As it is always a smart idea to have additional batteries on hand, but did you know with the help of the DC power supply the number of batteries you lug around can be drastically decreased. The DC power supply simply plugs into a cigarette lighter outlet in most cars, trucks, R.V.'s, SUV's, and boats, which then pulls power from the battery to recharge the XPO2. When using this method of charging it doesn't matter what flow setting you are on—all flow settings will work while the battery is being recharged, so your oxygen delivery is never interrupted. This essential accessory allows you to extend your time away from home with confidence, knowing you can keep your battery charged while on the move without any disruption to your oxygen therapy.