MPPT sizing calculator question Isc above Impp

DIY
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1

Overpaneling by 150% here, the Isc is exceeding the max current the MPPT can handle: 35A:

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Reading here:

I played around with the calculator and it seems that Victron looks at the Impp when suggesting an MPPT controller.

From my understanding it’s OK to overpanel as the MPPT can only output 70A (4000W) and therefore we’ll never see the Isc from happening. Is this true?

But the experts in the mentioned discussion regard Isc as a very hard limit.

As a protection, could I add a 35A quick fuse before the MPPT to avoid a short-circuit situation before the MPPT controller.

The MPPT 250/85 is an option as well, but I’m more interested in the theory here and why Victron is OK with exceeding the Isc in the calculator.

2

The voltage is a hard limit the current is a max 35A in and 70A out. These mppt’s from what I have tested prefer a high current compared to a high voltate low current.

Why dont you look at 450/100 with 2 trackers? In Australia they the same price.

You really need the 250/85 or 250/100. But looking at the real word case for the panels they will not see STC current and voltage. You will be more like 13A-14A mpp

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3

The 250/100 is about 50% of the price of a 450/100.

I’m curious about the suggestion from Victron why they take the Imp and not the Isc for the max current the MPPT can handle.

4

I have never seen it before. The 450/100 has a MPPT of 16A and 20ISC per a tracker. Its a beast. These non-isolated MPPTs are likely to weld together send the array voltage to your gear if they fail. It’s very unlikely the electrical parameters for the panels will be seen on the input of the MPPT more likely the NOCT. When you get a cloud voltage and current does peak to the max panel rating and beyond for a few seconds. I have seen over 110A 12A from the panels with my 450/100. They have isc of 11A and should only output 2700w per a tracker. This is the only controller I have seen with a limit not equal to the output.