Solar LED string lights too dim. Can I add another solar panel?


I bought two strings of solar LED christmas lights this year.   They don't get as bright as the plug-in LED lights I see around the neighborhood.  What I'm wondering is if it's possible to take some other cheap solar lighting fixture for the yard, and add the extra solar panels to my LED setup to give the batteries a better charge.

While I was rewiring stuff, I'd also probably want to make the lead cord to the solar panel a bit longer so I had more flexibility about where I put the panels for optimal sunlight exposure.  I'm totally new to wiring adventures, so I don't know what would be needed to make sure all of this would be weatherproof.

 I've searched here, and could not find an instructable on this topic.  Looking forward to seeing one added, or being directed to one if it already exists!

-Alison

sort by: active | newest | oldest
crapflinger7 years ago
are the lights you have any thing similar to these ? we got a few sets of these from target last year and they are really dim but i think it's because they're REALLY small LEDs....something in the 1mm range or something. they almost look like surface mounts. i can't find any specific specifications on the LEDs themselves though.
Oh, man, those are crap (is that why you're flinging them at us? :-D). I sure hope that's not what the OP has. Can't be modified or improved :-( Start with tiny surface mount LEDs, then put nice thick translucent color filters on top, so even less light actually makes it out.
Kiteman7 years ago
Rather than add a panel, add LEDs - solder one in parallel with the existing LED.

Just connect them leg0to0leg, making sure you have them both the same way round (look for the flat edge on one side of the LED).

They won't stay lit for as long, but they will be much brighter.
overboardgirl (author)  Kiteman7 years ago
Wow. I've been reading up a little bit on the web about how to make stuff with LEDs, and I must really not understand them at all! Why would that make them brighter?

(It's fine with me if they don't run all night long - until midnight would probably be great).

Can anyone direct me to some good resources for how to learn some basic EE? I don't even own a soldering iron, much less know how to use it (though I've heard it's not hard - I just don't know anything about the principles of the matter).
It won't make any individual LED brighter, but if you have twice as many (for example), you will get twice as much light out in total.

For learning electronics, many people have already asked that question here and elsewhere. In the search box for Instructables, try typing "learn electronics" and see what comes up. You can limit the search to just the Answers section by adding "inurl:answers" to the search, or limit it to just Forum topics with "inurl:community".
overboardgirl (author)  kelseymh7 years ago
Hmm. Well, I already bought two sets to double the number of lights. For a second there, I thought Kiteman was saying that if I took both strings and hooked them up in parallel to just one solar panel, it would, for some reason, make all the lights brighter. That's not making sense to me.

I'm not looking for overall light output (I'm not trying to read by these) I want each light to shine more intensely for overall effect. These are christmas lights, strung over my entry gate. Sure, I could buy a couple more strings, but they'd be just as dim and lame-looking as the first two, I'd imagine, with these short, cloudy winter days.

I will definitely check out Instructables specifically for learning tips.

Thanks!
You're exactly right that hooking up more lights to the same solar charger system (not just the panel, the panel plus battery and associated little charging circuit) would not make each light brighter :-)

With normal low-voltage LEDs, you aren't going to be able to do that at all, unfortunately. LEDs aren't like incandescent bulbs -- when you give them enough voltage, they turn on full, and draw just enough current to power the light output. If you raise the voltage (add batteries, or put more solar panels in series), they'll brighten somewhat, but not extensively. With too much voltage (or reverse bias), they'll break down (burn out).

To change the brightness of LEDs, what people have to do is "flicker" them, using electronics to turn them on and off faster than your eye can detect. Do a web or Instructables search on "PWM" or "pulse wave modulation" to see more of what I'm describing.

I'm sorry to say it, but I suspect that you may need to get LEDs you can plug into an outlet, if you want something bright in a Northern hemisphere winter :-/ However, we have a lot of electronics experts around here, and one of them may have a good idea to help you.
overboardgirl (author)  kelseymh7 years ago
So you're suggesting that these LEDs are deliberately gimped to be lower output than normal plug-in ones? You could do that with the resistor right? Or rather that they are a type which is simply not capable of emitting very much light (presumably chosen to make them last on the limited battery power? I thought LEDs didn't use up that much electricity...).

I know that there are "normal" and "high intensity" LEDs, but I wouldn't have thought that christmas lights would need to be "high intensity". But maybe they are. I can't see any use for these "normal" lights if this is all the light they're capable of, but I guess they have their applications...

Is there a way to test whether they're working up to their potential? Because if this is how bright they were designed to be then they're a bit of a rip-off. Definitely lower output than I think most people would expect from string-lights... Is there some indicator on the bulb, or a way I can test them?

I don't want to just overpower them and burn them out. (The too-much voltage thing is why they need the proper resistor, right?) Sorry for all the noob questions here. Thanks for all your explanations!
Oh, no. Different LEDs are manufactured with different voltage and current requirements. For example, the LEDs used in car lights and traffic signals use higher voltage and current than LEDs in a flashlight.

My suspicion is that your solar panel is putting out voltage toward the low end of the LED's operating range, so you're getting minimal light. One way to test that would be to bring the solar panel indoors and illuminate it with something bright, then compare the brightness of the LEDs. You'll probably need to put the panel and light source in a box or something.

Sometimes the LEDs have part numbers or other indicators stamped on them, but it really depends.

You're asking lots of good questions! Unlike some newbies who think they already know everything ;->