use Solar Sunroof as a trickle charger for battery

[ainarssems]

I am not sure how the cells are wired up in the panel and if the DC-DC converter is step up or step down.

Converter is in the sunroof itself and would require trim removal which I have not investigated how it comes off to measure output directly from the cells themselves. I did the measurements at the relay.

Usually solar cells produce about 0.5V each and are wired 36 in series for 18V output . Like I said I do not now how the A8 sunroof is wired but I would not bee surprised if it is also giving 18V from the panel and then using stepdown DC-DC converter to boost output amps but at lower voltage.

My guess is that if they wired fan directly to the solar panel of 18V it would be trying to draw too much amps because of low resistance of the fan and therefore dramatically reducing voltage and overall power output. Ideally you want to balance current and voltage near the max voltage where it produces most power in the region that i have marked with yellow circle in picture below, then use DC-DC converter which would then convert to optimal amps and volts for the consumer.