Why does MacBook Pro 15" Unibody hibernates randomly when on battery?

I bought a second hand Macbook Pro (late 2008/2009 Unibody) recently that hibernates randomly whenever it's on battery.

It can happen very soon (a minute or two) after running the computer on battery, so I don't think it is a heat related issue.

When it is on AC power, the computer stays on and charges the battery fine.

When you press the power button to turn it back on, it comes back with the same screen with the progress bar, so it looks to be restoring from hibernation/deep sleep.

I have tried resetting the SMC, doing a PRAM reset also, but to no avail.

The health of the battery isn't great, but I've tried the battery on my old Macbook Pro (same model) without any problems. I also tried putting my good battery from my other computer in and the same thing would happen.

When I bought the computer it had Mavericks installed, so just to be safe I tried putting my hard drive from my old computer in which is on Mac OS Snow Leopard and still the same problem would happen.

It doesn't seem to make a difference if battery is fully or partially charged.

This machine is 2.8 GHz machine. It runs quite hot, but so does my 2.66 GHz machine. I do know the previous owner did spill wine on it, and had to replace the keyboard. The keyboard works fine by the trackpad requires a lot of pressure to click it. Not sure if this may also affect the hibernation issue!

My suspicions:

- Bad battery connector?

- Bad logic board or charging module?

- Faulty SMC sensor?

Any help would be great! :)

Answered! View the answer I have this problem too

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I would check the Battery Indicator Cable (the cable that goes from the logic board to the battery charging status board (green lights). It's a fragile cable that can be damaged by the battery screws. The cable also has something to do with the computer sleep function.

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Thanks for your response, Lemerise!

I have put the motherboard in another (older machine) and it seems to work fine now. So I am most suspicious of either the battery connector or indicator cable as you mentioned.

The only problem with this older case is the screen has a horrible black band that comes down one side of the screen once it heats up! So it's a case of out of the frying pan and into the fire.

Am hoping to swap the screens if I can only get past these stripped torx screws... why is nothing easy?!

Thanks again, Lutfi

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Lutfi Hady will be eternally grateful.
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