You can, but it has a separate supply so you can use if it is not charged. So in short you can use it both ways. On a power cord directly to the OBD II port or untethered. I do like the charging base. You can hook up the dongle and move around with the scanner. I really like it. Have you seen Eric O use it on South main auto? He is who got me interested in it. The fact that he really liked it was what made me look at it.And can you use it right out of the box? Old high end scan tools do not need a battery to work they can use the cars battery through the OBD2 port. It would be bad to be using a tool with only its own source of power while doing a ECU update or what ever, and have the battery poo out during it.![]()