Why won't my MacBook charge above 99% battery?

How old is your MacBook? I heard that some people get this problem with old MacBooks. The number slowly goes down.

You may need to ‘reset’ your battery.

Just google ‘reset your battery macbook pro (or whatever)’

@Pixel: I purchased it this summer, so it’s not too old…

You need to calibrate the PMU. To do this, use your MacBook normally without the power cord inserted until the battery drains to the point that the computer automatically shuts off and will not start. Leave it off for a few minutes, and then plug it back into the power source. Let it charge until none of lights on the bottom are blinking anymore. This should resolve the reading problem and make the figure more accurate. If you still have problems, contact Apple.

@richardhenry I also heard it’s good to do that once a month to keep your battery healthy.

Pixel, the new lithium-ion batteries are not suppose to suffer from remembered discharge like their predecessors. They still might, but the new ones shouldn’t.

@bodyhead Thanks. Good to know.

@richardhenry, that procedure calibrates the battery chip, not the PMU. The PMU (Power Management Unit) was a chip on the logic boards of New World PowerPC Macs that managed power-related functions like sleeping, waking, charging, etc. On Intel macs, that chip has been replaced by the SMC (System Management Controller), which can be reset using this procedure.

In addition, the Apple-specified battery calibration procedure specifies that the computer should be fully charged, left for two hours, then fully discharged, left for five hours, then fully charged again.

The battery calibration isn’t a terrible thing to do, but I usually associate battery uC problems with symptoms like suddenly dropping charge, unexpected poweroffs, etc. Let us know how that goes if you do it.

TitsMcGhee, if you do an SMC reset and it doesn’t help, the information that the command-line tool “pmset” provides can be useful. In the Terminal, type “pmset -g rawlog” to get a display of everything the battery is reporting to the computer. Paste it here and maybe we can pull something out of it.

@aaronbeekay: Good to know, thanks.

I used to have an iBook that just stayed that way. I never really thought more of it, cause I got 6 hours outta the battery – honestly I don’t think that 1% will make a difference.

The 1% is for the LED

The same thing happened to me (99% charged battery).

I think it was because when I put the new battery in and charged it up for the first time – the computer was ON and I was using it.

I didn’t think it would make a difference, but it probably did.

To anyone reading this:
When you put a new battery in (to charge it for the first time)—charge it with the computer OFF—until the AC Adapter LED turns from amber to GREEN.

THEN, as per Apple’s instructions, you can use your computer for the next two hours or so with it plugged in. THEN, use it unplugged until it goes the fully asleep “sleep” mode (the second time it falls asleep) and THEN let it sit 5 hours before FULLY recharging it.

Otherwise, your battery—like mine is now—will be stuck on 99%.