using 24volt equiptment on a 12v system

C co Crusader 2/127 · **Posted:** Sun Dec 23, 2007 8:05 pm

I currently trying to figre out what i would need to do to run a set of truck-lite LED headlamps(military equiptment). They are the first full LED Headlamps in the world from what i found out. An thoeir retrofitting them onto all new and remanufactured HEMMT vehicles that Oshkosh truck makes. So I checked out all of the tech drawings that we have on them and it should be pretty easy to retro fit the kj for them. Im getting the NSN for them as soon as i get bach from my christmas vacation so that i can order them(connections with my units supply people is a good thing). The next problem I have to tackle is power. What am i going to need to do to step up the 12v DC of the stock system to run the 24v DC lights? Im looking for something small i can wire into each light so that their wired independantly like they are now. So if someone knowledgable with dc elictrical could give me some sugestions that would be awsome. If we could get this figured out i see some potential for a retro kit being made for the lib.

tjkj2002 · **Posted:** Sun Dec 23, 2007 8:10 pm

First they may not be DOT legal and you'd have to wire in a 2nd battery to properly run the 24v lights or they will be 1/2 the brightness they should be.

rickm · **Posted:** Sun Dec 23, 2007 11:00 pm

I would certainly check to see if they are legal to use in your state.

The current limiting and/or regulating circuitry may or may not be built within the LED unit itself, it may be external.

If all of the above doesn't scare you away from using those LED headlamps, then you should know that stealing from the U.S. military is most certainly illegal, and may even result in some jail time.

no wonder my taxes are so high every year.

p.s. yes, I was in the military for over 20 years.

Goglio704 · **Posted:** Sun Dec 23, 2007 11:07 pm

You might try googling the term DC voltage doubler. AC voltage changes easily with a transformer, but DC is harder.

JHCRASH · **Posted:** Sun Dec 23, 2007 11:11 pm

tjkj2002 wrote:

First they may not be DOT legal and you'd have to wire in a 2nd battery to properly run the 24v lights or they will be 1/2 the brightness they should be.

This is true ^,
It is pretty hard to convert it unless the lights have something with them its not really worth all the trouble, even if they do you would still need a second battery,its a pain.
I had the opportunity a couple years ago to get some of the headlights they run on commercial airliners for a very good price (nothing) they were nib and like 20 million candle power but 24v I was going to use them on my TJ but it was too big of a hassle.

C co Crusader 2/127 · **Posted:** Wed Dec 26, 2007 2:39 pm

tjkj2002 wrote:

First they may not be DOT legal and you'd have to wire in a 2nd battery to properly run the 24v lights or they will be 1/2 the brightness they should be.

i thought the same thing when i first saw them and wanted to put them on the lib. An right on the covers to them it says the DOT number and the ASE number. I probably wouldnt have cared about that a few months earlier but with my recent lighting ticket im pretty careful about it. Anyway they all check out fine. I called truck lite and they conform to all federal standard for photometrics. So their legal on the fed level and on the wisconsin level. other states im not so sure on. Now i was looking into the additional battery and i dont know if i want to buy an extra battery just for lights. It there anything else i could use it for like an air locker or something extra? I just dont want to waste all this space for a set of lights.

Hood297 · **Posted:** Thu Dec 27, 2007 7:45 pm

You could always relocate your battery(s) to the rear cargo area, or get some gel cell, unspillable batteries and mount them on their side underneath the rear seats...

It'd be a pretty serious project and pretty exspensive when you think about the lengths of heavy guage wires you would need, especially not to have a substancial amount of resistance. But it would also free up alot of space for fun stuff like air compressors.

C co Crusader 2/127 · **Posted:** Fri Dec 28, 2007 3:15 am

will a optima fit under the rear seat and still allow it to fold down? I pretty much trowing the converter or multiplier idea out of the window because well i dont know a darn thing about serious electronics like that. Any forseable problems with a second battery? How would i want to wore them?

tjkj2002 · **Posted:** Fri Dec 28, 2007 8:17 am

C co Crusader 2/127 wrote:

will a optima fit under the rear seat and still allow it to fold down? I pretty much trowing the converter or multiplier idea out of the window because well i dont know a darn thing about serious electronics like that. Any forseable problems with a second battery? How would i want to wore them?

You'd loose the ability to fold the rear seats down if you put a battery under there.

tjkj2002 · **Posted:** Fri Dec 28, 2007 8:18 am

C co Crusader 2/127 wrote:

will a optima fit under the rear seat and still allow it to fold down? I pretty much trowing the converter or multiplier idea out of the window because well i dont know a darn thing about serious electronics like that. Any forseable problems with a second battery? How would i want to wore them?

