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Old 09-04-2009, 15:10   #1
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LED Lights and Oversized Batteries

Back in my youth, I learned quickly that incadescent 1.5 volt lights would operate on 1, 2 or many batteries, as long as the batteries were in parallel.

I've never heard this discussed here or anywhere else for that matter, but I thought I read somewhere that LED lights were not so much voltage dependent as they were amperage dependent. These LED's can be had so unbelievably cheap, that I want to change everything on the boat(maybe not navigation) and everything at my home to battery-operated(12 volt gelcells), on a single ciruit, much like good ole house wiring.

I ask this because I have all sorts of 4-1/2 volt LED lights for my boat, but the batteries only last about 3-4 days of use before they start to dim(AA batteries).

I am considering making battery packs of D-cell batteries which should last much, much longer and have absolutely no drain on my boat batteries.

I've also contemplated transforming down to 5 volts or so to operate the LED's from the boat battery.

BUT, in the back of my mind, although I can't find that certain information about it, I'm rather afraid that the D-cell(or reduced 12 volt batery), will burn the circuitry controlling the LED lights. Somehow, I've got it in my mind that in much the same way that incadescents would accept too high a voltage, that the LED's will accept too high an amperage.

Can anyone tell me if this is a valid concern?

IF not, I will be, in short order changing ALL my boat lights to LED in short order . . . cabin, courtesy, spreader-lights and whatever else I think of adding onto a single circuit, if possible(and if simple).
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Old 09-04-2009, 18:01   #2
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go to dr. led website .it will explain led's .i use sensi bulbs for all my lighting.they draw .3milliamps. there are many disscussions about led's on the boards just search....jt
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Old 09-04-2009, 19:08   #3
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I'm rather afraid that the D-cell(or reduced 12 volt batery), will burn the circuitry controlling the LED lights. Somehow, I've got it in my mind that in much the same way that incadescents would accept too high a voltage, that the LED's will accept too high an amperage.
As long as the voltage is within the spec, the battery capacity doesn't matter. You can use as big a battery as you want and it will not harm the LED as long as the voltage is correct.
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Old 10-04-2009, 06:05   #4
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Two winters ago(a year ago this past winter), I bought some strings of battery powered LED lights that ran on 4 AA batteries(series) and bought one of those 6-volt batteries.

I removed the battery pod(and in hindsite possibly removed required circuitry) and hooked the lights up to the 6-volt battery.

They worked just fine but even though the final voltage was the same the negative(?) contact began getting hot and even somewhat melted the insulation(just a little).

In reading about LED's I got the impression that amperage was a concern and this could explain the problem with my experiment(a problem I never encountered with incadescent), but maybe I was wrong.

I thought I also read that the lights milliamp requirement could be resolved in series multiple for a more capacity battery.

I'm somewhat miffed at how differently LEDS react to energy than incadescents do and know I need more study on this before I screw around.

AND . . . maybe my idea of stringing my entire boat with "cheap" LED lights on a single circuit(with individual on/off capabilities) on that same circuit is much more complicated than I thought?

One thing for sure is that LED's are different.
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Old 13-04-2009, 19:49   #5
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Cheap LEDs are probably not worth spending your effort on. Most have built in resistors, that render them less than efficient.

