Energizer Energi To Go TM brings instant credibility to a new category. Delivers a full charge Uses a patented intelligent management system that optimises power transfer from power pack to device which maximises the battery output. Comes supplied with two Lithium AA batteries which provide up to 4 times more talk time than Alkaline. Provides power to talk immediately even when phone battery is completely discharged. Blue light to indicate when mobile phone is charging. Reusable lightweight durable convenient easy to use portable and fast.