The Heidelberg Energy display is difficult to see. The ESP should still have a free pin. This could be used, for example, to control an LED NeoPixel Ring WS2812 with 32 LEDs as a charge indicator. Since 5V has to be placed in the box anyway, you could use the voltage as the power supply for the LED. A simple running light during the charging process would be enough.
The Heidelberg Energy display is difficult to see. The ESP should still have a free pin. This could be used, for example, to control an LED NeoPixel Ring WS2812 with 32 LEDs as a charge indicator. Since 5V has to be placed in the box anyway, you could use the voltage as the power supply for the LED. A simple running light during the charging process would be enough.