Many good suggestions on changing equipment etc., and most agree on which are the more effective methods of recharging. Reading between the lines though, it seems the OP is faced with his battery discharging while in storage.
The easy fix for this is to disconnect the batteries while in storage. He could disconnect the negative wire(s) each time he stores the RV or install a battery disconnect switch (BlueSea makes an excellent one) though you'd still have to contend with the battery's internal self discharge rate. This could be anywhere between 2-12% per month depending on type of battery. A small solar panel, connected directly to the battery, could take care of this without the need for any solar controller.
Just my two cents worth.
Mike