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H4 LED Headlight bulb

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stormbringer
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H4 LED Headlight bulb

Post by stormbringer on Thu 02 Apr 2015, 1:43 pm

LED headlight is here. Several car- and motorcycle-manufacturers offer LED headlight options for customers to choose.

I want LED headlight too. Promises of 1/3 power consumption, near-infinite 'bulb'-life and loads of light sounds almost too good to be true.

And it is. Too good to be true.

I know. Simply because I've tried one of these 'miraculous' light-machines.

Bottom line: Useless.

Read on for more gritty details, but don't under any circumstance go and buy one of these things (calendar says spring 2015 - maybe things will improve as time passes).


Here's what I've learned.

eBay offers several different motorcycle headlight kits, all containing a device designed to more or less closely mimic the function of a standard H4 bulb. So, I went over the various ads and finally ordered one that looked 'right' (more on this in a later post). This set me back some 18£, and delivery - from China - took the usual month or so. Having picked up the parcel at the post office, this was what I got:



The bulb comes with different adaptor brackets, so I chose the H4 variant

and put it in my utterly standard OE headlight housing. I'm aware there are different housings in use, so here's a picture for reference:


Despite the protruding cooling-fin/fan (yes - there's a small fan inside the radiator!) assembly everything came together fine without anything pinching.

This is what the back plate has to say about light output:


Next was actually testing this for truth value.

And sure there was light. Oodles of it. Loads and loads of the whitest light I've seen in a long time. Absolutely, positively, blinding amounts of whiter-than-halogen light!

So I went for a test ride.
It very quickly became apparent that something was not right. Yes, there was light allright, but it was everywhere - not just a dipped beam as is required not to blind oncoming traffic. The headlight now poured oodles of light everywhere, effectively lighting up the entire scenery in front of the bike. Road signs lit up like christmas trees as far as I could see, which would be a nice thing if only it didn't light up the inside of cars in front of me too.

To record the LED lighting pattern, I found a brick wall and made these two photos:
Dipped beam:


High beam:


Next, I went straight home and replaced the LED assembly with the original Osram Nightbreaker bulb. And returned to the brick wall to do this reference:
Dipped beam:


High beam:


The difference in light distribution pattern is clearly visible, showing the LED device to be incapable of directing light output to go only where desired.

Test failed. Simple as that.

The mechanics of light bulbs and reflectors is key to understanding why this device fails to perform. Current LED light devices simply cannot provide a light source small enough to replace traditional filament based bulbs. I'll try to explain a bit further in another post for those interested, but for now, you can walk away with the knowledge that LED 'upgrade'-bulbs in traditional reflector lamps, designed for Halogen H4 simply doesn't work!
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Beresford
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Re: H4 LED Headlight bulb

Post by Beresford on Thu 02 Apr 2015, 1:56 pm

Pity. I thought that LED bulbs only worked in 4 light arrangements (in cars). 1 pair for main and the other for dipped because , as you say, the light source is too big and "double filament" bulbs are not technically possible anyway.
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stormbringer
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Re: H4 LED Headlight bulb

Post by stormbringer on Thu 02 Apr 2015, 2:39 pm

The principle of our headlight is simple - the silvery headlight bowl closely follows a mathematical shape known a a parabola. Parabolas have what is known as a focal point - meaning that incoming light will gather in this exact point in space, similar to what is shown here:

In the above picture it's worth noting that incoming light rays Q1-Q3 are parallel.

The parabola works just the same the other way around; put a light source at F and all light hitting the parabola will end up being sent in exactly the same direction - parallel rays of light - which is what we want our headlight to do.

One condition applies though; the focal point has a diameter of effectively 0 - zero. Thus, any light source with a diameter bigger than zero will cause non-parallel rays of light to be emitted. Not desirable.

Look at your average H4 bulb. Each filament resembles a rod of length 3 mm or so, one of them being shrouded by a small metal bowl halfway round, allowing only half of the parabola to be lit.

Not point-shaped, but close.

Now look at this LED bulb. It's made from a triangular rod of aluminium (designed to transport heat generated by the LED devices away) onto which yellow COB's (Chip On Board) are glued. Each COB consists of a number of light emitting diodes (LED), meaning our light source now consists of three COBs each consisting of many light sources.


Compared to the filament bulb, this does not even come close to a point-shaped light source. Which is why it doesn't work.

Yes, the manufacturer has done his best to put the COBs near the place where filaments are positioned in a traditional H4 bulb, but technology simply doesn't allow him to put the LEDs close enough to mimic the filament's behaviour.

This has to do with heat. Halogen bulb filaments thrive on heat, LEDs don't. Cramping LEDs together causes heat buildup, which causes them to deteriorate rapidly.

So, what I got in the mail from China simply represents the current state of technology 2015. Once the heat dissipation issue is solved, LEDs may either be cramped together closely enough - or perhaps replaced by the holy grail of lighting; ONE led - to make a properly functioning Halogen H4 replacement 'bulb'.


