Ever wondered why some batteries are labelled AA, AAA or even AAAA?

The naming system goes back to the early days of radio, when ‘A’ batteries powered low-voltage circuits and ‘B’ batteries supplied high voltage. By the 1940s, the American National Standards Institute (ANSI) had standardised battery sizes using letters to indicate their dimensions.

Originally, battery sizes progressed alphabetically: A, B, C, D and so on. But when electronics started shrinking in the 1950s, smaller sizes like AA, AAA and AAAA were introduced.

ANSI still lists sizes from AAAA through to G, along with odd ones like J (designed by Kodak) and N (named after the chemical symbol for mercury).

Some sizes, like A, have disappeared, while others, like B, are still used in certain applications, such as bicycle lights in the UK.

The system is far from perfect. The 9V battery, for example, does not follow the letter naming at all; it likely did not need one because of its unique shape.

Outside the US, the letter system is not even used. Instead, batteries are labelled based on chemistry and dimensions, which is why an AA battery might also be called LR6, MN1500, or E91, depending on where you are.

Despite the inconsistencies, the familiar AA, C, and D labels are not going to disappear. Manufacturers worry that switching to a more technical system would confuse consumers. So, for now, we are sticking with this quirky, decades-old naming tradition.