Torsten Curdt’s weblog

Battery Statistics

An easy way of finding out about the health of your MacBook/MacBookPro battery is to use this little command line.

$ ioreg -w0 -l | grep Capacity
"CurrentCapacity" = 5259
"LegacyBatteryInfo" = {"Capacity"=5279,"Voltage"=12596,"Flags"=7,"Current"=5259,"Amperage"=267,"Cycle Count"=48}
"DesignCapacity" = 5500
"MaxCapacity" = 5279

MaxCapacity is the current capacity your battery can still hold on a full charge. DesignCapacity was the original capacity. So if the difference gets too big your battery is probably end of life and ready to be replaced. Most likely the related Cycle Count is high then as well.

It would actually be a neat little project to collect this information over time with RRDTool. If you are OK to shell out a few bucks there already is a software called ibat that seems to do this.

Update: There is also a freeware tool called coconutbattery that shows this information in a nice UI.

  • I’ve followed Apple’s instructions for recalibrating the battery ( http://support.apple.com/kb/HT... ) twice so far, and coconutBattery has reported an increase in current maximum capacity each time.

    Not sure yet if the battery life actually is longer, but I’m hoping so. The process is a bit fiddly, but might save me shelling out for a new battery just yet.
  • ricki

    I actually have the same thing happen:
    855 Cycles
    4935 mA

    on a more than 2 year old MacBook.
    It was a result of upgrading from tiger to leopard, that is a least my best guess.
  • @Aaron: That's indeed very strange!

    My suggestion: contact the author of ibat. I am expecting he might have some clue. And then let us know! :)
  • Aaron Wagner
    Very interesting. My wife was concerned about how she should charge/discharge her new macbook and I wasn't sure.

    I ran this command for her, but the results don't make sense. How could her MaxCapacity be higher than the DesignCapacity?

    She's had the laptop for about seven months and it's been on almost 24/7 since then. I was really surprised by these results. It doesn't seem right, but I know nothing about how this stuff works.

    "CurrentCapacity" = 4804
    "LegacyBatteryInfo" = {"Capacity"=5167,"Voltage"=12269,"Flags"=4,"Current"=4804,"Amperage"=18446744073709550419,"Cycle Count"=142}
    "DesignCapacity" = 5020
    "MaxCapacity" = 5167
  • Henning Schmiedehausen
    iStat Pro displays this information, too. And my first generation MacBook Pro with once replaced battery (remember the "we need to replace your battery" recall?) is still at 85% health after 148 cycles.
  • Interesting command line. Thanks Torsten!

    Here are the results on my MBP:
    $ ioreg -w0 -l | grep Capacity
    "CurrentCapacity" = 2579
    "LegacyBatteryInfo" = {"Capacity"=2649,"Voltage"=12410,"Flags"=5,"Current"=2579,"Amperage"=0,"Cycle Count"=172}
    "DesignCapacity" = 5500
    "MaxCapacity" = 2649

    These statistics confirm my feeling that my battery lasts only half the time than when I got it, one year and 7 months ago.
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