My Macbook Air will not keep the charge for very long

Please post the EtreCheck output as a "Reply" to this thread

<https://discussions.apple.com/docs/DOC-6174> or <https://etrecheck.com>

Use the EtreCheck "Share" button to "Copy Report" (See the image below)

And then Paste in a "Reply" to this thread.

If, AND ONLY IF, you get the error:

"The message contains invalid characters"

then try posting to PasteBin.com, and give us a PasteBin URL link.

<http://pastebin.com/>

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EtreCheck is a tool that helps Apple Support Community volunteers debug problems without any access to the troubled computers. Debugging problems can be a difficult task even when the machine is in front of you. Attempting it via a discussion forum is extremely difficult. EtreCheck is a great help that regards.

Use spotlight to search for activity monitor and open it.

In the app, look for CPU% and determine the highest grade of usage and what it relates to such as a know or unknown app or service running in the background.

But you might have a faulty battery and a reservation might be required for a full cycle count.

Please see

Determining battery cycle count for Mac notebooks

https://support.apple.com/en-us/HT201585

Try these helpful articles

Calibrating your computer's battery

http://support.apple.com/kb/HT1490

Tips for maximizing your battery charge.

http://support.apple.com/kb/HT1446

How long have you been using it.