Last edited by stormbringer on Thu 02 Apr 2015, 3:03 pm; edited 1 time in total
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stormbringer
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Re: H4 LED Headlight bulb

Post by stormbringer on Thu 02 Apr 2015, 2:55 pm

@Beresford wrote:Pity. I thought that LED bulbs only worked in 4 light arrangements (in cars). 1 pair for main and the other for dipped because , as you say, the light source is too big and "double filament" bulbs are not technically possible anyway.
You're spot on. Actually, the H4 is in itself a Frankenstein's monster - simply because it has two filaments each requiring a separate focal point. One single parabola cannot do this...

Manufacturers have resorted to dual-light arrangements to improve on the matter. One parabola - holding eg. a H7 single-filament-bulb - for high beam and another parabola with another geometry and a H7 to go with it for dipped beam.

But all this was last year. Now, we have Xenon which is rapidly being replaced by dedicated LED arrangements, far superior in performance to the oldskool H4 solutions.

The thing is, it's entirely possible to use LED light sources for headlight use. But the 'parabola' - nowadays a clever lens arrangement - must be made specifically for LED use.

Thus, if we want to put LEDs on our CBs, the entire headlight assembly has to be replaced by something new. Has anyone seen any complete replacement assemblies?
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Beresford
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Re: H4 LED Headlight bulb

Post by Beresford on Thu 02 Apr 2015, 3:54 pm

American market
http://www.gelighting.com/LightingWeb/na/consumer/products/highlights/nighthawk/led-headlights/overview/
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HomeBrew
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Re: H4 LED Headlight bulb

Post by HomeBrew on Thu 02 Apr 2015, 4:03 pm

@stormbringer wrote:
And sure there was light. Oodles of it. Loads and loads of the whitest light I've seen in a long time. Absolutely, positively, blinding amounts of whiter-than-halogen light!

So I went for a test ride.
It very quickly became apparent that something was not right. Yes, there was light allright, but it was everywhere - not just a dipped beam as is required not to blind oncoming traffic. The headlight now poured oodles of light everywhere, effectively lighting up the entire scenery in front of the bike. Road signs lit up like christmas trees as far as I could see, which would be a nice thing if only it didn't light up the inside of cars in front of me too.







Maybe blinding car drivers is a small price to pay for having a decent view around bends in the dark? In general they don't seem too concerned about dipping their beams when I meet them, they can see I am coming but often blind me for a few seconds anyway- no real reason for this other than they are lazy and don't give a ****.
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ashcroc
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Re: H4 LED Headlight bulb

Post by ashcroc on Thu 02 Apr 2015, 6:04 pm

Interesting reading. I wonder if you'd get better results from a clear lense/ angled relector arrangement like jerryfudd's new headlight has.
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stormbringer
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Re: H4 LED Headlight bulb

Post by stormbringer on Thu 02 Apr 2015, 6:23 pm

@ashcroc wrote:Interesting reading. I wonder if you'd get better results from a clear lense/ angled relector arrangement like jerryfudd's new headlight has.
Unlikely. The lamp geometry is the same, thus likely to produce the same result. A much better way to go would be to replace the entire unit with something akin Beresford's suggestion. The GE unit seems to me to be a better option. Wonder if it fits the OE housing?
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stormbringer
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Re: H4 LED Headlight bulb

Post by stormbringer on Thu 02 Apr 2015, 6:28 pm

@HomeBrew wrote:Maybe blinding car drivers is a small price to pay for having a decent view around bends in the dark?
That, and being pulled over by the first oncoming patrol car you meet. The light colour (as well as sheer amount) is all-revealing...
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sullivj
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Re: H4 LED Headlight bulb

Post by sullivj on Fri 03 Apr 2015, 7:51 am

Great write up SB. I would be concerned about the possible heat generated so close to my wiring loom too.

If there was a way of getting that light AND defining a pattern, I would love to get one.
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Beresford
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Re: H4 LED Headlight bulb

Post by Beresford on Fri 03 Apr 2015, 2:08 pm

This article is a good review of the various headlight system types.
http://www.autoevolution.com/news/battle-of-the-headlights-halogen-vs-xenon-vs-led-26530.html
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skyrider
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Re: H4 LED Headlight bulb

Post by skyrider on Mon 04 May 2015, 7:13 pm

it would worry me when I read from CHINA on the packet will you be able to send it back for a refund Neutral
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Basil Moss
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Re: H4 LED Headlight bulb

Post by Basil Moss on Tue 05 May 2015, 7:21 pm

@HomeBrew wrote:
Maybe blinding car drivers is a small price to pay for having a decent view around bends in the dark? In general they don't seem too concerned about dipping their beams when I meet them, they can see I am coming but often blind me for a few seconds anyway- no real reason for this other than they are lazy and don't give a ****.

I'd rather the people driving cars toward me weren't blind...

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