LED's

[robert shreveport]

Had a guy ask me today, if LED's were on a 6 volt A and on another A that is 12 volt would there be any difference in the brightness? I told him I thought there would be no difference. What is the answer?

[Mike V. Florida]

NO, they are not like light bulbs.

The actual LED's need a voltage below either battery voltage, the actual voltage depends on several things not need for your answer. There is circuitry, in most cases, to bring down the voltage to a level that the LEDs need to light.

So if you have LED lights that are designed for 12 volts and place them on a 6 volt car they might not even light due to the circuitry and if they did there would be little difference. LED's dim by turning them on and off, the longer they are on the brighter your eyes see them.

[Tom Wesenberg]

I bought a pair of 12 volt LED trailer lights from Harbor Freight and they light on 6 volts but are dimmer.

[Mike V. Florida]

Originally Posted by Tom Wesenberg

I bought a pair of 12 volt LED trailer lights from Harbor Freight and they light on 6 volts but are dimmer.

Why do you think that was? Maybe they were wired in a combination of series and Parallel to get away from using a regulator?

[Tom Wesenberg]

Originally Posted by Mike V. Florida

Why do you think that was? Maybe they were wired in a combination of series and Parallel to get away from using a regulator?

I'm sure these are similar to those free H/F flashlights with cheap batteries that quickly dim as the batteries wear out. With just a resistence circuit to control the amperage, instead of a more advanced regulated power supply, they dim as the voltage drops.

I bought some 4.5 volt led's off the internet, and I can connect 1, 2 or 3 AA cells and with one connected you can barely see a dim glow. With 2 connected, it's a low light, and with 3 it's a bright light.

[Mike V. Florida]

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Originally Posted by Tom Wesenberg

I'm sure these are similar to those free H/F flashlights with cheap batteries that quickly dim as the batteries wear out. With just a resistence circuit to control the amperage, instead of a more advanced regulated power supply, they dim as the voltage drops.

I bought some 4.5 volt led's off the internet, and I can connect 1, 2 or 3 AA cells and with one connected you can barely see a dim glow. With 2 connected, it's a low light, and with 3 it's a bright light.

Makes sense.

[Tom Wesenberg]

BTW, those free H/F flashlights aren't too bad IF you throw away the cheap batteries as soon as they start to dim, or 2 months, which ever comes first, and also put a dab of grease on all the contacts for the batteries. Leaky cheap batteries are the killer for these free flashlights.

[Mike V. Florida]

Originally Posted by Tom Wesenberg

BTW, those free H/F flashlights aren't too bad IF you throw away the cheap batteries as soon as they start to dim, or 2 months, which ever comes first, and also put a dab of grease on all the contacts for the batteries. Leaky cheap batteries are the killer for these free flashlights.

I use them at work and do exactly what you said. I toss the batteries right away and don't wait until they die down.

[robert shreveport]

Mike V. and Tom I'm not sure you understood me as I meant to ask my question. Can't you buy 6 volt LEDs and 12 volt LEDs and use them in the respective cars of the same voltage. I think what you both said was the 6 volt would be dimmer. I don't know electronics, in my mind I would have thought they would both appear similar in brightness.

[SteveB31]

We have both in stock, so i will try them on 6 volt and 12 volt batteries tomorrow and answer your question.

[Tom Wesenberg]

OK, now I see what you mean. Yes, they should be the same but it would also depend on the particular LED. I have a single LED table lamp that is brighter than my 9 LED flashlight.

I'd wait for Steve's answer tomorrow, because I'd assume his LED's are made by the same company and designed to emit the same light.

[robert shreveport]

I'll be awaiting the results, thanks. To me it was a good question, because I think some guys would be thinking about this if they were considering the swap from 6-12 volts.

[SteveB31]

I tried the 12 volt United Pacific tail light LED on 6 volt, and their is NO LIGHT.

Other LED's may differ but these will not work at all on 6 volts.

Also, keep in mind that the United PAcific LED tail light conversions, are polarity specific. the 6 volt ones are positive ground and the 12 volt ones are negative ground, and yes, I did try them both ways as I was curious.

Steve Becker
Berts Model A Center

[SkipShift]

Here are some 6V Led's. There are a few others at this site. I haven't tried them. http://www.ledlight.com/24-led-light...-sensitve.aspx

[bogiediver]

LEDs can be voltage and polarity specific - or not... depends on how they were made - i.e. what circuitry is included.

For example - there are LED 7" round headlights that are neg ground only and put out full light from 9V to 33V - simply don't work below or above.

A 4" round aux lamp works 9v to 15v - w auto shut off at 18v...

Marker lamps designed for 13.4v (in other words the typical 12v system) only.

All these from the same company...

Some single intensity LEDs can be 'dimmed' with an inline resistor; or with the proper wiring including a resistor in one leg and a diode in the other, can become dual intensity.

I use all the above on my motorcycle (12v neg gnd)...

Most LEDs are polarity specific (and protected), but not all - so you have to be sure to get what you need.

Unfortunately, the correct answer to the true original question (whether the brightness would vary for the same LED on 6v vs 12v) is - it depends on the manufacture of the LED device.

I use a set of 6v pos gnd, tear drop shape, dual intensity, LED clusters mounted to the rear bumpers of my roadster to give me running, turn and brake lights - I feel safer with those in place...

FWIW