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Date: 19 April 2016. Solar, Batteries and an Inverter.


This was a four-part series on solar power, battery storage and AC power used aboard my boat. Sometimes I prefer smaller doses of information and for those who do the separate articles are:

  1. Batteries Store Power

  2. Solar Makes Power

  3. Power Used Aboard Seaweed

  4. Inverters Make AC Power

This is the complete version with all the information contained in the above four articles.
Solar, Batteries and an Inverter:

A boater wrote asking about solar power. Like many I have embraced the solar movement. The price has come down on the panels. Nothing moves so nothing breaks. It is quiet. What solar panels are not is the complete package. There's more to it.

I started with one 75 watt panel mounted over the cockpit in front of the wind generator.

If you have the room for them, solar is definitely the way to augment your power supply. I love mine. The one complaint I have heard time and again is "
I wish I had more space for solar. I envy you folks with room for multiple panels."

A few years back I added two more 100 watt panels atop the pilothouse.

Aboard Seaweed I had a total of 275 watts. At that time I had four 100 amp batteries. The combination was not enough to run my refrigerator 24/7 unless it was windy. Then the wind generator kicked in enough power to put me over the top on power.

I like to make more power than I use thus the batteries stay near full at all times.
According to Calder's it is best to use the least percentage of battery amperage.


Mini-Lesson on Power and Battery Capacity.


I'm going to use round numbers for this explanation. It's easier for me to understand that way...


Your standard *Group 27 or *Group 29 battery holds a certain number of amp hours aka power. For math's sake, let's call it 100 amp hours per battery. With the economical batteries (read: cheap) it is suggested that we never use more than half of the amperage in the battery. Thus our 100 amp battery is only going to provide 50 amps of usable power.

*Group 27 or Group 29 batteries: Batteries are numbered by the external size. Thus a Group 27 battery will be 12 inches long, 7 inches wide about 9 1/2 inches tall. A Group 29 battery is slightly larger. Group 31's are 13" x 7" x 10". The capacity (number of amps/power) does vary between brands.

I opted for the smaller Group 27's. The larger batteries are way too heavy for me to maneuver. The next time I buy more batteries I may chose larger heavier ones as by then I shall be at the "hire testosterone" stage of battery replacement. I won't be able to lift them myself.


Each battery can only be recharged a certain number of times before it fails. There are tricks to rejuvenate batts though long term I have not see a lot of success. It's easier to simply replace.

I do not have the funds to continually replace batteries.

Calder's tome [Boatowners Mechanical and Electrical Manual 4th Edition] recommends we use a smaller percentage of battery capacity. That will allow more recharging cycles.


Each of my 12-volt batteries holds 100 amps of power. I want to use the smallest percentage of amp hours possible in order to have those batteries last. Here's a chart:

(I use 125 amp hours per day in my life of decadence.)

# of Batteries 100 Amps Each Total Amps Using 150* Amps Remaining Amps Percentage Used
3 batts 100A 300A 150A 150A 50%
4 batts 100A 400A 150A 250A 38%
5 batts 100A 500A 150A 350A 30%
6 batts 100A 600A 150A 450A 25%
Me7 batts 100A 700A 150A 550A 21%

*I rounded up to 150 amp hours per day in my chart to account for the extras. Some days I might watch three movies. Or use the microwave for lots of popcorn while watching said DVDs. It's always better to estimate on the higher side for usage.

Trust me when I say we can always find accoutrements for a more decadent lifestyle. I have never heard a boater say they had too much power available.


It is a good idea to have plenty of batteries. It is not just your solar power generation that counts. We have to have a place to store the power. That is the battery bank.

I now have a bunch of solar panels and could not be happier. Recently I added two more 85 watt panels. They were a gift from Bucky. With the addition of those two it matters not if I am at anchor or at a dock. Everything works. Except me!

Behind the solar panel there is an anhinga sitting on a piling to the immediate left of my wind generator.

