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I have had a skim through it, but the mainstay of the power consumption charts seem to be relating to LED's at their optimum operating voltage, the power loss from and additional components needed to convert another voltage , 12v for example, to the ideal LED operating voltage still seems to be another issue and must use more power!

Another interesting thin I have found by reading the listings of ebay LED vehicle bulbs, very few make any mention of the power consumption or give any figures, it just seems 'assumed' that consumption will be lower. As it would be if you replaced a 4v filament bulb for a 4v LED, In a vehicle application this makes little difference and there are other benefits to LEDs but if lowering power consumption is your aim then maybe LED bulbs aren't all they are assumed to be :nenau
 
18 years ago I completed a National Diploma in Electronics, I have just read through this and decided I haven't the first clue how I managed to pass.
 
you would love the stuff me an Briggie have been going through then! A nice university research paper on LED's with load of equations. We are both ex tv engineers, from when they were big and heavy and made of glass and videos had tapes that top loaded :thumb2
 
oh the fun of shorting the final athode to the chassis ..... those where the days :lol:lol:lol
 
I gave myself a shock doing that once! my hair stood on end and my tie straight out at 90% in front of me! And i burnt two small holes in my finger right down to the bone :eek:
 
when I was a kid, my dad was always bringing old TV sets home to try and repair, needless to say most got bunged in my direction to pull to bits, I found the quickest way to kill earth worms was the spark from the final anode, what fun we had then, could you see that today, Rick
 
Rustic - for some reason the quote button isn't working but cheers for that! As i really need to drop my power consumption now the nights are drawing in :thumb2
 
To answer the original question it depends on the type of lighting fitted in your caravan. If you have fluorescent lights fitted the LEDs will be only very marginally more efficient as their efficacies are similar (but the latest LEDs win).
If you drive them via a resistor to control the current you are on a looser as the resistor just converts the excess voltage (and hence power) to heat. If you buy switch mode LED drivers the conversion efficiency should be over 90% and you can series LEDs, work on each LED needing around 3 to 3.3V at their rated current.
The big problem with home construction is getting the heat out of the LED body, at work we build high power LED light engines on PCBs with an aluminium substrate and these are then mounted on aluminium heatsinks. Small low power LEDs can be mounted on FR4 but you still need to back the assembly with some form of heatsink.
In your position I would look at a ready made solution, Labcraft got a good write up in RadCom for their 12V LED lamps and no I don't work for Labcraft but I do work for a UK company that manufacture 100,000 LED drivers and light engines a month!!
 
edgerton19 said:
To answer the original question it depends on the type of lighting fitted in your caravan. If you have fluorescent lights fitted the LEDs will be only very marginally more efficient as their efficacies are similar (but the latest LEDs win).
If you drive them via a resistor to control the current you are on a looser as the resistor just converts the excess voltage (and hence power) to heat. If you buy switch mode LED drivers the conversion efficiency should be over 90% and you can series LEDs, work on each LED needing around 3 to 3.3V at their rated current.
The big problem with home construction is getting the heat out of the LED body, at work we build high power LED light engines on PCBs with an aluminium substrate and these are then mounted on aluminium heatsinks. Small low power LEDs can be mounted on FR4 but you still need to back the assembly with some form of heatsink.
In your position I would look at a ready made solution, Labcraft got a good write up in RadCom for their 12V LED lamps and no I don't work for Labcraft but I do work for a UK company that manufacture 100,000 LED drivers and light engines a month!!
Click to expand...


Interesting stuff but! my intention was/is always to use something ready made i.e. the ready made Led "bulbs" available to for use in cars. My point was that these all seem to use resistors that, as you say, waste the extra power as heat. In the case of indicators they would have to do this to work! So while there are benefits to LED replacement bulbs is energy saving one of them or is it just an assumption we all make.

So if i buy these for example:

http://www.ebay.co.uk/itm/2-x-LED-L...White-/270868469102?forcev4exp=true&forceRpt=

note the seller makes no claims regarding their efficiency! They can't use less power as they must use a ballast resistor to make the flasher unit in the car work and therefore use the same power in total!
 
