Where did the classification of No. 1, No. 2, No. 5 and No. 7 batteries come from?

The so-called battery sizes are sorted by numbers in decreasing order of volume and numbered in sequence. They have no special meaning.

According to the GB/T 8897.1-2013 primary battery standard, battery specifications are defined in the name of the National Electrotechnical Commission (IEC) specification.

For example, R20, R6 and R03 represent traditional numbering methods such as No. 1, No. 5 and No. 7 respectively.

However, due to user habits, numbering methods such as No. 1, No. 5 and No. 7 are still retained in the product names.

The R in the R series battery model represents a round single cell, and this letter, together with the number that follows, indicates the nominal size of the battery.

Battery No. 1, the national standard model is R20, the English code is D, the diameter is 34.2mm, and the height is 61.5mm.

No. 2 battery, the national standard model is R14, the English code is C, the diameter is ф26.2mm; the height is 50.0mm.

AA battery, national standard model is R6, English code is AA, diameter ф14.5mm; height 50.5mm.

No. 7 battery, the national standard model is R03, the English code is AAA, the diameter is ф10.5mm; the height is 44.5mm.