I now have a total of 445 watts in five panels atop Seaweed. At this latitude with a plain old solar controller I have about 150 amps of power incoming each day. Life is wonderful afloat.


How to figure out how many amps from each solar panel.


Here is a rough way to figure out how much power your solar panel will produce: It's all related to the angle of the sun, closeness to the equator, and cloud cover. This is what I've found:

At the Florida/Georgia border (latitude 30) using a standard solar controller (not the more expensive MPPT controllers that are lots better) the math works out thus: Take your wattage and divide by three. Call it amps.

Panel Watts Total Daily Amps   Panel Watts Total Daily Amps
10W 3A   100W 33A
30W 10A   150W 50A
60W 20A   225W 75A
90W 30A   300W 100A
    Me 450W 150A

Of course if you are closer to the equator you will have more hours of sun and thus get more power from your panels. Conversely, if you are farther away from the equator you will have few hours of sunlight and thus will receive less power incoming.


It matters not if I am plugged into a shore power or at anchor. My life is the same.

EXCEPT I cannot run the wall-banger air-conditioner while at anchor. Well, actually I can run the a/c unit though I must simultaneously run the engine. It has to be mighty hot and muggy for that to happen!

One thing to remember is it is not just power generation you need to deal with. You also must have a place to store the power derived from solar, wind, etc. So as you are thinking about what you require, also factor in batteries.

Aboard Seaweed I have 700+ amp hours in seven batts. I get about 150 amps per day from my solar panels. Additionally I have a wind generator that helps bump things up too when the wind blows.

Note: It is never windy enough if you are like me and anchor close to shore and in the lee of islands. I prefer calm quiet anchorages to bumpy exposed places.

I knew my refrigerator used a lot of juice aka power. How much exactly was the question. A Kill-O-Watt meter will tell you how much power your items consume. In 80 degree ambient temperature my reefer/freezer combination (the smallest made, 3.1 cubic feet by Haier) requires 60 amp hours in a 24 hour period.

P3 P4400 Kill A Watt Electricity Usage Monitor

I bought this unit to determine exactly how much power my cheap a/c powered refrigerator uses. It provides power and time. From that it was easy to figure out amps I need to supply each day for my life of decadence.

Using solar power I know I need to generate 60 amps per day to run the reefer.

Affiliate link.

This was the least expensive one I could find. It has the fewest features. I don't need complicated.
The meter just needs to work.

Side Note: Online was far less costly than in local stores which had the fancy ones. Electrical gurus might want the information those provide. I did not require more than the basics so opted for simple. J.

I generate 150 amps per day with my solar panels. The refrigerator/freezer uses 60 amp hours during 24 hours. That leaves me a theoretical 90 amps for everything else.


Definition of "everything else"

Item (time and power required per hour) Daily Power Required Item (hours used) Daily Power Required)
Computer (12h @ 15w) 20A DVD player (4h @ 24w) 10A
Microwave (30 min @ 700w) 21A VHF Radio (24h @ 5w) 12A
Anchor Light (10h @ .3A) 3A Depth Sounder (24h @ 2.5w) 6A

As you can see, when I add in the refrigerator/freezer (60A) I'm using about 130A per day for my life. The microwave estimate included a couple of bowls of popcorn plus reheating, tea making, etc.

I need to make that much power daily to support my life of decadence.

Could I use less power? Absolutely. Do I want to? Nope. This is my home. I intend to live forever aboard Seaweed. Having the accoutrements of a comfortable life means that will happen. Those that have to "rough it" long term are often left unhappy.

I am woman, over fifty and appreciate things like ice cubes in my tea. A refreshing cool tangerine (Cuties or Halo brands preferred) right from the reefer is such a treat on a warm afternoon. Having lived without those things makes me appreciate them all the more.

Would I go back? No. Make that HECK NO! Life is great aboard my Seaweed.
Yes I am spoiled. And grateful, blessed, fortunate and so happy to be here.

It's wonderful on the water...

When starting out you do not need to have Everything. What you do need is a plan.

