I have a MinnKota 3 bank charger, Precision MK330PC . It charges Optimax 27M BlueTop batteries and does a great job. I tried Cabela's AGM batteries and they do not last. The Optima batteries are worth the extra expense. I plug mine in as soon as I park the boat. Being a guide, I use them a lot. I had my oldest BlueTop, which over 5 years old, checked yesterday. This advertized 800 CCA battery actually check out at 1100 CCA, after all theses years. When these batteries begin getting weaker, I replace them and keep them for my automatic gate and jumping equipment around the house. I have used some of them for over 10 years. Hope this helps.

The key is having a charger that charges the specific batteries you use. An AGM battery does not charge at the same heat range as a wet cell battery. Also, sealed batteries do not boil over and are much better to leave connect all the time.