For some reason the MPPT calculator from Victron only allows an even number of solarpanels when you want one than one string. I want to connect seven 505Wp panels to one MPPT. Five in series in string one, which comes to 249v, so spot on. Then another two parallel in a second string. The panels are all 14amps max and 45v voc. I think this should not be a problem but I want to be sure and as I said, the calculator does allow two strings but only with same amount of panels
No you cannot connect uneven strings. It does not track each string separately. So 2x even strings is the way.
249v is too close to the 250v max anyway. Too risky to run it that high.
If you want to do that switch to the RS 450 series mppts. Even then one panel will not start up the mppt on that tracker. But you could just run them all in one string.
If it can’t track 2 strings separately, what does it matter if I connect an uneven number in 2 strings? What is worst case scenario that can happen? According to the calculator I could add 2 strings of 5 panels to this very same MPPT, so 5-5 is not a problem, 5-2 should be a problem, but why?
Btw regarding the 249v, the calculator even recommends the 250 MPPT when I select one string with 5 panels, so that should not be a problem
This cannot work.
What is being spoken of is PV strings being connected in parallel. If one string is more powerful, power will flow between the strings due to the potential difference. This constraint is not specific to Victron. Unequal PV strings should not be wired in parallel. If unequal strings are necessary, use a separate solar regulator per string. The MPPT calculator protects the user from making a fundamental mistake.