The plan for Seaweed included a wind generator and solar panels. With the current solar panels (455 watts generating 150A per day) I'm set. Life for me is no different at anchor in a remote cove than it would be when tied to a dock with a power cord.

Actually it's better at anchor. The only neighbors are fish, birds and dolphin. There is a simplicity of life at anchor. Days start when I wake up. One day that might be at 0400 and the next it could be nearly noon. This retirement thing is Awesome!

To get where I'm at you're going to have to buy some goodies though. You'll need solar panels, a solar controller (it puts the correct voltage of power into your batteries) and an inverter. An inverter turns DC battery power into the stuff you use in houses: 120 volts of AC.

My second solar controller was a Morningstor30.

About Solar Controllers: They are rated for specific wattages. Originally with my 75 watt panel I had a Morningstar10. It could have handled a 100 watt panel. The Morningstar30 shown above would work fine for up to 300 watts. Later with the addition of the two newest panels I upgraded to a MPPT60. It will support up to 600 watts of solar.

For further information on the differences between the two types of controllers, the Solar Regulators (Standard vs. MPPT) article would be worth a read.

Life is wonderful afloat. To keep up my standard of decadent living, I need to generate just less than 150 amp hours per day. My solar panels deliver that. The power is stored in my battery bank.

In order to use the power gathered by the solar and sent to the batteries by the solar regulator I needed an inverter. Originally I opted for an AIMS1000 from The Inverter Store. It worked right well until I upgraded to a microwave.


You will discover that each new addition brings unexpected consequences.

The desire for ice cubes meant a larger refrigerator. Then the silverware drawer and those lockers needed to be removed for the refrigerator. Details on the refrigerator install can be found in the
Securing a Refrigerator (fans too) article.

Since the reefer was now in there was a lovely (perfect really) spot for a microwave.

Then I tried the microwave with my old-style inverter. The microwave didn't work. So I needed a new and better pure sine wave inverter. And it will have to be wired as it has some automatic switches in it...

You get the picture. Each change though perfectly logical and sensible meant more complication and bother. In the end it's worth it. In the midst it is definitely trying.

Not to mention swapping engines during the whole improvement fiasco.

It's good that I have a sense of humor and a dog. Skipper helped me though the rough patches when my world was helter-skelter. New friends and old were a serious boon.

I truly am blessed.

Old and Ugly:
New and spiffy with a microwave too!

The new larger refrigerator is just perfect. With a separate door for the freezer I can make ice cubes. I am totally enjoying this upgrade.


Mini-Lesson on inverters: There are two types of inverters. Square wave are the least expensive. I have used a square wave AIMS1000 for years and it is a-okay. It powered everything on the boat until I bought the digital microwave.

The best prices for inverters I have found is at The Inverter Store.

The second type is a Pure Sine Wave inverter. They are twice the price and if you need one, you need one. Let me explain:

The pure sine wave units are the best. They mimic exactly the power you get in houses. Pure sine wave inverters will keep your electronics in tip-top shape. There is virtually zero difference between the power they generate and standard power found at a house.

Electrical gurus will state unequivocally that the higher priced pure sine wave inverters are best. They do not damage electronics and electric items perform better with purse sine wave inverters.

The square wave work okay for many things. Generally speaking, anything with a digital control will not work with a square wave inverter. The type of AC power cheap inverters produce is similar to but not exactly the same as house power. Some stuff will work anyway.

Is it great? No, but the square wave is Good Enough provided you have no sensitive items. Mine did very well powering the computer, crock-pot, refrigerator, and my Christmas tree lights.

Other items won't work. My microwave makes a sound, the turntable spins and nothing heats up when using the original square wave inverter. The square wave inverter powers my a/c unit just fine. I suspect because the air conditioner has a dial versus digital control, that is why the inverter powers it without issue.

The microwave and my popcorn addiction [see Popcorn for One (and Stone-wave Update) article] means I needed a Pure Sine Wave inverter.  My AIMS1000 I will pass along to another boater. It works, just not for my particular application.

