I'm a female and not quite sure how to use this thing. After watching a few youtube videos I tried it and got a yellow and then a green light so I figured I probably connected it correctly. I needed this to charge my car battery while I was away for 3 weeks. I used an extension cord to connect the battery to an outlet in the garage. I attached the battery to the driver's door handle. Everything seemed to be working fine. When I came back the green light came on (indicating the battery was fully charged) and the car started straight away with no problems. So glad I found this item. Much better than asking someone to start my car every few weeks while I'm gone. Incidentally, I also inflated my tires to more psi than I normally need to keep them inflated. When I came back the air dropped to the psi I needed.