My son's car was putting out 15.7v at the alt terminal. I checked the battery and it was roughly 13.5 IIRC. This is for a '91 Toyota Cressida. I was wanting to install a #4 wire from the terminal to the battery, as I read on a couple of sites that had articles on "The Big 3". Isn't this 15V+ a little too much for the battery?