KC Rally 801 bulbs

[VegasF6]

After reading this "Skip the 130w bulbs. Not only is their quality poor and their lifespan ridiculously short, but their very large filament coil has low luminance and does bad things to beam focus. Use 100w bulbs max, and make sure they're from a reputable manufacturer."

It leads me to question if I might actually see some improvement in output or focus in My KC 801 by using a 100W bulb instead? Rather than clutter up C2U5H thread figured it would be better to post a separate one.

Can you clarify, and recommend brands?

Oh, just to be clear they are for strictly off road use only. And while bulb life is sort of a concern, it isn't very much so.

 

[Alaric Darconville]

It leads me to question if I might actually see some improvement in output or focus in My KC 801 by using a 100W bulb instead?

Maybe marginally so in focus, and maybe marginally in filament luminance. I'd expect that a 130W bulb would exacerbate any wiring deficiencies and result in an undervolted filament.

You *could* give up output and get the Osram Night Breaker +90, and could potentially gain filament luminance due to less voltage loss, but if it's truly an off-road application, maybe beam focus would be the least of the problems anyway.

 

[VegasF6]

Can you explain the difference between output vs filament luminance? I would have thought they were the same.

The charging system of the vehicle is more than adequate and the wiring is also over sized and should have no problem with the load. Is there another reason to think there is an under voltage situation?

There are no problems that I am aware of, I am satisfied with the output of the lamps (though it certainly is a narrow beam) but if there is room for improvement I would like to explore those options.

 

[Alaric Darconville]

Can you explain the difference between output vs filament luminance? I would have thought they were the same.

Sort of*. My own apprehension of it is that the light is emitted from a smaller area, approaching a point source, so to get the same output (luminous flux) as a larger light source it must be 'concentrated', so to speak. Compare a fluorescent tube emitting 1800lm compared to a tiny filament emitting 1000lm. Which would you rather stare at?

Additionally, it's easier to look at a 100W filament that's been dimmed down to put out the same luminous flux as a 15W bulb would put out under full power, than it is to look at that 15W filament.

Just an analogy, of course.

The charging system of the vehicle is more than adequate and the wiring is also over sized and should have no problem with the load. Is there another reason to think there is an under voltage situation?

There's only one way to tell-- measure the voltage drop.

*By "sort of", I mean "sort of explain", not "they are sort of the same".

 

[-Virgil-]

Can you explain the difference between output vs filament luminance? I would have thought they were the same

No. Output, measured in lumens or mean spherical candlepower, is the amount of light produced by the bulb, a quantity referred to as "intensity". Luminance, measured in candela per square meter, is (in basic terms) the "brightness" of the light source. Think it over for a moment and it should become clear that you can produce the same amount of light (intensity) with a small brighter source as you can with a large dimmer source. Luminance matters because it translates directly to beam performance. A higher-luminance headlamp light source gives (again in basic terms) more beam "punch" for any given intensity.

Furthermore, a relatively smaller light source improves beam performance versus a relatively larger one because of focus factors; the smaller light source is closer to a point source.

 

[Alaric Darconville]

How close is my own explanation to "getting it"? :)

 

[VegasF6]

I see. And the filament design for my lamp is larger and of poor enough design to cause it to perform worse than for instance the linked 90 watt Osram? This would only be so in the case of voltage drop? Lets assume for the sake of discussion an Osram 90 watt vs a KC 2766, both being fed 13.2V, what sort of luminance figures could I expect for each?

Does KC manufacture there own bulbs, or can you tell me if they use another manufacturer are they a poor bulb?

If I was to do a side by side comparison with one of each lamp in each housing, is it likely I would see a visible improvement in one in either brightness, tint, or beam range? Or are there too many variables to say?

Thanks!
Chris

 

[-Virgil-]

KC does not manufacture any lamps; all of their lights are imported -- mostly from China. There is no 90w Osram H1 bulb. Luminance figures are deep, deep into the arcana of lamp design and are not useful for selecting bulbs in the field. A good quality bulb beats a poor quality bulb for objective beam performance.

 

[VegasF6]

Got it, thanks.
FYI the KC Rally 800 series uses an H3 lamp not an H1.

I installed these lights with short runs of heavy gauge wire directly from the battery fused and relayed. I forget the gauge I used, I think it was probably a #10 but may have been #12. I will check for voltage drop. The lamps are something I probably will not change until one fails then. It would be nice to have spares on hand though.