We have a 40 amp smart charger, Powermania brand, that can charge 3 separate batteries. It came with a plug, to plug into a normal 120 volt AC outlet. But the installation instructions also state that one can cut off the plug, and wire it directly to the AC panel.
Although I'm not an electrician, I can't see how it would matter if it's plugged into an AC outlet or wired directly to the AC panel, as the amount of voltage should be about the same.
Frank