There is two ways I can do it on my boat. The batteries are for my epropulsion outboard. I have two chargers of roughly the same output. One is a 120 volt model that I can connect to my Victron 500 watt inverter. The inverter is just enough to run the charger. Or I can use a 12 volt to 48 volt charger that plugs directly into the boat's 12 volt system. Which is more efficient?