A question for the electrical whizzes

Perplexed

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So I have eight outdoor Christmas ornaments, in the form of chicken wire bent and shaped into spheres about 2 feet in diameter, each of which is wrapped with a strand of LED lights. The strands are all the same, except four are red and four are green. They have their own solar panel about five by five inches, and a battery recharged from the panel. I have them hanging from the branches of a pair of trees out front, with the panels all facing south.

I’ve noticed that if it’s cloudy out, the red-lit spheres will be lit for several hours, then they’ll fade. The green-lit spheres, on the other hand, last all night, though they’re pretty dim by morning. If it’s sunny all day, all eight spheres remain lit all night.

Why do the green LEDs last that much longer than the red LEDs? I know red has a longer wavelength and lower frequency compared to green, so its energy is lower than that of green LED’s. That would lead me to think the green LEDs would drain the battery faster, but this hasn’t been my experience with the LED strands I have. I’m guessing that there’s a resistor in the circuit that has a greater value to restrict the flow of electricity more through the red LED strands, and a resister of lesser value in the green LED strands, hence there’s more of a drain on the battery in the red LED strands.

What say you?
 

Catt57

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So I have eight outdoor Christmas ornaments, in the form of chicken wire bent and shaped into spheres about 2 feet in diameter, each of which is wrapped with a strand of LED lights. The strands are all the same, except four are red and four are green. They have their own solar panel about five by five inches, and a battery recharged from the panel. I have them hanging from the branches of a pair of trees out front, with the panels all facing south.

I’ve noticed that if it’s cloudy out, the red-lit spheres will be lit for several hours, then they’ll fade. The green-lit spheres, on the other hand, last all night, though they’re pretty dim by morning. If it’s sunny all day, all eight spheres remain lit all night.

Why do the green LEDs last that much longer than the red LEDs? I know red has a longer wavelength and lower frequency compared to green, so its energy is lower than that of green LED’s. That would lead me to think the green LEDs would drain the battery faster, but this hasn’t been my experience with the LED strands I have. I’m guessing that there’s a resistor in the circuit that has a greater value to restrict the flow of electricity more through the red LED strands, and a resister of lesser value in the green LED strands, hence there’s more of a drain on the battery in the red LED strands.

What say you?

Due to the physics of the LED, different colored LEDs have different "forward voltage"s (a primary characteristic of an LED). This site's LED color chart gives the forward voltages for their LEDs, but it does really depend on the LED in question. In general, the higher in frequency light an LED makes (the bluer it is), the higher the forward voltage. Often, a red LED's forward voltage is ~2V, a green one ~3V, and a blue one is ~3.4V, but it really does depend on the LED manufacturer and the exact frequency of the light emitted.
 
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GeneW

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I'd look at the batteries. A lot of those solar rechargeables uses what appears to be the same size as AA or AAA batteries, but they are made in different milliamp ratings. You might be able to upgrade the batteries just by buying some with a higher capacity. Or the weaker one might have one or more weak cells/batteries. They can certainly be replaced.
 

Glock 40

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Yes the higher voltage would pull more watts if the source of power is equal. Have you tried swapping batteries or solar setups between colors? I would figure you have one battery that holds more mAh than the other or one setup doesn't charge as good as the other. Do you know what type of batteries are in the solar panels? Chinese cells are notorious for being crap and having large variance in capacity.
 

Catt57

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Wouldn’t this mean the green LEDs fade faster than the red, which is the opposite of what I see in the strands I have?

Typically. But if you look at the 2 items I point out on this chart you'll see that these 2 in particular the Red draws more voltage then the green. And again, it really does depend on the LED manufacturer.

And GeneW and Neckbeard are also correct. Odds are the batteries and solar panels are not quite equal. Different colors are probably different assembly lines, and different batches of components.

upload_2020-12-3_17-50-10.png
 
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Perplexed

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I’d have to crack open the housings to get to the batteries, so it’s not really a big deal. I was just curious; if it had been one or two of the one color lasting longer, I’d have passed it off as variances in battery manufacture. But, all four green last longer than all four red, by at least a factor of three, which got me wondering. Thanks for the input, folks.
 

MacFromOK

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LEDs of any color can have much different specs, so it depends on which specific LEDs were used. The circuitry powering them may be different for different specs, which may or may not vary by color. Also, different spec LEDs used on the same circuitry likely won't have the same battery life.

It all depends on how the manufacturer combined which components on the different assemblies. The amount of current used matters more than voltage regarding battery life.
:drunk2:
 
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