Chiroptera wrote:I have a ton (300' +) of LED lights. They are the old variety which look like strips of 3-4 lights on a plastic backing- some look like dominoes. Last year we covered our art cart in them and ran them off a 12 V deep cycle. This year we are doubling the amount of lights.
Oh, let's see. I'll guess there's about 4 LED's per foot, so with 600', that's 2,400 LED's. If they're just one color, figure they use about 20mA each at an average of, say, 3 volts, so that's 60mW each which is 0.06 watts * 2,400 = 144 watts. They probably just use a resistor to regulate from 12V which I'd say is about 75% efficient. 144 watts / 75% = 192 watts (e.g. 192 watts in * 75% efficiency = 144 watts out).
So the deep-cycle battery is probably something like 90 amp-hours, and you don't really want to run it past 25% capacity, so you can use about 68 amp-hours or so. At 12 volts, 68 amp-hours * 12 volts = 816 watt-hours. So your 192 watts of lights could run for 4 hours and 15 minutes.
If they're RGB color-changing LED's, then red, green, or blue is one emitter per LED, so that's the same at 192 watts = 4.25 hours. If you do a solid color like yellow (red+green), cyan (green+blue), or magenta (blue+red), then that's 384 watts so you only get 2.1 hours. And if you turn red, green, and blue all on, you get white but that's 576 watts or 1.4 hours.