04-21-2017, 11:15 AM
I'm not sure that there is necessarily less power consumption. LED headlights often have huge heat sinks to dissipate the power caused by the series voltage-dropping resistance needed, because an LED will short-circuit if connected directly to battery voltage.
The voltage drop across an LED (light emitting diode) can range anywhere from 0.7V to around 1.5V I believe. The amount of light is more or less proportional to the current passing through the LED and its efficiency. Nevertheless, if the LED is drawing current at 1.5V for example, that same current is flowing through the series resistance that is dropping 12.3 to 12.5V (assuming 13.8 to 14.1V operating system voltage). Power = voltage * current so it's easy to see that the power wasted in the series resistance is far greater than the power converted into photons by the LED array. Some LED headlight modules not only incorporate massive metal heatsinks...many also include an actual electric fan to blow air over the heatsink for additional heat dissipation to the ambient air.
Now, maybe in an LED headlight array the diodes are connected in series and not in parallel. In that case, the wasted power would be much less. If there were four 1.5V LEDs in series for example, then the total drop across them would be 6V and the series resistance would only have to dissipate the wasted power from dropping 7.8 to 8.1V.
I think the main benefit of an LED headlight is much greater brightness, with the secondary benefit being virtually infinite life expectancy. No more having a headlamp burn out while out on a ride. A tertiary benefit might be that the bright white quality of the light is more effective than the dull yellow glow of an incandescent lamp.
The voltage drop across an LED (light emitting diode) can range anywhere from 0.7V to around 1.5V I believe. The amount of light is more or less proportional to the current passing through the LED and its efficiency. Nevertheless, if the LED is drawing current at 1.5V for example, that same current is flowing through the series resistance that is dropping 12.3 to 12.5V (assuming 13.8 to 14.1V operating system voltage). Power = voltage * current so it's easy to see that the power wasted in the series resistance is far greater than the power converted into photons by the LED array. Some LED headlight modules not only incorporate massive metal heatsinks...many also include an actual electric fan to blow air over the heatsink for additional heat dissipation to the ambient air.
Now, maybe in an LED headlight array the diodes are connected in series and not in parallel. In that case, the wasted power would be much less. If there were four 1.5V LEDs in series for example, then the total drop across them would be 6V and the series resistance would only have to dissipate the wasted power from dropping 7.8 to 8.1V.
I think the main benefit of an LED headlight is much greater brightness, with the secondary benefit being virtually infinite life expectancy. No more having a headlamp burn out while out on a ride. A tertiary benefit might be that the bright white quality of the light is more effective than the dull yellow glow of an incandescent lamp.