Introduction: Solar Power System With Up-cycled Components.

Picture of Solar Power System With Up-cycled Components.

Scope of Project.
The objective of this project is to assemble and install a stand alone solar power system (Photo Voltaic or PV) . My goal is to run 2 LED light bulbs in fixtures on my workbench and charge/maintain my power tool batteries. My estimated load will be 2 x 10W/LED bulbs, and 85W for the charger while it is actively charging batteries. As I have included my cordless power tools into my emergency preparedness plan, the ability to charge those batteries off grid is a necessity. Eventually I would love to go completely power neutral and do a full on grid tie system with a battery backup but that would require an electrical engineer and more money than I can invest in the mean time.

Personal history

I became interested in solar power after I saw my first Space Shuttle launch. I want to say it was 1980 something and I was just a tiny tinker gnome. The ability for a satellite to obtain its power from sunlight was absolutely fascinating to a young tinkerer whom had a habit of taking his toys apart to make new toys. Heck some of those creations even worked, providing one used enough imagination.

Around 2001, A friend turned me on to Home Power Magazine. I loved that rag and for the longest time I was a subscriber. Each month showcased yet another build and my lust for solar power continued to grow. the down side was that during the early 2000's, panels alone were running in the $6/Watt range. I pushed it off in my mind and hoped that prices would eventually drop to my tinkering budget.

Side note, I was the second tick for Guerrilla Conservation on their old map Columbia Missouri. I stole the incandescent bulbs from the fixtures in the apartment building I lived in and replaced them all with CFL bulbs. In the letter I left in the managers box i stated what i had done and why, along with explaining the savings they would experience. I dont think my anonymous bulb theft was really noticed as the CFL's remained the entire time I lived there. I do believe the statute of limitations has elapsed for the petty theft of lightbulbs.

Over the years I have continued to salvage parts that wold be compatible to build a PV system. I was able to obtain 3 deep cycle batteries from routine maintenance on my employers UPS. Other scrap I have amassed during annual junk cleaning of my department. For example I managed quite the box of 10-12 gauge wire and Anderson connectors, Fuses, and other bits from smaller UPS's.

I had planned on going with a 45W Harbor Freight kit, as they can be found for as low as $130 on sale. However from friends that have gone that route, they report that the charge controller just did not hold up to 24x7 usage. So I kept looking and waited until the price was right to buy standard components with out a proprietary kit.

Initial design and how it changed.
I had initially only planned on installing the Renogy 100W starter kit on a pallet wood ground mount, and calling it done. However after placing my first order, I realized that I had a bunch of credit from trading in school books and DVD's.. The result was that I was able to doubled the system generation capacity with a second 100W panel and the other bits and pieces to wire them in parallel.

I had also originally planned on building a simple fixed angle mount out of pallets. However this changed when i realized that the sattelite pole mount would work better and allow me to easily trim the grass under it. The old dish was a bit of an eye sore, just standing there unused and unappreciated. As I was in the process of pulling it out, I noticed that it was graduated for angles of elevation. I thought to myself that's it! I will get as much of the pipe out of the ground as possible and build a mount using the graduated bracket. And if it does not work ill go back to the sled idea. So I applied my trusty scientific method of stress testing the mount, by swinging on it like a silly monkey and determined that it may just work.

All documentation for the Renogy Products listed can be found here.

Anyway enough speculation and planning on to the good part.

Step 1: Inventory of Parts and Tools Used.

Picture of Inventory of Parts and Tools Used.

Stuff Bought From Amazon ( I had about $160, in store credit and trade on my account so my total out of pocket was about $200)

I started off by ordering the following 100W kit. 209.99

  • 100-Watt polycrystalline solar panel.
  • One pair of 20 feet MC4 cables
  • One set of Z Brackets
  • Renogy PWM 30A LCD Display charge controller

Then I added another 100w panel 135.99
A Y junction to connect the 2 panels in parallel. 12.99
A 30 Amp inline fuse for the PV positive $18.00
A pair of MC4 assembly/dissassembly tools $6.99
A second set of Z Brackets $13.49

Stuff bought from the local farm and home store.

  • 2 x 2 gauge cable ring terminals $3
  • 4 x 2 - 8 Gauge clamping ring terminal $4
  • 6 x 6mm x 20mm standard thread bolts $2
  • 60lb bag of ready mix concrete $2.97

Stuff scrounged from scrap piles and saved from the landfill over the years.

