I don't know exactly what you are willing to settle for or what you want to pay, but, I have a Deltran Solar Battery Tender. It is not a charger in the sense every one here seems to be talking about, it is a tender that will maintain either my chassis or my house batteries IF they are fully charged to start with. I know and I acknowledge that it has little or no chance of charging a low battery.
At one time, folks that remove their batteries during the winter and keep them in a garage or shop were praising the Deltran Battery Minder(120vac) for keeping their batteries topped off.
I will admit that the Battery Minder will run 24 hours a day and may do a better job than the Solar Battery Tender but I have found it satisfactory between trips.
My opinion only, many have and will disagree.