Batteries are devices that store energy and convert it into electrical energy. They can be rechargeable or disposable, and can be used to power a variety of devices. Most common batteries are made up of electrochemical cells, which contain two electrodes separated by an electrolyte which can hold electrical charge. When these electrodes are connected to a load, they produce a current of electricity. The most common type of battery is the lead-acid battery, which is used to start vehicle engines and store energy from solar panels and wind turbines. Other types of batteries include lithium-ion and nickel-cadmium batteries, which are used in consumer electronics, as well as nickel-metal-hydride and alkaline batteries which are used in everyday items such as torches and remotes.