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Third Rail System for iPhone 4 review: One battery to power them all

CNET Editor Dong Ngo's take on the newly announced Third Rail System battery pack solution for mobile devices from Third Rail Mobility.

Third Rail Mobility's Slim Case piggybacking its Smart Battery .
Third Rail Mobility's Slim Case piggybacking its Smart Battery .
Dong Ngo/CNET

All the money you have spent on cases and juice packs for the iPhone 4, or any smartphone that you have for that matter, only makes it that much harder to move on to a different device. This is what Third Rail Mobility, a new accessory maker for smartphones, intends to change.

The company announced today its very first product, the Third Rail System power solution for the iPhone 4, also known as the Third Rail Slim Case for iPhone 4 with Slide-on Smart Battery, which works not only with the iPhone 4, but also with most, if not all, mobile devices that charge via an USB cable.

Now playing: Watch this: Third Rail Slim Case for iPhone 4 with Slide-on Battery

The system includes a Slim Case that fits just the iPhone 4 and a Smart Battery that can clip on the case and stay firmly that way to form the juice pack. The battery can be taken out of the case easily and the idea is you clip it back on when you're done with talking, surfing, gaming or texting, and are ready to tuck the phone away, even though you can still do all those things when the battery is clipped on.

The best thing about this battery is the fact that it comes with an USB adapter that has a standard USB port, like those found on the back of a computer. With this adapter, the battery can power any other mobile device that charges using a USB cable. Also, the battery can be used with any other Slim Case that Third Rail Mobility will release in the future for other smartphones.

In addition to that, more than one battery can be stacked on top of one another to increase the power capacity. Third Rail Mobility says that up to six of them can work together. Each of them can carry enough juice to charge the iPhone 4's internal battery from empty to about 65 percent full.

This new concept of separating the case and the battery and making them work smartly together means that you won't ever have to get a new juice pack when moving to a new device. Now you can keep the battery, which is the most expensive part, to use it as a backup power source, or get a new Slim Case for the new device and clip it on.

It also means that when the battery deteriorates, which batteries do over time, you'll need to replace the battery itself, not the whole package, including the case.

The Third Rail System for the iPhone 4 is available now and costs $90 (it includes one Slim Case for the iPhone 4 and one Smart Battery). You can also buy the case by itself for $40 or just the battery (with an USB adapter cable) for $60. To learn more about how this new product performs and other features, check out the full review.