New power supply for testing
The new power supply has arrived that I will use for testing. It is a 60A 13.8V voltage source. I’ve added a bunch of 100A diodes in series with it so that I can fake an ignition signal. The diodes should drop about 1.4V when the current goes through them so that it appears the device is on a battery and when I turn that red key I short the diodes out and it delivers the full 13.8V simulating the voltage delivered from the alternator.
This is helpful because the PDU can trigger actions based on this transition from 12V to 13.8V and back.