Introduction: Making a 1 Watt Solar Array.

I love my neighbor’s garbage I call them the parts department. In this, instructible I am building a Solar Array out of 30 solar lights my neighbor threw out.

For this project I am only going to use 18 of the solar cells for the array I am building. The array will be able to charge a 12 volt 10 watt hour battery in a day. The total cost of building this array is about 5 dollars, a comparable array or solar cell can run you 60 dollars.

Since all the parts are salvaged, I will test every thing every step of the way, I don't want to completely assemble the array only to find out one of the components I used is faulty.

For testing you will need a multimeter.

Step 1: The Lights.

My neighbor threw out 3 different styles of solar lights.

I took them apart and kept the tops with the solar cells  and electronics.

At this point you don’t need tools all the parts clip or press together.

The white spot next to the solar cell or in the solar cell is a photovoltaic cell the photovoltaic is used to set the light into charging or lighting mode.

Step 2: Dissamble the Tops.

I took apart solar light tops and kept the internal parts, the solar cells and electronics.

At this point all the tools I needed was a screwdriver and a wire cutter.

Step 3: Clean the Solar Cell.

Clean the caulking and other debris off the solar cells, a utility knife works well, try not to damage the solar cell by scratching it.

Step 4: The Usefull Parts.

The parts inside are, the circuit board with an LED light, the solar cells, and the photovoltaic.

Some of the solar cells have the photovoltaic attached to the solar cell, like this green solar cell.It can be remover by unsolder the connections.

Some of the photovoltaic are hot glued together just apply a little heat and they come apart.

At this stage the tools I used was a wire cutter, a soldering gun, and a hot air blower.

Step 5: The Salvaged Parts.

When deconstruction is complete these are the parts you have salvaged.

Surprisingly you can buy a solar powered light for less than buying the parts.

The circuit board sometimes useful sometimes not.
The LED light
The solar cells
The photovoltaic
Some rechargeable batteries, most of the time the batteries are no good.

Step 6: Fixing a Cell.

Plastic solar cells can be compromised by scuffing on the surface of the plastic cell, or oxidation of the plastic due to UV light from the sun.

Coat it with UV resistant clear coat or lacquer and test the cell again this can improve your cells by 20%.

Step 7: Connecting and Testing the Solar Cells.

Under room lights check the voltage coming out of the solar cell you should get some voltage.

If you get no voltage the cell might be damaged or the wires might be bad.

Replace the wires and test or replace the cell.

Solder the cells in series + to –

Under room lights check the voltage coming out of the solar cell array.

If you tested all the cells before assembly and get no voltage after assembly, one cell might be connected backwards or the wire connections might be bad.

Resolder the cells or replace the wires and test.

I know I might sound like I am repeating my self but there is an old carpenter rule. “Measure twice, cut once.”

Step 8: Testing the Array.

Test the array under diffuse sunlight and full sunlight checking the voltage coming out of the solar array.

You will get little differences in the voltages for different light levels within its function range.

The voltage you get will be different for the different cells.

Plastic cells give about 2.2 volts, glass cells give about 3.1 volts a cell.

Glass cells give you a higher voltage then the plastic ones.

Keep adding solar cells until you get the desired voltage.

About 1 volt above the voltage you want, so if you want 12 volts add solar cells until you get at least 13 volts.

This is for a Diode to protect the solar cells from reverse current, there is a voltage drop across a diode.

If you are planing on using a voltage regulator like LM7812 you will need to add more cells to get more voltage.

Step 9: Schematics.

I had a total of 7 glass solar cells, 7 black solar cells, and 16 green backed solar cells.

With salvaged solar cells I don’t have the specs so I don’t like to mix different cells in series to be sure I don’t create an over current in a cell.

With solar cells you should always have a diode to prevent a back current from batteries and strings of solar cells in parallel.

The 1N5819 Schottky Diode prevents back current when the different cells are connected in parallel.

