Measuring LED headlight draw

[mike123]

I have an amp clamp and I measured 8.52 Amps with the headlights on and 15.8 Amps with the high beams on.

I then swapped in 4 LED headlights and the wiring mod to get all four of them on with low beams selected. I see 10.2 Amps on the amp clamp, whether I have the low or high beams enabled!

Can anyone explain why the amp draw looks the same whether low or high beams on the LEDs are selected?

I am also now second-guessing the wiring modification. I assume I'd be around 5 or 6 amps if I just had the outer lights come on for the normal headlights. Given I've effectively made my current usage worse (though, visibility improvement will I'm sure be awesome), I am curious if the mod is not recommended for that reason.

[iflights]

I have an amp clamp and I measured 8.52 Amps with the headlights on and 15.8 Amps with the high beams on.

I then swapped in 4 LED headlights and the wiring mod to get all four of them on with low beams selected. I see 10.2 Amps on the amp clamp, whether I have the low or high beams enabled!

Can anyone explain why the amp draw looks the same whether low or high beams on the LEDs are selected?

I am also now second-guessing the wiring modification. I assume I'd be around 5 or 6 amps if I just had the outer lights come on for the normal headlights. Given I've effectively made my current usage worse (though, visibility improvement will I'm sure be awesome), I am curious if the mod is not recommended for that reason.

What does the manufacturer of the LEDs say the draw should be?

[mike123]

Hah, good idea. Amazon shows 80 Watts, so at 12.6 volts that is about 6.4 amps for the pair or 12.8 amps for all four of them. I guess that's pretty close to what I observed, with around 2-3 more amps for other lights that were on (doors open, etc).

It looks like there's more energy efficient bulbs available (down to 50 Watts for the same fanless 12,000 Lumens that mine have), so in hindsight I should have made this a part of my shopping criteria I think.

I am still surprised that they draw the same whether in low-beam or high-beam mode though. I was just curious if anyone knew why that was (or if it's likely measurement error on my part).

[DMC-Ron]

Hah, good idea. Amazon shows 80 Watts, so at 12.6 volts that is about 6.4 amps for the pair or 12.8 amps for all four of them. I guess that's pretty close to what I observed, with around 2-3 more amps for other lights that were on (doors open, etc).

It looks like there's more energy efficient bulbs available (down to 50 Watts for the same fanless 12,000 Lumens that mine have), so in hindsight I should have made this a part of my shopping criteria I think.

I am still surprised that they draw the same whether in low-beam or high-beam mode though. I was just curious if anyone knew why that was (or if it's likely measurement error on my part).

Mike,
Your measurement is likely correct. There are differences between different manufacturers on how they handle high/low beam. But one method used involves a slightly offset placement of LED segments. It can be the same number of segments for both high and low beam. The high beam segments are located closer to the base, often about the middle of the bulb, and the low beam segments are often located near the tip of the bulb and may have a shroud shade. Activating the low beam lights the tip LED segments which is further forward from the reflector housing and this, in combination with the built in shade, keeps the beam pattern lower. Activating the high beam lights the more centered LED segments and they are more closely aligned with the focal point of the reflector housing giving the full forward angle of the light. While some manufacturers do use more LED segments for the high beam, it's common for the same type and number of segments to be used for both high and low. This seems the case with your LED bulb. If you look closely at your LED bulb you can usually tell if the quantity and size of the LED segments look to be the same for the high and low location.

Ron

[mike123]

Thanks Ron! I am sure there are good reasons for that setup but it's definitely surprising to me. Good to know the amp clamp is working too, so I can continue to use it for further testing and optimizations. Thanks for the detailed explanation!

[mike123]

I am still annoyed that my LED headlights seem to draw more current than the old bulbs in the car at low beams. (For high beams, the LEDs are much more efficient). I am also a little self-conscious that my "12000 lumen" LEDs are not adjusted well and may be bothering other drivers (particularly with the wiring mod for inner-headlights-on-at-low-beam-setting too). I bought some new bulbs to test out alongside my old bulbs (old ones on the inners, new ones on the outers):

original LEDs: RENO 80W 12000LM 6500K color

new LEDs: LASFIT 40W 4000LM 6000K color

I eyeballed the light output on a white wall, and it was pretty similar with maybe a little edge to the RENO. The color does indeed look more yellow on the LASFIT, which is intended based on the Kelvin number I guess.

I then unplugged one bulb at a time and saw that according to my amp clamp, unplugging one bulb of *either* of the RENO or the LASFIT resulted in a 1.7 amp drop in current usage, implying about 20W per unit for either of them. Is there some sort of electrical reason that testing like this (only unplugging one bulb in the pair, purely to save time) would always produce results like that?

Otherwise all I can conclude is maybe the RENO's are advertised based on 4 bulbs power consumption and the LASFITs are advertised based on 2 bulbs worth of power consumption.

[Helirich]

Mike,
Your measurement is likely correct. There are differences between different manufacturers on how they handle high/low beam. But one method used involves a slightly offset placement of LED segments. It can be the same number of segments for both high and low beam. The high beam segments are located closer to the base, often about the middle of the bulb, and the low beam segments are often located near the tip of the bulb and may have a shroud shade. Activating the low beam lights the tip LED segments which is further forward from the reflector housing and this, in combination with the built in shade, keeps the beam pattern lower. Activating the high beam lights the more centered LED segments and they are more closely aligned with the focal point of the reflector housing giving the full forward angle of the light. While some manufacturers do use more LED segments for the high beam, it's common for the same type and number of segments to be used for both high and low. This seems the case with your LED bulb. If you look closely at your LED bulb you can usually tell if the quantity and size of the LED segments look to be the same for the high and low location.

Ron

If we were talking about one bulb (or pair) handling both high and low beam, this makes sense. But on a car with two pairs I don?t understand how the total draw doesn?t go up with the activation of the second pair. What am I missing?

[Bitsyncmaster]

It is confusing what the advertised power is (one or both bulbs). It's not clear in the adds. Also some units have better electronics (more efficient so less heating of that unit). I found one LED and the electronic unit would run cool. Other units that electronics run hot.

Don't forget these LED headlights use a switching regulator so the higher voltage at the headlight results in less current draw (same power). So make sure your wiring is not dropping the voltage much at the headlight.

[mike123]

Don't forget these LED headlights use a switching regulator so the higher voltage at the headlight results in less current draw (same power). So make sure your wiring is not dropping the voltage much at the headlight.

Did not know that, thanks!