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Lanzado en julio de 2018, el MacBook Pro de 15", modelo A1990, presenta una pantalla de retroiluminación LED de 15.4 pulgadas con tecnología True Tone, TouchID y hasta 6 procesadores Core i9.

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Multimeter - low battery voltage, dead laptop

Hi

My Mac suddenly stopped turning on after I came from holidays.

I expected it was faulty battery because for the last few months there was a warning in MacOs saying about recommended battery replacement. Also the laptop had huge issues with overheating, the funs were often running with full speed.

For this reasons I decided to replace the battery with the iFixit one, but the Mac still does not turn on. I visually inspected the motherboard for any issues but there is nothing worrying. There was no liquid damage for sure. Laptop was just sitting for the last 5 days not being used which is even more mysterious.

However I noticed when I check the voltage for the new battery with multimeter using the two gold connectors I get 0.1 V. I would like to understand if it's normal ? For comparison I did check the old battery and it was showing similar value so I assume that might be a normal thing?

Secondly do you have any recommendations what else could be tested? I'm happy to take risk as the laptop is dead anyways and I did recently a backup.

I did try

  • Run Mac without battery
  • Reset SMC
  • Tried different chargers
  • Connect to charger for a day
  • Reassemble everything 2 times checking the cables and connectors

Thanks!

New iFixit battery

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Old battery ( removed from laptop)

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Solución Elegida

I've solved the problem.

The issue was not the battery, and still not sure why the multimeter does not show the max voltage when checking the battery.

I checked the logicboard carefully again and noticed a little bit of corrosion on the right side of the board, close to the air intake. Then I checked the logicboard schema and found a capacitor that looked a bit corroded, which was C9081 (it was very hard to see that without a proper microscope). I checked with a multimeter if the capacitor was shortage to the ground, and it turned it was. But same as all the capacitors close to this one, so I was not 100% sure if that one was faulty.

I did google for the capacitor C9081 and found this video https://youtu.be/NXCU4LpeQUA?si=1fSR-vQA.... The person described that this is a common problem for MacBook 2018/2019 because of moisture and dust close to the edge of the board.

I was surprised the guy recommended removing the capacitor instead of replacing it... I did not have much to lose, so I took the risk and just removed the capacitor from the board; after removing it, there was no more shortage of the other capacitors, which was promising.

It turned out this fixed the problem; the laptop works, and it is much quieter because I also replaced the old thermal paste (which was dry) for CPU and GPU. For the CPU, I used liquid metal instead of thermal paste ( highly recommended if your laptop is overheating as it would throttle your CPU and drains your battery faster which in long run would cause a faster degradation of the battery)

I'm not quite sure if there is any side effect in removing the capacitor, but on the other hand, I don't have experience with soldering SMD and the laptop works without any problems. I would appreciate it if anyone with more expertise in electronics could say something more about this.

I don't recommend anyone who reads this post to do the same if their Mac does not turn on unless they know how to fix electronics. It worked for me; I had a backup of my data, and I did not have much to lose, I was close to buying a new Mac.

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In my recollection, those do not always run without the battery connected, you might get trackpad click though, or a low battery logo on screen.

I will also say, it may not be that the laptop was overheating. The fans may have been running heavily as well if the battery had failed. If the Mac detects that sensor data from the battery is missing, it will ramp the fans up to compensate as a safety.

Either way, it sounds like the new battery isn't charging. You should be getting well above that. More in the neighborhood of 11, even if the battery was low. The battery itself is rated for 11.4 V, but a fully charged battery would likely exceed that. Based on your descriptions, I would expect the old battery to read as 0.1V, but not the new one.

Seems like you may have gotten a dud battery. I would get in touch with iFixit's support team and see if they can sort you out.

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Thanks for the answer,

I will check with support

I'm thinking there might be some voltage regulator that is controlled by board and when the laptop is off it would not give the max voltage. I could not find on the Internet what is the proper way to check the battery voltage for Mac. I also don't have any working Mac to compare.

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@mariusz86 Based on your pics, you measured correctly.

The thing with Lithium Ion batteries like this is that they also need a certain amount of power to wake from sleep/hibernation. When the battery is in disuse for some time, it goes into a “sleep” mode. If there isn’t enough power in the battery cells to wake the battery board back up when it’s needed, then the new battery could actually be totally fine, but is too depleted to be of use and can’t charge because the battery management board is unpowered.

So it’s a weird catch 22. Doesn’t have enough power to wake up, can’t get enough power to wake up because it’s asleep. A replacement battery seems like the likeliest fix to me, but keep us posted.

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