Adding more solar panels

2Brooktrout

My system currently has 4-Rec Twin Peak 310 watt panels (Voc 39.8, Vmp 33.5, Imp 9.26) in a single string powering through a Magnum PT-100 controller ( 224 volt max).  I would like to add more panels but the ones I installed are not available.  Can I add 4 more similar panels by making another string of 4 panels and running through a combiner box? Wiring from the panel combiner box is sufficient for the added amperage but the Voc of the two strings would be different by a few volts. Would it be better to break up my existing string and make two strings with 2 new and 2 old panels so the end operating voltages would be similar?

solar_dave

Generally you need panels within 10% of the original specs.