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Discussion Starter · #1 ·
I'm in the process of designing a solar system to power an Engel refrigerator/freezer and keep a Group 27 battery (also used to power occasionally used inverter) charged.

I've decided on a 140W panel and am thinking of mounting it - independent of my bimini - on a vertical, twin pole platform that is about 1' aft of the stern pulpit.

The size of the panel is about 51 x 27. I was planning on mounting the framework to a piece of 1/4 or 1/2" starboard with on inverted deck flange at each end and then mounting the Z-brackets that come with the panel to the starboard.

The mount would be 7/8" stainless with the two vertical poles tied together with a horizontal brace.

Questions:

  1. Is the starboard desirable for having a rigid mount or should I just attach the solar panel to horizontal runs of tubing?
  2. Is it desirable to have whatever mount I use adjustable or is completely flat acceptable?

Murph

S/V Amalia
1965 Cal 30
Muskegon, MI
 

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First thought is that, while a 140W panel will easily keep up with the fridge during daylight/sunny weather, a group 27 battery is unlikely to get you through the dull/dark periods for long, esp if inverter loads are included. I'd be looking at upping your amphour capacity by quite a bit.

Starboard is rather heavy.. don't see the need to use as part of the mount. If you incorporate the ability to tilt the panel you will greatly enhance it's output if you pay attention during the day.

Hard to say from your description but on the face of it your support plan may be a bit wobbly.. esp with the added weight of starboard...
 

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Murph;

A few ideas for your consideration;

Adjustable/moveablefor light placement/collection
Removable easily for stowage
Lightest weight with best possible strength and mounting options

Perhaps a Bimini-type frame with twist-adjusting back rail frame length?. Utilize Bimini hardware available and a pair of HD or Lowe's cheap alum painters poles for the back "legs" as adjusters? Ditto on losing the Starboard; both weight and windage excess. Deck flanges possile; but add a pairof opposing angle, fore/aft braces. 30,45 and 60 degree rail hdwr is common enuff . Pull-pins 'stead of bolt-on brackets?
Unless your planning on TransPac length reaches; you're not going to deploy while underway (?). Mooring/slip use willmake install/useage much easier to facilitate,; both manufacturing and design.

I'm going thru the same design/mental gymnastics for my future installation; soI can sympathize :D

HTH,
Paul
 

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Discussion Starter · #4 ·
With Paul & Ron's comments, and a bit of further research, it seems that there is no need to use starboard since the panel is well supported by just being mounted at the edges.

I found a website that offers lots of mounting options and will likely come up with something like they show.

While I can add to the battery bank and likely will, my loads are actually fairly small for a 140W panel. The Group 27 is 115 Amp Hours. At 50% charge limits, it could power the refer for about 6 hours with no input from solar.

Most solar planing says that 5 hours a day at rated output is what you can expect at average which is about 700 Watt Hours. Assuming 2.5 A with a 33% duty cycle, 12 V and 24 hours (about .8 Amp Hours per hour) it looks like the Engel will only need 240 Watt Hours for the whole day.

As to the inverter, that load is very intermittent and it will likely be turned off except when I need to use the microwave, coffee pot or electric tea kettle.

If I can, I'm still thinking about mounting it independent of the stern rail, but won't be able to really decide on mounting until I make the commitment to buy the panel, charge controller and the other stuff.

Thanks for your thoughts.

Murph
 

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As to the inverter, that load is very intermittent and it will likely be turned off except when I need to use the microwave, coffee pot or electric tea kettle.
Umm, I don't see that working out well for you. You'll probably need a Honda generator to run those things. That or just use the propane stove to heat your water and food.

I'm skeptical that one grp 27 is going to live long running a dc fridge.

Ralph
 

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A common problem with an inverter of 1800 to 2000 watts - needed for the use you describe - is that the inverter often shuts down due to low voltage if the battery bank is too small. An inverter supplying 1000 watts is consuming 100 amps DC. A single group 27 battery can only sustain that for a few minutes.
 

