Home Built Solar Power System




Introduction: Home Built Solar Power System

Hi. I've been interested in renewables for a while now. Our society can't continue to work on oil, and with rising gas prices and more frequent power outages, solar energy seems to be the way to go. The main problem that inspired me to make this system comes from my love of technology. When my iPhone and laptop run out of juice, my life becomes very primitive. With the goal of keeping all my electronics up and running no matter what the weather and grid status is the main reason I made this system and instructable. This is my system and how it functions. I'll start with the original setup and show how it has evolved over time.

Step 1: The Original Setup

My original setup started off with a 10 watt panel I built myself from some cells I found off of eBay. These were the tougher CIGS cells rather than monocrystalline or polycrystalline. The cell was originally rated at 15 watts but because of all the inefficient soldered connections (I wasn't that great at soldering yet), it made about 10 watts. Each black square is one cell that makes approx. 5 volts. The voltage was combined in series to create around 20 volts, and then the amperage was adjusted with wiring the strings of 20 volts into parallel. I'm not really going to go in a crazy amount of detail because this is explained on hundreds of other instructables. This amount of power is ideal for maybe some DC lights and charging cell phones. It's not nearly enough for even my laptop. The inverter would whine and the adapter on my laptop would begin to buzz. Probably not a good sign!
*Note* The third picture to this step is a quickly drawn schematic of how everythig in this system currently works. It will help with trying to understand the basic function of the system if you are new to solar for simplicity. I'll try to include a schematic after every major change to clarify.

Step 2: The First Battery and Electronics System

The original electronics consisted of an old 12v marine battery that I repurposed, a Coleman Air C60 charge controller, and a 400 watt inverter. That was all  I needed to manage the battery and keep it from overcharging.

If you are new to solar power and how it works, the charge controller is a device (usually microprocessor controlled) that regulates the charging on the battery. When the battery becomes completely full, it is designed to stop most electricity from going into the battery. Without a charge controller, the battery would eventually boil out and become ruined.

If you are extremely new to solar, you might wonder why there's a battery. Even though it's possible to run loads without a battery, they would shut down every time the sun goes behind a cloud. The battery is there to make sure there is a stable, clean stream of power to your loads. Also, it can store electricity for night, as I have it do.

 Be sure to look at the highlighted notes on the pictures for more information.

Step 3: Adding a 15 Watt Solar Panel

With my interest sparked again by a friend also interested in solar, I went online and purchased a northern tool 15 watt panel. The frame was a paint to install, but once attatched I immidiately noticed the battery voltage shooting up and the charge controller having to regulate the current constantly. Also, my inverter stopped yelling at me for charging my laptop, but it still would drain the battery pretty fast. Interesting what a difference 15 watts makes!

Step 4: A New Battery

The original battery decided to go fast. Leaving a cell phone on the charger overnight would drain it down to the 11 volt range. I could see how this would never last. Tractor Supply had a good deal on commercial batteries, which are a combination of deep-cycle and starting. I would recommend getting straight out deep cycle, though, because of their better efficiency. Deep cycle batteries are designed for (as the name implies) deep cycling: draining the battery significantly. They have much wider lead plates that can resist the chemical abuse of the acid. Starting batteries have thin plates that can release a lot of energy quickly. This thin of a plate can never sustain the chemical abuse of deep cycling. So deep cycle is the way to go, starting batteries won't last long. Commercial works well, too, though. This battery is flooded, meaning I have to add distilled water every now and then. It's really not a hardship, though. Equalization occurs every few months and keeps the battery very healthy.

While on the topic of batteries, I would like to explain the PROPER way to read a battery's charge. The voltage of the battery IS NOT the best way to determinte state of charge (soc). A battery's voltage can swing all over the place, and is most accurate after resting for 4 hours without a load or charge. Rarely does this occur. The BEST way to read a flooded battery is by inserting a hydrometer in a cap and reading the gravity. The most common is amp meters that use a shunt to measure how much goes in and out.

