If you are fed up with your iPhone 4 battery losing its charge whilst you are out and about there’s a new iPhone 4 accessory case from Third Rail that features a detachable battery so you can extend your iPhone battery life.

According to an article over on Engadget by way of TUAW, Third Rail Mobility now offer the Third Rail System, which includes a slim case for the iOS smartphone along with a 1250mAh detachable battery pack that slides into place whenever the user requires a boost.

Price wise the Third Rail System for the iPhone 4 commands a price tag of $90, and the removable batteries can also charge other devices using microUSB.

Apparently though you can purchase the case separately for $39.99 and additional batteries if required for $59.99 each, the slim case weighs 26 grams and is available in black, and apparently the locking tabs that connect the battery to the case enables the user to stack up to 6 “Smart Batteries” and charge them all at once.

So there you have it the Third Rail System for the iPhone 4 one case and all the battery power you require, anyone tempted to purchase this iPhone 4 accessory?