Solar Panel Voc-MPPT?
Wondering if there is any relationship between measured Voc and MPPT performance with a 24v panel. My 12v panel has a Voc rating of 21.9 and Isc of 8.2, but I often see 8.2ish when Voc is only 20....
Forum Discussion
red31 wrote:ken white wrote:
The PWM Controller makes the solar panel assume the battery voltage under normal operating conditions,
What makes the panel match batt voltage without a controller, ie directly connected?
The panel has an operating space where it acts as a constant current device - its internal impedance varies linearly with supplied voltage.
An ideal constant current device can assume any voltage across it.
The panel also has an operating space where the resistance changes non-linearly with voltage, and this starts to occur at the voltage point when the panel current starts to diminish quickly for a given irradiance.
Maximum panel power occurs on the non-linear resistance part of the I-V curve and that's where the MPPT controller operates.
A battery also has an internal impedance that is dynamic and is a function of its internal charge level and the physical condition of its plates.
If we were only interested in maximum power transfer, it would occur when the controller acts as an impedance matching device and matches these two internal impedances.