  • 400W - 12VDC to 110VAC inverter (work was going to toss this so I saved it)
  • 4 gauge electrical cable (left over from new electrical service installation)
  • 10 gauge wire in various lengths (salvaged from various UPS)
  • 2 Anderson quick connects (UPS salvage and already on wire)
  • 3 x 215 Wh Deep Cycle Batteries (salvaged from a UPS)
  • Wildblue Satellite dish pole and bracket (removed from the yard)
  • Pallet Wood (from local trailer manufacturer)
  • Treated 2x4 (storm salvage)

Stuff from stock on hand

  • Red and Black Electrical Tape
  • 10 Gauge ring terminals
  • 10 Gauge butt connectors
  • 2 3/4" Deck screws
  • 1 1/2" Deck Screws
  • 1" drywall screws
  • Rosin Core Solder

Tools Used

  • Reciprocating saw with metal cutting blade
  • Circular saw
  • Impact driver
  • Hammer drill with 1/2 Masonry Bit
  • Socket Set
  • pocket knife
  • 6 in 1 screwdriver
  • Wire Cutters
  • Wire Crimper
  • Tape Measure
  • Protractor
  • Bubble level
  • Lensatic Compass (direction finding and aiming)
  • Shovel (for diggin holes)
  • Hoe (concrete mixing and packing)
  • Storage Tub (concrete mixing)
  • F250 (borrowed to pick up pallets, thanks John & Jared)

Safety Equipment

  • Goggles
  • Hearing Protection
  • N95 Dust mask
  • Wool Blanket (to cover the panels)

Step 2: Battery Bank Building.

Picture of Battery Bank Building.

While waiting for the main components to arrive, I began work on building the connectors for the batteries.
I reasoned that battery interconnect cables would be needed, along with a disconnect to safely remove the bank from the charge controller. I used 2 anderson quick disconnects and some bits of wire to make the battery to controller connection. I also added a fuse so if I had an oops moment it would blow before my batteries did.

The batteries are being wired in parallel. Each positive will be connected to each other positive using jumper wires. The same goes for the negative leg. The difference between parallel and series. Parallel increases capacity, while series increases voltage. Had I connected them in series I would have a 36V battery bank and would probably have some toasted electronics.

For determining wiring using a 2% acceptable loss I used the following calculator.

I was able to determine that a 3ft/1meter run would be safe for 10Ga wire at 30Amps.

*EDIT* If you use Aluminium cable for battery interconnects in your own set up make sure to use an Anti-Oxidization compound or bad stuff can happen. I did not at the time, but will correct that defect as soon as possible. I over looked this detail and figured that 4 gauge wire for runs of 1 ft would be good for more amperage then I would ever pull from this bank. Thanks to Vyger for pointing this out.

This is what I came up with

  1. I measured and cut 4 x 1ft sections of 4 gauge wire. The wire was left over from an electrical service installation.
  2. Using a pocket knife I scored the insulation about 3/4 of an inch from the tip, then used my wire cutters to strip the insulation.
  3. 2 of the bus bars used the screw clamp terminal end however the hardware store only had 6 so I had to use 2 solder/crimp ring terminals
  4. Open the screw terminal, insert the wire, then tighten it back down using a pair of plyers to hold the terminal for the final turns.
  5. To solder the 2 ring terminals on, I first clamped them into my metal vise.
  6. Then I used a small butane torch to heat the copper terminal and filled the well with molten solder.
  7. While applying heat to the terminal end I preheated the cable end in the flame and gently inserted it into the terminal taking care not to splash solder.
  8. After your jumpers are made color one double clamp and one clamp/lug terminal wire with red electrical tape to indicate +

Allow the terminal to cool before removing the connector from the vise.

This video is a variation of the technique described above I made years ago for R/C bullet connectors. Instead of the little bullet connector it is a big ring terminal.

Now that the large gage jumpers are made it is time to make the small gauge connection for the Charge controller.

This one is pretty simple. I selected the anderson connector that had the longest pieces of wire. Then I selected another that was wired so that when the connection is made they would line up + red to +red and - black to - black

As the wire already had blade connectors that fit a large 60 Amp fuse that I had I just stuck it inline on the positive side. then used electrical tape to ensure that it did not inadvertently short out on the - side. Don't use an automotive type blade fuse like I used the industrial blade fuse. The heat generated can melt any heat shrink and cause a short if it is not in a proper fuse holder.