Step 5: The BIG Panel!!!!

After a few months of toying with solar, I decided to get serious. One of the top loads I wanted the system to run was a backup sump pump which ran off of 12v. This, of course, can easily draw over 100 watts at a time. The system wouldn't be able to keep up with the pump and would eventually stop altogether, flooding the basement. The solution to all my problems was to get a bigger panel. This one is made by UL Solar and is rated for 100 watts.

Mounting the panel proved to be difficult. Instead of on the ground where I could easily monitor and maintain the panels, I decided to install this one on the roof for better solar exposure. As you can see in the third pic, it is conveniently right on the edge of the roof,  reducing my wire run and potential losses. The 12 gauge wire is specifically made for low (10 - 30) voltage, so my 12 volt system fit right into that, even with the panel producing 23 volts open circuit.

Step 6: Upgrading the Charge Controller

My original controller (the Coleman Air C60 found on the second step) was not very successful with the new solar panel. Since it uses an on/off relay, it will connect the panels to the battery, and the voltage of the battery would shoot up because of all the juice coming in. The voltage would rise up to the battery trip point, then shoot back down again as the relay began "dumping" the power. So basically, only 1/3 of the available power I get every day actually goes to the battery, the other gets dumped even though the battery wasn't full. I decided that the current charge controller had to go.


I decided on a Xantrex C35 charge controller online. The C35 is a unique controller because it offers 3-stage charging, plus PWM charging. When the sun comes up, the battery is usually sitting at a happy 12.4 volts or so. That's fine with me. It's not discharged too much, and it could sit like that for days. As soon as the panel starts sending power, the C35 will "boot up" and begin charging the battery in "bulk" mode. Bulk mode tries to charge the battery as fast as possible by giving it as  much voltage and amperage the panel will give out. It does this until the voltage hits about 14.8 volts. When it gets there, the controller switches to the "absortion" stage. In this stage, the battery charges more slowly by limiting amperage, not voltage. Then, after it holds that voltage for approx. one hour, it switches to float mode, where the battery is considered fully charged. This keeps it at 14.0 volts until I use the power or the sun goes down. If I start using the power while the controller is in float mode, it will automatically adjust the current to account for the load!

Step 7: Upgrading the Alt-E Power Board

The original setup inside the basement was a patched together mess. It had stuff everywhere, wires crossing everywhere, and everything delicately balancing on the battery as if at any moment it might slip and short (which had happened a couple times). Obviously, a fire was going to be inevitable. With that in mind I designed a vertical board where I could mount all the electronics and some bus bars. The battery would sit on the cool basement floor where the temperature would increase efficiency. IT IS A MYTH THAT BATTERIES WILL DRAIN ON A CEMENT FLOOR! All batteries will lose energy over time, but a battery doesn't care what it's sitting on.

To start, I needed a board. That was accomplished with some spare wood (first picture).

Then, the electronics would need to be mounted (second).

The new addition of the bus bar helps prevent a short circuit. It's hard to see from this picture, but there is a layer of plexiglass on top of the whole thing. This prevents anything from crossing the two. It hopefully is obvious which side is positive and which is negative. Again, way overdone but better safe than sorry.

Step 8: The Finished System (for Now)

After all of the upgrades and designs, the system is close to finished (for now). I plan on adding another battery to help keep  the voltage steady under load and add a backup sump pump. For now, though, the system charges all of our cell phones, my laptop, and some lights. Updates will continue with this instructable as more stuff is added, so check back now and then for any updates!

Step 9: Adding Another Battery

Update 5/9/12:

I know I had mentioned this in my previous post, but now I actually made a move on it. The problem with my system right now is that the battery is too small for the amount of panels I have pumping juice into. By 9:00 AM the next morning, that battery is fully charged. I'd like to run more stuff at night to pull down the battery down more, but I'm limited because of the lack of capacity. Running cell phones and lights at night was enough to drain the battery, but not enough that the panels couldn't recharge it easily the next day.

