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Old 11-02-2013, 07:42 AM   #21
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Propane refrigerators are like anchors and the twin versus single engine discussion. They will be discussed/debated forever.

The advantages of a propane refrigerator are obvious. Where propane is available the electrical consumption is significantly reduced.

The downside of these refrigerators is a safety issue. Propane refrigerators are popular in North American among RVs. The difference with an RV and a boat is that leaking propane will spill out in an RV and will collect in the bilge for a boat. Normal use of a propane stove/oven on a boat is occasional for perhaps an hour or so a day. Usually with someone watching. The 24/7 use of propane for a refrigerator means any leak in the system will likely result in disaster.

Anyway those are a couple of the issues as frequently discussed. I know boaters with propane refrigerators and others who feel they are unsafe. You must make your own decision.

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Old 11-02-2013, 10:33 AM   #22
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...... using an inverter to create 120V would be more inefficient than using a Danfoss 12V real DC fridge.
I can't confirm that the above statement is true, as what I know about electricity can be put in a thimble. What I can confirm is that the PO set up my boat as described above by FF. I have a 3000W inverter that runs all my 120v needs. He replaced the 12v/120v frig with a cheap Sears 120v unit. Along with an ice maker (also 120v) and no generator, I can easily go a couple of days without any need to recharge the house batts. If more marina hopping or short cruises are in my future, I'll add a Honda or Yamaha small generator.
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Old 11-02-2013, 12:13 PM   #23
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>using an inverter to create 120V would be more inefficient than using a Danfoss 12V real DC fridge.<

ON A PROPANE fridge we were discussing using 120V !.

The old 12/120 camping fridges (like a Norcold) were fine in there era.

It is possible that a 30 year newer sears cheapo could use less juice than one of these older units, even with inverter loss.

A MODERN DC unit , with a modern DC computer controlled compressor will use less juice than the inverter + sears cheapo.

>I know boaters with propane refrigerator and others who feel they are unsafe. You must make your own decision. <

The difficulty in installing a propane unit in an existing boat , is that the unit must be in a deep (at least 6 inch) tray that is gravity drained to outside above the WL.

Impossible with some galley down builds , fairly easy if the base of the fridge is high enough from the WL.
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Old 11-02-2013, 04:29 PM   #24
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The difficulty in installing a propane unit in an existing boat , is that the unit must be in a deep (at least 6 inch) tray that is gravity drained to outside above the WL.
Hmmm. I didn't know this and it makes absolute sense. My refer is mounted atop a box built for several anti-siphon loops in the machinery space beneath. It is, however, well above the waterline. I could manage the construction of such a pan and drain overboard without too much problem. That's a very sound safety precaution. I suppose a downward angle on the drain overboard would be most preferable as well, yes?
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Old 11-02-2013, 08:19 PM   #25
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Solve the reefer problem and the rest is EASY!!!
That is so right. And why people go the propane route.
Running a big fridge on AC from panels is a huge ask. In practice I`m ok if I get 50% of theoretical panel output. There must be some huge battery banks out there for it to work.
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Old 11-02-2013, 08:50 PM   #26
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That is so right. And why people go the propane route.
Running a big fridge on AC from panels is a huge ask. In practice I`m ok if I get 50% of theoretical panel output. There must be some huge battery banks out there for it to work.
On cruisers forum there is a guy on a performance 44ft sailing cat, so not a huge roof space and weight would be an issue so it wouldn't be an overly heavy battery bank either.
He says:

Quote:
To add some real world experience as opposed to ignorant monocular ranting, we've now been running a domestic fridge and freezer off an inverter for two years, with no problems.

Fridge and freezer cost just over $500 Au for the pair. 1500 Watt PSW inverter cost $310 each. I have two, in case one fails. (I also use the spare to run the breadmaker, a washing machine and any power tools etc..)

Power consumption is a bit higher, but not massively so compared to my last boat's marine fridge. (When it worked) I can run the entire boat, including watermaker, breadmaker etc, off the 600Watt solar array, with MPPT controller.

I've been told most 12 volt refrigeration compressors use capilliary evaporators, while 240 volt use thermal expansion valves, which are more efficient. Which might explain the small difference in power consumption. Don't know how factual this is though...

