Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
  • G01R19/10—Measuring sum, difference or ratio
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
  • G01R19/0038—Circuits for comparing several input signals and for indicating the result of this comparison, e.g. equal, different, greater, smaller (comparing pulses or pulse trains according to amplitude)
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
  • G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
  • G01R31/3835—Arrangements for monitoring battery or accumulator variables, e.g. SoC involving only voltage measurements

Definitions

• the present invention relates to a method for measuring the state of charge of an accumulator subjected to high transient consumption, by measuring a temporary drop in voltage across its terminals, and a device for implementing this. process.
• FIG. 1 is a diagram representing the variation of this no-load voltage, at the terminals of the accumulator as a function of the state of discharge of this accumulator.
• a third method consists in measuring the dynamic resistance of the accumulator: this method is used when the accumulator delivers on a payload which cannot be disconnected; the dynamic resistance of the accumulator is evaluated by connecting an additional auxiliary charge for a short time, producing an additional current flow and a voltage drop across the terminals of the accumulator, the measurement of which enables this resistance to be calculated.
• the auxiliary load is connected for a short time time to avoid unnecessary discharge of the battery.
• Experimental studies have made it possible to determine a limit value of this resistance from which the accumulator should be recharged. These last two methods have the advantage of being relatively simple and quick to implement, but do not make it possible to give a sufficient indication when one wants to know sufficiently long in advance that the accumulator is reaching the end of discharge. .
• this accumulator when used to power a device with high transient consumption at start-up such as an electric motor causing a charge with high inertia and / or high friction at start-up, in particular for the launching of a combustion engine internal, it is necessary to know whether the accumulator can still perform at least one engine start. However, when the voltmeter of the second method indicates that point A or A 'of the diagram has been reached, it is already too late and there is a good chance that the motor can no longer be started.
• the appreciable variation in the dynamic resistance of the accumulator does not occur until one has reached the vicinity of point A or A 'of the diagram, and the third method does not make it possible to predict sufficiently long in advance the end of discharge of the accumulator in the case of its application when starting an electric motor.
• the discharge is sometimes slow, sometimes rapid, and we progressively pass from the first curve to the second curve of FIG. 1.
• These phenomena are non-linear, so that their forecasting is not possible by simply measuring linear effects such as dynamic resistance o On the contrary, we must integrate the nonlinear phenomena accompanying high-value transient discharges.
• An electric motor is used to simplify the description, any type of load with high transient consumption at start-up, the start-up consumption representing a large fraction of the capacity of the accumulator.
• An object of the present invention is to propose a method for measuring the state of charge of an accumulator making it possible to indicate sufficiently long in advance the need for recharging. of the accumulator.
• the method makes it possible to know that the accumulator will have to be recharged but that an engine can still be started one or more times.
• Another object of the present invention is to provide a device allowing the implementation of this method, by measuring the maximum temporary voltage drop across the terminals of the accumulator when the engine starts.
• Another object of the present invention is to provide a circuit which is both simple and economical for carrying out these measurements.
• the method of measuring the state of charge of an accumulator consists in memorizing the voltage at the terminals of the accumulator before the connection of the electric motor, to be detected after each connection from the motor the maximum temporary voltage drop across the accumulator terminals, to be stored and to display the result of this detection. The comparison of this maximum voltage drop value with a reference value allows the user to appreciate the need to recharge the accumulator.
• This measurement method makes it possible, unlike the known methods, to integrate all the non-linear phenomena producing a voltage drop during the operation of the accumulator on the payload for which it is intended.
• the process of The present invention makes it possible, unlike known methods, to take into account, in a simple and effective manner, the actual intensity delivered in the charge, and non-linear phenomena accompanying the flow of a large fraction of the capacity of the accumulator to each start-up to forecast its residual capacity; the method thus makes it possible to obtain a sufficiently reliable and long forecast in the case of a flow rate on an electric motor, which is an essentially variable load.
