Jeff;
I finally had to chime in.
There are plenty of nice DC power supplies out there that will do the
trick. I have used them in the past for small sensitive electronics that
can't take high equalize voltage. you can get them right from Digikey
and elsewhere in many capacity ranges, $20 and up.
But it sounds like they haven't given you any info on how the individual
LED series strings are arranged and regulated. Do you need one DC supply
for each, or just one for the whole thing? Your assessment is correct I
think -- parallel connections are BAD with LEDs, and the string with the
most voltage will eventually fail first, so best practice is regulate
every string.
And the words "void the warranty" sound extremely ominous, with scary
music playing in the background.
Why not just a Morningstar SureSine inverter? You keep your warranty,
and it's just down into the amperage range that there are some PV
controllers that could switch it via a low voltage disconnect, or you
could add a small extra relay. Wouldn't have to be big. From what I see
in your post, you'll be at 120 watts from LEDs max. The SureSine is
cheap, compact, low standby draw, and if you interrupt DC input via the
controller LVD and bring it back, it just turns right back on again with
no operator resett needed. I'm not sure about what you'd need for the
timers, but I bet they are cheaper at 120VAC than at 12VDC. There are PV
controller/LVDs that will do this too, though maybe not exactly how you
need it.
just food for thought anyway!
--
Dan Fink
Executive Director;
Otherpower
Buckville Energy Consulting
Buckville Publications LLC
IREC / NABCEP accredited Continuing Education Providers
(970) 672-4342
On 12/16/2011 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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