Introduction: Make Your Own Solar Powered Led String Lights. ($5 Bucks Max)

Picture of Make Your Own Solar Powered Led String Lights.  ($5 Bucks Max)

  Making a basic solar powered string of led lights isn't too difficult.  This instructable will require no electronics knowledge and no programing. 
  What were will be doing is upgrading some old battery powered mini lights to LEDs and then using some basic components, charging the batteries with a small solar panel.  With the aid on 1 IC and 1 inductor, we can automate the string so it turns off and charges during the day and turns on at night. 
Let's get started.

Step 1: Let's See What We Need to Get Started.

Step 2: What We Will Need.

Picture of What We Will Need.

I'll tell you what I used, but you can improvise your own parts.

1 Battery powered light set with battery box.
1 Solar Panel 2.0v @ 80mA (I'm using two 1.2v NiMHs in parallel. If you want to use one -then you need 2v @ > 20mA.
1 IC (QX5251F) Will discuss this one later on
1 Inductor 220uF (This is not exact and you can change it to meet your desires.)
10 LED's (White, Blue, Green or Pink) (Red and Yellow are a little different, but you can use them if you really want.)

A soldering iron.
Wire Cutter

Step 3: Let's Make an LED String.

Picture of Let's Make an LED String.

You don't have to make your own string.  You can buy battery powered LED string on Ebay for about $2 - $4 depending on the number of LEDs.  Then you can just hack the battery box which you'll see in a few steps. 
If you have an old Christmas string mini lights, they need to be Battery Operated.  If you use AC powered ones, the wiring is not in parallel.  You can cut up the AC strings and rewire them in parallel, or you can just get two long wires and solder on the LEDs. 

Anyway here is a close up of the prep.

Step 4: Let's Start Putting the Circuit Together.

Picture of Let's Start Putting the Circuit Together.

These are the connections we will need to make to properly have our circuit turn on and off automatically as well as properly charge the batteries and power the lights. 

This is the entire layout.  You can add 15 leds per QX5251F @ 20mAh per LED.  The max current for the QX5251F is 300mA so you can play with different configurations.

I purchased my QX5251F from a vendor for $20 for 100pcs.  He'll sell as little as 10pcs, but the shipping is still $9 plus $2 for paypal.
Here is the vendors contact info.
If someone just really wants one or two, contact me and we'll see if we can work something out through paypal or something.

Here's the secret.  You might be able to scavenge the entire circuit from any Chinese made solar lawn lamp.  US ones use about a dozen different components, but I guess you could use that too.

Step 5: Working on the Housing Connections.

Picture of Working on the Housing Connections.

A few soldering points and we are almost done.  So let's put it all together.

Step 6: That's It.

Picture of That's It.

That it.  I've tested this set up with two 1000mAh (The real capacity) and they ran all night.  If you use a real 2000mAh battery you can obviously just use one.  Just keep in mind that max output of your solar panel.  If your solar panel can only put out 20mAh, in 8 hours of sunlight you'll only be able to charge your battery(ies) with 160mA so that's what it can put out.  That's only enough to power 8 LEDs for about 1 hour at Full power.  The circuit uses only a fraction, about 5ma per LED.  Also you can't use the complete capacity of the battery.  The QX5251F can use about 35%.  It won't take the batteries down past 0.8volts.


rcisneros (author)2010-10-20

String of lights - $2 new (Second-hand was $0.25)
Solar panel - $1.5 off ebay.
QX5251F (IC) - $0.20
Inductor 220uF- $0.02
Battery(ies) - $0.50 x 2 = $1

> $5

I am very interested in building one of these but I have some questions as I do not know what I am doing. can you email me at

and I can give you my number or I can call you if possible.

radcock (author)2017-08-23

Does it matter if my solar panel o/p voltage is 5v? I wanted to have the 5V panel charge 2 1.2V batteries in parallel, giving a long 'light' time to my bulbs. Would this be okay doing the same configuration?

The real Hellhound (author)2017-03-21

i then found out the bulb was 20 years old!

The real Hellhound (author)2017-03-21

i made this and it blew up giving me a second degree burn on my hand

ninadt23 (author)2016-03-01

Please give me details of this ic QX5251F to buy this.

Tempest2 (author)2016-03-01

I am wanting to do this with a reel of LED lights from eBay.

