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Strange power/battery/charging issue with 2011 17" MBP!

Sharky II

macrumors 6502a
Original poster
Jan 6, 2004
United Kingdom

I’ve been given a 2011 17” MBP with good specs: Quad Core i7 2.3GHz, 16GB RAM, 500GB SSD. I’m trying to fix it for someone who is not able to afford to fix it themselves and needs help - I want to fix it and give it back to them to use, or sell it and give them the money.

It’s in perfect cosmetic condition, but the problem is that the battery doesn’t seem to ever get charged (the machine does not boot without the power plugged in), and the performance is extremely slow when it boots. It has a new, 3rd party battery, coconut battery pic attached.

A couple of days ago, the machine was booting (enabling me to get the photos below and see which processes are running) - but currently the machine is caught in a cycle of wanting to boot, then shutting down just as you get to the login screen, then booting again. I believe this machine is from an era where it boots up automatically when power is attached, which is why it keeps booting up again, randomly.

When it does/did get to the is the kernel_task process which is taking up all the CPU (I assume this is a power management issue due to having 'no battery attached'?), however the machine is not getting hot. It’s just very slow.

Things I’ve tried:
  • Multiple PRAM Resets
  • Multiple SMC Resets
  • Different Chargers (all genuine 85W)
  • Reseating battery connector
  • Air-blasting battery connector and logic board
  • Booting without battery connected (same performance issue)
  • Looking at Coconut Battery app. Photo is attached.
It looks like the battery is third party, however the performance is bad with the battery disconnected.

I have not removed the logic board yet.

Can anyone recommend some troubleshooting steps to try to figure out what the problem is? I'm hoping that it might be the small magsafe 'daughter board', or something like that (i.e. replaceable).

This is still a very nice/capable laptop and I'd like to rescue it for the owner, if possible - any help would be appreciated!




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Sharky II

macrumors 6502a
Original poster
Jan 6, 2004
United Kingdom
Thanks for your feedback

Yes, I figured that would be the case (about the CPU throttling). I guess I need to find a way to figure out if it's the logic board or the battery, preferably without simply buying another battery to find out (and then having 2 healthy but useless batteries!).

Obviously the worst case scenario is that the logic board is 'bad'.

I was also wondering if it's possible that the small magsafe 'daughter board' is the culprit.... I have a half dissected 2010 MBP lying around, i wonder if the magsafe board is the same on both machines? That way I could swap them around and have a try.

However, the best case scenario would be that it's the battery.

Is anybody able to suggest some tests that would enable me to have a bit more confidence in this, before shelling out money for another battery?



Edit: As an update, I just disconnected the battery and tried to start the MBP, and it worked (albeit extremely slowly). With the battery connected, it would often restart half way through booting up. This is a little bit of evidence that the battery may be at fault here.
Last edited:
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