This product is a voltage controller, which turns on and off the output through a relay, which only acts as a switch and cannot change the voltage. You can freely set the charging or discharging mode and set parameters. For example, when the battery voltage reaches the set voltage, the module automatically disconnect to avoid battery over-discharging and prolong battery life; In addition, you can also set the charging and discharging time. Unlike other LED display modules, this protection module comes with an LCD high-definition display, which can clearly display voltage, voltage percentage and time. With 30A high current relay, suitable for any 6-60V variety of batteries and Lithium batteries. That means, after a charge or discharge, the interval between turning on again. The time range that can be set is 0-999 seconds. Colour: Blue Material: Metal Package Contents: 2 x Voltage Testers Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.