My 10 year old Macbook Air is giving me some fits. Could be time for a new battery, but here goes. Wife noted it was showing 0% and charging for a while, but the light on the charger indicated it was charged. Pulled the plug, and it shut off immediately. Uh oh, battery may be shot. Plugged cable in, still says charged. Unplugged, hit the power switch, and it turns on, showing 100% battery. She shut it down because she didn't need it. Next day, it's plugged in, and still showing 0% and charging. Tried the same sequence, but this time, trying to start it on battery, the screen shows it needs to be charged. Plugged in, shows it's charged, but turns on and shows 0%. Pulled the plug, and it shuts off immediately. Yeah, battery may be shot.
Today, last ditch effort. Tried turn it on a few times on battery, got the low battery screen several times. This time, I plug in the charger, and it's actually charging! So I turn it on, it shows 98%. Pulled the plug, and it kept going. Got down to about 38%, but then it suddenly jumped up to 55%. Kept going, and it abruptly turned off at 44%. So, it seems the battery does have some life, it's just way out of calibration. Letting it cool off for a while, hoping it will charge back up and work properly. All told, probably ran for 1.5 hours.
Today, last ditch effort. Tried turn it on a few times on battery, got the low battery screen several times. This time, I plug in the charger, and it's actually charging! So I turn it on, it shows 98%. Pulled the plug, and it kept going. Got down to about 38%, but then it suddenly jumped up to 55%. Kept going, and it abruptly turned off at 44%. So, it seems the battery does have some life, it's just way out of calibration. Letting it cool off for a while, hoping it will charge back up and work properly. All told, probably ran for 1.5 hours.