• maximum voltage drop must be understood as the voltage drop from which transient parasitic phenomena such as suroscilla- have been eliminated. tionc, due in particular to the inductive nature of electric motors.
• the device for measuring the state of charge of an accumulator comprises means for detecting and storing maximum voltage drop and display means for viewing the result of the detection or the result of the comparison of this detection with a reference signal.
• the means for viewing the result of the detection which carry out a storage of continuous or analog type, allow the operator to interpret the results in order to assess the need for recharging, in particular by integrating temperature forecasts, for example meteorological forecasts, which may influence the future behavior of the load.
• the means for detecting and memorizing the maximum voltage drop comprises a first maximum detector circuit for detecting and memorizing the maximum voltage of the accumulator, a subtractor circuit for effecting the difference between this maximum voltage and the instantaneous voltage of the accumulator, and a second maximum detector circuit for detecting and memorizing the maximum of this difference: a low-pass filter eliminates transient parasitic oscillations from the instantaneous voltage of the accumulator.
• the present invention provides a device allowing the monitoring of the state of charge of an accumulator by combination of the above method of measuring maximum voltage drop when connecting an electric motor to the terminals of the accumulator, and the method of measuring the no-load voltage of the accumulator.
• the device also comprises means for measuring the no-load voltage of the accumulator and means for shifting zero and inversion to allow the display of the result of this measurement using the same display means. than the first process.
• - Figure 1 is intended to illustrate the method for evaluating the state of charge of an accumulator by measuring the no-load voltage
• - Figure 2 shows waveforms to illustrate the measurement method according to the present invention
• FIG. 2 represents a time diagram of the voltage at the terminals of the accumulator during the measurement.
• the accumulator is first of all empty, the current output being substantially zero.
• the voltage at its terminals is at a high and constant level represented by the bearing P.
• the electric motor is connected to the terminals of the accumulator which then delivers a current.
• This causes a voltage drop across the terminals of the accumulator, represented by the descent B of the curve.
• the current flow decreases, and the motor may be disconnected.
• the voltage gradually rises from the minimiam C to a level Q substantially at the same level as the level P.
• the minimum C reached depends on the current supplied by the accumulator and on the state of charge thereof.
• the curve in solid lines in solid lines
• Curve 21 represents a form of voltage drop for an insufficiently charged accumulator, according to the same flow conditions, the minimum of the curve being less than the minimum admissible voltage shown by the dotted line a.
• Curve 22 represents the voltage drop for an accumulator whose charge becomes almost insufficient, the minimum being inside a voltage zone known as the dangerous zone represented between the dotted lines a and bo
• the method according to the present invention consists detecting and measuring the voltage of this minimum, and displaying the result so as to cause the battery to recharge as soon as this minimum reaches the danger zone.
• FIG. 3 schematically represents the circuit used for the implementation of this method: between the positive terminal 31 and the negative terminal 32 of the accumulator 30 are connected on the one hand the load impedance constituted by the motor 40 in series with an interrupter 34 and on the other hand a circuit for detecting a maximum voltage drop.
• the method according to the present invention consists in detecting the maximum voltage drop across the terminals of the accumulator on each closing of the switch 34 allowing the engine 40 to start.
• the electric motor 40 is shown in the figure mechanically coupled with a motor. internal combustion engine 41.
• the electric motor is used as the starter of the internal combustion engine.
• the device of the present invention performs a measurement which lasts during the entire start-up phase of the engine, the area of rise of the voltage curve represented in FIG. 2 having a shape which depends on various physical parameters such as than the inertia of the combustion engine or its temperature.
• the minimum voltage of zone C depends only on the electrical parameters of the charge impedance and the state of the accumulator, this state being a function of the current supplied to the motor.
• FIG. 3 schematically shows an embodiment of the maximum voltage drop detector according to the present invention.
