The battery pack can be recharged using the solar panels in the bag, the included AC travel charger, or the car charger. Which means it is just as useful in the city as it is traveling, hiking, or camping. You can transfer power stored in the battery pack to your device whenever you need it. Charge Indicator: This indicates how much charge is left in the battery and also that it is receiving a charge. Voltage Converter: A voltage converter switch on top of the battery pack allows you to adjust the power output to suit the device being charged, 5, 6, or 7.2 Volts. Virtually all cell phones, most PDA's, and USB charges run at 5V. The 7.2V setting is useful for devices like larger digital cameras and iPods, or when using a car charger. For more information on selecting the correct voltage, see below. LED Torch: There is a very bright LED torch on the face of the battery, which lasts approximately 55 hours on a charge. The battery pack clips inside the back pocket of the bag, and can be removed for use separately. It is also sold separately with standard adaptors and chargers.