Good day. A coffee machine needs approx. 800 - 1200 watts of power. So it won't work. I need the part to charge batteries, for which it is sufficient without any problems.
I've been using a power strip where I've cut the plug and put a plug with a + and - connector without the ground. When I travelled, my children were able to connect their computers and cell phones to the power strip and charge them. I myself have taken a multi-socket where I cut the plug and put a plug with a + and - connector without the earth. When travelling the children were able to connect their computers and mobiles to charge.
According to information e.g. under [1] (as also with a competitor of Digitec Galaxus AG), the device weighs 0.8 kg.
[1] http://www.exista.ch/prodDocuments/300w_specification.pdf
Theoretically, you can connect a power strip there. You just have to consider the total power of the connected devices and that the car battery still has some juice ;)
What annoyed me a bit was that the socket is only 2-pole and has a "cover".