The power supply needs to fulfill some critical demands and available solutions are quite bulky.

• Raspi needs to boots when igniton is turned ON
• Raspi needs to gracefully shut off when ignition is turned off
• Little to no power is consumed in the off state so the battery is not drained

Hours were spent on online research until a suitable solution was discovered in this blog. However, after ordering the PCB and soldering the components it turned out that the circuit was not functioning as expected. Once the ignition was off the Raspberry would immediately turn back on again. You can now find a modified and working schematic in the main repository.

The PCB and components need to be sourced and assembled by yourself. As stated in the original article, it is advisable to put a heatsink on the big transistor.