LED driving lights are all the rage right now, for a number of good reasons. The high initial cost is usually outweighed by their incredibly long life (typically 20 times that of an HID bulb), intense light-producing ability, and low power draw. If lumens are the standard measure of light put out by a lamp, and Watts a measure of power draw, then a tungsten bulb would produce 12-17 lumens per Watt, a halogen bulb 24lm/W, a fluorescent lamp 45-75lm/W and an LED lamp up to 90lm/W.
So LEDS – light-emitting diodes – are efficient, and that means less power drawn from your battery. Also, as manufacturers get better at building reflectors and lenses to better focus the light produced by individual LEDs, they have been able to extend their use from floodlights (in the main) to driving lights. As with all lamps, heat is the enemy of LEDs, too: excessive heat build-up will destroy the diode, reducing its lumen output over time – hence the need for cleverly designed, often rather heavy, metal heat-sink-type housings. Add to this the vibration associated with driving off-road, and the problems of regular doses of dust, stray stones and immersion in water, and it’s clear that we ask a lot of a driving light.
A typical standard headlight puts out 1800-2000 lumens. When driving offroad, especially in unfamiliar territory, you often want more light, spread wider and further. The law allows a maximum of three lights on each side of the car, with auxiliary lights to be mounted below the headlights for on-road driving to prevent blinding oncoming road users. No legal ceiling is placed on total lumen output, but one should know that lights mounted on the roofrack, for example, though giving a longer light throw, may be used only off public roads, must be covered at all other times, and must be operated on a separate electrical circuit.
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