The selection of suitable cables is often underestimated for larger LED installations. LED strips operate in the low voltage range, z.B. 24 volt, which makes the current load rise quickly with the appropriate power. This is how z.B. An LED installation of 225 watts (a typical value for indirect room lighting) at 24 volts almost 10 amps of power.
The cables must be designed accordingly strong. If they are too thin, the voltage drop over the length of the wire will be so large that the leds will no longer be supplied with sufficient voltage and, if necessary, will be switched off. Shine darker or not at all. In addition, the cables heat up. In extreme cases, it even comes to the so-called cable fire and thus serious danger to life and limb! If possible the voltage drop across the cable should not exceed 5%. In addition to the connected load in watts, the length of the cable plays a decisive role here.
Which cable cross-section is the right one??
The following table provides a quick overview for selecting the appropriate cable cross-section (in mm²). It is for 24 volt and max. 5% voltage drop calculated:
For a 250W connection and 5m cable length we recommend a cable with at least 2 x 1.5mm² cross-section. 2 x , since plus and minus must be connected.
Particularly large connection powers and cable runs
For very large cable runs and powers, even 2 x 4mm² are no longer sufficient (empty, gray cells in the overview above). Here, either an even larger cross-section must be used (z.B. 6mm²) or 2 cables have to be pulled in parallel. So z.B. With a connected load of 400W and a cable length of 10m already two times 2 x 2,5mm² cable recommended. There is no cable cross-section that is too large overall. Only it must not be too small!
With the following small online tool you can easily calculate the voltage drop yourself:
The tool is based on the following simple formula:
Cables for RGB and RGBW LED installations
In the case of RGB and RGBW, the max. power consumption to the 3 or. 4 LED colors on. therefore one wire here (i.D.R. If the minus is used) each have a correspondingly smaller cross-section. The return line (i.D.R. The plus) but then almost all the power together again, so that here the conductor cross-section must be significantly larger. Professional RGB and RGBW cables take this into account and are equipped with different cross-sections accordingly. The following is the RGBW cable l4s-027 with 1mm² cross-section for the common PLUS and 4 x 0.35mm² for the individual MINUS connections:
All in all, for larger LED installations (over 5m) it is highly advisable to choose LED components with 24 volts instead of only 12 volts. At 12 volts, the current doubles abruptly and the cabling effort increases accordingly.
[total: 45 average: 4.8 ]
this is a very helpful and well explained guide. Now I also realize some of the problems I have had so far.
Thanks for the praise!
i would like to retrofit 4x12v 72w LED (in series) headlights on car. Which cross section do you recommend?
(cable length ca.2m)
i don’t know enough about your installation here and i don’t know at which voltage drop your 12V LED start to cause problems. According to our online tool for cable calculation, you will get by with 2 x 0.75mm² in this setup to just under 5% voltage drop.
Thicker cross sections are generally always better. So if you have the possibility there 2 x 1.5mm² or even 2 x 2.5mm² to lay, then just do that.
What setup is recommended if you want to dim multiple strips evenly and from one location?
Which dimmer(o.button) and which central (UV) power supply unit?
unfortunately this question can not be answered in a general way. It depends on the size and power consumption of the installation and how the LED strips are distributed in the room. If necessary. Is it necessary to use several power supplies and controllers but it is usually cheaper to work with one power supply and only one strong controller, as long as you can run cables everywhere. You are welcome to write us an email.
I would like to install 2 x12 watt outdoor lamps at 230 volt 3×1.5 is the cable, what length must not exceed this?
Hello mr. neumann,
the power is with 24 watt very low. With our online calculator for the cable cross-section, there is only 5% voltage drop at 9m, at 17m it is 10% (cable cross-section always 1.5mm²). Which voltage drop your lamp can handle, can be found in the data sheet. If there is nothing in it, I would rather stick to the max power consumption. 5% orientation.
I want to connect a pool underwater spotlight (12V LED / 16W). The supply line from the technical room to the terminal box is ca. 7 m long and made in 6.0 mm2.
Can I then work according to the above tool with a 0.5 mm2 cable at ca. 1,5m between headlight and terminal box?
Hello fred pop,
that is possible. In general it is of course never wrong to use thicker cross sections. So if necessary. 2 x 0,75mm² or even more. but in principle the 16 watt are so low, that also 0,5mm² are ok.
what to look for with CCT-strips?
what kind of cable should be installed (example 5x5m room)?
with CCT – i.e. tunable white – it is basically no different. The cable cross section must be able to handle the total power. With CCT there are 2 minus lines (one for warm white, one for cool white) and a common plus line. Most controllers control CCT in such a way that the brightness always remains the same when the color temperature changes. With a medium color temperature, therefore, warm and cool white leds are not driven with 100% each, but in the ratio 50 / 50 or 40 / 60 or 30 / 70 – depending on the selected color temperature.
