I have a VM iii with an mppt range of 120v to 450v and startup voltage of 150v, will be using 355 watt Canadian Solar panels, Vmp is 39.4, am thinking of starting wit five panels, will the charge controller be dropping in and out depending on conditions, eg, clouds passing overhead or is 5 panels ok

Tariq you need to do the Volt maths using VOC. For that panel I think it is around 45-46V

Ok, thanks, Voc is 46.8 so for 5 panels it is 234 volts, that should be enough I assume

I recall someone needing 6 panels minimum, but I think that they might have been 60 cell panels. Yours sound like 72 cell panels; 5 panels of 72 cells is the same total number of cells (360). So I'd say you'd be fine.

Remember that the Voc figure is for 25°C and 1000 W/m², so at dawn it will be a bit different (not very much).

Edited April 3, 20205 yr by Coulomb

Thanks Colulomb, yes, they are 72 cell panels, due to budget consideration, have to start  small