# Will 13v led lamps run on 12v?

Discussion in 'LEDs and Optoelectronics' started by Dmc112, Feb 25, 2019.

1. ### Dmc112

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Feb 25, 2019

Hi.
I have x16 3x3w 13v led lamps that l want to run from one transformer. I’ve calculated (at 13v) that l’ll need a 11.1amp/144 va transformer. As there are actually x2 rows of eight, lm also happy to use x2 transformers. My question is, as most transformers are 12v, will the 13v led lamps run on 12v and just be a little dimmer or a) not run at all b) damage the lamps?
The picture shows the lamp lm using, they are connected in two rows of 8, each row is paralleled and both ends come back to one point.
Hoping someone can point me in the right direction.

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
There are a couple of possibilities.

The first is that the original power supply is a led driver that delivers a constant current. In this case, replacing it with a voltage source could result in the LEDs not lighting at all, it them immediately being destroyed. There may be a little leeway between these outcomes, but not something you'd want to rely on.

The other likely option is that the lamps have drivers in them and probably run from a nominal 12V. A 13V power supply in this case will allow for voltage drop across long runs off cable. In this case, a 12V power supply might work fine.

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3. ### Dmc112

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Feb 25, 2019
Thanks for the help. I’ll enquire as to whether they have drivers built in. The transformer they were supplied with, which is just an LED power supply is this:

4. ### Externet

796
174
Aug 24, 2009
The picture shows output being from 8.6V to 13V with 23V as max. Seems like a constant current supply for a couple of series leds to several in series, maintaining a fixed 0.7A current.
Applying 12V regulated voltage not recommended. Seems the lamps have 4 led in series inside. with no limiting resistor. To run them on 12.0 V; they may not turn on or be dim.

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5. ### Bluejets

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Oct 5, 2014
Something not right there.
First photo shows the light with it's own internal driver ( input 220-240v 50 hz)
Although I would not be happy with single insulation as supply lead for 220-240v.

If it is indeed referring to the driver, then 1 driver per fitting.
13v 0.7A close enough to 9w ....which is what they say (3x3W)

6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,501
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Jan 21, 2010
The power supply, as others have suggested, is a constant current driver. Note the current is specified as "700mA(const)".

I suspect the light fitting just contains three LEDs in series and that the input power marking referees to the transformer.

If this is the case then you need one driver per light, they can't be wired in parallel.

There are always ways around this, but that's the simple answer.

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7. ### BobK

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Jan 5, 2010
If you want to run all 8 of these off a single low voltage supply, I would suggest an LM317 based constant current source for each lamp and a 15V 8A supply.

Bob

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8. ### Audioguru

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Sep 24, 2016
Dmc112 keeps talking about using a high current transformer to blow up the LEDs. He doesn't understand that a transformer has an AC output. The LED lights are designed to be used with the constant current 700mA DC power supplies for each light as shown.

I agree that those 700mA AC/DC power supplies can be replaced with a high current 15VAC transformer feeding an LM317 set for 700mA for each light.