The flashing of the middle LED (every 2 - 3 sec.) signals the stand-by mode of the lithium pack. If you want to switch off the flashing during stand-by mode, you can activate the "LED OFF" function before exiting the Lenz heat app. After exiting the Lenz heat app, the LEDs on the lithium pack no longer flash. Nevertheless, the lithium pack automatically switches to power-off mode after the time specified in the operating instructions. The LEDs can be switched on again via the Lenz heat app or the LEDs flash again as usual during the charging process.