Are your headlights or work lights duller than they should be?

Here are some interesting facts about voltage loss to your lights.

If we use for an example a 12 volt 55 watt halogen globe such as a low beam or work light globe, the manufacturer has usually rated the globes wattage (55 in this case) at 12.8 volts, so we have 55 watts at 12.8 volt.

The wattage of a globe is only a representation of brightness. Wattage is a measurement of all energy produced by the globe, and a very big portion of it is heat.

Voltage loss to a light is determined by measuring the voltage at the globe, while it is plugged in and operating. It is common in older machines to find less than 10.5 volts actually at the globe. This equates to only 37 watts of power output. If however we could get our full charging voltage of 14 volts to the light then we would have 66 watts.

  • 55w @ 12.8v
  • 37w @ 10.5 v  (Bad)
  • 66w @ 14v (Good)


Voltage loss can be reduced by

  1. Decreasing current draw, or power output of the lights by using LED technology where most of the energy produced is actually light. However it is worth noting that even the LEDs may not be at full brightness because there will still be some voltage loss.
  2. Rewiring existing halogen lights through relays with a direct power supply from the battery to achieve 14 volts at the light.
  3. Rewiring lights with relays and/or heavier cable and replacing with LED or HID technology. (a+b)

Alignment is important too, many complaints about dull lights may be fixed by simply getting them to shine in the right place!

Are your lights dull?