Last article on designing and installing a large solar panel system

[DavidM]

This is the final article on designing and installing a large solar panel system in my three article series on solar panels. Please read and provide your constructive feedback. I will incorporate your comments in the final article and then upload to the Library.

David

 

[dhays]

This is the final article on designing and installing a large solar panel system in my three article series on solar panels. Please read and provide your constructive feedback. I will incorporate your comments in the final article and then upload to the Library.

David

It looks good. If I'd been able to read this before I started it would have saved a lot of head scratching.

I had a couple thoughts based on some of the questions that I had when I started.

You did a good job of explaining how to size the controller for volts and amps. However, I found it helpful to look at the power/temperature curve. If someone is on the fence as to the size of controller, that could influence them one way or the other.

Initially, I was confused about how the solar controller is controlled. Most of the time you need to add an additional control/monitor panel to actually control the controller. The other option, which I chose, was a bluetooth enabled controller so I didn't have to do that.

Dave

 

[Insequent]

David
Good article. My only comments are:
1. If you combine panel wiring then do it with a fuse block. That way, should you wish to isolate one panel it is easy to do so by removing its fuse.
2. You could add Victron to the list of good controllers.

For interest I have attached a graph showing my own system performance. I have 6 x 345W panels and 2 x FlexMax80 controllers, and 1284 Ah AGM house bank. And 2 x 200A alternators. The data were collected firstly on a winter/spring cruise to the Great Barrier Reef (GBR), and then in Brisbane (latitude 27.5°S) during summer. I have all comforts of home, and was typically using over 400Ah at anchor overnight. Plus more during the day. I can turn some stuff off to extend days at anchor if required, but usually don't need to worry about doing that. Reefer, icemaker, freezer are the biggest power hogs.

There are 4 panels on the hardtop, and 2 on the pilothouse roof. My avatar pic was taken a week after they were installed, and as shown in the pic I often lay the tall VHF antennae down to avoid shading. I still get some shading at certain boat orientations, and it has a huge impact on solar output.

 

[DavidM]

Initially, I was confused about how the solar controller is controlled. Most of the time you need to add an additional control/monitor panel to actually control the controller. The other option, which I chose, was a bluetooth enabled controller so I didn't have to do that.
Dave

Yes, the high end controllers are like high end inverters: You can do the basics with the main unit, but to do all of the bells and whistles you need the additional monitor panel or app on your smartphone.

But frankly solar controllers are pretty simple in operation and once you set them up you don't really need to touch them, so I wouldn't spend the money for the external monitor. Use your battery monitor to see how the system is performing overall.

David

 

[TDunn]

You can save money on the controller by setting up your house bank as 24 volts. Then run your systems with a 24:12 DCC converter. The cost of the converter will reduce the controller savings a bit, but a DCC converter gives very stable, constant, voltage that will make your electronics happy.

One other factor, voltage drop between the controller and the batteries has two effects. First it is power lost. Second it can lead to under charging your batteries. The second consideration can be negated with modern high end controllers by simple increasing the charging voltage setting on the controller by the voltage drop.

 

[DavidM]

One other factor, voltage drop between the controller and the batteries has two effects. First it is power lost. Second it can lead to under charging your batteries. The second consideration can be negated with modern high end controllers by simple increasing the charging voltage setting on the controller by the voltage drop.

You will be better off with big cable between the controller and the batteries to limit voltage drop to about 0.2 v at full charging and much less as the batteries get full.

Voltage drop is dynamic. If you use smaller cable then the voltage drop will be high when the batteries are discharged and the current is high. Once the batteries get full the current drops off and so does the voltage drop.

So if you set the charging voltage high to compensated for voltage drop at high charging rates, it will be too high at low charging rates when the voltage drop decreases.

And the short cable from the controller to main DC panel or battery is cheap. So go big.

David

 

[DavidM]

I have incorporated your comments into the final article and uploaded it to the Library/Systems section.

Enjoy!

David