The Ultimate Guide to Building a Personal (and truly portable) Prepper’s Solar Generator

by Erich

The following is a guest post provided by Michael Lemieux

Often times, you’ll see ads on the internet and television for these solar generators touting how efficient they are and never needing fuel to operate. While not technically true (you don’t need to “purchase” additional fuel to operate) it is a bit misleading as solar radiation is and can be used as a source of fuel. But yes, for now, sunlight is free to all who have access to it (presuming you are not in some deep underground cavern.)

The barrier for most of us though is the cost — hundreds or even thousands of dollars that most cannot afford to part with for just one item.

But for those willing to purchase a few common items and willingness to venture into the “Do it yourself” world you can build one yourself.

Overcoming the Solar DIY Hurdles

Most people may find it a bit daunting to tackle electronics and wiring to safely (and most importantly) build a dependable generator that will be there when we truly need it. But in truth it is not that hard and most of the “complexity” is taken out by getting the right components and using a bit of common sense.

The second barrier is the hesitation of not knowing what we don’t know. With the modern age of online research and more importantly looking at what others who have said about the components, the rating, of how well a product works.

As to the components I list here, they are ones that I have used and your research may lead you to other items that provide greater functionality and dependability. This is good, the more you know the better equipped you will be to prepare for the future and knowledge is power.

How to Build Your Personal DIY Solar Generator

To start things off, the only limitation on this generator is you, your budget, and needs. The solar generator I will be showing you how to build today is not going to power your whole house but will help you keep your hand-held devices charged, will even be able to run multiple lap tops, charge batteries, virtually anything with a USB, or even jump start a dead car, and run a few lights for a number of hours.

So to get right into it here is a list of the things you will need. I am a big fan of Amazon Prime for the free shipping and have found the prices quite comparable to other outlets but shop around locally and you may be able to save even more. But one word of caution, do not skimp on the battery as that is what provides the amount of power and how well and quickly it can recharge from the solar panel.

Here we go:

What You’ll Need

First off is the battery:

1) ML35-12 – 12V 35AH U1 Deep Cycle AGM Solar Battery

batteryThis is a deep cycle battery that maintains its power output during most all of the usage phase. These batteries are most commonly used for powered wheelchairs and give hours of use and high power.

2) Solar Charge Controller Esky Intelligent LCD 30A 12V/24V 360W/720W PWM Solar Panel Regulator Adapter Charge Controller

charge-controllerIt is important to get a charge controller that will adjust for charging the battery but also load balance. This controller will allow for usage of the power output ports while charging and still maintain peak battery charging and will keep the battery charged even when demand is high.

3) Instapark® NEW All Black 10W High-Efficiency Mono-Crystalline Solar Panel

solar-panelI chose a mono-crystalline over a poly because of the historically better electrical production of the panel output and the cost. I think I paid around $40 for this panel which can be paired with other panels to create as large a system as you need. I am only using one of these for this single battery system as I wanted a truly portable system and the larger your array is the less portable it becomes.

4) 12V Dash Sockets and Primary Output

dash-socketNext are 2 – 12V dash sockets, or what used to be called a cigarette lighter socket. This is what we will use to attach the solar panel to the housing as well as to provide for a 12v outlet. These may vary in appearance but are cheap and can be found in most automotive and hardware stores for just a few bucks. (Optional based on how you wish to wire your system.)


usb-portYou will also need to determine what your primary output use will be for your generator. I wanted to be able to charge multiple USB devices as well as run a 12v converter to convert from DC to 120ac or to power a 12v device directly from the generator. There are also two USB ports on the charge controller as well but I have the controller inside the lid of the housing and it was not convenient to open the housing every time.

5) The Housing

field-boxThe box I chose was a 1612 Plano Field Box that would hold the battery and all the components as well as having a small compartment outside on the top of the lid to hold connectors/cables for charging different devices. These run less than $20 and are easy to cut to install all the devices. The tray is not used for this project.

