Wiring led lights for 12v solar use

flyingvranch · Mar 8, 2013

I currently have a 12 volt solar panel system wired throughout my cabin. The battery voltage runs from 12.2 volts up to 14.4 volts depending on if it is daylight and the panels are charging the batteries. For battery equalization voltages I shut down all the lights for safety as the voltage usually runs up to 15.5 volts for several hours. ( I only do this once a month anyway)

I found some nice under counter puck led lights at HD that run off 110 volt AC through a transformer that produces 30 volts DC output that then powers 3 pucks that are wired in series. I disassembled the lights and powered each one individually using a 12 volt dc bench power supply and they seem to work fine. My question is can I rewire 3 of these pucks in parallel to each other and then power them directly from my 12 volt dc system? This seems like a simple question but I have searched the forum till I am blue in the face and can't seem to find the answers. I am a complete novice concerning drivers etc. I am well versed on solar power however and I just need to see if I can get these lights to work for my particular application. Thank you very much in advance!

rmteo · Mar 8, 2013

Yes. (reply must be at least 5 chars).

ianfield · Mar 9, 2013

flyingvranch said:
I currently have a 12 volt solar panel system wired throughout my cabin. The battery voltage runs from 12.2 volts up to 14.4 volts depending on if it is daylight and the panels are charging the batteries. For battery equalization voltages I shut down all the lights for safety as the voltage usually runs up to 15.5 volts for several hours. ( I only do this once a month anyway)

I found some nice under counter puck led lights at HD that run off 110 volt AC through a transformer that produces 30 volts DC output that then powers 3 pucks that are wired in series. I disassembled the lights and powered each one individually using a 12 volt dc bench power supply and they seem to work fine. My question is can I rewire 3 of these pucks in parallel to each other and then power them directly from my 12 volt dc system? This seems like a simple question but I have searched the forum till I am blue in the face and can't seem to find the answers. I am a complete novice concerning drivers etc. I am well versed on solar power however and I just need to see if I can get these lights to work for my particular application. Thank you very much in advance!

LEDs need to be run from a current limited supply (can be as simple as a current limiting resistor if your fixed voltage supply is stable).

If you put 2 or more LEDs in parallel, due to slight manufacturing tolerances; one will hog more than its share of the current - it will then heat up more than the others causing its Vf to reduce and hog even more current.

The Vf is somewhere in the region of 3.4V for a white LED, so if you've stuck it on a 12V battery without anything to limit the current - its ready for the bin!

flyingvranch · Mar 9, 2013

Well I am a little confused by the two conflicting answers. For what it's worth, I have the string (3 pucks) wired up parallel and on my bench right now running off of a 12v power supply. So far so good, but I am worried about the longevity issues. Thanks for the help so far folks!

flyingvranch · Mar 10, 2013

Well I left the lights working via the power supply for several hours but I am disappointed because they get extremely hot. I think this is a design flaw too as I have another set that I bought that I hooked up per the package instructions using the standard driver that came with it and plugged those into the 110v AC wall socket. They get just as hot also. I would certainly never consider mounting these under a cabinet which is what they are intended for. Looks like a fire hazard either way....

ianfield · Mar 10, 2013

flyingvranch said:
Well I left the lights working via the power supply for several hours but I am disappointed because they get extremely hot. I think this is a design flaw too as I have another set that I bought that I hooked up per the package instructions using the standard driver that came with it and plugged those into the 110v AC wall socket. They get just as hot also. I would certainly never consider mounting these under a cabinet which is what they are intended for. Looks like a fire hazard either way....

Can you post a photo of your setup and/or list any part numbers?

snakebite · Mar 10, 2013

high power led's must dissipate heat.not as much as a bulb but they still need to get rid of it.
the puck housing is likely the heatsink.
post pics with the cover off.the power supply may be a constant current type.if there is no resistor or regulator in the puck the led's will become fed's.emitting smoke rather than photons.

flyingvranch · Mar 11, 2013

Here is a link to the product. http://www.homedepot.com/p/Hampton-Bay-LED-Black-Puck-Light-Kit-21343KIT-B/203000440#specifications

I am unable to directly upload attachments yet, apparently because I am a new member to this forum. Hope this helps!

ianfield · Mar 11, 2013

flyingvranch said:
Here is a link to the product. http://www.homedepot.com/p/Hampton-Bay-LED-Black-Puck-Light-Kit-21343KIT-B/203000440#specifications

I am unable to directly upload attachments yet, apparently because I am a new member to this forum. Hope this helps!

With the combined Vf of 3x white LEDs coming to around 10.2V, I'm inclined to wonder if they're relying on cable resistance to limit the current from a fixed voltage PSU!

SemiMan · Mar 11, 2013

If you have a current meter you could measure the current going to one light and see what the current is running from the battery. If they are the same or close (over the range up to 14.4), then you should be fine. If not, then it is time to look at other lights.

When you say "hot" could you hold them in your hand for a period of time, or so hot you drop them immediately? Even if the latter, it does not mean they are "too hot". Keep in mind the ignition temperature for any common materials is quite high and even discoloration does not occur till well over 100C. It is likely not an issue.

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Wiring led lights for 12v solar use

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