Battery: After upgrading to mac OS 13.1 from 13.0, battery came down to 91% from 94% in 18days.

Thanks for posting in the Apple Support Communities jaedon_mgs,

The following are the recommended steps to determine the health of your Mac's battery:

To view your battery’s condition, choose Apple menu  > System Settings, then click Battery  in the sidebar. (You may need to scroll down.)

Look at Battery Health on the right. You may see any of the following conditions:

• Normal: The battery is functioning normally.

• Service recommended: The battery is performing normally, but its ability to hold a charge is less than when it was new. You may want to consider replacing the battery.

Check the condition of your Mac notebook’s battery

If it says the battery is functioning normally, you can continue using your Mac with the expectation and confidence that it will be available with a charge when you expect it be.

If it says service recommended, you can continue using your Mac, but may see battery life affected, and should set up service at your earliest convenience.  Find out how to service or repair your Mac.

We hope this helps!

Thanks for letting us know, jaedon_mgs,

If you'd like to report this to Apple, we'd suggest that you contact Apple directly. You can find their contact details here: Contact Apple Support

Take care!