JP2018189606A - Device and method for evaluating battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for evaluating a battery that are highly resistant to noise and can easily measure such battery states of a storage battery as the internal resistance during or immediately after discharge (conduction) or during or immediately after charge (conduction) without relaying on currents.SOLUTION: A load is provided so that a current is flown from a chemical battery. The switch is connected to between the chemical battery and the load so that a discharge current from the chemical battery can be interrupted. A measuring circuit is provided to be capable of measuring a battery current and a battery voltage of the chemical battery. The measurement circuit measures a transient phenomenon before or after when the discharge current is blocked by the battery voltage, and can measure the internal resistance of the chemical battery from the ratio between the battery voltage difference and the discharge current before or after the interruption of the measured discharge current.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a battery evaluation device and a battery evaluation method.

  Conventionally, a chemical battery that can store electricity and can be used as a battery, in particular, it can be used as a battery by storing electricity by charging, and it is easy to evaluate the state of a battery called a secondary battery or storage battery that can be used repeatedly. And precise technology is required. For example, in a lead storage battery which is a typical chemical battery, the battery state is often represented by the equivalent circuit of FIG. 1 including the influence of the electric double layer in the battery. An electromotive force and internal resistance are important factors in determining battery deterioration. However, a measurement method necessary for managing a state of charge with a small error has not yet been established.

There are roughly the following three methods for measuring the internal resistance of lead-acid batteries and the like.
(1) The conductance method is a method in which an alternating current signal is passed through a battery cell and unit at a specific frequency to measure a current response between terminals.
(2) The impedance method is a method of taking a current from a battery at a specific frequency and measuring the voltage drop of the cell and unit. Discharge for 1/1000 to 1/2 second, and calculate the internal resistance (= impedance) from Ohm's law from the voltage drop measured at that time. This is the method used by most battery testers.
(3) The resistance method (load measurement method) is a method in which a load is applied to a cell and a unit to measure changes in voltage and current, and is adopted in an analog load tester or the like.

  The internal resistance of the storage battery is low, and these require measurement in consideration of the influence of the electric double layer. In order to measure accurately, the measurement time becomes long and careful noise countermeasures are required. In particular, in the resistance method, the load on the storage battery may be a problem. For the purpose of solving such problems, the first current control unit / backflow prevention diode and the second current control unit / backflow prevention diode are provided in series in a closed circuit in pairs in the forward direction and the reverse direction. A storage battery diagnostic device has been proposed (see Patent Document 1).

Japanese Patent No. 4372624

  The present invention makes it possible to easily measure the battery state such as the internal resistance of the storage battery during or after discharge (energization) or immediately after charging or during or immediately after charging without depending on the discharge (energization) current, and is resistant to noise. An object is to provide an evaluation device and a battery evaluation method.

  In order to achieve the above object, a battery evaluation apparatus according to a first aspect of the present invention is a battery evaluation apparatus for measuring an internal resistance of a chemical battery, and includes a load provided to flow a current from the chemical battery, A switch connected between the chemical battery and the load so as to cut off a discharge current from the chemical battery; and a measurement circuit provided to measure a battery current and a battery voltage of the chemical battery. The measurement circuit measures a transient phenomenon before and after the interruption of the discharge current with a battery voltage, and determines the internal resistance of the chemical battery from the ratio of the measured battery voltage difference before and after the interruption of the discharge current and the discharge current. It is comprised so that measurement is possible.

  A battery evaluation apparatus according to a second aspect of the present invention is a battery evaluation apparatus for measuring an internal resistance of a secondary battery, the charger provided so as to be able to charge the secondary battery, the secondary battery, and the charging A switch connected to the battery so as to cut off a charging current to the secondary battery, and a measurement circuit provided to measure a battery current and a battery voltage of the secondary battery, and the measurement The circuit measures a transient phenomenon before and after the interruption of the charging current by a battery voltage, and measures an internal resistance of the secondary battery from a ratio of the measured battery voltage difference before and after the interruption of the charging current and the charging current. It is configured to be possible.

  In the battery evaluation apparatus according to the first and second aspects of the present invention, it is preferable that the measurement circuit is configured to block a direct current and remove a high frequency region that becomes a noise source when measuring a battery voltage. . The switch may comprise a transient current switch circuit.

  The battery evaluation method according to the first aspect of the present invention is a battery evaluation method for measuring and evaluating the internal resistance of a chemical battery, wherein a load is connected to the chemical battery to pass a current and the discharge current is cut off. The transient phenomenon before and after the interruption of the battery is measured by the battery voltage, the internal resistance of the chemical battery is measured from the ratio of the battery voltage difference before and after the interruption of the discharge current and the discharge current, and based on the measured internal resistance The chemical battery is evaluated.

