Good Old Daze

I have the above battery tender hooked to my car. It connects with a red and a black cable like most types and is connected directly to the terminals. My question is when the unit IS NOT plugged in for charging or maintaining, the green light on the unit stays on. On the unit it says that green indicates "connected to power:. Would that mean the battery is the power if not plugged in to an outlet? In other words is it normal for the green light to stay on when not plugged into a wall outlet? Thanks, hope someone has an answer.