The black side was not as long as the red due to the addition of a fuse so I crimped on another length of wire using a 10 gauge butt connector. Then finished the lead off by Crimping a 10 gauge ring terminal on the free ends.

The side that goes into the charge controller just has 1/4" insulation stripped off with twist on the free end to keep it from fraying while being inserted.

If you do not know how to crimp a connector or strip wire I suggest looking at the below video. I don't own it and only link as he licences under creative commons.

Step 3: Bench Test.

Picture of Bench Test.

Now that all the components are in, and the battery jumper cables are made it is time to test it all out to make sure everything works before building the mount.

Of note when connecting and disconnecting solar panels make sure you cover them so that they are not generating electricity to prevent shorts and turning your fancy green energy producers into slag.

Starting with the Charge controller I made my connections right to left.

  1. Attach included temperature probe to the charge controller.
  2. Strip and connect the cables for the inverter to the load port on the charge controller ensuring correct polarity.
  3. Connect the controller side of the battery cable to the battery terminals ensuring correct polarity.
  4. Cover the solar panels and make note of which side is negative. Attach both negatives to their respective Y junction.
  5. Connect both positives to their respective Y junction.
  6. Connect the inline fuse to the single end of the positive junction
  7. Connect the negative lead to the negative junction then connect it to the charge controller
  8. Connect the positive lead to the fuse on the positive junction and connect it to the charge controller
  9. Ensure your batteries are wired up correctly and join the quick connect.
  10. Note at this point the charge controller is now energized and will display the status of the solar array and Load.
  11. Uncover the solar panels and enjoy collecting energy from the sun.

By pressing the menu cycle button I was able to verify that my panels were producing 7 Amps of power and my tool battery charger was using 3 Amps. I was also able to verify the voltages by touching the probes of my multimeter to the screw terminals on the charge controller. I noticed 13.21V on the solar array, 13.19 on the battery , and 13.18 on the load terminals.

Using the Renogy MC4 wrenches, I disconnected the battery bank and disassembled the panels using the reverse of how I assembled above. The only difference is that I marked the positive side with red electrical tape before disconnecting it to make hook up easier after passing cable through the wall.

Step 4: Recovering the Pole

Picture of Recovering the Pole

Once upon a time where we were in the country the only internet service was laggy satellite internet. Sure it had decent speeds once it got going but ping returns were measured in seconds. Needless to say I ditched it as soon as there was a better alternative but I still had the pole and dish.

While Taking the dish out I noticed that the pipe was some pretty stout stuff and I could hang all 250 lbs of me from the arm of the dish with out the pole flexing hey and the bracket is marked to indicate the angle the dish is pointed at. I wonder if I could reuse it for my solar panels? That was my eureka moment I was now determined to get the pole out of the ground and re use the bracket with the fancy graduations to tilt my panels. The only thing was how the heck can I get it out of the ground. The short answer is that I didn't. First I unbolted the dish from the angle bracket then dug down until I hit concrete. I then used a reciprocating saw with a metal blade to cut it off as flush as possible.

The resulting pole was about 5'6" including the mount. I also salvaged all the bolts and nuts, as well as the mounting plate from the back of the dish. The resulting scrap dish pieces went to the boy down the road who gathers metal to sell back to the recyclers. I gotta hand it to the kid he works hard for the pocket money he earns.

Step 5: Fabricating the Frame to Mount the Panels.

Picture of Fabricating the Frame to Mount the Panels.

Going with the upcycled/reused theme of this build I grabbed the long piece of 2x4 and measured it hoped that it was long enough to get 2 boards to make the top and bottom edge horizontal boards. The 3 vertical stringers only need to be as long as the Z Bracket mounting hardware. The pictures should clarify this.

The following is how I made my panel rack.

