Rechargeable batteries start deteriorating from the moment they are manufactured. I’ve noticed my Canon 20D’s batteries don’t last quite as long as they did 2 years ago. AA and AAA batteries seem to be even worse. As I’m heading to San Francisco in July I’ll be doing a lot of flying so it’ll be important that my Apple Macbook laptop have a decent battery life.
There’s no quick fix for this as it’s not reversible but if you’re wondering how much life is left, then Coconut Battery is a must have. I installed it last night and it looks like my battery still has 85% of it’s capacity left after 11 months of use. That’s not bad. It’s not enough to get me across the Atlantic but I don’t know if I want to spend €139 on a second battery when I’ll only ever use it once a year.
I think it is possible to slow down the deterioration. Don’t unplug your laptop! The less you use the battery, the longer the battery will last.