Ohhhh, I see, you leave yours plugged in all the time. I cycle mine to almost dead at least once a week. I know for a fact lithium batteries don't like keeping a full charge all the time because my old precision M50's battery got raped like that and would do exactly what you describe. Mine is actually lucky to see more than a day or two at 100% charge and that's assuming it leaves my backpack over the weekend.
And yes, it's a lithium, Sony makes a point to put that in bright blue on the battery right next to where it tells you to dispose of the battery properly. I just need the secondary battery so I can go forever without a charge! Or I could pick up the 8-cell instead of the 4-cell I run now... lol
Yeah I don't really cycle it at all. Good point though . . . best life is achieved by NOT keeping the cells fully charged - learned that years after I got this laptop so I was operating on not cycling them at all and that ends up killing them by keeping them fully charged. Too late to do anything about that now however. OPerating mine on battery power changes performance levels so I just keep it powered up all the time. Never shut it down much either - just suspended it but since I added the stupid Microsoft ZUNE it crashes all the time when waking up from suspend so I just shut it down at night now.
Yeah but then when you need them to last you may forget to adjust them down and typically that happens when the power cord disconnects without you knowing about it and then it is too late . . . poof it crashes or shuts down when you are not looking or in the middle of a long email writing something profound.
Higher combined mileage (50MPG), larger 1.8 Liter engine, lower RPM at highway speed, smaller electrics for the hybrid drive, drag CD 0.25, more head room in the rear, 5 cubic feet more internal space, lane assist, more traction battery power, 3 operating modes, autopark, electric water pump, exhaust gas recirculation, exhaust heat reclamation, lower CO2 emissions, optional LED headlights, to name a lot of them. They figure that 90% will be sold to existing Prius owners that will trade in old ones for the new 2010 model.