This is an amazing charge controller! The 5 speed controller works like you won't believe! I had a 30 amp Harbor Freight Controller on my solar panel in my RV, after 3 days of idling and overcast skies my batteries dropped to 11.9 volts. After installing this Zamp controller with the same panels, batteries and weather, my batteries never went below 12.5 volts and they charged much faster with this controller.