Battery unit having a plurality of rechargeable battery cells and method of charging the same

• US 6,121,752 A
• Filed: 01/28/2000
• Issued: 09/19/2000
• Est. Priority Date: 11/21/1997
• Status: Expired due to Term

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kitahara, Jun, Takeoka, Hitoshi, Miyata, Junichi, Saitou, Kenichi, Ishii, Masato
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/493,237
• Time in Patent Office: 235 Days
• Field of Search: 320/116, 320/118, 320/119, 320/121, 320/122
• US Class Current: 320/122
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery assembly unit and a method of charging the same for applying constant current/constant voltage charging to a battery assembly in which a plurality of battery cell groups each having battery cells each being rechargeable and increasable in electromotive force as charging proceeds are connected in series. There are provided a reference charging voltage circuit for generating charging reference voltages serving as voltages referenced to electromotive force levels of the individual battery cell groups on the basis of charging voltage applied across the battery assembly and changeable with time, and comparison circuits each adapted to compare an electromotive force level across each of the plurality of battery cell groups connected in series with the charging reference voltage. Further, bypass circuits are provided each of which connected in parallel across each of the plurality of battery cell groups connected in series and when an electromotive force of a battery cell group exceeds the charging reference voltage, bypasses the charging current by an amount corresponding to a difference.

Claims

1. A battery assembly in which a plurality of battery cell groups each having battery cells each being rechargeable are connected in series, comprising:

a reference charging voltage circuit for generating reference voltages serving as voltages referenced to a potential difference across the individual battery cell groups on the basis of a charging voltage applied across said battery assembly;

and

bypass means being connected in parallel across terminals of said plurality of battery cell groups connected in series and, when the potential difference across each battery cell group reaches said charging reference voltage, being operative to bypass charging current due to said charging voltage applied across said battery assembly by an amount conforming to a difference.

2. A battery assembly unit according to claim 1, wherein said reference charging voltage circuit is connected in parallel across said battery assembly to divide said charging voltage applied across said battery assembly by the number of said battery cell groups connected in series to generate said reference voltage.

3. A battery assembly unit according to claim 1 further comprising a bypass current control circuit, wherein, when the potential difference across the battery assembly reaches the charging end voltage, said bypass current control circuit performs bypass control of the charging current in conformity with constant voltage charging.

4. A battery assembly unit according to claim 1 further comprising a charge/discharge discriminative circuit adapted to detect discharging operation of the battery assembly to deliver a discharge discriminative signal to said bypass means, wherein, when receiving said discharging discriminative signal, said bypass means releases the bypass operation of the charging current.

5. A battery assembly unit according to claim 1, wherein said bypass means includes comparison means for comparing a potential difference across each battery cell and said reference voltage, and said bypass means bypasses said charging current when said potential difference across each battery cell exceeds said reference voltage.

6. A battery assembly unit in which a plurality of battery cell groups each having battery cells each being rechargeable and increasable in electromotive force as charging proceeds are connected in series, comprising:

charging interruption means connected in series with one polarity of each battery cell group of said battery assembly;

bypass interruption means connected in parallel with each battery cell group of said battery assembly;

a reference voltage source for generating a charging end voltage of said battery cell group as a charging end reference voltage;

comparison circuits each being connected in parallel across each of said battery cell groups constituting said battery assembly to compare a potential difference across each battery cell group with the charging end reference voltage of said reference voltage source and being operative to deliver a charging end voltage detection signal for each battery cell group when the potential difference across each battery cell group reaches the charging end voltage; and

a charging circuit configuration control sequence circuit for receiving the charging end voltage detection signal for each battery cell group from said comparison circuit and delivering a control signal which opens said charging interruption means and closes said bypass interruption means associated with a battery cell reaching the charging end voltage and further delivers to an external power supply a charging voltage designating signal which instructs a charging voltage conforming to the number of battery cells excepting the battery cell reaching said charging end voltage.

7. A battery assembly unit according to claim 6 further comprising, on the battery assembly charging current applying side, charging protective means capable of interrupting charging current and discharging current, wherein said charging circuit configuration control sequence circuit responds to said charging end voltage detection signal to transmit a charging stop signal to said charging protective means so as to temporarily stop the charging current, thereby opening and closing said charging interruption means and said bypass interruption means, respectively, associated with the battery cell group reaching said charging end voltage and thereafter causing said charging protective means to restart conduction of the charging current.

8. A battery assembly unit charging method for applying charging to a battery assembly in which a plurality of battery cell groups each having battery cells each being rechargeable and connected in series, comprising the steps of:

detecting a potential difference across each battery cell group;

generating reference charging voltages for the individual battery cell groups from a charging voltage that it is applied across said battery assembly;

comparing the potential difference across each battery cell group with said reference voltage; and

bypassing charging current for a battery cell having a potential difference in excess of said reference voltage in accordance with a difference from said reference voltage.

9. A battery assembly unit charging method for according to claim 8, wherein said reference voltages are generated by dividing the charging voltage applied to said battery assembly by the number of battery cell groups.

10. A battery assembly unit charging method according to claim 8, wherein when the potential difference across a battery cell group reaches a predetermined charging end voltage, charging current for that battery cell group is completely bypassed.

11. A charging current control circuit for applying charging to a battery assembly in which a plurality of battery cell groups each having battery cells and each being rechargeable are connected in series, comprising:

a reference charging voltage circuit for generating charging reference voltages serving as voltages referenced to a potential difference across the individual battery cell groups on the basis of a charging voltage applied across said battery assembly; and

bypass means connected in parallel across terminals of each of said plurality of battery cell groups connected in series and, when the potential difference across each battery cell group exceeds said reference voltage, being operative to bypass charging current due to said charging voltage applied across said battery assembly by an amount conforming to the potential difference.

12. A battery assembly unit charging method for applying charging to a battery assembly in a plurality of battery cell groups each having battery cells each being rechargeable and connected in series, comprising the steps of:

measuring a potential difference across each battery cell group;

generating a reference voltage corresponding to a charging end voltage;

comparing the potential difference across each battery cell group with said reference voltage;

separating a battery cell group reaching said reference voltage from said series connection; and

performing charging at a charging voltage conforming to the number of remaining battery cell groups.