michael hurd
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In the United States and Canada, ( DOT ) nominal headlight voltage is specified at 12.8 volts.
In Europe ( ECE ) they rate headlights at 13.2 volts.
Both DOT and ECE lifespan ratings are specified at 14 volts.
Bulb life varies exponentially with changes in voltage, to the -13th power.
Bulb output (lumens) varies exponentially with change in voltage, to the +3.4 power. It's tempting to say the life curve is so much steeper than the output curve that it's worth lowering the voltage to get long lifespan, but it's really not. If you look at the data for how much more likely you are to be in a visibility-related crash after dark than in daylight, you will quickly decide that output is much more important than lifespan.
Old bulbs can suffer degradation from many forms. In a system where the DRL's use headlight bulbs, and the applied voltage is lower, the bulbs can accumulate black deposits from the vaporized tungsten that does not re-attach itself to the filament.
The physical positioning of a filament can change over time, the filament undergoes loss, and in a halogen environment if the voltage is high enough, the vaporized tungsten gets re-deposited on the red hot filament, but not necessarily in the place where it left. The resulting geometric change in shape will de-focus the headlamp filament.
" I just bought '80' watt low beams to replace my 55 watt ones. "
Wattage without any other specification is useless. 5 mpg sounds like a terrible fuel mileage, but if you are driving a tractor-trailer unit grossing 140,000 pounds, that's not bad.
What's a watt? A watt would be 1 volt applied across a resistance of 1 ohm, and a resultant 1 ampere of current flow.
Many calculators are available online to show you the relationship between voltage, resistance and current.
Those 80 watt low beams might be 80 watts at 14+ volts, but may be 40ish watts at 11 volts.
" My headlights suck, can't I just install an HID kit? " If you intend to use the factory installed housings, no.
While you can certainly install certain stand alone HID projector units from Hella, and others ( flange mount ) that are weather sealed and certified to maintain compliance with laws, installing a projector assembly from another vehicle, or a custom one behind the original optical lens will result in a non-compliant assembly.
" I just installed these [ insert brand here ] LED drop in's, and I can see much better! " There is no legally compliant drop in LED headlight system, period. Nor will there be for a reflector housing designed for halogen light sources. Irregular radiation pattern, and excessive glare for oncoming traffic are just part of the problem.
" What is the difference between LL bulbs and regular bulbs? "
Long life bulbs may last a long, long time. They also produce LOWER output than a regular bulb. Do you want to see, or not?
" Can I install relays for the headlights? "
Yes, you should if being able to see is your number one priority. In some vehicles, the headlights are fed by as small as 20 gauge ( SAE sizes are smaller than AWG sizes ! ) wire. This is woefully inadequate, leading to horrific voltage drop and dismal output.
" Can I measure my voltage drop? "
Absolutely, with a volt / ohm meter. The correct way to do this is with the bulbs lit up and functioning. This requires backprobing the headlight connections, in some vehicles this is not easy. A couple of paper clips straightened out and inserted next to the wire in the silicone seal of a weatherpack connector can work, although there are specialty tools for this as well. Measure for both the battery positive and the ground voltage drop, adding these together is your total voltage drop.
Set your meter to measure resistance, take the red lead and place it on the battery +, then take the black lead and place it on the backprobe device. Write down the value. Repeat for the battery - to the headlight negative lead, this time placing the red lead on the headlight backprobe device.
Add the two together, and this is your total loss in the headlight system.
" My headlamps are hazy / yellow, will better bulbs help? "
A very small amount. If you are on an absolutely beer budget, cleaning and or polishing your headlamps along with good quality relays is your number 1 and 2 items to address.
Look at it this way... if someone smeared Vaseline on your television screen, would turning up the color temperature compensate for the picture distortion? NOPE.
The lenses are part and parcel of the OPTICS of the headlight, a complete system.
" These bulbs have a blue coating on them, and I can see better! "
Selective filtering ( like the Sylvania Silver Star ) reduces the total amount of light reaching the road. By applying a blue filter, you reduce the amount of light. You cannot filter a light source to remove some band of light, and wind up with MORE light, period.
