A solar panel is charging a supply battery. Voltage is 12-14V. Am I allowed to make a direct connection to the USB Type-C PD port? As I understand this would violate the PD protocol but what would be the consequences? If that doesn’t work what would be the most efficient way to connect to this power source? What if I would modulate the voltage to a fix value (9/12/15/20V) would that work?
Power from Battery
Not sure what you mean by that, here we cut the end off the cable and just use the c end and the other end it connected to a power supply.
What you are doing with the solar panel depends on if you have cheap gear. Many of those chargers just have a nasty and noisy square wave output. Not what you need. Either way you need clean DC and VERY well regulated. We have stuff out on remote sites with solar panels + battery and sine wave inverters (bumps upto 120VAC) so the computer gear runs off the “normal” power supply.