And the whole lot was cheaper than buying the guts of a marine fridge, and having to build my own cabinet around it. And then I'd still have to find the amps to run it.

I can't say whether this setup would work in a mono. Not much about them does seem to work, so possibly this type of refrigeration wouldn't either.

Flat batteries overnight? Not even close.
Can a Household Refrigerator Work on a Sailboat ? - Page 4 - Cruisers & Sailing Forums
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Old 11-03-2013, 06:04 AM   #27
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Some numbers from Bay Pelican:

Two 1999 Subzero under-counter units, 4.5 cubic feet each, one refrigerator, one freezer. 24 hr usage approximately 400 amp hours, based on Kill a Watt readings of the 110 volt ac usage.

Replaced with two Isotherm 110 volt/12 volt units with Danfoss compressors. Usuage approximately 160+ amp hours based on ammeter readings and some guess work for the 110 volt usage during the 3/4 hour the generator is on.

Two units combined draw between 3 amps and 8.5 amps 12 volt DC depending on whether one of both compressors are on.

Note the ambient temperature is usually in the low 80s F, high 20s C. The Isotherm freezer is slightly smaller than the Subzero was.

For someone living at anchor, as we do, this was an enormous improvement.

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Old 11-03-2013, 07:22 AM   #28
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For folks with daily noisemaker hours a large ,,engine driven compressor or 240V large compressor with TX valves will freeze a eutetic plate ....IF the box it is in has good insulation.

This is the old sailboat method , and does work great but there are downsides.

Usually the box must be custom built top loading to get 4-6 inches of good freon blown insulation.

4-6 inches of insulation makes the box smaller inside , so a larger area to build the box is required.
The eutetic plates are frequently 2 ft square and 3 or so inches thick, which eats more internal room.

Our performance on out 90/90 is it takes 2 hours of engine (Volvo MD 3-B) time to bring both the freezer and fridge plates to proper temperature , about -10F in the freezer to freeze 0-F deg plates.

This lasts 4 days , so every 3 days we change location with at least 2 hours of engine time.
AS I refuse to idle the engine to death , if we wish to remain in an area we buoy the anchor with the dink and simply cruise the local area under power.

All this is heavy , compressor , heat exchanger and multiple eutetic plates , but so are multiple battery banks.

There is NO sound from the brine solution melting in the plates , so its silent boat as soon as the engine is secured .

For someone with experience the entire system can be home brewed , should initial cost be an objection.
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Old 11-03-2013, 09:55 PM   #29
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Parmenter,
It can be done but YOU MUST KNOW how much power the fridge PLUS all the other loads that you expect to run will use.

I think one of the very first things you should do is purchase and install a SOC meter and get it going immediately. There are other ways to estimate real power useage but this thing will tell you without all the estimates. If the fridge, your 120Vac unit is only on 120V when at the dock then another purchase might be a KILL A WATT meter. P3 International P4400 Kill A Watt Electricity Usage Monitor - Amazon.com

Then you will have a good reading and using the results of both as required you can come up with a plan.

If you are currently running the fridge from an inverter run from the batteries then the SOC will give you what you need. If you run the fridge separately then both may be required and then do the calculations to figure all out.

A story I've told before but here goes again. A friend, a retired EE, set up his boat to do without a gen. He does carry a 2K watt Honda for emergencies but seldom uses it.
3X 135 w solar panels run his boat and by 14:00 hr on a sunny summer day here in B.C. Canada his batteries are recharged. His panels are flat mounted with no provision for a tilt to follow the sun which in most cases at anchor is useless.

He has a 12vdc full size single wide combo fridge/freezer fridge and a 12vdc Waeco chest freezer. Both use the Danfoss compressor, the BD35 which when running draw about 4.0 - 4.2A. I don't know what the duty cycle is but I would guess based on my Danfoss , in hot weather about 60%.

He uses 6 X golf cart batteries for a bank of about 660A/Hrs. They have all the other stuff aboard , water pumps, lighting, radio, and whatever else they need. The system keeps up as long as they get the sun each day.
I BELIEVE they can actually go 2 days if one is cloudy because of course the panels still pick up enough to get through to the third day. After that they may need to run the boat or the gen. On a cloudy day, not rainy, he still gets 20-40% charge, I believe, but it is down, depending on cloud density.

