One of the many complaints leveled at the iPhone design is the closed case, with no user-serviceable batteries. This has spawned multiple cases with inbuilt power supplies for extending the iPhone’s sometimes anaemic battery life. Granted the iPhone 4 is a great improvement over past models in the power department, but every little helps. But what if you don’t want a case with the added bulk of a battery?

Enter the new case and smart battery from Third Rail. The two-part system offers the best of both worlds – a slim iPhone 4 case with an attachable battery pack for when you need that little bit more juice – 1250mAh worth of juice to be exact.

The $90 kit consists of one case and one smart battery, with further batteries available for $40 each. If you do happen to buy two or more batteries, there’s the added benefit of being able to stack them to create either a power hub or to charge them both at the same time.

The Third Rail™ System includes the Slim Case for iPhone 4 with a slide-on Smart Battery. Understanding that your daily power needs may vary, The System allows you to add power when you need it and remove it when you don’t!

The Slim Case is a sleek, everyday protective case with a high quality, soft-touch feel. The Smart Battery can also function as a standalone backup battery to power other devices via USB Adapter (included).

In this world where we’re all carrying around multiple devices the smart battery can also be used as a charger for almost anything thanks to its micro-USB port.

With many put off of traditional battery-increasing cases by their bulk, the Third Rail case and smart battery offer a great alternative to carrying around a power cord and sticking near a power outlet.

(via 9to5Mac)

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