A CCT-LED-band with a max. Power of 20 watts per meter will in reality hardly draw more than 10 watts per meter. Accordingly, the cable can be made thinner.
this rule is valid for MOST controllers, but NOT FOR ALL !!
As for the 5x5m space, it is best if you send a request through our configurator for indirect lighting:
I have a problem with 2 pool LED lights (30W each, 12V). the wire cross section is 1,5mm with a wire length of 17m.
Well i connect the power supply one lamp is burning bright, the other one has only 10 LED`s. Which possibilities do I have? The power supply delivers at the output 11,6V. Should I change it for a regulated one?
Thanks a lot
a 12V power supply should also deliver 12 volts. Coupled with the long cable length, at least one of the lights does not get enough voltage, as it seems.
With 60 watt you have 17% voltage drop on 17m here!
A high quality power supply also allows to regulate the voltage a bit above 12V, so that the loss over the cable length can be compensated.
thanks for your helpful homepage.
I have a similar question as michael, but a bit more detailed.
I have in different places in the house 24V LED strips RGBWCCT with 5 meters length and specified 12W/m. I could not measure this yet because of missing hardware.
Now I would like to place the, at best controllable, power supplies in the distribution box, also feed the controllers directly here and go from there to the respective strips. J-Y(st)Y 8x2x0,8 wires are installed. So these have a cross section of 0,5mm²
The cable lengths to the strips do not exceed 5 meters at any point. Mostly rather direction 3 meters.
Can I connect one wire per color and V+ in this constellation without having to worry that the current carrying capacity of the wires is no longer sufficient and that the wire will get too hot??
And your tip with the parallel laying of wires. But this does not improve the current carrying capacity of the individual wires, but only the voltage drop, correct?
Or would it still be mandatory to double the wire for V+??
I would then connect the strips best in the middle, so that the voltage drop and the current in the band are then evenly distributed.
Do you have a better recommendation or would you completely advise against it??
this all sounds uncritical. 5m with 12W/m results in the maximum case also only 60 watt. There is also still a 0.5mm² cross section for 5m cable length.
With the parallel installation, the current is divided into 2 lines. So the voltage drop is halved. That is what you want to achieve with it.
I want to install 7.35m long 5V RGBW (SK6812) at the top and bottom of the staircase handrail. In total I need for both sides 300W. Do I just use a 300W power supply, or should I split it into 2?? (will probably need 2 microcontrollers)
I plan to carry a cable and feed every 3-4m. With your calculator I come but even with 4mm² cable still on 43% voltage drop. Do I have to go to 6mm² here?
(to place more power supplies will be difficult)
Glad about every hint, I am still new in the topic.
300W at 5V sounds already quite heavy. That is easily 60 amps! But there are RS power supplies that can do this.
For the calculation you don’t have to take the total 300W, but only the power of the part you supply. You are feeding the voltage several times. I would use min. Feed every 2m. If I have understood correctly, you have then max. 40W on the 2m and then it works much better with the cable.
A thousand thanks for the quick reply!
If I understand this correctly, I would then have to carry a separate cable for each feed?
Can’t I just run a 5V cable (+neutral) from the power supply and solder the whole thing to each feed point in turn?? In this case the cable would carry the full 150 watt at least to the first power supply, right??
Correct. You would then need a very strong cable. It is more common to wire the feed points separately from the power supply / controller.
first of all thanks for your page here! Very well described and very informative!
I have a somewhat special situation and maybe you can answer my question, because I could not find anything so far.
I have a wall (ca.10-11m long) and small towers on it, which should be illuminated with RGBW bands under the cover.
Each of these towers gets 2 x 50cm LED band. After 2m comes the next tower and so on.. This results in a total length of approx. 20m, with many extensions. In sum 10x50cm RBGW and about 15m extension.
Can you tell me which cross section I should use for this?? Since every 2.5m again 50cm LED is in between comes, the loss is not much too high at the total length?
the cable calculation is not different in this case. You include connected power and cable length in the calculation. Assuming the last tower has 10 watt installed and the cable is 2,5m long. Then these are your values for the calculation. At the second last tower there are 2 x 10 watt and 2.5m cable, because this cable is already used to supply 2 towers. At the third last tower then 3 x 10 watt and 2,5m cable etc.
