Taken from : http://www.macnn.com/reviews/kensington-powerbolt-micro-car-charger.html
Kensington PowerBolt Micro Car Charger
August 13th, 2010Charge any Apple i-devices with this low-profile device.
You can leave this little USB charger in your carís Power Adapter and not worry about advertising its presence. It sits almost flush with your car and no cords hang out to trip you.
It seems that everyone and their sister make peripherals that you can charge with an USB port. The iPhone, iPod, iPad, cell phones, GPS devices, and hands-free kits all can charge via USB, and the list doesnít stop there. You can use many of these devices in the car, but your car probably only has a cigarette lighter, sometimes called the Power Adapter in these politically correct days, so you need an adapter.
The 2.1 Amp Kensington PowerBolt Micro Car Charger is just such an adapter. It plugs into the lighter in your car, and provides a power-only USB port for you to use. This is much better than a car adapter that has an integrated cable for two reasons. First, it means that you can charge several devices with a single adapter as long as you have the right cable for the device. Second, when you're not using it, you can leave it plugged in without worrying about the cable getting in your way.
PowerBolt Micro Package
The PowerBolt is very small; it is about 1 1/2 inches long, and when plugged into your car, sticks out less than 1/2 inch. Kensington refers to its low-profile design on the site. It has a little LED on the front, which shines red when it is getting power. The connector on the front of the PowerBolt is a standard USB female USB A-type connector, just like on your Macintosh. The PowerBolt also comes with a separate USB to iPhone/iPad/iPod connector as well.
To install the PowerBolt Micro Car Charger, you simply plug it into the lighter, and you're ready to go. The smallness works against the PowerBolt though, if you have to remove it. Since it is so small, and sits almost flush with the top of the lighter, it is hard to get a grip on it to remove.
The PowerBolt charged my iPhone on the way home from work one day, and my wifeís Garmin GPS the next time out. I am sure that in my car, the plug does not get power unless the key is turned on - the LED on the front of the PowerBolt make this easy to check. That means you do not have to unplug it to preserve car battery life when you leave the car.
PowerBolt Micro With Cable
Kensington claims that the PowerBolt Micro provides enough power to enable fast charging on an iPad. I charged my iPad while it was plugged in, but I didn't have any way of verifying that it was charging fast, as they claim. The iPad did go from 61% charged to 74% during a 25-minute ride.
The PowerBolt has a reasonable list price of $24.99, and is available from the Apple Store, as well as various online retailers such as Amazon. Now, if I could only charge my MacBook Pro over USB!
Edited by Ilene Hoffman, Reviews Editor
PowerBolt Micro Package Photo by Marshall Clow
-Charges all USB devices.
-Can rapid charge iPad.
-Nothing, but may be difficult to remove.
-No place to park your device.