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I am trying use my macbook with an external device in Clamshell Mode without the power adapter. Hence, I am following this tutorial.

The author gives, first, a GUI approach. Then, he suggests the following commands on terminal:

pmset -g | grep hibernatemode

sudo pmset -a sleep 0
sudo pmset -a hibernatemode 0
sudo pmset -a disablesleep 1

sudo pmset -a sleep 1
sudo pmset -a hibernatemode <original hibernatemode value | usually 3 on a MacBook>
sudo pmset -a disablesleep 0

The point that intrigues me the most is that before giving the instructions, he says:

Note: I have not tested these commands because Apple recommends not changing the hibernatemode using the pmset command, and these commands do just that. However, these commands will disable your laptop’s sleep on lid-close trigger, so they should also solve the problem of being unable to use your laptop in clamshell mode without the power adapter. That said, use them at your own risk.

Hence, my doubts are:

  1. Why does Apple not recommend tweaking hibernate-mode with the pmset command?

  2. What could go wrong? Why is it dangerous?

  3. If something bad happens, is it possible to revert the problem? And how to do it?

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  • 1
    How do you find out the original hibernatemode value?
    – minseong
    Jul 23, 2023 at 17:43

2 Answers 2

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Why does Apple not recommend tweaking hibernate-mode with the pmset command?

Apple has performed painstaking tests and engineering to optimize the balance between availability of your device and protecting your data. This has nothing to do with the health of your battery as the SMC and the battery itself will already take care of that aspect.

What could go wrong? Why is it dangerous?

Modifying the hibernation of your Mac changes when and/or if it writes the data from RAM to a sleep image. If the machine powers off prior to it writing the image of your machine state, that image doesn’t get written to disk. The danger is you’re now in data loss territory.

If something bad happens, is it possible to revert the problem? And how to do it?

“Revert?” Not likely. A sleep image that isn’t written isn’t a deleted file. It is data stored in volatile storage disappearing into thin air because it wasn’t saved. When it goes, it’s gone.

Now, if you’ve saved your data to permanent storage, then you you can revert. But, that’s incumbent upon you to manage it.

How do you prevent this?

Use your Mac as intended. There is a reason for using a power adapter in closed clamshell mode. Sure, you can circumvent it but then any failures and/or data loss is on you.

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Firstly: if your Mac laptop is permanently connected to a power source, it will go into "Optimized Charging mode" (after a few days), where it will only charge to 80%, in order to prevent any deterioration caused by being fully charged for long periods of time.

enter image description here

So the premise of the article -- that this procedure needs to be done to stop your battery being "destroyed" -- is false.

An external display makes different energy demands on your laptop, which the laptop can't manage in the same way as for the built-in screen.

The likely 'bad' thing that will happen is that your battery will fully discharge, because it no longer sleeps when you close the lid. Letting the battery fully discharge is just as bad, if not worse, than leaving it plugged in.

Apple's engineers spend a lot of time working on the design of the hardware and software, to maximise battery efficiency and lifespan. Rather than "Apple knows what we want better than we do", it's a case of "Apple knows how their products are designed to work".

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  • Won't it completely discharge with the lid open, too? Why is it worse with the lid closed?
    – Barmar
    Jun 9, 2023 at 0:32
  • @Barmar The point is that if you could connect it to a display with no power, it could completely discharge while unattended. In normal use (open, no cable, no external display), it will give you warnings about the battery %, go into low power mode, and sleep before turning off.
    – benwiggy
    Jun 9, 2023 at 6:50
  • I can't find "optimized charging mode" on my laptop. Is that a feature only of certain OSes or models?
    – minseong
    Jun 9, 2023 at 13:32
  • @theonlygusti In Ventura go to Battery Settings and click on the (i) next to Battery Health.
    – Barmar
    Jun 9, 2023 at 14:21
  • @theonlygusti You have to be running Big Sur or later, and I think some older laptops may not support the feature.
    – benwiggy
    Jun 12, 2023 at 9:39

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