To maximise the endurance and overall life of a laptop battery, should I take steps like avoiding recharging while its partially charged? Should I avoid keeping it fully or partially charged beyond a certain length of time? Is there a technique for coaxing longevity back into it after that’s been whittled away?
It depends on the type. For the LiIon batteries, most of it just comes down to aging. Used/unused, charged/uncharged, after a certain amount of time they fail. They like cool temps more than warm temps, but not many other options for extending the lifetime.
If you have NiMHs OTOH, some things to note: Do not keep charging them after they are fully charged. You can get voltage depression which looks like a dying battery. So either: run off the battery, run off the AC or be charging a truly rundown battery. Don’t run off the AC with a charged & charging battery. I have recovered several NiMHs from voltage depression by just running the device until it goes off. Wait a while. Lather rinse repeat. For laptops, this means turning off all battery saving functions in the BIOS and software.
http://www.batteryuniversity.com/parttwo-34.htm (LiIon)
This site seems to recommend storing cold at 40% charge.
Unless you have two batteries, that seems like too much trouble. I have a new replacement battery for my Dell Latitude, and I am experimenting by keeping in at 40% in the fridge, except when charging it up and taking it on business trips. Otherwise, I keep the original battery in the machine. The original battery (system shipped 3/03) only holds about an hour or two at this point w/o any special care.
The rule of thumb is that whatever battery you have will play all but the last 10 minutes of any DVD on the plane.