No matter what smartphone you own there will be always times when you need that extra bit of juice from the device, and today if you are the owner of the Apple iPhone 4 or iPhone 4S you can improve your battery life with a PowerJackit case bargain.

Cases that double up as an extra boost in battery power are nothing new but ones that cost as low as the PowerJackit case range from Expansys certainly are. The online retailer for everything mobile is currently at the time of writing offering a massive discount on the range of cases that cost only £9.99.

This is a reduction of £50 for some of the range that promises to double the battery life of your iPhone 4 or 4S. There is a huge range to choose from with all of them being extremely slim despite the built in battery, and will also protect your device as well.

The cases feature a 1,450 mAh battery built in that promises to provide an extra 7 hours of talk time, 10 extra hours of video playback, 40 extra hours of music playback, or 300 extra hours of standby time.

There have been a number of positive reviews from users that have already purchased one of the PowerJackit range of cases, with many that can’t believe there is a battery packed away inside the product. At the time of writing many of the range are still showing that they are in stock, but at this price and with only £1.79 being charged for delivery they won’t be around for long, and the full range can be found here.

Will you be getting one of these cases for your handset?