Competency 3: prove the system with numbers. Panel checks in full sun: Voc across open terminals (should be near nameplate), Isc briefly through the clamp meter with a short-rated meter (near nameplate). Battery: rested voltage tells state of charge — 12.7 V full, 12.2 V half, 11.9 V empty for lead-acid. Controller: input vs output amps proves charging. Every reading goes in the commissioning sheet, which is the customer's warranty document.