• This detector comprises, for displaying the measurement result, a voltmeter 42, one terminal of which is connected to the negative terminal of the accumulator 30, and the other terminal of which is connected to the output terminal of a circuit 43, the usual function of which is known by the name of "maximum detector".
• the input terminal of the maximum detector 43 is connected to the output terminal of a circuit 44 whose usual function is known by the name of "subtractor", of which a first input terminal, called inverting, is connected to the positive terminal of the accx-emulator 30 by means of a low-pass filter 45, and of which a second input terminal, known as a non-inverting terminal, is connected to the output terminal of a second maximum detector 46.
• the input terminal of this second maximum detector 46 is connected to terminal 31 of the accumulator.
• the two detectors of ma-H-rm ⁇ have the following function: when a variable voltage is applied to their input terminal, the voltage at their output terminal is equal to the maximum reached by the input voltage. This output voltage is memorized by the circuit and remains substantially constant for a predetermined time.
• the function of circuit 44 is to produce on its output terminal a voltage equal to the sum of the voltage present at its non-inverting input terminal and the opposite of the voltage present at its inverting input terminal. This circuit therefore makes the difference between these two voltages.
• the filter 45 is a low-pass filter intended to avoid taking too sudden variations in the input voltage due to rapid variations in the impedance of the motor 40.
• the device further comprises a switching means 47 for selectively switching the voltmeter 42 sometimes on the output terminal of the detector 43 and sometimes on the output terminal of a shaping circuit 48 whose input terminal is connected to terminal 31 of the accumulator.
• the first function of the shaping circuit 4S is to invert the instantaneous voltage measured across the terminals of the accumulator 30, and the second function is to shift the voltage obtained by a constant value to allow the use of the voltmeter 42 according to the two measurement modes, the needle of the voltmeter moving in the same ranges delimiting a zone of good functioning, a dangerous zone, and a zone of bad functioning.
• FIG 4 there is shown an embodiment of the circuit according to the present invention, taking the main elements of the circuit of Figure 3 and giving an embodiment of the different elements: filter, maximum detector, subtractor, switch and circuit formatting.
• the voltmeter 42 has a first terminal connected to the negative terminal 32 of the accumulator, which we will call in the following reference terminal, and a second terminal connected to the output terminal of the switching means 47.
• the switching means 47 has an input terminal connected to the output terminal of a first operational amplifier 60, the inverting input terminal of which is connected to its output terminal.
• the non-inverting input terminal of the amplifier 60 is connected to the reference terminal 32 via a resistor 61 and a capacitor 62 connected in parallel, and to the cathode of a diode 64 whose l the anode is connected to the output terminal of a second operational amplifier 63.
• the inverting input terminal of the amplifier 63 is connected to the inverting input terminal of the amplifier 60 via a resistor 65, and to the output terminal of the amplifier 63 via a resistor 66, and to the terminal 31 of the accumulator via a resistor 68, and to the reference terminal 32 by through a capacitor 67.
• the non-inverting input terminal of amplifier 63 is connected to the output terminal of a third operational amplifier 70 whose inverting input terminal is connected on the one hand to its output terminal and secondly to the inverting input terminal a fourth operational amplifier 73 via a resistor 76
• the non-inverting input terminal of the amplifier 70 is connected to the reference terminal 32 via a resistor 71 and a capacitor 72 connected in parallel, and to the cathode of a diode 74, the anode of which is connected to the output terminal of the amplifier 73 ”
• the inverting input terminal of the amplifier 73 is further connected to its terminal output via a resistor 75.
• the non-inverting input terminal of the amplifier 73 is connected to the reference terminal 32 via a resistor 77 and to the terminal 31 of the accumulator by through a resistor 78.
• the switching means 47 has the function of selectively switching its output terminal with one of its two input terminals.
• the second input terminal of the switch 47 is connected to the output terminal of an operational amplifier 80 whose inverting input terminal is connected to the terminal 31 of the accumulator via a resistor 84 and to the output terminal of amplifier 80 via a resistor 31.
• the non-inverting input terminal of amplifier 80 is connected on the one hand to terminal 31 of the accumulator via a resistor 83 and on the other hand to the cathode of a Zener diode 82 whose anode is connected to the reference terminal 32.
