How to Make Any Home Appliance Into a Solar Electric Hybrid

This project is a simple and cheap way to integrate renewable energy into your home by turning your appliances into solar electric hybrids. Here is how it works. A solar panel (or any other renewable power source) charges a storage battery. A control circuit continuously monitors the battery's voltage. When the battery is fully charged, the circuit automatically turns on a power inverter and switches the appliance from running on grid power to running on the energy stored in the battery. Then when the battery's voltage drops too low, the circuit automatically switches the appliance back to grid power until the battery is recharged.

This design doesn't require any modification to the appliance or your home's electrical system. It can work with any power source that is capable of charging a 12V battery (examples: wind turbines, bike generators, etc.). But most importantly the system is scalable. This design is set up for outputs of up to 75 watts, but by swapping out parts for ones with higher power ratings you can power larger appliances or multiple smaller appliances at the same time. This lets you build a system that fits your energy needs and your budget.

I am still trying to make improvements to the design. So if you have any questions, problems or suggestions please leave a comment. I would really appreciate the feedback.

Step 1: System Overview

Here are the five basic parts of this system:

1. 12V Solar Panel (or other renewable power source)
2. 12V Rechargeable Battery
3. Control Circuit
4. 12V Power Inverter
5. Automatic Switching Circuit

When assembled, the solar panel, battery, and inverter plug into the control circuit. The automatic switching circuit plugs into the inverter and the wall outlet. Then the appliance plugs into the automatic switching circuit.

The solar panel, battery, and inverter may be purchased off-the-shelf from a variety of locations. The last two parts of the system (the control circuit and the automatic switching circuit) will need to be constructed. This is detailed in later steps.

Step 2: Choose a Solar Panel

The solar panel that I used was a 5 watt model from Harbor Freight. But you can use smaller panels or larger panels. The only difference is that the power output determines how quickly the battery will charge and how often the system will be activated. The only guideline to follow is that you don't want a panel that produces more power than you will use in a day. This would result in wasted energy.

Keep in mind that other power sources can be used in place of the solar panel. Wind and bicycle generator could also work well. They just have to be capable of charging a 12 volt battery.

Step 3: Choose a Battery

When selecting a battery you have some trade-offs to consider. Batteries are more efficient and last longer when they are charged and discharged slowly. It is also best to minimize how deeply you discharge the battery. As a result, bigger batteries will give better performance. But larger batteries are more expensive and take up more space. Deep cycle batteries are better at withstanding the regular charging and discharging experienced as part of a solar electrical system. But deep cycle batteries are also more expensive.

I am using a 7Ah battery to power a 13 watt CFL lamp for my finch aviary. This seems to work well. If you are confused about which battery to buy, it might help to consult the battery expert at your local store. They should be able to recommend a battery for your application and budget. 

Step 4: Choose a Power Inverter

The power inverter converts the output of your 12V DC battery into 120V AC that can power home electronics. I am using an 80 watt model from Harbor Freight. The most important requirement for your power inverter is that it must be capable of continuously powering the appliance(s) that you want to run. Inverters generally list their maximum power ratings in terms of both continuous and peak watts. Generally you want to stay a bit under the continuous limit to avoid excessive heating.

Step 5: Control Circuit Materials

Control Circuit Materials:
Printed Circuit Board (Radio Shack #276-170)
2 x Diode (Radio Shack #276-1103)
+5V Fixed-Voltage Regulator (Radio Shack #276-1770)
555 timer IC (Radio Shack # 276-1723)
MPS2222A NPN Transistor (Radio Shack #276-2009)
IRF510 MOSFET (Radio Shack # 276-2072)
100µF 15V Capacitor (optional)
2 x 0.1µF 15V Capacitor (optional)
2 x 10K-Ohm 15-Turn Cermet Potentiometer/Trimmer (Radio Shack #271-343)
100-Ohm Resistor (Radio Shack #271-005)
330-Ohm Resistor (Radio Shack #271-012)
1K-Ohm Resistor (Radio Shack #271-004)
12VDC/125VAC 10A SPDT Mini Relay (Radio Shack #275-248)
12VDC Vehicle Power Accessory Outlet (Radio Shack #270-046)
Project Enclosure (6x3x2") (Radio Shack #270-1805)
2 x bolts (1/4" or smaller)
2 x nuts (1/4" or smaller)
2 x 1/4" Fully Insulated Female Quick Disconnects (Radio Shack #64-3133)
2 ft. x 16 guage wire
Jumper Wires

