PowerDuo Reserve

• The industry's most trusted AC and 12 volt chargers
• Charges iPhone, iPod, MP3 players, other USB-chargeable devices
• Removable backup battery provides hours of additional use for iPhone and iPod
• Battery is interchangeable between PowerJolt Reserve and PowerBlock Reserve chargers (chargers and Reserve battery packs are also sold separately)

The good: The battery is small and light. The less then optimal: The battery pack does not provide much extra power. Reviews for this product (on Amazon and elsewhere) report it provides about 70-75% additional battery life. In 2 uses of this with my iPhone 4S, it only provided 15%-20% increase in battery power. The 15% was after the battery pack had sat about a week after being charged. The 20% was after the battery pack had been just removed from the charger and said it was fully charged. While I like Griffin products and generally find them to be of better than average quality, I think this product is a bit too expensive for the additional power it provides.

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Ok, I got this for our 4 hour flight and it came in handy when my daughter had 7 percent battery life and when she used this it gave her 37 percent more. Works fast and keeps it's charge even if it's not plugged in for a couple days.

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This is the second griffin charger I have purchased. The first one was for my teenage daughter, who loves this device and carries it with her wherever her phone goes. The second was for my wife, who like my daughter, would find herself in an awkward place with a phone about to die. The backup battery charges from the car charger and is fairly small so it fits in a pocket or purse easily. It provides about a 40% charge, so don't expect a full charge. The 40% charge gives them both about 2 hours of phone service, so so far it fits the need very well without being bulky. Now my grown son wants one.

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Have this product for over one year and liked it enough to send it as a gift for a friend!

This battery has been charged for hours and only provided me with 20% boost. Seems useful for trips and plus it comes with wall and car charger. Didn't pay much for it but $29.99 seems overpriced for me.