Homemade Portable Solar Generator

By Dyers Eve

I had been thinking of constructing a portable solar generator for some time. I remember seeing a news story on a local company that was marketing a “new” product.

It was an 1800 watt portable solar generator with a 100 watt solar panel. I will not link their product here, I do not want to give free advertising or any positive or negative endorsement. I wanted to make my “own”, but I liked the idea.

So after contemplating for a while and having gone the “harbor freight” course, I started gathering my items. First I did some research on solar. And the internet is full of information…

At a local store that has a lot of items that they buy in bulk. They buy for instance a wrecked trailer load of whatever (electronics, sporting goods, food items, etc.), they turn around and sell these items to the public at DEEP discounts.

It is kind of a crap shoot on what they have from day to day, but sometimes some good stuff can be gotten for cheap. For example, I was able to buy 2 brand new Universal AGM batteries (12 volt 110 AH) for $80.00 each. Typically these retail at a battery distributor locally for $300.

I found on our local news classifieds, a local contractor that serves the DIY’er, and bought 2 (Chinese) 225 watt polycrystalline panels.

After exhaustive research I had found out that these panels were actually about .7% more efficient due to the entire array being capable of producing power, whereas the monocrystalline types have rounded edges that cut down on overall efficiency. I bout them for $0.89 a watt. $400 for 450 watts of (advertised) capacity.

I also researched the charge controller. I found that there are 2 types. PWM and MPPT. In short the PWM (cheaper by far) controller will only allow the panels to charge at a rate of what the batteries are at, leaving 40-60% wasted as heat.

Conversely the MPPT is a true dc to dc converter. It has intelligent programming that will convert the incoming voltage and amps to a much higher rate (95-98% advertised by all manufacturers).

The controller is capable of 30 amps and 150 VDC. The panels at OCV put out 37 VDC and 8.2 A at short circuit. Thus I am able to series wire the panel giving me theoretically 60 VDC and 8 amp charge rate.

Thus vastly increasing the performance of the panels and charge rate and capacity. Plus the controller can charge in bulk, absorb and float modes. The MPPT I bought, was off eBay from a seller with 100% positive feedback, for $176 shipped for free. (It arrived in 2 days actually)!

I ordered a Power Bright 2300 watt Modified sine wave inverter from Lowes. $247.32 after tax. It is a nifty unit. It comes with a remote for on and off, and it comes with the cables and connectors (already connected at the factory on both ends of the cables).

(No, I can’t run a refrigerator or a motor off of it, to me that is not important right now. A true sine wave inverter the same size goes for a few hundred more if I remember correctly.)

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Picture #1

I bought a Husky roll around tool box from Home depot for $64. (Picture 1)

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Picture #2

I placed the batteries inside the compartment on the wheel side. (picture 2)

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Picture #3

I connected the batteries in parallel to achieve an amp rate of 220 amp hours @ 12V. I used copper lug connectors to the battery posts that are facilitated for ¼” hardware. I then connected the #6 AWG wire to the positive and negative posts via the lug connectors. (pic 3)

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Picture #4

I needed a panel to mount the inverter and charge controller to. I had a 2’ by 16” ½” particle board from a past project, and some felt. So I took some adhesive spray and covered the particle board. (pic 4)

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Picture #5

Then test fit the board and located the mounting positions for the braces I got from Home depot and drilled a hole for the 1/4” hardware. (pic 5)

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Picture #6

I then fit the board into place. I did not screw the board to the braces, I want to be able to remove the board to access the batteries. (pic 6)

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Picture #7

I then mounted the inverter and a Mini ANL fuse (200A) on the board and connected the Mini ANL on the positive cable. I also mounted the sensor for the remote. I then attached the cables and started the inverter to make sure we were a go. (pic 7)

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Picture #8
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Picture #9

I then mounted the MPPT, and attached the #6 AWG to the charge controller. (Yes I know both leads are white, I used colored tape to identify the polarity. (pic 8) (pic 9)

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Picture #10

I then hooked up the extension cable for the PV panels to the controller. (I got the extension cable from the solar panel guy for $0.40 a foot and $2 for the connectors).

I bought 50’, 25’ for the positive and negative. I figured when we go camping, we would be in the shade but the panels could be located 25’ away in the sun, while we were in the shade. (pic 10)

I hooked up the panels in series (+ to – between the panels the + and – to the controller).

It was a warm but overcast day, very hazy. The batteries were at 50%, and within just a few minutes the array had the batteries at 80%. It was charging the batteries at 13.8 V at 8 amps!

On an over cast day in maybe 15 minutes. I admit nothing was running. The inverter was off and there was no load.

So for $1136 I made my own generator. I have 4 times the solar wattage and twice the battery capacity of other manufactured ones. I also admit I got deep discounts on some items like the batteries.

[Rourke: Great job and thanks for sharing!!!!]

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16 thoughts on “Homemade Portable Solar Generator”

  1. Great write up. I saw the adverts for the un-named solar generator salesman on Glenn Becks show years ago. After about five minutes of research, I came to the conclusion that the same components could be purchased at Northern Tool for about half what the guy was charging, and that was retail. I wrote to Beck saying that I had no problem with folks going into business but DID have a problem with those folks using fear in an attempt to rob the public. Beck didn’t even have the decency to write back and tell me to go eff myself. While I never pulled the trigger on building my own, this article is a great inspiration. Gotta go to work…………………..