LED Chip Model: SMD 3528
Beam angle(°): 120°
Input Voltage: DC 12V
LED Quantity: 300 leds/5 Meter
Working Current/meter: 0.35-0.4A
Output power: 21-24W /5 Meter

Would this set up work for this? Unsure how to figure how big of solar panel? Would like to run Dusk to dawn....
Can you help?

barsam (author)2016-01-01

I have now a more explicit question. If I have about 33 tiny lights on a string, how big a solar panel do I need???

barsam (author)2016-01-01

I am not able to find a solar panel on Ebay. I am finding only rather expensive panels for i-phones. what term should I look for in the search engine of Ebay or Amazon??

KarlaE1 (author)2015-09-20

can I use battery filament lights from IKEA ? They look like LED but are hard wired (can't replace burned outs).

RigoC (author)KarlaE12015-09-21

I'm not sure. If they require 3.1v - 3.4v, then I'd say yes. If they are not LEDs, they will use up a lot of energy and run only for a short time.

Good Luck.

leredmon (author)2015-07-25

I need two to four "twinkling" lights that are solar powered via a cord approximately 5' long. I will be putting the lights under glass in one location, but need the solar cell placed away from the glass/lights. Is this something I could purchase from you?

rcisneros (author)leredmon2015-08-05

I'd love to but is not really worth it anymore. You can now go to a dollar store and but a cheap solar light for $1 or so. Rip it open and The components will all be there.

nguyen603 (author)2015-05-13

Where do I buy the materials for the light? Thanks.

amajo37 (author)2014-12-05

i have string lights but i wish to longer the wires to put them on the roof to get more light, can you help pls

amajo37 (author)2014-12-05

i have string lights but i wish to longer the wires to put them on the roof to get more light, can you help pls

Lanoma (author)2014-11-11

I put new batteries in my solar lights. They don't switch off when exposed to light and the battery dies after a few hours. batteries were 1.2 400mah replaced with 1.2 1800 mah. Can you help. Terminals are touchy too how can I fix this?

rickvanderzwet (author)2013-07-25

The inductor is 220uH (uF is used for capacitors).

pjapardy-barnett (author)2013-02-13

Is it possible to buy 5 sets (blue, yellow, red, green, pink) from you? I need them to light up my fairy houses please.

clazman (author)2012-09-13

I have a question that doesn't pertain to this Instructable so I don't know if I should ask it.

Can the QX5251 be destroyed if the battery was to be placed in backwards?

One of my lights quit working and the LED is still good.

Rather than trying to fix this module I found a circuit on the internet that uses a 3906 transistor, 4007 diode and two resistors (47K for the base and a 47 ohm between the collector and LED. It does not use an inductor. I still can't get this circuit to work. I've compared it many times to the one I found.

iApple guy (author)2012-03-26

Just made mine for under $2 my own way. It works with glass pannels, and it looks COMPLEATLY different. Instructable coming soon!

rcisneros (author)iApple guy2012-03-28


iApple guy (author)2012-03-26

I started to think about this project again just today, and I figured out how to make this with glass pannels. I will make the instructable soon, well actually today so come check it out. It will not be up til later today, I still need to make it!

aalnizzo (author)2011-12-16

Couldnt find that LED driver chip anywhere.
Got these ...
instead. Because of this and your diagram here I think I got an idea of how to wire it right but not 100%. With this chip instead of the one you have here, a) my wiring below should work right? (on my chip) (see pic).

Will this charge bat? and keep the solar cell from draining power?

rcisneros (author)aalnizzo2011-12-16

Never mind the second diagram shows the Zener internal, so everything looks good. Your set. Good luck.

Mine don't blow up if you mess the wires, so hopefully yours don't either.

aalnizzo (author)rcisneros2011-12-17

Thanks! Appreciate it. Yeah this chip is freaking tiny!. Wound up having to solder solar tabbing to the connections super carefully to have something to solder the wiring to. Seriously didnt think they would be this small, like a mm, by two mms, with three connections on the one side. Talk about a challenge to solder. Building them now, will be glad to see then working soon!

rcisneros (author)aalnizzo2011-12-17

That does sound like a challenge. The advantage is your chip is rated to a much higher voltage so there should be nothing stopping you from trying to use lithium batteries and a 1w LED. Please post your final results. I'd love to see them.

rcisneros (author)aalnizzo2011-12-16

From the pdf white paper I think so. Looks like the same setup except that these Zetex people like to use strange terms.