Note: Even though I could continue to use the system like this, I would be wasting valuable sunlight hours where the battery is full and I have no need for the power. Really counts when I need the power and don't have any, plus I'm kicking myself at night when I have to shut down loads while I sat and watched the power go to waste all day.

The new battery is at 86 a.h. compared to the previous 104 a.h. battery I got earlier. That's a total of 190 amp hours for those of you who can't do math in their heads. BECAUSE a battery should never be discharged below 50%, I basically have 95 amp hours to play with. Still, this is significantly more than the 52 I had before. I still would like to purchase more batteries, so I will still continue searching for good deals.

Step 10: Outdoor Lighting

Last Christmas (2011), I had decided to run some Christmas lights through solar. We live a ways out of town, so it doesn't justify to pay a huge monthly bill for some dinky lights that only a handful of people will see. Still, though, it helped brighten up our road and my neighbors were inspired to put up Christmas lights, too. How I eventually decided to run the Christmas lights was via a 400 watt inverter with one of those timers plugged into it. The lights would turn on at about 6, then off in two hours. Using all LED lights, my light consumption totaled to be around 30 watts. However, with the inverter working full time, I actually consumed about 50 watts. Not that the system can't handle this, but such a loss in winter really made a difference. We had limited sun hours and some days with just no sun.

Having so much fun with those lights, this summer (2012) I decided to put up some path lighting outside just for fun. I searched specifically for 12v LED lights (which is extremely important, or else you're wasting energy), and found some at home depot. When they arrived by mail, I cut the wire from the transformer and wired it directly into the battery. I then ran a 60 foot 14 ga. wire from my battery bank to the front of the house, where there were two holes drilled for my wires to go through. From there, each light was connected.

The problem with these lights was the amount of control on my part. Every time I wanted to turn the lights on, I'd have to run down into the basement, connect the wires, and then do the opposite in the morning. REALLY A PAIN. And if I forget, there goes 120 precious watt-hours.

I finally decided to connect my 10 watt panel to a relay, so at night when the panel stopped giving out anything the relay would click and the lights would come on. This didn't work too well considering that whenever a cloud passed the lights would go on. The ultimate solution to this problem is found on the next slide.

Step 11: A Lighting Controller

My very first charge controller from step 2 on this instructable had finally quit (NOT THE XANTREX C35!!!). It wasn't a very good design to begin with, and only looked at battery voltage. As I had explained earlier, the voltage would rise under charge, and it would assume the battery was full while it was instead just charging. I finally unbolted it from the board and threw it in a box. I took the 15 watts of power it was handling and wired it directly into the bus bars. The system still worked fine, but the other controller got "confused" on why the voltage was rising while it wasn't putting much into it. The solution that fixed my lighting problem and my charge controller problem was a charge controller with lighting control. The one I picked was a Xantrex C12. I have had a very good experience with their products, so I decided to give them another go. Turns out this controller is a PAIN to wire up. The terminals on it are so small and close, I'm constantly afraid it's going to short out any minute now. Good thing theres fuses. Anyways, after 2 days, I finally got it working.

When the sun comes up, the controller senses it by the power coming in from the panel. It then shuts off all outdoor lighting and begins sending and regulating power from the panel to the batteries. When night finally arrives, it waits 60 seconds after the panel voltage drops below 3 volts, then blink! and the lights come on all night (or whatever amount of time I want them on). Very nifty and automatic! Also automatically adjusts throughout the year as the sunrise and sunset times differ.

JUST TO MAKE SURE I AM COMPLETELY CLEAR, THE XANTREX C35 IS WORKING TOGETHER WITH THE C12. The only controller that was replaced was the original coleman air.