  1. Lay out the panels into the position they will be mounted.
  2. Measure their width and length accounting for any hardware
  3. Mark and cut the long 2x4 in half these will be the horizontal sections.
  4. Find a pallet that has good stringers at least as long as your bracket locations on the vertical.
  5. Carefully break down pallet to obtain the stringers.
  6. Determine which is the best stringer and find its midpoint
  7. Center the mount plate on the board and align it square
  8. Mark out a pattern for screws
  9. Slowly drill screw holes that are the same diameter as the shank for your 11/2 deck screws.
  10. Use a drop of oil to keep the bit lubricated.
  11. hold it up to the light and admire your handiwork
  12. Find the center line of your horizontal supports
  13. Center the middle stringer, placing the marked side down. Square it up with your protractor, and screw it using 3 2 3/4 inch deck screws in a V pattern. If on this side you are pointing down when it is flipped for the back side you will want them to point up.
  14. Screw the other 2 vertical stringers ensuring that they are also square.
  15. Flip the assembly over and use the same screw pattern only reversed. If the "front" had the V pointing down have the V pointing up on the "back".
  16. Insert carriage bolts into the mounting disk. Then screw it into the stringer where marked.
  17. Using the carriage bolts attach the pole bracket on to the mounting disk. And tighten the nuts down using an appropriate socket.

At this point I mounted the pole in my bench vise. I checked to ensure that the pipe was level in 2 directions. I then set the rack in place on the end of the pipe and checked to make sure that it was level as well. I also loosened all the angle adjustment nuts and was pleased to see that the rack was balanced enough that it did not tilt on its own accord and stayed in the position it was set in.

I checked the most angle I can achieve is 60 degrees instead of the optimum 74 for the summer solstice. But the good thing is that the efficiency lost I am more then going to make up for in hours of daylight. The good news is that I can tilt my panels toward the optimum angles for the winter months when daylight is a much rarer commodity.

To figure out your optimum angles of tilt from vertical the linked calculator will show you all you need to know for your location.

Step 6: Drive and Secure the Pole in Concrete.

Picture of Drive and Secure the Pole in Concrete.

Figure out where you are going to want to sink your pole. I chose an area that Gets good sun during the summer from 10 Am - 7PM when the trees shade that part of the house. However in the winter the trees will loose their leaves so it will get even better sun then. I guess that is all that needs to be said so on to sinking the pole.

  1. I dug a hole about shovel deep, and a bit wider then a shovel and a half wide.
  2. Then I centered the pole in the hole and due to the water logged clay it stood on its own accord.
  3. Using the short 10lb hammer I re-handled in a previous instructable I drove the pole in about 2 and a half feet down. Using a scrap of wood to prevent the pole from mushrooming out.
  4. Check level in 2 directions and lightly knock the pipe sideways to correct for any variance.
  5. I mixed the concrete in accordance with the packaging, in a storage tote.
  6. After mixing pour the concrete around the pole.
  7. Use the hoe to tamp the concrete until it is a uniform flatness.
  8. Let the concrete set according to package directions and clean your tools.

Step 7: Putting It All Together.

Picture of Putting It All Together.

This one is dirty. If you only have a cordless Hammer Drill with a dull masonry bit like I dis you are going to have a bad time. Concrete dust is going to go everywhere and it will mess up your lungs so wear a mask/respirator and goggles not just safety glasses. Hearing protection too. Trust me this part sucks.

  1. Put on the safety gear
  2. Chuck your masonry bit into your hammer drill
  3. Insert a fresh battery.
  4. Start drilling the hole through the garage wall where you want to route the cables.
  5. Keep drilling through the 6 inches of concrete
  6. keep drilling through the 8 inches of concrete
  7. Change battery
  8. How thick is this wall anyway 10 inches a foot I don't know.
  9. Still drilling..
  10. Finally broke through to the other side. It was 10 inches thick and I only know as I measured the bit after I was done.
  11. Blow dust out of the hole using a can of compressed air or a leaf blower. Keep your mask on.
  12. Insert your cables for the charge controller from the outside in. Note the red tape for the positive cable.

Yes I made a big production out of drilling the hole but it honestly sucked and I hope to never do such a thing again. I must have hit 2 or 3 rocks in there and with no good way to apply pressure to this drill I just kept on hammering on. Now mount the panels to the rack.

  1. Attach the Z brackets to the panels according to their directions using an appropriately sized socket.
  2. Lay out the frame bracket side down and support it up with blocks to that it is not wobbly (2x4 tower FTW)
  3. Center the first panel onto its side of the rack. Secure it using the included self drilling screws and an impact gun or drill driver.
  4. Center the second panel and attach it in the same manner.

Step 8: Final Assembly

Picture of Final Assembly

Ok this Has been a long instructable but thanks for bearing with me.

