How Many Watts for a Strand of Christmas Lights?

[jerry i h]

I have a 60 LED strand of C6's that, according to the included instructions, takes only 5 watts. I also have a 70 mini-incan strand that seems to be 3.5 volts and 0.4 watts, so total usage is 70x0.4=28 watts.
Does this seem feasible? I only ask because these beasties are all made-in-China, so who knows if the "instructions" are correct. I would like to have holiday lights that are minimally abuse of the electric grid. Any thoughts or opinions would be greatly appreciated.

 

[65535]

It's time for Halloween not Xmas...

Hook it up to a Watt meter or even an Ammeter on a DMM.

Most 3mm LEDS (about the size that are in those Xmas lights) are about .5watts a piece so you're looking at 30 or so watts a strand.

Most websites seem to state around 5 watts or so. It would be interesting to know.

I have a DMM so if someone sends me a strand I'll test and send back, but that would cost about $10.

 

[J_C]

I beg to differ, most 3 to 5mm encapsulated LEDs are 100mW, (~30mA max with good heatsinking (short leads to large copper surface area on PCB), more like 20mA max for long life). 60 LED x 100mW = 6W, 5W/60 = 83mW, so yes 5W seems not only realistic, it also seems to be driving them too hard for best life with only encased wires to 'sink away heat. On the other hand, someone making Christmas lights is using a shedload of LEDs, with that quantity they could easily persuade some manufacturer to make a slightly more robust LED that withstands 83mW long term, it would only require the cathode lead be slightly larger but I doubt they would, an inline resistor would be cheaper and they don't expect you'll use Christmas lights 24/7/365 a year so the lifespan is extended over time. Made in China, even if the LEDs themselves are, would at most tend to mean lower lumens/W and maybe thinner wire to make it cheaper, while sometimes specs are just plain wrong it is as easy to make a 5W strand of LEDs in China as anywhere else.

 

[Lynx_Arc]

most 3 or 5mm LEDs are 10-20ma at 3.5v or about 0.07watts nowhere near half a watt so a whole string of 100 would be about 7 watts while even the small incan bulbs are 80-200ma each or 4 to 10 times the power if at the same voltage as voltages differ on them vastly depending on how many in the string and how many strings (in parallel) to the plug.