6) The Electronics

You will need one spool of red and one spool of black 10awg electrical wire to make the connections. This can be purchased at most any hardware stores. I recommend using a single color (red) for positive connections and black for negative connections.

Because we are working with electronics it is imperative that we do not hook things up backwards or short the system. You can wire each of the components directly to the controller and bypass the use of the connectors. I recommend the use of connectors to aid in circuit isolation as well as ease in modifying the system later. You will see more on this as we proceed through the project.

battery-harnessTo connect to the battery, and to protect the system, use a battery harness with a built in fuse like this one (Battery Tender 081-0069-6 Ring Terminal Harness with Black Fused 2-Pin Quick Disconnect Plug) which you can get on Amazon for about 6-8 dollars or locally at most automotive stores.

Other components can be added as you desire such as a digital readout of the battery level, an LED light to work with the system at night, etc. Your only limit is your imagination and physics of course.

Wiring Diagram

The basic wiring drawing is shown below:

Each line in the chart  represents a (+) red wire and a (–) black wire.

Each line in the chart
represents a (+) red wire and a (–) black wire.

It really is this simple. The complexity is increased on how many items you want to add of each component and additional “features” such as an on/off switch, lights, etc. I recommend starting with the basic system to allow for simple energy in and energy out and then expand once the basic system is up and running.

The solar panel is connected to the solar array port on the charge controller. The charge controller then feeds the electricity from the panel through the battery port to the battery posts and monitors the battery charge level to ensure it does not over-charge the battery as well as isolates the solar panel from the battery when its voltage drops at night. The controller then/also feeds the output devices connected to the LOAD port on the controller.

To illustrate how simple this generator setup is, you could actually build your generator with just this information. Attach the red positive wire and black negative wire of the solar panel to the appropriate poles marked with the solar panel on the charge controller. Attach the positive and negative wires of the battery to the center or battery marked poles on the controller. Then lastly identify your positive and negative connections on your output device attach the appropriate colored wire and attach them to the output terminal on the controller marked by a light bulb.

That is all there is to it. Of course that would not be efficient and the lines could easily get tangled, shorted, or pulled off the devices. So we will put everything in a nice neat traveling case to keep our generator running for some time to come.

This will make more sense as we move through the build process…

Putting it all Together

The tools needed for this build will be:

  • a drill or other means of cutting your holes in the case
  • a drill bit the size of your output component
  • wire cutters
  • connectors – (type of your choosing)
  • Phillips screw driver
  • Electrical tape
  • Silicone sealant

Step 1: Lay Out and Mount the Components

Once you have assembled all the parts you will need to lay out exactly how each component will fit into your housing. I suggest actually placing each part in its approximate position with the battery sitting inside the container. This will ensure that your desired positions will work and not be blocked by the biggest item in the box, the battery.

Once you have determined where each component will go you will need to drill the appropriate holes and mount all your components into place.

Mine is laid out like this:

component-layout

You do not need to make yours just like mine, this is only an example and you may lay yours out how it would best fit your needs and how you intend to use the generator.

The two plugs on the left are a 12v cigarette lighter type outlet and a dual USB power output to charge any USB compatible devices from outside the box.

The battery sits in the middle (ish) to help balance weight. The closer the battery is to the center the easier it is to carry.

The switch and battery readout are optional and will only be briefly covered in this tutorial and is not necessary for the generator to run, it is simply there for ease of gaining information on the system without opening the box.

On the right is a 12V plug used for the input from the solar panel. I made it this way to allow for easy disconnect during non-charging periods and to facilitate quick movement without having wires hanging that could get snagged while moving.

Determine the size hole needed for each component that will be mounted on your box. Drill the desired holes and mount the device. I recommend adding silicone sealant to each device prior to inserting in the holes to make a water resistant seal to help protect the system if it is outside in the elements.

mounted-controllerI have chosen to mount my controller on the inside of the box lid to keep it out of the elements and protected from snagging the wires connected to it. You may want to look for a box that has a larger storage area in the lid to provide for this protection but I went the less costly route for this build.