In addition, of course, all voltage drops must be added up. D.H. If you z.B. If you calculate 2% voltage drop on each cable, then the total voltage drop on the last of the 5 towers is already 5 x 2% = 10%. (or more precisely 100 – 0.98^5 = 90.4. So 9.6% voltage drop)
Many greetings, dennis
Cool site, thanks for that!
I think I understand everything, just would like to check that I’m not making a thinking error:
– indirect room lighting with 5700K high CRI afford as a daylight project
– 4 x 12V-reels à 5 meter, so 20 meter in total
– 20 watt each, so 400W in total.
– 4 power supplies (meanwell HLG 250) à 250W, adjustable from 10,8 to 13,2 V
1. I plan the power supply with one power supply per reel (so 5M à 100W), according to your calculator 4mm2 would be ideal as cable cross-section. I would like to refeed every meter from the same cable, otherwise the brightness will decrease a lot. This does not change the configuration of the cross section, or? If I would position the power supply in the middle under the strip and feed per side, I would only have to calculate with 2.5 meters, correct or thinking error? What would you recommend?
2. Stupid question: stranded or solid wire does not change the load capacity, only the cable flexibility, or? I still have old speaker cables with 2,5mm2
3. Theoretically 2 power supplies (instead of 4) would be enough to drive the bars, but I would need a bigger cable cross section and it would do the power supplies better to have buffers, or?
4. If I turn the power supplies to 13V, the power seems to get about 20-30% brighter (I am aware of the decreasing brightness perception). If the components are rated for the current at 12V and the heat is dissipated well, do you think it would be so bad to go to the 13.2? So this then actually greatly shortens the life of the LED? Isn’t it said that the semiconductor crystals themselves could theoretically become infinitely bright as long as the components can handle it and the heat dissipation is good?? The alu-strips are already oversized, but couldn’t it be that the leds also have a little power buffer?? Or would you strongly advise against it?
Best regards and thanks in advance
such extensive questions please send us an email. the comment section here is actually for more general questions. Short a few notes though at least:
Such circumferences (20m x 20W) if possible never realize with 12V but always with 24V LED strips. the required cable cross section becomes immense at 12V, as you can see. Otherwise, your ideas in point 1) are correct.
For soldering use only flexible stranded wires. For the rest it does not matter.
Power supplies always with min. 10% buffer. At 12V I would even min. 20 or 25% say.
If the 12V leds are operated with 13,2V, the lifetime will decrease significantly. At least halved, I would say. I definitely advise against it!
I have 7 meters of 24V LED strips. I feed once at the beginning.
Shall I calculate according to approx. 4 m new feed or would also be a feed at the end possible?
feeding at the end is also possible. Depending on the LED strip, even the one-sided feed at the beginning may be enough. especially if you have 24V LED-strips with built-in constant current sources (csq), like e.g.B. Our LK04-26b, then the 7m are also possible fed on one side.
We have when laying conduit in our house for the supply lines to LED (several bands) in several rooms always 1.5mm cable laid and wanted to use power supplies for top hat rails directly in the control cabinet. Now we were recommended all lines against 0.5mm to change, otherwise the leds would shine weaker. However, I read it here exactly the other way around. All leds are designed for 24V 30W power supplies. I am confused. What is correct?
by no means exchange in 0,5mm! This only increases the voltage drop and this significantly. Through a thin hose flows finally also less water, than through a thick one. To give you an example. Who recommends this??
Hi, big PRAISE!,
is there an extra guideline for cable laying in the house DC (distribution EG to leds EG resp. DG) => cable length> cross section?
Would it be z.B. In the house with 20m of conduction it is advisable to take a 5×1,5NYN to jew. 2lines with PLUS& minus?
Is it better to use hat rail power supplies or to install the portable power supplies close to the leds (selection/decision criterion)?
in general, the cable runs between power supplies and LED strips should be kept as short as possible, otherwise the low voltage here may. Correspondingly large cable cross-sections required.
Whether 2 x 1.5mm each for PLUS and MINUS are sufficient for 20m depends on the connected power. See our calculation tool for the voltage drop above.
DIN rail power supplies are not recommended, because they tend to make noise when LED controllers are connected downstream. Z.B. With SDR we had problems here. We use only the high quality HLG power supplies wherever possible.
first of all, thanks for the explanations, which made me think about the cable choice in the first place.
