54 Low Voltage D.C. Lighting Tips

54 Low Voltage D.C. Lighting Tips

Getting the most out of your low voltage d.c. lighting.

The two main types of low voltage direct current lighting are fluorescent and L.E.D.

(light emitting diode) lighting.

Low voltage d.c. fluorescent lights use the same tubes as conventional a.c. lights.

The inverter/ballast takes low voltage direct current, inverts it into alternating currents

and sends it to the fluorescent tube as a high voltage / high frequency current.

The gas in the tube ionizes and fires (lights up) the tube.

Once the tube is lit, the voltage and frequency drop to a level which keeps the tube running

How to get the most life out of your fluorescent tube and fixture.

It used to be common to see fluorescent tube packages marked with a life span of ten thousand

hours, and in small print it would say with a three hour minimum run time.

The gas in the tube ionizes to light the tube each time it is run, this also breaks down the gas and the

internal connections a little each time and causes the dark rings on the ends of the tube.

The inverter/ballast also draws a high current to get the tube to light. This high current draw heats up

the electronics and reduces the life of the components.

As the tube ends darken they put more stress on the inverter/ballast.

If you replace worn tubes in a timely manner the inverter/ballast will last longer.

A very important factor in the life span of a d.c. fluorescent light is the voltage drop to the light.

Remember the formula: watts (power) equals volts (pressure) times amps (quantity.)

A 12 watt fluorescent light requires app. 12 volts at 1 am to run.

If the wire size is too small for the length of wire between the light and the battery it will cause the

inverter/ballast to draw too many amps which increases heat to the components.

This can also be caused by letting the battery voltage drop too low.

Either way, if the voltage at the light is too low the inverter/ballast will draw too many amps to fire

and run the light which will cause early lamp and/or electronics failure.

In short:

Keep the wire size appropriate for the amp draw and wire distance in your lighting circuit.

If you have many lights on the same wiring circuit please base the wire size on the total amp draw,

plus about 20% for starting and use the total wire length for your calculations.

The light at the end of a wire run will receive the lowest voltage, especially if other lights are in use

at the same time.

When the tube ends darken, replace them.

Minimize the on/off cycles, a different type of lighting may be more appropriate for use in

hallways and closets.

Always allow the fluorescent light adequate ventilation to provide cooling which extends the life

of the inverter/ballast.

This is especially important with compact fluorescent lights as the tube is usually facing down and

the heat rises into the inverter/ballast.

Low voltage d.c. L.E.D. lights are very energy efficient and can tolerate many on/off cycles

as well as a low input voltage.

Two things can shorten the life of an led light.

The first is over-voltage.

If these are used in an alternative energy system and the input voltage is set too high (e.g. over 14-1/2 volts

for a 12 volt system) the led's may fail. For systems with a high charging or equalization set-point

voltage you will want to make sure that the led lights are turned off during charging.

Many charge controllers allow users to set charging voltages as high as fifteen volts on a 12 volt system and

this can cause led failure.

Another cause of failure with led lighting is over-heating.

The high-output led lights will produce a noticable amount of heat, which is why they are vented for cooling

and have heat sinks to draw off the heat.

If these high-output led lights are used in a sealed (non-ventilated) fixture they will overheat and cause a

cascade failure of the led's.

On these high-output led lights, one watt per LED or greater, make sure that the heat generated will be

able to escape from the light.

You may notice that some of the high output a.c. led lights have the leds set into a cast and finned

heat sink.

Many of the super-bright led flashlights use the aluminum flashlight body as part of a heat sink.

The above is copyright by John Drake Services, Inc.

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