Replacing alternator with solar panel array on roof?

[gascort]

I'm planning on getting a ~50W panel to mount into the roof of my wagon. I'm going to put the alternator in circuit with a small lawn mower battery, the computer, ignition, fuel pump, engine cooling fan, and injectors.
I'm going to keep the solar PV panel connected to a deep cycle battery and then to all the non-integral parts of the car (starter, headlamps, parking lights, stereo, blower motor....) and have a switch between the two systems that I can connect for long road trips. This way, I can always get the car to go, even if the deep cycle battery or PV system fails somehow. From the previous post, I don't think the essentials will bog down the alternator too badly, and I'll be able to maintain use of the alternator's slightly higher voltage for my ECU and injectors, which I believe to be important for economy.

[orange4boy]

Gascourt,

Are you sure you can isolate all those functions? My personal preference is to keep it simple. You never know what is connected to what in wiring harness. Unless you happen to be an electrical engineer then fill your boots.

The frictional losses in the belt would surely outweigh the slightly cooler spark and the fuel pump is designed to maintain a certain pressure regardless of voltage ( as long as it's not too low)

But I'm a bit of an idealist. I'm removing all the parasitic drag off my previa. Bye Bye belts!

[orange4boy]

I found these interesting nuggets of info in

"Automotive Electrical Systems Circa 2005
By John G. Kassakian, Hans Christoph Wolf, John M. Miller, and Charles J. Hurton
Demands for Better Fuel Economy and more Electric Power are Driving Cars to Multiple Higher Voltages"

IEEE Spectrum: Automotive Electrical Systems Circa 2005

"Even more to the point, the U.S. Corporate Average Fleet Efficiency (CAFE) standard prescribes a maximum fuel consumption rate for cars sold in the United States. The Federal government assesses a penalty of US $5 for every 0.1 mile per gallon (0.04 kilometer per liter) below 27.5 mi/gal (8.55 L/100 km) on every car the manufacturer sells. A 200-W electrical load accounts for about 0.4 km/L in the FTP 75 cycle test; so, if a manufacturer is delivering 25-mi/gal (9.41 L/100 km) cars, for example, it can justify spending more per vehicle on components to improve electrical efficiency."

Also:

"Improving the electrical system's efficiency so it lops 100 W off the average electrical load has the same effect on fuel economy as reducing the car's weight by 50 kg, as measured by the FTP (Federal Test Procedure) 75 standard profile of starts, runs, and stops"

and the real kicker:

"At present, when U.S. and European fuel economy tests are conducted, only those electric loads essential to the operation of the vehicle are active—that is, the ignition and engine electronics. Lights, air-circulating blowers for the passenger compartment, entertainment electronics, power windows, and so forth are all turned off for the tests."

That last one has changed slightly in that now they must run the A/C for a short part of the test but still no other electrical loads are required.

Anyone still not clear as to why new cars often don't live up to their mpg ratings.

[gascort]

Originally Posted by orange4boy

Gascourt,
Are you sure you can isolate all those functions? My personal preference is to keep it simple. You never know what is connected to what in wiring harness. Unless you happen to be an electrical engineer then fill your boots.

I should be able to isolate everything at the fuse panels, using some male and female connectors. I believe I only need to do this to 5 fuses. Shouldn't take more than an hour.

Originally Posted by orange4boy

The frictional losses in the belt would surely outweigh the slightly cooler spark and the fuel pump is designed to maintain a certain pressure regardless of voltage ( as long as it's not too low)

You are correct, these should be fine. The speed of everything in the computer is driven by the voltage that serves it, though, and since I've seen sensors, etc. get thrown off by voltage problems before, I don't want to mess with it if I can avoid it easily.
PLUS I need the car for occasional trips to see my family in Kansas City, which is some 250 miles each way. This way, I don't have to worry about stopping to charge up or put the belt on, etc. with the wife and baby in the car. I already commend my wife for riding around with me in the car.

[gascort]

Originally Posted by orange4boy

"Improving the electrical system's efficiency so it lops 100 W off the average electrical load has the same effect on fuel economy as reducing the car's weight by 50 kg, as measured by the FTP (Federal Test Procedure) 75 standard profile of starts, runs, and stops"

Interesting find!

Originally Posted by orange4boy

"At present, when U.S. and European fuel economy tests are conducted, only those electric loads essential to the operation of the vehicle are active

these are the ones I'll keep on my alternator - essentially

[orange4boy]

Quite right,

What you propose is a good balance between reliability and economy. My trips are 100km max, but if you are going 250miles... that's too far to rely on 'should work ok'.

Good luck!

[MetroMPG]

Originally Posted by orange4boy

I found these interesting nuggets of info

Good nuggets for sure. Thanks for posting them.

[cfg83]

orange4boy -

Originally Posted by orange4boy

...

Following info may be useful

Accessories approximately current draw:
- Air conditioner 12-20Amp
- Brake lamps 3-6 Amp
- Cigarette lighter 10-12 Amp
- CDI ignition 6-36 Amp
- Dome lamp 1 Amp
- Electrical fans 6-25 Amp
- Electrical clock 1 Amp
- Electric fuel pump 7-15 Amp
- Electric water pump 3-12 Amp
- ECU/EFI 10 Amp
- Headlights two low beam 8-9 Amp
- Headlights two high beam 13-15 Amp
- Horn power circuit 8 Amp
- Heat defroster 6-10 Amp
- HEI ignition 6-10 Amp
- Ignition coil 5 Amp
- Instrument panel 2-4 Amp
- Nitrous solenoid 5-15 Amp
- Power seats / Power windows 25-50 Amp
- Stereo HIFI normal 10 Amp
- Starter motor, normal cranking 125-250 Amp (fully loaded battery)
- Starter motor, initial engine turn over 500-800 Amp
- Throttle stop 5-15 Amp
- Trans brake 12-20 Amp
- Turn signals 5 Amp

This is a cool list. Some are "low frequency" loads like the turn signals, but they can still add up. My Saturn DRLs use the high beams, so I disabled them. I don't know if they were at full power under DRL state, so I only give myself a 5-10 Amp credit for that.

CarloSW2

[MetroMPG]

PS - welcome to the forum orange4boy.

[Tourigjm]

Originally Posted by gascort

I'm planning on getting a ~50W panel to mount into the roof of my wagon. I'm going to put the alternator in circuit with a small lawn mower battery, the computer, ignition, fuel pump, engine cooling fan, and injectors.
I'm going to keep the solar PV panel connected to a deep cycle battery and then to all the non-integral parts of the car (starter, headlamps, parking lights, stereo, blower motor....) and have a switch between the two systems that I can connect for long road trips. This way, I can always get the car to go, even if the deep cycle battery or PV system fails somehow. From the previous post, I don't think the essentials will bog down the alternator too badly, and I'll be able to maintain use of the alternator's slightly higher voltage for my ECU and injectors, which I believe to be important for economy.

I've heard that the next gen prius will have a solar system to run all the "non essentials" as an option. so you are definitely the only one with this idea. How long do you estimate it will take to recoup the price of the panel/bodywork in fuel savings?