MacBook battery meter less than 100% when on AC

The battery will not charge to 100% sometimes unless it is drained down from time to time. I have seen this vary on multiple MACs I own. This keeps the charge cycles down.

http://support.apple.com/kb/TS1909

Resolution

This is normal. The batteries used in these computers are designed to avoid short discharge/charge cycles in order to prolong the overall life of the battery.

When setting the Mac OS X battery status menu bar icon to display charge state by percentage, you may notice that the reported charge stays between 93 or 95 percent and 99 percent.

The adapter will not charge the battery to 100% automatically if it will add additional wear to the battery.

I tried that, and it didn't seem to make a difference. Prior to Moutnain Lion, I never had this issue (on my late-2010 MBP). After Mountain Lion, this happens about 50% of the time when plugged in.

Not a major issue, just annoying for us OCD-type folks. 🙂