Fangrui Product Details Description/features: Usage 1. Connect The Positive And Negative Terminals Of The Display Board To The Positive And Negative Terminals Of The Tested Battery, And Gently The Red Button With Your Fingers To Light Up The Led Light To Display The Real-time Battery Level 2. Release The Finger And Wait For 3-5 Seconds For The Led Light To Turn Off. When Static, It Does Not Consume Any Power At All 3. With Reverse Connection Function, Even If The Positive And Negative Connections Are Reversed, It Not Burn. Just Adjust It. Lithium Battery Group Displays Battery Parameters: (the Following Data Are Reference Values With A Error Range.) Warm Sound Prompt: The 3.7v Lithium Battery Uses One Red Power Indicator Light And Four Green Battery Indicator Lights (for Other Voltage Ranges, There Is One Red Power Indicator Light And Four Blue Battery Indicator Lights) Specifications: Material: Abs Color As Shown (n Represents The Number Of Battery Cells) The Power Indicator Light Is Red Battery Voltage N X 3.3v Lights Up