Once all your devices are mounted where they will be going then it is time to look at each component and how they are wired.

Step 2: Wire the Panel and Battery

Wiring the Panel

The first component we will look at is the solar panel.

The solar panel listed above comes with lead wire already pre-soldered to the panel. At this point you need to determine if you wish to direct wire the panel or utilize some type of connector.

I have added a 12v auto plug to the end so I can quickly attach it to the box. How you wire it is up to you. Some have added banana connectors or two pin trailer connectors, it really does not matter.

pos-neg-wiringFor a direct wire connection run your wires to the charge controller and attach the positive and negative leads as shown here:

For those wishing to go the connector route choose whatever connector you want to use that has been installed in your box and wire per directions for that particular connector. The greatest concern is to ensure that positive and negative connections do not get crossed.

The Pigtails on my connectors were red and white; others will be red and black or yellow and white. Though try to maintain uniformity so that when looking at the connections you will know which is positive and which is negative but the colors do not matter. If all you have is black wire get a roll of red tape and place a piece of red tape at each end of the connection for positive and your good to go.

12v-connectorI added a 12v auto connector to the wire leading from the solar panel as well as a couple feet of wire to make for easier deployment of the panel and give me the ability to have a small amount of separation between the battery and the solar panel. This was simply a convenience decision and one you will need to make for your own requirements.

That’s all that is needed to be done with the solar panel, so set that aside and well next look at the battery.

Wiring the Battery

The battery I have chosen is a Mighty Max ML35-12. It is a 12 volt 35 Amp Hr rated battery that completely sealed and requires no maintenance and will still operate in any position and at a wide temperature range. Also because the size is right (7.68 in x 5.16 in x 7.13 in) for placing inside our tool box.

The battery comes with square lead posts that have a hole through it and two sets of nuts and bolts for attaching your wires. Attach the red lead from the terminal harness with the built in fuse to the positive (red) side of the battery by running the bolt through the lead post and the ring of the harness and add a washer, nut and then tighten. Use caution and do not apply too much pressure, a ¼ to ½ turn after hand tightening is sufficient. Now do the same to the negative side with the other wire of the harness.

You will notice that the harness comes with a 2-pin quick disconnect plug. This was a primary consideration when designing my system as this was already on the harness I decided to continue the use this scheme throughout the system.

Step 3: Perform the Final Installation and Build

You should now have:

  • a solar panel wired and ready
  • Battery wired and ready
  • Controller mounted in or on your box
  • Box with outlets ready to wire up

components-finished

Install the Battery

The next step now is to install the battery into the box. Though there is not very much room the battery will have a tendency to move about a bit. In the past I have used sticky backed hook and loop fasteners on the bottom to keep the battery from sliding about. Another option is to use high density packing foam to “wedge” the battery in place.

You will now need to cut a set of wires that will run from the controller to a mating connector that will connect to your battery harness. Ensure all connections are tight and no bare wires are exposed. Do not expose the wires at the controller end just yet to ensure we do not short the battery.

connected-batteryOnce the connector harness is wired, loosen the two battery terminals corresponding to battery output on the controller. If you are using the same controller I am it will be the center two terminals. Trim the red wire back about a quarter inch and twist the wires to keep them from fraying. Slide the red wire into the + terminal on the controller and tighten. Give the wire a gentle tug to ensure it is clamped in place. Now repeat this process for the black wire and the – terminal. You will notice the controller light up as soon as the black wire is connected showing you have done it correctly.

Note: Your battery should have an initial charge for the system to operate correctly. If you battery is dead, please charge it in a conventional trickle charger before attempting completion.

