I'm sure this has been discussed a million times, but I'm trying to put some cheap chinese 12v led lights as replacement marker lights in a 24v vehicle. These are super cheap, talking about like $80 for all 16 lights, compared to something like $40/light for name brand.

it's confusing because some of the auction listings say they are 12/24v. nothing on the box at all, and sticker on light back says 12v.

I would love to just put in series but that looks to be harder than its worth, they have 2 positive wires, one which does the 6 leds( x2) on the left and right side and one which does the center 6 leds, so that wouldn't be properly balanced. and a shared ground

How bad do you think it would be just to run them at the full 24v? honestly if it just reduces their lifespan by a reasonable percentage i could care less for the price and expected use. i just don't want them to say like catch on fire.

 

You need to state your location. All exterior lights on motor vehicles in my country need to be approved by the Department Of Transportation.

 

In the US, but I don't see why these wouldn't work since I'm modifying the existing OKI lights and using the original DOT plastic lenses

 

Still not legal. The color of the markers and the brightness of the lights are regulated.

 

Still not legal. The color of the markers and the brightness of the lights are regulated.

Got a link to the law or state laws which apply because I have seen motorcycles all dressed out with LED lights including modifying brake lights to flash X number of times when brakes are applied. I would be curious as to exactly what the law or code states.

Ron

 

I've had some experience with DOT regs and as far as I can find I don't see how this is illegal. I was asking for technical advice, not legal, though I can understand some people's hesitation to provide advice if they may somehow feel is against the law.

https://www.gpo.gov/fdsys/pkg/CFR-2004-title49-vol5/xml/CFR-2004-title49-vol5-sec571-108.xml

The lenses must be DOT approved but I see nothing that indicates the lights themselves have to be. I see minimum candela limits, and maximum on headlights, but no maximum on clearance/marker lights.

 

Viewing them as simply LEDs if you can get the current at 12 volts a series resistor can be placed in series with each yellow wire to limit the current when running at 24 Volts. This of course assumes any local, federal or state laws are complied with.

Ron

 

I was hoping to avoid a resistor wasting energy/heat but i guess that's the only real option with this design since I don't see how to put the two halfs in series. Any idea on what the amp pull is on a light like this, or what size resistor i should use?

 

Actually did a little more digging on these regs from 1972, maximum marker light allowance is 15 cd

a The maximum light output for red clearance and identification lamps is 15 cd. When red
clearance lamps are optically combined with stop or turn signal lamps, this maximum applies on
or above the horizontal.
J592e, July 1972.

which sounds to me like it would be pretty hard to surpass based on wikipedia

The luminous intensity of light-emitting diodes is measured in millicandelas (mcd), or thousandths of a candela. Indicator LEDs are typically in the 50 mcd range; "ultra-bright" LEDs can reach 15,000 mcd (15 cd), or higher.

 

Your best bet would be to run a set with both yellow tied together on a bench at about 13.6 volts or off a fully charged 12 volt battery if you can't come up with 13.6 volts. Place a current measuring meter in series and note the current. With that known and knowing the actual voltage of a 24 volt system we can calculate the needed resistance and wattage needed. I must admit I have no clue what a 24 volt system running voltage actually is. Maybe another member does know.

Ron

 

so i dug out my small bench ps and tried it at 24v (i think reality is upto 28v) and it started smoking about less than a minute, so definitely not designed for 24v, only 12v

i'm getting around a .24 amp draw, will do a resistor calc in a little and order, so this is not getting done tonight or tomorrow for that matter

 

i'm getting around a .24 amp draw, will do a resistor calc in a little and order, so this is not getting done tonight or tomorrow for that matter

If at around 12 to12.6 or Even 13,6 and you drew 0.24 Amp for a section. WE can wing it and call 24 you want about a 50 Ohm resistor give or take a few ohms and rated at about 1 watt should be adequate.

Ron