Temperature responsive battery charging circuit

• US 3,895,283 A
• Filed: 11/26/1973
• Issued: 07/15/1975
• Est. Priority Date: 11/26/1973
• Status: Expired due to Term

• Current Assignee: Bruce E. Peterson
• Original Assignee: Bruce E. Peterson
• Inventors: Peterson, Bruce E.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/419,116
• Time in Patent Office: 596 Days
• Field of Search: 320/35,36,68,64,39,40,31,32,61 323/75H 322/28
• US Class Current: 322/33
• CPC Class Codes: H02J 2310/44 for aircrafts
• CPC Class Codes: H02J 7/007192 in response to temperature
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: H02J 7/16 Regulation of the charging current or voltage by variation of field
• CPC Class Codes: H02J 7/32 for charging batteries from a charging set comprising a non-electric prime mover rotating at constant speed
• CPC Class Codes: Y10S 320/33 Aircraft or spacecraft application

Abstract

A battery charging circuit for use in aircraft wherein a voltage-regulated alternator is employed to maintain a nickel cadmium battery charged. A temperature-dependent resistance element thermally coupled to the battery provides a reference voltage against which battery terminal voltage is compared. When the terminal voltage falls below the reference voltage application of sensing voltage to the alternator voltage regulator is interrupted, causing full charging current to be applied to the battery. When the terminal voltage exceeds the reference voltage, sensing voltage is reapplied to reduce charging current. The alternator switches between maximum and minimum charging efforts to maintain a voltage level dictated by the battery temperature.

Claims

1. In an electrical system of the type having a nickel cadmium battery, a source of unidirectional charging current, and a voltage regulator for controlling the output voltage of said source of unidirectional current in accordance with an applied sensing voltage related to the voltage level of said system, said voltage regulator causing said current source to operate at a predetermined maximum voltage level in the absense of said applied sensing voltage and at lesser voltage levels in the presence of said applied sensing voltage, a battery charge control and thermal runaway protection circuit comprising, in combination:

temperature sensing means including a sensor in thermal communication with said battery for generating a temperaturedependent reference signal; and

battery charge control Means responsive to said reference signal and to the terminal voltage of said battery for terminating the application of sensing voltage to said voltage regulator for maximum charging effort when the terminal voltage of said battery falls below a predetermined level dependent on the temperature of said battery, and for applying sensing voltage to said regulator for reduced charging effort when the terminal voltage of said battery exceeds said predetermined level.

2. A battery charge control and thermal runaway protection circuit as defined in claim 1 wherein said source of unidirectional charging current comprises a generator including a field winding, and wherein said voltage regulator controls the application of excitation current to said field winding to maintain the voltage level of said system constant.

3. A battery charge control and thermal runaway protection circuit as defined in claim 1 wherein said battery charge control means comprise a comparison amplifier for effecting a comparison between at least a portion of said battery terminal voltage and said temperature-dependent reference signal, and switch means responsive to the output of said comparison amplifier for controlling application of sensing voltage to said voltage regulator.

4. A battery charge control and thermal runaway protection circuit as defined in claim 1 wherein said temperature sensing means further comprise a constant-voltage source, a bridge circuit coupled between said constant-voltage source and ground, and a first differential amplifier having its input terminals coupled across the center of said bridge, and wherein said temperature sensor comprises a temperature-dependent resistance included in one leg of said bridge to produce a temperature-dependent reference output signal from said amplifier.

5. A battery charge control and thermal runaway protection circuit as defined in claim 4 wherein said temperature-dependent resistance has a positive temperature coefficient, and wherein said reference signal varies inversely with temperature.

6. A battery charge control and thermal runaway protection circuit as defined in claim 3 wherein the application of sensing voltage to said regulator is terminated when said portion of said battery terminal voltage falls below said reference voltage, and re-established when said portion of said battery terminal voltage rises above said reference voltage.

7. A battery charge control and thermal runaway protection circuit as defined in claim 4 wherein said battery charge control means comprise a second differential amplifier having a first input terminal coupled to the output of said first differential amplifier, and a second input terminal coupled to the terminals of said battery.

8. In an electrical system of the type having a nickel cadmium battery, a source of unidirectional charging current, and a voltage regulator for controlling the output voltage of said source of unidirectional current in accordance with an applied sensing voltage related to the voltage level of said system, a charge control and thermal runaway protection circuit comprising, in combination:

temperature sensing means including a sensor in thermal communication with said battery for generating a temperature-dependent reference signal; and

battery charge control means responsive to said reference signal and to the terminal voltage of said battery for selectively terminating the application of sensing voltage to said voltage regulator according to the terminal voltage and temperature of said battery to reduce the potential for thermal runaway in said battery while maintaining said battery fully charged.

9. A battery charge control and thermal runaway protection circuit as defined in claim 8 wherein said source of unidirectional charging current comprises a generator including a field winding, and wherein said voltage regulator controls the application of excitation current to said field winding to maintain the voltage level of said system constant.

10. A battery charge control and thermal runaway protection circuit as defined in claim 8 wherein the application of sensing voltage to said regulator is terminated when said battery terminal voltage exceeds said reference voltage, and re-established when said battery terminal voltage falls below said reference voltage.