MacBook Pro shuts off instantly when unplugged despite a healthy battery

Minor issues: [sic]

SSD too slow - SSD is showing poor performance.

Performance:

System Load: 2.02 (1 min ago) 2.09 (5 min ago) 2.00 (15 min ago)

Nominal I/O usage: 0.13 MB/s

File system: 86.11 seconds

Write speed: 204 MB/s

Read speed: 1074 MB/s

Properly functioning drives on modern Macs Write speeds are comparable of even slightly better than Read speeds (because of buffering on writes) your drive may be failing.

if you have not recently restarted in Safe Mode, that is the easiest thing to do that incorporates a disk check as it starts up.

Start up your Mac in safe mode - Apple Support

If using a Mac with Apple silicon

1. Shut down your Mac.
2. Press and hold the power button on your Mac to turn on your Mac and load startup options. When you see the startup options window, release the power button.
3. Select your startup disk. It's named Macintosh HD, unless you changed its name.
4. Press and hold the Shift key, then click the “Continue in Safe Mode” button below your startup disk.
5. When you see the login window, you might also see “Safe Boot” in red text in the upper-right corner of the login window. Log in to your Mac. You might be asked to log in again.

your MacBook Pro with only 8GB RAM and only 128 GB drive is severely limited.

Apple no longer sells ANY Macs with only 8GB RAM. Your 128 GB drive is also limiting.

if you find major issues, I recommend you either:

• run an older version of macOS, such as Monterey, if possible.

• consider trading-in or abandoning this Mac for a more capable Mac. I would NOT recommend spending money on this unit.

no Time Machine or other local, disk based backup is showing.

If you do not have a recent local, disk-based backup, your computer is like a ticking Time bomb. You are only one disk failure, one mainboard failure, one crazy software, or one "oops" away from losing EVERYTHING! Drives do not last forever. It is not a question of IF it will fail, only WHEN it will fail. In addition, you never know when crazy software or Pilot Error throws away far more than you intended.

If you are using another direct-to-disk backup method that you prefer, and you currently have a recent disk-based backup, that is great. If not, you should consider using Built-in Time Machine. Take steps to acquire an external drive as soon as possible. If you buy one, a drive 2 to 3 times or larger than your boot drive is preferable for long term trouble-free operation. Do not pay extra for a drive that is fast.  (You can get by for a while with a "found" smaller drive if necessary, but it will eventually become annoying).

Attach your external drive and use

Settings > General > Time machine ...

... to turn on Time Machine and specify what drive to store your Backups on.  It may ask to initialize the new drive, and that is as expected. APFS format is default format if running MacOS 11 Big Sur or later.

Time machine works quietly and automatically in the background, without interrupting your regular work, and only saves the incremental changes (after the first full backup). Time machine backs up your machine — including every connected drive that is in a Mac compatible format. it can not back up Windows format drives.

Time Machine's "claim to fame" is that it is the backup that gets done. It does not ruin performance of the rest of the computer while doing its backup operations. You do not have to set aside a "Special Time" when you only do backups. When you need it, your Time machine Backup is much more likely to be there.

How to use Time Machine to Backup or Restore your Mac:

Back up your Mac with Time Machine - Apple Support

Time Machine may spend all afternoon making your first full backup. You can continue to do your regular work while it does this. The first Full Backup is by far the biggest backup.

A deeper repair of the boot drive is possible using Internet Recovery. It was not pushed to the front because safe mode is much simpler.

You will want to Invoke Recovery using the Internet, so you will hold Command-Option-R at startup:

How to start up from macOS Recovery - Apple Support

Using the following more detailed article, Scroll down to the section labeled:

"Repair your computer’s internal storage device "

How to repair a Mac storage device with Disk Utility - Apple Support

as directed, elect "show all devices".

then repair:

each and every Volume, then

each answer every Container, then

the Physical device.

all should report no issues, else repair that item again before proceeding to the next.

--------

'MacOS Base System' is the Disk Image of the stripped-down MacOS that is running Internet Recovery. 'MacOS Base System' is locked, so it can't be repaired. 'MacOS BaseSystem' also creates about 30 RAM-disks for temporary storage, leaving the boot drive Completely free for a Deep Repair.

if you can't get Internet recovery to GO, then you can use regular Recovery, which runs from a disk image on the Boot drive itself, but has slightly more restricted repair abilities.

As a follow-up to Grant's SSD observation: a NVME SSD in that Macbook Pro model should have Read and Write speeds over 2000 MB/sec. Yours is showing mechanical HD speeds.

I also recommend a safe mode boot. I would add to let the come "soak" in Safe Mode for 20-30 minutes before restarting normally in case it needs time to fix issues.

runbluemaddy wrote:

MBP 2019 Intel Quad-Core i5

8GB

Sequoia

My MBP has started to only work when on mains power. If the power lead is removed the machine powers off immediately. It will not switch on unless mains powers is connected.

The battery is good and was replaced by Apple in Feb 2025 and has 96 cycles. The logic board was replaced at the same time as a fault was found with this.

The machine was working perfectly and then it started to power off (when on battery) at random times. This has now escalated to only working as described.

Any help appreciated - This seems to be a common issue that has been around for years.

Thanks.

Get help with your Mac notebook battery

Learn how to optimize the life of the battery in your Mac notebook, fix battery issues, and get service.

If you see Service Recommended on your MacBook Air or MacBook Pro - Apple Support

In or out of warranty you can get a free over the counter 'Apple Service Diagnostics' test /assessment

Make an appointment for a "hardware issue"

Genius Bar Reservation and Apple Support Options - Apple

Outside the USA

Contact Apple Support - Apple Support

One thing you can try at home is a reset of the SMC. The SMC is responsible for managing power on your Mac. Resetting it can resolve certain issues related to power or thermal management. Resetting the SMC may be a step to resolve issues that could be power related.

Follow the steps appropriate for your Mac model. You may need to do this a couple times:

How to Reset the SMC of your Mac - Apple Support

Consider downloading and running this little "discovery" utility, Etrecheck. It changes NOTHING. Etrecheck was developed by a senior contributor here, and uses mostly system calls and simple tests to collect often-needed information.

it contains little tests for speeds of devices, CPU utilization, memory usage, energy usage and a digest of recent problems, in one easy to use package. it does not even need to be Installed. Because less can be learned when your Mac is running great, best time to run is when your problems are actually occurring, if possible.

if you follow the directions faithfully, its report (pre-laundered of all personally-identifiable information) can be "Shared" to the System ClipBoard, then Pasted into an ‘Additional Text’ window in a reply on the forums.

Use Etrecheck Pro for free:

http://Etrecheck.com

The amount of data you get can be daunting. If you POST your report, some Readers here are willing to look over those reports, and can provide valuable insights.

Then start a reply on the forums, click the 'additional text" icon, and PASTE

Grant Bennet-Alder wrote:

• consider trading-in or abandoning this Mac for a more capable Mac. I would NOT recommend spending money on this unit.

I definitely concur.

A five year old battery might be expected to power off at any time below 50 percent full, because the cells get weaker over time and the battery's ability to judge distance-to-empty deteriorates with age of the battery.

Why are you not running on power adapter?

runbluemaddy wrote:

I ** using DisplayLink to extend the desktop to multiple screens via a docking station.

The reported power issue only shows itself when running on battery power.

Thanks for clearing that up!

runbluemaddy wrote:

I ** using DisplayLink to extend the desktop to multiple screens via a docking station.

The reported power issue only shows itself when running on battery power.

And... what about without using the docking station?