Portable electronic devices such as laptops, phones and MP3 music players are great companions in the car – until the batteries run out.

You could buy 12V chargers for them, but that will come at considerable expense, so the easiest way to revive them while on the move is with an inverter. Plug one in to the lighter socket, and it turns the car’s DC current into 230V AC mains power. They all come with a three-pin plug socket, but some also boast USB outlets, which are ideal for MP3 players and phones.

However, don’t think you can use an inverter to power drills or heaters in the workshop, as they have limited output and are really only intended to work with electronic gadgets.

So, which is the best piece of kit to plug your PDA, Bluetooth headset or DVD player into?