Optional Charge Controller Materials:
Diode (Radio Shack #276-1103)
555 timer IC (Radio Shack # 276-1723)
0.1µF 15V Capacitor (optional)
MPS2222A NPN Transistor (Radio Shack #276-2009)
IRF510 MOSFET (Radio Shack # 276-2072)
2 x 10K-Ohm 15-Turn Cermet Potentiometer/Trimmer (Radio Shack #271-343)
100-Ohm Resistor (Radio Shack #271-005)
330-Ohm Resistor (Radio Shack #271-012)
1K-Ohm Resistor (Radio Shack #271-004)
12VDC/125VAC 10A SPDT Mini Relay (Radio Shack #275-248)

Tools:
Soldering iron and solder
Screwdriver
Multimeter
Crimping tool (for quick disconnects)
Drill and Drill Bits
Wire Strippers
Knife

Part Substitutions:
I chose these parts because they are easily accessible (most can be purchased from Radio Shack). However, all of them may be substituted for other parts with similar values. You can generally find them cheaper online. The four 10k 15-turn trimmer potentiometers may be replaced with single turn potentiometers or fixed value resistors. I chose these potentiometers because they are much easier to make fine adjustments when calibrating the circuit. The input diode can be replaced with a schottky diode for better performance. It may also be omitted if your solar panel has a built in blocking diode.

Step 6: Control Circuit Design

Basic Control Circuit Design
This circuit is a modified version of a charge controller circuit that was designed by Mike Davis (http://www.mdpub.com/555Controller/index.html). In the original circuit, a 555 timer IC was used to disconnect a battery from the solar panel when its voltage gets too high (to prevent it from over charging). In my design, the control circuit connects the battery to an inverter and an output circuit when the battery is fully charged.

Here is a brief description of how the circuit works. A 5V voltage regulator powers the 555 timer IC and sets its internal reference voltages. A pair of potentiometers (variable resistors) are set up as voltage dividers that provide a signal to the timer IC that is proportional to the battery's voltage. These signals determine the operating range of the system. As the battery's voltage rises and falls, so does the output signals of the potentiometers. When the signal at pin 6 rises above 3.3V, the output of the IC goes LOW and activates the relay through a series of transistors. When the signal at pin 2 falls below 1.6V, the output of the IC goes HIGH, which deactivates the relay. By setting the positions of the potentiometers, you determine at what voltages the battery must be to activate and deactivate the output.

Alternate Design with Charge Controller
A charge controller usually isn't required for this setup. If the output of your solar panel is small relative to the storage capacity of your battery and you are powering a device that is frequently turned on, then you generally don't need to be worried about over charging the battery. However, if you wish to use a charge controller, you may attach one between the solar panel and the control circuit. I have also provided an alternate circuit design that includes a charge controller built into the control circuit.

(A larger version of the images can be viewed by clicking on the image once to zoom in. Clicking on the image a second time takes you to the image page where you can select "ORIGINAL" for a much larger version)

Step 7: Preset the Potentiometers

Before assembling the circuit, it is a good idea to preset the potentiometers. This will prevent a lot of troubleshooting later. As indicated in the pictures, the values of the potentiometers should be set to the following:

Basic Control Circuit Design
Potentiometer connected to pin 2: 8600Ω between wiper and the positive rail, and 1400Ω between wiper and the negative rail.
Potentiometer connected to pin 6: 7200Ω between wiper and the positive rail, and 2800Ω between wiper and the negative rail.

Optional Charge Controller
Potentiometer connected to pin 2: 8700Ω between wiper and the positive rail, and 1300Ω between wiper and the negative rail.
Potentiometer connected to pin 6: 7500Ω between wiper and the positive rail, and 2500Ω between wiper and the negative rail.

These will not be the final calibrated values. These are just convenient starting locations to get you in the ball park. The final settings will depend on the specific battery that you are using and its recommended operating range. When making the final adjustments, it is helpful to use a power supply with an adjustable voltage regulator such as a LM317T (Radio Shack #276-1778). See the following step for an example. If you don't have access to an adjustable power supply it will take a bit of time tweaking the values and checking it with a multimeter while the system is in operation.

