I run 3. Two for my trolling motor(that's all, nothing else) and one more for my cranking/other electrical. I have never had any problems. I do however charge all of my batteries before every trip. My boat is a 2060 WarEagle with 80 lb. Thrust Terrova. I have a 797si and a 787c2 and they both stay on all day. I also pump my livewell every 30 mins.