Hi, gang.
I'm excited to report that the first array on my fifth wheel camper is finished. But I am not pleased with the results.
The system is a "name brand" product with four 100w x 12v panels in series parallel with their 30A PWM charge controller. I'm using the Victron battery shunt for monitoring battery output, but using the controller's built in bluetooth to access the actual charging data from the panels.
Please follow along and double check my math.
The panels are mounted flat. The sky was clear and all four panels were in max sun at mid day, which reached an elevation of 62 degrees.
The system generated only 255 watts. That's just 64% efficient. To say that I'm disappointed would be an understatement.
I read that PWM charge controllers are 75-80% efficient. But I wasn't satisfied with the answer. There's still some watts missing.
Taking the sine of 62 degrees (or the cosine of 28) and multiplying by 100, I arrive at 88 watts. So, my theoretical maximum production as they lay on the roof is a combined 352 watts. Assuming a 75% efficient conversion for the charge controller, I'm only 10 watts away from my actual production.
Using the 80% figure and factoring in the temperature coefficient and some cabling loses and this satisfies my OCD.
Are my assumptions in the right direction? If not, I might have some other issues to address. Perhaps the charge controller is sensing the lead acid battery's charging inefficiencies and it is effectively lowering the displayed power??
Moving forward, I want to install two and possibly three 24v panels at 200 watts each and also arranged in parallel. They will be mounted on tiltable racks. I'm eyeing the Victron SmartSolar 100/50. I also plan on running AWG 8 from beginning to end to minimize wiring loss.
Assuming the new array is tilted towards the sun, what sort of overall efficiency/production can I realistically expect with the new MPPT controller?
