Connecting PV modules in parallel involves wiring every one of the constructive terminals of each panel jointly and performing the same for many of the destructive terminals. With out a demand controller, variations in voltage and amperage from unprocessed energy would permanently damage or ruin delicate battery cells. Polycrystalline panels https://www.americanarraysolar.com/4-factors-to-remember-when-choosing-the-solar-company-visalia/