Macbook Pro is randomly rebooting

Cooper622 wrote:

J. The battery in the MBP is completely shot, would that be the sole reason for my reboots?

I would say that is an excellent guess.

Start there an eliminate the obvious/easiest and see if it resolves the issue.

DIY Battery Replacements for Apple MacBook Pro ... - OWC

Have you tested it in Safe Mode? The computer's battery and/or AC adapter needs replacing. My guess is the battery is the reason it dies when disconnected from the charger. However, if the charger isn't working, then the battery is not charged. Unfortunately, that model is obsolete meaning Apple no longer has parts for it. If the problem is on the motherboard you cannot get it repaired by Apple.

About Using Safe Mode

• Use safe mode to isolate issues with your Mac - Apple Support
• Playing Safe- what does Safe mode do?

A Troubleshooting Procedure that may Fix Problems with macOS El Capitan or Later

You should try each, one at a time, then test to see if the problem is fixed before going on to the next.

    Be sure to backup your files before proceeding if possible.

1. Shutdown the computer, wait 30 seconds, restart the computer.
2. Disconnect all third-party peripherals.
3. Resetting your Mac's PRAM and NVRAM
4. Reset the System Management Controller (SMC)
5. Reset your Startup Disk and Sound preferences, if needed, after resetting the PRAM.
6. Test in safe mode to see if the problem persists, then restart normally.  Use safe mode to isolate issues with your Mac and Playing Safe - what does Safe mode do?
7. Repair the disk by booting from the Recovery HD. Immediately after the chime hold down the Command and R keys until the Utility Menu appears. Choose Disk Utility and click on the Continue button. Select the indented (usually, Macintosh HD) volume entry from the side list.  Click on the First Aid button in the toolbar. Wait for the Done button to appear. Quit Disk Utility and return to the Utility Menu. Restart the computer from the Apple Menu.
8. Repair permissions on the Home folder: Resolve issues caused by changing the permissions of items in your home folder.
9. Create a New User Account Open Users & Groups preferences. Click on the lock icon and enter your Admin password when prompted. On the left under Current User click on the Add [+] button under Login Options. Setup a new Admin user account. Upon completion log out of your current account then log into the new account. If your problems cease, then consider switching to the new account and transferring your files to it - Transferring files from one User Account to another.
10. Reinstall OS X by booting from the Recovery HD using the Command and R keys. When the Utility Menu appears select Install OS X then click on the Continue button.
11. Erase and Install OS X Restart the computer. Immediately after the chime hold down the Command and R keys until the Apple logo appears. When the Utility Menu appears:

     1. Select Disk Utility from the Utility Menu and click on the Continue button.

     2. When Disk Utility loads select the drive (out-dented entry) from the Device list.

     3. Click on the Erase button in Disk Utility's toolbar. A panel will drop down.

     4. Set the Format type to APFS (for SSDs only) or Mac OS Extended (Journaled.)

     5. Click on the Apply button, then wait for the Done button to activate and click on it.

     6. Quit Disk Utility and return to the Utility Menu.

     7. Select Install OS X and click on the Continue button.

MacBook Pro models use up to all the power available from the Power adapter, and also "borrow" freely from the battery under heavy loads, on a moment-by-moment basis. Running an external display can be a heavy additional load, depending on the display.

If the battery can supply nothing additional, it is possible to overdraw the available power, which makes the voltages start to collapse. If this happens, your Mac will do an Emergency Power-down to save itself from damage. Such a power-down will seem "instant", it will not linger for even a few seconds.

Well, the best way to try and pin down the cause is to follow a troubleshooting procedure. Here is one I put together. The idea is to try and isolate a potential cause by starting with something simple and ending up with an Erase and Install if the problem cannot be isolated.

A Troubleshooting Procedure that may Fix Problems with macOS El Capitan or Later

You should try each, one at a time, then test to see if the problem is fixed before going on to the next.

    Be sure to backup your files before proceeding if possible.

1. Shutdown the computer, wait 30 seconds, restart the computer.
2. Disconnect all third-party peripherals.
3. Resetting your Mac's PRAM and NVRAM
4. Reset the System Management Controller (SMC)
5. Reset your Startup Disk and Sound preferences, if needed, after resetting the PRAM.
6. Test in safe mode to see if the problem persists, then restart normally.  Use safe mode to isolate issues with your Mac and Playing Safe - what does Safe mode do?
7. Repair the disk by booting from the Recovery HD. Immediately after the chime hold down the Command and R keys until the Utility Menu appears. Choose Disk Utility and click on the Continue button. Select the indented (usually, Macintosh HD) volume entry from the side list.  Click on the First Aid button in the toolbar. Wait for the Done button to appear. Quit Disk Utility and return to the Utility Menu. Restart the computer from the Apple Menu.
8. Repair permissions on the Home folder: Resolve issues caused by changing the permissions of items in your home folder.
9. Create a New User Account Open Users & Groups preferences. Click on the lock icon and enter your Admin password when prompted. On the left under Current User click on the Add [+] button under Login Options. Setup a new Admin user account. Upon completion log out of your current account then log into the new account. If your problems cease, then consider switching to the new account and transferring your files to it - Transferring files from one User Account to another.
10. Reinstall OS X by booting from the Recovery HD using the Command and R keys. When the Utility Menu appears select Install OS X then click on the Continue button.
11. Erase and Install OS X Restart the computer. Immediately after the chime hold down the Command and R keys until the Apple logo appears. When the Utility Menu appears:

     1. Select Disk Utility from the Utility Menu and click on the Continue button.

     2. When Disk Utility loads select the drive (out-dented entry) from the Device list.

     3. Click on the Erase button in Disk Utility's toolbar. A panel will drop down.

     4. Set the Format type to APFS (for SSDs only) or Mac OS Extended (Journaled.)

     5. Click on the Apply button, then wait for the Done button to activate and click on it.

     6. Quit Disk Utility and return to the Utility Menu.

     7. Select Install OS X and click on the Continue button.

Cooper622 wrote:

I replaced the battery and I've been solid all week. Displaying to my external monitor and all.

Good computing Cooper622 ! Thanks for the report.

Visit OWC and see if they don't have a replacement battery for your model. If they do, then you can replace the battery yourself. They even include required tools. The job is pretty easy.

If the battery has gone bad, then the moment you remove the charger the computer will shutdown. However, if the charger is connected and is not defective in some way, then replacing the battery will not likely stop random reboots under normal load conditions. A non-functioning or missing battery will result in the processor throttling down to avoid problems related to the battery supplementing the charger's power when needed. You will notice that the clock speed for the processor is reduced by half.

However, none of this would seem to be at the heart of a computer randomly rebooting unless the processor is under heavy load, in which case, and given other conditions the processor executes a shutdown to prevent damage.

The migration process is throttled back to mundane by the speed of the source drive, typically a rotating magnetic drive that just can't produce data very quickly.

In terms of power load, adding an external display is FAR more of a load that migrating files for 12 hours.

You can't "guess" that a bad file is the source of your problems. it almost never is. And when it is, the symptoms do not match what you are reporting.

late 2011 15-in MacBook Pro running High Sierra.

sleep/Wake failure.

Any reports nearby with Date&Time and ending in .panic?

or screen going blank or black or freezing?