12V lighting for off-the-grid cabin

keeth

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Hi everyone,

i'm building a small off-the-grid cabin with a modest solar PV system, and I'm trying to design an interior lighting system that gives the most light for the fewest watts, and runs at 12V, to avoid needing an inverter.

The cabin is one 10'x16' room with a loft bed and high (10-14') vaulted ceiling.

My initial idea was to do a cable lighting system, replacing the MR16 halogens with LEDs. However I'm still looking around for other options.

Last year I experimented with an automotive-style bulb made of 42 warm white LEDs and found it was not nearly bright enough. After a bit more research it looks like I was naive thinking I could light a large room with a 1.5W lamp.

After reading some posts on this forum, I'm thinking of trying some 12V bulbs driven by super-bright cool white LEDs (Cree/Luxeon/etc). I can always use candles if I want warmer lighting for a dinner or something. A more realistic energy budget for this system would probably be 15-20W.

I'm open to any suggestions at all on how to do this better. I'm sure others out there have attempted something similar to this. Any recommendations are appreciated be they general design tips or specific products.

Thanks in advance! :D
 

LEDninja

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:welcome:

You can get MR16 Cree bulbs though I find the narrow beams a problem. You will need multiple bulbs as a 100W bulb is 1400+ lumens. Your automotive bulb is listed as 115 lumens.

3x1W US source 200 Lumen (White); 180 Lumen (Warm White)

3x2W canadian source 300LM(Cool White), 240LM(Warm White)

3x2W Australian source Warm White 260 lumens
PM WeLight for more info.

-

There are LED linear and flex modules.

-

You can build your own LED fixture(s).
 
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Dave_H

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I saw some 12v strip lighting in either (can't remember) Home Depot
or Rona (both in Canada). It came with its own wall-plug switching
adaptor.

Dave
 
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RobertK

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Hi keeth.

If you aren't worried about making your own fixtures, I'd advise using a Bridgelux BXRA-W0402-00000. I was looking at their LED arrays again, and saw this model on Newark. This one operates on ~6.3W and outputs 460lm of warm white light; roughly speaking, you could fit 3 of these into your energy budget.

Just for reference (see this thread), this model is roughly equivalent to a 100W lightbulb in its 120 degree throw.
 

Linger

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A number of emitters spaced across the ceiling, mount each on a steel plate (size of a CD) for heatsinking.

*I recommend bringing a desk lamp, a 12v halogen (you could stock 5w and 10 w bulbs). If you lop off the transformer you might be able to feed the 12v circuit right into the lamp cord. After a while the hollow spectrum of LED light gets to me and I forsee you really enjoying the option of %100 CRI at times.

-a few cree mc-e emitters. The mc-e is 4 dies, emitter can be wired in series. A few parrallel mc-e's along your ceiling would be decent. mc-e's about $12-15 from Cutter. You can get really good colour.
-Alternately some discount C bin P7's wired in series.
-Alernately a single CBM-360: 4x luminus ssr-90 dies on one copper chip.
 

James Jackson

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Howdy!

10 x 14 ain't that large and is possible to illuminate the way that you are wanting to do - using a small 12-Volt system.

I have been using a small system for almost 3 years now, and the LED lighting is doable.

There are a couple of approaches that you could consider...

1) Using a 12-Volt track-lighting system - modified to use your 12-Volt battery. I used one of those for about 2 years, consisting of 3 MR-16 LED 'bulbs' - that put out about 145 Lumens each, for a total of about 435 Lumens of light. This will light the room, but maybe not be a 'blistering white' light.

2) As others have mentioned, you can make your own LED lights. That is the direction I am now going, my latest lighttubes put about 500 Lumens in a 6-inch long tube. I will put 4 of these onto my light-tube - for a total of about 2000 Lumens.

Look up my history of postings to see what I currently have up on the wall, and how it lights up the room. My mobile home is about 16-feet wide and the coverage I am lighting is about 25-feet long.

Be sure to use an LVD of some sort - to disconnect your battery when it gets discharged - so that you do not destroy the battery.

If you need more info, contact me, and I may be able to help.

Regards,

James Jackson
 

TorchBoy

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:welcome: keeth.

A number of emitters spaced across the ceiling, mount each on a steel plate (size of a CD) for heatsinking.
...
-a few cree mc-e emitters. The mc-e is 4 dies, emitter can be wired in series.
I like the steel plate idea but a 12 V battery system is unlikely to have enough voltage for four white LEDs in series.

