Whether you are on vacation, running some quick errands, or taking your grandchildren to the park, the AirSep Focus External Battery will keep you up and running. Weighing a mere 0.5 pounds, this external battery adds virtually no weight to the concentrator. It can be clipped to your belt or waist to keep your AirSep Focus weighing 1.75 pounds, or it can be carried in the designated battery pocket on the AirSep Focus dual battery custom carrying case. The AirSep Focus external battery has an expected battery life of up to 1.5 hours. On the side of the battery there is an LED indication system that tells you your remaining battery life in 25% increments. It can be recharged using the AirSep Focus universal power supply using either AC or DC power, with the capability of charging two batteries simultaneously, charging one battery and powering the Focus, or simply charging one battery.