November 22, 2019

Wiring the Solar Panels

Last month we got the solar panels up.

Image from "The Solar Panels Are Up"

The next step was to research the best way to connect them and what we'd need to do it.

Image from "The Solar Panels Are Up"

Each panel has a pair of wires (technically cables) with connectors.

Back of solar panel.

One of the cables is positive, the other is negative. We had two options for connecting our three panels: in either series or parallel. There are advantages and disadvantage to each.

Series wiring connects negative to positive and positive to negative. This is the easiest configuration because it only requires plugging one panel into the next. It's a good choice for longer runs of cable and can use smaller gauge (less expensive) cable. This set-up multiplies the panels' voltages. Its disadvantage is that all panels must be in full sun. Even partial shade means no electricity. Or, if one panel isn't working properly none of them work, just like a string of Christmas tree lights.

Parallel wiring connects positive to positive and negative to negative. Its disadvantages are that it requires adapters and heavier gauge (more expensive) cable for longer runs. Its advantage is that it begins to produce electricity when any part of the array receives sunlight. It isn't up to 100% production until full sun, but at least it produces some. This set-up multiplies the panels' amps.

For us, parallel wiring makes the most sense for several reasons. The first is that we want to take advantage of whatever sunlight is hitting the panels, even with partial shade. The second is that we don't have a great distance between the panels and the battery bank.

Cables will be buried under the driveway and connect
the array to a battery box where the shelves are now.

We needed about 30 feet of cable to connect the solar panels to the battery bank. Dan will build a box for the batteries where the shelf unit is in the above photo.

The third reason is that we really don't need additional voltage. Each of our panels is rated for 57.3 volts (VMP). Multiplied by 3 panels that would be almost 172 volts. That would be overkill for the small 12-volt system we need to power our freezer and a chest fridge. (See "Solar Pantry Part 4: The Plan").

To connect the panels in parallel requires adapters.

Y branch parallel adapters. We bought them from Amazon.

They come in pairs, one negative and one positive. Connecting all three panels required two pair (for a total of four adapters, two positive and two negative).

One pair connects the first two panels together.

The other pair connects the first pair to the 3rd panel.

All 3 panels connected. These will plug into the cable
once the battery bank & charge controller are in place.

The next step is to bury the cable, so let the digging begin.

Wiring the Solar Panels © November 2019


Ed said...

If that were my solar panel system, I wouldn't worry about overkill. It might be powering just a freezer today but tomorrow it might be additional lights and by next week, I'm out adding more panels to keep up with demand!

Helberg Farm Stories said...

THANK YOU!! We are thinking about adding solar to our little farm but have not done it - yet. I guess I am afraid we will have a large expense and then find out not enough supply?! We have a couple of dear friends that have geothermal and just added a huge solar array on a new building of theirs (they are also close to 70 yrs old and he is a retired electrician but constant genius "outside-the-box" thinker). One day soon we hope to add it. Your blog made it all sound so easy and simple (we started looking at this before the now easy connectors). PLEASE follow up with this as we would love to know how it goes for you - including any issues please!

Cockeyed Jo said...

Having extra juice is necessary when using solar power. You can't let the batteries drop below a certain point plus inclement weather for days. So how many batteries did you get? More is better.

Susan said...

Thank you for making it so clear, Leigh. It's really helpful to see all the connectors and will be interesting to read about your progress with solar.

Kelly said...

It's looking good and it wouldn't surprise me if you're pleased enough that, as Ed says, you just keep adding on and powering more!

We're up and running with our solar now and so far, so good. We got a rather late start in the year since winter doesn't produce as much, but we did well enough at the end of the summer that our last power bill was a credit balance. :D I doubt that will be the case over the next few months, but after next summer it should always be next to nothing.

Leigh said...

Ed, exactly! My plan only required two panels, but we went ahead and put up three. We would love to be able to add more and use it for more. For now, the freezer and hopefully a chest fridge will be a good start.

HFS, you're welcome! I am always glad to share what we learn, both ups and downs. You can definitely expect quite a few more posts on this subject! I have to admit that this has been a huge learning curve, especially since the concept of electricity is an abstract one. Plus, everyone has their own opinions about things, so we've had to wade through it all to figure out what was best for us. It's extremely fortunate that you know someone with an electrician's background! We've also found quite a few good videos on YouTube, which have helped a lot.

