Solar panels mounted on arch - series or parallel

[collinsp]

Hi Guys,

I'm about to upgraded the old/useless panels currently mounted on my solar arch. I'm thinking about 2 Renology 175W panels with a Victron MPPT 100/50 connected to 2 Renology 200Ah Lithium batteries. I work from the boat several days a week using a laptop and screen either in the Marina or over the summer months at anchor and usually am also running the fridge as well. I wanted to get thoughts on wiring the panels in series or parallel. I have read that with healing, not much pf a problem in Marinas or at anchor but sowetimes have to have the laptop and screen running on passages, that it would be better to have them in parallel but most of what I have read is for people mounting on the sides not on an arch. I wondered if anyone had experience with drop in output when healed over on passages. My thoughts were that unless you were healing over >25 degrees it should not make that much difference to the output but that is purely a guess

Any thoughts/input would be greatly appreciated.

Paul

 

[pmagowan]

My understanding (through research rather than experience) is that optimal is an mppt for each panel. Otherwise there are lots of threads here and other places re pros and cons depending on likely shading etc.
Look at genasun boost mppt

 

[noelex]

My understanding (through research rather than experience) is that optimal is an mppt for each panel. Otherwise there are lots of threads here and other places re pros and cons depending on likely shading etc.
Look at genasun boost mppt

Yes, one solar controller per panel generally delivers the maximum solar energy yield on a yacht. Unfortunately, it is also usually the most expensive and difficult to install, although sometime two smaller controllers will be a similar price or even occasionally cheaper than one larger unit.

The next best option is parallel connection.

Serial connection is the cheapest and easiest to install, but the total energy harvest is less, especially with panels subject to shade or disparate conditions.

 

[sailoppopotamus]

I think that two Victron SmartSolar 75/15 controllers work out significantly cheaper than a single 100/50, and will likely perform better than a single 100/50. The latter however is more future proof, in the sense that you can add more panels without needing to upgrade the controller (assuming you can even fit more panels on your boat). Having recently installed a SmartSolar controller I feel the Bluetooth functionality is definitely worth the premium in price over the non-Bluetooth enabled BlueSolar and I'm very glad I didn't go for BlueSolar as I originally intended.

 

[PaulRainbow]

Hi Guys,

I'm about to upgraded the old/useless panels currently mounted on my solar arch. I'm thinking about 2 Renology 175W panels with a Victron MPPT 100/50 connected to 2 Renology 200Ah Lithium batteries. I work from the boat several days a week using a laptop and screen either in the Marina or over the summer months at anchor and usually am also running the fridge as well. I wanted to get thoughts on wiring the panels in series or parallel. I have read that with healing, not much pf a problem in Marinas or at anchor but sowetimes have to have the laptop and screen running on passages, that it would be better to have them in parallel but most of what I have read is for people mounting on the sides not on an arch. I wondered if anyone had experience with drop in output when healed over on passages. My thoughts were that unless you were healing over >25 degrees it should not make that much difference to the output but that is purely a guess

Any thoughts/input would be greatly appreciated.

Paul

If the panels won't suffer from shading, connect them in series. Any shading, connect in parallel.

 

[Refueler]

I am genuinely interested in this and maybe someone can expand on it.

I have one panel so far - yes small I know - but it gives out over 18v .... the controller I have states up to about 41v .. anyway around that.
I am waiting to receive a second panel same size etc and intention to parallel, so that voltage stays at the 18v - well below controller max ... but wattage increased.

Just reading posts - I'm wondering why shade would be a factor to say parallel ... I would have thought the matter would need series to get the voltage up to make sure controller is triggered to work ?

 

[noelex]

Just reading posts - I'm wondering why shade would be a factor to say parallel ... I would have thought the matter would need series to get the voltage up to make sure controller is triggered to work ?

If you have a MPPT controller it will adjust the input voltage to the value that produces the maximum power.

If you have two identical panels in identical situations this voltage will be identical for both panels

However, if one panel is subject to different conditions, such as shade, the voltage which produces the most power will be different between the two panels. When connected in parallel there can only be one input voltage. The controller will be forced to select a compromise voltage.

With one controller per panel the input voltages can adjusted to maximise the input voltage of just the connected panel. Thus different panels can have different input voltages to optimise their output.

The difference is not great, but multiple controllers provides the highest yield providing the Vmp remains above the battery voltage. Multiple controllers also add useful redundancy.

 

[Daverw]

I tried both serial and parallel for my two panels fitted two years ago, they do have some shading at times due to back stay, I did not really think it would make that much difference. in Jan fitted second mppt controller so one each and the effect on increased output is significant, nearly double over a week, I now have the radar done on the arch between both and even this although makes a difference it’s small.

 

[Refueler]

If you have a MPPT controller it will adjust the input voltage to the value that produces the maximum power.

If you have two identical panels in identical situations this voltage will be identical for both panels

However, if one panel is subject to different conditions, such as shade, the voltage which produces the most power will be different between the two panels. When connected in parallel there can only be one input voltage. The controller will be forced to select a compromise voltage.

With one controller per panel the input voltages can adjusted to maximise the input voltage of just the connected panel. Thus different panels can have different input voltages to optimise their output.

The difference is not great, but multiple controllers provides the highest yield providing the Vmp remains above the battery voltage. Multiple controllers also add useful redundancy.

I can see the separate controller point ... thats not my question ...

I was referring to Series vs Parallel feeding one controller.

For so long I have laboured with Watts ...

 

[noelex]

I was referring to Series vs Parallel feeding one controller.

In very simple terms, the problem with series connection is that the current from all connected solar panels must be equal. Solar panels with any shade produce much less current than panels in full sun, as anyone with solar panels will attest Thus one panel in shade can potentially limit the maximum current of the other connected panels that may be in full sun. Bypass diodes can mitigate this somewhat, but not in all situations.

However, this is a very simplified view. The difference in performance between series and parallel is complex to model theoretically. There are times when depending on how the shadows fall, one or the other connection can be superior.

The best method of determining which connection system produces the highest yield is experimental. Sailors after trying both connection options overwhelmingly report parallel connection is superior on a yacht.

There are some caveats. The panel Vmp has to be above the battery voltage and also enough to meet the start up requirements of the controller.

Series connection is the easiest and cheapest to implement, requiring thinner wire than parallel connection so it worth considering even if the output will be lower. Also note that series connection is only normally possible with MPPT controllers.

 

[collinsp]

Thanks for all the useful input, really enjoyed reading the thoughts and experience of people. I think I will go with 2 MPPT controllers which actually work out cheaper than the 100/50 option, then i get the max from each panel and also have redundancy. Appreciate there is little room to add another panel without another controller but I have no more room on the arch anyway

 

[Baggywrinkle]

Did an experiment in the Adriatic with my 3 x 100W panels and a Victron SmartSolar MPPT (100-30) .... had a week with them connected in parallel, and a week with them connected in series - they were mounted on the bimini as shown here .... 2,5mm2 on each panel and 6mm2 from the MC4 connectors on the bimini to the MPPT (about 4-5 m)



.... I saw no discernable difference in the daily yield so I connected them in series due to the simplicity of the wiring.

Various explanations could be the reason ...

The bypass diodes in the panels were minimising the effect of shading?, the combined voltages of 3 panels was getting the MPPT over its startup voltage earlier, and it was staying on longer in the evening? - but at the end of the day, I saw no measurable advantage to parallel connection. Weather was mostly clear skies and sunshine, no obvious differences in the two weeks which was borne out by the daily yield figures.

I didn't try multiple MPPTs.