Series or Parallel Panels?

[dmkkeng]

Originally Posted by flightlead404

I'm struggling a little with my solar design. I'm planning on installing THREE of these 210W panels on my Hunter 38.

The panels will be over the rear half of the bimini top and extending a little over the davits, aligned longitudinally behind the end of the boom.

I'm struggling with how to wire, series or parallel. I'm concerned about two things; first, if in series, partial shading of one panel taking the whole string down, second, if in parallel, the gauge of the wire from the branch connectors to the MPPT controller (guess, 30 ft).

Thoughts? Comments? Suggestions?

I have a Catalina 42 sailboat with four 100W panels located on top of the Bimini, when you are sailing the position of the sun and the tack you are on can greatly affect the performance of the solar panels. For that reason my panels are connected in a serial/ parallel configuration. The two panels on the port side and the two panels on the starboard side are connected in series, the port side panel array and starboard side panel array are connected in parallel. The wiring from the solar panels is fed into a breaker box located aft, the output of the breaker box is fed to a single controller that is capable of handling both the max voltage and current produced by the solar panels, same goes for the wiring. From a redundancy point of view I wish I had installed a separate controller for the port and starboard array. Check the specifications on the panels that you have, when panels are in series you add the max voltage, current remains the same, when panels are in parallel you add the max current, voltage stays the same. Next you need to check the specification of the controller to ensure it can handle the max voltage and current produced by the solar panels, the same goes for the wiring. Hope that helps.

[dmkkeng]

Originally Posted by flightlead404

Reading some of the published articles I find on the 'net some of them give what appears to be contradictory reasoning for their choices. One article mentions wiring in series because of the shading issue, but series raised the panel voltage above battery voltage and minimized the issue. Another mentions running in parallel but using a brach connector to join all the grounds, but running separate leads for the positives, which sounds like the ground side is then too small of a gauge.

To be "best" it seems like I would need to run all three pairs of leads separately all the way to the controller, OR, probably use 6 AWG from two branch connectors close to the panels.

Yes there is definitely contradictory information - my understanding is that if you are worried about shading install the panels in a a parallel configuration, the draw back of this configuration is it increases the max current and the size of the wiring required. Perhaps in your scenario it is worth considering multiple smaller controllers rather than one big controller?

[dmkkeng]

Originally Posted by flightlead404

I'm considering going in parallel with three separate PWM controllers. That solves the shading issue and the charge start point issue, and keeps the controller cost lower.

I just need to check if there's space for the wiring. Back on the boat tomorrow.

Read up on the technology of PWM versus MPPT controller, the MPPT controllers are more efficient, they are more expensive however the cost difference is justified.

[thomm225]

That's like 6 of 1; a half dozen of the other.

If you have a battery bank more than capable of handling the load on your boat, you should be fine either way......and that includes the controllers as well.

[pwillems]

I did my own pseudo scientific testing between parallel and series before deciding for my own installation. 2 sets of new panels side by side at the same time and in a range of insolation conditions with identical controllers charging the same depleted battery.

In cases with unavoidable shading such as a sailboat, parallel is the way to go. Anyone who tells you differently has not done the testing and is just repeating what they read somewhere.

Even better however is a controller per panel.

[Moontide]

EDIT - I think his post was corrrected after i read it. I agree with the parrallel over series that it now says.



pwillems That is certainly much different than my own experiment. when I installed solar on my boat. Also the opposite of what others have seen and documented on Youtube videos they put up.



Are you sure you didn't reverse the two? If not would be interested on seeing the detailed results.



And your statement about others only repeating what they have read is way off base, and pretty absurd to even say. Making those kinds of accusations does nothing to contribute to the knowledge base. Post your actual results if you want to educate people.

[pwillems]

Originally Posted by Moontide

EDIT - I think his post was corrrected after i read it. I agree with the parrallel over series that it now says.



pwillems That is certainly much different than my own experiment. when I installed solar on my boat. Also the opposite of what others have seen and documented on Youtube videos they put up.



Are you sure you didn't reverse the two? If not would be interested on seeing the detailed results.



And your statement about others only repeating what they have read is way off base, and pretty absurd to even say. Making those kinds of accusations does nothing to contribute to the knowledge base. Post your actual results if you want to educate people.

Spot on, morning coffee had not kicked in yet, I initially typed series and edited to parallel.

My tests 100% confirmed parallel over series if there is any chance of shade at all.

Case closed as far as I am concerned, I ignored the forums and did my own testing which was conclusive. But internet debates will go on forever and I am no longer interested. My setup is optimal based on my own tests.

[Gerrit Coetzee]

Originally Posted by flightlead404

I'm struggling a little with my solar design. I'm planning on installing THREE of these 210W panels on my Hunter 38.

The panels will be over the rear half of the bimini top and extending a little over the davits, aligned longitudinally behind the end of the boom.

I'm struggling with how to wire, series or parallel. I'm concerned about two things; first, if in series, partial shading of one panel taking the whole string down, second, if in parallel, the gauge of the wire from the branch connectors to the MPPT controller (guess, 30 ft).

Thoughts? Comments? Suggestions?

