Abstract: A battery charging device providing both a rapid high charging rate and a trickle rate for a substantially fully charged battery and employing first, second and third rectifying circuits for rectifying an AC current into a DC current; a charging state switch circuit for outputting information about the charging-state switching of the battery between a high charging rate and a trickle charge rate; charging driving circuits for outputting a driving signal representing high speed charging or trickle charging in accordance with the output of the charging state switch circuit; a charging circuit for performing high speed charging or trickle charging in response to the driving signal; an auxiliary controlling circuit for controlling the battery to be charged with a regulating current during a rapid high charging rate; a battery mounting sensing circuit for sensing the mounting of a battery to be charged; a charging state indicating circuit for indicating a rapid high charging rate of the battery mounting sensing ci