I did it that way for quite a while on my old boat. It does get tiresome with three batteries to connect. I went with a built-in eventually and still do in my classic. Much more convenient to pull down a hanging power cord, plug it in, and put it up for the night… As opposed to climbing up on the boat, hanging down into the bilge compartment to connect alligator clips, being careful to avoid reversed polarity and blown fuses in the leads, etc. Weight of the new chargers is minimal.
.