(A larger version of the images can be viewed by clicking on the image once to zoom in. Clicking on the image a second time takes you to the image page where you can select "ORIGINAL" for a much larger version)

Step 8: Control Circuit Assembly

Always prototype circuits on a breadboard before soldering them onto a printed circuit board. In my breadboard prototype, I included an adjustable voltage regulator so that I could quickly simulate the charging and discharging cycles. This makes it convenient to work out the final adjustments to the potentiometers.

If you are using the same boards that I am, you can just copy my layout. The PCB is a bit longer than it needs to be for this circuit. To trim off the excess, use a sharp knife to deeply score a line across the board through one column of holes and break it off along the line.

Step 9: Automatic Switching Circuit Materials

Automatic Switching Circuit Materials:
Project Enclosure (3x2x1") (Radio Shack #270-1801)
125VAC/10A DPDT Plug-In Relay (Radio Shack #275-217)
8 x 1/4" Fully Insulated Female Quick Disconnects (Radio Shack #64-3133)
1 full extension cord with male and female ends
1 power cord with male end only (preferably a different color than the extension cord)

Tools:
Wire Strippers
Crimping Tool (for quick disconnects)
Knife or Dremel (for cutting housing)

Step 10: Automatic Switching Circuit Design

This circuit has only one major part: a double pole double throw relay. It is wired in such a way that it will automatically switch the output whenever the inverter is powered on. To achieve this, the input line from the wall outlet is connected to the normally closed contacts and the output line going to the appliance is connected to the common contacts. Then the input line from the inverter is connected to both the coil and the normally open contacts.

When the device is inactive, your appliance will be connected to the wall outlet and powered by the grid as it normally would be. The only difference is that it is going through the relay. But when the device is activated, the inverter turns on and sends power to the normally open contacts and the coil. This switches the relay. The appliance is disconnected from the wall outlet and connected to the inverter. This is how the switching circuit will automatically switch to your renewable power source whenever it is available.

Step 11: Automatic Switching Circuit Assembly

Begin by cutting the extension cord into two pieces. The female end will be the output line where the appliance is plugged in.The male end will be the grid input line that is plugged into the wall outlet. The second power cord will be the input line that is plugged into the inverter. You may wish to select a power cord for the inverter line that is a different color than the other cords. This helps prevent mixing up the lines. You may also want to label them.

Cut a 3 inch section off the end of the inverter power cord. This will be the jumper between the coil contacts and the normally open contacts on the relay. Strip 1/2 inch of insulation from the ends of all the wires. Twist together the exposed ends of the inverter cord and the 3 inch section that you just made and crimp them into a single pair of quick disconnects as shown in the picture. Then crimp quick disconnects onto all the remaining wire ends. Connect the output line (female end of the extension cord) to the common terminals. Connect the grid input line (male end of the extension cord) to the normally closed terminals. Lastly, connect the first set of quick disconnects on the inverter input line to the coil terminals and connect the second pair quick disconnects to the normally open terminals.

Step 12: Project Housing Modifications

Solar Panel Attachment Point
The cables from my solar panel have clamps on the end. So I decided to use bolts as the attachment points on the control circuit housing. For this, I found a pair of bolts and nuts that fit the clamps. Then I drilled holes in the side of the housing that were a little smaller than the bolts and screwed the bolts into the holes. The nuts were threaded onto the bolt inside the housing. This will make the attachment point for the wires inside the housing.

Holes for Wires
Because so many quick disconnects are used on wires that go into the project enclosures, it would be inconvenient to feed the wires into the enclosures through drilled holes. Instead, I found it easier to just cut small slits in the side of the enclosure where the two halves come together. Do this for all the wires that go through the walls of the enclosures.

DC Power Outlet Hole
Drill or cut a 1 3/32" hole in the side of the housing for the control circuit. Since this is an odd size, you will probably have to drill a 1" hole and widen the hole with a file or knife. Insert the DC power outlet into the hole. If it doesn't fit tightly, you can secure it in place with glue.

