A city law banning the disposal of dead rechargeable batteries and requiring retailers to collect them takes effect today. The law is meant to limit pollution caused by toxic metals in the batteries, including cadmium, lead and mercury, and requires retailers to accept the batteries from consumers and return them to the manufacturers for recycling. The law authorizes the Sanitation Department to randomly check garbage and recycling containers for used rechargeable batteries and to check that retailers like Staples and Best Buy are complying. Consumers who dispose of the batteries face fines of $50 to $200; fines for retailers are $200 to $500, and for manufacturers, $2,000 to $2,400.