 Pro and M1 Max SoCs. Model A2442.

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Broken battery data cable or firmware problem?

HI, I recently cleaned the area under my touchpad (had a small liquid spill and I wanted to make sure, that nothing went too far into the body). For this I had to remove the battery data cable and reattach it.

Now my laptop only starts when I connect it to power and it does not use the battery at all (e.g. when I disconnect the power cable, it goes off immediately, the startup date and time is 1 April, 00:00, etc.). The battery indicator shows 67% charge, it seems to able to read information like the total capacity, but it does not charge (remaining time to full is always 00:00). I immediately suspected the battery data cable, since during the insertion I had to bend it a bit and I was afraid I broke it.

I tested each of the six lines with a multimeter to check if I had broken any connections and indeed the fourth line (counting from the left) did seem to be broken. I ordered an aftermarket replacement and it arrived today, but it did not help. I again checked each line and again the same line was broken. Now I wonder, if that is suppose to be the case and I am actually having some kind of firmware/battery initialisation problem. I tried to find instructions to reset the SMC, but for Apple Silicon MacBooks a simply power cycle should be enough.

Am I missing anything?

Update (05/08/24)


here is the screenshot from CoconutBattery:

Block Image

The data seems accurate, so I assume the system can read the battery information. I am not sure, if there is more you would like to see?

I will try to follow the suggestions RipperDoc made. For some measurements I think I need to get better tools (my multimeter was hardly able to measure the pins on the cable...).

Answered! View the answer I have this problem too

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Chosen Solution

Hi all,

thank you very much for all the suggestions, that was very helpful and I learned a bit more about how the power and battery is managed in my MacBook. I had to do some important work in the meantime, so I kept my MacBook running on external power and I also saw the battery level going down slowly (67%-63% in the last week).

I was actually not so sure, if my logic board was affected, since the liquid did not even make it around my trackpad. Today, after downloading and studying the schematics, I decided to retrace my steps and after loosening the battery to logic board connector I found a dust/dirt particle on one of the pads on the battery. After blowing it away and reconnecting everything (I had to connect an external charger at least once), it worked again.

Now my battery is charging full speed and everything seems fine.

Thanks again for all the help!

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Most Helpful Answer

pin 4 is irrelevant for the battery.
if you do not have boardview (easy to find on google if you look for board number 820-02098 bvr, use openboardview or flexbv free version to open), 6th pin is closest to trackpad connector
1. battery does not output voltage unless pin 1 on bmc cable is not connected to ground.

once you connect external power, it powers up some always-on power lines. one of such lines constantly turns on a MosFet which connects SYSTEM_DETECT_L to ground and activates battery. once battery is active, it will keep this MosFet on by its own.
2. battery should communicate once per second via SDA / SCL SMBUS line, pins 2 and 3. if you have good multimeter you will be able to see 3.3v slightly fluctuating on both pins. some cheaper multimeters will be able still to see such fluctuating in AC mode.
3. working charging circuit will pulse 6V to the battery if it is not coonnected to "wake" it. deeply depleted battery wont be visible on SDA SCL communication line but this pulse will be able to turn its controller to be readable by SMC

so using this 3 facts it is easy to troubleshoot why your mac is not working from battery.

1. measure voltage on disconnected battery output while mac is connected to charger. normal behavior of pulsing voltage indicates working charging circuit and working battery switch MosFET (Q5265)
2,. measure voltage on battery output with BMC cable connected.
normal value would be 11.5,...,12.9V slowly rising as macbook charges the battery.

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Let’s see what CoconutBattery tells us with everything connected. Post a snapshot of the Apps main here so we can see it as well.

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@ductng - Clearly SMC is getting the batteries data from the Batteries BMC logic. I don’t think the battery cable is your issue.

Your system should be charging right now as the batteries temp is not elevated and the power level is low enough. We can also see there is a charger connected.

That leads us to an issue within the logic boards charge control logic. As you had liquid intrusion I’m suspecting the logic board did get wet from what ever spilled causing damage. At this point you need to fully remove the logic board to do a careful expection of the other side.


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Duc Bao Ta will be eternally grateful.
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