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wytco0 asked

MPPT Sizing query - Victron Calculator incorrect?

Hi I am trying to size a Victron MPPT for use with my 5kVA Multiplus II as I move away from my current Growatt Hybrid inverter.

I have 2 strings of Canadian Solar 455W panels with 5 panels in each string. Initially I want to move 5 panels to a new Victron MPPT for connection to my Victron system. The manufacturers figures for each panel are Wp=455 Voc=49.3 Isc=11.66 Vmpp=41.3 iMp=11.02 with 35m of 6mm cable connecting them to the Mppt, temp coeff are the same as the default from sizing tool.

The Victron calculator is giving me strange results, with a string of 4 panels it recommends the SmartSolar MPPT 250/60 Tr but when I state 5 panels it offers only the SmartSolar MPPT RS 450/100-Tr.

The string is only about 2.25 kw so I am surprised that there are not more options for Victron Mppts, the economics are not great if I have to by 3 of the largest available to support 4.5kw of panels, they are currently handled by a single 5kw hybrid inverter.

Am I missing something important? or is there an issue with the Victron sizing tool?


TIA


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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @wytco0

That result looks correct.

It’s mainly based on the strict PV input voltage limit. Those panels have a very high open circuit voltage of 49.3V. Once accounting for temperature, 5 in a string is over the 250V limit of the 250/60.

Try with 9 panels and running 3 parallel strings of 3 instead?

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wytco0 avatar image wytco0 commented ·
Of course I didn't think about paralleling them (is that even a word) from a quick look I think it would accept 2s 5p as well.


Thanks

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