Purpose
Provide ventilation to the driver and battery.
Requirements
Driver
Airflow
While no quantitative requirement is set in regs, I don’t think having a pinhole sized vent will pass. Since it is left to the discretion of the inspector, we should aim to size the vent and duct such that it would not “look unreasonable” if it was in an actual car. A 2in diameter opening + duct, or an equivalent cross-sectional area, sounds like a reasonable lower bound.
Filtration
While not required, since it is blowing at the driver’s face it would be nice if it did does not suck through fine particulate matter from the road. Intakes should also contain geometrical features to protect against water ingress.
Battery
Airflow
The intake/exhaust and ducting should aim to maintain a cross sectional area greater than a 4in diameter circle. Battery fans are approximately 6in in diameter.