A rechargeable battery, also known as a storage battery, is a group of one or more electrochemical cells. They are most commonly known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in various shapes and sizes, ranging from a button cell to complete megawatt systems connected to stabilize an electrical distribution network. Different combinations of chemicals are commonly used, including: lead-acid, nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), and lithium ion polymer (Li-ion polymer).
Rechargeable batteries have a lower total cost of operation and they have a much smaller environmental impact than disposable batteries. A large number of rechargeable battery types are available in the same sizes as disposable types. While rechargeable batteries often have a higher initial purchase price, they can be recharged very cheaply and used many times.