I should note that he did things a bit differently from many. His systems panels are wired in series so the panel set sends a nominal 36volts to the controller. He bought the controller of course to take that into account + it self adjusts for voltage.

Read his thread Albin Owners Group &bull; View topic - Solar Panels

It's on the Albin forums. You should not need to sign up just to read the post.

Your useage may be different so YOU need to find out how much power the fridge uses for real, allow for ~ 90% only inverter efficiency, and how much other power the rest of the equipment you need to run uses. The SOC meter and if needed the K a W meter. He did this after the first years use so he had a good idea what was going on + he had that SOC meter as a big help.

Then decide how many days you want to be able or need to go without running the boat or a gen. You must take into account those cloudy days. That can be done by adding another panel to whatever you think is needed, extra battery capacity or both. Both would be better of course but I realize cost is also a factor. Initially batts. I think if you have the space and purchase a controller that can take extra panels over the initial purchase. Of course you must have the space for both batts and panels.

He used 135W panels but there is no reason a different capacity panel could not do the same. He had the area to cover atop his Bimini cover and the 135 were perfect and covered all available space. If you have more space then even better. You can go longer if the SYSTEM is thought out and put together correctly.

Your specific fridge will have a huge amount to do with this. Poor insulation, typically house fridges are not as electrically efficient ,total watts used, as dedicated boat fridges, poor ventiation to get rid of heat where the fridge is mounted but it can be done.

For the system overall though one of the best things to do is reduce electrical load. LED lighting will help a lot. A small muffin type fan to evacuate the fridge cavity cast off heat. Set it up so it runs only when the fridge runs. If the fridge can't get rid of that heat it can't cool the interior and it will run and run and run.
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Old 11-04-2013, 06:02 AM   #30
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IF the panels are going on a Bimini mount , some are dual surface and will put out juice from reflected sun light UNDER the panel.
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Old 11-09-2013, 07:36 PM   #31
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Solar Powered Refrigerators
I have a 19.5 cu. ft. GE no frost refrigerator/freezer (Model TFX20RH) built in 1987 aboard my boat. On May 20, 2010 I tested the power consumption using a Kill-A-Watt meter. The test lasted 67 hours (2.8 days) with a power consumption of 9.54 kWh (142 watts average). Temperature of the interior of the boat was 70-80F and temp of the interior of the fridge was about 45F. The freezer part was about 25F.
So a typical 20 cu. ft. mid 80s refrigerator burns about 140 watts at 120 volts. Today similar fridges are much more efficient with power consumptions of as little as 50 watts.
So if you are trying to solar power a refrigerator figure 50 watts for a new 20 cu. ft refrigerator. If you've got an old beastie refrigerator from the 80s figure nearly triple that. So the obvious answer from the standpoint of keeping the solar panels small (and cheap) is to buy an effiicient new fridge. The cost of a good 20 cubic foot refrigerator/freezer can be as much as $1,400. But if you can cut back on the frills and size a good fridge using as little as $25 watts can be had for under $500.
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Old 11-10-2013, 06:55 AM   #32
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50 watts at 12V is about 4 amps , figure 5 for wiring and inverter losses.

At 24 hours a day thats 120 amp hours , which requires 240 AH batteries on a cloudy day.

Simply replacing 120 AH will require 150AH of solar or wind as batterys need energy to be charged.

Solar can work , but its a challenge , not a bolt on task.

To shop for a fridge there will be an annual KW number on the new units , simply divide by 365 to find the KW per day.

This is a very LOW estimate as most thin wall insulation in modern fridges require heating strips to defrost the insulation , and door seal.

And of course the unit mfg have permission NOT to count this power in the annual.

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Old 11-10-2013, 07:58 AM   #33
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Yes, you can power the fridge using solar. I recommend shopping for the latest refrigerator/freezers made in Japan such as Hitachi. These units are super efficient with multiple doors and drawers to avoid heating up each time you open up for a cold beer. Using the annual cost figures (yellow tag), you can estimate daily watts - our 14 civic foot Uses about 35 watts/hour.

Second - get efficient inverter - as close to 90% as possible.

Third - if space for PV array is generous, you can install less expensive, less efficient panels. We have Sun Power , the most efficient. We feet our chargers at 80v by pairing the panels.

