LOL I didn't even see the Stay N "Church".
Wrench, In my opinion, (and that's all it is), I don't have any problems with my batteries, and don't "need" it, but it is good piece of mind while on the water. I also feel it keeps your batteries lasting longer. I am on the same set of batteries that came in the boat since I bought it new in 2010. Same think with my last boat ant WalMart batteries. I get 4 or 5 years out of them, and sometimes more.
We have all been on the water that day that our batteries decide they are done and it makes for a bad day, whether fun fishing or fishing a tournament. At least if I have a battery decide to start going bad, I can turn on the motor and run a while and give them a charge. At least it will be enough to salvage a day.