Battery Sizes
Batteries come in a wide array of shapes and sizes, 
each particularly designed to power certain types of electronic devices. But the two most common consumer battery varieties are the cylindrical battery and the prismatic (rectangular-shaped) battery.
Starting with the cylindrical batteries, the standard-sized dry cell battery is the single cell AAA (Triple A) battery, which has a length of 44.5 mm and a diameter of 10.5 mm. AAA batteries made with alkaline weigh approximately 11.5 g, while Li-FeS2 (lithium battery) AAA batteries are about 7.6 g in mass. A rechargeable NiMH (Nickel-metal hybride battery) AAA battery usually weighs 14-15 g. AAA’s are typically used to power small electronic devices like digital cameras, remote controls and MP3 players.
The AA (Double A) battery is another standard battery size, measuring a length of 51 mm or 20 in (50.1 mm (1.97 in) excluding the button terminal), and a diameter of 13.5-14.5 mm (0.53-0.57 in). An alkaline AA battery weighs around 23 g (0.81 oz), a lithium AA weighs about 15 g (0.53 oz) and a NiMH AA is roughly 31 g (1.1 oz) in mass. AA batteries are normally used for powering portable electronic devices.
The C size battery (or simply C battery) has a diameter of 26.2 mm and a length of 50 mm. It is used for medium drain applications like electronic musical instruments and toys. The D battery (D cell) measures 34.2 mm in diameter and 61.5 mm in length. It is commonly used to power flashlights, and was in fact introduced as the first flashlight battery in 1898. Aside from that, the D cell is also used for high current drain applications such as radio receivers, transmitters, boomboxes, and others.
The 9-volt battery, also known as the PP3 battery, is a prismatic battery measuring a height of 48.5 mm, a length of 26.5 mm, and a width of 17.5 mm. 9-volts function as back-up power for alarm clocks and digital clocks. Apart from that, they are also used for transistor radios, smoke detectors, radio-controllers, and guitar effects devices.
The Lantern battery is another prismatic battery which, as its name implies, is used mainly for lanterns and flashlights. It measures 115 mm in height, 68.2 mm in length, and 68.2 in width. It comes in four versions, the most common being the 6 volt, which is characterized by its spring or screw terminals. Other versions include the 4.5 volt, which has two metal strips for terminals and is used in disposable flashlights; the 7.5 volt, which has screw terminals, a rectangular base, and usually has a carrying handle between its terminals; and the 12 volt, similar to the 7.5 volt, but used in powering electrical car accessories outside of a car.
