Henry,

You said that the ST and STXR units can't read DC current. Was the DC current measurement added to improve MPPT?

Gordon

Hi Gordon,

Yes , current is needed to calculate DC power from the array ... There is a daughter card added to the XR/GP with the DC sense circuit to do this ... The original ST ST/XR had a non-functional circuit with the needed drop resistor , what I designed was the differental circuit to measure , scale and average for the CPU.

The original designer felt mppt could be found using the AC power , to slow for cause and effect , or loop speed , when that didn't work they tried guessing by the voltage drop which was triggered by many other no mppt events.

Henry [img]images/smiles/icon_razz.gif[/img] [img]images/smiles/icon_razz.gif[/img]

Henry and all,

May previous highest daily energy producion with my ST2500 connected to 48 SP75s (3600 peak watts) set at 10 degrees below my latitude angle, facing due south, in San Diego County was 18.8 kWh in late April 2002. Yesterday, using the XR/GP, the system produced 19.25 kWh. Onward to 20 kWh!

Gordon

Holy Photon Batman !!

Thats allot of power from a single inverter !

Based on the different in perfect conditions between the ST and XR/GP , you'll hit 20.88Kw according to my trusty decoder ring ... maybe ever 21Kw , if you clean your panels !

Upload the logs when it happens !


Henry [img]images/smiles/icon_biggrin.gif[/img] [img]images/smiles/icon_biggrin.gif[/img]