Energizer's Power Max P20 has a 4,000mAh battery that can charge other phones

Energizer is expanding its Power Max series with the P20 - a feature phone with a huge emphasis on endurance.

The Energizer Power Max P20 has a 4,000mAh battery that will last 31 days of stand-by or 40 hours of continuous 2G talk.

And if that's not enough, the Power Max P20 has a standard USB type-A that can be used to charge other phones.

The Energizer Power Max P20 has a 2.8-inch 240x320px display and offers a dual-SIM slot as well as a separate microSD one and packs a torch on its top.

There's a VGA camera, an FM Radio and an MP3 Music Player. All of this is run by a Spreadtrum SC6531E and 4MB of RAM.