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My 150 Watt Solar Power System

By Tim Mitchell aka WooferHound

Huntsville Alabama U.S.A.

In the beginning

-- The System --

I have a small solar power system that has been in operation since October 2007. It was a very minimum system based on the Harbor Freight 45 watt solar kit. This system charges a 12 volt battery and I use the DC power straight off the battery without using an inverter. It's simple but very functional running: Lights, DSL Modem, Fan, TV/Radio from it and it's been working great.

This is a great example to beginners on how easy and cheap it is to get started setting up their own decent Solar power system.

I have made many improvements over the last year, allowing me to add more solar panels and a Wind generator to the system. When I first Put everything together I was buying the 45 watt solar power kits from Harbor Freight I used the Panel Mounts that came with the Harbor Freight solar panels and just set the three original solar panels down on the ground.

The Black pipe that you see is a Solar Pool Heater.

Panel Mount

-- Adjustable Panel Frame --

I made a frame for the panels out of 2x4 wood studs, painted it with outdoor Primer and screwed it together with 3 inch (75mm) screws. Then I made a separate Foundation Framework and screwed it down to the top of the shed. The last step was to connect the Panel Frame to the Foundation at the front using hinges. I can tilt the entire set of solar panels up and down for Summer & Winter settings. No kind of tracking here, just seasonal adjustment. You may notice that it is exactly big enough to hold 3 more Harbor freight panels.

The front of the shed faces directly South but my house rises fairly high just to the East of my shed. It's not a bother in the Summer and the panels are never shaded. However in the Winter the panels don't get Sun till after 11:AM in the morning so the tilt of the shed roof points the panels to more open sky in the Winter. I have the angle temporarily set using the Unpainted Woodblocks. I want to make some kind of system that will easy set it for Summer or Winter Sun angles. I haven't quite figured this part out yet. I think I'll mount with hinges, some long pieces of wood that will open up and stand the Frame up for Winter, then fold down with woodblocks on the back of that, setting it to Summer Sun. Then I'm thinking about holding it down with Bungee Cords so the wind can't flip it over.

Christmas 2008 my mom gave me another set of Harbor Freight Panels. Now I have double the power coming in. Here are all six Harbor Freight panels on the adjustable mount set to the Winter position.

In 2011 I added 3 more panels for a total of 9 panels bringing the possible wattage up to about 150 watts

Solar panels

I have made up a chart for myself so I can properly adjust the panels for best seasonal output. I've decided to adjust the panels 4 times a year for best output. Using this chart as listed, the panels will not be more than 1 month from directly facing the Sun. I'll explain the four lines of text relating to each readjustment.

Move Date - This is the date that you would actually move the panel to it's new position
Duration - Length of time the panel will remain in this position
Set Date - The panel should be adjusted to directly face the Sun on this date
Season - The season of the year, needs to be reversed for the Southern Hemisphere

Solar Panel Angle Set Chart

Move Date - February 21
Duration - 2 Months
Set Date - March 21 or September 21
Season - Spring

Move Date - April 21
Duration - 4 Months
Set Dates - May 21 or July 21
Season - Summer

Move Date - August 21
Duration - 2 Months
Set Date - September 21 or March 21
Season - Fall

Move Date - October 21
Duration - 4 Months
Set Dates - November 21 or January 21
Season - Winter

Diode Isolation Panel

-- Diode Isolated Combiner --

It's good to isolate solar panels from the battery through Blocking Diodes. I built a Diode Isolated Input Panel for all my Renewable Energy power inputs. It provides terminal strip inputs for up to 10 Solar Panels, two phases of my Wind Generator, and an Auxiliary Input for some other experiments I want to play with. This is a picture of the unit wired to my new Fused Power Distribution Panel on the left.

The brown circuit board on the left of the unit has the 10 heatsinked diodes for the 10 solar panel inputs. I got the diodes from the user Ghurd on Fieldlines.com, they are Schottky Rectifiers rated at 45v 10a with a low voltage drop of .4 volt. The way it's wired, I can put ten 60watt panels on it for a max total of 600 watts Solar.

On the lower right of the brown circuit card is a Diode Bridge made from four 1000volt 6amp diodes. I used High voltage diodes because i don't know what I will connect to this experimental Auxiliary Power Input, could be used for my Stepper Motor Farm or from other sources I haven't thought of yet.

Two Bridge rectifiers for my 2 phase Wind Generator are on the lower right-side of the unit. They will be handling about 125watts each and are rated at 80v 12amps. The rectifiers are mounted to decent sized heatsinks which in turn are bolted flat to the chassis for additional cooling.