Now that the panels are mounted to the frame it is time to carry it out to the pole and finish hooking it all up.

  1. I first mounted the charge controller to a small wooden book stand that I found in a dumpster. Using 1" drywall screws
  2. Then I mounted the inverter by wedging the screw heads into the side fins of its chassis 2 on the long sides with 1 on the ends Not tight just to keep it secure as there are no mounting holes.
  3. Then I mounted the bracket for my tool battery charger in place.
  4. Finalize the hookups working from right to left. Inverter, Battery, Panels DO NOT CONNECT THE BATTERY BANK AT THIS POINT.
  5. I carried the assembled PV rack out to the pole with the bracket as close to vertical as I could get it.
  6. I then Used my compass to aim the rack at 180 degrees south.
  7. Using a socket wrench I tightened the mounting clamp.
  8. Covered the rack with a blanket to ensure that it is not generating any electricity.
  9. Connect the PV panels to the cables to the Y combiner junction and fuse, the same way as the bench test instructions.
  10. Connect the battery bank disconnect to the storage batteries.
  11. Uncover the panels.
  12. Set the panel angle according to the time of year.
  13. Secure the angle adjustment.
  14. Zip tie the cables to the pole,
  15. Inject a bit of caulk into the hole to seal it.
  16. Check the readouts to ensure voltage from the panels, battery and load.
  17. Verify the amperage flowing into the storage battery.
  18. Verify amperage flowing to the inverter.
  19. Charge up the batteries used to build this all.
  20. Enjoy the beverage of your choice while you put your tools away knowing that you are now harvesting clean energy and that your projects will now be that much better for it.

Step 9: In Conclusion.

Picture of In Conclusion.

This was an involved project. I have learned quite a bit in actual practice to go along with all the theory and principles that I have read about over the years. I like omitting the phantom load of my Ryobi "Super Charger". It is a good feeling knowing that my 7 Li-Ion battery packs are being charged via a clean power source. I have also ran the power outlet from the work bench to the inverter so that I may power my LED light fixtures from it as well while I am tinkering with easy access to grid power to run energy hog tools like my shop-vac and sander.

When and If the battery bank dies, I think I am just going to replace it with a single or pair of group 29 marine deep cycle batteries. The 3 batteries that I have now only have a capacity of about 60 Amp/Hours combined. When a large deep-cycle marine battery has anywhere from 80-120 Amp/Hour Capacity. The only downside is that each battery would vary in price from $100-200. I would already have the cores to exchange so I guess I have that going for me. However I would have to build a vented battery box as the sealed AGM batteries I have currently are spill proof and non vented.

Arthur and I have been tried various experiments; shading panels, pointing them in non optimal directions and angles, varying them from dusty to wet, all while noting the differences in voltage and amperage generated on the charge controller display. I think he is just as amazed as I was and he likes the idea of getting free electricity.

Future upgrades will include replacing the battery bank as they fail before adding more solar capacity. However it would be relatively inexpensive to add another 200W of solar. The only down side is that if I went more then 400W of solar I would need to expand to a more expensive charge controller and possibly a larger inverter. Currently 100W panels can be found for about $1.50/ watt delivered down from the $5/watt + shipping back when I started lusting after solar power. However it is far cheaper to add efficacy then it is to add capacity. If you can save 10W per light bulb that is 210W per week for 3 hours nightly run time that you would not have to collect and store in your solar system.

Another thing to think about if you are concerned about atmospheric carbon and climate change. Every 1 Watt/hour of electricity saved, or generated via clean energy sources, sequesters about 500mg of atmospheric carbon. Take the 10W savings for switching a single compact florescent to a LED light bulb will prevent 105 grams of atmospheric carbon from being released.

If I am able to use the full amount generated by my system each week, I would be able to save 5 Kilowatt Hours of electricity, 3500 Grams of atmospheric carbon, and about $.55 with my electric bill. I guess every little bit helps, so I will continue to change out CFL's with LED bulbs and replacing old power hog appliances with newer energy star rated ones.

Camping and Disaster Preparedness.

I tend to think of all the different ways I can use something. With a background in firefighting and emergency management I tend to know that disasters will happen the only variable is when. So now if the power goes out my family has a back up to the grid and can run some modest loads virtually indefinitely.

