I've used this (Duracell 5 Hour Mobile Phone and MP3 Portable USB Charger
) on my Blackberry 9650 Bold and can only say WOW! This, I'm going to get a lot of use out of.
An initial charge of the unit for 5 hours, then you're ready to go. A 55% depleted Blackberry battery was recharged in 2 hours and that not only left approximately half of the charger's power it enabled me to have a considerable increase in standby/talk time. Note that you can also charge your phone whilst the charger is still connected to the mains which means you don't have to carry your phone supplied charger with you, simply charge your phone in the normal way, over night (the USB charger switches off when the phone battery is fully charged) then go in to work the next day with a fully charged phone AND have the USB charger ALSo fully charged.
How the charger will be after a few uses (normally it take a few re-charges for these Ion type batteries to operate fully), I don't know. I also don't know if the USB charger battery will last long (although other similar batteries I've had last a long time), my first impressions of this item are very high.
Whilst this is a little on the expensive side, I think this will be a useful item to many smart phone (especially Blackberry) users and will recommend it highly (it works also with your iPhone/iPad, just use your own Apple supplied USB lead). Keep a fully charged one in your car/briefcase/handbag and you can guarantee you'll never be saying to a potential client that you'll have to ring them back because your battery's dying.
My only negative comment is that I can only give it 5 stars, I wish I could exceed this - This is one of the first utility items I've received for years that not only "does-what-it-says-on-the-can" it exceeds my expectations. Well done Duracell - this is a truly a great product.