We all know that the iPhone 3G and iPhone 3GS battery sucks, but what can you do about it? Griffin is hoping that its portable solution means you won't have to travel around with the charger wherever you go. But does it work? We got charging to find out.

The concept is simple. You charge the battery accessory, which you can then use when the iPhone is running low on power. Rather than an iPhone case like the Mophie Juice Pack Air, you get a small matchbox-sized battery that plugs into the dock connector. The matchbox battery is charged itself via an AC adapter or cigarette lighter adapter so you can charge it via the wall or in the car.

Both the AC adapter and car adapter are as compact as they can be and both come with a USB socket allowing you to charge a second device - handy in the case of the AC adapter because it means you can charge your iPhone's battery at the same time. A small magnet in both the chargers and the battery pack keeps everything in place when charging.

The battery pack itself as five green LED lights so you can see the status of the charge. You can only see the charge status when the battery is plugged into a charger or an iPhone/iPod. It isn't a big thing, but it would have been handy to be able to see if it needs charging without having to connect it to your iPhone.

In use and the battery offers a full charge as promised, but unlike the Mophie Juice Pack Air, we wouldn't be comfortable using this on the go and especially when it's in a pocket.

While it easily fits into the dock connector, attaching a matchbox-sized device to the base of your iPhone makes for a long phone. It isn't practical having something so long and fragile in your pocket. We were constantly worried that it would snap off and leave the dock connector in the iPhone rendering everything useless.

The end result is a battery that you feel you can only use at your desk or in the car, or basically anywhere you know you are going to be sitting for the next hour. It that's the case, you might as well just plug the iPhone in to a wall socket and be done with it.