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ELECTRICS

HALOGEN OR HID OR LED DRIVING LIGHTS

The black art of lighting up bush roads

We all know that auxiliary lights are necessary for safe night driving on bush roads, but do you need to spend up on HID or LED lights, or are halogens good enough?

intro picThe black art of lighting up bush roads has produced a dazzling array of add-on equipment, which makes selecting a pair of night-vision aids quite a business.

The reason for buying after-market lights should be to enhance standard 4WD headlight penetration, which is inadequate for driving on Australian country roads. However, as happens also with the purchase of wheels or tyres, appearance often influences the buyer, rather than performance.

Our laboratory and real-world light tests over the years have shown that price isn’t a reliable guide to light performance, because many of the most expensive lights on the market have performed ordinarily, while some of the cheaper ones blazed brilliantly.

Looking at a light will tell you if it seems to be well made and if its mounting bracket is substantial, but it won't tell you much about its performance.

The most confident light makers have supporting literature that shows approximate light patterns on the road surface and pattern distances in metres. However, even such diagrams can be ‘fiddled’ because light intensity is very difficult to quantify.

By far the most popular auxiliary lighting choice of 4WD owners is a pair of round spotties, but there’s not much point settling on a pair and then discovering they won’t fit your bar. Vehicle registration authorities in some States are policing light fitments that project beyond the front profile of the vehicle or the ‘roo bar.

The aim of this is to ensure that there are no sharp projections that could harm pedestrians in a collision, so if you want to stay within the letter of the law and be a good 4WD citizen, you should ensure that your new lights fit within the bar profile. The top of a light may project, provided it can bend back freely within the bar profile in the event of a pedestrian impact.

Another fitment factor is the need to adjust and tighten lights when they’re in position on your bar. Make sure you’re going to be able to access the adjustment nuts or screws once the light is in place.

Bearing in mind that most State and Territory rules now insist that spotties tuck inside the ‘roo bar envelope, most buyers finish up with a pair of round lights with diameters from 150mm up to 230mm. 

Most light makers recommend a pair that combines a pencil or ‘spot’ beam light for maximum distance illumination and a spread beam, to light up the road edges.

Another arrangement preferred by some is a pair of pencil beams and yet another combination is a pair of spreads.

Recently, LED light bars have become popular and are much easier to fit to streamlined vehicle fronts. However, our testing shows that LEDs can't produce the one-kilometre-distance illumination that big halogens and HID lights can.

However, LEDs have good mid-distance illumination and are virtually maintenance-free.

 

What is a ‘Halogen’ Light

In any incandescent bulb, electricity passing through a thin filament causes it to glow: the higher the temperature, the brighter the bulb. However, during the process, atoms of the wire fly off, so that the wire decays to the point where it burns through or breaks. 

In a conventional bulb, as used in most parking and taillight globes, the atoms deposit on the inside of the glass, eventually clouding the bulb and reducing its output.

The great advance of the halogen bulb is the fact that it’s pressure-filled with an inert halogen gas that greatly reduces the amount of ‘evaporation’ from the filament. In addition, the gas forms a tungsten halide compound with the few atoms that do break away from the filament. This halide returns to the filament, breaking down to its original components of tungsten and halogen gas, thus improving the life of the bulb and eliminating clouding. That said, the halogen’s ‘hot wire’ process is still only five percent efficient, with 95 percent of the electrical input being shed as heat.

The halogen bulb will wear out, through the effects of filament degradation, vibration and the extreme heat of the bulb: around 400 degrees C. Rough roads, poorly installed lights and clear plastic light covers used at low speeds, where there’s insufficient cooling airflow, all contribute to shortening of bulb life. In bush-travel conditions, a halogen 55W bulb may last for only 200 working hours, but a 100W bulb for as little as 50 hours.

 

What Watts

hella halogensIf vehicle lights were similar to household lights wattage would be the main indicator of brightness, but vehicle lights differ in a very significant way from house lights. When you buy a new globe for your house, you don't expect it to be ‘directional’, unless you’re buying outside spotlights or indoor ‘down’ lights.

Vehicle lights need to be directional, in a precise way, and that's where the science comes in.

This directional component comes from the reflector finish and shape and, in the case of most spread beams, from the lens fitted to the front of the light.

A pencil beam usually relies solely on reflector shape and finish for beam direction, and has a plain lens.

Spread-beam lights used to rely totally on shaping of the lens - fluting or bars moulded into the glass - to bend the light from the reflector into a shorter, but wider shape. However, there’s an increasing trend to use free-form reflectors to shape the beam spread, through a clear lens.

Free-form headlights are now the standard offerings in most new 4WD vehicles. Fashion dictates that modern headlights have clear lenses, so the reflector has to do all the beam shaping.