When I picked the tool line I wanted to go with I chose Ryobi for 2 reasons. They are affordable and there is a wide variety of tools that are interchangeable with the same battery type. Granted the lithium batteries can get expensive however I was able to maximize my battery quantity by buying refurbished lawn tools that included batteries and a tool. As such I wound up with 7 battery packs 2 High capacity packs 4 standard capacity and one standard capacity + pack.

  • In the event of a storm the reciprocating saw with a tree trimming blade should make short work of 10 inch branches. wood metal and other cutting the rest of the time.
  • The Radio also has Bluetooth audio connectivity and the ability to charge phones and other devices via the USB port. Tunes and a phone top off while working. Information, entertainment, and a way to keep connected in a emergency.
  • The 2 x 120 lumen LED lanterns are perfect for sitting out by the fire pit camping or on the porch. Sometimes you just need to not sit in the dark. They are perfect for closing up the chickens reading at night or any other use where one may want to see in the dark.
  • The flashlight Is even better instead of a nice area light it projects a pretty tight beam perfect for poking around under the car or trying to figure out what that noise was in the pastures.
  • I can also charge my laptop and tether through my phone for internet providing that the cellular towers are still up.
  • With the garage being all poured concrete It should survive some severe storm damage. And the LED light bulbs on my workbench are perfect for being run off the inverter and battery bank. So that I can set up a temporary kitchen with my butane camp stove, Alcohol Stove or good ole fashioned grill.
  • All though I have yet to try it I should be able to run a mini-fridge that I keep in the basement family room as it is supposed to only draw 1 amp at 110v. I just don't want to hork out the fridge to the garage. But one of the long extension cords may make a sufficient test.

In conclusion I hope that my experience in installing a small solar power plant has instilled a desire to get you building if you have any questions feel free to ask I will be more then happy to help in any way I can. Or if you have seen something where I have messed up or caused a potential hazard please let me know.

After using the system for 2 weeks....

I have been using my system for about 2 weeks, and I have of good news to report. It seems that the charger only pulls 85 watts when it is actively charging the tool batteries. After my main battery bank is fully charged the controller shuts off the PV array. Resulting in only banking about 10-20 Amp Hours a day of clean power. with my surplus generation capacity, I also charge both of our laptops a cellphones. I also noticed that the fan that I run in the garage shop, is only a 200W load when it is on high. So when I am working in the shop I can run my fan, along with my bench lights, and charge my tool batteries all at the same time. The resulting load for all that would be at most 305W @ 120V or 25 amps on the 12v side. With the sun shining I can run it almost all day and for about 2 hours after dark.

Tropical depression Bill. Last week the remnants of tropical storm bill came rolling through, we experienced hail high winds trees going down and all sorts of severe weather. I am proud to say that my mount held up just fine and my panels are safe and sound. I am not with out any doubt that this little set up is ready for the long term and will serve me just fine. Ill continue to log my usage and update as needed. so far I have banked 200A and used 104A all my tools are ready to go I have basically a 300w emergency power circuit in the garage on standby and I have probably saved about a dime on my electrical bill. WOOO HOOO.


ezeisel (author)2015-06-16

This is awesome, and motivation for me to build a small one!

Being a neophyte, are there particular batteries that are better to use than others? Could I use this one from Amazon: (12v and 18ah)?

Also, how does the Amp levels of your charge controller and the Watts of the power inverter relate to the battery and the solar panels used exactly?

My goal is to create a self-contained system that has 2 110v outlets I can plug things into, like yours, but at a smaller scale (I'd hang the panel securely from my window as I don't have a lawn).

MoTinkerGNome (author)ezeisel2015-06-16

ezeisel, Thanks for the comments and the great questions.

To size a system one has to figure out how much load they want to run and for how long. Watts = Amps x Volts. It has been my experience with my system so far that for a 100W AC load ( 100 watts = .83 amps x 120 volts) My inverter draws about 10 A DC at 12V or 120 W DC due to inefficiencies.

With those calculations the above 18 Ah Battery that you listed would last for about 1 hour 30 minutes. But it would exceed the C rate for that battery.

To determine the Columb (C) rate of what you can safely charge or discharge; Divide the capacity 18 A by 12 Volts to receive the Columb Rate of 1.5 Amp/hours charge/discharge that would be a 1C rate with a lead acid battery you do not want to usually exceed this number unless the manufacture specifies otherwise. This may cause some confusion as my battery bank is a 60 amp hours of capacity, but they are designed for rapid discharge and their C rate is 20 Amps

Suppose that battery can only support a 1C charge/discharge rate you would be able to run a 18W 12v load or charge it with a 15w 12V panel. If you receive about 5 hours of good insolation (sunshine) every day most of North America in the summer receives 4-5 hours.

