mppt vs pwm

BFL13 wrote:
Well somebody please nip out there and measure panel voltage during Absorb/Float while running a load that puts amps above array total Isc.

It is easy to do. Just put the meter across the pos and neg controller input terminals or do it out at the panel. Nothing disconnected of course.

My Vmp is 30v so when I check for that when MPPT is on I get 29.3 at panel and 29 at controller. So I have a 1% line loss there. YMMV. Trouble is I never took the voltage later on after it dropped out of MPPT. Can't check again till after mid-April.

So somebody here must be on MPPT solar now that can help out! :)

D

The higher the SOC, the closer the panel voltage will approach Voc. The power pulses become shorter with longer time between. Panel voltage rises to Voc.

It's probably not correct to think of your Vmp as a set number such as 30v. That might be the published voltage at STC, but it varies with irradiance and panel temp. My panels have an STC Vmp of 36 yet I see voltages from 31 to 36 when charging in MPPT. That is the point of an MPPT controller. It you see 30 volts all the time I would have to doubt that it is truly MPPT.