The Kensington Mini Battery Extender is a very nice size and matches the iPhone 3G or original iPhone in width. The case is made of metal, not plastic which is nice. It gives you confidence that this battery is well made. It also has 3 battery level lights (blue LED) and a low power warning/charging light that shows red when low and green when the iPhone is fully charged.

The Kensington Mini Battery comes with a retractable mini USB to standard USB plug for charging but little else. The manual is confusing to read with the various languages grouped on each page. Reading through it gave me very little information aside from some of the strange rules about storing the battery. First of all, they ask you to try not to store your Mini Battery Pack fully charged or discharged. They claim it’s best to store it at 60% charge remaining. Exactly how you’re supposed to do this isn’t explained but I can assume when they say “store” they mean not use for a long period of time.

The manual also warns to avoid frequent full discharges, and to charge the battery pack even if it isn’t fully discharged. That said, it takes approximately 2.5 - 3 hours to fully charge the Kensington Mini Battery Extender. The battery does seem to lose charge if you don’t use it after charging. Leaving the battery in my bag for a few days produced a battery indicator that showed only halfway charged. Still it was enough juice to recharge my iPhone to full charge from half charged. Not bad.

If the mini battery isn’t good enough for you (and it might not be), Kensington also makes a larger battery that will probably last you for at least a couple of days. We don’t need that much power nor the extra weight. The biggest plus of the mini battery is the size and the fact that I can carry it easily with me. It’s already saved me during days of heavy iPhone usage and I’m sure it will continue to prove valuable in the future. This is one investment I’m glad I made.