[ WORKING VOLTAGE]In order to avoid consuming the voltage of the battery being measured, the device can be separately connected to another power supply as its working voltage [CHARGE AND DISCHARGE PROTECTION]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 [INTERZONE VOLTAGE PROTECTION]This means that you can set the number of values between which the voltage disconnect or connect the relay [FIXED VOLTAGE MONITORING]When the measured voltage is higher than the set voltage value, the relay is connected, otherwise it be disconnected. Alternatively, you can set it to always stay connected manually power off, and the relay outputs a pulse signal when the measured voltage is equal to the set voltage (up and down 0.1V) PARAMETER: Working voltage: DC 12V Measuring Range: DC 0-99.9V Load current: 15A(Max) Load voltage: DC0-30V or AC0-250V Material: plastic colour: Blue Package Contents: 2 x Battery Voltage Monitor Module 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.