Fourth. If your budget allows, use LiFePo lithium cells to make as big a battery as space allows. The cost of ownership of a LI battery is less than AGM if you use it. Compare less than 500 lifetime cycles vs. over 3,000 for the LI.

Our DSe "Sunshine" has 6,000 watts of solar, 2 each Outback 60 amp controller chargers, 2 each Outback 3.6 kW inverters and 1,000 AH/48v LI battery. All domestic power is sun generated including induction cooktops, air conditioning, refrigeration, pumps, hot water, washer-dryer, entertainment system and LED lighting.

The key to a successful system is doing the math up front. More battery is better than less. A bit of wind power is a good idea, too.
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Old 11-10-2013, 11:19 AM   #34
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Shore Power Independence
You guys who are trying to run your boats totally on solar power thereby eliminating the generator are missing the point. Nearly all modern motoryachts are already equipped with a generator. And solar cells don’t provide enough power for the galley loads, water heating or air conditioning. What you really want is called shore power independence; the ability to operate your yacht away from shore power cables attached to a dock.

My Connie is already shore power independent. It has a 20 KW generator and 600 gallon fuel tanks. If I reserve 200 gallons for the engines, that leaves me with 400 gallons for the genny. It burns about 1.0 gph at full load. But at half load (10 KW) it only burns about Ĺ gph. So at half load I can stay away from the dock for 400/0.5 = 800 hours. That’s almost 33 days of continuous running. But during the evening I burn very little power (probably less than ľ of full load) so with a little effort to conserve power I can probably stay away from the dock for 45 days (a month and a half).

But by now you guys are probably saying “Who the hell wants to put up with the noise, vibration, fumes and smell of a diesel genny operating 24/7 for a month and a half?” The answer is “Not me!”

How do I get around it? The answer is I run the genny only 8 hours a day at meal times; breakfast, lunch, dinner and midnight snack. And while I am running the genny I take care of charging a 480 AH set of four 6 volt 120 AH golf cart batteries. With a 3 kW inverter this battery bank takes care of all the 120 volt AC loads during the periods when the genny is off.

The genny has to be on at all meal times anyway to handle the galley loads (unless you are willing to survive on baloney sandwiches). With 20kW to work with I can easily take care of all the other high power loads, water heating, clothes washing/drying, battery charging, partial air condition, etc. Windmills and solar panels? I don’t need them and I don’t want to pay for them. I don’t think that most of you that have generators need them either.

For those of you heavily into the shore power independence kick I recommend The Voyager’s Handbook. This is a book written by blue water cruisers who cross oceans and circumnavigate the world. They obviously have to be shore power independent. It’s a 570 page tome filled with graphs, figures and pictures which describes just about anything you would want to know about ocean voyaging and shore power independence. I bought my copy in 2011 for $42.35.

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Old 11-10-2013, 01:26 PM   #35
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Pete. This thread started with the question can one run a fridge using only solar power and avoid the need to install a generator. The skipper asking obviously doesn't have a generator at present and is seeking an alternate solution.

As you say, most yachts come with a generator and yours has a. 20 kW. Of course, the path of least resistance for you and most others is to simply turn on the generator when needed, rationing power when it 'a off. Makes sense.

The question was can the jobless be done and is it being done with solar in the absence of an on board diesel or gas generator.

And the answer is,"YES!"

In addition, cooking, air conditioning and other domestic tasks can also be done using solar alone, or solar plus other forms of power generation.

One last thing, your 400 gallons of diesel is over $1,500 each time you replace it and your generator is a bit noisier than solar. I'm not suggesting you invest the time and effort to convert, but for someone starting with a clean sheet of paper , solar and wind are viable alternatives for some boaters.
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Old 11-10-2013, 05:23 PM   #36
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Running Household Fridges on Solar Panels

A previous post asked the question “Can you run a household fridge on solar panels?” I assumed that what he meant was “Is it practical to run a household fridge on solar panels?” Obviously, if you have unlimited money you can run the fridge on solar panels. But few of us have unlimited funds. I’ll try to answer that question in the following paragraphs.

