I built an 80 watt solar panel for less than $50.
About 5 months ago I began researching and experimenting with solar energy. That led to watching about a dozen videos on how to make solar panels and several searches on eBay for solar related gear. Before watching the videos I had purchased my first solar panels on Amazon for about $100 each and quickly discovered that they put out very little energy for what I paid. One was a 15 watt panel (Sunforce 50033 15-Watt Solar Charging Kit) and the other was a 30W Mono-crystalline Solar Panel With a 12V solar charge controller (the charge controller died within days). That motivated the DIY in me.
Solar tabbing wire and 5 inch solar cells
One of my goals in building my own solar panels was to re-purpose materials and spend as little money as possible. This is the second solar panel Ive constructed and it is rated at about 80 watts. Ive measured 19.5 volts on an open circuit with 4.9 amps in full sunlight on my first day of testing.
I mentioned that I built this panel for under $50 but that would be difficult to reproduce without acquiring more free or low cost materials. Here is a list of materials I used in this project.
- 5 solar cells (made in Japan) 5×5 square polycrystalline silicon @ $34.00 on eBay
- Two 2 x 3 x 8 Premium Kiln Dried Studs from Home Depot @ $5.00
- DAP clear silicone caulk from Home Depot @ $8.00
- 10 ft & 100 ft Solder covered Tabbing Wire @ $7.61 on eBay
- Dow Corning Sylgard 184 (normally $50 but received as gift for this project)
- Rust-Oleum spray paint (free)
- Screws and brackets for frame (free)
- Quarter inch tempered glass (free)
- Blocking diode (25 cents)
- Outdoor extension cord (free)
The solar cells are 5 x 5 and rated at 2.4 watts each, purchased on eBay for $34 (shipping included). I got 40 solar cells total and used 36 on this panel. I cracked two so 2 remain to be used in a future project. The frame was made out of wood and I purchased two 2x3x8 foot long pieces from Home Depot. Total cost for that was about five dollars. The hardware to put the wood together was all material I had in the garage. Basically screws, brackets, and paint. I had a can of pink rustoleum paint and a can of silver rustoleum paint. I sprayed those on the frame to make the wood more water resistant. Heres a close up view.
Homemade solar panel hardware closeup
The photo shows the painted wood frame, miscellaneous hardware, and glass sealed with silicone caulk. The quarter inch tempered glass I got for free from a family member. It was sitting in their backyard covered in dirt. That was a huge score in saving cash. I had clear silicone caulk in the garage but it turns out it was beyond the cure date and had already solidified. I purchased a tube of clear silicone from Home Depot for around $8 and used about half the container for this project. I went heavy on the silicone caulk and definitely could have used less and still created a watertight seal.
I made purchases on eBay as well. Cost for about 100 feet of tabbing wire (shown in the top photo) along with 10 feet of bus wire was under $10. I estimate I used about 50 feet of tabbing and maybe 3 feet of bus wire, plenty left over for building the next panel.
Besides the solar cells, the most expensive part of this project was Dow Corning Sylgard 184. Ive seen the product retail for around $50 online along with shipping ranging from $10-$20. Fortunately for me, I have family working in the silicone sealing industry, and my first jar of Sylgard 184 was acquired at no cost. That will not be the case for my next project so I will have to factor fifty dollars in or find an alternative sealant.
For wiring I used an outdoor 25 foot long extension cord that I got from my neighbor for free. He had cut through it and damaged one end, leaving it to sit in the yard to tangle up for a year or more. I told him about the project and he said take it. What I like about using an outdoor extension cord is that its already wired for the elements, and it had good 12 AWG gauge copper wiring inside. I soldered the extension cord directly to the bus wire, one on the positive side, and one on the negative side. I also wired in a diode to prevent the solar panel from discharging the battery when there is no sun. I bought a pack of diodes on eBay for a few dollars.
My homemade 80 watt solar panel in the sun
The remainder of the project was pretty much time. I invested about six hours on Fathers Day soldering all the solar cells and putting everything together. I broke a lot less cells than I did in my first project but I did break two cells in the final stages of preparing them on the glass. I chose to remove those and re-solder in two new cells. For me that has been the biggest drawback of making solar cells. They are extremely fragile and I have broken or at least cracked a dozen of them. That adds to cost significantly, especially if youre making only one solar panel. In my case, all broken cells go into a large bin, along with leftover cut tabbing wire and bus wire. I should have enough material to make a solar panel from broken cells and wire by the end of the summer. Ill use that panel for when I take a camping trip with my Jeep. Even if its only a 20 watt panel, that can help keep my batteries charged during camping weekends.
Since I started this project Ive collected more material for making frames, my next frame should be made at little to no cost and will be either aluminum, or a combination of wood and aluminum.
Since Ive had my minds eye on working with solar using recycled and/or re-purposed materials Ive collected a significant amount of material to use. Living in a large metro like Los Angeles provides an opportunity to get help and materials from others. Thank you! People have provided me with 12 volt batteries (one from a car and one from a UPS power backup system) and Im finding they feel good knowing Im putting items to good use. Ive also collected an old toolbox, (large enough to hold a car battery and solar controller), and several damaged outdoor extension cords. Seems everybody slices through those extension cords at some time, and usually wraps them up with electrical tape or duct tape.
I still have to mount the panel in a sunny place and find a lightweight protective backing, maybe a neighbor has Lexan Polycarbonate wasting space in their garage. Ill update this post after the panel has been in use a month or two and share how its doing.
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