I want to power 16 m of SK6812 RGBWW LED 5 V strips with 60 pixel/m. They are rated with 18 W/m which would make the maximum power ~300 W. I highly doubt that I will ever use the full power so, 200 W should be fine.

Still, that would mean running 40 A on one cable which sounds crazy to me. I am contemplating whether I use one power supply with 3-4 feed-ins to the strip, or two power supplies with 2-3 + 1 feed-ins. Two would make the cable management easier (because of doors and windows in the way). The two power supplies would cover different lengths.

I have 4 questions:

  1. Is it correct that I could use two 5 V 20 A power supplies instead of one 5 V 40 A in order to get 200 W?

  2. Could I combine a 5 V 13 A (for the shorter side) with a 5 V 30 A power supply, or do they need the same current?

  3. Would the combination of the two power supplies lead to less energy loss with the same wire thickness? If so, would that difference even matter since the second power supply will also add more loss?

  4. Can I minimize the energy loss if I inject power in smaller intervals?

Bonus: Are there any other ways to optimize for energy efficiency?

The setup would be wired something like this:

One power supply version:

One power supply version

Multiple power supply version (the first power supply would provide one feed-in, the second power supply would provide two or three feed-ins)

Multiple power supply version (the first power supply would provide one feed-in, the second power supply would provide two or three feed-ins)

EDIT: clarified some things in the text and added another picture.

  • \$\begingroup\$ Welcome! Zero chance of 16 meter worth of voltage drop at 5 V with only one side powered. If you do a search, there are plenty of images where the blue and white ones fade the longer you go along the strip as they have the highest forward voltage. How many shorter sections can you live with and feed-ins of power at those points? \$\endgroup\$
    – winny
    May 4, 2023 at 15:13
  • \$\begingroup\$ Thank you for your answer. I will ad as many feed-ins as necessary, regardless of using the 1 or 2 power supply solution. Can power consumption be decreased by adding more feed-ins than necessary? \$\endgroup\$ May 4, 2023 at 15:21
  • \$\begingroup\$ Not really. Also, it’s not given that two power supplies injected in two different places will play nicely. Granted, you have some resistance between them via the strip, but one will have ever so slightly higher output voltage than the other and depending on internal construction (synchronous rectification or not), will try to fight the other. I would try to get one honking large power supply and run a conduit along the strip. There are 12 V versions to avoid this very problem. \$\endgroup\$
    – winny
    May 4, 2023 at 18:19
  • \$\begingroup\$ Thank you very much. I am not sure I understand. Would the Voltage not be different at the injection point anyways because of the voltage drop? \$\endgroup\$ May 4, 2023 at 19:10
  • \$\begingroup\$ If you have two different 5 V supplies. They won’t have exactly the same output voltage. \$\endgroup\$
    – winny
    May 4, 2023 at 19:15

1 Answer 1


Your second diagram is what you want to do:

enter image description here

You have a common ground so the digital parts can talk to each other, but you have no circuit between the individual power supplies, so they act like they're not even connected. You're also limiting the current in each part of the system, so you're less likely to start an electrical fire if there is a short circuit.

You can split them up however you like. Each strip is acting as if it was independent of the others, so if you can have 1 big and 1 small, 2 equal sized, or however many you want. Just make sure each power supply can power the number of LEDs you have connected.

As mentioned, you will of course need to regularly reconnect power as the copper on flex strips is equal to maybe 24 AWG, and so can carry only a few amps without huge loss of voltage. So run a suitable gauge wire behind the strip and connect at regular intervals, breaking in the middle so that it doesn't join the two power supply plus terminals. This will actually cause your strips to use more power (because they'll all light up) but it is what you need to do.

  • \$\begingroup\$ It's worth ensuring that the V- lines of the two power supplies are solidly connected to each other, rather than relying on the ground line of the LED strips. \$\endgroup\$
    – Simon B
    May 5, 2023 at 9:21
  • \$\begingroup\$ It won't hurt, but no current will flow between the supply grounds and if the strip ground is severed the LED strips are probably trash anyway. \$\endgroup\$ May 5, 2023 at 12:28
  • \$\begingroup\$ Thank you very much! Your comment is very helpful and reassuring. I feel ready to do it now. \$\endgroup\$ May 5, 2023 at 14:53

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