Since there are three different cells of different sizes I only used the green and the black plastic cells for aesthetic reasons.

In a 12 volt array which I wanted, I had 7 glass solar cells, 1 black solar cell, and 4 green backed solar cells left over from the thirty solar lights.

This is the Schematic.

Step 10: Assembling the Array Strings.

Start with a straight edge, line up the solar strings and tape them in place.

When you have all the strings in place it is ready for the internal sponge.

For the internal sponge I used ¼ inch sponge rubber weather seal. This will hold the cells in place against the faceplate.

Replace the tape with the weather seal systematically in order to keep the internal parts in the shape you wanted and connect the lead wires.

Then test to make sure you are getting the right output.

Step 11: The Outer Casing.

The front and back of the outer casing is made with Plexiglas, I of course got from my neighbors garbage and the edges are made of ½ inch thick sponge rubber weather seal. Cut the Plexiglas 1 inch wider then the assembled solar cells. In my case that was 8 by 14 inches.

The cutting tool I use to cut Plexiglas is made out of a standard screwdriver.

I ground the tip of the screwdriver to this shape.

Scratch the Plexiglas deeply following the straight edge.

Then flip the Plexiglas over and bend the Plexiglas at the scratch it will break along the scratch.

Step 12: Assembling the Outer Casing.

Place the solar cells face down on the front of the outer casing and attach the ½ inch sponge rubber weather seal around the parameter holding the cells in place.

Place the back of the outer casing on to the array and tape the Plexiglas in place.

Drill one hole at a time in the center of the sponge rubber weather seal and bolt finger tight. Over tightening the bolts can break the Plexiglas.

Drill the next hole at the opposite end of the array in the center of the sponge rubber weather seal and bolt finger tight.

Repeat this until the bolts are around the parameter of the array housing and remove the tape.

Step 13: The Final Test.

The last thing to do is test the array.

This does not need a charge controller to maintain a car battery or a battery in storage it is not strong enough to charge a car battery from dead but it will maintain a large battery not in use.

If you do make an array make an instructible on it and here is a little advice.

Try not to mix different makes of cells in string series to be sure you don’t create an over current in a cell in the string or the string may fail if a cell burns out.

With solar cells, you should always have a diode to prevent a back current from batteries and the other strings of solar cells in the array hooked up in parallel.

Back currents can drain your battery at night or burn out a cell string even when you are not using the array.

There is a voltage drop across a diode, try to pick a diode with the smallest voltage drop.

Small cells like the ones I used create a small current so if you use diodes rated for 1 amp you should be safe.

Make sure the diode is rated for a voltage greater than the string voltage generated by the string, the 1N5819 Schottky Diode is a good diode it is rated for 40 volts and has a voltage drop of less than 1 volt.

High-speed diodes have the small voltage drops and Germanium diodes have voltage drops as low as .45 volts.

Last seal up the array so morning mist and rain wont short out the array, you wont believe how many commercially available solar cells cannot be let get wet.

Hope this is helpful

Joe

Comments

author
Josehf Murchison (author)2011-12-03

If you do make an array make an instructible on it and here is a little advice.

Try not to mix different makes of cells in string series to be sure you don’t create an over current in a cell in the string or the string may fail if a cell burns out.

With solar cells, you should always have a diode to prevent a back current from batteries and the other strings of solar cells in the array hooked up in parallel.

Back currents can drain your battery at night or burn out a cell string even when you are not using the array.

There is a voltage drop across a diode, try to pick a diode with the smallest voltage drop.

Small cells like the ones I used create a small current so if you use diodes rated for 1 amp you should be safe.

Make sure the diode is rated for a voltage greater than the string voltage generated by the string, the 1N5819 Schottky Diode is a good diode it is rated for 40 volts and has a voltage drop of less than 1 volt.

High-speed diodes have the small voltage drops and Germanium diodes have voltage drops as low as .45 volts.