That technology has now moved from headlights into spotties.

 

Lab Testing

narva labAt Outback Travel Australia we've checked out different lights in real-world conditions and we've also used a light laboratory to measure actual performance.

This lab has a light stand at one end, a white wall at the opposite end and in between, the floor, ceiling and walls are covered with dark, non-reflective surfaces. The height and width of the white wall represent the common limits of long-distance and spread-beam lighting.

For a power supply we use a new battery, connected to an electronically controlled charger that delivers a constant 13.8 volts. We settled on this charging level, because it’s typical of vehicle charging system voltages. A new battery has an open circuit voltage of 13.2 volts and the charging circuit voltage must exceed that for current flow.

The lights are connected to the battery, using the light manufacturer’s loom where provided and we check battery voltage before each test.

From our experience with measuring laboratory light patterns and relating those patterns to real-world conditions we know that the best pencil beam lights have a large ‘hot spot’ in the centre of the combined-light beam, with little diffusion into the bands of lesser intensity.

The best spread-beams show flattish concentrations of light around a shallow-oval centre, fanning out to at least 10 degrees either side of centre.

Less effective pencil beams have a wider diffusion of light, with a smaller central hot spot, while some wide-spreads spray light over a very wide angle, losing intensity in the process.

 

HID Lights

hella compact hidHigh Intensity Discharge lights are the brightest stars in the 4WD lighting galaxy. We know that LED (light emitting diode) driving lights are the newest techno developments, but the best long-distance-beam choice in the 4WD lighting arena is the gas discharge type.

These HID (high intensity discharge) lights are automotive equivalents of the household fluorescent tube, which is 20 percent efficient and almost everlasting. In contrast, the best halogen globes are around five percent efficient; with most of the electrical input being dissipated as heat.

HID lighting technology replaces the filament of the light bulb with a capsule of gas. The light emanates from an arc discharge between two closely spaced electrodes that are hermetically sealed inside a small quartz glass capsule.

(For the atomically literate, light is produced by passing a current through a metal vapour. Free electrons colliding with an atom in the vapour momentarily knock an electron into a higher orbit of the atom. When the displaced electron falls back to its former level, a quantum of radiation is emitted. The wavelength of radiation depends on the energy zone of the disturbed electron and on the type of metal vapour used in the arc tube.)

To operate, HID lights require high-voltage ballast units that supply and maintain high voltage and control the current. All first-generation HID lights had externally-mounted ballast units – usually finned aluminium boxes – but new-generation HIDs have internally-fitted ballast units.

The amount of light produced is greater than from a standard halogen bulb, while the HID globe consumes less power and more closely approximates the ‘color temperature’ of natural daylight.

Light engineers talk of colour temperature in Kelvin units. It’s not important to understand the basis of the rating, but the comparative levels indicate why HID lights are brighter than conventional lights.

The typical colour temperature of a standard incandescent globe is less than 3000 Kelvin; a halogen globe falls into the 3000-4000 Kelvin range and HID lights exceed 4000 Kelvin.

HID lights have globes with wattages that are much lower than halogen lights. A typical HID globe is only 35-70W, compared with the average 100W for halogen driving light globes. Because the HID globe has no wire filament it’s much more durable than a conventional ‘hot wire’ globe and should last at least 2000 working hours.

Although it produces useful output when first ignited, an HID light requires a few seconds to come up to full output. In addition, if power to the lamp is lost or turned off, the arc tube must cool a little before the arc can be re-struck and light produced. We observed this ‘warmup’ phase in the HID lights we tested, as the light ‘temperature’ rose and the colour of the light changed.

In summary, HID lighting has three key advantages over conventional halogen primary lights: more light output, whiter light and longer service life. The main disadvantage is cost, but prices are falling steadily.

 

LED Driving Lights

Outback Travel Australia was chosen as one of the companies to evaluate the new Hella Luminator LED Series driving lights, prior to their Australian release in early 2012. Since then we've checked out many competitor LED lights.  

LEDs deliver bright, white, even beams and turn the road to virtual daylight out to around 550-750 metres.

hella leds

Brightness is on a par with HIDs and there is no sign of blotchiness, or unwanted reflector flare in the beams.

Light Emitting Diode lights work completely differently from incandescent and HID lights, generating photons of light at the atomic level.

Low-energy LEDs emit in the infra-red spectrum and are used in appliance remote controls. Higher-energy designs emit light in the visible spectrum.

LEDs emit light directionally, so they can be arrayed with small, individual reflectors, as in light bars and most LED driving lights, or with a large reflector, as in Hella’s Luminator LED and Narva Enhanced Optic lights.


 

 


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