Whether you have two or four batteries you will greatly benefit from the addition of the DeVilbiss iGo battery charger, as this gives you an additional method of charging—this is the only external charging method for the iGo portable concentrator. Now you can have a battery operating the iGo while another battery is being charged with the external charger. This is great for traveling patients, as they can go out and enjoy vacation while the additional battery is being charged back at the hotel for later usage when the first battery depletes. Not only does it benefit the traveling patient, but also patients that keep batteries in multiple locations such as at work and at home. The DeVilbiss iGo battery charger is both reliable and simplistic to use—a fully charged battery can be left on the charger without ever over-charging. When a battery is charging, a green light will flash for the duration of the charge cycle; once fully charged, the light will switch to a constant green. Be sure to place the external charger on a flat, dry surface near a wall outlet where it can be left without being interrupted.