Battery Cycle Count

I just got my T500 a few days ago and I love it. I got a 9 cell battery as well as an ultrabay battery, and get about 7 hours of battery life on integrated graphics with the screen brightness all the way up! I've haven't come close to running out of power yet, usually by the time I run through the ultrabay battery I've plugged in again. Because of this, my cycle count for the ultrabay battery is at 6 while the 9 cell is only at 1. I know this is a long way off, but how many cycles can these batteries take before they really start losing a lot of capacity. Is there a way I can tell it to use the 9 cell even if I have the ultrabay battery in? I just don't want to end up having a useless ultrabay battery with hundreds of cycles and a 9 cell with about 20. I'm guessing I'll get a new computer in 4-5 years so I'd rather have each battery be used fairly equally so I don't have to replace one.

 

You will probably have to replace a battery in a couple years. But it is good to spread out that usage as you sort of implied. Because batteries inherently cannot last forever...manufacturers only warranty them for a year. However, if you treat batteries correct you can get them to last 2+ years and have most of their capacitance.

 

Unfortunately there is no way to tell the computer to use the main battery before the ultrabay battery. It's kind of annoying, but that's how Lenovo has it set up. However, it is pretty easy to just pop ultrabay battery out.

Batteries will slowly lose their capacity, with use and with time. My 2-3 yr old 9-cell apparently only has 39 cycles, but is at 57% of its original max (45 of its original 78Wh). My 6-cell (same age) has 248 cycles, and holds 33 of its original 52Wh (63%). (wow, that's weird that they're so different...)

 

Heat and your recharge behavior are also very critical...