Solar cell panel on the roof..?.
 

I see they are selling 200 watt panels nowadays.
Like the SANYO HIP-200BA3 panel..
http://store.altenergystore.com/Sola...yo/diagram.gif

So, since they cost a lot, I was thinking about the best way to deploy one
of these new panels on the roof of my little SUV..

A power control unit that converts down to 12-15 volts and can steer the
power to where it's needed.

1.The control unit would only power up if the panel was supplying few watts from the sun. (Self powered).

2. If the ICE was on, the battery voltage would be monitored . The voltage
to the battery (from the panel) would be increased until it was slightly
above the monitored voltage. (It would take over for the alternator,
as much as possible, thus reducing engine loading).

3. If the ICE was off, and the air temperature was hot, the controller would
1st charge the battery as needed and 2nd power up cabin ventilation fan(s)
to keep the car cooler.

4. If the ICE was off, and the temperature was cold, the controller would 1st
charge the battery as needed and 2nd apply power to an engine block heating element.


I was also thinking about what happens when the car drives under a bridge etc.
Where the sun is blocked out. Instead of the controller falling off line,
perhaps a 12V 'bridge' niMH battery could be useful.?.
(The niMH weight limit should be under 5 or 10 pounds).
It might be useful just to run the cabin ventilation fan if you parked in the
shade for an hour at the mall..

You probably won't get enough electricity out of it to make up for the extra gas you burn because of the added drag. Leave the solar cells home, sitting on your roof where they'll generate power whenever the sun is shining.

If done right, I don't think they will produce that much more drag especially on an SUV body (which aren't renown for their aero anyways). But as to the gains... not sure. I would use a solar rig set up to send power into a deep cycle battery and from that run my appliances (ie a small fan)

Something like this...
"How to make a solar power generator"

But I'm all about temporary gadgets that can be deployed and withdrawn at will. I'm not saavy enough to wire it into the car itself.

That's a good idea, but when I'm at home, electricity doesn't cost that much..

But, when I'm out on the road, driving up a steep hill at 40 MPH,
how much is electricity costing (in gasoline) to charge my car battery,
and provide electric power to the car's electronics??

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The drag.. That's a real problem. But not one that can't be solved..
I've seen some aftermarket PV setups that looked like they
were painted on the roof.. Not much drag at all..
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I think there are guys who have taken out their alternator completely
and charge their car battery at home every night..

A good low profile solar panel might really be useful for that mod.
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If it's not practical now, how about when the 300 watt panels come out? :D

Those tiny panels can barely run a fan..
To get 200 watts out of those little portable panels, you would need
40 of them. At $3938.80 that's $19.69 a watt.
You could buy a Sanyo panel for about $5.52 a watt..:thumbup:

if you mount the panel flat then it will never get full sun, it would instead be getting 7/10 of full sun and thus have 7/10 the output so your 200 watt panel would never put out more then 140 watts of power under perfect conditions.
there are charge controllers out there that do basically what you are asking, giving you a dump load when your battery is full, off the top of my head I don't have one to recommend but an isolator diode before the charge controller could work and be easy to rig up to split the power to the fan/heater.