Rechargeable battery charging method and apparatus

• US 5,637,979 A
• Filed: 01/18/1996
• Issued: 06/10/1997
• Est. Priority Date: 08/27/1992
• Status: Expired due to Term

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Ohira, Takaharu, Tamai, Mikitaka
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US08/588,294
• Time in Patent Office: 509 Days
• Field of Search: 320/15, 320/17, 320/20, 320/23, 320/39, 320/6, 320/7, 320/18, 320/19
• US Class Current: 320/116
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A plurality of series connected rechargeable batteries are charged by detecting battery voltages and controlling charging current. Normal charging is performed until any one battery voltage reaches a prescribed voltage. After any one battery voltage reaches the prescribed voltage, all batteries are charged such that a charging current is controlled to keep each battery voltage from exceeding the prescribed voltage.

Claims

1. A rechargeable battery charging method comprising:

(a) effecting a first charging of a plurality of series connected rechargeable batteries, said first charging being a constant current charging,

(b) detecting a battery voltage of each one of said rechargeable batteries during said first charging, wherein said first charging is performed until the battery voltage of any one of the rechargeable batteries is detected as reaching a prescribed voltage, and

(c) after the battery voltage of any one of the rechargeable batteries reaches the prescribed voltage, effecting a second charging of the plurality of series connected rechargeable batteries by gradually reducing a battery charging current to maintain the battery voltage of said any one of the rechargeable batteries at the prescribed voltage and to gradually increase the battery voltage of each of the remaining rechargeable batteries without exceeding the prescribed voltage.

2. A rechargeable battery charging method as recited in claim 1, wherein said first and second chargings are effected to a plurality of series connected nonaqueous rechargeable batteries.

3. A rechargeable battery charging method as recited in claim 2, wherein said first and second chargings are effected to a plurality of series connected lithium ion rechargeable batteries.

4. A rechargeable battery charging method as recited in claim 1, wherein said plurality of series connected rechargeable batteries are contained within a battery pack which is detachably connectable to a battery charger, and wherein said method further comprises automatically detecting a total battery voltage of the rechargeable batteries in response to the battery pack being connected to the battery charger and then controlling charging to keep the total battery voltage from exceeding a prescribed total voltage.

5. A rechargeable battery charging apparatus comprising:

(a) a detection means for detecting a battery voltage of each one of a plurality of rechargeable batteries which are connected together in series, wherein said the detection means is a constant voltage charging circuit that prevents the battery voltage of each battery from exceeding the prescribed voltage, and

(b) a control means, responsive to said detection means, for charging the rechargeable batteries by gradually reducing a battery charging current to maintain the battery voltage of said any one of the rechargeable batteries at the prescribed voltage and to gradually increase the battery voltage of each of the remaining rechargeable batteries without exceeding the prescribed voltage when the battery voltage of said any one of the rechargeable batteries is detected as reaching the prescribed voltage, wherein said control means is a constant current charging circuit that control the battery charging current in accordance with a signal output from said constant voltage charging circuit.

6. A rechargeable battery charging apparatus as recited in claim 5, wherein said rechargeable battery charging apparatus is connected to a voltage detection terminal of a battery pack containing said rechargeable batteries and further includes means for controlling a current flowing into and out of said voltage detection terminal.

7. A rechargeable battery charging apparatus as recited in claim 6, wherein said battery charger includes an operational amplifier having an input connected to said rechargeable batteries and an output connected to said voltage detection terminal.

8. A rechargeable battery charging apparatus as recited in claim 6, wherein said battery charger includes a high resistance device connected between said rechargeable battery and said detection means.

9. A rechargeable battery charging apparatus as recited in claim 6, wherein said battery charger includes an operational amplifier and a high resistance device connected between said rechargeable battery and said detection means.

10. A rechargeable battery charging apparatus as recited in claim 5, wherein said constant voltage charging circuit includes operational amplifiers that respectively compare the battery voltage of each rechargeable battery with a reference voltage, and wherein outputs of the operational amplifiers control said constant current charging circuit.

11. A rechargeable battery charging apparatus as recited in claim 5, wherein said constant voltage charging circuit includes shunt regulator integrated circuits controlled by the battery voltage of each of the rechargeable batteries, and and wherein outputs of said shunt regulator integrated circuits control said constant current charging circuit.

12. A rechargeable battery charging apparatus as recited in claim 5, wherein

(a) said control means is a constant current charging circuit, and

(b) said detection means is said voltage detection circuit that detects the battery voltage of each of the rechargeable batteries and a micro-computer that processes an output from said voltage detection current and controls said constant current charging circuit.

13. A rechargeable battery charging apparatus as recited in claim 5, wherein said plurality of series connected rechargeable batteries are contained within a battery pack which is detachably connectable to a battery charger, and wherein said apparatus further comprises a second detection means for automatically detecting a total battery voltage of the rechargeable batteries in response to said battery pack being connected to said battery charger and a second control means for then controlling charging to keep the total battery voltage from exceeding a prescribed total voltage when said second detection means detects that the total battery voltage has reached the prescribed total voltage.

14. A rechargeable battery charging apparatus as recited in claim 13, wherein said control means and said second control means are a constant current charging circuit, wherein said detection means is a first constant voltage charging circuit, and wherein said second detection means is a second constant voltage charging circuit.