There are actually three types of inverters. Inverter/chargers are also sold. I'm not fond of those. For me two separate units means that when one part breaks I can simply replace the component. I have a separate charger for the batteries when I'm tied to a dock.

Having real estate for solar is important. For those who have limited space an expensive MPPT solar controller will increase the power your solar panels put into the batteries. The less expensive controllers work too. They are simply not as efficient as the MPPT controllers.

Solar charges batteries through a solar controller. Batteries supply power to inverter. Inverter changes battery power (12 volts) into AC (120 volt) power like you'd have in a house.

All three components have to work together.

Start small. Solar to batteries to 12 volt items. THEN move up and start with your AC side of the boat.

The best visitors just want to sit around and relax. They don't care what power system you have.

Note the Night Heron sitting on the rail of the boat rafted next to me.

If you're like me you will find that buying a cheap throw-away refrigerator for $150 is better economically than spending $700 or more on a small 12-volt one. When mine quits I'll go to Walmart and buy another.

Years ago (pulling on old-fogey slippers) "everyone" switched over to 12-volt items. It was the "newest and greatest" thing. We stopped using iceboxes (with blocks of ice) and life was good. Then, well, things changed.

The DC refrigerators (reference Engel for instance) are wonderful. They are also way beyond my budget. By increasing gradually the amount of solar I have, I am now able to buy and use any item off the shelf from regular stores such as Walmart.

I do not need to buy expensive "Marine" items.


If you would like to duplicate the solar system I have aboard Seaweed, here is your shopping list:


 2pcs 100W Mono Watt 100W 100Watts Off Grid 12 Volt 12V RV Boat USA Solar Cells

Renogy is the brand I chose. Good prices and fast shipping from Amazon. When I ordered I had to have a street address for shipping via UPS.

 MorningStar ProStar PS-30M PWM Solar Battery Charge Controller, 30 Amp 12/24 Volts

(I now have an MPPT60, a better albeit more expensive controller)


P3 P4400 Kill A Watt Electricity Usage Monitor

Plug it in, then plug your appliance into the front. The meter will tell you how much power is used. There is an elapsed time button so figuring power consumption is easy.

2 Wire Blue DC 4.5-30V LED Panel digital display Voltage Meter Voltmeter By BuyinCoins

I use voltage meters to monitor my battery state. I have several scattered throughout Seaweed so wherever I am I can tell what my power situation is.


You will also need wire. I cannot tell you the size as your boat most likely will be larger. Longer wire runs require a bigger gauge wire than the short runs aboard Seaweed.


BEFORE you spend the first dime however, make sure you like life at anchor. If you're hopping from marina to marina there is no need to expand your power creating beyond that of the alternators on your engine. Solar is one answer for those of us who prefer life off the grid.

I love the quiet, and I like my ice cubes too. You really can have it all. It just takes work and determination.

This is the life:

P.S. - I am NOT a power expert. I'm relating the experience I have had while out here for the past 8 years.

Currently (April 2016) my Comments are broken. Fortunately folks have emailed input, so here you go:

From Cap'n Todd:
1. MPPT controllers - These controllers are great IF you have multiple solar panels wired in series. If you only have one panel or have your panel wired in parallel there is very little benefit to an MPPT controller versus the much cheaper PWM or simple on/off controllers.

2. Actually during the summer we have more hours of sunlight up north than you do down south. For example right now you have about 13 hours of sunlight a day while here in Maine we have about 14 hours. In late June we will have almost two hours more sunlight each day than you do. The difference is in the sun angle (ours is lower). That matters for horizontal fixed panels, but in late June/early July we will not be far behind you in power from our solar panels due to our longer days. If you have solar panels that are angled to account for sun angle (doesn't work on the hook), you can do better here than down south during the summer. However, that requires an active sun tracking system which takes power to run and will reduce useable output and will break down now and then. It is an option for the dock queen type boat, but not needed if there is shore power available.

Do you use other means of power generation such as a generator, alternator?
What provides the majority of your power when away from the dock?



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