It is actually the result of a series connection of two cells of 3.6 (3.7)V. The actual voltage is 7.2V.
Generally divided into: 1, 2, 3, 5, 7 number, of which 5 and 7 are especially commonly used, the so-called AA battery is the 5th battery, and the AAA battery is the 7th battery. AA and AAA are all descriptions of the battery model. The specific models are as follows:
1, D type battery (large battery / LR20 / AM1) diameter ф34.2; height 61.5mm.
2. C-type battery (No. 2 battery / LR14/AM2) Diameter ф26.2; Height 50.0mm.
3, AA type battery (5th battery / LR6 / AM3) diameter ф14.5; height 50.5mm.
4, AAA type battery (7th battery / LR03 / AM4) diameter ф10.5; height 44.5mm.
5, AA/2 type battery (8th battery LR1/AM5) diameter ф11.0; height 30.0mm.
6, AAAA type battery (9th battery / LR61 / AM6) diameter ф8.0; height 39.5mm.
7, AAAA / 2 type battery (small 9th battery / LR61 / AM6) diameter ф8.0; height 28.0mm.