How literally and figuratively green is this? The device is both a re-chargeable battery and USB charger. The single pack comes with one battery and charger for £17.95 (~$ 25.00.) The double pack includes a double charger and two batteries for £24.95 (~$35.00) and will fit into one USB port. The description doesn’t say how long a charge takes or how long the batteries will last, but hey, you always have an extra port, don’t you?