mppt vs pwm

BFL13 wrote:
If voltage is lower than Vmp you get less power but go up in Isc on the IV curve, so to get lower power but also lower amps, you have to raise the panel voltage?

Yes.

Think of it this way. The controller has a supply side (PV array) and a demand side (battery and other loads). The supply side will only produce what the demand side requires.

During low SOC and/or high load demand the MPPT controller will look for the highest power output to supply the demand. The PV array should be at Vmp at this time.

At higher SOC and/or lower load demand (Abs and Float) the PV array can supply the demand at less than full panel power. The controller will switch from MPPT to Abs or Float (Rogue MPPT is not functional in Abs or Float as max power is not needed). Panel voltage is adjusted to supply the power that is needed. It will be somewhere between Vmp and Voc. The lighter the demand the closer panel voltage will approach Voc.

In Float I will see 2 amps or so going into the batteries. This equates to less than 1 amp on the panel side. If you look at a typical IV curve the only place you will find 1 amp output is near Voc. I have verified this as panel voltage is 41 to 42 volts in float with little to no loads.

I have done as JiminDenver described earlier and slowly added loads while in float. As demand increased, PV voltage decreased. At about 17 amps (still only 2 going to the batteries), the controller gave up and switched back to MPPT to supply the demand.