For 4.5 years I used a 15" macbook pro from mid-2008. It had changeable batteries so twice I went to Apple and convinced them to give me a new one for free. The three batteries I used in that machine were very different. The first one was a champ. It would last for six hours at its peak. It degraded slowly and predictably over time. It was reliable. But then, after two blissful years, it started throwing out Service Battery alerts.
Thus began my quest for the perfect battery, which was never satisfied. The other two I tried weren't as good. Especially the third one which started off at a peak of about 3.5 hours. If I didn't know it already from phones and mp3 players I learned then that rechargeable batteries are fickle. The new MacBook Airs are supposed to have all-day battery life, but what are some of the unlikely gems already in your gadget arsenal? Or just low-power devices that are meant to hold a charge for weeks and do. Power powwow below.