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(Pocket-lint) - You know the drill, you need to make a phone call on your iPhone and bam, the battery has run out. Energenie is the latest company to offer a solution with its iPhone 4/4S Chargegenie Sleevecharger.

Clip your iPhone into the Sleevecharger case and not only will your handset be protected from any bumps, scuffs and knocks, but you’ll also double the battery life. 

While the Chargegenie Sleevecharger is solely compatible with the iPhone 4 and iPhone 4S, Energenie has an alternative solution for handsets from other manufacturers. 

The Chargegenie 25 and Chargegenie 50 external batteries house a capacity of 2500mAh and 5000mAh respectively and can be used to top up the juice levels of mobiles, MP3 players, games consoles and digital cameras, with a range of different adapters included in the box.

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Indeed the Chargegenie 50 boasts enough power to charge a tablet device such as an iPad or Google Nexus 7.

energenie protective case doubles iphone s battery life image 2

The iPhone 4/4S Chargegenie Sleevecharger is available for £29.99, while the Chargegenie 25 costs £41.99 and the Chargegenie 50 £59.99. All three devices are available from www.energenie4u.co.uk.

Energenie faces competition from Mophie which recently unveiled devices that perform similar functionalities.

Do you struggle to get a full day's use out of your iPhone? Let us know in the comments below...

Writing by Danny Brogan.