Method and apparatus for monitoring battery energy level

• US 3,899,732 A
• Filed: 08/16/1973
• Issued: 08/12/1975
• Est. Priority Date: 08/16/1973
• Status: Expired due to Term

• Current Assignee: BRK Brands Incorporated (Newell Brands Inc.)
• Original Assignee: Paul A. Staby
• Inventors: Staby, Paul A.
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Hille, Rolf
• Application Number:
  US05/388,975
• Time in Patent Office: 726 Days
• Field of Search: 324/29.5 340/237S,249,248B,248D
• US Class Current: 324/429
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/3646 for indicating electrical conditions or variables, e.g. visual or audible indicators
• CPC Class Codes: G01R 31/386 using test-loads
• CPC Class Codes: G08B 29/181 due to failing power supply

Abstract

A fire detection apparatus operates to self-monitor the energy level of a cell or battery powering it by periodically comparing a first signal, which is a function of the unloaded battery output voltage, with a second signal, which is a function of the battery output voltage when loaded, to generate a difference signal. The difference signal is characterized by only exceeding a predetermined magnitude whenever the energy stored in the battery is below a selected energy level and is used to indicate impending battery failure by driving a different alarm or the same alarm in a manner noticeably different from the alarm signal generated in response to the detection of a fire.

Claims

1. Battery operated detection apparatus comprising:

first and second electrical lead means for connection, respectively, to the positive and negative terminals of a battery power source;

battery powered means for sensing a selected condition and generating a first electrical output signal representative of said condition, said sensing means being connected between said electrical lead means to receive power therefrom whereby to be powered by the battery power source connected thereto;

battery powered alarm means connected between said first and second electrical leads to receive power therefrom whereby to be powered by the battery power source connected thereto, said alarm means being connected to said sensing means to receive said first electrical output signal and being operable to generate an output signal corresponding thereto;

means connected between said first and second electrical leads for periodically loading the battery power source connected thereto to subject it to momentary increased discharge current;

means for generating a first voltage signal having a magnitude equal to a selected proportion less than 100 percent of the output voltage of the battery power source prior to said loading;

means for generating a second voltage signal having a magnitude less than said first voltage signal and equal to the output voltage of the battery power source when loaded less a predetermined voltage drop; and

, means for comparing said first and second voltage signals and generating a second electrical output whenever their difference exceeds a predetermined magnitude, said difference only exceeding a predetermined magnitude whenever the energy stored in the battery power source is below a selected energy level, and alarm means being connected to receive said second output signal and being operable to generate an output signal corresponding thereto.

2. The invention defined in claim 1 wherein said alarm means is said batteRy powered alarm means.

3. The invention defined in claim 1 wherein said selected condition sensed by said sensing means is the conductivity of the atmosphere whereby fire may be detected by the presence of smoke and/or combustion products in the atmosphere.

4. The invention defined in claim 3 wherein said oscillator employs a programable unijunction transistor or equivalent.

5. The invention defined in claim 4 wherein a light emitting diode is employed to bias said oscillator into recycling so as to minimize the energy drain on the battery power source.

6. The invention defined in claim 1 wherein said means for generating said first voltage signal is a voltage divider circuit connected between said first and second electrical lead means.

7. The invention defined in claim 1 wherein said means for generating said second voltage signal is at least one diode connected in series with a resistor between said first and second electrical lead means, said second voltage signal being generated at the point of connection of said diode with said resistor.

8. The invention defined in claim 1 wherein said means for comparing said first and second voltage signals and generating said second output signal is a programable unijunction transistor means or equivalent.

9. The invention defined in claim 1 wherein:

said first output signal generated by said sensing means is generated as long as said selected condition is sensed;

said second output signal generated by said means for comparing said first and second voltage signals is a pulse of short duration; and

, said alarm means is responsive to provide a different alarm signal.

10. The invention defined in claim 1 wherein the means for periodically loading the battery power source draws less than 50 microamperes current therefrom.

11. The invention defined in claim 9 wherein said alarm means includes a silicon controlled rectifier and a sound generator, said silicon controlled rectifier having its anode-cathode current path connected in series with said sound generator and its gate electrode connected to receive said first and second output signals, said sound generator having automatically reclosing contacts which open when electrical current flows therethrough whereby a series of blasts of said generator are generated in response to said first output signal and said sound generator starts to turn on but immediately clicks off in response to said second output signal so as to generate an audible click.

12. A circuit arrangement for determining whether the energy in an electrical storage cell or battery exceeds a selected level, comprising:

means connected to the terminals of said battery for generating a first signal having a magnitude equal to a selected proportion less than 100 percent of the unloaded output voltage of said battery;

means connected to the terminals of said battery for periodically loading said battery to subject it to a momentary increased discharge current;

means connected to the terminals of said battery for generating a second signal having a magnitude less than said first signal and equal to the loaded output voltage of said battery less a predetermined value; and

, means for comparing said first and second signals and generating an output signal whenever their difference exceeds a predetermined magnitude, said difference only exceeding a predetermined magnitude whenever the energy stored in said battery is below said selected energy level.

13. A method for determining whether the energy in an electrical storage battery exceeds a selected level comprising the steps of:

sensing the output voltage of the battery under a selected load condition and generating a first voltage signal having a magnitude equal to a selected proportion thereof less than 100 percent;

periodically loading the battery to subject it to momentary increased discharge current and simultaneously sensing its output voltage;

generating a second voltage signal haviNg a magnitude less than said first voltage signal and equal to the output voltage of the loaded battery less a predetermined voltage drop; and

, generating a third voltage signal equal to the difference between said first and second voltage signals, said third voltage signal only exceeding a predetermined magnitude whenever the energy stored in the battery is below a selected energy level.

14. The invention defined in claim 1 wherein the means for periodically loading the battery power source draws less than 50 microamperes current therefrom.

15. Battery operated detection apparatus comprising:

first and second electrical lead means for connection, respectively, to the positive and negative terminals of a battery power source;

battery powered means for sensing a selected condition and generating a first electrical output signal representative of said condition, said sensing means being connected between said electrical lead means to receive power therefrom whereby to be powered by the battery power source connected thereto;

battery powered alarm means connected between said first and second electrical leads to receive power therefrom whereby to be powered by the battery power source connected thereto, said alarm means being connected to said sensing means to receive said first electrical output signal and being operable to generate an output signal corresponding thereto;

means connected between said first and second electrical leads for periodically loading the battery power source connected thereto to subject it to momentary increased discharge current, said means for periodically loading the battery power source being a free running oscillator;

means for generating a first voltage signal having a magnitude equal to a selected proportion less than 100 percent of the output voltage of the battery power source prior to said loading;

means for generating a second voltage signal having a magnitude less than said first voltage signal and equal to the output voltage of the battery power source when loaded less a predetermined voltage drop; and

, means for comparing said first and second voltage signals and generating a second electrical output whenever their difference exceeds a predetermined magnitude, said difference only exceeding a predetermined magnitude whenever the energy stored in the battery power source is below a selected energy level, and alarm means being connected to receive said second output signal and being operable to generate an output signal corresponding thereto.