Last seal up the array so morning mist and rain wont short out the array, you wont believe how many commercially available solar cells cannot be let get wet.

Hope this is helpful

Joe

author
ninadt23 (author)2016-11-11

Dear Sir,

I am had done the small lanterns 20nos for my window.

i am using that form 7to8months. now out of 20 5 has battery size expands & they cant stay for half hr

i had use 5volt/80mA solar panel & battery lithium polymer 3..7volt/400mA with one diode only i am connected on output 3LEDs 3volt/20mA with 72ohms of resistor.

can you please help me to how stop to expand this battery problem?

author

It sounds like your battery is a little small and it may not be fully charged.

Your 5 volt 80 mA solar panel should be able to charge a 3.7 volt 800 mAh battery in 5 hours of full sun.

Is the solar cell getting full sun for 5 hours?

If it is not getting full sun for 5 hours you need to move the panel to where it gets full sun for 5 hours.

author

yes it will not fully charge but more than sufficient for my application. i am using for deem lantern.
so i am using low power LED with resistance in series so it is glowing for 7 to 8 hrs
now i just want to ask you is it want any resistance to protect my lithium polymer battery.
my battery have inbuilt PCM/PCB protection but then also it is expands its size.

author

You might find this page helpful;

http://www.fpvforme.com/charging-lipo-batteries/

author
jisaac6 (author)2016-07-23

Thanks sir, I have read and digest the step 9. The Pv has reverse diode protection to eliminate any feedback from other Pv connected in parallel with it. Thanks so much sir.

author
wmada (author)2015-05-21

hi. can any one offer any explanation. I have 8 solar cells. each tests at 3.1v i hooked them all in series i got up n down numbers as if bad cells of wires. so i took apart. i hooked 3 cells and get 9.1 v good i guess right? but wont drive a dc fan motor.? so anyways I went to add another cell to row and i drop to 2 volt. i figure bad cell? so i get two rows each 9 v but when i connect those two i only get 9 v? what am i doing wrong? i tried connecting the two rows in series and parallel any thoughts?

author
ajensen27 (author)2014-06-07

OK so I made one to charge my cell phone. it makes about 12.08 volts. but I have no idea as to the current. they were Walmart cheapies. (like a dollar each) I would like to have used some sort of USB adapter but could I just stick the wires on the battery? its a li-ion rated for 3.7v and 1500mAh. I want to charge it in a few hours not days. any help would be very appreciated.

author
ajensen27 (author)ajensen272014-06-07

sorry I meant u made an array. no diodes or anything.

author

Mine is three lines of solar cells and charges at 360 mah per hour.

author
wouternet (author)2012-02-19

Plastic doesn't oxidize. It decomposes or degrades.
Metal oxidezes. And oxidation isn't caused by UV light, it's caused by water and oxigen.

author

Oxidation isn't caused by UV light? You couldn't be more wrong.
The vast majority of plastics are polymers (around 98% of them) and Polymers most definitely oxidize. In fact Polyethylene, polypropylene, and poly(methyl methacrylate) oxidize due to UV light.
I realize this post was quite sometime ago however, stating that a person is incorrect when it's yourself making false statements is just bad form.

author

Don't be to hard on him most people are taught oxidation is water iron and air, when that is far from the truth.

author
Valeriy (author)2013-10-07

А если подключить преобразователь то можно и 220 вольтт получить для дома !

author
Josehf Murchison (author)Valeriy2013-10-07

My Russian is bad so I hope you can get this.

Solar is not fixed the sun and clouds, even a cold day effects the efficiency of the solar cell.

This one runs 450 ma in good light most of the time it is less and the volts get as high as 18. That is why I call this a 1 watt because over 1 week of charting its output averaged 1 watt during daylight hours.

However if you build one the components you use will in all probability will give you something different let alone what the sun shine will do.

You must remember electronics is a ball park and sometimes that ball park is big and sometimes it is small.

