Replaced and broke-in new Battery - Client left for her Paris trip the same day!
2011 MacBook Air had been sitting in a closet for a couple of years, and when she pulled it out it no longer could hold enough charge to even retain the system's clock time.
I ordered the replacement battery from iFixit and put it in the day it arrived. I then charged it to 100% and ran the charge out twice in a row and rushed it to her apartment just in time for her to leave for the airport to catch her evening flight to Paris. Mission successful, yet another satisfied client!
(Original battery had one VERY swollen cell and was non-functional)
Repair was straightforward but don't forget to break in the new battery!
1. Finish replacing the battery and close up the Macbook Air.
2. Plug the power adapter in to the laptop and to a wall outlet, but do not turn on the power to the laptop.
3. Let the battery charge up overnight with the laptop turned off.
4. Once the battery is fully charged, leave the MacBook Air powered on under battery power only until the battery runs down completely.
Make sure the computer doesn't put itself to sleep by performing the following: Open System Preferences, and go to Energy Saver section. Here you see two sliders for Computer Sleep and Display Sleep. The sliders range from 1 minute, to Never. Use the sliders to adjust the sleep behavior to suit your needs. There are separate settings for Battery powered operation and for Power Adapter. You may disable sleep altogether by putting the slider on “Never”, Just remember to adjust the settings back to system defaults afterwards. You can also play a music CD or a DVD movie or as I like to do, in Safari, navigate to http://24hoursofhappy.com/ and play "Happy" in order to use up the battery more quickly.
5. When the battery runs out the computer will shut off. Let the battery cool down for 20 to 30 minutes.
6. Recharge the battery again as in steps 2-4.
(Do this twice altogether and your new battery should perform superbly)
7. Remember to adjust the Energy Saver System Preferences back to system defaults afterwards