KMC-3 - Which batteries will last the longest?

We recommend alkaline “D” cell batteries or, especially if battery power will be used often, rechargeable “D” cell batteries with a separate charger (the KMC 3 will not recharge batteries). For many of our tests we used Energizer alkaline “D” cells, rated at between 10,000-20,000 mAh, depending on the load. With batteries, like anything else, you get what you pay for so we recommend a known brand name with a higher mAh rating. NiMH rechargeable batteries and a charger for them cost more initially but would pay for themselves in the long run if you plan to use battery power on the KMC 3 frequently.