From draining, I'm not sure. The IC I used says it has an internal blocking diode. This one says DIODE array, which seems to be where you would put the inductor, but you might need a blocking diode. You can get them anywhere for 1 cent or so.

BTW nice job on finding a substituion.

iApple guy (author)2011-09-02

I took my LED solar lights apart, and now they aren't working. I tried soldering them, and maybe I melted the wire connections (as seen in photo). These were some different looking solar panels on some landscape lights I bought at Wal-Mart. Can somebody give me some advice?

rcisneros (author)iApple guy2011-09-03

These look like glass panels. You really can't solder them. They have to be glued. There is a special conductive glue, but it isn't cheap. The panels themselves tend to be a bit more efficient in my experience, but the leads are fragile. I have two sitting on my shelf like this (broken). I'm waiting to have a real need to buy the conductive glue.

iApple guy (author)rcisneros2011-09-03

yes they are glass panels

rcisneros (author)iApple guy2011-09-03

Oh and fair warning. If you try to solder them, you could melt the panel near the conductor on the inside of the glass. After that, there is no simple way of fixing it. You could try to stick needles in the sides to pierce it, but most likely it will just shatter the panel. It might still work if all you break is the glass though. If it's not working, what do you have to lose. Just beware of flying glass.

trknjim (author)2011-07-23

Is the 220uf inductor a capacitor or are you using a 220 ohm resisitor? I didn't see a schematic, just a diagram mock for the components. Pretty sweet a simple... I like it !!!

trknjim (author)trknjim2011-07-23

Thanks for the fast reply. Do you have the inductors and the ICs for sale? I found numerous inductors and in different values, BUT STILL CAN'T LOCATE the QX5251F IC. Seems to be a proprietary component !!!

rcisneros (author)trknjim2011-07-24

Inductors are everywhere. The values don't have to be exact. You can look at the chart I posted on this page.
The QX IC is prop, but there are alternatives. You can rip one out of a cheap made in china solar led lamp. You just can't be sure of the quality of the IC, but that may not be a big deal for you.
If you really want and the QX, send me a pm and we can work something out.

rcisneros (author)trknjim2011-07-23

No resistors required. Just 1 inductor. The list of components is on the first real page.

rcisneros (author)2011-01-05

These are some of the inductor values you can use. As you see, if you change the inductor value you will use more energy, but that will give you more brightness.

shanakoenig (author)rcisneros2011-07-12

Thanks! I am actually working with a cheap solar light currently (in quantity purchased for about $2 each). I have been reading some basic electronic books, tons of instructables and the comments and going through the overunity joule thief forum. I have learned a lot but have come onto a few basic stumbling blocks I would love any advice on.

Basic goal:
Build an efficient circuit that can run a large LED array at 3.4 volts 20 ma per LED (full brightness). I would love to be able to do between 10 and 30 on a single circuit, but I can always do 2 circuits if it is more efficient that a single circuit. Obviously I know the more leds I use the big the solar panel I will need and larger battery capacity.

Set up:
When I take apart my basic cheap solar light I can only run 1 or 2 color changing led well off the current circuit, if I add a third LED they start to flicker. I currently have modified a few to run 2 LEDs or 3 with some flickering and they will run all night on a full charge with a cheap 600 mah recharable battery.
This circuit runs at about (it varies up and down) 13 ma and with 1 led the volts across it measure about 2.3, with 2 leds about 2.1 each.

This is way to dim, based on an instrucitble or a comment on one, someone tried adding a second battery in series to boost the voltage. I tried this and it worked great I found the best results before the leds get dimmer then I want is 6. I can add more and the circuit only draws slightly more power, but the leds get dimmer then I want, I have tried up to 17, but really 6-8 is best. Below is a chart of the approximate ma and volts (measured across each led) that is draw for different number of LEDs (all color changing or white rate 3.4-3.6 volts and 20 ma).

1 LED = 60 ma / 3.6-5 volts (varies up and down)
2 LED = 98 / 3.3 - 4.4
3 LED = 103 / 3.1 - 3.6
4 LED = 106/ 3 -3.3
5 LED = 108 / 2.9 - 3.2
6 LED = 112 / 2.7 -3.1
10 LED = 120 / 2.7 - 2.9
17 LED = 122 / 2.4 - 2.6

This was all tested on fully charged batteries and the batteries dies the voltage drops.