A 100 watt Sunforce Solar Panel costs about $360 (West Marine). The realistic daily output from four of these panels in bright sunlight in the tropics is about 100 AH @12 V (p235, Voyagers Handbook). This assumes that the orientation of the panel is nearly perpendicular to the surface of the panel. That’s not too difficult to do on land but on a rapidly moving boat you can only expect about half that amount (50 AH). 50AH at 12 volts is 5 AH at 120 volts or 600 watt hours (0.6 kWh). An efficient 20 cu. ft. refrigerator/freezer burns about 60 watts and over a 24 hour day it will burn 1440 watt hours or 1.44 kWh. So just to keep up with the refrigerator’s load you will need about (1.44/0.6) x4 = 9.6 panels at a cost of 9.6 x $360= $3,456. And this is in the tropics. In the mid-latitudes the array and its cost might have to be twice as large.

Each panel is about 4’ x 2’ so your total array is about 8’ x 4’ and must be mounted on a two axis gimbal to keep it perpendicular to the incoming solar radiation. To keep the solar array size manageable you are probably going to have to reduce the area by a factor of two making it about 2.82’ x 5.6’; still a pretty unwieldy array; particularly in a 20 knot breeze. And since the area of the array is only half as much you’re are going to have to reduce the size of the refrigerator to something like 10 cubic feet; Not exactly household size; more like picnic size.

The reduced array size will fortunately reduce the cost of the panels but the cost of a custom made two axis steerable mount will more than eat up those savings. I think the whole array system (panels plus mount) would cost $3k to $4k. And add in $800 for a bank of batteries/battery charger/inverter system plus another $600 for the fridge and you’re well over $5,000.

Logistically, steering the array is going to be a major problem. The boat is pitching, rolling and yawing but if you don’t keep the array nearly normal to the incoming solar radiation the power drops off dramatically. In dead calms steering the array may not be a problem but in any type of sea steering the array will require a second helmsman. You’ve got to steer the array as well as the boat.

And of course at sea you can have several days (perhaps even occasionally a week) of cloudy weather when the solar panels will produce next to nothing. This will require a huge battery bank to store enough battery power to get you through these periods.

The answer to the question “Can you run a refrigerator solely on solar cells?” is “Yes”; provided you have a large enough array and enough money to pay for the solar array and all its accessories”. If you asked me whether it was practical the answer would be a resounding “No”. A generator would be cheaper, more reliable and more practical. Plus, It can run 24/7 regardless of the weather.

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Old 11-10-2013, 07:50 PM   #37
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Pete. This thread started with the question can one run a fridge using only solar power and avoid the need to install a generator. The skipper asking obviously doesn't have a generator at present and is seeking an alternate solution.

As you say, most yachts come with a generator and yours has a. 20 kW. Of course, the path of least resistance for you and most others is to simply turn on the generator when needed, rationing power when it 'a off. Makes sense.

The question was can the jobless be done and is it being done with solar in the absence of an on board diesel or gas generator.

And the answer is,"YES!"
Thanks for the valuable information provided.

The vessel will be based and cruised in Northern Australia and SEAsia, so equatorial waters

The vessel I was looking at had a genset, but it didnt work and was in need of rebuild.
Rebuild costs in Australia would certainly run into the $5's if not $10's of thousands and buying a new one would probably be more viable.
Then there is daily fuel usage

200watt solar panels are available on ebay here for as little as $200 (possibly even $160 Click Here
An efficient 300 to 400 litre 240v fridge freezer is available for around $1000 - $1500 here.

An efficient 12 volt fridge freezer is $3000 plus here and looks like a 1960's icebox.
Also it would only be 120 litre, so 2 if not 3 would be required.
3 things to go wrong and a $10,000 purchase price.
If going no solar add in $15 to $20,000 for Genset

That buys a hell of a lot of $200 panels for running that less efficient fridge freezer and when/if it gives problems WORST case scenario is I throw the fridge away and spend another $1500.
The 12 volt fridges may cause all sorts of problems, my cruising observations would show marine refrigeration issues to be very common, so spending large dollars on a potentially troublesome item to me makes little sense.
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Old 11-10-2013, 08:45 PM   #38
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Since I've already spent a great deal of money and time to transfer my genset to a new hatch under the veranda from it's hell hole under the galley, I've no intention of getting rid of it, but I've also spent an equal amount of time and money re-skinning my roof and clearing it of other devices for solar panels only. My plan is for installing 1340 Watts of panels to drive my Dometic fridge, pumps, lights, and to charge my two 8D house batteries till they wear out and I change them out for LI units as Rubin suggests. Of course, I'm in FL and that means a lot. I'll run the genset for A/C. Hot water will come from another solar panel and insulated storage tank specific to that need.

