Calculation of voltage percentage: battery voltage / (upper limit voltage - lower limit voltage) Key function: Up button: short press to switch display% and time, long press for 5 seconds to switch mode, charging mode: in, discharging mode: out Set button: short press to view the currently set parameters; long press set button to enter the parameter setting interface, setting up: upper voltage limit, DN: lower voltage limit, Op: conduction time, DOP: delayed conduction time (0-999 seconds), FOP: forced conduction time (0-10 seconds) in discharge mode Down button: short press the close / open relay enable (emergency stop function) to close, the LCD displays off, and the relay is disconnected. Long press the down button to set the LCD backlight status. L-P: off backlight is always on, on: backlight automatically goes out after 5-10 minutes; after it goes out, press any button to wake up. Parameter setting: 1. Press and hold the set key to enter the parameter setting interface; 2. After entering the parameter setting interface, short press the set key to switch the set parameters; 3. After the parameters are selected, they can be set by up / down key. Short press and long press are supported; 4. If you want to set other parameters, repeat steps b) and C); 5. After all parameters are set, long press set key to exit and save Color: black Material: ABS Package Contents: 2 x Battery protector 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.