question

alwaysinthelight avatar image
alwaysinthelight asked

[SOLVED] complex solar panel setup...

I'm reading (here) as much as I can to be able to choose the components I need but it's a steep learning curve and I am not confident I can make the right choice...

Solar panels: JA Solar 405Wp

(Parameters at Standard Test Conditions)
-Open Circuit Voltage (Voc) [V]: 37.23
-Max Power Voltage (Vmp) [A]: 31.21
-Short Circuit Current (Isc) [A]: 13.87
-Max. Power Current (Imp) [A]: 12.98


I have 2 solar panel locations:
- 6 panels will fit on a high roof facing south, 51 degree angle
---> PROBLEM: 1 panel partly in the shadow until 1 PM

- 4 panels will fit on a garage roof facing South, flat roof (E-W placement)
---> PROBLEM: all panels in the shadow until 1PM

System:

- Victron Multiplus II 48/3000 ??
- battery: Victron 48V LiFePo ??

But my main problem is choosing the MMPT's !

how to group the solar panels, for example: the one on the roof which has shadow, is is better to connect it to a seperate MMPT?

Many thanks to anybody willing to help me out!


MPPT Controllers
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3 Answers
gazza avatar image
gazza answered ·

Yea, you don't want to compromise a string of panels with one that is mostly in shade.
If the distance between panel groups was not too far then it may be worth thinking in groups as "shaded" and "non-shaded" rather than as the 6 and 4 that you are proposing, still with separate MPPT chargers.
On the other hand if the rogue panel just can't be re-sited to a better position then it may not be worth the effort of more complicated cabling?

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alwaysinthelight avatar image alwaysinthelight commented ·
Thank you for confirming my thoughs: I will indeed make 2 groups of panels (high roof with no shade and garage with partly shade) each with their own MPPT charger. The one shaded panel on the roof will be omitted from the plan.
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gazza avatar image
gazza answered ·

The quick answer, you would be better having 2 MPPT chargers, one for each group.
You can use this link to play around with each configuration to see what suits you best for each group. https://www.victronenergy.com/mppt-calculator

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alwaysinthelight avatar image alwaysinthelight commented ·
Thank you for your suggestion! What are your thoughts on the one panel on the high roof that is partly shaded until 1 PM: Should I remove this panel from the plan so that is does not influence the whole string by the shadow?
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nickdb avatar image
nickdb answered ·

How shaded is shaded? That's a big part of the day you are compromising.

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alwaysinthelight avatar image alwaysinthelight commented ·

Thank you for your reply! Of the 6 panels of the high roof, 1 of them would be partly shaded until 1PM and the 4 panels on the garage would be partly shaded from the house until they have full sun at 1PM.

I think it would be better to ditch the one panel on the roof that has shade?? If I put it in series with the 5 non shaded one it will affect the whole group?

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