Key benefits Real time battery level display: Connect the display board to the battery under test and press the red button to illuminate the LED and view the current battery level. Energy efficient idle state: When you release pressure from the red button, the LED turns off within 3 to 5 seconds and no power is consumed in the idle state. Safe reverse polarity protection: If the positive and negative connections are reversed, the unit will not burn; simply correct the wiring and continue. Straightforward operation: Simple steps to check battery health without complicated setup or tools. What it does Displays the real time battery level by linking the positive and negative terminals of the display board to the corresponding terminals of the battery under test. Uses a red button to briefly light the LED for a live reading; releasing the button ends the display and saves power. How to use Step 1: Connect the positive and negative terminals of the display board to the positive and negative terminals of the tested battery. Step 2: Gently press the red button with a finger to light up the LED and display the real time battery level. Step 3: Release the finger; the LED will turn off after about 3 to 5 seconds. While off, the device consumes no power. Step 4: If the connections are reversed, the device will not burn. Simply correct the polarity and use as intended. Description and features Function: Provides a quick, visual readout of a battery's real time level via an LED on a display board. Safety: Reverse connection protection prevents damage if polarity is accidentally reversed. Power efficiency: Idle state uses no power; LED illumination is momentary only when the red button is pressed. Simplicity: No complex setup required; straightforward connection and a single button operation. Usage scope: Designed for checking the voltage level of a battery under test through direct terminal connections. Use scenarios Onsite tool maintenance: Quickly verify the charge level of cordless tool batteries during field service. Battery pack checks in repairs: Assess real time battery health during assembly or diagnostics of rechargeable packs. Hobby projects and prototypes: Monitor battery status for RC cars, drones, or other battery powered projects with minimal setup.