I got this because there are times when I need my Blackberry to be functional and I'm not near a charger. I hadn't tried the P790 yet when hurricane Irene decided to pay a visit. I had the unit charged up when the power went out Saturday before 9pm. By 4pm the next day, power had not been restored and the phone was going below 20% & wanted to shut down some functioning to conserve what was left of the battery life. I attached the P790 with an adaptor I bought at the same time. In under an hour I was at 55% battery life and could keep going normally till I had an opportunity to do a normal charge at my office, later that evening. It'd be an understatement to say I'm pleased.