With todays tech, it seems to me that reasonably economic compromises in appliances and solar/wind are becoming abundant the same time (thanks to China), especially in relation to the overall cost of boat ownership. The points that Pete has made about direct sunlight are legit, but panel design is improving. I'm looking forward to the day that I have to start and run my genset as a maintenance requirement rather than a need.
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Old 11-10-2013, 08:59 PM   #39
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The state of the art fridges from japan such as the hitachi use inverter technology for their variable speed compressors maximizing efficiency. And typically, a household fridge runs years without any service.

Look closely at building a LI-Ion battery - cost is about $1/AH (3.3v cells - $4/AH at 12v). This is about 2 times the cost of the best AGM batteries but is about 40% the mass (per AH) and has 6 to 10 times the life expectancy in cycles. 400 AH at 12v should be enough. More is better. The bigger the battery, the less wasted solar energy. With a lithium battery, you'll need a battery management system - ideally one that can communicate with solar chargers AND the inverter (Victron makes one that does this).

Sun Seeker Lite is an iPhone app that calculates the elevation of the sun during the day depending on your latitude. You can take this info and calculate the angles of the sun from the vertical. This is the angle the sun hits the panels assuming the panels are mounted flat. (The only practical way). Take the cosine of this angle and multiple by the rating of the panel. This gives you the maximum possible output of the panel.

I feel you actually will see about 50% to 75% of this number of real useable power. Based on your latitude and number of sunny days, you should be able to get a good idea how big the PV array needs to be. Again, err on more rather than less, depending on space requirements.

I think Victron also has solar controller/chargers?

We used AGM batteries for 4 seasons. They wee OK. Last year we replaced with Li-Ion which is fantastic. We now have a single 48v/1,000 AH battery that weighs 1,250# (same weight as 400 AH AGM).
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Old 11-10-2013, 11:43 PM   #40
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Hi Reuben,

Your right that household fridges last a long time. My GE refrigerator/freezer on the boat is 27 years old and running fine. And I have another (not on the boat) that's even older. The problem with the old fridges is not longevity it's that they're not efficient. So I should change the old fridge out. But that costs about $1500 for the new fridge plus another $500 for removal of the old unit and installation of the new. But as long as I charge the batteries with a generator, efficiency isn't important so I guess I'll continue to use the old fridge until it craps out.

My ordinary wet lead acid batteries last about 8 years so even with old technology I'm not worried about lifetime. And at $200 for a 12V 250 AH 8D ($0.80/AH) they're cheap. Building a LI-ION battery might be an interesting hobby project but I really don't need one. The old batteries work fine. If I were launching my batteries into space weight would be important but on a 54,000 lb. boat the weight is noise level. And again, since I'm charging the batteries with a generator, maximum efficiency isn't important. And my old lead acid batteries don't need a battery management system.

I have tables from Bowditch that give the elevation of the sun. Not as cute as the app but it works and since I don't have an iphone they may work better anyway. But thanks for the tip.

Putting your solar array on a flat horizontal surface makes a lot of sense. That way you don't have to steer the array; a big cost saving. But the only semi-flat horizontal surface I have for the array is the top of the lower salon which gets a hell of a lot of salt spray and it also means that in the early morning and late afternoon your array is essentially useless. Horizontal arrays only give you about 6 to 8 hours a day of useful output. Plus, it's my wife's favorite place to sunbathe. I may have problems kicking her out. But if I can evict my wife I may try the horizontal array route. The steerable array while more efficient is a logistical bummer. But again, as long as I charge my batteries with the genny I don't need a solar array so perhaps my wife can keep her sunbathing spot.

I'm getting older and lifting out the 135 lb. 8Ds is beginning to be a problem. If they were in an easily accessible place lifting them out wouldn't be a problem. But they aren't and I'm finding that hiring a $10 an hour grunt to help me with the batteries is a lot cheaper than a trip to the doctor. How the hell do you get a 1,250 lb battery out of the boat? I'm assuming it comes out in pieces. Or do you have a special crane?

Pete37
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