Batteries can release high power, and most packs include protection to safeguard against malfunction. The most basic safety device in a battery is a fuse that opens on high current. Some devices open permanently and render the battery useless; others are more forgiving and reset.
Battery packs achieve the desired operating voltage by connecting several cells in series, with each cell adding to the total terminal voltage. Parallel connection attains higher capacity for increased current handling, as each cell adds to the total current handling. Some packs may have a combination of serial and parallel connections.
A battery is an electrochemical device that produces a voltage potential when placing different metals in acid solutions. The open circuit voltage (OCV) attained varies according to the metals and acid solutions (electrolyte) used. Applying a charge or discharge places the battery in the closed circuit voltage (CCV) condition; charging raises the voltage and discharging lowers it.
Early batteries were in jars, but mass production changed the packaging to the cylindrical design. The year 1896 pioneered the large F cell for lanterns; the D cell followed in 1898, the C cell in 1900, and the popular AA was introduced in 1907. Design criteria and cost considerations required new battery formats that offer distinct advantages over the cylindrical design.