MacBook Air M4 battery drained when shut down

Hello

I've owned a 13-inch MacBook Air M4 since May 2025. So far, I haven't had any issues with it, apart from one strange crash while it was in sleep mode many months ago, which has never happened again. I mainly use my Mac for work and studying, but because of the holidays I've been using it a bit less over the past few days.

A few days ago, I charged it from 0% to 100% and then shut it down completely so it wouldn't drain the battery. Today, literally about half an hour ago, I turned it on for the first time in a week and saw that the battery was at 53%, and it has already dropped to 46%.

The battery graph shows something like this (screen attached at the end), as if the battery suddenly dropped from 100% to around 50% on its own when I turned the Mac back on. I checked Screen Time, and it shows absolutely no activity during the days the Mac was turned off. I literally just powered it on, so there's no chance I accidentally left it in sleep mode.

Activity Monitor does show that Safari supposedly used a significant amount of battery over a 12-hour period, but neither Screen Time nor the Battery settings reflect that at all. So I'm confused about what's going on and why the battery percentage dropped so dramatically.

The battery has 90 charge cycles, the maximum capacity has gone from 100% to 99%, and the battery condition is reported as Normal.

I also noticed that after turning it on, it took a bit longer than usual for all the files and folders on my desktop to appear.

I also don't understand why the battery panel says that I last charged the Mac to 53% today. Since charging it to 100% and shutting it down a week ago, I haven't plugged it in even once. In fact, I didn't even take it out of its sleeve during that entire week.

I'm certain that nobody used my Mac during the past week. As I mentioned, Screen Time shows zero activity for that period.

What could be causing this? Is this something I should be concerned about, or should I just recharge the Mac and not worry unless it happens again?

[Edited by Moderator]