Question on dimensioning MPPT for panels

[Messier11]

When I use Victron's mppt calculator I get this suggestion:

What I don't get is that when I do the math myself, I get the following result:
13.45A * 3 in parallell * 34,2 * 5 in series / 48v (system voltage) = I get 140 amps, and that is not even counting with the tempretur adjustments. The system voltage of 48v is of course a bit low (will perhaps be 54v in reality). But the suggestion is still significantly underdimensioned (20-30%).

Is it recommended to overdimension the panels to this extent? Or is my math wrong?

 

[SamDeleted]

6.9kw of panels ÷ 54v = 127amps of charge to your battery

So I think the 100amp victron should be fine you're just over-paneling it , clipping the last 27amps

 

[SamDeleted]

I'd probably go for two smaller MPPTs, 60/70amps , but thats going to cost a pretty penny in blue

 

[sunshine_eggo]

When I use Victron's mppt calculator I get this suggestion:View attachment 145995

What I don't get is that when I do the math myself, I get the following result:
13.45A * 3 in parallell * 34,2 * 5 in series / 48v (system voltage) = I get 140 amps, and that is not even counting with the tempretur adjustments. The system voltage of 48v is of course a bit low (will perhaps be 54v in reality). But the suggestion is still significantly underdimensioned (20-30%).

Is it recommended to overdimension the panels to this extent? Or is my math wrong?

I have that charge controller. It's limited to 5800W output on a 48V battery (assumes 58V charging), but you can overpanel it like crazy. You could hang another 2 strings for a 5S5P array of your panels and be under the input limits.

460W * 15 = 6900W.

Victron does not make a controller over 100A except for the RS 450/200, and that one will make you poop your pants on pricing.

The reality is that you will rarely get 100% output from your array. When you do, conditions will have to be absolutlely perfect, and it will only be for an hour or so a day. Check for the NOCT ratings of your panels, that's much more realistic.

When you look at it on an annual basis, you might lose 0.1% of the total kWh potential.

Additionally, Victron routinely allows for over-paneling for this very reason.

For comparison, I have unbelievably good solar. I'm in the high desert @ 2000m elevation - thin air, cool temps, and clear skies. My array outputs > 90% rated about 3% of the time over the solar day. Some days are fricken fantastic, and I get > rated, but again, my solar conditions are actually capable of producing > STC conditions.

If you want to spend more to make sure you convert every possible photon into electrons, then you'd need to get two controllers, or take out a loan for the RS 450/200.