Battery chargers are devices used to replenish a drained or low-battery by supplying it with an adequate amount of electric power. Battery chargers are used to charge a variety of battery types, including lead-acid, nickel-metal hydride, lithium-ion, and nickel-cadmium. Lead-acid chargers are typically used for automotive batteries, while nickel-metal hydride, lithium-ion, and nickel-cadmium chargers are used for consumer electronics like cell phones and laptops. Modern battery chargers usually come with a number of advanced features such as reverse-polarity protection and automatic shutoff, which protect the battery from overcharging and potentially damaging it.