Two Batteries

-- The Batteries --

I had a good week at work and enough extra cash to get new batteries for my solar power system. I was going to go to Costco and get some cheap Golf Cart batteries from there. But I went to my favorite little battery store and found them selling new Trojan T-105 batteries off of a pallet for $118 each. I couldn't resist and I bought two for my 12 volt system at a cost of $254 dollars tax and all. I eagerly got them home and connected to the system.

These are 6 volt Golfcart batteries, so 2 of them are wired in series to make 12 volts DC. These batteries are rated at 225 amphours so both of them together make 12 volts at 225 amphours.

Dump Controller

-- Charge Controller --

I am using a Dump Load controller to keep the batteries from overcharging. It works by diverting any excess voltage from the battery and into resisters making heat.

This is my 2 stage Dump controller that I built and installed. It has 2 separate Ghurd Controller Modules in it. The first stage can be set to start dumping at 14.5 volts, while the second stage can be set higher to start dumping at 14.7 volts. This makes it easier on the battery as large dump loads are not used until there is a large amount of power to dump. The resistors are hanging on 3/8inch threaded rod with little heatsinks made from big fender washers. The threaded rod is bolted tightly to the chassis which makes an it into an even bigger heatsink. The top row of resistors is Stage 1 and the 2nd and 3rd rows are Stage 2. The 12volt fan only operates when any of the 2 stages are dumping.

The fan gets it's power through 2 isolation diodes that charge the Big Blue 10000mfd capacitor on the lower right. If any one of the 2 stages pulses a dump voltage to the resistors, it also pulses the capacitor through an isolation diode, which charges up the 10000mfd capacitor and can keep the fan running for about 5 or 8 seconds. The the diode isolates the capacitor from the resistors preventing the capacitor from discharging back through the resistors. The ghurd dump controller can be set for a wide hysteresis range and I have mine set for .01 volt. Set that way the controller can pulse dumps quite rapidly. It is rare to see it pulsing dumps more than 1 second apart. I usually see the dump pulses running faster than 10 times a second, but it can easy be so fast that the dump light appears to stay on continuously.

There has been some discussion about how bad it is to charge a capacitor Hard
like this in the first few dump pulses that may be more than 5 seconds apart,
but I have never heard of any actual problems doing this, plus this is a fairly high quality cap.

Solar panels

I also made each dump stage adjustable with switches. Stage 1 can be set to dump at 3 or 6 amps, while stage 2 is settable to 6 or 12 amps dump. At this time I have everything set to minimum since I only have 3amps coming in right now, but I can really grow into some more Solar Panels and other RE inputs easily. I included On/Off switches on each stage too. This will let me operate the unit on either stage independently or turn them both off for Battery Equalization. The dump indicator LEDs are here also, plus there are LED outputs on the terminal strips for some dump indicators inside where I'm using the power at.

This has worked perfectly since the moment I installed it and switched it on. Of course I had to do some minor tweaking to get the 2 stages dumping at the correct voltages, but all the functions work just fine. When I switch between High & Low amp dump settings, the LED flashrate does not change, but the On-Duration changes. The cooling fan (.14 amp) will run usably for about 5 seconds after each dump pulse and the whole thing runs cool enough to touch, even directly touching the resistors that are continuously dumping. As I add more power inputs I will need to watch and see how hot it gets. it's max dumping ability is about 300 watts at 18 amps.

Here is a link to Ghurds Dump Load Controller kit, I highly recommend it.

Battery Fuse Panel

-- Fused Battery Connections --

I built a really nice Fused Power Distribution Panel for anything that connects to the batteries. In fact "this is the battery" and anything that I hook to the battery will make it's connection here. It is wired entirely with 12 gauge wire. Each Individual input from the battery to it's fuse is a separate 12ga wire. It is constructed in a chassis from an old Radio Shack burglar alarm system. In the picture below, it is installed and operational right next to My Ghurd Dump load and controller.

There are only 4 negative terminals on the strip. Each terminal has two 12 gauge wires going to the battery which is hard to see in the picture. There are 8 numbered Input/Outputs. They They are connected as follows...
1 - (Future) maybe a voltage sensing circuit
2 - (Future) Maybe an output for some lighting around my nearby pool
3 - Output 1 is a 12ga wire to the house- 10amp fuse
4 - Output 2 another 12ga wire to the house- 10amp fuse
5 - Input From Solar Panel Diode Combiner- 10 amp fuse
6 - (Future) Input from Wind Turbine generator
7 - Ghurd Dump Load power connection- 15amp fuse
8 - Dump Load Voltage sense line- 3 amp fuse

Charging System

-- Battery, Control and Distribution --

Here is a picture of the charging system all put together out in the shed that the solar panels are on. The power wire to the house is buried about 15 feet between the shed and the house.

