Key benefits Real time battery level display with a single press. Connect the positive and negative terminals of the display board to the tested battery, then press the red button to light the LED and read the level in real time. Safe reverse polarity protection. If the positive and negative connections are swapped, it will not burn; simply correct the connection. Low idle power consumption. After you release the button, the LED turns off within 3 to 5 seconds and no power is drawn when idle. Simple, tool operation. Quick to use for fast battery checks in the field or workshop. How to use 1. Connect the positive and negative terminals of the display board to the corresponding terminals of the tested battery. 2. Press and hold the red button to illuminate the LED and display the real time battery level. 3. Release the button; the LED will turn off after 3–5 seconds. When off, the device draws no power. Applications and scenarios Field service and on site diagnostics for vehicles, portable tools, and remote equipment. Maintenance and quality checks in workshops or production lines to verify battery health before use. Hobbyist and DIY testing for RC batteries, power banks, cameras, and other consumer electronics. Compatibility and notes Designed to connect directly via matching positive and negative terminals to standard display boards and tested batteries. No special tools required.