[RE-wrenches] DC power for LED lighting

Fri Dec 16 15:29:11 PST 2011

Jeff,

About 8 months ago I built my first LED billboard powered by PV's. The LED light manufacturer could not deliver the 12 volt version fixtures in time but they had 120 volt models in stock. I modified the plans to use a Morningstar Suresine inverter. The system has been working flawlessly even through the 118 degree summer heat in Yuma. I used relay control to turn off inverter DC power during the day. Perhaps this will be a simple solution but you will need to add in the conversion losses. 

Larry Crutcher
Starlight Solar Power Systems

On Dec 16, 2011, at 11:24 AM, Jeff Yago wrote:

I have a local sign company that asked is to provide a solar lighting system for a double sided sign they were building for a large retirement community entrance.  We have provided many solar lighting systems just like this over the years and sent them several examples.  All our systems have been turn-key in that we provided the 12 VDC ground mounted LED flood lights with the separately pole mounted solar module(S) and battery/controller box.   We “assumed” when we told them our system includes the LED lights that they understood that we were providing the lighting. 

Unfortunately, when we arrived on the site to install the solar system, they said they did not need our LED lights, they wanted us to power the LED lights inside the sign.  We opened up the signs and found two 120 VAC electronic LED power supplies.  Each was clearly labeled as providing a maximum of 5 amps at 12 VDC output, and each powered a separate string of about 150 tiny plastic “blocks” and each block contained 2 small LED lamps.   We immediately advised the client that the solar  system was designed to power our two  12 VDC flood lights and we would have to totally tear out what we had just installed and go to a much larger system that included an inverter, larger array, 120 VAC timing device, and replace the 2 conductor DC underground wiring  with 3-conductor AC wire and all  this would really increase $$$.

I said as an alternative, why can’t we just cut out the two electronic120 VAC input  LED drivers since we are providing well regulated 12 VDC power direct from the GEL battery.   He checked with their LED lamp supplier and they said they strongly disagree and will void warranty.  Since we are talking about almost 300 total LED devices my client is afraid to give us the OK, even though we did run them overnight and everything worked just fine.   As I recall, an LED needs something in the circuit to limit the amp current, not the voltage flowing through it,  or it will just get brighter and brighter and then fail.  However, I thought almost all strings of separate LED lights already had some kind of regulator built into each light block otherwise those near the end of the string would be less bright than those near the power source.    Is this correct??

Finally, if strings of LEDs require some kind of voltage or current regulator, I can’t believe they all have to run on 120 VAC as indicated by this LED manufacturer who offers no alternative.    Any LED experts out there that can point me to some type of DC-to-DC converter or current  regulator that can replace these 120VAC LED drivers?

Thanks,

Jeff Yago

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