Patent ID: 7764048

Claim:
A method of charging a rechargeable battery including a bare cell and a charging component through which current can flow to charge the bare cell, the method comprising: determining a charge state of the bare cell across terminals of the bare cell; and controlling a charging current flowing through the charging component to be at a first relatively low level during a pre-charging phase and at a second higher level during a charging phase, in dependence on the determined charge state, with the step of controlling the charging current flowing through the charging component comprising the steps of: electrically connecting a charging field effect transistor between a terminal of the bare cell and a terminal of a charger, with the charging field effect transistor comprising a drain electrode electrically connected to the terminal of the bare cell, a source electrode electrically connected to the terminal of the charger, and a gate electrode; controlling a duty ratio of a pulse width modulation signal generated by a pulse generating device; filtering the alternating voltage of the pulse width modulation signal; and applying the filtered signal to the source electrode of the charging field effect transistor to control the amount of charging current flowing from the source electrode to the drain electrode of the charging field effect transistor.