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matias-b asked

Short circuit current safety factor?

Hello!

I just ordered three additional 160w panels in addition to the one I have. The charge controller I have is a Victron Smartsolar 100/20. (Yes I know I am totally overpanelling in regards of the controller, but I live quite far up in the north so sun is weak in spring and fall) Battery will be 2x100Ah Victron Super Cycle in series for 24v.

The plan was to put the panels in series achieving a total of 71.6V which is within spec even at -40C. However I realize now it would be smarter to put them in two parallel and two series configuration because of how the sun starts shining on them in the morning. It is not critical to do this but perhaps it would give me one more hour of charging per day.

Problem is the panels have an Isc of 9.99A. So in a 2S2P configuration that gives 19.98A, while the controller have a maximum of 20A Isc, so practically maximum.

This is uncomfortably close to maximum, so I must ask would this be safe? I see people on other forums claiming that one must add a 1.25 safety factor meaning I would need to upgrade the charge controller , others say it is already factored in the specs of the controller.

What are your thoughts?

MPPT Controllers
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1 Answer
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klim8skeptic answered ·

Problem is the panels have an Isc of 9.99A. So in a 2S2P configuration that gives 19.98A, while the controller have a maximum of 20A Isc, so practically maximum.

Thank you for reading the manual :).

This is uncomfortably close to maximum, so I must ask would this be safe? I see people on other forums claiming that one must add a 1.25 safety factor meaning I would need to upgrade the charge controller , others say it is already factored in the specs of the controller.

The mppt's 20a input current limit only comes into play if the PV array ever get connected to the mppt in reverse polarity. The safety devices in the mppt are only rated to withstand a 20a reverse voltage/current snafu, before they are damaged.

Your 2s x 2p array is probably fine, seeing as at temps below 25c, the current the array can produce reduces.

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