Posted March 29, 20205 yr I have been experimenting with a voltronics VMII ( 2017 model) which has rated pv input 120V to 450V. I think its the Axpert range. Serial request returns VMII-5000. Seems as if SCC only kicks in if PV voltage is over 150V but will operate below this value once on. Has anyone else experienced this issue? Would have implications for solar panel selection. I have also seen very different pv input voltages in other forums. Seem as if Voltronics might have changed PV specifications? Any colour much appreciated.
March 29, 20205 yr 10 hours ago, MTS said: Seems as if SCC only kicks in if PV voltage is over 150V but will operate below this value once on. Has anyone else experienced this issue? I don't think that this is an "issue"; most solar charge controllers work that way to prevent a "jagged start" in the mornings. I believe that the 150 V minimum start voltage has always been there. The consensus seems to be a minimum of 6 panels, though I don't know if that changes if they are 60 versus 72 (or even 66) celled panels.
April 18, 20205 yr This is similar to the MPP 3024GK, it works with 250w X6 at 30v each. It didn't work when I used 4 panels.
January 30, 20223 yr This inverter works in this way, when sun starts rises solar produce open cuicuit voltage with zero amp to charge capacitor on Mppt, when sun moves up, voltage drops to vmp and amp starts from zero to maximum 12h00pm until mid day. If inverter says 120 - 450 it's for VMP. 500v for open cuicuit. To meet 120 vmp 1st Option, You need 5 panels for 250 watts 60cells, because open cuicuit for this pannels is 37 * 5 = 185v Vmp 29*5=145v (if you use 4 panels it will be 29*4=116v, It's not meet minimum requirements) 2nd Option You need 4 panels that has 72 cells. Open cuicuit 43*4=172v Vmp 37*4=148v
February 1, 20223 yr All MPPTs that I have seen needs a higher start voltage than what they would operate at. Take the smaller Solis grid tied that needs only 2 x 60 cell panels to start which is over 60V @ very low current. After the start you need only 50V. The 30/115V Axpert with 145V max MPPT will start at about 35V @ 2W early in the day.
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