• the switch 47 can be synchronized with the start-up, in particular by detecting the voltage difference at the input and at the output of the storage means 46. In FIG.
• the first maximum detector 43 comprises the operational amplifiers 60 and 63, the resistor 61, the capacitor 62 and the diode 64.
• the second maximum detector 46 comprises the same elements , namely the amplifiers 70 and 73, the resistor 71, the capacitor 72 and the diode 74.
• the subtraction function of the circuit 44 is carried out, in this embodiment, by all of the elements of the detector 43.
• the filter 45 includes the capacitor 67 and the resistor 68.
• the shaping circuit 48 includes the amplifier 80, the resistors 81, 83 and 84 and the Zener diode 82.
• resistors 68 and 78 with the same value, and resistors 65 and 77 with the same value.
• resistor 68 and 78 with the same value
• resistors 65 and 77 with the same value.
• resistor 68 and 78 with a value five to ten times greater than the value of resistor 65, so that the input and output voltages of the amplifiers remain small compared to the supply voltage.
• the operating precision of the assembly is guaranteed up to very low supply voltages supplied by the accumulator.
• the maximum detector 46 supplies on its output terminal a voltage equal to a fraction of the voltage at the terminals of the accumulator, fraction determined by resistors 77 and 78.
• the second maximum detector 43 detects no voltage difference between the output terminal of the first detector 46 and terminal 31 of the accumulator, so that its output terminal provides zero voltage taking into account the choice of the values of resistors 65, 68, 77 and 78 mentioned above.
• the switching means 47 connects the voltmeter 42 with the output terminal of the amplifier 60, the voltmeter indicates a zero voltage, its needle being placed in a range 90 of the dial indicating a sufficient charge of the accumulator.
• the diode 64 is reverse biased, and prevents the discharge of the capacitor 62, so that the output terminal of the amplifier 60 supplies a voltage equal to the drop in voltage ⁇ iaximale of the accumulator, during the time of discharge of the capacitor 62 in the resistor 61.
• the setting is thus carried out in memory, for a certain time, of the maximum voltage drop of the accumulator.
• the needle of the voltmeter 42 indicates the value of this maximum voltage drop, and, if this is large, the needle of the voltmeter can penetrate an area 91 of the dial, known as the danger zone.
• the time constant of the circuit formed by the capacitor 72 and the resistor 71 is chosen so that the voltage drop at the output of the amplifier 70 during the course of the test is negligible, but that the memory storage circuit 46 follows slow variations in battery voltage.
• the time constant of the circuit formed by the capacitor 62 and the resistor 61 is chosen to be long enough to allow the operator to read the transient loss of voltage from the accumulator.
• the device of the present invention also makes it possible to monitor the state of charge of the accumulator in the absence of starting the engine 40.
• the switching means 47 connects the voltmeter 42 with the output of the setting means. shape 48.
• This shaping means makes it possible to produce a zero suppression voltmeter, the direction of deviation of which has been chosen so as to be compatible with that of the maximum detector described above.
• the needle of the voltmeter reaches zone 91, while when this voltage is higher, the needle remains in zone 90.
• Voltmeter 42 can be of analog type and include marks to define the dangerous range and the range of good operation.
• the voltage drop detected by the device described above is compared with one or more reference voltages by a comparator, not shown in the figures, the signal supplied by the comparator being transmitted in binary form to one or more indicator lights or to a generator of sound signals to warn the user of the need to recharge the accumulator.
• the present invention is very generally applicable to the measurement of the state of charge of all types of accumulators, the voltage of which decreases as the discharge progresses, and in particular of lead accumulators and of cadmium nickel accumulators.
• the invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof contained in the field of claims below.

Applications Claiming Priority (2)

Publications (1)

Family

ID=9237602

Family Applications (1)

Country Status (7)

Families Citing this family (8)

Family Cites Families (4)

• 1980
  • 1980-01-14 FR FR8000951A patent/FR2473730A1/fr active Granted
• 1981
  • 1981-01-12 WO PCT/FR1981/000004 patent/WO1981002066A1/fr not_active Application Discontinuation
  • 1981-01-12 JP JP50041381A patent/JPS56501897A/ja active Pending
  • 1981-01-12 EP EP81900209A patent/EP0044318A1/de not_active Ceased
  • 1981-01-12 US US06/300,127 patent/US4453129A/en not_active Expired - Fee Related
  • 1981-01-12 IT IT03305/81A patent/IT1221092B/it active
  • 1981-01-14 ES ES499257A patent/ES8201737A1/es not_active Expired

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events