[Sprinterman]

Does anyone know if there is any difference between 100 and 13.7v as regards to brightness? I’ve tried both but can’t distinguish between them, I’ve set it to 13.7v, I’m guessing these are the highest brightness settings

[Billfitz]

100% is whatever the alternator output is, usually 14.5v. LED brightness isn't affected by voltage anywhere near as much as incandescent, part and parcel of the difference in how they produce light.

[Sprinterman]

So 100 or 13.7 won’t change the brightness, or any voltage settings? The alternator determines the voltage? So these settings above are irrelevant?

[Billfitz]

They'll have some effect but not a lot. Incandescent brightness is determined by voltage, LED brightness is determined by current.