I got this external battery to mainly use with my htc evo instead of buying a bulky extended phone battery but soon discovered that it also works great on my ipod. It allowed me to charge not only my ipod while watching videos on a 14 hr flight but also charged my friends iphones while still leaving enough charge for my phone after landing.  It can charge my phone up to 4-5 times before it needs  to be recharged The charging chord that comes with the battery is a good length and allows me to have the Imp500 in my pocket charging my phone while I'm taking on it. Its great to have around since you can pull it out whenever any of your devices starts to die.