A Cree XP-G is the most efficient LED around at the moment; at 1.5 W (like your 42 LED bulb) it produces about 200 lumens. If you want to light up the room reasonably well you'd probably need at least six times that, which you could do with as few as 3 XP-Gs (1.2 A each, total 15 W including 80% driver efficiency), or, say, 8 of them (360 mA each, total 10.5 W including 82.5% driver efficiency) depending on how hard you wanted to run each one. (They get less efficient when run harder.) Either way, it comes in within power budget. You can get heatsinking MR16 housings to put them in. :tinfoil:
 

jason 77

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Hi keeth.

If you aren't worried about making your own fixtures, I'd advise using a Bridgelux BXRA-W0402-00000. I was looking at their LED arrays again, and saw this model on Newark. This one operates on ~6.3W and outputs 460lm of warm white light; roughly speaking, you could fit 3 of these into your energy budget.

Just for reference (see this thread), this model is roughly equivalent to a 100W lightbulb in its 120 degree throw.

I second this idea of using bridgelux leds, I have five or so of them and the warm and neutral white ones are extremely bright and put out a nice color.

3 to 4 of the BRIDGELUX BXRA-N0400-00000 run in parallel should put out plenty of light for a room that size. Plus since they only need like 9-10 volts a piece they would be perfect for your 12VDC supply.
 

Dave_H

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I'm open to any suggestions at all on how to do this better. I'm sure others out there have attempted something similar to this. Any recommendations are appreciated be they general design tips or specific products.

Thanks in advance! :D

You didn't mention overall budget for this project, but it would certainly
help to narrow things down. My experience is rather limited to lighting
small rooms with individual (including battery-powered) lamps that
would not likely be practical to you. I have yet to build custom
lighting but will take the dive sooner or later (hopefully sooner) ;)

Meantime, I have found a commercial 120v 2W LED bulb (Sylvania)
which lights my upstairs hall to a nice warm light; not too bright
but very good dispersion. It costs $10. You may find a 12v equivalent
somewhere. A simple solution would involve finding suitable fixtures
and wiring them up.

True experts have more ideas about mixing different LED colours
etc. which is fine but tends to complicate the design.

Dave
 

blasterman

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In regards to Bridgelux, I'm in the process of building some killer drop rails using the 402s, and not even considering Cree. I need +3000 lumens of light, and only the Bridgelux gets me there with the right budget and flexibility. They also just got their energy star cert on the ES line.

However, I would NOT use Bridgelux for this project. Main reason is that their warm-whites are very inefficient and not the ideal match for a battery anything. They look awesome and have a superb lumen to price ratio, but they are dogs on efficiency. The Bridgelux cool whites are better in this respect.

Also, the only way to work a Bridgelux in a 12volt circuit is to either waste power with a resistor, or you'll need a 500ma buck. It's easy to do, but another problem is you then have a lot of light coming from a single spot in a small area. You have no idea how bright a 450lumen emitter is stuffed in a corner and how obnoxious it it.

My advice for the OP is his original idea, and that's to use higher quality Cree based 12volt MR-16s. These will get you the best efficiency and color with the least screwing around. If you go DIY, I would just bolt some neutral Crees to some Alu bar and run it off a 700mA buck.
 

TorchBoy

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... another problem is you then have a lot of light coming from a single spot in a small area. You have no idea how bright a 450lumen emitter is stuffed in a corner and how obnoxious it it.
It's incredibly harsh. How optically efficient is the prismatic plastic that's used for fluoro tube fittings?

Some wonderfully diverse ideas in this thread. I like. :twothumbs
 

blasterman

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Very efficient. Over 90%, but it only works mediocre on small point sources like LEDs, but better than nothing.
 

watt4

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welcome to cpf.


you could hang some LED lanterns ( 8-D cell type ) with wiring to the battery system.

benefit would be the dual-use ability: wired into cabin power with no batteries internally, or temporarily stick some D-cells in them and use them outside.

there are 8-D cell fluorescent lanterns, too.


also, you could take them with you when you leave.


http://www.walmart.com/ip/Coleman-Twin-LED-Lantern/13849011

http://www.walmart.com/ip/Coleman-Family-Size-Lantern/13849010

http://www.walmart.com/ip/Coleman-8-D-LED-Family-Sized-Lantern/8223656
 
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Dave_H

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I had a look at the strip lights at Home Depot. The 12'' 15-LED one
is $40 (CDN) and runs from AC. Cold white, not very efficient (gets
pretty warm) for the amount of light output. Disappointing so I
don't recommend it. Consumption is ~1W.

