When sourcing Lr20 (D size) batteries, you must prioritize nominal voltage (1.5V) and discharge capacity, which typically ranges from 12,000mAh to 18,000mAh depending on the load. Ensure the battery uses high-purity manganese dioxide and zinc powder to prevent internal resistance buildup. For industrial or high-drain applications, verify the leak-proof structure and the use of a stainless steel jacket to prevent corrosion and ensure structural integrity over a long shelf life, which should ideally be 5 to 10 years.