Sonnet is a little coy about just how much extra playtime the 2,100mAh battery in its Volta add-on for the 5G iPod - and its recent update. It provides a set of "estimates" that don't quite add up. If it adds an extra 50 hours' audio playback time to a 30GB iPod, why does it add 60 hours more to a 60GB or 80GB model?

But what are we complaining for? With even a baseline 50 extra hours of listerning and, more importantly, 7-18 hours more video playback time, all for just £45, who's grumbling?

Volta connects to the iPod via a dock connector, but provides a slot of its own so the player can be charged and stocked with content while it's fitted into the Sonnet device. Sonnet bundles a USB-to-dock cable so you'll always have one handy, and the unit ships with side latches to hold the iPod in place. Four charge-status LEDs keep you informed how much playtime the Volta can provide before it drops out and the iPod's own battery takes over.

Volta is available now. ®

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