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LEDs Versus Halogen and Stobe

Written by PFM Staff

If you are new to fleet management, or have not been in the market for a lightbar lately, you will now find the entire lightbar industry has changed. Just a few years ago, just a few manufacturers existed, and your choice was basically between a halogen bar or a strobe bar. Today, those veteran lightbar makers still exist, but many new companies have joined the market. And the entire police lightbar industry has converted to light emitting diode (LED) lightbars.

LED Emergency Lights

Simply put, buy an LED lightbar, period. The use of LEDs has revolutionized emergency lights because LEDs have solved both concerns of the older lighting systems.

The halogen lights were bright and reliable, but they pulled so much current that they outpaced most alternators, even the high-output police package versions. When the current draw exceeds that of the alternator, current is taken from the battery, which slowly drains it. Today’s batteries cannot be deep-cycled (drained dead) like the old style of batteries.

And today’s police vehicle already has heavy amp-draw demands from other emergency and communications gear. Plus today’s police vehicle has huge electrical demands for the powertrain and body control functions. The vehicle itself needs most of the alternator output and cannot spare much for police gear.

To make matters even worse, the rated alternator output is the maximum possible under ideal test conditions. As the ambient temperature goes up, and as the under-hood temperature goes up, the alternator output falls off. Powertrain controllers that automatically increase the idle rpm as they detect heavy amp-draw help a little bit, but not enough.

Too Much Amp Draw

Alternator output varies by police car make, but the math is the same. The alternator never produces the rated output in actual use. The vehicle already uses most of the power, depending on the vehicle accessories in use, i.e., A/C, rear window defroster, radiator electric fan, heater motor. Some of the police equipment has a steady power draw, i.e., laptops, radar, in-car camera. Precious little power is left for the flashing emergency lights.

Those halogen emergency lights pulled up to 75 amps! That is more than any powertrain or body control function, and more than any other piece of emergency equipment. When that halogen lightbar was activated, the battery immediately started to drain. The halogen lights activated for a long period of time could drain the battery dead, even with the car running. Best case, the battery was deep-cycled during this use. And some batteries fail completely after being deep-cycled just a half dozen times.

In comparison, a fully activated, multi-function LED lightbar pulls about 14 amps, and many lighting functions on the LED bar pull less than 5 amps. The widespread use of the LED lightbar has single handedly made existing alternator capacity enough for police use in almost every police application. Yes, we are putting more electronic components into vehicles, like e-ticket printers, but out-running the high-output police alternator today is a clear exception, when it used to be the rule. The single reason is the use of low amp-draw LED emergency lights.

Bulb and Rotor Reliability

Another concern with halogen lights was long-term durability and reliability. This is no fault of the lightbar maker. All lightbar makers produced good equipment. The facts are that all light bulbs burn out, and this includes halogen light bulbs. Moving parts, like rotator gears, wear out. Electric motors driving the rotators burn out.

Fleet managers want to transfer as much police car from the vehicles they are taking out of service to the new vehicles. This is especially true for expensive items like lightbars. Yet halogen lightbars typically do not have the long-term durability and reliability to be passed on more than once.

Yes, halogen bulbs can be replaced. Yes, drive gears and fractional horsepower electric motors can be replaced…but no one does that. The thinking is that if one of the motors burns out, or one of the gear sets strips teeth, the other motors and gear teeth cannot be far behind. If a halogen bulb burns out, the other bulbs cannot be far behind.

In comparison, the LED emergency lights have no moving parts. Nothing to wear out. And the LED emitter itself is good for 100,000 hours of use. The LED light is not going to burn out in anyone’s police career. As long as the electrical circuit (wire or printed) remains intact, the LED will last longer than anyone cares about.

Strobes

The LED has also essentially replaced the strobe lightbar. The reason is not amp-draw like the halogen bar. Instead, the high-output power source for the strobe lights was simply not as reliable as many police fleet managers expected. The heavy, shielded cable for the strobes running from the power source to the strobe bulbs was a bit of an issue. The life of the strobe bulb was a bit of an issue. The intense heat generated by the strobe bulb was a bit of an issue. Again, in comparison to strobes, LED lights are more durable and more reliable in police service.

To be sure, both halogen and strobe emergency lights still exist! Most emergency light makers still produce these. They are much less expensive than LED emergency lights. They may be the right lights for some applications. Just consider the advantages of LEDs and the disadvantages of halogens and strobes before you buy.

LED Brightness

For some time, fleet managers were concerned that the LEDs would not be bright enough. Halogens and strobes always produced powerful emergency signals, from bright sun to rain to fog. Turn around is fair play. Today, a concern about LED emergency lights is they are too bright!

In fact, most lightbar controllers today include some sort of a dimming button for the LED lightbar. These are generally wired to default to the bright mode, and the dim mode is generally not functional in some high-activity light modes. Suffice it to say, today’s LED emergency lights are as bright, if not much brighter, than the halogen and strobe lights of old.

Last Frontier

Halogen and strobe lights have been the best choices in two separate areas, until just recently. In fact, even for veteran fleet managers, this has changed since the last time you purchased emergency lights.

Halogen lights remained the technology of choice for take-downs and alley lights until just recently. The white LED light was the last color to be developed. LEDs emit the color of light they were built to emit. They do not emit white light, which is then changed to a certain color by using a colored lens. Blue LEDs actually emit blue light, and only blue light. Red LEDs emit only red light. And so it is with white LEDs. White was the hardest color to make an LED emit.

As a result, the powerful white lights used in take-downs and alleys remained halogen even on fully LED lightbars. Yes, that means the LED part of the lighbar draws almost no amps, and the take-downs and alleys draw a bunch of amps! All that has just changed. Most of today’s modern LED lightbars use white LEDs for both front take-downs and both side alley lights. This use was the last of the halogens to disappear in police emergency lights.

Strobe lights remained the technology of choice for corner lights, the intense white lights mounted inside headlight, turn signal, taillight and backup light lenses. Again, the reason is the late development of a powerful white LED emitter. It has been just within the past year that an LED package bright enough and small enough has been developed for corner lights.

These LEDs have a single, significant advantage over strobes, in addition to getting rid of the strobe power source. That reason is the heat generated by strobes. The heat is so intense in tight and closed spaces like a headlight housing, that the strobes were actually melting the plastic housings or blistering the chrome reflective plating.

In fact, Chrysler Fleet specifically recommended against installing corner strobes in the Dodge Charger headlight lenses. All that has changed with the cool-operating LEDs. The corner LEDs are as bright and have as much “pop” as any corner strobe. This use was the last of the strobes to disappear in police emergency lights.

Published in Law and Order, Apr 2009

Rating : 9.3


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