USED FOR: This is a under-voltage switch controller used to turn off the power of load in the event of the voltage dropping below a set value OVER-DISCHARGING FUNCTION: This controller will help you to protect battery from over-discharging and prolong battery life WITH A LED INDICATOR: Undervoltage controller is designed with a LED indicator to show if battery is under-voltage EASY : Both turn-off and turn-on voltage value can be adjusted by simply pressing buttons HIGH SECURITY: When the battery voltage increases to a set value, the module will automatically turn on load again Specifications: Suitable Battery: 12V storage/lithium battery Control Current: 20A Control Precision: 0.1V Voltage Error: ±0.1V Size: 8*4.3*2.8cm/3.1*1.7*1.1in Weight: 41g(approx.) Restore to Factory Setting: At normal state, press and hold S1 and S2 buttons together, till display shows 888, to restore to factory setting.