74, 232, stock alternator and BRIGHT LIGHTS

ok guys, here's the question:
i have a 74 cj5, 232 i-6, stock alternator and a pair of 6" round aircraft landing lights i want to mount on my front bumper.
these lights are 250 watts each and designed to operate on an medium sized airplane's electrical system. i think this means 24 volts not the 12 volt system in my jeep.
i had them mounted in 6" KC housings on a full size blazer about ten years ago. they were as bright as the sun, you could see and see them for miles, when i turned them on ALL THE LIGHTS (dash, radio, headlights...) ,except the landing lights, in the car would dim, the volt meter would dip below 12 volts and eventuly the wires leading to the lights melted.
i would like to know if anyone else has tried to put these in a jeep, what electrical upgrades would be necessary and should i just go buy a new off-road light kit b/c am i crazy for wanting to install these.
i feel the need to install these lights because, i think i need a new alternator anyway, i dont care about being legal b/c i am stupid and i think it would be really cool to have "aircraft landing lights" on the front of my five.
any help?
thanks
b

 

Well, let's look at the math. 250 Watts at 12 Volts ~21 AMPS PER LIGHT.
So those 2 lights are drawing approximatley 42 AMPS from your electrical system. You would need a 10 Guage or larger wire to handle that load. 8 guage would be better. Plus I doubt the stock alternator is bigger then 60 Amps Max output. If you want to use those lights then you will need a bigger alternator to power them.

As far as wiring, each light would need to be powered through its own 30A relay to keep from burning the switch out.

 

HudsonHawk gives some good advice. You need a much bigger alternator to keep from drawing down your battery while the lights are on, and heavy wiring, relays, circuit breakers, etc. My only quibble would be assuming these lights really consume 250W at 12V.

If these are incandescent lights, they may actually draw more current at lower voltage, since the resistance of the filament goes up with the temperature. Also, lights (esp. incandescent lights) need a lot of current at startup, and draw less current once they heat up. I'd suggest you use wiring, relays and circuit breakers rated twicw what the operating current is. I'd also suggest you measure the current, but that may not be practical, since this is more current than a typical hand-held DVM can measure.

I know you wrote you like the idea of big lights on front of your Jeep, but if you don't have the H-4 headlights yet, I'd suggest you get those first.

 

Tim, I had overlooked the loss due to lower voltage. You are right. If you build it to twice the load you think you need and it should be ok.

 

You can get a 100 amp 1-wire alternator at any performance shop. The stock alternator mounting bracket will require some mods. Since it's an excitable alternator (lights will tend to dim at idle), you have to remember to keep the revs up every once in a while. A good Volt Gage will show the charging rate.
I would run dual batteries - 1 manually isolated for accessories.
Pep Boys sells a 1200 amp gel cell sealed battery (Hawker Energy - Odyssey PC1200). You used to be able to have Hawker ship it. I can't read the phone number on the battery, but they are located in Maryland.

gj

ps: I run a 900 amp Hawker on my Shovelhead stroker. Hawkers are smaller than your standard lead/acid battery by about 30% overall.

gj

 

thanks for the replies.... i was going to upgrade my headlights too so when i do that it may be problem solved.
as much as i like the idea of saying i have aircraft landing lights on the front of the rig i think it may be a safer bet to get some lighting designed for the front of a car and keep the landing lights for another day.
thanks again
b