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well i tried to convert the caravan to leds to save power on non hook up sites.

found they ran cooler than regular bulbs, though just like the hosehold types
gave much less light than regular bulbs.

in end went back to regular bulbs which also give a warmer light than led.
 
Thomas-the-Terrano2 said:
well i tried to convert the caravan to leds to save power on non hook up sites.

found they ran cooler than regular bulbs, though just like the hosehold types
gave much less light than regular bulbs.

in end went back to regular bulbs which also give a warmer light than led.
Click to expand...

there are so many different LED replacements you will be surprised! with more or less LED's and even different colour tones like 'warm white', just type G4 LED into ebay as an experiment. Noe i am convinced these will use less power as they aren't car bulbs but a BA15 base usual means indicators and as such has a ballast resistor. I think I have sussed it though and have ordered some more to day to experiment.

I will let you know how it goes :thumb2
 
The problem is, you are looking at just one thing, and with LED's you have to look at a much broader picture..

Even if you ignore the longer life, and less degeneration, and stick to just worried about making a battery last as long as possible.

Basically, LED's do not have to draw the same current, in order to produce the same amount of usable light...

E.g.
LED's put all their light out in one direction, so waste less light.
LED's run cool, so are wasting less energy as heat.
LED's produce a far tighter spectrum of light, so are not wasting power producing invisible Ultra violet and infra-red frequencies.

Have a look here.
http://www.ledtek.com.cn/info/faq-2011070801.htm

The next problem is deciding how much light you need, as most bulbs are measured in Watts, but that is just how much electricity is used, not how much light is put out. Currently it is very hard to work out true comparisons, not only as traditional bulbs do not always publish their light output, but also because they radiate the light in nearly all directions, where as an LED concentrates the light in a beam in just one direction.

The bottom of this site gives some comparisons of power for a given light output, http://www.designrecycleinc.com/led%20comp%20chart.html and it can be seen that they say a 5w LED is the same as a 40w incandescent light both producing 450 lumens.

So a 5w LED running on 12v would be drawing 0.42amp, as opposed to a 40w incandescent bulbs running on 12volt would be drawing 3.33amp.

A CREE LED, set up to produce 460 lumens, needs 1.5amp at a voltage of 3.25volt. the corresponding resistor for that to run on 12volt, sticking to preferred values would be 6.8ohm 13watt.

Therefore the resister would be dissipating just under 13watt, and the LED would be using just under 5watt, resulting in the LED/Resistor combination using 18w, for the equivalent of a 40watt incandescent bulb.

Having said all that, if I was making a 12v LED CREE bulb of that power, I would use 2 or 3 LED's in series, and a smaller resistor, which could drop the power to 14 or 16watt.
 
I dont understand what this debate is about.Ive just installed 2 4.5watt work lights on my fourtrak they light the whole place up.If i had put 2 5w sidelight bulbs there it would do nothing.In my opinion the led lights are far brighter than my headlights and use a fraction of the power.
 
cncfabs said:
I dont understand what this debate is about.Ive just installed 2 4.5watt work lights on my fourtrak they light the whole place up.If i had put 2 5w sidelight bulbs there it would do nothing.In my opinion the led lights are far brighter than my headlights and use a fraction of the power.
Click to expand...

how do you know they use less power have you measured it :augie

but seriusy in the application you mention I have no doubt that they do use less power. But! try using a Ba15 LED bulb intended for a car indicator and supplied as a replacment caravan spotlight bulb and you may find you are using more power due to the "canbus" compensating components.
 
Leds instead of strips

A couple of years back I bought a roll of sticky back led strip from ebay and converted all the strip lighting in the van from twin flourescent to three strips of led. I can now run all the lights in the van, that's 6 light units and the current draw isn't even the equivalent of one of the twin strips.
The light output is if anything brighter than before and when listening to the radio on long wave (shipping forecast and all that) no interference from the ballast circuit.
 
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