Step 12: Update: the Complete System Diagram

After many comments (Thanks everyone!) I have made this drawing to try and clarify why I have two charge controllers. The 10 watt panel I built now runs some basic DC things by the garden (radio).

The 15 watt panel is connected to the C12 and is the "photocell" for the lighting control. During the day, however, it regulates the power to the battery just like any other charge controller would. At night, it stops sending power to the battery and begins doing just the opposite. The 100 watt panel (and any future panels will be) is connected to the C35 due to its higher capacity.

In the picture, all the red dots indicate a fuse. There are a few more for the inverter and elsewhere, but these are the basics.

Step 13: Using My Power!!!

So now that I have all this solar power available, why not use it even when the grid is up? In fact, most of the power I make is inverted and used to power my everyday electronics (my laptop, monitor, fishtank light) and some other appliances that we all use regularly (vacuum). Since installation, my system has generated approximately 119 KwH. As the system expands, this number is expected to jump into the thousands. Stay tuned, and comment on any ideas or advice! Also, vote for me in the Green Tech contest! Thanks!

As a side note, this ENTIRE instructable, from the pictures to the internet connection, were all powered via solar! Thanks for using a bit of solar energy just by looking at my instructable!

Step 14: Backup Sump Pump

This has been mentioned several times before, but I have now added a backup sump pump ran entirely off of solar. The pump is a Wayne ESP25 backup pump rated at 3300 GPH. I looked at the Basement Watchdog and other pumps, but after many reviews I chose the ESP25. A note on the Basement watchdog: it's all PLASTIC. The ESP25 is all METAL. You tell me which will most likely be better. Hooking it up was a real pain because our sump pit is so tight. I'm no plumber, that's for sure. Anyways, the pump came with its own battery box, so off to the store to get another battery. It is EXTREMELY similar to the one in step 9 except for the company logo. Other than that it's literally the same model. So now, my battery bank has 276 amp-hours of energy at my disposal. The pump can run 7.5 hours continuously at 75 a.h., so at 276, that's 27.6 hours of CONTINUOUS run time. While testing, I noticed it only runs about 15 seconds per minute, so that makes it about 4 days of running if it ran 15 seconds every minute without any solar input. SINCE there's always going to be some solar input despite cloudy conditions, I'm looking at an estimated unlimited run time.

The video below shows a test on what would happen if the main pump fails for whatever reason.

Step 15: Living Off the Grid and Installing New Data Monitoring Equipment

January 2013 was our first major power outage of the year. It was a partly-cloudy day after a very breezy night that knoked out the power lines. No problem for me, though. While our neighbors pulled out their generator, I simply grabbed some extension cords. From the 400 watt inverter, I was able to charge cell phones, iPods, iPads, laptops, and also power our DSL modem for Internet. At the end of the day, who doesn't like to watch some TV? No problem for me. I used a 40 inch LED tv that drew about 60 watts. The batteries had no trouble keeping it powered until I wanted to go to bed. Overall, I was very impressed with the system performance. It served all the needs I wanted it to. Maybe next time I'll look into our washing machine. Who knows?

Now, the next order of business. I recently installed a pentametric battery monitor system specifically designed for renewable energy systems. Basically, there are two shunts. One is positioned between the 100 watt array and the batteries, while the other one is located between the bus bars in the batteries. They measure amperage and voltage throughout the system. Both shunts connect to the pentametric input unit, which is just a computer that logs and tracks all this data. From there, I purchased the Ethernet unit. It runs from the system all the way to my router. Any computer in the house can instantly access all system data live, or review and save logged data for analysis. The system has since changed the way I see how much energy I use, and how much I really have to work with. Prior to installing this, I had no idea how full the batteries were, while knowing not to take them below 50%. Even during power outages, the batterie never seemed to go below about 80% full. Works for me. I'll try to upload some of the excel data files and some screenshots.

i think it's also VERY VERY VERY IMPORTANT for me to say that the PENTAMETRIC IS MADE IN AMERICA! I will chose an American company any day regardless of cost. The company that builds them is in Boulder Creek, California and what they make is very high quality. 

