question

Something seems to be off with the Victron calculator.

Presumably your battery Voltage is 12V?
For 2 of your panels in series you'd need at least a 100/30.
For 3 in series you'd then need a 100/50 or a 150/45.

to be clear, a 100/20 would also work but your output current would be limited to 20A. It is still interesting to have panels over sized as they provide extra power in the winter and you often don't need over xA charge max. Of course, all other things being equal the 100/30 will be a better choice. In Uk its £140 to £200 ish so depends how price sensitive you are.

Warning 2 pannels : P=360 Wc

If voltage battery = 12V

You Lose energy, because the power will be limited to 290W

If voltage battery = 24V it's OK

With 3 pannels : P= 540W Same conclusions

Power limited at 290W (12v) so, half of available power lost, between us, I'll take the model above

And OK under 24V but Very close to the limit. The victron electronics should resist but it is good to leave few Watt

But Me too, I'm experimenting with solar on a camper van. I guess the panels aren't reclining, but flat On the roof ? You are not in the ideal angle To get the maximum power, but you will not hope to add more power with biggest panne.

I dont have features of the SmartSolar MPPT 100/30 on this datasheet

Sorry for my (and Google trad lol) bad english.

RN

The online calculator gives different results than the excel version which also has the benefit of more information.

Going strictly by max potential power you're well into 100/30 territory. But the question is how likely are you to produce it? Lets face it, in the middle of a sunny day you're more likely to park in the shade than look for the best angle to the sun. And you won't get anywhere near max power in winter when the opposite is likely true. Also, batteries will likely approach absorption phase before the panels are producing max power so output will be limited anyway.

There are obviously other potential scenarios where you might see the 100/20 shedding power but how often that could happen depends on how you use the van.

So, if price (maybe size?) is an issue you might be fine with 100/20. If not, just get 100/30 and not worry about it.