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islander bahama 24
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Myself I would split the panel output between two panels so in the event of a problem or shading I still have at least half of the total output available at any one time at the same time it splits the base loading on the mounting to two separate locations something like this would work great Complete Kit 200 Watt 200W Poly Solar Panel 12V 24V Battery RV Boat Off Grid | eBay however as many have stated I agree a bigger battery would be bettsr
 

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I just used 1" stainless steel tubing to make a rack for my two 140 watt solar panels. At first I had the two aft poles attached to my pulpit and the two forward poles attached to my bimini.

The next tropical storm, when I wanted to take my bimini down, I realized the engineering faux pas I had made at that point. I then re rigged it where all four vertical poles were attached to the stern pulpit. The only thing I don't like is the sag in the two horizontal poles that the panels are actually mounted on. It doesn't hurt anything, I just don't like the way it looks.

In other applications, I had driven a 7/8 tube through the 1 inch tube to make a much more rigid pole and I wish I had done that on this one. There are (at least) two grades of 1" stainless tubing (one with thicker tubing than the other) and the 7/8 tube will fit inside one, but not the other.

The other negative with my mount is that my panels can't be adjusted to more squarely face the sun. But, I have noticed at extended anchorages, how few people who have the adjustable panels, actually continually adjust them to face the sun. :)

And, as mentioned before, you have to have a controller for big panels like that or they will overcharge your batteries at times.



The angle of the shot makes it look like the boom won't clear them, but that's an optical illusion. It may not be the perfect way to mount them, but it was pretty easy and it's worked for me for four years like that (not counting the above noted modification I had to make).
 

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I'm in the process of designing a solar system to power an Engel refrigerator/freezer and keep a Group 27 battery (also used to power occasionally used inverter) charged.

I've decided on a 140W panel and am thinking of mounting it - independent of my bimini - on a vertical, twin pole platform that is about 1' aft of the stern pulpit.

The size of the panel is about 51 x 27. I was planning on mounting the framework to a piece of 1/4 or 1/2" starboard with on inverted deck flange at each end and then mounting the Z-brackets that come with the panel to the starboard.

The mount would be 7/8" stainless with the two vertical poles tied together with a horizontal brace.

Questions:

  1. Is the starboard desirable for having a rigid mount or should I just attach the solar panel to horizontal runs of tubing?
  2. Is it desirable to have whatever mount I use adjustable or is completely flat acceptable?

Murph

S/V Amalia
1965 Cal 30
Muskegon, MI
What you don't say is how you plan to use this?

*Are you at a dock all week and just want support when out cruising?

*Are you on a mooring and want the fridge to run 24/7?

How you use it is critical because it determines how you design...

I have a customer doing exactly what you want to do but he is a mooring 24/7 guy who wanted to run his Engel... 1 Kyocera 140W panel, with MPPT controller, was not enough when weather went sour... He also has 450Ah's of battery bank as reserve. He often came back to a deficit, not good for the batteries...

I added a second 140W panel and it works perfectly and he has excess to recharge the bank. Remember the 5 hour number is prime conditions and geography determined. It also changes by month and insolation... You can easily have rainy or overcast days/weeks that will result in a 140W panel producing as little as 14 Ah's over an entire day (See Day 1 below). His Engel burns about 30-35 Ah's per day, in Maine. (real world measured/data logged numbers, not marketing)...

I did some data collection / tracking last spring comparing two identical 140W panels, one with MPPT and one with PWM, and allowing the weather to do what it wanted.

The reality was that the PWM controlled 140W panel put out 182 Ah's for an entire 7 day period or an average of 26Ah's per day or 3 hours at full 25C output. The MPPT controller did 220 Ah's or approx 34 Ah's per day or 4 hours at full rated 25C output. Weather is real and needs to be accounted for. These panels can easily do 5+ hours per day but it needs the weather window to do that..

However you would not likely see that type of MPPT gain with a single G-27 battery as it would spend much of its time in absorption when the fridge was not running so MPPT would benefit you little........

The bottom line is when designing a system you design for worst case not the best case, which is what folks tend to do...

