First a confession:

I love my iPhone and no other gadget even comes close. Yes, rival handsets may have bigger screens, faster processors, louder speakers or a more open software licence, but out of the dozens of handsets I've tried for this column none adds up to a better package. I'm such a fanboy I even used the iPhone as both a ruler and spirit level when putting up new shelves last weekend.

But the one bugbear they haven't solved in seven generations of iPhone is battery life. Leave an iPhone on standby and it'll run for several days on a single charge. But use it for games or as a sat nav system and the battery can be drained within a couple of hours.

It's this variability, rather than a consistent shortness of battery life, that catches many iPhone users out. Now the team at PhoneSuit, a Californian mobile accessory manufacturer, has developed the £75 PhoneSuite Elite 5. This rubberised, two-piece case fits over the iPhone to provide both impact protection and extended battery life from its integrated 2100 mAh battery. Crucially, that battery capacity is greater than the phone's internal battery, making the case good for a full 100% recharge of a dead iPhone.

With the case fitted, topping up the iPhone battery is as simple as touching a button on the back of the case. Five blue LEDs briefly illuminate to indicate the current charge level of the case, then it gets to work restoring the iPhone to 100% charge.

There are a lot of smart design touches, from the large port openings that allow headphones to be connected easily, to the subtle front lip that protects the glass screen from face-down impacts.

An integrated micro-USB port allows the iPhone to be synced and charged without removing it from the case. The only compromise here is that it forces you to switch from the Apple-supplied Lightning charging cable to the more generic micro-USB standard. A micro-USB cable is included in the pack, but that doesn't help if you have a Lightning-based speaker dock or in-car connection cable.

The PhoneSuit is a great solution for iPhone users who suffer from battery anxiety. I found the additional bulk of the case - which takes the iPhone from a svelte 7.6mm to a rather chunky 15.5mm - too much for my trouser pocket, so the PhoneSuit has become an occasional accessory for long days out rather than an everyday essential. Those with less tight-fitting trousers may well wonder what I'm fussing about.