Abstract:
A usage counter has input terminals connectable to the terminals of a jump-starting battery pack. The counter has an IC comparator which generates an output signal when battery voltage drops below a predetermined reference level. If the output signal persists for a predetermined time period, indicating an attempt to jump-start an engine with the battery pack, an IC timer is triggered to output a count pulse which is inverted and then counted and displayed by an IC counter/display circuit. The usage counter circuit is powered by the battery pack and has a Zener diode which provides to the IC circuits a limited supply voltage which is unaffected by voltage spikes which might appear at the battery pack terminals. A capacitor maintains the reference voltage level despite momentary drops in battery terminal voltage.

Description:
RELATED APPLICATION 
     This application claims the benefit of the filing date of copending U.S. provisional application No. 60/175,363, filed Jan. 10, 2000. 
    
    
     BACKGROUND 
     This application relates to battery or power packs of the rechargeable type and, in particular, to lead-acid, thin metal film battery packs. The application relates in particular to determining the cycle life of lead-acid battery packs for uses, such as jump-starting automotive vehicles. 
     It is known to provide battery packs, i.e., compact arrangements of one or more cells, for various DC power delivery applications. One such application is for use in jump-starting automotive vehicles. Such battery packs typically use lead-acid batteries, some of which have recently been of the thin metal film type. Such thin metal film lead-acid batteries are sold, for example, by Johnson Controls, Inc. under the designation “Inspira” and by Bolder Technologies under the designation “Bolder 9/5 Sub-C TMF” (Thin Metal Film). 
     It is desirable to provide a simple apparatus for determining the practical cycle life of jump-starting battery packs, particularly during development of prototype units, in terms of the number of usage cycles, such as jump starts or jump start attempts, which can be effected by the unit. 
     SUMMARY 
     This application discloses an improved test and monitoring circuit for use with jump-starting battery packs. 
     An important aspect is the provision of a circuit for monitoring the number of vehicle start attempts performed by a portable jump-starting battery unit. 
     Another aspect is the provision of a circuit of the type set forth, which detects automotive jump-starting attempts with minimal current draw. 
     Still another aspect is the provision of a circuit of the type set forth, which is of simple and economical construction. 
     In particular, there is provided an apparatus for determining the cycle life of a battery in terms of usage cycles, comprising a reference circuit adapted to be coupled to the battery and establishing a reference voltage level, a usage cycle detection circuit adapted to be coupled to the battery and to the reference circuit and generating a count signal in response to battery voltage dropping below the reference voltage level, and a counter circuit coupled to the detection circuit for counting the number of count signals generated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     For the purpose of facilitating an understanding of the subject matter sought to be protected, there is illustrated in the accompanying drawing an embodiment thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated. 
     The FIGURE is a schematic circuit diagram of a usage counter circuit connected to a battery pack. 
    