This seems to drain my batteries MUCH faster than it should. With a 6 LED array it should consume about 340 ma per hour, so if I wanted it to last 10 hours that would be 3400 ma. (I have other solar panels that I plan to swap out to provide enough power). I thought that two 3000 ma batteries would last at least 7 hours even taking into account i can only use the first 80% before the voltage drops too low. However my lights dies after only a few hours!

I read your comment on one of BrownDog's instrutables about no name rechargeable batteries and figured that that may be the problem. So I added two more 3000 ma batteries in parallel, for a total of 2.4 volt 6,000 ma battery pack. This lasts on full for brightness for 5 hours and then gets dimmer over the next 3 hours until it dies. I really want my lights to last at least 10 hours, this is 3400 ma. If only 50% of my battery is good and I can only really use 80% of that, does it mean I REALLY only have 2400? How do you test the batteries to see how much they really hold? I have tested with my millimeter after I have charged them and I get about 1.4 unloaded so I assumed they were fully charged to 3000 ma.

What I would love to know is how you are able to light 10 led off two1.2 volt batteries in series with 2000 ma all night?

By doubling the input voltage am I reducing the efficiency of the circuit?

I have attached pictures of my set up, circuit and a close up of the IC. Would you recommend changing the inductor to up the current, as add my batteries only in series to give longer life and not extra voltage (also more solar panels)? What do you think would be more efficient?

rcisneros (author)shanakoenig2011-07-12

The one thing that you could use is oscillation. Most people can't see the blinking over 50 -60khz. The IC used, which is very similar to yours, except yours seems adapted for color lights, it does that as part of it's function. That's why if you put in a blinking LED to a normal solar light it will only be red. In reality it's turning on and off really fast, but the first color is always red. Your circuit there is made to over come that and keep a charge in the circuit so the LED can go through colors. If you replace that with a white LED, it's always on so it uses more energy then and a blinking led which is off some of the time. If you remove the IC and re-wire it without the capacitor and diode, you might get better battery life.

As for your batteries. There is no such thing as a 3000mAh battery so I'm guessing if you test them you'd find something like 1000mAh, if you're lucky. Also, you can't use all the power in a battery. That is to say it's not going to go zero. When it's 'drained' it will probably have a charge of .8v or .9v. That's like 50%. So your math of 6000 is really more like 1000mAh. SUCKS huh? Stick to name brands. They are actually cheaper in the long run.
BTW, 1000mAh is huge for solar lights and should last you days.

That IC might have a limit V. The QX claims a limit of 1.9v, but I've tested it as high as 3.4. That doesn't mean it won't burn out in a day or so.

I sugguest your really remove the diode and cap from your circuit and then try like 3 leds. Then double it. Then test and then double it. The inductor I used limited me to 10 leds. Not the brightest. If you want more you'll need a different inductor, but you'll have to experiment with your IC. Good luck.

shanakoenig (author)rcisneros2011-07-12

Thanks for the info! I am actually using color changing lights, mostly at least with a few white LEDs thrown in, so I probably need to since with the circuit as is. I have actually run it for the equivalent of several days and all the circuits seem good on 2 batteries, I tired with 3 at one time and quickly fried a circuit so that is the limit.

Based on what you said I need to leave the circuit as is. If I don't remove my capaciotr and diode, but change my inductor to 33uh or 20uh instead or the 47uh that is currently in there will I still be able to up the current? If so and my IC can handle it that would be a great way to get a few more LEDs at full brightness.

**Small note on my battery use, I am trying to power between 10-20 LEDs in a single array at full brightness to light up some fiber optics. This would last for days for a normal light, but these are huge sculptures several feet across. i am stressing the filaments and I need very bright light for it to leaks from all the stress points the way I want. I have tested this with a single high brightness 3.4 volt 20 LED that is powered by a 4.5v battery pack and it looks amazing. I want to get my solar powered lights up to that level and have them last all night. :)

rcisneros (author)shanakoenig2011-07-13

Sounds like you have a plan. I wish I could find an IC that did what this one does for lithium batteries. Replacing a 20ma LED with 1W LED is a hugh difference. Even if it only ran half the night it would rock. Unfortunately all the circuits I've seen use up a lot of the battery power or require a bunch of components which makes it way more complicated.

Good Luck and post a pic when you get it fired up.

shanakoenig (author)rcisneros2011-07-16

Well it didn't work, it no longer turns off in the light. I am pretty sure since I doubled my battery voltage the amount of power coming from the solar cells in no longer greater than what is coming from the batteries so it doesn't switch the circuit inside the IC.

