I recently upgraded my solar setup from a Zamp PWM controller to a Victron MPPT 75 |15 controller, hoping to get better power yield under varying shade conditions. While the old Zamp controller worked just fine, the new Victron doesn't charge at all on most days. Zero Amps, nothing. It looks like there is some rule in the Victron that says the PV panel Voc has to be 5 Volts higher than the battery voltage for the controller to start working. I hardly ever reach that extra 5V and on most days I get no charge at all. What am I missing? Is there a way to turn that arbitrary (and counter-productive, in my opinion) value down to a more reasonable value?
Here is what's happening:
PV panel specs:
210W (nominal) panel is mounted flat horizontally on my RV rooftop
Voc=19.83V (on a typical summer day in the morning I get 17.5V)
Vmp=16.77V
Battery (Lithium) specs:
Vbulk=14.4V
Vfloat=13.5V
Victron MPPT 75|15 configuration:
Default LiFePo setting
So if the battery is at, say, 14.2 Volts and my horizontally mounted panel produces Voc of 17.5V the Victron will never start up, although under identical conditions my old PWM dinosaur charges the same batteries from the same PV panel at about 7 Amps. There have been days when the Victron did start up but that was only about 2 or 3 days in April/May.
