The AirSep FreeStyle 5 DC Power Supply is designed to be used while you are in the car. It plugs directly into the cigarette lighter or 12v socket. When plugged in, the DC power supply will not only recharge your AirSep FreeStyle 5's internal battery, but it will also power the machine at the same time. The AirSep FreeStyle 5 DC Power Supply will charge your internal battery and power the machine on all 5 pulse flow settings. There are no restrictions or cutoffs like you see with some other portable oxygen concentrators. This means you will never be without oxygen in the car as long as you have the DC power supply. This essential accessory gives you the freedom to travel and run errands with confidence, knowing your oxygen therapy will continue uninterrupted while your battery charges on the go.