D batteries are a standard size of ‘dry cell’ battery. These are the easily interchangeable models widely used in electronic and domestic devices. The term ‘dry cell’ is used to distinguish them from more specialist ‘wet cell’ batteries which, as the name suggests, contain liquid.
What does a D size battery look like? Typically, they are squat and solid, with a barrel-like shape. The positive contact point or terminal on the top of each battery has a distinct metal cap shape.
D batteries were first invented in 1898. Today, they are also known as R20s, after their designation by standards body the International Electrotechnical Commission (IEC).
D size batteries are available as both standard non-rechargeable and rechargeable models.