Apparatus to prevent complete battery discharge

• US 5,343,137 A
• Filed: 01/27/1993
• Issued: 08/30/1994
• Est. Priority Date: 01/28/1992
• Status: Expired due to Fees

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Kitaoka, Kazuhiro, Ito, Tsukasa, Takesue, Fumiki, Furuse, Akihiro
• Primary Examiner(s): KINCAID, KRISTINE LYNN
• Application Number:
  US08/009,635
• Time in Patent Office: 580 Days
• Field of Search: 320/5, 320/13, 320/31, 320/32, 320/37, 320/38, 320/39, 320/40, 307/10.7
• US Class Current: 320/132
• CPC Class Codes: H02H 3/006 Calibration or setting of parameters
• CPC Class Codes: H02H 5/041 additionally responsive to excess current H02H5/048 takes precedence
• CPC Class Codes: H02H 7/18 for batteries; for accumulators
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

To prevent the complete discharge of a battery connected to a load, a battery voltage of the battery is compared with a reference voltage, and a switch is activated to open an electrical connection between the battery and the load when the detected battery voltage falls below the reference voltage. To compensate for dynamic characteristics of the battery and the load, a battery current flowing through the battery is detected and a value of the reference voltage is continuously set according to the detected battery current. Similarly, a battery temperature of the battery also controls the reference voltage. Also, a timer may be provided to cause the switch to open the connection between the battery and the load only when the detected battery voltage remains below the reference voltage for a predetermined period of time.

Claims

1. An apparatus for preventing complete discharge of a battery electrically connected in series with a load, said apparatus comprising:

current detector means, connected in series with the battery, for detecting a battery current flowing through the battery;

voltage detector means, connected in parallel with the battery, for detecting a battery voltage of the battery;

switching means, connected between the load and the battery, for selectively closing and opening an electrical connection between the load and the battery; and

,

computation means for controlling said switching means in accordance with the battery current detected by said current detector means and the battery voltage detected by said voltage detector means;

wherein said computation means includes

(a) battery state detecting means for generating a reference voltage having a voltage level dependent on the battery current detected by said current detector means, said battery state detecting means responsive to said current detector means to decrease the reference voltage when the battery current increases and to increase the reference voltage when the battery current decreases,

(b) comparator means for comparing the reference voltage generated by said battery state detecting means with the battery voltage detected by said voltage detector means, and for generating a first output signal when the battery voltage detected by said voltage detector means becomes less than the reference voltage generated by said battery state detecting means, and

(c) timer means for detecting a discharge state in which the first output signal is generated by said comparator means for more than a predetermined time period, and for controlling said switching means to open the electrical connection between the load and the battery upon detecting the discharge state.

2. An apparatus for preventing complete discharge of a battery electrically connected in series with a load, said apparatus comprising:

current detector means, connected in series with the battery, for detecting a battery current flowing through the battery;

voltage detector means, connected in parallel with the battery, for detecting a battery voltage of the battery;

temperature detector means for detecting a battery temperature of the battery;

switching means, connected between the load and the battery, for selectively closing and opening an electrical connection between the load and the battery; and

,

computation means for controlling said switching means in accordance with the battery current detected by said current detector means, the battery voltage detected by said voltage detector means and the battery temperature detected by said temperature detector means;

wherein said computation means includes

(a) battery state detecting means for generating a reference voltage having a voltage level dependent on the battery current detected by said current detector means and the battery temperature detected by said temperature detector means, said battery state detecting means being responsive to said current detector means to decrease the reference voltage when the battery current increases and to increase the reference voltage when the battery current decreases, and being responsive to said temperature detector means to increase the reference voltage when the battery temperature increases and to decrease the reference voltage when the battery current decreases, and

(b) comparator means for comparing the reference voltage generated by said battery state detecting means with the battery voltage detected by said voltage detector means, and for generating a first output signal when the battery voltage detected by said voltage detector means becomes less than the reference voltage generated by said battery state detecting means, wherein said switching means is responsive to said first output signal to open the electrical connection between the load and the battery.

3. An apparatus as claimed in claim 2, wherein said computation means further includes timer means for detecting a discharge state in which the first output signal is generated by said comparator means for more than a predetermined time period, and for controlling said switching means to open the electrical connection between the load and the battery upon detecting the discharge state.