You would multiply The hours of sunlight by the wattage of the panel to receive the watt hours collected per day. 5 hours x 15 Watts = 75 Watt hours / 12V = 6.25 = 3-4 good days of sunshine to bring the battery back up to full.

So to start Figure out how much of a load you want to run and for how long and then size up from there.

FYI in the time that I have had my set up running the panels have collected 70 Amp / hours 12V DC, and My loads have resulted in 25 Amp hours @ 12v

Another FYI a 12v battery is considered fully charged at 13.8 and fully discharged at 10.8VDC Most of the time you dont want to discharge the battery below 50% unless it is a true deep cycle battery. If it lists CCA then it is a starting battery and they will get killed pretty darn quick.

SunZilla (author)2015-10-14

Nice project! Thanks for sharing.

basicdave (author)2015-07-21

Such a Great post! Thank you for that!

If you have never seen it here is a really great tool put out by the National Renewable Energy Lab. It gives you a monthly breakdown of production based on location.

MoTinkerGNome (author)basicdave2015-07-21

Thanks Basicdave.

I was not aware of that calculator Given my location and costs I will generate 290KWH/year if I did looked that up correctly.

jayjay_jayem (author)2015-06-28

hi there, very nice post, but because I am a neophyte in solar stuff, I wonder if you could show me a computation or,much better, a complete specs if I consume 90-100 Kilowatt per month. I just need the solar installation for my submersible pump, refrigerator,a TV, and occasionally, an aircon. thanks!

Jay Jay, The solar isn't that difficult however I am not that well versed with UK electrical practices. If you are looking to go completely off grid with no mains power the most expensive part will be the storage.

Now if you go Grid inter tie you will not have the expense of the storage batteries.

If you check out this calculator you will see that you will need about 12-15KW of solar panels.

I dont know a thing about UK electrical code or what panels would cost there but that would be about $20,000 USD for just the parts. I would really suggest you check with a local solar installer. If you can reduce your consumption then that would be less solar you would want to use.

billbillt (author)2015-06-18

Very complete!... got my votes!..

MoTinkerGNome (author)billbillt2015-06-18

Thanks bilbillt, I am flattered.

Tater Zoid (author)2015-06-18

Very impressive.

MoTinkerGNome (author)Tater Zoid2015-06-18

Thank you Tater, It was just one of those things that I have been wanting to do for a long time.

madashell13 (author)2015-06-15

Very nice. Length was not bad considering the information. Liked the amount of detail given in areas that most neglect. I have a very similar system with homemade panels ready to go online if the rain will ever cooperate. Nice instructable, keep up the good work!!!

Thank you I would love to see pictures of your set up, I was pretty much shooting through holes in the rain my self. The cool thing is that even though it has been raining off and on for several days I have collected 55 amps of power and only used 16 of those collected. I am kinda of interested to see what it will do when I finally get a full day of sunshine.

Vyger (author)2015-06-15

Hey, just a quick note on something I noticed, but I might be wrong. Whenever you use aluminum cable and especially when you connect it to copper, such as in a fuse box or a lug like yours, you need to coat the aluminum with a special anti oxidation grease. The one I have is called OX-gard. The stuff is cheap and you can get it at any hardware store. Anyway you should re do your connections and coat your cable ends. If you don't the aluminum will form an oxidation layer and will cause resistance to the power flowing. This will make the wires heat up and will waste your power. It can also cause a fire. It's the reason the use of aluminum wire for regular house wire was banned.

MoTinkerGNome (author)Vyger2015-06-16

Thank you Vyger, I appreciate ya looking out for me. I am not an electrician suppose I got so caught up with calculations on 10 gauge wire (less then 3 ft is ok for a 30 amp load before a 2% loss) that I neglected the jumper cables. I figured 4 gauge was more then enough. In retrospect I am going to cannibalize a pair of automotive booster cables and swap out the aluminum cable for copper.

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Bio: Howdy, I am a bit of a tinker gnome. I like playing with hardware/technology along with making stuff I want out of old stuff ... More »
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