5 Replies Latest reply: Dec 16, 2011 5:01 AM by Ralph Landry1
Cunnla Level 4 Level 4 (1,355 points)

My Macbook Air is a late 2010 13" model and right now the battery cycle count is 102, condition normal. I usually run the MBA on the battery until it goes down to 70 percent or so then recharge it. Until recently the battery capaciity was 98 percent, sometime 97,  but I could not leave well enough alone and decided to recalibrate the battery, about a month ago. Since then the battery capacity has fallen to 94 percent. At the time I did not know that it was not necessary to recalibrate the newer Macbook Airs. I have been hoping the capacity will go back up but no sign of that yet. Right now it is down to 93 percent. Is this normal for a 1-year-old Macbook Air? Should I try recalibrating again or is it likely to make things even worse and to be avoided like the plague?

  • Ralph Landry1 Level 8 Level 8 (38,635 points)

    REcalibrating does not recalibrate the battery, but, rather, the charge reporting circuitry.  Battery capacity on my MBP moves up and down a little and I just don't worry about it now.  Sometimes it will report 100% charge, sometimes a little less.  Run it down low and recharge and it comes back to 100%.  The Lithium-Ion batteries seem to have a mind of their own.


    As long as it says Normal for the Condition you should be doing fine. 

  • Cunnla Level 4 Level 4 (1,355 points)

    Thanks Ralph for the quick response. What I meant was the current maximum capacity as a percentage of design capacity, as shown in the Coconut app. Design capacity is 6,700 and maximum charge right now is 6,258, which gives 93 percent.

  • Ralph Landry1 Level 8 Level 8 (38,635 points)

    Never have used that app...I rely on the internal report...apple in the upper left corner, About This Mac, More Info, System Rrport then Power under Hardware.  Reports Capacity, Charge remaining, Charge cycles, Condition.  Might be interesting to compare the system reported data with the Coconut app information.  I suspect the app is just reading the System Report and giving it back.


    Though I hvae never had a Capacity come out such an even number...mine moves up and down, and is always all four digits.


    Just a thought, compare the capacity reported with that Design Capacity...just wonder if that is using a design spec for the battery rather than the actual capacity of the individual users' battery.  Take a look and see what how they compare.

  • Cunnla Level 4 Level 4 (1,355 points)

      Charge Remaining (mAh):          6258

      Fully Charged:          Yes

      Charging:          No

      Full Charge Capacity (mAh):          6258


    Those are my readings from the Apple menu.

    As you say, Coconut uses the same figures and compares them with

    something called Design Capacity (6,700) , which is, I guess, what it

    was supposed to be when it left the factory.

  • Ralph Landry1 Level 8 Level 8 (38,635 points)

    And those figures say you have 100% charge.


    The algoritm that is used by the reporting circuitry sometimes differes a little from the ration you calculate from the actual charge data...I've noticed a slight difference on occasion...so it is not something to be too concerned about when you see a reported charge of 98% and you know it is charged.


    Which brings up another point, the charging circuit will take the battery to full charge, if you leave it on the outlet power the charge circuit shuts down and you run on line power.  But the battery will still trickle discharge a little until it comes down to something like 95% at which point the charging circuit kicks in again and tops it up to full charge, then switches off again...that keeps the battery from over-charging, overheating, etc.  Part of the protection circuit.


    Looks like you are in good shape irrespective to the details of the Coconut report.