This is the fourth generation power board I have built for the van. It has been an exercise in iterative design. Fortunately, the blue gum chopping boards, which each stage has used, are easy to replace. The first, second and third designs all worked but after using them for a while I decided to remove the features I did not use and add others which might be useful.
The previous design had the unplanned issue of connecting the engine battery and home battery together if you turned them both on at the same time. This was sometimes of use when I needed to charge the home battery from the alternator. In this design, I added a button to connect them deliberately. The same button also allows you to use the USB and 12-volt chargers sockets on both sides even if you only want to use one battery.
After wiring it up I discovered the unplanned bonus of seeing how much current is flowing between the batteries via the chargers. This board also provides other useful data including the current I am getting from the solar panel. This has been a mystery for years as even the solar controller display does not give this reading.
I have also built some custom shelves to maximise storage in the van. These improvements should give me the ability to survive a whole month photographing in remote locations before needing resupply. This will come in handy in the second half of 2019 as I hope to be driving across many Australian deserts on my way to the start of World Solar Challenge in Darwin.