MacBook Pro M4 disables external monitor video when running on battery with lid closed

Your Mac is behaving as designed. The default for closing the display is that the Mac sleeps, and that sounds like what yours is doing.

Only if you satisfy ALL of:

• connected an external display

• connected to a source of power

• connected to external keyboard

• connected to external pointing device

...will your Mac allow an exception, which is Not sleeping but instead staying awake and running with the external display active, known as "Closed Display Mode".

Also note that Shutting Down, Restarting, Sleeping, and opening the display from this state are all are undocumented behaviors, and may produce wildly different results.

bookooc wrote:

Well that really sucks! I didn't want to keep my power connected at all times, as I've been told it isn't good for the battery.

Thanks for the replies. Now I wish I could make the tabs , menu bars etc bigger in Chrome and the Apple toolbars etc. when in 4k. I have to lower the resolution to see the darn text. I have increaed the text size, but this doesn't help for the toolbars etc.

thanks

Leaving your computer plugged in will not damage the computer or the battery. The MacOS manages the power/charging system very well. No need for you to try to micromanage the system.

bookooc wrote:

Well that really sucks! I didn't want to keep my power connected at all times, as I've been told it isn't good for the battery.

You’ve been given outdated information. Your Mac will manage charging to prolong battery lifespan, including pausing charging at 80% if frequently connected to power. Best practice is to plug in whenever you can and run on battery when you can’t.

Closed display (clamshell) mode requires power to be connected.

bookooc wrote:

I need to know how to do this while on battery.

Power is required. You could use a powerbank if you need portability, such as one of the 25000 mAh units from Anker that output 100 W.

<< Now I wish I could make the tabs , menu bars etc bigger >>

settings > Accessibility > display > text ...

MenuBar size { default | large }

>> choose large and restart