I am planning a PV solar system for my off-grid home in the Philippines. As a solar newbie I need some expert opinion(s) on a recent exchange I had with a solar panel provider in China. I had requested a quote on some different models of panels and they quoted 275 watt panels, even though they offer higher power panels. Their reply to my question as to why they did not quote the higher power panels follows:
- Why recommending 270W/275W: Please see below:
Panel Working Voltage Off grid voltage Conversion Rate
270W 31.1V 24V 24V/31.1V=77%
275W 31.3V 24V 24V/31.3V=76.6%
300W 32.8V 24V 24V/32.8V=73%
325W 37.5V 24V 24V/37.5V=64%
370W 39.4V 24V 24V/39.4V=61%
The principle is that no matter what solar panel voltage, it could only charge a 24V system ( if you need 48V system, you need 2pcs, the principle is same), so the system voltage is fixed, it is 24V or 48V, then the total watt you get is 24V multiply by the current, so the voltage is wasted, no need to use high voltage. So I recommend 270W or 275W, it is enough. Or you can also choose PERC mono 300w, but price is expensive than poly.
I’m a little confused by their explanation as it is my understanding from reading other solar blogs that the output higher power panels would not be wasted but would in fact charge my battery bank more efficiently?