Today was a day dedicated to the fridge and freezer. I had noticed that the fridge especially had very long run times, and was causing a bit of battery drain. When I had a look at it, the piping outside the actual fridge was covered in ice. This of course seemed a bit wrong, I was obviously wasting quite a bit of energy cooling down the air in the machine room!
So I did a bit of studying. Apparently a cooling system like this needs to have the right amount of carrier gas inside it. If the pressure is not right the system will not work well. Excess icing on the pipes outside the fridge indicates that the pressure is too high. In this case the coolant does not evaporate completely in the evaporator inside the fridge. Thus there is some fluid coolant leaving the fridge, which then evaporates in the pipes on the way to the compressor. This makes the system inefficient.
So all I needed to do to fix the problem was to let a bit of coolant out, which is easy enough. Getting it back in is a different story, so I was very careful in the beginning with how much gas to let out. Working in small increments and waiting maybe 10-15 minutes for the system to stabilize before letting out more.
This image shows the process when it is almost complete. You can see a small length of frost along the pipe in the center. When I started this pipe was completely covered in a thick crust of ice. As more and more gas is let out, the length of pipe that freezes gets shorter and shorter. And in the end the whole visible length of pipe is free from frost.
The compressor now runs significantly shorter times, while keeping the fridge cooler than before. Hooray!