Battery residual capacity displaying system with discharged electrical quantity computation section

• US 5,545,969 A
• Filed: 10/25/1993
• Issued: 08/13/1996
• Est. Priority Date: 12/02/1992
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Hasegawa, Hirokazu
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TSO, EDWARD H
• Application Number:
  US08/140,501
• Time in Patent Office: 1,023 Days
• Field of Search: 320/5, 320/31, 320/32, 320/35, 320/37, 320/39, 320/48, 324/426, 324/431, 324/433, 324/435, 340/635, 340/636
• US Class Current: 320/134
• CPC Class Codes: G01R 31/3646 for indicating electrical conditions or variables, e.g. visual or audible indicators
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current

Abstract

A system for displaying the residual capacity of a secondary battery so as to update the battery capacity when the battery discharges from its full charged condition to a predetermined voltage level, in which this predetermined voltage is selected to be sufficiently higher than the operation halting voltage of a portable electrical apparatus to be connected, and the quantity of electricity discharged until the predetermined voltage level is reached is suitably corrected to determine the newest battery capacity, so that the battery capacity can be accurately updated under the actual operating condition with a high frequency and high precision.

Claims

1. A system for displaying a residual capacity of a secondary battery, said system comprising:

a current detection resistor for converting a charging current and a discharge current of said secondary battery into very small voltages respectively;

charging and discharging current detection means, comprising a charging side operational amplifier and a discharge side operational amplifier, for amplifying the very small voltages appearing across said current detection resistor respectively to generate resultant signals and outputting the resultant signals respectively;

voltage drop detection means for detecting a situation where a voltage of said secondary battery has dropped to a level lower than a predetermined setting and outputting a voltage drop signal when said situation is detected;

temperature detection means for detecting an ambient temperature of said secondary battery to generate a temperature signal and outputting the temperature signal;

electrical quantity computation means, receiving the resultant signals of said charging and discharge current detection means together with the temperature signal of said temperature detection means as its inputs, for deciding whether an operation mode of said system is a charging mode, a discharge mode or a stand-by mode and computing a quantity of electricity in that mode;

charging completion detection means for producing an output signal and setting its output signal when completion of charging said secondary battery is detected, but resetting its output signal when charging said secondary battery is started;

discharged electrical quantity integration means for integrating the quantity of electricity at time intervals of a predetermined period to derive a first integrated value when the output signal of said charging completion detection means is set and a decision of said electrical quantity computation means indicates the discharge mode, but, when the output signal of said charging completion detection means is reset, nullifying the first integrated value irrespective of the decision of said electrical quantity computation means;

capacity memory means for storing the first integrated value integrated by said discharged electrical quantity integration means as a newest battery capacity when the output signal of said charging completion detection means is set and the voltage drop signal is first outputted from said voltage drop detection means after the charging is started;

electrical quantity integration means for obtaining a second integrated value by integrating, at time intervals of the predetermined period, the quantity of electricity by addition when the decision of said electrical quantity computation means indicates the charging mode, but by subtraction when the decision of said electrical quantity computation means indicates the discharge mode, thereby determining the residual capacity on the basis of a ratio of the second integrated value to the first integrated value stored in said capacity memory means, said electrical quantity integration means setting the second integrated value to correspond to the value of the residual capacity at the predetermined voltage level when the voltage drop signal is first outputted from said voltage drop detection means after the charging is started, but setting the second integrated value to correspond to the residual capacity of 100% when the output signal of said charging completion detection means is set as a result of the charging; and

display means for displaying the residual capacity stepwise on the basis of the value of the residual capacity determined by said electrical quantity integration means.

2. A battery residual capacity displaying system according to claim 1, wherein said electrical quantity computation means multiplies, when the detected mode is one of the charging mode and the discharge mode, one of the resultant signals by a predetermined period to compute the quantity of electricity and then multiplies the quantity of electricity by an efficiency determined by both the one of the resultant signals and the ambient temperature of said secondary battery to compute the final quantity of electricity, while when the detected mode is the stand-by mode, the electrical quantity computation means computes the quantity of electricity by selecting suitable temperature data meeting the detected temperature from among a plurality of temperature data prepared beforehand for each of a plurality of ambient temperatures and representing both a self-discharge quantity of electricity of said secondary battery and a quantity of electricity consumption by said battery residual capacity displaying system.

3. A battery residual capacity displaying system according to claim 1, wherein said display means comprises a display unit including a plurality of liquid crystal display segments energized or deenergized in response to application of an input signal.

4. A system for displaying a residual capacity of a secondary battery, said system comprising:

a current detection resistor for converting a charging current and a discharge current of said secondary battery into very small voltages respectively;

charging and discharge current detection means, comprising a charging side operational amplifier and a discharge side operational amplifier, for amplifying the very small voltages appearing across said current detection resistor respectively to generate resultant signals and outputting the resultant signals respectively;

residual capacity alarm means, receiving a terminal voltage of said secondary battery and one of the resultant signals corresponding to the discharge current as its inputs, for lowering battery voltage detection level in proportion to an increase in the discharge current and for generating an alarm signal irrespective of the discharge current when a predetermined setting of the residual capacity of said secondary battery is reached;

temperature detection means for detecting the ambient temperature of said secondary battery to produce a temperature signal and outputting the temperature signal;

