inverter
John,If you are charging with your motor and using a small inverter into your cigarette lighter outlets, it is pretty safe. If you are mixing shore power with an automotive charger, you are crossing the line.If you bring power onboard with a portable GFI unit, it be careful. Test the source for polarity and ground. Stop at a marine store or electric supply house and ask for a polarity tester and ask how to use it. They cost about 5 bucks. If the ac coming in has no ground or reverse polarity your ac is extremely dangerous. Only use the ac to power run things that are not connected to the boat or the dc system. If you connect an ac automotive charger to a battery you have severely increased your risk factor. I can not try to explain electricity here. no time no space and random thought can be misleading. Ray,An electrician on land does not understand the grounding, bonding, electrolysis and galvanic corrosion that takes place on a boat. A poor system can induce many corrosion facilitators.r.w.landau