solar panel & car efficiency

Is it possible, in any fashion, to add a solar panel to a car? Where would such connection be? (alternator?) Would the PCM have a problem with this?

No problem at all. There are all kinds of solar panels for cars. Some plug into the cigarette lighter, others get hard wired. I'm sure you could basically hook it up anywhere to a hot wire; alternator, starter, battery, fuse panel, etc.

Is there any chance of over-voltage (not specific to solar panels) or other electrical problems?

Not as far as I know. Some have noticed a slight voltage drain in the absence of light. Some have successfully incorporated a diode to prevent this, but I'm not by any means an electrical engineer.

I bought one of those solar panel battery keepers for my project car, setting the panel outside the garage door while the car is in storage.

It didn't seem to help at all - prob the darkness drain that Curtis mentions. Charge all day, discharge all night.

Since they were fairly cheap I bought another one and wired them together to effectively double the amperage. Slight improvement but not really enough to justify the effort or expense.

I desperately want to cover my roof with solar panels, just the same. The current calculations seem to "prove" that our entire nation might be freed from foreign oil if we all had panels.

Well to some degree. That's one reason to have hybrid cars. Imagine tring to drive across country in a extremely heavy overcast & at night!

Curtis73 is right, a diode would probably to the trick. Though it may possibly rely on the quality of parts also.

Did you try using solar panels while the car was running at all? That's why I wanna know. I mean charging the battery is always good, but I wanna take some load off gasoline.

Ah... well, the amount of power you would save the alternator would be so miniscule that might show up as a .0004 mpg increase. I didn't use math for that, that's just a sacrastic guess. Most of the alternator's draw is belt friction, bearing friction, and the little fan on the pulley. There is some friction from power generation, but rarely is your vehicle actually drawing enough power to make a significant load on the engine itself.

You can dramatically reduce belt friction by using a serpentine belt (if your car doesn't already have one). You can reduce energy load by disabling your DRLs, not running the stereo, or avoiding high-draw items like the A/C compressor, rear window defroster, or ventilation fan.

Adding a solar panel will save about as much gas as the difference between the interior light being on or off. Since you can't ever tell the difference in MPG with even your headlights on I don't think even 5 amps worth of solar panels will make enough of a difference to warrant the expense.

I do have to say, however; investigating ways of helping reduce foreign oil consumption and helping the environment are very wise, noble, and applaudable qualities. In a world where people are finding ways to get around the laws, and my personally being from a state where the laws don't work, its nice to see someone else interested in helping out voluntarily. Everyone lauged at me when I wanted to put cats on my 66 Pontiac. Bravo, deadbird. I'm happy that there are auto enthusiasts like us still around.

I don't think you're going to get that much energy out of a solar panel small enough to mount on a car. I've seen "sun-raycer" cars that try to use PVs and they are built severally light-weight (bicycle weight) and still crawl rather slowly, even on a sunny day.

Check this out. It's called "Electrocharger" and looks like a large alternator:

http://www.sigmaautomotive.com/electrocharger/electrocharger.php

but when you're accelerating it switches to act as a motor, using your battery to boost acceleration. Then when you back out of the throttle it switches back to be a generator. They claim it turns any car into a hybrid.

Actually I'm just looking into the technicalities because I have a few different ideas.