Thursday, March 15, 2012

Wiring your Solar System

Yesterday I wrote about how to choose the components of your solar system. Now that everything is all picked out it's time to put it all together. Today I'll discuss how to wire up and install your new solar system.

There are four main components in your system, the panels, the charge controller, the batteries, and your boat's common connection. Each must be connected in order to benefit from those flashy new panels you just got in the mail. I'd like to start with a simple diagram, then explain it further as we move on.

click above to enlarge

Above are the four main components that we spoke about, and that I helped to choose in my previous article. The above diagram is for 12v panels, and 12v batteries. You'll want to have panels that work on a 12v system for sure, but there are other battery options, such as 6v batteries that I'll mention later.

Since your charge controller is meant to operate on a 12v system as well, it will have a range of voltages that it can operate at. It's important to read your manufacturer's specifications to make sure that you are not feeding your charge controller with too much voltage, otherwise you'll get that nasty "burning electrical components" smell in your boat, and that's the sort of smell that we're trying to avoid here. In order to not give the charge controller too much voltage, the panels are wired parallel. Parallel wiring doubles the amperage output, but leaves the voltage the same. To wire them parallel the panel's positive connections are wired together, as well as their negative connections, as shown above. Then a positive connection from one end of the circuit and a negative connection from the other end of the circuit is fed into the input on the charge controller.

Your charge controller will accept the current coming from your solar array and adjust the voltage and amperage to either charge your batteries, run your vessel's equipment, or both. The charge controller's output is fed directly to your vessel's main positive bus and it's negative ground. Your positive bus is a power distribution block that all of your electrical components are wired to, and your negative ground is where all of your equipment is grounded. On your boat, you should have a good negative ground that leads to the water. On many vessel's it may be the copper strips your SSB radio is wired to, or to your keel. If you can find the other negative connections then you're probably safe connecting the charge controller's negative output there.

The batteries in the above diagram are of the 12v variety. Since all of the equipment on the boat needs a 12v connection, we want to keep their voltage at 12v, even though there is two of them. In order to keep the voltage the same we are again going to wire them parallel. Positive to positive and negative to negative. This make's the 2 batteries in the bank act as one larger battery. It keeps their voltage the same and adds their amperage.

What about 6v batteries?
If you have two 6v batteries in your bank, then you will need to wire them in a series to double the voltage so that your equipment is getting the 12v that it needs to run. No problem. Instead of connecting the positives to the positives and negatives to negatives, simply do the opposite. One battery's positive must go to the other's negative, as shown to the right. The rest of the system can be wired as usual. Make sure that when connecting to the vessel's main bus the connections are made from opposite ends of the battery bank, as in a positive from one battery and a negative from another. This makes sure that your batteries are both drained and charged evenly, extending the life of your battery bank.

What if I've got four 6v batteries?
Then you have two options. You could either put them in separate banks, or get fancy with the wiring to keep the bank at 12v. On my boat, I have two separate banks that I can switch back and forth between with a switch like this one. Using that switch I can charge and run my system with just one battery bank or use both. But let's have a look at the wiring. To keep the system at 12v you'll have to use a combination of both series and parallel wiring as shown below.

In this diagram there are four 6v batteries. The two on the left are wired together in parallel, so that their combined voltage is still 6v. The same is true with the two batteries on the right. However, the orange wire in the middle that connects the four together puts each group together in a series, making the combined total voltage of the entire bank 12v.

There are still a few other options when wiring up your solar system that I have not covered but this article covers most situations. If you are having any trouble wiring your system, or want to add components that are not mentioned please leave me a comment and I'll be happy to walk you through the process.


  1. Rob - You mentioned to me when we were down at Sven's, but I forgot to make a note of it... where did you order your panels and charge controller from? What charge controller are you using? Thanks! - Bryan

  2. Hey Bryan, good to hear from you! I got my solar panels from civic solar and they are the ET Solar 95w modules. Civic solar gave me great customer service and they had a really reasonable price including cheap shipping. I can't recall where I got my charge controller from but mine is made by a company called blue sky. I would definitely recommend getting a blue sky controller, it works great and lots of other cruisers recommended them to me. Everyone seems to recommend blue sky or morningstar controllers as I've heard great things about both.

    Good luck!

  3. Rob

    There should be only one electrical ground on a boat and that is the engine block. From one point on the block a heavy wire should lead to a bus and all other electrical grounds connect to this. The ssb copper strips and the keel if used for lightning protection are earthing points and not meant to conduct electricity.

    Also the positive wire to the batteries should be fused close to the battery post.

  4. Hi Rob,
    This information is exactly what I was looking for...thanks!! My 8hp evinrude will also be charging the batteries when running. Will it harm the controller or panels?


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  6. can you please post some pixs of the solar power setup on your boat