TFA never really addresses the question of, "given that 600-700W is about all that's going to fit on top of a car roof, how many days does it take to recharge a 50kWh battery pack?" Because that would also conveniently answer the question in the headline.
(And I'm being generous with the 700W on a car roof. I could squeeze about 450W on the roof of a 26 foot RV.)