Main fuse box maintenance

[AV8R]

Old fashioned incandescent bulbs only have the internal impedance of the metal that gives off light as current passes through it and heats up the metal and boils off photons.

Modern LED modules (not standalone LEDS) usually have an internal current and voltage (ie power) limiter circuit. I would not expect them to vary their brightness significantly with power fluctuations. LEDs by nature, are semiconductor junctions which have a threshold voltage for turn on (typically around 0.6vdc). After which, they are pretty linear in I-V characteristics up until their power dissipation limit is reached (which is a function of junction size and cooling). Then they just fail. The high end LED modules have power limiting and pulse duration circuitry to make them behave per the application required. Take a video of your LED lamps or modules and you may see them flickering where the eye alone does not detect this due to ocular persistence

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[Larry Fine]

. . . in my head the Wattage remained constant - so as the voltage increased the current must go down.

This does apply to equipment that is built or modified for a different supply voltage. A 60 watt headlight made for 6 volts requires twice the current as a 60 watt light made for 12 volts.

 

[Larry Fine]

So Mr Fine, you knowledgeable electrical chappie, does this explain why my H4's usually shuffle off this mortal coil on longer rides where higher sustained RPM, let's say 4000 RPM for about 6 hours a day, is held. If I've got this right they are effectively higher wattage at higher volts, i.e. revs. So does this push the bulbs a step too far or not, I had put it down to long periods of sustained vibration and have switched to Osram Ultra Life H4 this year but they haven't received the above treatment yet. I'd love to know your opinion and its good to have you aboard.

No, it doesn't really explain chronic bulb failure, which could be attributed to vibration or over-voltage. The voltage regulator is the only part that could allow too much voltage, and the bulbs should be able to withstand normal vibration.

It might be helpful to monitor the voltage while riding if you can rig it.

To add, I am an electrical contractor, as well as a low-voltage man: audio/video, computer networking, etc. I have been installing car stereo since the days of 8-tracks. I installed an electronic cruise control on my 750 Nighthawk, and plan on it soon on my ST1100.

 

[Jim Van]

Maybe more vibration at the higher RPM's ?? And slightly higher voltage being generated at the higher RPM ??

Bulb lifetime is related to voltage. A little higher voltage will reduce the lifetime drastically. I just read a 1.5 volt increase for a 12 volt ( nominal ) headlamp, will reduce the life by 50%. Sounds about right to me.

BTW, what is the RATED voltage for an H4 lamp, anyway ? I doubt it's 12 volts. 12 volts is only a nominal rating, not the actual rating, I bet, since the charging voltage is always much more than 12 volts. Time to do some research - I will report back later.

EDIT : Found an Osram data sheet. Osram uses 13.2 volts as the "test voltage" for their "Nght Breaker Laser" halogen lamps.

So, I would say a 55 watt head lamp bulb draws about 55 / 13.2 = 4.17 Amps.

Jim V. (MSEE )

 

[AV8R]

Apart from mechanical sources of premature bulb failures, you might also check the electrical health of your bike's battery, generator and ground connection.