I have it hooked up to one of those portable jump start batteries. It shows 13.5 volts on the display. No, I haven't tried it outside yet, just in my garage under florecent lighting. Right now I am going through the manual to try and get used to all of the display possibilities. I have had 2 Hbird's since the mid 1980's and still have a Lowrance X-67c that I like, but the GPS is all new and all Greek to me for now.