Wire around the house

-- Getting the Power to the House --

The 110 foot (33m) Wire goes from the battery, around the house, to my computer room, which is where I use the 12volt power. Originally the wire was two 12ga positive wires and a single 12ga negative wire. I have added another 12ga negative wire. Now there are two 12ga wires on both the positive and negative side. Two 12ga wires equal 9ga wire. They are fused for a max of 20 amps even though the wiring should be good for 40 amps.

Fused Output Panel

-- Fused Distribution Panel --

I recently installed more solar panels so I needed to expand so I could use the extra power. Until now I had been distributing the power using a Switch Box with a terminal strip output, but that wasn't good enough anymore.

So I built this Power Distribution Box to give me multiple fused outputs to my different loads. This is mounted under my desk below my computer monitor. You can see the four 12 gauge wires coming from the battery into a terminal strip on the lower Righthand side. These 4 wires are then paralleled across two 24000mfd 50v capacitors. After that the Positive wires go through a 4 position Fuse Block and then I have provided 4 fused outputs on a Terminal strip. This box has made it incredibly easy to attach or try different loads on the 12vdc outputs, not to mention having the safety of the fuses now.

The Capacitors are to prevent power surges on the long 12 volt line to the battery by providing a little local power storage at the point where I'm using the power at. When I originally installed My Solar Power I had 2 lights, a fan and my DSL modem hooked up to the 4 original power switches. I discovered that If the modem was on, and then I switched anything else on, the modem would Reset itself. So I installed a 20000mfd capacitor in the switchbox and the Reset problem disappeared. When I built this power box I increased the value to 48000mfd since I had the capacitors and I'm adding more loads.

Switch Panel

-- Using The Solar Power --

I'm using this switch panel to operate most of my solar powered items. The yellow LED is on if any of the switches is on to indicate power is being used from the battery. The 2 green LEDs are indicator lights for the 2 levels of Dump Control provided by my charge controller. The red switch turns on a meter to show me the battery voltage.

I am using the 12 to 15 volt DC power for many things.
Five 12vdc 5 watt fluorescent lights - Cable Modem and Router
12 volt DC TV and Radio - Muffin fan for personal comfort in the Summer
Cell Phone Charging and Household Wireless phones,
Digital TV converter box, plus more

Solar panels

Another fused output goes to a second switchbox I made just for the room,lighting. I mounted this box out in the open on a corner of my desk so other people could easily see and use them. The lights I'm using are from the Harbor Freight solar kit and the ones you can get at Home Depot or Wal-Mart that run on 12vdc.

Also inside of this switchbox is a 9 Volt Regulator screwed to the box itself for heatsinking. This regulator is wired to the Charging Station for the Cordless phone in the picture, and a police scanner that runs on 9vdc.

Cigarette lighter outlets

I bought this on eBay from HongKong for $6.oo shipped. It has 3 Car Cigarette Lighter Sockets and a 5vdc USB Charger output on it. This is extremely versatile allowing me to power up many items already made to work in cars. Right now I have a CB Radio plugged into a 12 volt socket and my cell phone is being charged off of the USB outlet.

12 volt stuff

Voltage Check Meter
Cable Modem
TV / Radio

-- I am not doing this to save money on my power bill --

Power from The Grid in my area is cheap, about 10cents per Killowatt hour. It is very difficult to make your own power cheaper than that price, In fact you would find that making your own power is double or more the cost of buying power from the grid. It can easily cost 5 times the cost of grid power. Making your own power costs so much because of the price of solar panels and wind generators is expensive. Then to do the job right you will need lots of expensive batteries, and they need replacing every 8 or 10 years. There are only 3 good reasons to use Renewable Energy.

Remote Power - You need to have power where grid power is not available
Backup Power - You need power for the emergencies when the grid power goes off
Hobby Power - You are interested in making power and possibly helping the environment

I fall into the Hobby category with the added benefit of having Backup Power. I do save about $3.oo a month on my power bill, or about $35 a year. But I just bought $250 worth of batteries and I paid about $600 on my system so far. That is cheap too since I actually built and put the thing together myself. We had a 5 day power outage in April 2011 when Tornadoes came through. I had Lights, TV/Radio/CD Player, Fans and cell phone Charger. At that point I considered my system to be priceless.

I learned almost everything I know from Message Forums and the help provided by other people that are living off of solar and wind power. I am a moderator on http://www.anotherpower.com/forum/. Those are some really smart people over there and can answer any Renewable Energy question you may have. You can also visit a few more excellent sites for Do It Yourself solar and wind power, expert advice and plans...
http://otherpower.com/ and their companion Message Forum http://fieldlines.com/

The cheapest place I know to get solar panels is http://www.sunelec.com/index.php but I hear they don't have good customer Service.

As you can see I am having Too Much Fun . . .

but now I need some more Solar Panels

If you have any questions or comments about my system then just send an E-Mail to timmythy@mindspring.com.

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Tim's Home Page / timmythy@mindspring.com / Created: January 2012