Purchased a Amptron 200 watt solar panel in addition to the existing 100w panel I had on my RV. The extra input has been enough power to keep the newly purchased and installed Amptron 2X150AH Lithium batteries almost fully charged under load even on overcast days. The REDARC dc-dc charger does its job while driving & the Amptron 240v 40 amp charger keeps the batteries up when not in use. Very happy with the size and robust construction of the solar panel. very unobtrusive on the vehicle.