Marine or portable off-grid solar systems

Xizang · February 2016

I'm sort of lurking here, asking a dumb question every now and then, and trying to accumulate enough knowledge to not screw up too badly.   Okay, here's my project: Setting up a little backup power supply in Nebraska at my girlfriend's place. But want to keep it kind of portable, where we can peel it up easily and take it with us to my next management gig at a coastal location. There, we will have a larger sailboat or houseboat that we will want to transplant the system onto. So the parts need to be saltwater resistant.

I'm at the stage of looking for an inverter that's cheap enough for unemployed older folks to buy, yet tough enough to live on the water in a marine environment.    And along with the inverter, I'm going to need a couple of respectable batteries that will survive in the same saltwater climate.

I have a Brat charge controller and a Square-D weatherproof combiner box, along with a few 100-watt 12-volt (wired to 24-volt in series-parallel) solar panels.    The plan is to buy more.

So if you were me, what make and model inverter and batteries would you go for? Bear in mind that we're currently old folks on limited incomes.

vtmaps · February 2016

12 volt panels tend to be more expensive than the higher voltage panels. If your system is large, you would be better off with an MPPT controller and cheaper, higher voltage panels.

How much room for panels is there on the boat? That may be a design constraint for your future system.

Xizang said:
So if you were me, what make and model inverter and batteries would you go for?

First things first... what do you expect your system to do? What are the loads? Do you expect to recharge the batteries with only solar? A system should be designed to meet your needs... you haven't told us what you expect this system to do.

--vtMaps

zoneblue · February 2016

"Whats a good cheap inverter" is a FAQ here. The short answer is there isnt one. The (slighty) longer answer is, Xantrex, Samlex, Exceltech are the cheapest you ever want to look at. Everything else will end up becoming a liability. This youll be better of going used than a cheap chinese POS.

Xizang · February 2016

Probably similar loads to what you would have in a small 2-bedroom home. Some small appliances, TV, some CFL or LED lights, computer router and a couple of laptop computers at night. And a couple fans.

vtmaps · February 2016

Xizang said:

Probably similar loads to what you would have in a small 2-bedroom home. Some small appliances, TV, some CFL or LED lights, computer router and a couple of laptop computers at night. And a couple fans.

I need numbers... like how many kwh per day you will consume. If you were asking advice on which pickup truck to buy, I would need some numbers... like how many pounds you want to haul and how large is the trailer you want to tow.

--vtMaps

BB. · February 2016

If you can keep the loads to 300 Watts or less, the MorningStar 300 Watt TSW 12 VDC inverter is a very nice unit for a smaller system.

-Bill

Dave Angelini · February 2016

But Bill, he said he had a girlfriend. Ever meet one who did not have a big hairdryer?
My old friend who we cruised with was always getting new girl friends. On his boat card it had a blank so he could fill in her name.

Xizang · March 2016

Dave Angelini said:

My old friend who we cruised with was always getting new girl friends. On his boat card it had a blank so he could fill in her name.

I've found a guy gets into problems when he doesn't keep enough options open.

Xizang · March 2016

Dave, what did you figure out regarding GROUNDING of solar panels and system aboard boats? Electrolysis problems?

Dave Angelini · March 2016

Xizang said:

Dave, what did you figure out regarding GROUNDING of solar panels and system aboard boats? Electrolysis problems?

Yep, especially when in port on shore power. Stay anchored and you are probably fine. It is better away from port anyways....
Grounding of solar panels is not an issue as lightning will get in other ways (the mast & rigging), but in a failure you really would not want the frame energized either.

Xizang · March 2016

I managed a large marina in California where we got all brand-new docks (insurance settlement). It wasn't long before I started noticing burn marks in the wood decking. Apparently lightning strikes. Everything is in peril when a lightning storm comes through. Even docked in a marina.

I was just wondering about solar, if there's anything special you discovered regarding grounding. If there are electrolysis issues we usually never think of in solar systems on the water.

Dave Angelini · March 2016

There are always electrolysis issues on a boat ! You must be inspecting often if you are going out on the ocean.
In a marina probably worse and far more susceptible to lightning but, usually only a 10 foot dive to the boat

wellbuilt · March 2016

I lived on a 30' sail boat for 5 years .
Solar panels are hard to mount , I had 2 200 watt panels mounted over the stern rail on ss pipe .
I had 2 125 watt panels mounted on the toe rail that we could stow away on a extra bunk.
There was 3 flex panels on the sail cover = 96 watts .
The battery's where. Rd4 I think ? 153 ah each at 12 volt .
I had a old freedom inverter 1000 watt with charger that ran on grid power when docked.
I had a bomar alt. That ran off a 20 hp diesel with aftermarket 4 stage charge controller.
2 years we lived at dock 3 years we where on a mooring , we had plenty of power.
We watched tv every night used the microwave ,lights , radio all day and night pumped water hot and cold , small frig
Most of the time the 400 watts of solar charged us full every day ,
In the spring and fall we needed more solar.
The alt charged the battery if we motered and the diesel heated the water .

Xizang · March 2016

What was everyone's experience with watermakers? They draw serious amps if you're producing more than a couple gallons of good water a day.

Dave Angelini · March 2016

Engine drive is hard to beat if you are motoring. If you are cruising, there is either too much wind or not enough and so you are often motoring. I use to install the Spectra water maker and the electric version is probably the best one to buy if you need serious amounts of water.

The GPS, autopilot, and watermaker are probably the best things that ever happened to the offshore boating world.
I do not know how they did it before.

Shadowcatcher · April 2016

I will inject only one element ditch the inverter and run 12V. When we are off grid boodocking (small trailer) we use just 12V and propane for cooking and heating water, and things like cell phone chargers etc, lights (LED), TV/DVD are 12V.

Marine or portable off-grid solar systems

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