I plan to light a staircase with 5V WS2812B RGB LED stips (2 pieces a 5m). Per stage I use ca. 60cm strip section, with 16 steps a ca. 37 RGB leds and 600 RGB leds total. The right end of each strip section is connected to the left end of the next section via a three-armed cable, etc.. This gives me another 1m of three-wire return cable per stage to connect to the next section. In order to reduce the power drop, additional GND and +5V should be fed to each strip section (left). According to the manufacturer a 5m strip needs 95W at full brightness and all colors. So under full load would be 180W. A suitable switching power supply with 5v 40A is ordered (it has 3 outputs for GND and V+). Now the question:
which cable/cable cross-section should I use for the connection of the individual sections, and which for additional power supply per section??
if the 5V left are always fed separately, so there everything is connected in parallel directly to the power supply, there is not much power running through each cable. Always max. The 95W / 5 * 0.6 = 11,4 watt. You can use this value for the cable calculation. About the other feeds also no longer runs much. In principle, you can also omit them and just enter the data as a series.
Thanks for the helpful tool. What exactly do I have to enter? Voltage is clear. power is with my RGBW-strip 19.2 W/m (so 4.8 W/m/color). So for a 2 m strip I would have to enter 38.enter 4 W for the extreme case, right? And what is the length? If I run the 2 m strip on a 5 m supply line, I enter 7 m? Or is it only about the 5 m supply line?
The second question would be: if I want to use just described construction for stair lighting, z.B. For 5 stages, then the leads for each stage should all be the same length so that the stripes are all equally bright?
And the third and last question: if the cables come from the stages, then they have to be bundled on the controller. So you could lead all the wires that belong together into 5 wagon terminals and then have to go from there to the controller. Do you need a thicker cable for this distance, because the whole power goes over there?? There are 8 amperes, so at least 0.75 mm² or better 1 mm²?
Thank you and many greetings
only the cable lengths are valid. Length of the strip must not be added.
In the best case the leads are all the same length, but if the voltage drop is generally low, it does not matter much. Almost all our projects have different length cables.
If you combine cables and then bring them over only 1 cable to the controller, this should be a thick cable. You calculate it piece by piece. Over the single cables a certain voltage drops and over the common cable again (then with the total power). Add the two percentages of the voltage drops and the sum should not be more than 5%.
Hello I have a question, I have a power supply 5 volt 200 watt with 5 ampere.
I have built a panel with 4000 leds which cable from the power supply to the LED panel could I use it would be very nice if you could help me there I think this would also be an exceptional question for other members thank you for your answer with best wishes T.Meyer
Hello here is again P. Meyer of course the power supply has not 5 ampere but 40 ampere please excuse this addendum.
also you can calculate above with the tool. 5V, 200 watt and then the desired cable length. You will find out that even with only 1m cable length a thick 4mm² cable already means 7% voltage drop. 40A at 5V are just extremely much! This will then i.D.R. Also no longer made with only 1 cable but with many. So you can z.B. Put each 5 x 4mm² on PLUS and 5 x 4mm² on MINUS to realize at least 3m cable here.
Hello, I have to connect three ws2812b LED neomatrixes together, in total there are 768 LED’s! I have a power supply with 5V 50A and will then probably supply each matrix individually with power. With the power supply there are 3xv+ and 3xv-. Now my question: can I connect each matrix separately to the power supply, i.e. one cable for + and one for – to each matrix?? Or can you just connect the first matrix and last to the power supply and then connect the middle via the 3pin connectors DAT/GROUND/VCC with each other? Thanks
here supply each matrix individually with 5V. Loop only the data signal from matrix to matrix, but not the 5V. The voltage drop would be too high. Depending on the cable length there also necessarily very strong cables for the 5V between power supply and matrix use.
I would like to install a rgb lighting that consists of 2 m rgb each (approx. 60 led ) exists.
5x in a row and with about 2,5 m distance. The total length of the cables are up to the last 2m rgb strip about 20m.
I have now rgb cable 4×0.35 pulled in and it does not work properly. The first 2 led strips still go halay but also already with errors. The line from controller to led strip nr.1 is about 8m away already. The 3 is almost not correct nr.4 and 5 are on but only in a weak orange color. But without setting possibility.
Is this also due to the power supply or the cable cross section is too small??
It is operated with 2 controllers. The one is for led strip nr.1 and 2. The second is for nr.3/4/5. With the original power supplies that were included.
Thanks in advance.
Hello mr berner,
with which voltage do you work?
Let’s take only the last 2m section with 20m cable in front of it. I just assume that you use standard RGB-stripes with about 15W/m. Say up to 30W run there over the 20m cable.
When she does the above with 0.use 35mm² cross section in the tool, you get at 24V then 9% voltage drop – which is already very much. With 12V it is even 51! This is of course not possible. You definitely need stronger cables. At 12V times at least 2.5mm², better 4mm².
The calculation is simplified, because you have a row with 3 x 2m + 2 x 2m segments. You have to calculate per segment. 0.but 35mm² is certainly not enough – no matter how you calculate it.