The 12v light is a 30-LED (5x6) grid of similar 5mm LEDS, for
$50. Comsumption rated at 2W. Supplied adaptor is 12v/1A,
good to power 3 or 4 of these. Not that great either but it's good
to find out. Must be something better out there for same or less
money.

Dave
 

Dave_H

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My advice for the OP is his original idea, and that's to use higher quality Cree based 12volt MR-16s. .

Any in particular you can recommend, especially available over the counter
retail? Don't know about the OP but I'm the type who likes to see stuff
before I buy it whenever possible.

Dave
 

blasterman

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Cutter has some nice MR-16 12-volt retrofits, and they stand by their products.

The typical 5mm beehive light is pretty much garbage, along with most of low end junk sold at big box stores. A single Cree often puts out more light.

The cheap_a_zoid way to do this is R2s from DX, a cheap heat sink, and 12volt driver.
 
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In regards to Bridgelux, I'm in the process of building some killer drop rails using the 402s, and not even considering Cree. I need +3000 lumens of light, and only the Bridgelux gets me there with the right budget and flexibility. They also just got their energy star cert on the ES line.

However, I would NOT use Bridgelux for this project. Main reason is that their warm-whites are very inefficient and not the ideal match for a battery anything. They look awesome and have a superb lumen to price ratio, but they are dogs on efficiency. The Bridgelux cool whites are better in this respect.

Also, the only way to work a Bridgelux in a 12volt circuit is to either waste power with a resistor, or you'll need a 500ma buck. It's easy to do, but another problem is you then have a lot of light coming from a single spot in a small area. You have no idea how bright a 450lumen emitter is stuffed in a corner and how obnoxious it it.

My advice for the OP is his original idea, and that's to use higher quality Cree based 12volt MR-16s. These will get you the best efficiency and color with the least screwing around. If you go DIY, I would just bolt some neutral Crees to some Alu bar and run it off a 700mA buck.

I've got that little 15W flashlight buck/boost converter from DX- I don't know if it goes up to 12V input yet (will have to look to see if anyone tested), but it does pretty darn good with 9V in.
 

csa

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Remember to run your LEDs at lower than max brightness. If you've got everything running right up to the absolute max, you lose a lot of efficiency. Your best bet is going to be well-heatsinked emitters scattered broadly, rather than trying to get a few to put out a lot of light.

Heat is your enemy here, since it's not light. Minimize your production and save the electrons for lumens. :)
 

Light Sabre

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You didn't mention what type of batteries you were gonna use in your system I would assume lead-acid. FYI: marine/deep cycle batteries will take running down to lower voltages and will take repeat charge/discharge cycles. Car batteries don't like this type of treatment at all. It dramatically shortens their life span. Don't want ya left in the dark unexpectedly, but I'm sure you would have flashlights and portable lanterns as backups.
 

SFG2Lman

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I did this as a kid actually! it wasn't a cabin, but a "fort" (thing taj mahal in the trees) we "procured" a car battery and a solar charging system from an automatic deer feeder and we wired up a bunch of LEDs. This was back before high powered LEDs so we were really excited about the white 5mm ones lol. (me and my cousin were the weird kids...but we had the coolest fort!)

Anyway, the recommendation that I have is to either go indirect, or get diffusers. Harsh glaring doctors office style lights are usually not very "camping site" friendly. I know there are some losses in efficiency, but I would most definitely take those. CREE just announced the most efficient "warm light" ever, so it may be worth checking in to those. If you drive the CREE at 350ma each...heat buildup shouldn't be too bad of an issue. Anyway now that I have typed a lot and said almost nothing...my recommendations are 7-10 CREE, Indirect/diffused, and that should get you a well lit room. "Modular" lighting is always helpful too, build 7-10 fully contained lights (driver, sink, emitter, diffuser) and put them up temporarily and experiment till you find the perfect dispersion and fewest number, and then screw em up and run permanent wires. (run the extra's by the porch, bathroom/port-a-potty, or woodpile.
 
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