

As a general rule, the model number contains two capital letters and four digits as shown in the example (variations may be encoiuntered). This numbering system is supported by the Japan International Standard Committee of Clocks and Watches and is an established practice in Japan.
BK - 80AAAB
BK - Nickel Metal Hydride battery
80- multiply this number by 10 to obtain the rated capacity (some exceptions)
AAA - diameter: AAA, AA
B - cap shape: button top type