*****Have you tried your circuit with 2 batteries? *****

I have tried changing my inductor on my circuit but I assume it barely makes a difference since the capacitor(which I need for my color changing LEDs) is limiting the final output voltage. Right now there is a ceramic disc capacitor with 104 on it, based on similar images I have found on the web I assume this is .1uF 50VDC cap.

Currently my unmodified circuit uses a 47 uf inductor, a mystery IC circuit, a IN5819 Diode and a .1 uF capacitor. With that 1 battery and 1 color changing LED the circuit draws about 13 ma from the battery and about 3.5 ma and 2.8 to 5 volts to the LED.

*****Where did you get your induction to amps chart? Is this from your own tests? *****

My amp output based on induction input is very different from yours. What is the best way to test? Trial or is there a formula I can use? Based on your info I think a 22 uF inductor could double my amps. Then should I double my capacitor size to .2uF. If I get a much bigger capacitor like .5 uF would this still work and just give me more headroom to go a 10 uF inductor? Would this decrease the circuit effiency?

Thanks in advance for all your help! I am really new electronics and circuits, I have 10 + awesome sculptures I am trying to get lit right and every time I think I finally got things working I hit one more road block. :(

rcisneros (author)shanakoenig2011-07-17

The inductor chart is from the MFG of my IC so your results could match your IC or not.

I don't believe changing the capacitor will make a difference in the efficiency, but it might change the behavior of your circuit, but I don't think so for you. If you needed a bigger capacitor, my guess is that your leds would always be red. The capacitor is only there to keep a charge on the led so it cycles through the colors.

Assuming your IC works the same as mine, it doesn't work like you think. The IC has a built in light switch. Very simply, when the solar cell puts out any juice the switch trips. Whether there is enough charge from the solar doesn't matter to the switch.

Are you sure it's not burnt out?

You might have to start from square one. Get one to work with way it was supposed to work, then add another and adjust your inductors as you go. If you go to the end product and it doesn't work you have several parts to troubleshoot versus just the one thing you changed from the last step.

Skipping all these there are inexpensive LED controllers. I have NOT used them, but they are designed to do all kinds of things. Some just light 10 leds some make 30 leds chase or blink. If you are interested in some the bigger ones I can send you some links. The ICs can run from $2-$10 bucks if memory serves.

shanakoenig (author)rcisneros2011-07-17

The IC is okay. It still works when I change back to a single battery.

Part of my problem with my IC is it only turns off once the I get at least .45 volts from my solar panel. This works fine with the solar panel that is included with the garden light. As soon as even a tiny amount of light hits it it produces at least this. I want to replace it with CIS solar panels rated at 5 volts open circuit and 100 ma short circuit. These are great in full sun, but inside with a light on they only produce about .1 ma in the circuit, not enough to turn off the light.

Do you know how many volts your circuit needs to shut off? I have contacted the supplier and I think I will order those, it seems the simplest way. Then I can change the inductor to my ma requirements, and add a diode and capacitor to the end for my color changing LEDs.

I would also love the link for some of the LED controllers you mentioned, more options are always better :)

rcisneros (author)shanakoenig2011-07-12

To test battery capacity I have a SMART Charger. I'm using a LaCrosse BC700. It has test batt capacity feature. About $25 on sale at Amazon.

shanakoenig (author)2011-07-12

Who manufacturers the IC you are using? I have emailed the vendor but if I don't here back do you know where else I can get them from? What exactly do they do?

Also if I use a 100 uf inductor will that make my lights about twice as bright but use my batteries about twice as fast?

Sorry for the basic questions I am really new to this. Thanks in advance :)

rcisneros (author)shanakoenig2011-07-12

Since I wrote this there are more mfg that make the IC. I got mine from QX microdevices. The replaces several components as it does the job of the transistors, the photoresistors and diodes. But bottom line it knows when to charge the battery and when to turn on the LED.

As for the second question, yes. The lower UH inductor you use, the brighter it will be, but it will burn through the batteries faster.

If you find super cheap solar lights, WITHOUT a photoresistor, the odds are they are using a similar IC. You could use that to mod if you wanted something different.

The QX5251F though, takes a lot of punishment. I've tested with a lithium battery and it didn't blow up. I'm going to test it with a 5v Solar panel and see if it works and for how long.

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