Looks interesting and very simple. Makes me wonder why no one else has tried this method before. I have a battery tender negative lead on the very nut they want you to connect this thing to. I wonder if that would cause problems. I need the battery tender to remain in place I rarely drive my truck except when I need a truck which is not often. It is not a daily driver. So a battery tender is needed on it. 1 year old truck and only 6800 miles on it.