Step 13: Optional Testing With a DC Power Supply

Since a system that is solar powered is most active in the middle of the day (when many people are at work), it can be inconvenient to do initial testing and observation of the system at work. To get around this, you may wish to use a DC power supply in place of the solar panel for initial testing. The simplest and cheapest way to do this is to use an DC power adapter. Find one that has a operating voltage of about 12V. The open circuit voltage (no load) will usually be a good bit higher. The exact type doesn't matter. You probably have a suitable DC power adapter lying around your house somewhere. You may wish to add a capacitor between the positive and negative terminals if the power supply doesn't have a steady output. Connect the positive wire from the power supply to the positive terminal of the control circuit and the negative wire to the negative terminal of the control circuit. This will charge the battery and fuction just as the panel would, but isn't dependent on sunlight. This can make it more convenient to montior performance and trouble shoot the initial setup.

Step 14: Finished Assembly

Be sure to test all parts of the system individually before assembling them together.

Attach the clamps from the solar panel onto the bolts on the control circuit housing. Then attach the input wires on the control circuit board to the bolts on the inside the housing and tighten the nuts to hold them in place. Attach the battery lines on the control circuit to the corresponding battery terminals. Be careful not to mix up the positive and negative wires! You probabably want to label them or color code them. Attach the output lines on the control circuit to the DC power outlet. Be sure to attach the positive wire to the center pin and the negative wire to the outer barrel. Once everything is in place, close up the housing and screw it together.

Attach the inverter by plugging it into the DC power outlet. Put the Automatic switching circuit into its housing and close it up. Then plug the inverter power cord into the inverter. Plug the appliance into the output line. If the battery was fully charged, the appliance. should be powered. Lastly, plug the wall outlet power cord into a wall outlet.

Carefully observe all the parts of the system to make sure that nothing is making any weird sounds, smells, or is catching on fire. If not, you have a functioning solar electric hybrid adapter. 

Step 15: Final Notes and Future Design Improvements

Final Notes and Warnings
The operation of this device involves regularly cutting power and switching to a second power source that may be out of phase. As a result, the output may momentarily fluctuate. This is especially true if your switching circuit uses a relay with a low activation voltage. In this case, the relay might switch before the inverter is running at full power. This momentary fluctuation is no problem for simple appliances like a lamp or fan, but may potentially cause problems for sensitive electronics. So choose your appliances carefully. I am not responsible if you fry your computer.

Future Design Improvements
The biggest problem with this design is that the device activates as soon as the battery is fully charged. This does not necessarily coincide with when the appliance is turned on. Even if no appliance is on, the relays and the inverter will still consume power. This can waste electricity if you are powering a device that is not regularly on during the day.

In a future design, I will combine the various parts of this project into a single unit that has a sensor to determine when the appliance is turned on. Only once the appliance is turned on will the control circuit activate the relays and the inverter. This will help ensure that less power is wasted.

I would also like to add something to the circuit to smooth the output of the system to avoid the power fluctuations mentioned above. This might be something as simple as adding a time delay on the switching circuit.

If you have any suggestions for improvements please leave a comment and let me know.

Comments

[suganya sekar]

if any possible to connect the solar system into normal home inverter. if it is possible means how it is?

[youcantoo]

What is the switch time for the relay?

[DIYHacksAndHowTos]

The switching time just depends on the relay that you use. I couldn't tell you the exact timing for the relays that I used but in many cases it can cause a noticeable fluctuation in the output. So this kind of design is not suitable for for sensitive electronics. I just used it to power a lamp.

[youcantoo]

Don't use car batteries for your project. They were never designed to handle the requirements of a solar or wind powered system. Yes they maybe cheaper to buy. The car battery was designed to handle the initial load of starting your car and then be charged back up. A solar/wind system does not do this. You will find a car battery will last a short period of time under these circumstances. What was cheap to buy the first time then becomes a expensive replacement cost. Consider paying more up front for a deep cycle battery. You can even buy good used deep cycle batteries like forklift or golf cart batteries. They will well out last a car battery and yu will be money ahead.

[useful1]

This seems like a setup I can use. Thank you for posting it with clear instructions.

If I understand it correctly, it seems like an always "on" setup, meaning that when the batteries are topped off, you'll use battery power. Once the battery reaches "low", it switches to the power on the mains from the electrical company.

The relay switches is what controls the path the electricity takes.

