# Led Strip lights and Power supply Help?



## deltawars (May 29, 2014)

Hi guys I come from LPF and I recently bought 50 of these LED strip lights 12v and 15W each and 2 400W power supply's.
My question is can I connect 25 of the LED strip lights for a total of 375W and connect them to one of the terminals on the 400W power supply?

50x 15W Strip lights(with heatsinks) and 2x 400W Power Supplys. Power Supply View 1








Power Supply View 2 25 Strip lights connected together


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## kingofwylietx (Jun 18, 2014)

While I don't know anything about your strips, I would be very surprised if they are designed for 25 of them to be mounted in series. You should check with the manufacturer to find the max allowed. 

I would prefer more headroom on the power supply. If I was building something that needed 375 watts, I would get a minimum of 600-750 watt power supply. That's just me, but I wouldn't be comfortable running 375 watts continuously through a 400 watt power supply.


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## BigK (Jun 18, 2014)

Allowing a 10-15% buffer is standard. You're barely allowing a 6% buffer. You're going to be working that power supply pretty hard.


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## Conte (Jun 19, 2014)

Not likely, there are 3 sets of terminals for a reason, and the small lead wires on the LED strips couldn't handle that kind of load.


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## riss6270 (Jul 8, 2014)

You are most likely going to have to run seperate wires from the buss bar. You may only be able to hook up 3 to 5 max. It should say the max run from where you purchased them from.


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## gorgeouslighting (May 3, 2015)

deltawars said:


> Hi guys I come from LPF and I recently bought 50 of these LED strip lights 12v and 15W each and 2 400W power supply's.
> My question is can I connect 25 of the LED strip lights for a total of 375W and connect them to one of the terminals on the 400W power supply?
> 
> 50x 15W Strip lights(with heatsinks) and 2x 400W Power Supplys. Power Supply View 1
> ...



Hi LPF guy!

Before you want to choose the right power supply for your led strip lights, you should know the power efficiency firstly, normally, it is about 80% to 85%, (i.e. a 100 watt led driver should only be loaded with LED strip lights with a wattage draw of 85 watts at the most). Normally, led driver in higher power, the power efficiency will be higher accordingly.

So, the 375W led strip needs at least 442w power supply. Check this post Utility guide to choose the right led strip lights![h=2]*#4 **Suitable power supply/led driver for led strip lights*[/h]


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## RetroTechie (May 4, 2015)

gorgeouslighting said:


> Before you want to choose the right power supply for your led strip lights, you should know the power efficiency firstly, normally, it is about 80% to 85%, (i.e. a 100 watt led driver should only be loaded with LED strip lights with a wattage draw of 85 watts at the most). Normally, led driver in higher power, the power efficiency will be higher accordingly.
> 
> So, the 375W led strip needs at least 442w power supply. Check this post Utility guide to choose the right led strip lights!*#4 Suitable power supply/led driver for led strip lights*


Linked article only says that if you have a 100W rated LED driver, and it's up to 85% efficient, it won't output more than 85W so that's the maximum worth of LEDs it can drive. Power out < power in, duh...

In this case you simply have a 12V DC power supply whose max *output* is rated: 400W (33.4A). So if you'd load it with 400W, efficiency never being 100%, more than 400W will go in. _That_ number just isn't on the label, that's all. Like kingofwylietx said, better not load a powersupply continous to its max. That said: according to its specs, that's what it _should_ be able to handle (personally I wouldn't count on that, but hey  ).



Conte said:


> Not likely, there are 3 sets of terminals for a reason, and the small lead wires on the LED strips couldn't handle that kind of load.





riss6270 said:


> You are most likely going to have to run seperate wires from the buss bar. You may only be able to hook up 3 to 5 max. It should say the max run from where you purchased them from.


Oh dear, where to begin...

If those LED strips were all put in series, current through 1 would be the same as current through all of them (and thus the strips' wiring would be fine).

But they won't be put in series, since 12V DC from the powersupply is exactly what each strip takes. So they'll go in parallel, current through the whole lot will be high, but current through each individual strip will again be the same (15W / 12V = 1.25A per strip).

Of course those 3 sets of terminals are there to distribute that current over several connectors. So you'd take up to, ehm, 8 or so of those LED strips, tie all their red wires together, and connect those to a +V terminal. Then tie all their black wires together, and connect those to the matching -V terminal. Probably all those +V and -V are directly connected between themselves (check that!), so it it wouldn't matter which +V or which -V you use.

Repeat for the other 2 sets of terminals, and you have up to 24 LED strips powered. Repeat for the rest of the strips @ the 2nd power supply. Probably you'll need quite some length of heavy-duty speaker wire (or something like that) to tie everything together. Or perhaps use some metal strips as conductors? :thinking:

Did you do the math on the total lumens output of that setup? :wow: Are you lighting up a palace, or a 17-bedroom mansion? :laughing:

Personally with that # of LED strips I'd have put a few (say, 4) of them in series, and power it with a higher voltage like 48V DC. Less/thinner & simpler wiring. In this case that would mean getting other power supplies...  Also: this boatload of LEDs won't be dimmable? Just on/off? Have you already powered up a few to check LED tint & output?


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## kmossman (May 15, 2015)

It has been a long time...........so what did you do?!

my 2 cents

400W power supplies are rated............wait for it...................for 400W !!! 
Efficiency just reflects how efficient they are at converting the input to output.
However, for longer life and for possible [over-]heating concerns it is common to 'de-rate' - use at a lower wattage than the rating.

The Wattage for LEDs, in general, is very suspect. Vendors and factories use a variety of methods to concoct the figure. It is NOT always V * I, as we presume.
I recommend measuring the current.

You can daisy-chain them [series], but as the internal and external wiring is thin the voltage can often drop significantly. Most folks find that by the 4th or 5th strip they start to dim.
You can just limit the number in series, or use a separate heavy duty bus[wiring]. 

Can you connect all of them to one power supply? Well yes, but see above.


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