Yeah, I think your numbers are off, there’s no way my 10HP could burn a gallon in 15 minutes. It’ll run all day on 5 gal.
A diesel would run even longer...but weigh more.
Who said anything about a closed vehicle?
Your 10 hp generator puts out only about 5kW. It would take more than a day to charge your EV, and several tanks of gas. Besides that, your “all day” rating is only at half power - check the owner’s manual. That means two days running to charge the EV.
The picture is of a closed vehicle. I didn’t say anything.