I've replaced most of the lighting on our boat with LEDs. No, they aren't cheap. Just spent another $260 for just the PARTS to do the forward cabin (2 fixtures) and the forward head (2 fixtures). The good LEDs put out light very efficiently, last 50,000 hours, and are state of the art. Try Cree LEDs - Led Driver - Led Fixtures - Led Optics - Luxeon LEDs - LED Supply.com. You will need a driver for the LEDs in order to insure they get a constant CURRENT - which is critical.
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Old 14-04-2009, 01:06   #6
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I've replaced most of the lighting on our boat with LEDs. No, they aren't cheap. Just spent another $260 for just the PARTS to do the forward cabin (2 fixtures) and the forward head (2 fixtures).
I have been thinking about a similar project. The new Cree and Rebel LEDs are amazing.
Hope to learn from your experience, please publish some details if you have a chance.
Thanks John
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Old 14-04-2009, 05:26   #7
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With LEDs the important thing is to get ones that use Buck driver instead of resistors; the Buck driver will regulate higher current by rapid switching, while a resistor will convert your precious energy into unwanted heat. You can tell the difference between the two by (a) the price and (b) the input current, the range of ones with buck converters will go up to higher voltages.
I replaced all of my G4 bulbs with ones from MAST and now can run over 20 LED lights and draw less power than if I turn on my 2 reading lights, which are still 10W halogen (I can't fit a LED in the socket and don't want to replace the whole assembly). The color temperature of the newer generation of LEDs is much better and comfortable for the eye than the older ones as well. I love the LED lighting system and their incredibly low power drain.
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Old 14-04-2009, 11:06   #8
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John,

I have some photos somewhere of the fixtures themselves I'll try and dig up. Here's the original thread I wrote about them:

LED Lighting Project Update

I'll try and take some more pix this week as I make my new ones for the guest cabin and head.
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Old 14-04-2009, 14:22   #9
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A simple inline resistor should do the trick to bring 12v down. One per LED, mind!
Good luck!
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Old 14-04-2009, 15:15   #10
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Anthon - My point in the earlier post was that you want to avoid having to any resistors in the circuit. The reasons for going to LED from incandescent are to lower energy use and to stop producing heat. A resistor will just convert that hard-won and expensive electrical energy into heat. The buck converter is analogous to the MPPT controller used for solar charging in that it will minimize wasted power; and they can be bought for use instead of inline resistors; although at about $10 they are orders of magnitude more expensive than a resistor, but over time they will pay for themselves in saved energy and a longer LED lifespan.
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Old 14-04-2009, 15:18   #11
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John,

I have some photos somewhere of the fixtures themselves I'll try and dig up. Here's the original thread I wrote about them:

LED Lighting Project Update

I'll try and take some more pix this week as I make my new ones for the guest cabin and head.
Thanks for the link Bill, I missed the original post.
It looks like a great project I would be interested to see some photos of the fixtures and how you engineered the heat sink etc
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Old 14-04-2009, 20:34   #12
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Surv, you'll do way better if you find & take a course in "basic dc electronics" or get a book on it. Among other things, LEDs run on DC and DC can't be "transformed" per se. Transformers only work on AC. There are ways to get around that--but nothing is free, much less quick or painless. You know how that goes. (G)

The LEDs don't care if you use AA, AAA, or D cells, as long as the voltage matches what they were set up for. The extra amperage doesn't just flow out of the batteries, it is potentially available--not necessarily able to flow.
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Old 14-04-2009, 21:10   #13
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For the simple 4.5v lights that use three AAA cells in series, larger capacity cells with the same voltage may well overdrive the LED. The reason for this is that the internal resistance of smaller cells will limit current to the LED just like a separate current limiting resistor. Larger capacity cells, even of the same chemistry and voltage, usually have a much lower internal resistance and will let more current flow through the LED, perhaps more than the LED is rated to handle.
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Old 14-04-2009, 22:08   #14
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Yeah, you really don't need to use resistors - it's a waste of power.

I looked for photos of my last ones I built, but so far, no luck. I'll take some pics of these this week.
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Old 15-04-2009, 06:53   #15
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Buck convertors are generally about 85% to 90% efficient, so even they waste some power, just like a current limiting resistor. Naturally a convertor can be the ideal solution, but they certainly add cost and another level of electronic complexity that can fail or add RF interference to the vessel environment. Using properly sized current limiting resistors and strings of 3 or 4 white LEDs in series, you may lose only 35% to 15% of your power to the resistor in a 12/14 volt system, gain reliability, avoid RFI, and save money.

I personally do like using a good buck convertor when using the high power (1 to 7 watt white LEDs) for these installations, but when using the low power 3mm and 5mm LEDs for less demanding lighting a current limiting resistor can make more sense, and very little power is lost in the greater scheme of things.
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