What Are the Square Batteries

The nine-volt battery, or 9-volt battery, is a common size of battery that was introduced for early transistor radios. It has a rectangular prism shape with rounded edges and a polarized snap connector at the top.

What uses a square battery?

A nine-volt battery, either disposable or rechargeable, is usually used in smoke alarms, smoke detectors, walkie-talkies, transistor radios, test and instrumentation devices, medical batteries, LCD displays, and other small portable appliances.

What's the difference between C and D batteries?

C-sized batteries are smaller than D batteries but larger than AA and AAA batteries. They are: 50mm or 1.97 inches in length. 26.2mm or 1.03 inches in diameter.