Are battery electronics responsible for battery breakdown?
My iBook (500MHz, Dual USB, Combo, 2.5 years old) had the same problem: within 2 weeks battery life dropped down from 1.5hours to 5min, charging would go on for about 10min, then it said "charged". capacity in xbattery would read 68 mAh only (>4000mAh is normal!).
tried resetting power manager unit, resetting nvram, nothing would help. even tried resetting battery's internal power manager by shorting the two outermost contacts (not recommended, battery could explode!). didn't work. so i ordered a replacement battery for 200 swiss francs (about 150$).
after that i decided to open the old battery pack. it is made out of 6 batteries of the panasonic CGR18650A type (3.6V, 2000mAh) connected in a 2 parallel x 3 serial way (giving 10.8V, 4000mAh), plus the internal battery pack electronics.
seemed that a resistor on the battery electronics broke off (don't now whether this came from the dissembling...), maybe this was the actual cause for the battery pack breakdown?
the batteries reminded me of the one used in my MiniDisc-player (Sharp MD-MS200) so i checked the MD-Players battery and it read 3.6V, 1400mAh. tried to use one unit of the iBooky batteries in the MD-player (they're somewhat shorter than the sharp batteries, so i had to use some plied aluminum foil to ensure contact) and it worked! operated it for over 5hours, no heating of the battery nothing unusual, even recharged it once overnight, no problem.
didn't check the other battery units yet, but it seems that rather the battery pack's internal electronics than the actual battery units were broken. so i have 6 functional Panasonic CGR18650A batteries now...anyone interested?
disclaimer: use this information at your own risk!