This is from the depths of my memory, so take it with a ton of salt:
Had a colleague with a similar issue, sometime back in 2005(ish). We were investigating the problem and solicited the help of an electrical engineer. I can't remember all the tests we did, but the final speculation was that:
- Batteries are a compound of several cells. As batteries age, the cells degrade at different speed. Some cells might still take a full charge, others not.
- when a cell runs empty of charge it usually leads to a sudden drop in voltage, which makes the computer shut down. Thus a battery may be as weak as its weakest cell...
- The metering of remaining capacity may be built on the assumption of all cells being equal and thus be based on only a number of cells (and extrapolated), thus giving false results.
OP, do you have the same thing as the poster in apple discussions, that your battery reports (Sys info or coconut) an absurd capacity?
RGDS,