Rapid charging technique for lithium ion batteries

A method for charging a battery comprising the steps of:

• providing charging current to an external terminal of a battery through a first impedance, said first impedance being related to a series resistance between a current supplying terminal of a power supply and an electrode internal to said battery;
• detecting a voltage drop across said first impedance;
• generating a first voltage representative of a voltage at said electrode internal to said battery, said first voltage representing the voltage at said external terminal minus said voltage drop caused by said charging current through said first impedance;
• and
• applying said first voltage to a sense circuit for comparing said first voltage to a preset voltage to control said charging current to maintain said first voltage at approximately said preset voltage.

A method for charging a battery, said battery having external electrodes exposed through a housing of said battery and having internal electrodes in contact with an electrolyte, said method comprising the steps of:

• establishing a maintenance voltage determined to be a voltage at which the battery internal electrodes can be maintained without adversely affecting recharging of the battery;
• charging said battery through a first impedance so that said external electrodes are held at a voltage greater than said maintenance voltage, said first impedance being approximately equal to an electrical series resistance between said external electrodes and said internal electrodes;
• and
• terminating said charging of said battery after it has been determined that said battery has been sufficiently charged.

A battery charger comprising:

• a power supply having a charging current terminal;
• an impedance, related to an electrical series resistance of said battery, connected in series between said charging current terminal and an external battery terminal;
• a measuring circuit connected across said impedance for generating a first voltage representative of a voltage at an electrode internal to said battery, said first voltage representing the voltage at said external battery terminal minus a voltage drop caused by a charging current through said impedance;
• and
• a voltage sense circuit connected to an output of said measuring circuit for comparing said first voltage to a preset voltage and causing said charging current to maintain said first voltage at approximately said preset voltage.

A battery charger comprising:

• a power supply having a charging current terminal;
• an impedance connected in series between said charging current terminal and an external battery terminal, said impedance being approximately equal to an electrical series resistance between said external battery terminal and an electrode internal to said battery;
• a measuring circuit connected across said impedance for generating a first voltage representative of a voltage at said electrode internal to said battery, said first voltage being less than a voltage at said external battery terminal;
• and
• a voltage sense circuit connected to an output of said measuring circuit for comparing said first voltage to a preset voltage and causing said charging current to maintain said first voltage at approximately said preset voltage.