Here is the data:


NOTE: The data here can not be easily translated to lead acid because LiFePO4 stays in bulk until about 99.5% SOC with this type of current. MPPT controllers can only "boost" in bulk mode. Unless you had a massive lead acid bank the MPPT gains you see where would be less.
 

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[*]Is it desirable to have whatever mount I use adjustable or is completely flat acceptable?
I rate the ability to aim panels as being a HUGE benefit, and think it's critical on smaller boats like ours, as it allows you to get away with somewhat smaller panels than you might need if they always fixed horizontally... Not to mention, the advantage that smaller and more 'portable' panels can be stowed when not in use, or in heavy weather, etc...

I run into a fair number of East coast snowbirds who turn out to be disappointed in the performance of their panels over the course of a winter in the Bahamas. The primary reason, I believe, is that many tend to underestimate how low the sun - even as far south as the Bahamas - remains in the sky throughout the course of the day in wintertime... They're sacrificing a LOT of potential output, by not having the ability to articulate their panels... If at all possible, make them adjustable, is my recommendation...

I don't have any data, but I'm pretty certain that my daily solar output over the course of a sunny day up in Labrador this summer, probably exceeded that of an equivalent sunny midwinter day in Florida or the Bahamas... And, that's largely chalked up to the ability to articulate my comparatively small panels, and have them making amps from shortly after sunrise, until shortly before sunset...


 

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islander bahama 24
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OK I have a serious question for you after seeing your real world data with a 420 ah flooded lead acid bank and the 2 100 watt panels running a cool blue holding plate system 24/7and approximately 25 watts led lighting for about 3 hrs a day would it pay to spend the additional moneys on the mppt controller or should I spend it on a third 100 watt panel?
 

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Discussion Starter · #13 ·
As I get more into this, it seems like I will need to build a bigger bank with at least another Group 27 or go all the way to a Series/Paralleled bank of 4 T105's or equivalent.

Your comments and research on the charge controllers is fascinating; I hadn't really even thought about which controller I might use and this bears some further study.

How will I use the boat? Well, for the spring and summer, I'll be on shore power when I'm in the slip and the inverter will be off and Engle running from 110. I'll probably make a few weekend trips with whatever setup I have and make some measurements on how feasible it is to run from the second battery bank.

I have a primary house/starting bank of two Group 24's right now that are charged from an on-board charger and get a trickle from the tiny 35A on my Atomic 4. I don't plan on having any connection between this bank and whatever other bank I install as far as use or charging from the engine - but I may consider using one of my 3 legs on my 20A, 36V charger to top off the secondary bank when I'm on shore power.

Next September (God and finances allowing) I'm hoping to embark on the Great Loop and will be living aboard for up to a year. When I drop the mast and head over to Chicago, I'll be in for 1200 miles of motoring and will keep bank 1 topped of with the engine and occasional shore power charging. Using the Engel as either a freezer or refrigerator draws the same 2.75 amps on a (guessing here) 30% duty cycle and with minor use of the inverter as noted previously, think that this combination should do the job.

I really appreciate everyone's inputs. Like many other things in boating, adding solar and making equipment and use plans entails lots of research and decisions. I am grateful for the collective wisdom of the group.

Murph
 

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I would suggest looking at Gemini Marine's mounting system. I will be using their mounts to add 2 more 105w panels on top of my bimini.
Jim
 

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I'll probably make a few weekend trips with whatever setup I have and make some measurements on how feasible it is to run from the second battery bank.
I recommend installing a Xantrex LinkLite or equivalent to monitor charge status and battery condition if you don't have one yet. How else will you know what's going on with your charge status? Once you get everything set up, just unplug from shore power at the dock. See how your system is working. You don't have to anchor out to figure things out.

Ralph
 

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islander bahama 24
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What you don't say is how you plan to use this?

*Are you at a dock all week and just want support when out cruising?

*Are you on a mooring and want the fridge to run 24/7?

How you use it is critical because it determines how you design...

I have a customer doing exactly what you want to do but he is a mooring 24/7 guy who wanted to run his Engel... 1 Kyocera 140W panel, with MPPT controller, was not enough when weather went sour... He also has 450Ah's of battery bank as reserve. He often came back to a deficit, not good for the batteries...

