Why isn't no one trying to mass-build an electric car with a solar panel on the top?

Pretty much an expense thing.
Silicon is out as a solar cell option because silicon panels would be too heavy, offsetting any gain in generation by the fact that the car would have to expend any extra energy collected to get the car moving. That leaves us with a variety of thin-film solar cell technologies like CdTe, CIGS, Dye-sensitized, Organic, etc. All of these are significantly more expensive and slightly to significantly less efficient than silicon cells.

Let's do the math to show why it's a little used concept. My Mitsubishi outlander has a roof area of approximately 5.8 m^2. The sun has a power intensity of approximately 1 kW/m^2 at the ground on a clear day, and the best production CIGS cell is about 15% efficient. That means, best case scenario, I make about 870 Watts if I cover the entire roof with CIGS cells and don't take any losses in converting the power from sunlight to electricity and in storing it in the battery. Now, If i had the plug-in hybrid version of the Outlander, I would have a 12 kWhr battery, meaning I would have to charge it for over 12 hours (in peak, noonday sunlight) to get the Outlander's all electric range of...33 miles.

It's not so bad as to be completely worthless, seeing as you could probably get a 15 mile charge if you parked outside on a clear day, but it's not worth the several-thousand dollar cost to most buyers.

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I thought this too a while ago. Seems like a no Brainer to me. Even if it increased range by half a mile or powered just one component like said, an improvement is an improvement.

Even if a panel is $1.5k and you'd need 3 panels on the car (roof, hood, trunk), plus necessary electronics, it cannot be more than $7k to do a car. When building a Tesla on their site, ordering one with a cream colored interior and OEM 21" wheels comes to $7.8k. I bet a supplemental solar option would be incredibly popular.

I know next to nothing about the batteries EVs use, so question... can the batteries be charged while being used?

All the solar array's on the space station wouldn't even charge a Tesla at full power. Consumer grade panels have an even more pathetic power density. A car roof full of solar cells wouldn't even run the radio. That's why solar roofs and solar roadways are memes.

>1 kW/m^2
That's only for a surface perpendicular to the sun's rays.

Yeah, I was making some simplifications. In reality both transmitted intensity and apparent angle would change throughout the day, which is why you would get at most 10-15 miles of charge for leaving it out the whole day.

>Arrays can produce up to 120 kW
>Top end Tesla has a 102 kWhr battery

Even with charging losses it would only take around an hour or two for the ISS's solar arrays to fully charge a Tesla. Increase that a bit if you're on the surface and can't access the full solar spectrum.

Solar is such an absolute irrelevant technology when it comes to cars that you can reduce a car to the absolute barest minimum in all aspects in an effort to do all that you can to save on weight while maintaining an aerodynamic design that maximizes surface area for solar panels to inhabit and you still end up with a markedly inferior car.

Some VW/ audi models had solar panels in their sunroofs, they were "powerful" enough to spin up the fan for the ventilation so if you park your car in the sun you had a constant but low airflow. sadly they didn't think it through so it also blows in icy air when parked in winter

VW offered a solar panel on the Phaeton sunroof, it was used to power the fans when the car was parked.

The extra weight would probably offset the benefits of any additional power, then there is the problem of the waste and recycling regulations that apply to cars, solar panels are very high in embedded GWP and toxic chemicals, this isn't too bad if you can install them where they are going to be the most efficient, but when you start to lay them flat and add in shade from trees and buildings they stop making any sense at all.

Why wouldn't you just turn it off in winter? It's an option in the A/C menu.

2 seater model currently in late design phase, this is a previously made solar racer.
In the near future, this could be production level polish.

The solar panels were only for air-conditioning and other in-cabin electrical stuff (like roof lights, seat adjusters, infotainment, dash display, etc.). They produce way too small an amount of power to actually propel the vehicle or recharge its batteries.

IIRC the Tesla cars have a similar feature as an optional add-on.

Nissan's FUCKING LEAF has one in the spoiler, it's absolutely tiny though. All it does is top off the 12v battery for the accessories, which the traction battery does anyway, so it boosts the range by a tiny fraction since the traction battery doesn't have to top off the 12v battery as often.