A controller must be used! Otherwise, it may cause overcharging or over-discharging of the battery, affecting the service life of the battery. The function of the controller is to intelligently control the solar energy, battery, and load, and then maintain the battery, avoid overcharging, over-discharging, short circuit maintenance, etc., and intelligently control the operating time of the load. For more information, please refer to the controller manual. In addition, the load of the controller also has current requirements. The load of a 10A controller generally does not exceed 12A current. Relative to this, a 10A controller can support appliances below 120W, a 20A controller can support appliances below 300W, and a 30A controller can support appliances below 500W. Buyers can choose freely.