It is an optical illusion.
In Europe ( ECE ) they rate headlights at 13.2 volts.
Both DOT and ECE lifespan ratings are specified at 14 volts.
Bulb life varies exponentially with changes in voltage, to the -13th power.
Bulb output (lumens) varies exponentially with change in voltage, to the +3.4 power. It's tempting to say the life curve is so much steeper than the output curve that it's worth lowering the voltage to get long lifespan, but it's really not. If you look at the data for how much more likely you are to be in a visibility-related crash after dark than in daylight, you will quickly decide that output is much more important than lifespan.
Old bulbs can suffer degradation from many forms. In a system where the DRL's use headlight bulbs, and the applied voltage is lower, the bulbs can accumulate black deposits from the vaporized tungsten that does not re-attach itself to the filament.
The physical positioning of a filament can change over time, the filament undergoes loss, and in a halogen environment if the voltage is high enough, the vaporized tungsten gets re-deposited on the red hot filament, but not necessarily in the place where it left. The resulting geometric change in shape will de-focus the headlamp filament.
" I just bought '80' watt low beams to replace my 55 watt ones. "
Wattage without any other specification is useless. 5 mpg sounds like a terrible fuel mileage, but if you are driving a tractor-trailer unit grossing 140,000 pounds, that's not bad.
What's a watt? A watt would be 1 volt applied across a resistance of 1 ohm, and a resultant 1 ampere of current flow.
Many calculators are available online to show you the relationship between voltage, resistance and current.
Those 80 watt low beams might be 80 watts at 14+ volts, but may be 40ish watts at 11 volts.
" My headlights suck, can't I just install an HID kit? " If you intend to use the factory installed housings, no.
While you can certainly install certain stand alone HID projector units from Hella, and others ( flange mount ) that are weather sealed and certified to maintain compliance with laws, installing a projector assembly from another vehicle, or a custom one behind the original optical lens will result in a non-compliant assembly.
" I just installed these [ insert brand here ] LED drop in's, and I can see much better! " There is no legally compliant drop in LED headlight system, period. Nor will there be for a reflector housing designed for halogen light sources. Irregular radiation pattern, and excessive glare for oncoming traffic are just part of the problem.
" What is the difference between LL bulbs and regular bulbs? "
Long life bulbs may last a long, long time. They also produce LOWER output than a regular bulb. Do you want to see, or not?
" Can I install relays for the headlights? "
Yes, you should if being able to see is your number one priority. In some vehicles, the headlights are fed by as small as 20 gauge ( SAE sizes are smaller than AWG sizes ! ) wire. This is woefully inadequate, leading to horrific voltage drop and dismal output.
" Can I measure my voltage drop? "
Absolutely, with a volt / ohm meter. The correct way to do this is with the bulbs lit up and functioning. This requires backprobing the headlight connections, in some vehicles this is not easy. A couple of paper clips straightened out and inserted next to the wire in the silicone seal of a weatherpack connector can work, although there are specialty tools for this as well. Measure for both the battery positive and the ground voltage drop, adding these together is your total voltage drop.
Set your meter to measure resistance, take the red lead and place it on the battery +, then take the black lead and place it on the backprobe device. Write down the value. Repeat for the battery - to the headlight negative lead, this time placing the red lead on the headlight backprobe device.
Add the two together, and this is your total loss in the headlight system.
" My headlamps are hazy / yellow, will better bulbs help? "
A very small amount. If you are on an absolutely beer budget, cleaning and or polishing your headlamps along with good quality relays is your number 1 and 2 items to address.
Look at it this way... if someone smeared Vaseline on your television screen, would turning up the color temperature compensate for the picture distortion? NOPE.
The lenses are part and parcel of the OPTICS of the headlight, a complete system.
" These bulbs have a blue coating on them, and I can see better! "
Selective filtering ( like the Sylvania Silver Star ) reduces the total amount of light reaching the road. By applying a blue filter, you reduce the amount of light. You cannot filter a light source to remove some band of light, and wind up with MORE light, period.
It is an optical illusion.
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