    
     DETAILED DESCRIPTION 
     Referring to the FIGURE, there is illustrated a usage counter circuit, generally designated by the numeral  10 , having input terminals  11  and  12  which are adapted to be connected, respectively, to the terminals of a battery pack  15 , which has a terminal voltage V B . The battery pack  15  is typically of a type used for jump-starting automotive vehicles and may be of the thin metal film, lead-acid type. In a constructional model, the counter circuit  10  is adapted to be used with a battery pack having a storage battery of the type sold by Johnson Controls, Inc. under the trade name “Inspira” and rated at 2.4 ampere-hours. However, it will be appreciated that the circuit  10  could be used with other types of portable jump-starting battery pack units. 
     Connected in a series across the input terminals  11 ,  12  are a resistor  16  and a Zener diode  17 , for producing at the cathode of the Zener diode  17  a limited supply voltage V+. 
     The usage counter circuit  10  has a voltage comparator  20 , which includes a reference circuit, described below, and an integrated-circuit (“IC”) comparator  21  having supply terminals connected across the V+supply. The comparator  21  may be a CMOS comparator with open collector output, such as a TLC372, and has an output connected through a pull-up resistor  21   a  to the V+supply. Resistors  22 ,  23 ,  24  and  25  are connected in series across the terminals  11 ,  12 , the junction between the resistor  24  and  25  being connected to the inverting input terminal of the IC  21  to provide a reference voltage. The junction between the resistors  23  and  24  is connected to ground through a capacitor  26 , which causes the reference voltage to be unresponsive to transient battery voltage changes, such as those caused by attempts to start a vehicle. Resistors  27  and  28  are connected in series across the terminals  11 ,  12  and form a voltage divider which provides, at the junction therebetween, a comparison voltage connected to the non-inverting input terminal of the IC  21 , which comparison voltage is instantaneously responsive to battery voltage changes. The junction between the resistors  22  and  23  is connected to the cathode of a Zener diode  29 , the anode of which is connected to ground. The Zener diode  29  cooperates with the resistors  22 - 25  and the capacitor  26  to form the reference circuit. 
     The output of the comparator  20  at the output of the IC  21  is connected to a delayed trigger circuit  30 , which includes a CMOS IC timer  31 . More specifically, the output of the IC  21  is coupled through a resistor  32  to the trigger terminal of the timer  31 , the resistor  32  being connected in parallel with a diode  33  having its anode connected to the output of the IC  21 . The trigger terminal is also connected through a capacitor  34  to the V+supply. A resistor  35  and a capacitor  36  are connected in series across the V+supply, the junction therebetween being connected to threshold and discharge terminals of the timer  31 . A control terminal of the timer  31  is connected through a capacitor  37  to ground. The VCC and reset terminals of the timer  31  are connected to the V+supply. 
     The output of the timer  31  is coupled to an inverter  40 , which includes an NPN transistor  41 . More specifically, the output of the timer  31  is coupled through a resistor  42  to the base of the transistor  41 , the collector of which is connected with a resistor  43  to the V+supply, and the emitter of which is connected to ground. The output of the inverter  40 , at the collector of the transistor  41 , is coupled to the input terminal of an IC counter/display  45 , the positive supply terminal of which is connected to the cathode of a diode  44 , the anode of which is connected to the V+supply, the negative supply terminal of the counter/display  45  being connected to ground. A capacitor  46  is connected across the supply terminals of the counter/display  45 . The reset terminal of the counter/display  45  is connected through a resistor  47  to ground. The positive supply terminal of the counter/display  45  is connected to a terminal  48 , and a terminal  49  is connected to the reset terminal of the counter/display  45 . 
     In operation, the usage counter circuit  10  will recognize an appreciable drop in battery voltage, such as is caused by an attempt to jump-start an automotive vehicle, and will increment the number on the display by one. In this regard, the comparator IC  21 , the delayed trigger circuit  30  and the inverter  40  cooperate to function as a usage cycle detection circuit. When the battery pack  15  is in a non-used state, the voltage at the non-inverting input of the comparator IC  21  is slightly higher than the reference voltage at the inverting input terminal, and the output of the IC  21  is high, preferably about 12 volts. When the battery pack  15  is loaded by a vehicle starter, the voltage at the non-inverting input terminal of the IC  21  drops below the reference voltage and the output of the IC  21  goes low. This condition continues until the load is removed (the car starts or the starter is disengaged), allowing the battery voltage to rise, or until the capacitor  26  discharges (preferably after about 10 seconds), causing the reference voltage to drop below the comparison voltage. 
     In normal use, it is possible for the battery pack to experience instantaneous voltage drops caused by touching the battery leads together, connecting to a light load or the like. Such voltage drops would typically have a duration less than about one-tenth of a second. The delayed trigger  30  causes such instantaneous voltage drops to be ignored by the timer  31 . More specifically, the timer  31  is designed to provide a count pulse each time the voltage at its trigger input drops below one-third of the VCC voltage. The capacitor  36  and the resistor  35  establish a pulse duration of preferably about one second, and the capacitor  37  adds stability to the timer. The resistor  32  and the capacitor  34  form an RC delay, such that when the voltage at the output of the comparator IC  21  goes low (to about zero volts), it takes at least 500 ms. for the timer trigger voltage to drop below one-third VCC. However, when the output of the timer IC  21  goes high, the diode  33  allows current to bypass the resistor  32 , causing the trigger voltage of the timer  31  to rise immediately. If an undesirable instantaneous voltage drop, such as described above, occurs, the timer trigger voltage will not drop below one-third VCC before rising and a count pulse will not be generated by the timer  31 . Only if the battery voltage drops for at least 500 ms., will a count pulse be produced. 
     The timer  31  produces an active low count pulse at its output, which is inverted by the inverter  40  to a high pulse, which is recognized by the counter/display  45 . The counter/display is a totalizer with an LCD display and is incremented by one count with each input count pulse. The resistor  46  grounds the reset terminal of the counter/display  45 , while allowing the user to reset the counter/display  45  by shorting the reset pin to the V+supply across the terminals  48  and  49 . An appropriate reset switch button or the like (not shown) may be provided for this purpose. 
     When a battery pack successfully starts a vehicle, the vehicle&#39;s charging system will bring the battery pack voltage back up above its resting voltage of about 13 volts. To prevent a second count from occurring when the battery pack is removed from the running vehicle (allowing its voltage to drop to its resting level), the Zener diode  29  prevents the reference voltage from rising above its normal or reset level, thereby preventing a “double” count. 
     Voltage spikes can occur while connecting the battery pack  15  to, or disconnecting it from, a load. In order to protect the sensitive CMOS integrated circuits  21  and  31  from such voltage spikes, the Zener diode  17 , which may be rated at 16 volts, prevents the V+supply voltage from rising above that level. The resistor  16  limits current through the diode  17  when the battery pack voltage exceeds the Zener voltage. 
     The counter/display  45  is normally powered through the diode  44 . However, if the battery voltage drops below a pre-determined level, such as about 5 volts, the operation of the counter/display  45  may become erratic. In such an event, power is supplied from the high-value capacitor  46  to keep the counter/display  45  active for at least 30 seconds. 
     In a constructional model of the invention, the capacitors  26  and  34  may be 1 microfarad, the capacitors  36  and  37  may be 0.1 microfarad, the capacitor  46  may be 1000 microfarads, the Zener diode  29  may be a 13-volt, 1N4700, the Zener diode  17  may be a 16-volt 1N5246, the diode  33  may be an 1N914, the diode  44  may be an IN  4002 , the IC timer  31  may be a TLC555, the transistor  41  may be a 2N3904, the counter/display IC  45  may be Curtis 17082-112, the resistor  16  may be 100 Kohm, the resistor  21   a  may be 10 Kohm, the resistors  22 - 25  may, respectively be 1 Kohm, 12 Mohm, 8.2 Mohm and 18 Mohm, the resistors  27 ,  28  and  35  may be 10 Mohm, the resistor  32  may be 430 Kohm, and the resistors  42 ,  43  and  46  may be 4.7 Kohm. With these component values, the usage counter circuit  10  draws less than one milliampere. 
     Accordingly, it can be seen that there has been provided a usage counter circuit which provides a simple means of counting the number of vehicles start attempts made using a jump-start battery pack, while placing a negligible additional load on the battery pack. 
     The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While a particular embodiment has been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants&#39; contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.