Smartphones are life-changing, but their tendency to lose juice so fast is infuriating. But the Intelligent Energy’s hydrogen fuel cell charger answers the prayers of frustrated smartphone users everywhere. The new device can keep an iPhone charged for up to seven days. By shrinking technology used to fuel eco-friendly cars, the company has created a pocket-size prototype that can fit inside an iPhone 6. The battery has been developed to combine hydrogen and oxygen to produce energy, with only water vapour and heat as its by-products. The unit even fits so nicely in an iPhone 6 that the only alterations needed are some ventilation holes so water vapour can escape. The charger can be refuelled with hydrogen gas through an adapted headphone socket.