With its great public transport system, Japan is one of the world's truly personally mobile cultures. There are portable gadgets of all kinds, not least of which include cell phones and music players. Have you ever wondered just how many batteries are needed annually to feed this mobility? We decided to check, and apparently Japanese consumers own more than 100m cell phones and 200m+ personal entertainment and information devices. As a result, they consume about 4.6bn batteries worth JPY700bn (US$5.98bn) yearly, of which about 78% are primary (disposable) batteries.