Maybe addressed already.
Parallel or series not the only consideration.

Maybe not an issue yet, but 3x210w might bring you in range of another problem- MPPT and inverter minimum and maximums, the latter being the greater problem.

See what is both the Volts and the Amp maximum of the receiving parts.

After pushing 320V through my inverter with built in MMPT, I had to take it out and send it in, hopefully where it can be repaired. The maximum input take-up Voltage was 150V.

- And the installation was done by TWO certified electricians !!!-

Series or Parallel, note the limits.

(Now I have 3x2 in Series then Paralleled arrays)

[SOLAR SUPPORT]

This guy explain the advantages on different environmental conditions related with solar power production. This video is very informative..

Charge controller comparison video link:
https://youtu.be/kF_cVEYxj3E

I have 4 x 80 Wp monocristal panels connected in parallel which work with the PWM 30A charge regulator. 320 Wp system is 14 years old now and work great. Max output observed in may 21 Amps Average daily max output is 16~17 Amps @12volt in Hot summer times. Considering to upgrade to MPPT to improve the power output. 100 Wp test video show there are only 4 watts difference between the MPPT and PWM. Does it worth to shift MPPT?

[nilespf]

Originally Posted
I'm struggling a little with my solar design. I'm planning on installing THREE of these 210W panels on my Hunter 38.

The panels will be over the rear half of the bimini top and extending a little over the davits, aligned longitudinally behind the end of the boom.

I'm struggling with how to wire, series or parallel. I'm concerned about two things; first, if in series, partial shading of one panel taking the whole string down, second, if in parallel, the gauge of the wire from the branch connectors to the MPPT controller (guess, 30 ft).

Thoughts? Comments? Suggestions


Wire your panels in a manner that gives you the most voltage when in a shaded condition. Your panels look to be 60 cells and because the amount of bypass diodes installed by the factory will directly influence the output voltage of the panel then (as you know) how you wire the panels to each other influences the MPPT controller operation. Digressing for a moment, what we have to work with are the Buck variety MPPT's meaning they need to be able to step down the voltage received from the panels. If your panels have 2 diodes that bypass a linear string of 30 cells consider this example on a single panel. If you shade one cell and trigger a bypass condition (in that string of 30 cells only) the panel output drops to 8.5 volts. For the purist among us other effects influence the new output voltage but among friends.... Now if you wire up the shaded panel in series with another non shaded working panel then you have 25+ volts to work with and the MPPT is happy. Take the same shaded panel and wire it in parallel with another non shaded working panel and your output voltage will be marginal. Both configurations will supply 319W but one is considerably more sensitive to outside design conditions i.e. wire gage length of run battery SOC etc.

Post some info on your MPPT and how many diodes you have per panel.
Hope this helps.

[flightlead404]

I'm going to be wiring the panels in series, due to the position of the panels the shading will be minimal and manageable. I plan on using this cable.

So, with the 3 x 210W panels the using Vmp the input voltage to the controller will be 3 x 16.77 V or 50.31 V. The current at Imp is 12.48 A.

I was thinking of using this MPPT controller which has 150V max input.

The only thing that gives me pause is that it says in the descriptive text "This 20 amp MPPT Solar Panel Charger works with 260W Solar Panel on 12V Battery System".

Is that input amperage, or output? Do I need to spend the extra $60 to get its larger brother?

[smac999]

Buy 3 controllers.

[smac999]

Originally Posted by flightlead404

I'm going to be wiring the panels in series, due to the position of the panels the shading will be minimal and manageable. I plan on using this cable.

So, with the 3 x 210W panels the using Vmp the input voltage to the controller will be 3 x 16.77 V or 50.31 V. The current at Imp is 12.48 A.

I was thinking of using this MPPT controller which has 150V max input.

The only thing that gives me pause is that it says in the descriptive text "This 20 amp MPPT Solar Panel Charger works with 260W Solar Panel on 12V Battery System".

Is that input amperage, or output? Do I need to spend the extra $60 to get its larger brother?

You cannt Run 630w of Panels into a 20a controller. The amp rating is the output. You’ll be at ~50a if 12v batteries. You need a 50 or 60a controller. 30a if 24v bank.

[flightlead404]

Originally Posted by smac999

You cannt Run 630w of Panels into a 20a controller. The amp rating is the output. You’ll be at ~50a if 12v batteries. You need a 50 or 60a controller. 30a if 24v bank.

So it is the output, I thought it might be. Tks.

So this one seems to fit the bill then.

[nilespf]

Actually its the power. Buck converters can have any number of combinations of output as long as the total power being delivered to the load is not exceeded. Since the load is a battery, SOC will greatly effect what appears to be your performance. Example, if the battery is in need of charge, the controller can supply 20A max and by definition that is within the total power the controller can handle. Testing on a charged battery is border line useless in that there will be only a trickle of current flowing. You can use the M50 to program the output of the float high enough ( I also have M50's to program) to force feed the batteries. If the SOC is low, they will accept everything the system can offer. Use your battery monitor to characterize all your loads and you will be able to load the controller to virtually any power level you desire.