Depends on how much power you can efficiently harness I’d imagine

A 220 watt solar panel will somewhat efficiently charge a 12v battery on a clear day

An electric car uses about an 800v battery(s) which is about 67 normal batteries. Let’s go ahead and say a small truck would take twice that and hey to make it a round number let’s call it 2000v. That means you would need a solar panel that can produce 440,000 watts or .44 Megawatts.

Some Google fu shows that to harness an entire megawatt(1 million watts) you’d need about 5000 conventional solar panels which on the ground would take up about 5-10 acres. Pretty impractical to put half that on the back of a truck I’d say.

You’d have to have some extremely efficient solar panels to make it practical methinks. Might work on smaller cars though. Anyone feel free to jump in here and get me with an epic slam though