The Philips Respironics SimplyGo Mini External Battery Charger allows you to charge additional batteries outside the concentrator while the device is charging another battery. This gives you the option to charge extra batteries to take with you and quickly change batteries on the go! The external batteries are small and can be easily carried in the SimplyGo Mini backpack or in an accessory bag. This external battery charger uses AC power and comes with all necessary cables. The external charger uses only 120 Watts of power when charging a battery.