Couldn't the problem that "involves regularly cutting power and switching to a second power source that may be out of phase", be solved by adding a UPS backup after the automatic switching circuit and before the light bulb? (as shown in your diagram)

- U

[youcantoo]

Really if you are using a UPS there would be no need to have the switching circuit as the ups has it already has that sort of circuit built into it.

[DIYHacksAndHowTos]

Actually a UPS was my original concept for this project. In my original design, I took a UPS, and disabled the internal charging function by adding a diode after the battery. I set up the battery to be charged by a solar panel. Then when the battery was charged the control circuit would just cut off the grid power from the UPS and it would smoothly switch to the battery power. I decided to go with my current design because I was able to make it a little cheaper.

[useful1]

Just wanted to say, I built this system 2 months later and seems to be working great. The only part that I found frustrating was setting the value of the variable resistor on pin 2, to adjust when the control circuit switches off the relay going to the inverter.

Every time, I kept trying to test the value of pin 2 while the inverter was on, the relay would click and I could not get an accurate reading of the voltage while the system was under load. It was pretty frustrating. The only way to set the low end, was to use up the battery power until it reaches somewhere near 11V and turn the dial down until it clicked off.

But even then, I still don't know what the voltage reading is coming into pin 2.

[DIYHacksAndHowTos]

Thanks. I'm glad to hear that someone else was able to get it to work.

[orenyny]

Great project thank you! My question is if it is possible to do a hybrid that will keep the battery charged (from those 12V sources you mentioned), but if they run out (no wind and no sun) it will top of the battery from the grid.
In addition, it will be tied to the grid so if the battery is full and the solar pannel is generating electricity, it will feed into the grid, and finally, when the grid is down, use the battery (emergency).

Thanks!

[DIYHacksAndHowTos]

There are a couple of devices that are similar to your description. I grid-tie inverter would let you go directly from the solar panel to the grid without needing a battery. On the other hand, an Uninteruptible power supply would let you keep the battery charged with the grid and then use it if the grid goes out.

[TakashiMoto]

I'm not terribly good with schematics, could you post a pic of the underside of the control circuit board please?
I'm also having a hard time with figuring out the orientation of the relay on the breadboard, thanks so much!

[DIYHacksAndHowTos]

I will try to get another picture added. But in the mean time, you can get a good idea from the breadboard layout on step 8. All circuit parts were purchased from RadioShack (see step 5). So you can just align them the same way that they are in the picture. I hope this helps.

[TakashiMoto]

Is this the same relay? pinout and all?
http://www.mouser.com/ProductDetail/TE-Connectivity/OUDH-SS-112D000/?qs=%2fha2pyFadui2QAjXzdmwdlJkRYZqifB3R%252baei18HFruUr665Gub%252bLA%3d%3d
I sourced one a bit different but i have to move things around.

[tygger281]

VERY NICELY done! I do have a comment / question: We decided to use the complete kit because it came with "compatible" lights that just plugged into one of the adapters on the inverter that came in the kit.

We put one on the back porch and the front porch, and bought a cute, very small Kitchen cabinet. We painted the cabinets to match the house and BOOM, we are off and running!

The cabinet was PERFECT because it had two shelves - one for the inverter, and one for the battery. We were using the existing lights - two came with each kit. We hung one set on the back porch, and one on the front porch. So, the battery started charging, and within hours, had lights on the front and back porch!

Our first set of lights blew out most likely about two months later. We went BACK through the instructions, and could find nothing. We tested the solar panel by charging another small battery. It was charging fine. We found something to plug in one of the other ports on the inverter, no issue. So, I went to the store to find bulbs to fit in there; there is nothing else to fit in there that is the correct voltage. ANYWHERE.

So, called HF - and they said, yes, we can send you new replacement bulbs at no charge AND it would take six weeks to get them. What was I going to say but ok. So, new bulbs come, we plug them in - they last two weeks and *poof* they die again. I called again; they said it would take four months this time. They had stopped using those bulbs and that inverter in the kit.

At one point shortly after this, the inverter did die. So we called for a new inverter. Got one after 3.5 months (of course, still waiting on the light bulbs). We hooked up the new inverter. Tested the other parts of it, it seemed to be fine. New bulbs finally came - they worked for less than a day. We gave up on getting more bulbs.

The front porch bulbs lasted nearly a year. Then they died. We never tried to get them replaced. In the meantime, we moved the back panel to our chicken coop, and use a small water pump for emptying out the excess water barrel, if needed, or reuse the water in the yard.

