Why does longer LED strips use less power?

Why does 5 meter of a LED strip consume less power per meter than 1 meter of the same strip?

Link to strip - Link to shop (Danish)

According to the information, the strip uses 6W/meter if 5 meters long and 11W/meter if 1 meter long. Is this caused by voltage drop over the length or what is the cause of this?

Thanks in advance :slight_smile:

Powered from one side? Then you will lose quite some voltage over the length of the strip. You probably can see a difference in brightness of the LEDs as well, if you take both sides.

11W is 0.92A at 12V supply. Those thin copper traces can carry maybe 2-3A, not the 4.6A for full brightness.

Add a separate power wire in parallel to the strip, connecting it halfway and at the other end. That should do the job. Use a 0.75mm2 or thicker wire.

Yes, it's the voltage drop... For most purposes we treat wire as having zero resistance but wire has a (small) [u]resistance[/u] related to the gauge/diameter and length. That gives you a (small) voltage drop depending on the current ([u]Ohm's Law[/u]) which results in less current (and less power).

That is a truly bizarre way to specify things!

Thanks for the answers, karma spread! :slight_smile:

I just do not understand how anyone would describe an unwanted voltage drop like that. The claimed "decreased wattage" on longer strips does not apply if the strip is powered properly and that may trick someone into using a too weak power supply which may end bad. Bizarre it is!