  2. Nice write up Dyers, very descriptive. Great project.

    You might want to reconsider the parallel battery connection. It will work and the batteries appear to be indeed in parallel but better practice would be to charge and discharge from terminals on different batteries. Again if I interpret your parallel wiring correctly, the majority of current draw will come from one storage battery and the majority of the charge will flow to the other. I encountered a similar problem when wiring starting motor batteries in parallel for an industrial generator using what appears to be the same charge/discharge wiring. The battery wired to receive the charge from the alternator/regulator was kept at rated charge, whereas the battery connected in parallel to the battery being charged and directly connected to the starting motor struggled to maintain full charge and eventually failed before its twin. Of course, I may be interpreting your wiring in error but I think you have the two batteries in parallel with the charge side connected to one battery and the discharge inverter side to the other. If so, keep the batteries in parallel but cross the charge/discharge sides of the inverter and solar cell charge regulator. This is kind of hard to describe but easily understood in schematic which this format doesn’t easily permit. If desired, I could forward Rourke as diagram. Then again – I could be mis-interpreting your wiring from the photo.


  3. If you have any plans to use that invertor at its rated 2300 watts, you might also want to reconsider the wire size you are using between the batteries and the invertor.
    Assuming 90% efficiency, a 2300 watt invertor output will place a load on the batteries of approx. 215 amps.
    The 6 gage wire you are using is rated for a max load of 111 amps at 12 volts (or a 1200 watt continuous output at the invertor — at 90% efficient) — according to several sources I looked at.
    To run 215 amps, you need wire gage #1

  4. Thanks Arlene, I have thought about selling a few, but I am not one for selling I am more for sharing knowledge.

    P.R. I see what you mean. I am no electrician by any means. Your suggestion is an easy fix.

    Greenman. The #6 wire is coming from the MPPT Charge controller and goes into the battery bank. The CC puts out 35 A DC max. #6 is way larger than needed.

    Feedback is always welcomed.

  5. Dyers, thanks, this is definitely worth exploring and I have a h/f within a half hour drive, time to order a catalog.

  6. It would be a neat project to build one of these on an isolated enclosure inside a metal military medical chest. Of course it would be vulnerable to emp whenever opened for connection to load and solar (or wind or generator or an AC mains charger) but otherwise, hmm … I really like your project very much Dyers. A cheap battery electrolyte hydrometer would be a useful addition). I think a recent edition of QST described alternate power for amateur radio used in RACES. One nice thing that article pointed out was a need to standardize on Anderson Power Pole high current connectors.


  7. P.H.R. I did use anderson power pole connectors. I just didnt add them in the article. Sorry.

    Dave. I used A.G.M. (absorbed Glass Mat) batteries. These are sealed and do not use liquid electrolyte. More expensive, yes. Safer, absolutely. They also tolerate more charge/discharge cycles than other types of batteries except Lithium Ion types. Lithium Ion’s are $$$$$

  8. Awesome Stuff!
    Inspiring me to build something, I have so many components and have been an electrician for so many years… I also tinker with electronics and such. Dyer, this is like watching a young person try something for the first time and showing a Pro that he is a natural!!! Take that as a compliment, that is how I mean it!

  9. I admire people who take the initiative to do things themselves, but high power solar generators and electrical stuff needs to be done correctly. This project is not.

    1) Bad mechanical designed
    -batteries not physically attached, can move and short out
    -electronics not attached, and can move and short batteries
    -box way under rated for the weight of the batteries
    -total system too heavy to be portable, including the big poly panels
    2) Bad electrical design
    -not properly fused anywhere in the system
    -wires under rated for max current draws
    -batteries wired improperly, will age prematurely
    -inverter over sized for the size of the battery bank
    -no battery monitor
    -series poly panels susceptible to shading, orientation

    I find it curious that for your initial testing, you claimed your batteries where at 50% (how did you know that?) and the panels were putting 8A into them on a hazy day (probably true) and that they charged up to 80% after several minutes (how did you know that?). At 8A, that 220AH battery bank will charge 4% per hour, not even counting the 10-15% charging losses that most lead acid batteries have.

    • Your response to the article was overly critical. I don’t see you sticking your neck out writing an article on this subject. Your negative response will fall on deaf ears because you did not offer very clear solutions or the “right” way to build solar generator. Your assumption at the end was that he was lying. I would believe him far more than I would believe you. The author gets a B for his article. You get an F for your horrible response.

  10. Sadly my time on earth is short. Electrician Jobs will be at a premium demand. I have been a master and contractor for many years . one of the many problems will be the do it yourself handy men. The problem comes from handling a device that can kill you. because it isn’t plugged in right!! wrong! it has full voltage and current in full sun. A condition that makes you sweat. this lowered the body resistance is low. Conditions that allow lower voltage to deliver the 4 milliamps it takes to kill you. safety is the first rule keep the photocells covered. Only plug in the cables at the last moment. never remove protection on the connections for output cables If you are not an electrician read the instructions until you understand them. before you start make sure you have all the proper tools that are in proper working order. Gloves. 6 mill rubber gloves to insert inside regular gloves , used when attaching cables. Newspaper isn’t enough to block photocells. When installed correctly it can save money. Don’t count on the power buying your extra power. I sold power to my neighbors. charging their batteries at my lowest demand times. they drive inverters for convenience . I have solved my surpluses and neighbors save money on their bills. The point is that when properly sized will save money. with costs going higher it best get the size you need. Just because you have the same size house as your neighbor Doesn’t make your use the same. You need someone able to calculate the total possible current draw and the average daily use. Producing total possible need every day while using normal average use will most save money. companies now specialize and provide better sizing. Take care, we still have the shysters’ . Take the next step to the future, but take it with care and safety—–Grampa Master electrician (retired)

  11. I liked your article and your build. I do agree on fusing and using the larger maximum wire sizes. At least you put in the effort to build and learn, many will criticize, but won’t attempt. Remember, those who can DO. Those who can’t TEACH.


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