I definitely appreciate the English, as my German is not yet that good. Also, how would we choose between German/French/Italian? 
Don’t forget Romansh 
Hello everyone
Some of us build routers with solar panels and batteries in them.
So that the solar panels can capture enough light, we place them in a sunny spot. I have noticed that on a sunny autumn day, the temperature inside the housing can reach 40 °C. The batteries have a certain temperature range.
The one I use is 18650 with
discharged -20 to +60 °C
charge 0 to +50 °C
How do you deal with the heat in the housing if it is so sealed that it is waterproof?
I use a bimetallic strip (as here Solar carry-around node)
and heat shield with node box facing north as in this build Solar node for top of tall building using the Waveshare D solar power manager
and good tips here too