I got whats called a "Battery Bug". Simple, easy, plug-n-play, show digital readouts of how much energy use on last start and how much is left in battery. It never worked right, showed I only had 10% power left in battery, last year at the national, it started to alarm on the road, bought a new battery, old battety tested fully charged. I'm getting the unit from Summit, I'll be in that area a few times over the next few weeks so I'll check it out.