Energizer, Duracell rate as top batteries by Consumer Reports. ... Among flashlights, the battery life for an Energizer lasted about 7.3 hours. Falling short were Duracell batteries (6.8 hours) and Toys 'R Us brand cells (4 hours). Overall, that Energizer Lithium tested best, while Duracells tested well for alkaline cells.Dec 23, 2013