24v lights on a 12v system


by Guitarnut
Tags: lights
Guitarnut
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#1
Jun12-06, 12:43 AM
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Maybe this has been posted before but anyway

Im considering installing 24v aircraft landing lights on my jeep wrangler. (for off-road use.) What i would need to fabricate to make this work. I figure they will light up but i want them bright like they are supposed to be.
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Danger
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#2
Jun12-06, 09:09 AM
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You won't get full brightness out of them on 12V. I'd consider either series wiring 2 batteries together to get 24V, or use a secondary 24V aircraft battery. If you can, try tapping your alternator upstream of the regulator to pull 24V for charging. Remember to wire your lights in parallel so there won't be a voltage drop across the circuit.
Mech_Engineer
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Jun12-06, 09:33 AM
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Quote Quote by Guitarnut
Maybe this has been posted before but anyway

Im considering installing 24v aircraft landing lights on my jeep wrangler. (for off-road use.) What i would need to fabricate to make this work. I figure they will light up but i want them bright like they are supposed to be.
Theoretically, it is possible to go with a dual-battery system which could put out 24V, but my worry is overall power draw. How many amps do these things pull? How many watts? You should make sure you alternator can easily keep up, because if it can't you batteries will go dead, and if you are close to the full power rating of your alterantor, you could fry it after an extended period of time.

You might try going to an off-road forum and looking into auxillary lights such as Hella 500's, they're cheap and can use 130W bulbs. 4 of those, and you'd be a driving blind-o-ray.

berkeman
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#4
Jun12-06, 11:34 AM
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24v lights on a 12v system


Stick with 12V floodlights.
NoTime
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#5
Jun12-06, 07:53 PM
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Quote Quote by Danger
try tapping your alternator upstream of the regulator to pull 24V for charging.
Alternator regulators control the voltage by adjusting the current to the exciter winding. There is no "upstream".

Also aircraft landing lights are
A) Fragile and tend to have a very short lifespan.
B) Expensive.

I'd go with M_Es sugestion.
Danger
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Jun12-06, 11:25 PM
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Maybe the technology is different now. I know that most alternators now have internal regulators, but I figured that there must be a way to tap in ahead of them. I have a 120V converter that draws directly off of the alternator.
Cliff_J
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#7
Jun13-06, 12:08 AM
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Danger, it sounds like you're thinking of the regulator as a linear voltage regulator on the output of a generator, which is pretty much non-existant today.

If you look at a modern Delco alternator for example, it varies the duty cycle from 10% to 90% on a 400Hz pulsed signal that is responsible with energizing the field coils on the armature. So its like an indirect regulation, it changes the field strength and thus also the mechanical drag (which would be a constant RPM dependant drag for a different setup with single magnetic field level and requiring a linear voltage regulator). The stator and its diodes are directly wired to the output, simple and efficient too!

In regards to the lights, agreed with above as there are so many good choices out there for good off-road lights and the cost is likely going to be less than needed to setup a good 24V output that can handle that level of juice.

And while talking about alternators, if you decide to upgrade yours to handle the extra current draw, be aware that OEM spec alts make good output at idle, and some of the high-output types do indeed make more power at 2000 engine RPM but will sometimes make LESS OUTPUT at idle! Make sure you understand the idle output quality of the alternator you intend to buy!
Danger
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#8
Jun13-06, 09:40 AM
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Thanks, Cliff. The newest vehicle that I've owned was a '79, and the Camino is a '74-'76 mongrel. I did buy a new alternator for it, but I never bothered with how it worked.
Cliff_J
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#9
Jun13-06, 11:12 AM
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Even on my '71 Chevy, you could full-field the alternator by putting a straightened paper clip in a hole in the back of the case of the 60A alternator, the paper clip would ground out the field coils (normally handled by the voltage regulator) and then it would put out full power because it was full-field. That's according to my dad, diesel mechanic for years and the full-field was a crude test to see if the regulator had quit, but the voltage output and mechanical load on the motor seemed to fall inline with that assertion.

The PWM at 400Hz is from the GM service manual for my '96 CS144 model large-case alt, it seems all GMs today use the smaller CS130D alt so it might be slighly different, but I think they've been using some form of field control for a few decades now.

Sometimes it just amazes me that cars even worked decades ago with the technology available at the time, but then again they didn't expect them to go 100k without needing service either.


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