We still use the front porch panel as a trickle charge battery charger for the horse trailer and scooter batteries. But we are not using the inverter.

Is this why you are not buying the kits? Have you ever had similar problems with your inverters? Thanks!!!

[luvasu]

My experience says that an inverter needs space for cooling (air), never inside a cabinet, unless there are 2 fans (in an out blow, computer type). Above this, if the label says a wattage, never connect more than the 80% of this number of watts.
Following this rules my 80W inverter works for 4 years... and counting.

[luvasu]

I've different solar panels (7) up to 105W, feeding several 7Ah and 12Ah batteries, up to 186Ah, using a 10 Amp control charger (near to the limit 9.7 Amps)
On use (nightime) 4 inverters (120+120+80+80 W), sometimes at the same time, but not often.
Only mi first 7Ah battery has been replaced after 8 years duty, because not recharging above 4 VDC. (Similar to the one showed in a picture above).
My battery replacement is mandatory after 10 years duty (that one was a surprise).

[DIYHacksAndHowTos]

None of my components were part of a commercial kits. I just assembled it from off the shelf parts. I haven't been running my system very long but I haven't had much problems with my lamp setup.

[tygger281]

Oh, you are showing the kit in the final photo. Please let me know if you had similar issues.

[chuckyd]

Instead of using a converter, it would seem more efficient to use appliances that work off the same voltage as the battery/collector. There are several 12V appliances made for campers and motor homes.

[webgiant]

While 12V appliances exist for campers and motor homes, the reduced voltage means they usually have less efficiency and greatly increased cost. A 12V DC household refrigerator will run you several hundred dollars and have insulation so thick the interior will be considerably smaller than an AC refrigerator of the same general size. There are much cheaper 12V DC refrigerators, but they tend to be of the "improved ice chest" variety rather than an actual refrigerator.

An inverter allows you to use a wide range of Energy-Star appliances which are much cheaper than DC appliances, and get more use, and storage, out of your appliances.

[chuckyd]

Big deal. Just work on putting as much effort into DC appliances as has been put in AC appliances. If power is run through an inverter for an "efficient" appliance, is it still considered effecient from the other side of the inverter?

With the cost of inverters and the power lost in the process, it seems that eliminating the inverter would be more efficient.

[Ultra Computers]

Those panels look like thin film silicon panels, which tend to be the cheapest type of solar panel, but only run about 7 to 8 percent efficient. Currently the most efficient panels available to consumers (at 20 percent efficient) is the Sunpower E20 at 327 watts, at about 17 square feet of panel (including the gaps between cells and the frame. These panels run between $700 and $800 per panel (by the way, it is a mono crystalline silicon panel, which tend to by more expensive and more efficient).

Just thought I would add a little useful info


cheers
Ultra Computers

[londobali]

The question is: are those 20%-efficient cheaper than 3x the price of the 7%-efficient ones?
If it's more than 3 x as expensive, then might as well get three cheaper ones (if space allows)..
it will be cheaper and gives the same output.. or, in other words, it's more cost-efficient...

cheers.. :)

[ereus]

It should be borne in mind that AGM batteries are not suitable for inhabited environments due to any release of gas.

[webgiant]

So get a sealed AGM battery. Problem solved.

[gargoyle169]

Not trying to pee in anyones Wheaties but the system displayed herein is a Harbor Freight special. Not really in the spirit of Instructables.com. The entire package comes in a NON Recycled cardboard box with instructions!!!

"We have a "be nice" comment policy. Please be positive and constructive with your comments or risk being banned from our site. "

So I'll be nice and ask a constructive question, What is the cost per watt of this system, and what is the power density of the amorphous array? Then there is the matter of the 85 dollar AGM pile that Da Freight is peddling with this thing,, what is the reccomended c/20 rate versus dollar/watt ratio?

These are the real economics of DIY alternative energy.

[DIYHacksAndHowTos]

While the solar panel and the inverter that I used where purchsed from Harbor Frieght, no part of this project came from a kit. I think the confusion came from the picture in the final step. I just wanted to use a picture of a solar panel and system that was larger than my current setup to illustrate the idea of future delopments and improvements. But unfortunately the picture that I selected was that of a solar kit from Harbor Frieght. This was a poor choice on my part and I am sorry for the confusion. I have changed the picture to fix this.

