The Eco Energy 7 amp voltage switch protects your batteries from being excessively discharged. The input voltage is constantly monitored. When the input voltage is above the ON set point (typically 13.3 volts) the load will be turned on. When the input voltage is below the OFF set point (typically 12.0 volts) the load is turned off to protect the battery from being discharged excessively. The voltage set points are adjustable. Custom voltages from 6 to 24 volts can be ordered. Five year warranty.