electrical quantity computation means, receiving the resultant signals together with the temperature signal, for deciding whether an operation mode of the system is a charging mode, a discharge mode or a stand-by mode and computing a quantity of electricity in that mode;

charging completion detection means for producing an output signal and setting its output signal when completion of charging said secondary battery is detected, but resetting its output signal when charging said secondary battery is started;

discharged electrical quantity integration means for integrating the quantity of electricity at time intervals of a predetermined period to derive a first integrated value when the output signal of said charging completion detection means is set and a decision of said electrical quantity computation means indicates the discharge mode, but, when the output signal of said charging completion detection means is reset, nullifying the first integrated value irrespective of the decision of said electrical quantity computation means;

capacity memory means for storing a value obtained by dividing the first integrated value by a factor determined by a predetermined residual capacity alarm level of said residual capacity alarm means, which factor is 1-0.1 =0.9 when said predetermined setting of the residual capacity alarm level is 10%, as a newest battery capacity when the output signal of said charging completion detection means is set and the alarm signal is first generated from said residual capacity alarm means after the charging is started;

electrical quantity integration means for obtaining a second integrated value by integrating, at time intervals of the predetermined period, the quantity of electricity by addition when the decision of said electrical quantity computation means indicates the charging mode, but by subtraction when the decision of said electrical quantity computation means indicates the discharge mode, thereby determining the residual capacity on the basis of a ratio of the second integrated value to the first integrated value stored in said capacity memory means, said electrical quantity integration means setting the second integrated value to correspond to the value of the predetermined residual capacity when the alarm signal is first generated from said residual capacity alarm means after the charging is started, but setting the second integrated value to correspond to the residual capacity of 100% when the output signal of said charging completion detection means is set as a result of the charging; and

display means for displaying stepwise the residual capacity on the basis of the value of the residual capacity determined by said electrical quantity integration means.

5. A battery residual capacity displaying system according to claim 4, wherein said electrical quantity computation means multiplies, when the detected mode is one of the charging mode and the discharge mode, one of the resultant signals by a predetermined period to compute the quantity of electricity and then multiplies the quantity of electricity by an efficiency determined by both the one of the resultant signals and the ambient temperature of said secondary battery to compute the final quantity of electricity, while when the detected mode is the stand-by mode, the electrical quantity computation means computes the quantity of electricity by selecting suitable temperature data meeting the detected temperature from among a plurality of temperature data prepared beforehand for each of a plurality of ambient temperatures and representing both a self-discharge quantity of electricity of said secondary battery and a quantity of electricity consumption by said battery residual capacity displaying system.

6. A system for displaying a residual capacity of a secondary battery, said system comprising:

a current detection resistor for converting a charging current and a discharge current of said secondary battery into very small voltages respectively;

charging and discharge current detection means, comprising a charging side operational amplifier and a discharge side operational amplifier, for amplifying the very small voltages appearing across said current detection resistor respectively to generate resultant signals and outputting the resultant signals respectively;

residual capacity alarm means, receiving a terminal voltage of said secondary battery and one of the resultant signals corresponding to the discharge current as its inputs, for lowering battery voltage detection level in proportion to an increase in the discharge current and for generating an alarm signal irrespective of the discharge current when a predetermined setting of the residual capacity of said secondary battery is reached;

temperature detection means for detecting the ambient temperature of said secondary battery to produce a temperature signal and outputting the temperature signal;

electrical quantity computation means, receiving the resultant signal together with the temperature signal, for deciding whether an operation mode of the system is a charging mode, a discharge mode or a stand-by mode, and, when the detected mode is the discharge mode, multiplying one of the resultant signals corresponding to the discharge current by a predetermined period to compute a discharged quantity of electricity and then multiplying the discharged quantity of electricity by a discharge efficiency determined by both said one of the resultant signals and the ambient temperature of said secondary battery to compute a final quantity of electricity, while when the detected mode is the stand-by mode, computing a quantity of electricity by selecting suitable temperature data meeting the ambient temperature from among a plurality of data prepared beforehand for each of a plurality of ambient temperatures and representing both a self-discharge quantity of electricity of said secondary battery and a quantity of electrical consumption by said battery residual capacity displaying system;

charging completion detection means for producing an output signal and setting its output signal when completion of charging said secondary battery is detected, but resetting its output signal when charging said secondary battery is started;

discharged electrical quantity integration means for integrating the discharged quantity of electricity to obtain a first integrated value at time intervals of said predetermined period when the output signal of said charging completion detection means is in the set state, but nullifying the first integrated value when the output signal of said charging completion detection means is in the reset state;

capacity memory means for storing a value obtained by dividing the first integrated value by a factor determined by a predetermined residual capacity alarm level of said residual capacity alarm means, which factor is 1-0.1 =0.9 when said predetermined residual capacity alarm level is 10%, as a newest battery capacity when the output signal of said charging completion detection means is set and the alarm signal is first generated from said residual capacity alarm means after the charging is started;

capacity rating memory means for storing a rated capacity of said secondary battery;

capacity comparison means, receiving the value stored in said capacity memory means and the rated capacity stored in said capacity rating memory means for determining a degree of battery deterioration on the basis of a ratio of the value stored in said capacity memory means to the rated capacity; and

display means for displaying stepwise the degree of battery deterioration determined by said capacity comparison means.

7. A battery residual capacity displaying system according to claim 6, wherein the rated capacity stored in said capacity rating memory means is an initial capacity value of said secondary battery.