Yeah, it's quite interesting to watch it charge, if you're an OCD engineer like me. Open System Profiler (About This Mac > More Info > Power) and look at the numbers. You have to press ctrl-R to get a refresh, the numbers seem to refresh every 30 secs or so.
My battery is nearly new. Charging it seems to go at about 1500 mA, tapering down as the voltage reaches 12600 mV. Then the Magsafe light turns green, but it still charges about 200 mA, then it tapers slowly from 200 mA to 0 mA over an hour or two (can't remember). Interestingly during the taper period the voltage barely changes at all. Then it stops charging altogether, ie 0 mA.
If you write down the max voltage at the end of the charging cycle, then leave the Mac asleep on the charger overnight, in the morning it has dropped a few mV, at least mine has. A few mV in ten hours is consistent with the idea that the battery very slowly leaks charge, but the charger won't top it up until the voltage has dropped to ?12150? mV, which would take hundreds of hours.
Also if are using the computer and you unplug the charger at full charge, and plug it in after only a couple of minutes, the charger does not start to charge the battery. You have to run the battery down a good chunk (10%?) before it will charge it again. Again this is all consistent with the idea that over-charging is bad & the charger protects the battery very well.
All this means people talking about 95% or 97% of maximum capacity is meaningless. The charger is playing lots of games to protect the battery, the number of mAh at any given time depends on how the charge algorithm is behaving. The full charge capacity varies quite a bit between consecutive charges, just because that's how the charger works.
Anyway I thought it was interesting......
