Oversize 100/30 mttp blue solar

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alan-offgrid-van asked Feb 12, '23

Oversize 100/30 mttp blue solar

Bit of a newbie question.

I have a 100/30 mttp with 3 Victron 140W Solar Panel – Monocrystalline Panel in series hooked into a 200ah lithium 12v battery

Solar specs sre:

140w

Voc 23.6 open circuit voltage

Isc 8.05

Llmp 7.22

Vmpp 19v

So everything is in tolerance…I believe, and all working. I am trying to maximise the set up, so am considering adding an additional panel that would oversize it

System located in Scottish Highlands, so northern hemisphere and low number of optimal days

If I add another panel, by my calculations 4 panels in series - 27% oversized

Watt = 560

Voc = 94.4

Amp = 8.05

Does this look correct? Will this be ok?

Does anyone have any other suggestions for maximising the above, like wiring panels in parallel?

Many thanks

solar

2 |3000

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Answer 1 · 2023-02-12T10:09:24Z

wkirby answered · Feb 12, 2023 at 10:09 AM

Having 560W of PV feeding this controller will not be a problem. The MPPT will take as much as it possibly can from the array. Over sizing the array is a good idea especially in areas where fine weather is rare.
The Voc figure is given for a panel temperature of 25°C. At lower temperatures, which I believe are likely in Scotland, then this Voc figure will be higher and may exceed the 100V limit of your controller. The MPPT controller is likely to be damaged if your PV Voltage exceeds 100V.
It would be better to wire the four panels two in series strings which are in parallel. This would bring your Voc down to a safe level for your controller, but it would still be high enough to work well in a 12V system.

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alan-offgrid-van commented · Feb 12, 2023 at 08:47 PM

Thanks fir your advice. Much appreciated.

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