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Old 03-09-2018, 01:10   #1
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A basic Solar Question

I have been reading with interest the threads on solar panel installation and recognise that there is a wealth of information in this community. Perhaps you guys might suggest a simple solution to my question. Ideas appreciated.
I currently have two 80 watt panels mounted on a frame over the stern of my 33 foot yacht. Each one is angled at about 40 degrees to the horizontal, sloping outboard, one port, one stbd. They are paralleled to a Steca PR1515 controller. For many hours only one would be getting full sun and I generally see 4.5 to 5 amps coming into the controller. That seems to keep the AGM battery bank at 99% to 100% at the mooring.
I would like to put a 200 watt flexible on top of the bimini to improve solar catch and we all know that efficiency will never be such that I get 200W/12V current from it. Nevertheless it would feasibly exceed the 15A in total.
I am considering either a quick solution and put a controller on that panel and direct to the busbar, so there are two solar feeds to the busbar, or replace the Steca with a 30A MPPT. If I do the latter should I put diodes in the circuits to stop back current and reduced efficiency if one panel is in shade, since all panels would then be wired in parallel?
What are your thoughts?
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Old 03-09-2018, 01:44   #2
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Re: A basic Solar Question

Oops! I just thought of a supplementary question (as the politicians say). Do most people run their ships power (lights, electronics, fridge etc) from the load output on the controller or straight off the busbar? Mine go off the busbar at the moment, which means I have no way to note amp hour consumption.
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Old 03-09-2018, 18:28   #3
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Re: A basic Solar Question

if your panels are facing different ways it is best to have a controller for each panel. idealy you would have 3 controllers.

I would not use the load output.
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Old 03-09-2018, 22:02   #4
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Re: A basic Solar Question

An AH counting meter will let you log energy usage and / or charging inputs

at whatever point you like by moving the shunt.
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Old 04-09-2018, 12:14   #5
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Re: A basic Solar Question

Yep, you just got the two answers that I was considering posting whilst I was reading your comments . . . enough done and said . . . well done, gentlemen. . . .
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Old 04-09-2018, 15:58   #6
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Re: A basic Solar Question

Thanks for the responses guys. I think I have it figured now from what you have written and following a few old threads on this forum.
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Old 05-09-2018, 05:56   #7
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Re: A basic Solar Question

Quote:
Originally Posted by Dranflydbl View Post
I have been reading with interest the threads on solar panel installation and recognise that there is a wealth of information in this community. Perhaps you guys might suggest a simple solution to my question. Ideas appreciated.
I currently have two 80 watt panels mounted on a frame over the stern of my 33 foot yacht. Each one is angled at about 40 degrees to the horizontal, sloping outboard, one port, one stbd. They are paralleled to a Steca PR1515 controller. For many hours only one would be getting full sun and I generally see 4.5 to 5 amps coming into the controller. That seems to keep the AGM battery bank at 99% to 100% at the mooring.
I would like to put a 200 watt flexible on top of the bimini to improve solar catch and we all know that efficiency will never be such that I get 200W/12V current from it. Nevertheless it would feasibly exceed the 15A in total.
I am considering either a quick solution and put a controller on that panel and direct to the busbar, so there are two solar feeds to the busbar, or replace the Steca with a 30A MPPT. If I do the latter should I put diodes in the circuits to stop back current and reduced efficiency if one panel is in shade, since all panels would then be wired in parallel?
What are your thoughts?
An energy needs analysis should always be performed, but for your size cruising sailboat, I find the average daily energy consumption to be around 100 A-hrs, assuming a single BD-35 fridge compressor, Autohelm, and normal complement of nav instruments.

In this case, I recommend a balanced electrical system consisting of 300 A-hr FLA house battery capacity, and 80A automotive alternator, 400 W of combined solar, and/or wind.

The best place for the solar is typically on the back, aft of the boom, to have the least shading issues. On a dodger or bimini, with 2 panels mounted fore / aft side by side, one or the other will always be in the shade and outputing zip.

In response to your particular set up and questions.

You would likely do better if your panels were mounted flat rather than fixed angled. You will typically see 8-10 A peak and around 40 A-hrs total on a typical sunny day.



You will need to run your alternator (80A assumed) for about 1 hour in the morning for a sunny day, or 2 hours if the day will be cloudy.

If you bump your solar up to 400W you will not need ICE charging about 5 days out of 7, solar will take care of it all.

If you do put 200W of solar on the bimini, split it between to panels oriented fore/aft, connect them in parallel, and to a separate solar charge controller.

No diodes should be required if all panels are connected in parallel to their respective controllers.
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Old 05-09-2018, 10:11   #8
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Re: A basic Solar Question

My understanding is the output from the controllers should go straight to the battery. I have set up my system that way.

Load comes off the battery to a main switch then the fuse/switch panel on the positive side and straight from battery to buss on negative side.