Jo, that's true. Most people recommend not dropping below 50% "state of charge." Others only go to about 30% to prolong battery life. I've dabbled a little bit with this on a small, one-battery scale, but I'm curious how long our system will work out for this project. We just got the batteries yesterday. We were able to swing six which will give us 705 AH. That's more than the four I originally thought! Time and being patient has worked in our favor, 'cuz it enabled us to put away a little more for more batteries!

Susan, most of the books I read and videos I watched cover basic parts, but eventually we had to understand how to put the whole thing together. Those specifics have been a little harder to find, which is part of the reason our progress is slow. But, we're on pay-as-we-go anyway, so it all works out in the end!

Kelly, thanks! And congratulations on getting yours going! Right now we have the grid to fall back on, which is actually a comfort since we don't know what to expect. Since we'll get it up and running during winter, that should give us a good idea if it's large enough. We'll see!

Toirdhealbheach Beucail said...

Leigh, how weather resistant is that cabling and how long is it expected to last? Also, are you planning to put the cables in a tube or pipe underground?

wyomingheart said...

You explained that so much better than this dang book I bought! Thanks Leigh, and watch that back while digging!

Leigh said...

TB, good questions. I'm not sure of life expectancy, but hopefully, it's a long time since the cable is approved for direct burying! It's also approved for use in a conduit. Dan had some conduit but it wasn't enough. So he used PVC pipe. I've got pictures on that to show in my next blog post. :)

Wyomingheart, well, thanks! I looked at a lot of books, websites, and videos, but they mostly explained basic parts of the system. Details about putting it together were harder to come by, maybe because the subject is so complex. Obviously, I won't becoming an expert anytime soon!

Mike Yukon said...

All most finished, bet you are getting excited now that the big "flip the switch" day is just around the corner!

Leigh said...

Mike, progress often seems so slow! But between careful researching and uncooperative weather, that's just how it is. At lest progress is steady. :)

Rain said...

Thanks for the lesson Leigh. Your blog is going to be a "how to" for me in the future. It's interesting to know about the set ups. I don't think we could use solar panels at all during some months in the winter, because we simply do not get any sun at all. Do you need a certain amount of sun to produce enough juice for the batteries? I don't know if I'm asking that the right way...suppose, in my case, we have our solar panels so that they get full sun...but we only get half an hour of sun in the morning a few times a week...would that power the batteries enough to keep them going? Maybe that's a loaded question though...

Leigh said...

Rain, hopefully it will give you a gist of what's involved. Trying to work out the specifics for a particular set-up in more challenging.

It sounds like solar energy would be challenging for you. One of the books that been most helpful to me, Prepper's Total Grid Failure Handbook recommends that your panels should be able to fill your battery bank at least twice a week. That would go back to the size of your panels, the size of your battery bank, and how much you use the solar energy. You all might consider other ways to keep a battery bank filled. Wind? Hydro? A generator? Find someone close by who's doing it and ask!

Cockeyed Jo said...

More is always good. :o)

Leigh said...

Jo, the most we can manage!

Rain said...

Thanks so much Leigh! I have a lot to learn. I figure we'll be on the grid anyway (for the bank's requirement re: mortgage)...but down the line I certainly don't want to rely on it. November is the worst month here for the sunshine and I think there will be less sun depending on where we move to in the Maritimes. When I lived on Prince Edward Island, we were without sun for about 4 1/2 weeks in the winter, it was kind of depressing. But on that island it was perfect for wind power. Lots to think about and thanks for the link to that book. It looks like a great reference!

Leigh said...

Rain, we don't reckon we'll ever get completely off the grid, so we prioritized needs and chose accordingly. The other thing is to learn alternative ways of doing things. We try to find a manual or low-tech tool for every job we use a powered tool for. That way we have a choice. :)

Rain said...

Smart thinking. It's a nice idea to be able to be completely off grid, but realistically it likely won't happen! But it's a very good plan to find low tech or manual ways to do everything around the homestead as much as possible. I've been reading Prepper books today! Learning a lot!