Why was I excited about getting the opportunity to review the Power Fort? Because the iPhone 4S does have some battery issues, and battery life sometimes becomes a problem for me. They are probably related to the extra services that are running on the 4S, but I notice shorter battery life than what I had on my iPhone 4.
For the purpose of my testing, I am actually leaving the Mophie JuicePack on the phone and using the Power Fort in addition (for even more juice!). In case you are not familiar, the JuicePack is a case/extended battery for the iPhone that virtually doubles the battery life on the standard iPhone battery. It was a great purchase and I recommend it to anyone with an iPhone (even though it adds some serious weight to the iPhone).
In testing, I would let the iPhone run completely dead, then I would use the Mophie to charge the iPhone back up completely (which would drain the Mophie dead), and then I would run the iPhone dead again (so both the phone and the Mophie had a dead battery). Then I brought out the Power Fort.
It’s excellent. There’s nothing more I can say about it. It completely charged the iPhone and the Mophie (so basically two complete iPhone charges), and had some power to spare. If you jump on the cross-country flight and you watch movies on your phone the entire way there, with the Power Fort you can have a full battery when you arrive and actually need to use your phone.