Charging device

A battery charging device comprising:

• a constant current source;
• a plurality of battery circuit lines for connecting each of a plurality of batteries, respectively, to the constant current source to be charged thereby;
• a plurality of switch circuits for controlling the supply of current from the constant current source to each of the respective battery circuit lines;
• a full-charge detection means for detecting upon connection to a battery a fully charged state of the battery;
• a short-circuit detection circuit for determining whether a battery is short-circuited by measuring voltage level at a connection terminal of the battery at a selected time after said constant current source is connected thereto;
• an over-discharged battery discrimination means for determining whether a battery is over-discharged on the basis of measurement of an initial voltage of the output of the constant current source immediately after connection of the battery thereto, a charging voltage below a preset threshold being recognized as determining that an over-discharged battery has been connected for charging;
• and means operated in accordance with said determination for setting a time of connection of said full-charge detection means to said battery to start detection of a fully-charged state of the battery to begin at a time later than a time at which said full-charge detection means is connected for detection of full-charge of a normally discharged battery, such that false detection of a charging condition of said over-discharged battery as a full-charge condition will be prevented;
• and
• a switching control circuit means for switching said battery circuit line switch circuits one after another to successively connect each of said plurality of batteries to said constant current source to be charged, said switching control circuit means operating upon detection of one of a battery fully charged state and a short-circuited battery condition.

A battery charging device comprising:

• a constant current source;
• a plurality of battery circuit lines for connecting each of a plurality of batteries, respectively, to the constant current source to be charged thereby;
• a plurality of switch circuits for controlling the supply of current from the constant current source to each of the respective battery circuit lines;
• a full-charge detection means for detecting upon connection to a battery a fully charged state of the battery;
• a short-circuit detection circuit for determining whether a battery is short-circuited by measuring voltage level at a connection terminal of the battery at a selected time after said constant current source is connected thereto;
• a series transistor connected in circuit between the constant current source and the battery circuit lines, and a reverse current detection circuit including a comparison circuit which compares terminal voltage of a battery with output voltage of the constant current source and operates to turn the series transistor to an off state when the terminal voltage of the battery is higher than the output voltage of the constant current source;
• and
• a switching control circuit means for switching said battery circuit line switch circuits one after another to successively connect each of said plurality of batteries to said constant current source to be charged, said switching control circuit means operating upon detection of one of a battery fully charged state and a short-circuited battery condition;
• wherein said short-circuit detection circuit includes a first short-circuit detection circuit which detects if the charging voltage reaches a first reference voltage within a first predetermined period of time, and a second short-circuit detection circuit which detects if the charging voltage reaches a second reference voltage, which is higher than said first reference voltage, within a second predetermined period of time which is longer than said first predetermined period of time.

A battery charging device comprising:

• a constant current source;
• a plurality of battery circuit lines for connecting each of a plurality of batteries, respectively, to the constant current source to be charged thereby;
• a plurality of switch circuits for controlling the supply of current from the constant current source to each of the respective battery circuit lines;
• a full-charge detection means for detecting upon connection to a battery a fully charged state of the battery;
• a short-circuit detection circuit for determining whether a battery is short-circuited by measuring voltage level at a connection terminal of the battery at a selected time after said constant current source is connected thereto;
• a switching control circuit means for switching said battery circuit line switch circuits one after another to successively connect each of said plurality of batteries to said constant current source to be charged, said switching control circuit means operating upon detection one of a battery fully charged state and a short-circuited battery condition;
• and
• a source voltage control circuit means for maintaining source voltage of the switching control circuit means when a battery connection terminal is short-circuited, including a series transistor connected in circuit between the constant current source and the battery circuit lines and a circuit including a control transistor connected to the series transistor and a Zener diode connected between the base of the control transistor and the constant current source to control the conducting condition of the series transistor in response to output voltage of the constant current source;
• wherein said short-circuit detection circuit includes a first short-circuit detection circuit which detects if the charging voltage reaches a first reference voltage within a first predetermined period of time, and a second short-circuit detection circuit which detects if the charging voltage reaches a second reference voltage, which is higher than said first reference voltage, within a second predetermined period of time which is longer than said first predetermined period of time.

A battery charging device comprising:

• a constant current source;
• a plurality of battery circuit lines for connecting each of a plurality of batteries, respectively, to the constant current source to be charged thereby;
• a plurality of switch circuits for controlling the supply of current from the constant current source to each of the respective battery circuit lines;
• a full-charge detection means for detecting upon connection to a battery a fully charged state of the battery;
• a short-circuit detection circuit for determining whether a battery is short-circuited by measuring voltage level at a connection terminal of the battery at a selected time after said constant current source is connected thereto;
• an over-discharged battery discrimination means for determining whether a battery is over-discharged on the basis of measurement of an initial voltage of the output of the constant current source immediately after connection of the battery thereto, and means operated in accordance with said determination for setting a time of connection of said full-charge detection means to said battery to start detection of a fully-charged state of the battery;
• and
• a switching control circuit means for switching said battery circuit line switch circuits one after another to successively connect each of said plurality of batteries to said constant current source to be charged, said switching control circuit means operating upon detection of one of a battery fully charged state and a short-circuited battery condition;
• wherein said short-circuit detection circuit includes a first short-circuit detection circuit which detects if the charging voltage reaches a first reference voltage within a first predetermined period of time, and a second short-circuit detection circuit which detects if the charging voltage reaches a second reference voltage, which is higher than said first reference voltage, within a second predetermined period of time which is long than said first predetermined period of time.