Note: I am not affiliated with any company in any way. 

***UPDATE AUGUST 2013***

I'm finally attatching a GIANT spreadsheet of the data my pentametric has gathered over the past few months (March to be exact). Each "reading" takes place every 15 minutes and is stored on the pentametric's internal memory until I upload it to a computer. The internal memory only lasts about 6 days before I'm out of room and it begins to rewrite over some of the old data. Because of this, there are a few gaps in the data readings, but it's still a very accurate summary of what happens over the course of a typical day. Being a techy person, I wrote a program in java that takes my spreadsheet and calculates all sorts of data from it. The results are below:

System summary
Created 08/23/2013
File used for analysis: solarData.txt

System data:

Average battery volts: 12.860747758760798
Average solar Amp-hours: 0.0
Average % full: 96.76894865525672%
Battery is full 15.678484107579463% of the time
Minimum voltage ever recorded in this data series: 11.6 volts. Date recorded was: 7/19/2013
Maximum voltage ever recorded in this data series: 15.5 votls. Date recorded was: 3/10/2013

Equalization records:

3/10/2013: System voltage is 15.1
3/10/2013: System voltage is 15.4
3/10/2013: System voltage is 15.5
3/10/2013: System voltage is 15.3

Since data recording began on 3/5/2013,

Total solar production to date: 17.60 KwH

This amount of electricity costs approx. $2.82

The KwH production isn't exactly accurate since there are gaps in the data, but it's something I can live with.

Being that the pentametric is connected to my router (and therefore the internet), I'm currently looking for ways to make its data accessible to all of you on the internet. The best way is to download the pentametric software (http://bogartengineering.com/support/software Use the PMCOMM 2 beta. It's a lot simpler. However, it's not digitally signed so your computer may not be too fond of it).

After opening the program, click manage sites. Then, under connection type, click the TCP/IP (Ethernet) button. Under host, type pentametric.no-ip.biz and then make sure the port number under that is 1701. After that, click test connection, and if it says it's successful, congrats! You're connected to my pentametric. Click OK and then start under the live display option. Live data will then fill up the remaining gaps. If it doesn't work, it means that
1.) The internet is down on my end
2.) My hostname's IP is invalid (updates every four minutes)
3.) Too many users are using the live data feature.

The only solution is to wait a few minutes and try again.

I've set up firewalls to keep the connection just to the pentametric, and I'm just trying to do everyone a favor by letting them see what's up at any given time. I'd really appreciate it if you can be courteous and not try and screw everything up. It really took me a while to get it working and I'm doing it for everyone to get an idea about my electrical production. Thanks in advance.

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    1 year ago

    most of the things you used in the article are made from oil products .. even the battery


    Reply 1 year ago

    GM is moving to all electric cars, yet all the plastic in them is made from petroleum products. Almost all the metal fabricated parts are made with coal or petroleum power plants. Humans will never, EVER, be able to move to the Green, which so many think is the only way. 500,000 pounds of material must be mined, using petroleum powered vehicles, just to make one battery for an electric car. Think about that when your local government wants to outlaw the use of Natural Gas.


    5 years ago

    I used to have big problem finding effective ways to build my solar panels and maximizing my solar power.But I am getting better result now, after I stumbled upon this excellent guide I found HERE. It was a godsend. It gave me great Solar Panel tips and showed me what I was doing wrong before.


    5 years ago

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    5 years ago

    Hi there, i'm considering about building my own panel like you do by purchasing cells one by one. which one do you suggest, building from scratch or purchasing an commercial panel? is cost makes a difference?


    6 years ago

    I have made something similar, but with more solar power 245w and 140ah of batteries. The difference is I am powering the sump pump directly via inverter to the sump pump all the time 24/7.

