With 8 Watts of power, the Spark provides about an hour of iPad runtime for every hour in direct sunlight. The Spark includes a battery to store power. It holds one complete iPad charge and can be re-charged from sunlight or a wall charger. It has two USB ports, one with “normal” USB output of 650 mA and a second “high-power” port which puts out 2A. Without this, charging an iPad takes a very, very long time as the battery is about 5 times that of a typical phone.
Voltaic Spark Solar Tablet iPad Charger