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Old 07-04-2012, 11:53   #1
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Am I Expecting too much from my Solar Panels

Hi
Can anyone tell me if my solar charging system is performing as it should, or how I may improve it if it is not?
I have 6X200Ah AGMs and 6X135W PV panels running through 2 Mastervolt Chargemaster SMC-N-40 regulators
I am currently in Les Sables D Olonne France where the installation was carried out in November, before I the left for the winter.
On returning I have tested it over a few days and the peak Amp charge on sunny days (no cloud) was in the low 30s.
With an average load of about 10Amps the battery bank is slowly coming down.
Am I expecting too much or should I be thinking wind generator?
Any advice appreciated
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Old 07-04-2012, 12:32   #2
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Re: Am I expecting too much from my solar panels

have you tested the output of your panels and made sure the connections are good?? have you made sure the incoming charge is greatr than your use??
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Old 07-04-2012, 12:49   #3
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Re: Am I expecting too much from my solar panels

Your average load of 10 amps seems high. What are you running that draws so much current?

A peak of 30-33 amps seems a little low for your setup. I am not familiar with the Mastercharge controller but I do not think it is an MPPT type controller. If you switch to a good quality MPPT that should increase the charge to your batteries.

Four panels should be enough to keep most boat battery systems charged with good sunlight. I think with a better controller and a little conservation in your use the panels should be sufficient.
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Old 07-04-2012, 12:53   #4
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Re: Am I expecting too much from my solar panels

First check you cabling, that it is not causing voltage drops from inadequate size or bad contacts. A lot of DC wiring is spec'd for a 3% voltage drop but in a nominal 12-volt system that is a significant power loss in between the charging source and the battery.

Then if your "regulators" are just that, you can gain some 10-20% more power by switching to an MPPT controller.

6x135W panels would be 810 watts under the best conditions, or some 3200 watt hours in a typical days. That might translate into 230 amps (at 13.8 volts) into the battery bank on a good day. If you draw more than that, you have a problem. If you draw less than that but the system is not providing it, you have a different problem.

If your system is set up for "12" volts, it would provide some 56 amps in full sunlight. If it is set up for 24 volts, then 30 amps is indeed excellent output.

Bear in mind, these are ballpark numbers and a 10-20% variation would not be unheard of.

And then of course, you'd need to load test your batteries to see if they are part of the problem. If you are putting 30A into the batteries while drawing 10A out and the batteries are still losing charge--then yes, the batteries are probably due for replacement.
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Old 07-04-2012, 13:12   #5
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Re: Am I expecting too much from my solar panels

A max of low 30A from 810w of solar in France at this time of year is poor. Are there shadows on panels when you are getting this maximum? In some installations there are always shaddows on some panels. As the boat, or sun, swings the panels in shade change so all panels contribute at different times, but the maximum output is limited.
If there are not any great shadowing problems you need to start troubleshooting. The sort of output you are getting suggests that some panels are are not contributing. The most common problem is poor connections. A clamp on multimeter willl make diagnosing the problem much easier.
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Old 07-04-2012, 13:27   #6
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Re: Am I expecting too much from my solar panels

Your solar panels probably produce their maximum power at about 17 V. So 6*135/17 = 48 amps. So if you measured in the low 30s with the sun absolutely vertical (and I doubt that it was in early April in France) then your panels aren't performing up to spec. FWIW I talked to a friend in central Florida (a lower lattitude and therefore the sun is more vertical now) who I helped intall his panels. He was getting about 65% of rated amperage during mid day, about what you are seeing. So I suspect that your panels are performing up to spec.

I looked at MasterVolt's spec on this controller and didn't see the magic acronym MPPT, so I don't think that is what you have. All that means is that you cannot convert the 17 volts to a 13 V charging voltage and increase the amps accordingly which is what a MPPT controller does. You will never get more than about 48 amps into your batteries.

So I would look at: installing a MPPT controller which would increase charging about 15%, tilting your panels so that they are truly perpendicular to the sun (not likely possible), install more panels, or try to reduce your consumption. 240 amphours per day is very high for a typical cruiser. 100-150 would be more typical.

David
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Old 07-04-2012, 14:05   #7
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Re: Am I expecting too much from my solar panels

I would expect roughly 45A (@ nom 12V) from these panels into any system that can take full output. If you are getting less, then maybe:

- the panels are not aligned 90 degs to the sun (you are in les Sables but the Sun is somewhere over the Equator),

- your batteries are not 'discharged enough',

- the panels are not clean (dust) or they are partly shaded (masts, shroud shadows, etc),

- there is haze (commercial, natural, etc.)

