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Cloudinspector

Solar controller

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I would like to add an additional solar panel to my current array. This would make the system comprise of 4 x 100w panels wired in series.

The charge controller that’s fitted along with 3 existing panels is a Victron 100/30 i.e 100v/30amp. 

Using the calculation for required controller size, peak panel watts / battery voltage a figure of 33amps is stated.

400w/12v = 33.3 amps

this is 3 amps more than my Victron controller capacity.

Would It be safe to add the 4th solar panel without changing the controller as the over capacity of the panels is only 3amps?

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12 minutes ago, Cloudinspector said:

I would like to add an additional solar panel to my current array. This would make the system comprise of 4 x 100w panels wired in series.

The charge controller that’s fitted along with 3 existing panels is a Victron 100/30 i.e 100v/30amp. 

Using the calculation for required controller size, peak panel watts / battery voltage a figure of 33amps is stated.

400w/12v = 33.3 amps

this is 3 amps more than my Victron controller capacity.

Would It be safe to add the 4th solar panel without changing the controller as the over capacity of the panels is only 3amps?

Yes.

 

You will never get more than 30A out of the panels, as the controller will limit it,  but you are unlikely to get anything like that much most of the time in the UK. 

 

If we have a crazy hot summer and you are worried about it, you can always unplug the 4th panel, but you won't need to.

 

 

To add: when it's charging from solar, your battery voltage will be around 14V anyway, not 12V nominal.

 

400W / 14 V ~= 28.6 A anyway

 

 

Edited by TheBiscuits
spellink

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Check the controller instructions, but my Tracer says you can fit panels to twice the nominal current rating - you just won't get more current out than the controller rating.

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44 minutes ago, Cloudinspector said:

I would like to add an additional solar panel to my current array. This would make the system comprise of 4 x 100w panels wired in series.

The charge controller that’s fitted along with 3 existing panels is a Victron 100/30 i.e 100v/30amp. 

Using the calculation for required controller size, peak panel watts / battery voltage a figure of 33amps is stated.

400w/12v = 33.3 amps

this is 3 amps more than my Victron controller capacity.

Would It be safe to add the 4th solar panel without changing the controller as the over capacity of the panels is only 3amps?

The power shouldn't be a problem, the specifications for the smart version is a max power of 440w.

 

Possibly of more concern is the maximum voltage that you will get out of your 4 panels in series, as noted in the manual. Perhaps two parallel pairs of series connected panels would be better.

 

The images are from the smart solar manual. If yours is the non smart version, you can get the right manual to check from the  Victron website.

IMG_0647.PNG

IMG_0648.PNG

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Are your panels mounted flat or do you track the sun?  If the former you will never get more than about 70% of the rated output.

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1 hour ago, andy3196 said:

Possibly of more concern is the maximum voltage that you will get out of your 4 panels in series, as noted in the manual. Perhaps two parallel pairs of series connected panels would be better.

^^^^^ This. The extra power will be of no consequence but raising the voltage above 100V will kill that controller. So 4 panels wired as above (two series pairs in parallel) would be best. 

1 hour ago, Detling said:

Wired in parallel gives better performance in partial shade.

And worse performance in low light (autumn/winter). Swings & roundabouts. 


The two pairs in series/parallel is a good compromise. 

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I have just added an extra panel, I now have 4 x 170w into a 150v/40amp mppt controller, I have wired them up as 2 series pairs in parallel,  will see tomorrow what voltage/amps are being put into tha batteries. 

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8 hours ago, WotEver said:

^^^^^ This. The extra power will be of no consequence but raising the voltage above 100V will kill that controller. So 4 panels wired as above (two series pairs in parallel) would be best. 

And worse performance in low light (autumn/winter). Swings & roundabouts. 


The two pairs in series/parallel is a good compromise. 

The panels have an open circuit voltage of 21.24v so a combined voltage of 84.96 is well below the 100v max or am I missing something?

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4 minutes ago, Cloudinspector said:

The panels have an open circuit voltage of 21.24v so a combined voltage of 84.96 is well below the 100v max or am I missing something?

 

No, that's fine, but as you hadn't provided that information earlier some people took a guess and warned you of the issue.

 

If your panels Voc was 30V then three would be fine in series but 4 could cook the controller.

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10 minutes ago, Cloudinspector said:

The panels have an open circuit voltage of 21.24v so a combined voltage of 84.96 is well below the 100v max or am I missing something?

Remember that the Voc is at a certain temperature and there will be a factor that it increases by for each degree centigrade below that temperature.

 

Explained, with a worked example, at https://www.ecmweb.com/renewables/article/20896643/the-highs-and-lows-of-photovoltaic-system-calculations a fair way down the page.

 

so you might need to consider what they will be doing on a really cold winters day.

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14 hours ago, TheBiscuits said:

 

No, that's fine, but as you hadn't provided that information earlier some people took a guess and warned you of the issue.

 

If your panels Voc was 30V then three would be fine in series but 4 could cook the controller.

Just so :)

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