I'm sold on the voltwatch unit, espesially on bigger heavier planes that suck up the battery juice faster. I always check the battery with load before flying and after 5 flights. I installed a Voltwatch under the canopy of my 60 size SeaFury. After the 2nd flight the Voltwatch had 2 green lights left so I went up again. After the 3d flight the last red light was the only one on! I parked the plane for the rest of the day when I saw that. It turned out I had a bad cell in my battery pack. As far as I'm concerned the Voltwatch save my plane. I never would have suspected that the battery pack would quit after only 3 flights, especially when it read good with a load before I started flying!