Why is calculator rejecting my panels?

[Fideri (Fideri K)]

Hi everyone,

I suspect I’m missing something, but I can’t work out what. I’m designing an additional solar system (because I have extra components lying around) but the Victron MPPT calculator is rejecting my number of panels. When I enter 3 in series with 4 parallel strings, I get the right charger, exactly the model I plan to use, a 250/100. But when I enter 4 panels in series with 4 parallel strings, I get no result! I can’t figure out why.

Where the system will be installed, temperature is not an issue. The minimum we get is 15 degrees Celsius. The calculator always defaults to 10 degrees but that is not a problem for me.

My panel specs are:

• VOC: 49.90V
• ISC: 14.09A
• VMPP: 41.95V
• IMPP: 13.11A

So total VOC with 4 panels will be 199.6V and total ISC will be 56.36A. I understand there will be clipping, which is OK by me.

So why is the calculator rejecting 4 panels but accepting 3 panels on a 250/100? We are talking about a 48V system.

F.

[Skipper]

Did you allow oversizing above 130% under features?

[Fideri (Fideri K)]

Good catch. I suspect that is my issue. I will enable that and try again.

[Fideri (Fideri K)]

Update: Allowing oversizing beyond 130% works. With 3 panels, oversizing is 114% while with 4 panels, it is 133%. I guess I will go with 3 panels.