This product is a voltage controller, which turns the output through a relay, which only acts as a switch and cannot change the voltage.Charging mode IN: By setting the upper limit voltage UP and the lower limit voltage ; when the battery voltage less than or to the lower limit voltage , the relay is turned on, and the charger starts to charge the battery; when the battery voltage greater or to the upper limit voltage UP, the relay is disconnected to complete an automatic charging; the relay is turned on, IN flashes, indicating that it is charging.Discharge mode OUT: By setting the upper limit voltage UP and the lower limit voltage ; when the battery voltage greater or to the upper limit voltage UP, the relay is turned on and starts to discharge; when the battery voltage less than or to the lower limit voltage , the relay is disconnected to complete an automatic discharge function; the relay is turned on and OUT flashes, Indicates that it is discharging.Note: This product is a simple voltage controller, which uses a relay to turn the output. It only functions as a switch and cannot be transformed.Function:Calculation of voltage percentage: battery voltage/(upper limit voltage-lower limit voltage)Button:UP button: Short press to switch to display percentage and time, long press for 5 seconds to switch modes, charging mode: IN, discharging mode: OUTSET button: Short press to the currently set parameters; long press the SET button to set the parameterDOWN button: Short press to turn off/on the relay (emergency stop function), after the LCD display is OFF, the relay is disconnectedtype: Battery protectorcolor:BlueMaterial:PCB+electronic componentssize:62 x 57 x 22mmPackage Contents:1 x Battery protectorOnly 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.