They’re not—as long as the PV cells are a supplementary charging solution, in addition to wall charging, to the batteries. You’ll get a bit more range out while driving, especially when the car is a lightweight low drag design and PV cells may be the only thing needed to keep the constant 90 km/h speed in a sunny day. And when not driving the cells might be enough to get the 10…20 km or so commuting range back over your 8-hour workday.
But putting PV cells on a 3 ton electric SUV or pickup truck is stupid, it won’t do jack all due to the inherent inefficiency of such vehicles.
How does one find out what chips are in what USB sticks? Manufacturers don’t make this information available. At best you just find read and write speeds, usually just the max possible read speed and nothing else.