Device and method for charging a secondary battery

A method for charging a secondary battery, using a voltage measuring circuit for measuring a terminal voltage of said secondary battery, a current control circuit for controlling a charging current fed through said secondary battery, and an abnormality determining portion, and comprising steps of:

• starting the charging of said secondary battery;
• comparing said terminal voltage with a first threshold value which is decided based on a predetermined normal-state upper limit of the intemal resistance and the charging current of said secondary battery;
• finishing said charging when said terminal voltage has reached said first threshold value;
• measuring an open-circuit voltage of said secondary battery after finishing said charging;
• and
• determining that said secondary battery is abnormal when said open-circuit voltage is less than a second threshold value.

A device for charging a secondary battery, comprising:

• a voltage measuring circuit measuring a terminal voltage of said secondary battery;
• a current control circuit controlling a charging current fed to said secondary battery;
• and
• an abnormality determining portion which:
• starts a preliminary charging of said secondary battery, finishes said preliminary charging when
• compares said terminal voltage with a first threshold value which is decided based on a predetermined normal-state upper limit of the internal resistance and the charging current of said secondary battery,
• finishes said preliminary charging when said terminal voltage has reached said first threshold value;
• measures the open-circuit voltage of said secondary battery after finishing said preliminary charging, and
• determines that said secondary battery is abnormal when said open-circuit voltage is less than a second threshold value.

A method, for charging a secondary battery, using a voltage measuring circuit for measuring a terminal voltage of said secondary battery, a current control circuit for controlling a charging current fed through said secondary battery, and an abnormality determining portion, and comprising steps of:

• starting the preliminary charging of said secondary battery;
• comparing said terminal voltage with a first threshold value which is decided based on a predetermined normal-state upper limit of the internal resistance and the charging current of said secondary battery;
• finishing said preliminary charging when said terminal voltage has reached said first threshold value;
• measuring a open-circuit voltage of said secondary battery after finishing said preliminary charging;
• and
• determining that said secondary battery is abnormal when said open-circuit voltage is less than a second threshold value.