I added a second 140W panel and it works perfectly and he has excess to recharge the bank. Remember the 5 hour number is prime conditions and geography determined. It also changes by month and insolation... You can easily have rainy or overcast days/weeks that will result in a 140W panel producing as little as 14 Ah's over an entire day (See Day 1 below). His Engel burns about 30-35 Ah's per day, in Maine. (real world measured/data logged numbers, not marketing)...

I did some data collection / tracking last spring comparing two identical 140W panels, one with MPPT and one with PWM, and allowing the weather to do what it wanted.

The reality was that the PWM controlled 140W panel put out 182 Ah's for an entire 7 day period or an average of 26Ah's per day or 3 hours at full 25C output. The MPPT controller did 220 Ah's or approx 34 Ah's per day or 4 hours at full rated 25C output. Weather is real and needs to be accounted for. These panels can easily do 5+ hours per day but it needs the weather window to do that..

However you would not likely see that type of MPPT gain with a single G-27 battery as it would spend much of its time in absorption when the fridge was not running so MPPT would benefit you little........

The bottom line is when designing a system you design for worst case not the best case, which is what folks tend to do...

Here is the data:


NOTE: The data here can not be easily translated to lead acid because LiFePO4 stays in bulk until about 99.5% SOC with this type of current. MPPT controllers can only "boost" in bulk mode. Unless you had a massive lead acid bank the MPPT gains you see where would be less.
I have a question what do you mean by a massive lead acid bank mine is just over 400 ah and honestly don't expect to use more than 50 or 60 ah per day with 200 watts solar is it worth the expense of a mppt controller the pwm comes with the panels
 

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As I get more into this, it seems like I will need to build a bigger bank with at least another Group 27 or go all the way to a Series/Paralleled bank of 4 T105's or equivalent.

Your comments and research on the charge controllers is fascinating; I hadn't really even thought about which controller I might use and this bears some further study.

How will I use the boat? Well, for the spring and summer, I'll be on shore power when I'm in the slip and the inverter will be off and Engle running from 110. I'll probably make a few weekend trips with whatever setup I have and make some measurements on how feasible it is to run from the second battery bank.

I have a primary house/starting bank of two Group 24's right now that are charged from an on-board charger and get a trickle from the tiny 35A on my Atomic 4. I don't plan on having any connection between this bank and whatever other bank I install as far as use or charging from the engine - but I may consider using one of my 3 legs on my 20A, 36V charger to top off the secondary bank when I'm on shore power.

Next September (God and finances allowing) I'm hoping to embark on the Great Loop and will be living aboard for up to a year. When I drop the mast and head over to Chicago, I'll be in for 1200 miles of motoring and will keep bank 1 topped of with the engine and occasional shore power charging. Using the Engel as either a freezer or refrigerator draws the same 2.75 amps on a (guessing here) 30% duty cycle and with minor use of the inverter as noted previously, think that this combination should do the job.

I really appreciate everyone's inputs. Like many other things in boating, adding solar and making equipment and use plans entails lots of research and decisions. I am grateful for the collective wisdom of the group.

Murph
One thing I seem to see more and more are people who are at a slip and use solar to charge batteries and keep refrigerator cold so they don't have to plug into the normally pretty dirty power of a marina. Gives a nice flexibility as to where to get a slip too if you don't need power. If you are building a system make it as flexible and give you the most self sufficient system you can.
 

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one of my 3 legs on my 20A, 36V charger to top off the secondary bank when I'm on shore power.

Using the Engel as either a freezer or refrigerator draws the same 2.75 amps
For a 40 quart Engel the specs are .7 amps as a fridge and 2.5 amps as a freezer. In other words about 17 AH/24 hours as a fridge and 60 AH/24 hours as a freezer in 77F ambient temps.

36 volt charger?
 

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You cannot charge 12 volt batteries with that charger.

I'm guessing he has a 3 output 12 volt charger not a 36 volt charger which would not work.
 
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