A few weeks ago, my apr’09 13” MacBook started behaving strangely. After a few minutes off the power cord, it would simply shutdown without warning (no display of the low battery warning message … blam ! Black screen of death). The led battery indicators would show the battery to be at 80%, and if you started the laptop again, it would work for 5-10 minutes … then blam !
I’ve looked for solutions to this issue for a while, this behaviour didn’t match apple’s documents about battery calibration / PMU reset in their knowledge base, i’ve tried following every steps documented there (links provided below) to no avail.
I finally managed to get back to a properly running mac after following those instructions (Battery calibration) to the letter.
When the system would shutdown improperly, i would just start it up again until next time, and did this for 2 hours (about 6 or 7 power off / power on cycles) until the battery was completely depleted.
Then, i performed a full charge, allowing the system to rest for a few hours while on battery, powered it on, removed the battery adapter with my fingers crossed … and … I got my macbook back ! :-) Woooot :-)