    You need to keep an eye on battery voltages as mine will drop down to 12.4v even on the rainy days. I would like to see battery voltages to be maintained at 12.7v or above. Our sump pump draws 560w every times it runs, which usually runs for a bout 7 seconds.

    I must of spent over $500 for everything on mine, and will be adding at least another 200w of panels shortly


    6 years ago

    Very well done. I too am going to move my toolbox solar generator to a wall mount system as it grows. I'm planning to go from a single 100 watt panel to four. I'd also like (2) 125ah batteries.


    6 years ago

    Nice set-up for a home made DIY solar energy kit. I know some people aren't big on building the parts themselves, there are some good tier 1 products you can get and use for a plug n' play solar power system.



    6 years ago on Step 7

    Battery on concrete? Actually its more to do with temperature
    differences during charging and discharging I think . Concrete is cold
    and stays that way holding the base of the battery cold too. The heat
    though moves to the top by convection and during charging the top gets
    hotter. Stress cracks and warps the plates. It protects your battery too if you sit it on a plastic tray on top of a sheet of some sort of insulation. You will need to hose off battery tops from time to time and a tray catches spent/spilt acid . Try leaving a gal nail or two on top and you well see what I mean.


    Reply 6 years ago on Step 7

    And use copper impregnated anti sieze grease all over the terminals if you want them trouble free. If corroded then pour boiling water over the tops to clean up terminals and connectors then grease.


    6 years ago on Introduction


    I have a solar panel of 12watt. 16v DC. I am using it with PWM invertor of 55watt to charge the battery of 12v 7ah. But it cannot run a fan with AC motor. Please suggest what needs to be done.

    Fan is of 45-50watt.


    7 years ago on Introduction

    Impressive system! I'm curious how much is the total cost? This is nice for off the grid, but I'm thinking about buying a simple on-grid plug-in system. It seems to be the easiest way to offset your usage with solar. Lots of info here: http://www.pluginsolar.org/


    7 years ago

    I was wondering I am looking to build a solar charger to charge maybe my devices while also having a little bit of battery storage so far I have about 20-30 .518 volt at 4.01 amp solar cells what would I need to complete this project?

    I think you'll find that it is better for a sump pump to be run less frequently, for a longer time... In other words, rather than 15 seconds per minute, 45 seconds for 3 minutes would be less damaging to the pump.... The constant starting/stopping is what's really bad for the motor..... I have one pump that usually runs (as is rated to run) continuously, because it recirculates a fish pond in the yard... But, if it's just for de-watering (drainage) in order for your pump to run longer, either the sump pit needs to be wider (but not necessarily deeper), or to have a separate long-interval float (and maybe a deeper sump).... In the last option, the pump goes into the water deeper, but the float actuates where you want it to (usually several inches or more below the floor), and the float keeps pump on until it reaches the either the top of the pump (kept submerged), or less as long as the pump stays on longer.... In any case, 15 seconds is a pretty short cycle-on time....


    7 years ago on Introduction

    Very nicely done. I didn't know at first that this is much simpler to build a solar power system. thank you very much for posting. God bless


    8 years ago on Introduction

    I lived off the grid for 26 years, using a similar setup (just a bit bigger). Now I am on the grid, and I use a small grid-tie inverter rather than voltage controllers, batteries, and inverters. It seems to be a great savings if you are on the grid. Of course, I still use my solar panels !

    Das Blade
    Das Blade

    8 years ago on Step 6

    I like this solar stuff allot. You keep updating your systems and for us novices it would be help if you placed a price tage on the new stuff you add. Doesn't have to be exact just what you paid would give us all a better idea of the cost. Thanks Grandpablabe


    8 years ago on Step 12

    In your drawing on the last slide, you show two negative wires - or circuits - with a fuse in them. Why is the negative side fused and the positive side only has the one fuse at the battery positive? Shouldn't all these fuses be in the positive run?