Have you started to notice that your MacBook Pro has begun to run slow, only while running on batteries? The following fixes should help you fix MacBook Pro running slow on battery problems once and for all.

First of all, before you get to the fixes, you want to make sure that your MacBook’s performance problems are indeed occurring only when it is running on batteries and not when connected to the MagSafe connector.

To confirm this, please carry out the following steps;

Plug in your MagSafe
Power up your MacBook Pro
Go to Activity Monitor -> CPU -> CPU Usage Graph -> Note down CPU activity %
Unplug the MagSafe connector
Go to Activity Monitor -> CPU -> CPU Usage Graph -> Note down CPU activity %
Check to see if there is a significant difference between the two CPU activity % figures. When connected to your battery, your CPU activity % will show as 60%+. When connected to MagSafe, this figure will drop down to less than 10%.

Now that you have confirmed that your MacBook Pro is slow only while running on battery, let’s proceed to the potential fixes.

1. Deleting a certain .plist file

You will be shown how to find and delete a certain .plist file on your MacBook Pro. First, please take a backup of this file before you delete it. If your Mac starts to act funny after carrying out the following procedure (shouldn’t happen though), please restore that file to its original location.

Identifying your Mac’s model

Click on Apple Icon in Menu Bar
Click on About this Mac
Click on “More info”
Click on Hardware (found on the left side)
Write down the displayed Model Identifier e.g. MacBookPro x.x
Finding and deleting the problematic .plist file

Open Finder
Select Macintosh HD (The one with OS X installed on it)
Select System -> Library -> Extensions
Find and Locate a text file called “IOPlatformPluginFamily.kext”
Right click on the file and select “Show Package Contents”
Click Contents -> Resources -> Plugins
Right click on ACPI_SMC_PlatformPlugin.kext
Right click on it and Show Package Contents
Click Contents -> Resources
Find the .plist file that you identified earlier (e.g. MacBook pro x.x)
Delete the file
Restart your Mac
Hopefully, this would have fixed your Mac running slow on battery problem!
What does deleting the above .plist file actually do?

The theory is that the .plist file identified above is the file responsible for telling your Mac to slow down, when on battery power, so your battery life can be extended. More technically, the file actually instructs your Mac’s processor to work at a much slower clock speed than it is usually capable of, thereby resulting in dramatically reduced performance levels.

In some cases, instead of just some minor slowdowns, this .plist file brings about a crawl, leading to performance issues that probably made you find your way here to this page.

Remember, deleting this .plist file is a hack discovered by users after several trial and error methods and not something that is recommended by Apple, at least not officially. However, several hundred users have vouched for this method in forums and various types of online discussions.

Check your MacBook’s Battery Health

Sometimes, it could just be that your MacBook’s battery has run out of juice, pun intended! Just because it shows a full charge icon doesn’t always mean that the battery is working like it is supposed to be working.

Run a quick diagnostic test on your MacBook’s battery. Here’s our post on how to monitor MacBook battery health.

If the tests show that your MacBook’s battery has deteriorated significantly, it makes sense to invest in new batteries that might just fix your Mac’s slow performance issues, while running on battery power.

Other ways to possibly fix this problem is to carry out a SMC reset, PRAM reset and maybe by running a Repair Disk Permissions process, all of which are explained in a post that is linked to at the beginning of the article.

If you have used any other method or have read about other potential ways to fix a MacBook’s performance woes while on battery power, please do share them with us and we will in turn be glad to share it with our readers!