When I built our adventure trailer the power source for the 12volt gear is off grid "solar" which I have been happy with. But here's the issue with solar, you need sun light to charge the battery or batteries, so during the late sp...ring thru summer months in early fall, here in Arkansas the Ozark's are in full foliage "tree's leaf'd out" so we Sally & I have to camp on ridge tops to get the sunlight for charging our battery. Late fall & early spring the Ozarks are in fall mode no leaves, so my solar system works well, even though some days are overcasted my battery is fully charged. So I decided to build a portable 110 ac \ 12 volt dc converter box to charge our battery in months that the tree's are in full foliage. I built one for my bowfishing boat years ago & it works extremely well keeping 2 31 series 12v. deep cell batteries charged with my 2400watt inverter generator. Power Max 55watt Converter: 3 STAGE CHARGING SYSTEM: provides an automatic charging system in three steps. 1.) A fast charge to bring a good, drained battery back up to full voltage rapidly "Boost". 2.) A standard charge to bring the battery up to a full charge at a safe rate to prolong the life of the battery and provide power to run 12V lighting and appliances in the vehicle/device ("Normal") 3.) A trickle charge to keep the battery fresh during times of load inactivity ("Storage"). The charger automatically changes modes to accommodate changes in conditions.