How do you know if the bluetooth mouse and keyboard needs charging?

[levmc]

The ones that come with an iMac.

 

[casperes1996]

The ones that come with an iMac.

There's this in System Preferences.

You can also go to Bluetooth in the Menu Bar, and hover over the device to get this:

 

[HenryAZ]

In System Preferences/Bluetooth, check the box that says "Show Bluetooth in Menu Bar". Then you can just click on the menu bar icon and see the battery level (remaining charge) of your bluetooth mouse or external trackpad.

 

[mollyc]

A message will pop up when you reach a certain % and they need to be charged.

 

[Fishrrman]

When they stop working, they need charging!