Joe

author
kuhldad (author)2012-12-31

Followed your guide and was successful on my first try! I polished my plastic round panels with a buffing wheel and some Brasso instead of painting a clear coat. I received a bottle of the resin as a Christmas present so I used your instructable to make a 26 volt solar panel to trickle charge a slow go-kart I built for my boy.

author
Josehf Murchison (author)kuhldad2013-01-01

Cool you should post a Pic of it.
Joe

author
cobourgdave (author)2012-03-29

I like this instructable. I had not considered the garden light solar panels in this way. Clearly I am going on a scrap hunt amongst the garage sales this spring. Nice instructable with good clear instructions and good pics.
Well done sir.

author
wouternet (author)2012-02-19

I'm only seeing volts here. How much current can it deliver?
It will probably be about 150 ~ 200 mA....

author
paintphone (author)2012-02-09

So I used your instructable and made an upcycled solar pannel myself, here is what i came up with: 5 glass cells and a wopping 16.4V thanks so much for helping me understand this more.

DSCF1633.JPG
author

cool it looks nice also
Joe

author
paintphone (author)2012-01-24

I love just driving down the road and seeing some perfectly good solar lights, just hazed over and in need of a quick scrub with 1000 grit wet sandpaper and a quick coat of clear or 5. Defiantly going to a new home  a new home. This is going to be very useful for me. Great Instructable!

author
dasimpson1981 (author)2011-12-01

sorry to tell you but the voltage you are getting is not the voltage you need to charge a 12 volt battery from solar most solar panels are 18-21volt

author

I have checked out commercially available solar cells of the same power they only go up to 15 volts max 12 volts average. Even the charging system in a car only goes up to 14 volts.

author
Dr.Bill (author)Josehf Murchison2012-01-12

I have a 10 panel array. Each panel produces 22V @ 1.18A/20 W

My array produces 200W @ 11A.

I charge 2 Deep Cycle Marine batteries and run them through an inverter to

power a 625W device.

If I wire them differently I can get 220V out of them.

author
Josehf Murchison (author)Dr.Bill2012-01-13

If the solar panels don’t have a diode in them, I hope you put a diode between the solar panels in parallel.
I get a much larger wattage.

I x V = W
1.18a x 22v = 25.96 watts
25.96w x 10 = 259.6 watts

If you connect them in series you should get 220 volts at 1.18 amps and 259.6 watts.
You can connect them together two different ways.

220varay.GIF
author

Sorry wrong diodes 1N5403 in the top schematic and 1N5400 in the botom.

author

deep cycle batterys are not to be charged the same way as a car battery different voltages etc but all solar info i have read says 18v-21 i guess that way it can start charging sooner with less light

author

You want more build your own.
I have commercially available solar cells.

Picture.jpg
author

i will be doing soon i will go round collecting the end of crimbo ones every one seems to scrap

author

If you do make an array make an instructible on it and here is a little advice.

Try not to mix different makes of cells in string series to be sure you don’t create an over current in a cell in the string or the string may fail if a cell burns out.

With solar cells, you should always have a diode to prevent a back current from batteries and the other strings of solar cells in the array hooked up in parallel.

Back currents can drain your battery at night or burn out a cell string even when you are not using the array.

There is a voltage drop across a diode, try to pick a diode with the smallest voltage drop.

Small cells like the ones I used create a small current so if you use diodes rated for 1 amp you should be safe.

Make sure the diode is rated for a voltage greater than the string voltage generated by the string, the 1N5819 Schottky Diode is a good diode it is rated for 40 volts and has a voltage drop of less than 1 volt.

High-speed diodes have the small voltage drops and Germanium diodes have voltage drops as low as .45 volts.

Last seal up the array so morning mist and rain wont short out the array, you wont believe how many commercially available solar cells cannot be let get wet.

Hope this is helpful

Joe

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Bio: I am a photographer, a tinker, an electronics technology engineer, and author; I write short stories and poetry for the love of writing. I started ... More »
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