The obvious solution was to buy a folding solar panel. It would deliver the power I want and also fit into the car. However, have you looked at the price of folding panels? They run about 3 times the price of a non-folding one at the same power output. No thanks.
So what to do? How about I build my own!
So that's what I did. I was able to source some 40W panels from Amazon for $55 each including shipping. A continuous or "piano" hinge, a pair of sash window locks and a handle were all that was needed to complete this project.
Here we see the back side of the panels. I used the hinge as a template to drill holes for the rivets I used to secure the hinge to the panel. Once the hinge was installed it was on to the wiring. The panels had a nice box on the back where the connections were made. Opening the box revealed 2 screw terminals. It was a simple job to add a pair of ring terminals to one of the wires and connect it to the other panel's junction box.
So what was the point of making this? Look at the picture below. This is me and my telescope equipment. I took my family to see the Great American Solar Eclipse (August 21st 2017). Powering their devices and all of my telescope gear, laptops etc took quite a bit of power. I was able to do this by using a large deep cycle marine battery and this solar panel (and the relevant charge controllers etc). Look closely just below the bottom left corner of the black box housing the laptop. You can see the panel on the ground.