Bulb "run in" ? I have some Data but need explanation pls

[Morepower!]

I noticed a while ago that I was getting different voltage and current readings between new and used bulbs while doing some testing, I just forgot to write it down. So today I re-measured them, and wrote them down this time, below is what I got.

Bulb with 65+hrs use
93.6V @ 0.64A
13,500 Lux

New bulb
81.4V @ 0.72A
17,200 Lux

NOTE: The Lux readings were taken at a distance of 175mm from the bare bulb.

The bulbs are from the same Manufacturer, the only difference is one was H4 config. and the other was H7. I can't see this making any difference though. It's interesting to note when you do the math the Wattage is very similar. IIRC you need more voltage to transverse a bigger gap rather than current. Please correct me if I am wrong. But I really would like to know what you guys think of this. Is this what is classed as "run in" ??

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[XeRay]

As the bulb ages and the arc gap gets wider the voltage will go up and the current should reduce to maintain the same wattage over the bulbs life. Eventually the gap will be too large for the max starting voltage of the ballast. Hot restrike takes the highest voltage so that is where the problem should become most evident first.

Well aged bulb (worn out) "steady state" voltage should max out between 105 and 110 volts (wattage from a quality ballast will stay the same over the bulbs life) This 105-110V is the intended end of life desired by Philips, Osram and GE.

 

[BVH]

More excellent HID facts from Dan! Thank you!

 

[Patriot]

Awesome info as usual Dan. :thumbsup:

The longer I'm here, the more I learn.

 

[Morepower!]

Yes thanks for the explanation Dan. I've added some Lux readings I took after re-performing the test. I checked the gap between the electrodes with the eyeometer and the older bulb definately has a larger gap, my guess is 0.5-1mm. The eyeometer could be out though as it probably needs recalibrating after 43yrs. Would those Lux readings be typical of what could be expected considering the power readings for each bulb ? Meaning that the new bulb should be brighter ? The way I took the Lux readings wasn't exactly perfect, however the newer bulb definately seemed brighter to me.

 

[XeRay]

Yes lumens do decrease with age. Asian bulbs loose output much more quickly than Philips, Osram or GE bulbs.

Newest versions from these sources of high quality bulbs produce about 85% lumens of new at 1000 hours.