Chosen Solution
After having had this machine for a little over two years, the battery has about half of its useful life according to the battery statistics in the system monitor application (3300 mAh, 148 charge cycles). Yet when running on the battery and the battery monitor in the top right of the screen has dropped to about 91%, the machine simply shuts off as if there was too little power, with no warning or other indication. While buying a new battery is of course an option, my gut feeling is that the real problem lies elsewhere. Has anyone else had a similar problem and was able to solve it?
That is an extremely low amount of capacity for that many charge cycles. Looks like you have a defective battery. If you can boot without the battery connected I would rule out a bad DC in and confirm the bad battery. I have a 2009 Macbook (non unibody) with almost triple the charging cycles and it has over double the capacity of your battery. That battery is defective. I would check with Apple and make sure that this isn’t a known issue and you might get a free replacement. Worth a shot.
