Let Time Machine back up your MacBook on battery power

Why it happens

Out of the box, Time Machine on a Mac laptop only backs up while it's plugged in, so a backup never eats into your battery. If your backup disk is rarely connected while you're charging, backups quietly get skipped. One switch in the Options… sheet lets them run on battery too.

How to fix it

1. Connect your backup disk, or make sure your Mac is on the same network as it if it's a network disk.

2. Open the Apple menu, choose System Settings, click General in the sidebar, then Time Machine.

3. Click Options… and turn on Back up on battery power. Click Done.

   General›Time Machine›Options…›Back up on battery power

4. Test it while you're unplugged: click the Time Machine icon in the menu bar and choose Back Up Now. When it finishes, Time Machine settings show the time of the latest backup.

   Menu bar›Time Machine›Back Up Now

Still not fixed?

1. Don't see Back up on battery power? It only shows on Mac laptops. A desktop Mac is always on mains power, so it doesn't need the switch.

2. No Time Machine icon in the menu bar? Turn it on in Menu Bar settings, under Menu Bar Controls.

   Menu Bar›Menu Bar Controls›Time Machine

3. If Backup Frequency is set to Manually, nothing runs on its own, plugged in or not. Pick one of the automatic choices in the same Options… sheet.

   General›Time Machine›Options…›Backup Frequency

4. If backups still don't start, check that the disk shows under Time Machine in settings. A network disk needs your Mac on the same network, and a USB disk needs to be plugged in.

5. If backups fail with an error even on power, open Disk Utility and run First Aid on the backup disk. If First Aid finds errors it can't repair, the disk may be failing and should be replaced. If the disk checks out and backups still fail, contact Apple Support.

   Disk Utility›First Aid