I have been watching the install videos on YouTube..... some installers (when hard wiring) say to NOT plug the power cord into the power port at the top of the unit but to use the USB port on the SIDE of the camera. They said it must be plugged in that way for Parking Mode to work. Is that correct? The rear camera cord is tight with it there but it works. Ive been having an issue with my battery dying.... could this be why? Ive had power plugged into the top of the unit where it says POWER.