If you have chosen to use quick disconnects on your components, as I have, then the next step is to cut corresponding lengths of red and black wires necessary to connect to the mating connector of the solar input. Make sure that the positive and negative wires pass through to the correct wires on the other side of the connector to prevent shorting the system. If you have chosen to wire directly then move on to the next paragraph.

connected-panel-wiringOnce this wire set is ready connect the solar panel positive (red) to the terminal on the controller marked + and the black to the one marked -. This is the left most set of terminals on the controller, if using the one I use, or the set marked by solar or a picture of a panel.

If the panel is now in the sun you will see a green light indicating the unit is charging in the top left corner of the controller.

Parallel Wiring of Your Components

parallel-wiringNext, your output components will need to be wired up in parallel. That means all the red wires will be wired together and all the black wires will be wired together and all terminate (come together) into a single lead of one red wire and one black wire.

Measure a pair of wires to go from your output components to the controller. Connect the component red wires to the single lead to the controller for red and then black. Tape these connects together to ensure there is no bare wire and no chance for a short.


completed-wiringLike the other two terminals loosen and insert the red and black wires into the terminal blocks and tighten.

The Final Product

With your build complete, your new solar generator is now ready for operation and ready to travel….

finished-generator-1

finished-generator-2

This is the basic premise for all solar systems the only difference is scale (number of panels, batteries and output), otherwise they are the same.

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15 Comments»

Comment by Steve
2016-02-18 00:19:44

I made one similar to this several years back. Mine uses a rollable 21 watt solar panel to charge the system which I housed in a 20mm ammo can. I added cardboard lining to the metal can for EMP shielding of the components. I also store my radios, spare smart phone, usb chargers, an intelli core battery charger, and an assortment of rechargable batteries. Lastly, I included a miniature tool kit ( cutters, needle nose, electrical tape, multidriver, and clip leads) and small multimeter.

 
Comment by Luke
2016-02-18 00:33:15

A couple questions.

I see this as being a very useful tool and would love to know exactly how long it could keep a high-end laptop such as an 18″ Alienware laptop with the 350 watt power supply going before the battery would be incapable of keeping it going.

I also use a bi-pap device to keep me breathing at night. I think it uses about 100 watts of power but I’m not sure.

Would such a generator as you have built keep a bi-pap running all night or even two nights without recharging?

I’ve looked at the math for all this and there is something I don’t understand about working out the equations because I just can’t figure it out. Math was never a strong point of mind anyway so its probably something simple I am overlooking.

Good doc though on how to create one. And how easy is this plan to scale upward to something that actually could power like a single room in a house with like a small heater or air conditioner?

 
Comment by Franco
2016-02-18 01:39:52

Thank you for the great article! Looking forward to building my own, for I live in the perfect climate! Subscribing to Tactical Intelligence has been one of the best investments I ever made! Thank you again, Erich!
Respectfully,
Franco
(Palm Springs, CA)

 
Comment by Steve
2016-02-18 02:07:48

Total amp hour rating of the battery is number of amps at the rated voltage the system can deliver in an hour before being drained The battery can only charge at a rate that is limited by the charge controllers maximum watt rating times it’s voltage rating ( eg. 20 amps x 12 volts = 240 watts max solar panel input power). If you have a 21 (15v at 1.5 Amps) watt panel like mine you can fully charge a 35 amp hour battery in 26 (35 ÷ 1.5) hours of full sun on the panel. A 240 watt (30v at 8 amps ) panel would charge the same battery in 4.4 hours (35 / 8 ) of full sun.

Watts consumed times hours used equals watt hours consumed by the device in a given time frame. Watt hours / volts equals amp hours required at a given voltage. Your 100 watt cpap (eg. 12V at 8.3A) unit would only run for 4 hours off the fully charged 35 amp hour battery (35 / 8.3 ) cited in the parts list.

