TechRadar.com - Deep into technology

Your iPhone battery life can drain away alarmingly quickly, especially if you use your iPhone for watching video.

The Visparts Backup Battery for iPhone plugs into the dock connector to recharge your battery for when you're almost out of juice. It's styled just like the iPhone on the front, complete with glass panel, metallic edge and black plastic on the rear.

Not very secure

You need to charge the Backup Battery for one hour using the standard iPhone docking cable, then, with the Backup Battery attached to your iPhone, you can start making calls almost immediately, so you don't have to wait for the charging process to finish.

We found that it charged an empty iPhone battery to about half.

But there's one fundamental flaw: you'd expect the Backup Battery to feel secure once attached to your iPhone, but it wobbled alarmingly when connected and, because of this, we didn't feel confident handling our iPhone with the Backup Battery attached.