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Calibrate your MacBook Battery

July 21, 2011

Apple’s help documents tell you how to calibrate your MacBook’s battery but it fails to say why it might be needed. In this tutorial I will walk though the process of calibrating the battery and explain why it is needed.

 

When you click on the battery status indicator in the top menu bar of OS X, you will see a couple of things. You can see what percentage is left, what the estimated time remaining is or if it is fully charged. You can adjust the settings by clicking the Battery indicator in the menu bar then roll the mouse over “Show” and choose your preference. 

Apple recommends performing a battery calibration within the first week of purchasing a new MacBook and then every couple months. But what exactly is the battery calibration and why do we need it? Battery calibration is the process of keeping the displayed battery information in sync with the actual battery level. For instance, if the display says you have 90% battery remaining, you want that to be an accurate representation of the battery its self. A battery can become uncalibrated simply by the process of charging and discharging the battery through normal usage. This is not a problem with the battery but can cause un unreliable display causing you to think you have less time remaining on the battery and unnecessarily cutting short your un-tethered web surfing. 

 

Apple defines a charge cycle as running the battery down 100% then re-charging it and claims 300 charge cycles for the life of the battery before it may need to be replaced. This does not mean that you need to sit and let the battery deplete fully before charging before you hit one charge cycle. An example of how this works is if you unplug your laptop in the morning and use it until you get to 50% and then charge it again, that is only half of a charge cycle. Then in the evening you run down to 50% again with a subsequent recharge that would put you at one full charge cycle. This process will eventually show a discrepancy between the status shown to the user and the actual battery. 

 

The procedures for calibrating the battery are as follows:

Step One

Charge your MacBook fully. When the light on the magnetic adapter turns from orange to green then the battery is fully charged. 

Step Two

Leave the MacBook plugged in for 2 hours. You can continue to use the laptop. 

Step Three

Unplug the laptop and run the battery down. Use the laptop until the laptop goes into mandatory sleep on its own. You will receive warnings when the battery is getting low that will tell you to start saving your work. Save your work and continue to use it. Since this step can take 4-8 hours depending on your usage, you may want to set the computer Energy settings so that it does not sleep before the mandatory sleep. To do this go to System Preferences, Energy Saver and make sure you change the settings for Battery power. Drag the slider for Computer Sleep all the way to the right. 

Step Four

After the computer forces its self to sleep, let it sleep for five hours or more. This will fully drain the battery so when you re-charge it, it will know it is starting at zero and when it is full it is 100. I like to time my calibration so that I use the laptop in the afternoon on battery power and then let it sit in the extended sleep while I am sleeping.

Step Five

After five hours or more, plug in the MacBook and let it charge completely. You can use the laptop during this time. 

 

Thats it! Now you laptop battery and the display is calibrated and in sync. Don’t forget to change your Energy Settings while on Battery back to allow the computer to sleep if you changed them in step three. 

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