Supervision system for monitoring the condition of a battery and a series-connected fuse

• US 4,563,628 A
• Filed: 08/24/1984
• Issued: 01/07/1986
• Est. Priority Date: 10/12/1982
• Status: Expired due to Term

• Current Assignee: ADT Security Services Incorporated (Apollo Global Management, Inc.)
• Original Assignee: Baker Industries, Inc. (Lincoln Electric Holdings Incorporated)
• Inventors: Wynne, John M., Tietz, Joseph G.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/643,950
• Time in Patent Office: 501 Days
• Field of Search: 320/48, 320/20, 320/21, 307/64, 307/66, 340/636
• US Class Current: 320/163
• CPC Class Codes: H02J 7/0029 with safety or protection devices or circuits
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems
• CPC Class Codes: Y10S 320/12 Precharging analysis, e.g. determining presence of battery
• CPC Class Codes: Y10S 320/13 Fault detection
• CPC Class Codes: Y10S 320/19 Charger status, e.g. voltmeter

Abstract

The condition of a rechargeable battery, which is employed as a backup d-c power supply for a load in the event of an emergency and is normally charged by a d-c charging voltage through a series-connected protective fuse, is monitored by momentarily reducing the charging voltage and effectively sensing or measuring the voltage across the series-connected fuse and battery during the momentary reduction, while not affecting the load. If the battery is connected and is functioning properly and if the fuse is connected and is continuous, the sensed voltage will exceed a predetermined desired threshold level, and this normal condition may be visually and/or audibly indicated. On the other hand, if the battery is disconnected, or if the battery voltage is abnormally low, or if the fuse is absent or is open, then the sensed voltage will fall below the desired threshold level, signifying a trouble condition. When such a condition is detected, a trouble indicator provides an appropriate visual and/or audible signal.

Claims

1. A battery and fuse supervision system for monitoring the condition of a rechargeable battery and a series-connected protective fuse to detect whether the battery is present and connected, whether the battery voltage is abnormally low, and whether the fuse is present and is effective, wherein the battery and fuse are connected, via a series-connected isolating diode, to a load to provide backup d-c power for the load in the event of a failure of a primary d-c power supply which normally applies to the load a d-c operating voltage greater than the battery voltage, thereby reverse biasing the isolating diode so that normally no load current flows from the battery, said supervision system comprising:

a voltage regulator having its input connected to the primary d-c power supply and having first and second series-connected output resistors across which resistors is provided a d-c charging voltage having an amplitude exceeding a predetermined reference level;

a sensing resistor shunt-connected across the series combination of the fuse and the battery;

a coupling circuit, including a series-connected isolating diode, for applying the d-c charging voltage from said voltage regulator to said sensing resistor and, through the fuse, to the battery to charge the battery normally to the charging voltage;

a solid state switch shunt-connected across said second output resistor of said voltage regulator;

means for periodically momentarily turning said solid state switch on to essentially short out said second output resistor in order to periodically momentarily reduce the charging voltage to a level below the reference level so that the voltage across said sensing resistor, during each momentary reduction, will normally be isolated from and not affected by the charging voltage and will be equal to and reflect the battery voltage, the time duration of each momentary reduction of the charging voltage being extremely small compared to the time interval between successive reductions,

wherein the voltage across said sensing resistor is relatively high when the charging voltage is at its normal magnitude and the battery is being charged and is also relatively high when the battery voltage is above the reference level, and the fuse is present and continuous, but the charging voltage is at its reduced magnitude;

and wherein the voltage across said sensing resistor is relatively low when the battery voltage is below the reference level, or the fuse is open or disconnected, at the same time that the charging voltage is at its reduced level;

a voltage comparator for comparing the voltage across said sensing resistor with a reference voltage, representing the reference level, to determine, during each momentary reduction of the charging voltage, whether the sensing resistor voltage is relatively high, thereby indicating that the battery voltage is above the reference level and that the fuse is connected and is continuous, or is relatively low, thereby signifying that the battery voltage is below the reference level or that the fuse is discontinuous or is disconnected;

and indicator means, controlled by said voltage comparator, for providing a trouble indication when the sensing resistor voltage is relatively low.