- you charging system elements are not up to the job - switches, cables, chargers, etc.)

- other factors, or a combination of factors.

I found that pretty often it is either the wrong angle or else a shade from anything that brings the panels' output down.

My 2 eurocents.

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Old 07-04-2012, 20:18   #8
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Re: Am I expecting too much from my solar panels

"A max of low 30A from 810w of solar in France at this time of year is poor."
Gentlemen.
France! 24v could be the norm, not our US-centric 12V. Until we know that, we don't know if 30A is indeed low, or perfectly adequate for a 24V system.

Double the voltage, half the amperage, wattage all the same.

And we give thanks to the USN for requiring "all vehicles to be purchased by the USN" to have 12 volt systems, that's literally the only reason we have any voltage standard in US vehicles and vessels.
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Old 08-04-2012, 01:00   #9
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Re: Am I expecting too much from my solar panels

Thanks to all who have replied and given advice. I will analyze it and it gives me something to talk to the installer.
Just to answer some of the questions.
The 12V batteries new last year
Solar panels 12V
They are clean
Sloping towards the sun (cabin top of catamaran. Not perpendicular)
No shadows when readings taken over 3 days, sun at its best.
I ran batteries down to 65% one day but it didn't change the charge rate.
The cable size I am not sure of but will ask the question.
MPPT regulator sounds like I should have been offered the option.
The company here does a lot of work on Lagoons and I would have thought they were up to date.
If anyone has more to add all advice appreciated.
I hope this is the correct way to reply, as this is the first time I have posted but it probably will not be the last.
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Old 08-04-2012, 06:06   #10
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Re: Am I expecting too much from my solar panels

Quote:
Originally Posted by bluemana View Post

(...)

Sloping towards the sun (cabin top of catamaran. Not perpendicular)

(...)
So I assume you have fixed panels? Look at this graph, it explains the idea of the energy lost due to panel being fixed rather than angled.

http://www.limpkin.fr/public/Solar_p...rientation.png

Cheers,
b.
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Old 08-04-2012, 12:03   #11
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Re: Am I expecting too much from my solar panels

There is definatly something wrong. MPPT will only improve things a very small amount ( 10% or so) . The first thing to do is find the problem. It's unlikely to be wire size, because unless very small gauges have been selected your output is too low for it to wire loss alone. There is likely to be bad conection somewhere.
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Old 08-04-2012, 12:10   #12
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Re: Am I expecting too much from my solar panels

Quote:
Originally Posted by hellosailor View Post
"A max of low 30A from 810w of solar in France at this time of year is poor."
Gentlemen.
France! 24v could be the norm, not our US-centric 12V. Until we know that, we don't know if 30A is indeed low, or perfectly adequate for a 24V system.
12v is the norm all over the world. It is not like AC where the USA runs half the voltage of most of the rest of the world.
There are a few 24v yachts, from all countries, mainly 50 feet and over.
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Old 08-04-2012, 12:11   #13
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Re: Am I expecting too much from my solar panels

"The 12V batteries new last year
Solar panels 12V"

Then there is indeed something wrong. Even if the panels are not directly facing the sun, the loss is only something like 10% for every 15 degress ("one hour" of rotation) that they are off, which would leave the two hours around noon providing way more power.

If there is no ventilation airflow under the panels, they'll lose some performance from heat, but still, not 50%.

Your installer should be able to come out to the boat, check the system, and SHOW YOU that the 800+ watts of panels, are putting out something close to that power at noontime. Something, perhaps very subtle, is wrong.
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Old 08-04-2012, 21:19   #14
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Re: Am I expecting too much from my solar panels

Check this blog out. It's an RV boondocker guy that does not own a generator and runs his whole RV off 345w of solar. Great lil read.

1. The RV Battery Charging Puzzle HandyBob's Blog
2. The History, or how did I end up so angry? HandyBob's Blog
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Old 11-04-2012, 04:21   #15
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Re: Am I expecting too much from my solar panels

I am in Greece , without looking up insolation values I would expect they are simililar to you in france. Today is my first day back in the water after antifouling and I thought you may be interested that with less than half your solar power (330w) I got a peak output of 24.8A. This was well before solar noonso the output would go higher, but the batteries are regulating now
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