When calculating run times from watts, be sure the system voltages are considered. 24V at 5 amps consumes 120 watts. 12V at 5 amps consumes 60 watts. A 24 volt battery at 35 amp hour rating has more deliverable watts than a 12 volt 35 amp hour battery if both are fully charged.

Steve

 
Comment by Frank Clemens
2016-02-18 04:59:30

I have 26 Solar Panels on my Roof and they are connected to the Grid, so that I get Credit on my Power Bill. So when the grid goes down they do too. Then my Natural Gas Generator comes on in 14 seconds, that is connected to the Natural Gas Pipeline.
How can I use what I have to charge up these batteries?

 
Comment by Jane
2016-02-18 06:06:59

Hello I really appreciate you putting this artical out there for the general public, I have been checking out the prices of solar generators, too rich for my blood so I was looking for information on how to build one. I really like your information. I had a question can you build more than one to make a larger one .large enough to run a refrigerator and lights and if needed heater. if so could i connect them together and how would i do that. thanks Jane

 
Comment by Benjamin
2016-02-18 13:07:38

No it will not. 35 Amp Hours is not a lot of energy.

Bi Pap: 100 watts / 12 Volts = 8.33 Amps
All night: 16 hours absent peak sunlight * 8.33 Amps = 133.33 Amp-Hours
35 Amp Hours / 8.33 Amps = 4 hours at most

Assuming your bi-pap draws the 100 watts continuously, at most the battery shown here will run it for 4 hours.

It would run your laptop for about an hour.

This system is small to be portable and will recharge cell phone and other small electronic devices. Anything with a motor or that does physical labor will not run long on this system.

Using a Pair (must use two wired in series) of GC2 batteries will provide you at least 400 Amp-Hours (AH)

400 AH / 8.33 = 48 Hours.

 
Comment by Steve
2016-02-18 14:01:45

Ben,

The GC2 battery is a 6 volt battery so as you correctly stated two batteries must be wired in series to get the required 12 volts. The available amp hours of the two batteries in series is still the same as one battery. Amp hours are not added in series (red to positive; red to black; and black to negative), amp hours are added only when wired in parallel ( red to red; black to black).

A few simple rules of electrical circuits:
Volts sum in series, remain the same in parallel;
Amps sum in parallel, remain the same in series;
Watts equals Amps * Volts;
Watts sum in either parallel or series.

These rules apply to solar panels and batteries alike. These rules are fundamental to all circuits.

Steve

 
Comment by Carol Wilmot
2016-02-18 14:54:53

Thank you for this excellent project. Going to build one for myself.

 
Comment by Opiner
2016-02-18 15:51:18

Excellent article. Thank you.

What is the make or where can we get a battery readout like yours? It looks really nice.
Also, what is the source of the switch you used?9uDm

 
Comment by Indeedie
2016-02-19 01:37:33

I designed and built my off-grid system, then lived it for two years. It worked well and I’ve since started upgrading.

I see a few issues with this design. First and most important, the 10 watt solar panel is far too small to be of practical use. In winter, if it is directed at the sun, a user would get between 30-40 watts of charging per day. Subtract from that, the losses from charging a cold battery and from extracting the power afterwards. It’s simply too small. In summer, the charge would range from 50-80 watts per day, again in full sun with the panel appropriately directed. Subtract battery losses of about 30% and you’ll see the panel is still too small.

I would suggest a polymer panel which rolls up as an alternate source of charging. There are panels in the 60-80 watt range that are very small when rolled up. Another option would be to use folding panels.

The remainder of the design appears very solid. Kudos for a great article, and a good DIY project.

 
Comment by Ernie
2016-02-20 18:36:39

Hello Benjamin,

I built a kit like this but with 2 batteries and a 35W solar panel and charge controller, all from Harbor Freight last year. I used it for camping and it worked great. I needed it to power my CPAP machine, like your Bi-PAP. It lasts all night for me on just one battery. During the day, I recharge the battery and at night use the second battery. I just rotate the batteries each night.

 
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