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Released in May 2020, the 13" MacBook Pro features quad-core Intel 10th generation Core i5 and i7 processors, and Intel Iris Plus integrated graphics. (Model A2251/EMC3348 with four Thunderbolt 3 ports)

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Battery replacement ISSUE - VERY slow performance and doesn't hold chg

So....

I just replaced my battery and everything seemed to go well... except not. My mac is now really really really slow (when plugged in) and shuts down the moment I disconnect the power.

I can't even run the system diagnostic (D on startup) because I cannot get past the wifi password question (hangs). That said I can boot the system up, it just takes at least 20 min AND clicking ANY menu items takes about 2 minutes.

PLEASE HELP.

Update (12/02/25)

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Update (12/15/25)

So... I got a new battery and same issue. :-(

Answer this question I have this problem too

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Are you able to download stuff from a second Mac? Hopefully you can get this App CoconutBattery and then using a USB-C Thumb drive to transfer it to your Mac or just run it from the drive. Take a snapshot of the Apps main screen and post it here so we can see what's happening.

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15 Comments:

I can and will try this. BTW should I be able to read voltage across the battery? I'm not getting any unplugged.

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@gregalbrechtsen - At this point I'm not sure as we don't know if the power from the charger is getting to the battery and now the battery is discharged by use and can't charge. CoconutBattery offers a deeper view into the battery that Apples diagnostics or even the Systems Battery info.

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ok.. easy report from Coconut..

"NO Battery Found"

yikes..

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@gregalbrechtsen Double check that everything is connected correctly, iif no battery is found it maybe simply be not connected fully.

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@gregalbrechtsen I would investigate your data flex from the battery to the board. Make sure both sides of that Zif connector are latched in place well too and that there are no tares in that flex cable.

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It sounds like your Mac isn’t recognizing or communicating properly with the new battery. When a replacement battery isn’t detected, macOS may throttle performance heavily to protect the system, and it will shut down the moment power is unplugged. This often happens with incompatible or faulty third-party batteries, or when the battery connector isn’t seated correctly. Try resetting the SMC, reseating the battery connector, and checking CoconutBattery to see if the system detects it at all. If it shows “0%” or “Service Battery,” the replacement is likely defective.

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Greg Albrechtsen will be eternally grateful.
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