I would look at a solar option. I use a single large panel from Harbor Freight with regulator to charge 2 trolling motor batteries. They are in a 24v configuration. I currently only charge one at a time and disconnect the joining cable (that connects the batteries in series to form the 24v). I do have another output from the regulator but haven't been able to determine the output current of that to try to charge the other battery. It has a LIGHT symbol on it as if it is for powering an external light.

It wouldn't do a quick charge but outputs 2+ amps so can recharge in a day. Charges even if cloudy.

good luck.