Unfortunately I only have a single battery. I hope to upgrade to a dual setup soon. I worried my charger was under powered but I've never had problems with a dead battery. The "GUEST" charger appears to be a 6A/hr charger for dual batteries but when used for 2 batts it only supplies 3A/hr to each battery. So if you need 6A/hr like Jony indicates are you getting enough with the "GUEST"? Unless, you have a charger for each batt and can dedicate the full 6A/hr to a single batt? Nice setups to both you guys. I'm kinda clueless about this kinda stuff but looks like I may need a new charger...dang I have to buy something else for the boat .