You'd loose the ability to fold the rear seats down if you put a battery under there.

Se7enLC · **Posted:** Fri Dec 28, 2007 10:01 am

If you went with a 2-battery system, don't forget that you would lose the ability to CHARGE the second battery. A normal 2-battery system has the batteries in parallel, so the charging system is still charging at 12V. Having the batteries in series means that one of those batteries is just hanging out to dry while the other one is wired up to charge.

I'm with everyone else that says "too much work".

However.... IIRC from my undergrad days, you can use a step-up transformer to go from 12V to 24V at the cost of a power loss and heat gain.

Here's an example product that does the 12VDC -> 24VDC conversion. It's only 2500mA, though, so probably not enough for those lights:

http://www.m-99.co.uk/Electrical/12v_Car_to_24v_Stepup_Converte/12v_car_to_24v_stepup_converte.html

The Staff · **Posted:** Fri Dec 28, 2007 11:16 am

rickm wrote:

I would certainly check to see if they are legal to use in your state.

The current limiting and/or regulating circuitry may or may not be built within the LED unit itself, it may be external.

If all of the above doesn't scare you away from using those LED headlamps, then you should know that stealing from the U.S. military is most certainly illegal, and may even result in some jail time.

no wonder my taxes are so high every year.

p.s. yes, I was in the military for over 20 years.

Good point right there in bold.

C co Crusader 2/127 · **Posted:** Fri Jan 25, 2008 12:11 pm

well i now have a solution to the 24v problem. Yesterday we had a few of the designers over in my dept explaining how to paint the new HEMTT-A4 thy brought over. An surprise surprise... its going to have led headlights too. so i asked then about them and they told me that its doesnt matter if you use 12 or 24v for powering the lights. They also informed me that they have about 5 or 6 pairs sitting in in the New Technology Development Center that their not going to need because they scrapped the project they were going to use them on. So $50 bucks a lite and a personal items pass and their mine. Ill be the only vehicle in the world using a full led headlamp system!(the HEMTT's weve been retrofitting them on wont be on the market for a few more months)

Neal · **Posted:** Fri Jan 25, 2008 12:57 pm

LED's operate on current, when operating at 12v instead of 24v the series current limiting resistor would be 1/2 the value to run at the same current. Find out the value of the series resistor and reduce it by 50% or the current required and calculate the resistance needed.

C co Crusader 2/127 · **Posted:** Fri Jan 25, 2008 1:06 pm

I forgot to mention that they have a reducer built into them anyway. An i asked all 4 of the guys if they were 100% positive and they were positive that they would work(oneof the guy worked with trucklite engineers designing it)

Neal · **Posted:** Fri Jan 25, 2008 1:14 pm

Agree, altho if you run off 12v without cutting the series resistor by 50%, the lites will be 1/2 brightness. This may be bright enough. Try it and see, it will not hurt anything. If they are not as bright enough then just reduce the serries resistor by up to 50% and the LED's will be the max brightness.

C co Crusader 2/127 · **Posted:** Mon Jan 28, 2008 3:18 am

getting the lights on monday. So Im sure its going to take me a while to retro them in to the lib by making a new cradle to hold them and still look somewhat stock. the have ajustment screws right on them so thats all covered. An monday when i go pick them up ill ask then engineers about them again. As far as i can remember though the assured me that there would be absolutly no difference in light quality or intensity from using them on a 12v system. Ill ask what i can do to step up the power or do something with the reducer.

n3qik · **Posted:** Thu Feb 07, 2008 8:34 pm

If this is the one, then you are good to go:
http://www.truck-lite.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&storeId=10001&productId=24203&langId=-1

Any updates???????

tjkj2002 · **Posted:** Thu Feb 07, 2008 8:52 pm

n3qik wrote:

If this is the one, then you are good to go:
http://www.truck-lite.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&storeId=10001&productId=24203&langId=-1

Any updates???????

Those are just the LED turn signal lights,very prone to shorting out due to the bad seals letting water in,weird that the seals allow water in but not to drain out.The regular bulb versions had the same problems.

C co Crusader 2/127 · **Posted:** Fri Feb 08, 2008 1:11 am

no thats not the light im talking about. They use to have it on their website but sometime in the last 2 weeks they took it off. At the moment its only for military use. They had to waive laws on the lights temporarliy; even though they do pass all the ase and dot laws; because the DOD its trying to retrofit all vehicles with 7" lights as soon as possible. Im not sure about other states; but i know wisconsin just requires it to pass ASE regs whuich is where the DOT regs come from. Ill try and take a pic of the ones i got then post them up here.

using 24volt equiptment on a 12v system

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