After research, I found a MORE powerful backup battery "iPa 3000 portable battery" from amazon for my iphone. It is much cheaper, and easy to use. Very nice.
I am also looking for a Good Portable Power Pack but this is nice for 3000mAh, I am just wondering the size and Weight, looks heavy at 2 pounds Weight.
I have been looking for a good portable power pack battery for a long time. And finally I have got it here. Thanks a lot for sharing such a valuable information for me. It has really made my day. Thanks buddy.