In regards to your question, I used a 5 watt panel, 75 watt inverter and a 7 Ahr battery and was able to build the system for about $150 using parts from RadioShack. If you order the parts online you should be able build this setup for under $100. As my design lets you select the components that fit your needs, the performance is entirely dependent on the panel battery and inverter that you select.

[The Green Gentleman]

A very nice, classy response to a not-so-nice comment. That's not easy to do. A well made instructable, and a well-moderated comment section. Good job!

[dmarsh55]

CHALLENGE: apply this technology to a more heavy duty appliance. I have a 29 cf Kenmore Energy Star refrigerator/freezer, the label says 115V. We get semi-frequent power outages here, and of course our utility company is going up on our rates. Show us how to rig a set-up for this.

[DIYHacksAndHowTos]

There is no reason that this kind of system couldn't power a refrigerator. It is just a matter of making sure that all the components are rated high enough to handle the needed load. But for that kind of application you would have better luck getting an Uninteruptable power supply rated for your refrigerator's power, and many increasing the battery size.

[mgcasella]

Great idea! Another great challenge would be to build a hybrid system that powers the large AIR CONDITIONING unit for the house I live in!

In Kansas we've been having temperatures of 100 to 105 degrees each day this summer and our utilities bill has gone through the roof. Even if this potential rig cost $400-$500 I would still end up saving money over the course of the summer.

[Nove-Noga]

I spent four years working in a Las Vegas lighting shop. It was our job to help keep this the brightest city on the planet. Our rule of thumb for low voltage and transformer applications: Never exceed 80% of the rated output.

[pedromadeira]

Already my apologies for the English, but I have a question, I'm using a 300W Inverter (not pure sine) then when I start it (power on), right from the beginning, it's seeking more than 5A at the starting pike.

So, then made ​​in the design, does not allow a current output over 2A, at the output of the regulator (It's the 1 design, before the all relay switch, that commute the DC and the AC).

Could anyone help me get around this?

Thank you and best regards to all!

[DIYHacksAndHowTos]

You may need a different regulator or a different inverter. Sorry that I can't be more help. Good luck.

[pedromadeira]

Already my apologies for the English, but I have a question, I'm using a 300W Inverter (not pure sine) then when I start it (power on), right from the beginning, it's seeking more than 5A at the starting pike.

So, then made ​​in the design, does not allow a current output over 2A, at the output of the regulator (It's the 1 design, before the all relay switch, that commute the DC and the AC).

Could anyone help me get around this?

Thank you and best regards to all!

[jolshefsky]

I like that it's all DIY. I've been a go-to person for answering questions about solar setups for camping for a little while and I recommend people get a charge controller with a load switch. That accomplishes most of what you have in your control circuits (but good for you for DIY and explaining how it all works!)

My only minor quibble is about the power inverter. All the cheap inverters are "modified sine" which is a +180V/0V/-180V/0V wave that delivers the same amount of electrical power. It works fine for CFL's and most switching power supplies that just make the line voltage DC then work from there, or for resistive loads like incandescent bulbs and heaters (or, even direct line-powered LED light strings). But for transformers (e.g. plug-in brick transformers, and many many appliances) and AC induction motors (e.g. fans, pumps), the modified sine is completely inadequate and leads to lots of waste heat and potential damage to the appliance.

I have been recommending that people instead spend the extra money and get a "pure sine" inverter (I have a 300W Samlex brand that works very well). They are a lot more expensive per-watt, but especially for a small starter system, you really can't realistically use more than 75 watts or so for any appreciable time (that 7AH battery would be dead in in an hour at 75 watts, and realistically should only be run for about 30 minutes or so; a 500W coffee maker would kill it before one pot is done). The pure sine inverter will work fine with all appliances including things that people are likely to use like chargers for phones, iPods, or batteries, laptop power supplies, monitors, TV's, and audio amplifiers.

[mikeasaurus]

Great build, this is something I want to try sometime.

[kd1s]

Nice job on an ATX! Vendors like APC will charge a pretty penny for these.

[brjasper]

Neat little project. I'd posted before I read everything through, but I'd still suggest a small grid-tie inverter that would feed power back into the mains for the whole house. You can get some small ones fairly cheap as inverters go.