Inverter and electric harbor motor skip the fuse panel but have appropriately sized circuit breakers.
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Old 05-09-2018, 12:01   #9
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Re: A basic Solar Question

Quote:
Originally Posted by Dranflydbl View Post
I have been reading with interest the threads on solar panel installation and recognise that there is a wealth of information in this community. Perhaps you guys might suggest a simple solution to my question. Ideas appreciated.
I currently have two 80 watt panels mounted on a frame over the stern of my 33 foot yacht. Each one is angled at about 40 degrees to the horizontal, sloping outboard, one port, one stbd. They are paralleled to a Steca PR1515 controller. For many hours only one would be getting full sun and I generally see 4.5 to 5 amps coming into the controller. That seems to keep the AGM battery bank at 99% to 100% at the mooring.
I would like to put a 200 watt flexible on top of the bimini to improve solar catch and we all know that efficiency will never be such that I get 200W/12V current from it. Nevertheless it would feasibly exceed the 15A in total.
I am considering either a quick solution and put a controller on that panel and direct to the busbar, so there are two solar feeds to the busbar, or replace the Steca with a 30A MPPT. If I do the latter should I put diodes in the circuits to stop back current and reduced efficiency if one panel is in shade, since all panels would then be wired in parallel?
What are your thoughts?
I would recommend adding a separate controller for the new panel on the bimini.
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Old 05-09-2018, 12:03   #10
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Re: A basic Solar Question

Quote:
Originally Posted by ramblinrod View Post
An energy needs analysis should always be performed, but for your size cruising sailboat, I find the average daily energy consumption to be around 100 A-hrs, assuming a single BD-35 fridge compressor, Autohelm, and normal complement of nav instruments.

In this case, I recommend a balanced electrical system consisting of 300 A-hr FLA house battery capacity, and 80A automotive alternator, 400 W of combined solar, and/or wind.

The best place for the solar is typically on the back, aft of the boom, to have the least shading issues. On a dodger or bimini, with 2 panels mounted fore / aft side by side, one or the other will always be in the shade and outputing zip.

In response to your particular set up and questions.

You would likely do better if your panels were mounted flat rather than fixed angled. You will typically see 8-10 A peak and around 40 A-hrs total on a typical sunny day.



You will need to run your alternator (80A assumed) for about 1 hour in the morning for a sunny day, or 2 hours if the day will be cloudy.

If you bump your solar up to 400W you will not need ICE charging about 5 days out of 7, solar will take care of it all.

If you do put 200W of solar on the bimini, split it between to panels oriented fore/aft, connect them in parallel, and to a separate solar charge controller.

No diodes should be required if all panels are connected in parallel to their respective controllers.
why the infomercial before any addressing of his actual question.
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Old 05-09-2018, 14:30   #11
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Re: A basic Solar Question

@newhaul
Can you explain what he means by "oriented fore/aft"?

Quote:
If you do put 200W of solar on the bimini, split it between to panels oriented fore/aft, connect them in parallel, and to a separate solar charge controller.

PS: My understanding is that separate PV panels on port/starboard sides of the bimini should be connected to separate solar controllers for optimal charging.
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Old 05-09-2018, 14:40   #12
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Re: A basic Solar Question

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@newhaul
Can you explain what he means by "oriented fore/aft"?




PS: My understanding is that separate PV panels on port/starboard sides of the bimini should be connected to separate solar controllers for optimal charging.
for all panels there is a junction box on one end so that we will call the top and the oposite the bottom. so orient top and bottom with the bow and stern .
panels on either side of centerline dont need to be on seperate controllers . just best not to connect them in series .
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Old 05-09-2018, 20:37   #13
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Re: A basic Solar Question

Quote:
for all panels there is a junction box on one end so that we will call the top and the oposite the bottom. so orient top and bottom with the bow and stern .
Thanks. Can you explain to my why? Is it something to do with the PV cells or the way the wiring works or sun strikes the cell or what?

Quote:
panels on either side of centerline dont need to be on seperate controllers . just best not to connect them in series
Ok, what is your actual experience with panels in parallel when one panel is in shade? How does the amp output of the controller change when both panels are in full light vs, when one is in partial/full shade?

I understand that separate controllers are best and result in more output, but I don't know why and have not measured it yet.
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Old 05-09-2018, 20:47   #14
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Re: A basic Solar Question

Victron line two smaller SCs can be cheaper than one big one.

The difference varies tremendously depending on a dozen factors.

Sometimes not much at all for parallel.

Lors for serial.
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Old 05-09-2018, 20:52   #15
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Re: A basic Solar Question

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Originally Posted by rgleason View Post
Thanks. Can you explain to my why? Is it something to do with the PV cells or the way the wiring works or sun strikes the cell or what?

Ok, what is your actual experience with panels in parallel when one panel is in shade? How does the amp output of the controller change when both panels are in full light vs, when one is in partial/full shade?

I understand that separate controllers are best and result in more output, but I don't know why and have not measured it yet.
orentated fore and aft to minimize the likelyhood of shading. by the boom.
on parallel hooked up panels it really doesnt make a difference
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