# 12V lighting question



## cowboy joe (Sep 14, 2003)

I remodeled the kitchen a few years ago and purposely put in 12V halogen track lights. They run off a transformer which knocks the AC down to 12Vac. Thinking I should be able to run these off of DC but thought I'd ask before I toast a $10 lamp. Anyone know if the lamps will handle DC?

Not the ideal set up as the 4 bulbs in two separate strings which draw a total of 80W. Thinking I'll hook half to the PV system for now. Looking to eventually switch over to LEDs with a MR-16 base as they appear to be more efficient (higher foot candle output per watt) so I should be able to reduce the load and still have decent light. Prices are all over the map for these...anywhere from $8/each to over $50. Still have to do my research to separate those that are decent from the pigs in a poke. Anyone using similiar type lamps or have any recommendations? Thanks in advance.


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## survivalpro (Nov 14, 2009)

If they are 12 volt lights they will run off 12 volt power directly bu not all 12 volt appliances use 12 volt and many have their own transformer that adjusts the voltage.

You can use an inverter to change 12volt to ac and run any ac appliances.

Or you can buy car 12volt appliances and lights and run those directly off dc.

I have an instructable and videos on solar dc and ac setup that might help you:

http://www.instructables.com/id/How-to-have-a-home-with-no-house-payments-and-no-u/


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## byexample (Aug 28, 2009)

Something to be careful/mindful of is that power supplies like the one that came with your lighting fixture produce a fairly consistent voltage... probably right around 12 volts.

Your 12 volt PV system will fluctuate all over the place from as low as maybe 11 volts to as high as 15 volts depending on your batteries and how you manage your system. Chances are 15 volts may be too high for a 12 volt lamp considering that's a 25% increase above 12 volts.

Even if the lamps will work with 12 volt DC, you may still need a voltage regulator of some sort. I had this experience with using 12 volt DC LED lights on our PV system. They had a very short life... lasted less than a year. I eventually determined that the natural fluctuations of our PV system had shortened their life and I modified our lighting fixtures to include a small 12 volt voltage regulator. That was 5 years ago and we haven't lost an LED light since.

In the past I would be tempted to theorize that a 12 volt AC lamp wouldn't work on 12 volt DC... but I recently saw someone using 120 volt AC incandescent lights *directly* on their 12 volt DC PV system. Wouldn't have thought that would work either... but evidently it does.

Suppose you are going to have to run the experiment and find out. I sure hope you'll let us know how you make out. I'm quite curious to know.

Be well and good luck!


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## cowboy joe (Sep 14, 2003)

byexample said:


> Something to be careful/mindful of is that power supplies like the one that came with your lighting fixture produce a fairly consistent voltage... probably right around 12 volts.
> 
> Your 12 volt PV system will fluctuate all over the place from as low as maybe 11 volts to as high as 15 volts depending on your batteries and how you manage your system. Chances are 15 volts may be too high for a 12 volt lamp considering that's a 25% increase above 12 volts.
> 
> ...


Yep, that's exactly what I was thinking about. The charge controller on the system spikes as high as 14.5V. Not real certain how the higher levels would effect lamp life. Guess there is no way to know other than to give it a try with a single lamp.

Thanks for the feedback on the LED lamps. I have a regulator already built which is too light current wise for the halogens but should handle the LED lamps without breaking a sweat.


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## frank (Dec 16, 2008)

I played with this a little... took some led(home depot 7 bucks) christmas lights, modified 'em to run on 12v. Each light needs 3-4 volts. Run 3 in series and you get 'em to work. They are pos/neg sensitive. Won't run unless wired right. 4 in series, not as bright.

By example, got a link for the regulator?


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## byexample (Aug 28, 2009)

frank said:


> I played with this a little... took some led(home depot 7 bucks) christmas lights, modified 'em to run on 12v. Each light needs 3-4 volts. Run 3 in series and you get 'em to work. They are pos/neg sensitive. Won't run unless wired right. 4 in series, not as bright.
> 
> By example, got a link for the regulator?


I just used the 12 volt voltage regulators available on the shelf at the local radio shack. It ran about $1.50 at the time. I also know that some of the larger electronics suppliers have dozens of different voltage regulators to choose from... but I always found the ones at Radio Shack to be just fine for my needs and there wasn't any shipping to pay. I'd expect they have those online as well.


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## roachhill (Jul 8, 2009)

You should be able to get boxes of LEDs at Radio Shack also. Then you can chose the exact voltage you want and you will know the amount of voltage variation it will tolerate (it should be on the back of the package expressed in a +/-% of the rated voltage)


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## 12vman (Feb 17, 2004)

I usually design my fixtures under 12 volts so there isn't a "flicker" issue when a high current item is being used like the water pump. I chose 6 and 9 volts which is two voltages easily worked with when using LED's.

Common white LED's require 3.2 - 3.8 volts to operate. I just figure 3 volts each and series connect them in pairs of 2 for 6 volts and 3 for 9 volts. I use the LM7806 for 6 volts and the LM7809 for 9 volts. You can run a bunch of LED's with these regulators being each "pair" of LED's draw around .030 amps. Connecting LED's in this fashion doesn't allow them to be at full brightness but they last for years. I have some fixtures thats been in operation for over 6 years.. 24/7.. with no failures.

Shop around for LED's. Radio Shack isn't the best place to get them. For the price of 3 white LED's from Radio Shack I can but 100 somewhere else..

http://www.ledshoppe.com/Product/led/LE1002.htm

*"I remodeled the kitchen a few years ago and purposely put in 12V halogen track lights. They run off a transformer which knocks the AC down to 12Vac. Thinking I should be able to run these off of DC but thought I'd ask before I toast a $10 lamp. Anyone know if the lamps will handle DC?"*

Yes.. It'll work but they'll be power hogs!!


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## cowboy joe (Sep 14, 2003)

12vman said:


> Yes.. It'll work but they'll be power hogs!!


Yeah, they were fine for grid tie but one of the reasons I'm looking to switch to LEDs. Bought the tracks, light fixtures, xformers and all the hardware for less than $5 total at the local Bargain Outlet on clearance. Little did I know how much the dang lamps would cost.


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## 12vman (Feb 17, 2004)

Look around in here and see if this might be a good place to grab a couple..


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## byexample (Aug 28, 2009)

I've been buying LEDs from http://www.ledshoppe.com for years now. Very good prices, good quality LEDs, and I've never had any problems doing business with them.

I definitely don't recommend RadioShack for LEDs. They are way, way too expensive. Even the voltage regulators are a little expensive... but since I didn't need that many of them it didn't really matter. Buying LEDs in bulk has saved us lots of money though... lots.


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## 1fast68 (Apr 20, 2009)

byexample,
what size LED's do you use? 3mm, 5mm or 10mm

Thanks


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## byexample (Aug 28, 2009)

I've been using 5mm LEDs. I have a short article on our site on the design and construction of our 12 volt LED lights. Pretty crude stuff... but it gets the job done and we're still using our lights 5 years later without any problems.

http://www.byexample.com/projects/current/led_lights/


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## 1fast68 (Apr 20, 2009)

Thanks byexample,
I just ordered some of them.


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