Does the strength of solar lights decrease with distance? How far lights can be from panel without power loss?
I have three solar spot lights, each connected to ONE approx 4in x 4 in solar cell panel with 20ft. plastic covered wires. Will the current decrease if the lights are attached with 40ft wires? How far can I place the lights without weakening the flow of power? Will the wires withstand 45 C sun? Can the wires be replaced with any other kind that would stand higher sun temperature for 3 months? Can’t replace anything except wires where I am.

Yes. If you are talking about solar tube light systems, then the light does decrease the further away you get. With solar light transmitted through fiber optic cables, the light decreases in relation to the length of the fiber optic cables.
But maybe I misunderstood your question. If you have a solar photovoltaic panel that collects energy form the sun and then runs that electricity through a wire to a spotlight, then no, the light strength would not decrease with the distance of the wires. These solar spot lights are commercially available in lots of stores for less than $100 and ofter have different length wires or cables available as options.
The question of whether the wires will withstand hot temperatures is best answered by the specific manufacturer of your wires. Generally speaking, they should be fine, even on a hot day.
Note that if you replace the wires, you may void any warranties that came with the light system from the original manufacturer.
huh, I can’t quite understand your question. What are solar lights? solar panels are designed to be illuminated by the sun.
But any lights shining on a solar panel will produce some output, and that output depends on the brightness of the light. The brightness of the light depends on many factors, one of which is how well it is focused on the panel. With good reflectors, mirrors, lenses, etc, you can move the lights away and still maintain most of the light on the panels. In theory you can keep moving them away as long as your reflector gets better focused. In practice, I doubt you can move much more that 10 ft away with ordinary reflectors.
Wires? do you mean the wires to the lamps? with heavy enough wire, you can move them as far away as you want – that will not be the limiting factor. Size needed depends on the wattage rating on the lights, and the distance. Look up any of numerous wire calculation web sites, or use wire tables. The reference has one.
Most wire can easily withstand 45 C. It’s easy to get wire that will handle 65 C or higher. Just look at the temperature rating on the wire. PTFE (teflon) insulated wire, for example, is rated to 200 C.
Sample wire calculation. If the 3 lamps are 100 watts each, at 120 VAC, then the current is 300/120 = 2.5 amps. If you want a max of 5 volts drop, 2.5 for each wire, that is a resistance of 2.5/2.5 = 1 ohm. Using the wire tables, for 50 ft, #22 wire is 16 ohms per 1000ft, or 0.8 ohms for 50 ft. #22 is a small wire!
Another sample, 1500 watts total, just scale the above by 5, need 0.2 ohms. #14 is 2.5 ohms/1000 ft or 0.125 ohms. #14 is what is used in much house wiring.
I hope you don’t think you can get more power out of this than you put in. It depends on the type of light, but at best you will get 20% from the light and 20% from the array. so if you can get all the light from the lamps to shine on the arrays, you will get 0.2*0.2 or 0.04 or 4% out. Put in 1000 watts, get out 40 watts at best.
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