Batterys

A battery is a device that stores chemical energy and converts it to electrical energy through electrochemical reactions. It consists of one or more cells, each with a positive electrode (cathode), a negative electrode (anode), and an electrolyte that allows ion flow. When connected to a circuit, chemical reactions drive electrons through the external path, producing current. Batteries are divided into primary (non-rechargeable) and secondary (rechargeable) types.

Common chemistries include lead-acid, alkaline, nickel-metal hydride, nickel-cadmium, and lithium-ion. Lead-acid is inexpensive and robust, widely used for automotive starting and backup power but is heavy with relatively low energy density. Alkaline batteries are common primary cells for household devices. NiMH offers higher energy density than NiCd and is used in hybrids and many rechargeable devices. Li-ion batteries provide high energy density and dominate portable electronics and electric vehicles, with various chemistries and protection features to manage charging and temperature.

Performance is described by capacity (charge stored), energy density (energy per weight or volume), power density (how quickly energy can be delivered), and cycle life (how many charge-discharge cycles before significant capacity loss). Charging and use require proper charging equipment and, for many chemistries, a battery management system to ensure safety and longevity.

Safety and environmental considerations include the risk of overheating, leakage, and fire if misused. Most batteries contain hazardous materials and should be recycled or disposed of according to local rules. Recycling recovers materials such as lead, nickel, cobalt, lithium, and plastics, reducing resource use and pollution.