Hmm, going by Googling the weight of a Tesla (1600 - 2000kg), and going by the 100W camping solar panel I have that ways 3kg...

I could maybe fit 6 of these rectangles on the roof of a car, so 18kg for 600W. 600W would generate 3kWh/sunny day.

So we've increased the weight by 1%, and get about 5% extra range per sunny day.

Seems like a decent trade off? You could probably even offset the weight by reducing battery size a little, as you need to carry less charge if you can top up power as you go?

Self charging from solar allays the fear that if you can't charge your car you won't be completely stranded. Fitting solar charging stations everywhere is a different use case really.