  The battery evaluation method according to the second aspect of the present invention is a battery evaluation method for measuring and evaluating the internal resistance of a secondary battery, and charging the secondary battery by connecting a charger to the secondary battery, The transient phenomenon before and after the interruption when the charging current is interrupted is measured by the battery voltage, and the internal resistance of the secondary battery is measured from the ratio of the charging voltage and the battery voltage difference before and after the interruption of the charging current, The secondary battery is evaluated based on the measured internal resistance.

  According to the present invention, the battery state such as the internal resistance of the storage battery can be easily measured without depending on the discharge (energization) current during or immediately after discharge (energization) or during or immediately after charging. A strong battery evaluation apparatus and a battery evaluation method can be provided.

  Further, according to the present invention, it is possible to measure the battery state such as the internal resistance of the storage battery by using a general-purpose current / voltage measuring device without using a special power source or load device. Furthermore, the internal resistance of the battery can be measured by short-time current interruption during discharge (energization) or current-voltage measurement immediately after discharge. The internal resistance corresponding to the battery electromotive voltage can be measured. The internal resistance of the battery can be measured by short-time current interruption during charging or current-voltage measurement immediately after charging. It is possible to measure noise-resistant internal resistance without being greatly affected by ion migration caused by an electric double layer in the battery.

It is a circuit diagram which shows the equivalent circuit of a storage battery. It is a circuit diagram which shows the equivalent circuit of the storage battery for transients at the time of an electric current interruption. (A) The circuit diagram of the measurement circuit for measuring the current voltage of the transient phenomenon at the time of battery current interruption of the battery evaluation device of the embodiment of the present invention, (b) at the time of current interruption measured by (a) It is the graph which shows the measurement waveform of a battery current and a battery voltage, (c) The graph which expanded the time axis | shaft of (b). It is a circuit diagram of the transient current switch circuit of the battery evaluation apparatus of the embodiment of the present invention. (A) When the transient current switch circuit shown in FIG. 4 is applied to the battery evaluation apparatus shown in FIG. 3 (a), (b) the battery at the time of current interruption when the transient current switch circuit shown in FIG. 4 is not applied It is a graph which shows the measurement waveform of an electric current and a battery voltage. In the battery evaluation apparatus shown in FIG. 3 (a), (a) battery current and AC and DC battery voltage measurement waveforms, (b) battery current at current interruption and AC and DC battery voltage measurement waveforms. It is a graph to show. (A) A circuit diagram of a measurement circuit for measuring a current voltage of a transient phenomenon during charging in the battery evaluation device according to the embodiment of the present invention; (b) a battery current at the start of charging measured by (a); And a graph showing the measured waveform of the battery voltage, (c) a graph showing the measured waveform of the battery current and the battery voltage at the end of charging, measured by (a). The battery evaluation circuit shown in FIG. 7 (a) (a) battery current at the end of charging and AC and DC battery voltage measurement waveforms, (b) battery current at the end of discharging and AC and DC battery voltage It is a graph which shows a measurement waveform. It is a graph which shows the internal resistance measured by changing discharge current with the battery evaluation circuit shown to Fig.3 (a). It is a graph which shows the relationship between the discharge time of a storage battery, the return voltage, and internal resistance obtained by the battery evaluation circuit shown to Fig.3 (a). It is a graph which shows the relationship between the discharge time of a storage battery, the specific gravity of an electrolysis solution, and internal resistance obtained by the battery evaluation circuit shown to Fig.3 (a). It is a graph which shows the relationship between the charging time of a storage battery, the return voltage, and internal resistance obtained by the battery evaluation circuit shown to Fig.7 (a). The graph which shows the measurement waveform of the battery current and battery voltage at the time of the current interruption in the lithium ion battery obtained by the battery evaluation circuit shown in FIG. 3A, and is a graph in which the time axis of FIG. is there. It is a graph which shows the change of the discharge resistance measured by the discharge current and the electromotive voltage, and the transient phenomenon with respect to the discharge time of the lithium ion battery obtained by the battery evaluation circuit shown to Fig.3 (a).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Measurement method of battery internal resistance focusing on battery voltage transient phenomenon when battery current is interrupted]
As shown in FIG. 1, the equivalent circuit of the storage battery is composed of an equivalent circuit of an internal resistance and an electric double layer. The presence of the electric double layer makes it difficult to observe the internal state of the battery. Therefore, attention is paid to the transient phenomenon at the time of current interruption. FIG. 2 shows an equivalent circuit of the current-voltage characteristics before the electric current is suddenly interrupted at the time of charging or discharging and the electric charge is accumulated in the electric double layer capacitor. The electric double layer in a chemical battery also depends on the behavior of ions and causes a time delay with respect to current interruption. The battery voltage is observed as a transient phenomenon centered on a phenomenon determined by the movement of electrons in the battery, such as an oxidation-reduction reaction.

  FIG. 3 is an explanatory diagram regarding the derivation of the internal resistance by measuring the transient phenomenon. As shown in FIG. 3A, the measurement circuit includes a battery, a switch, and a load circuit, and measures a battery (load) current and a contact voltage. FIGS. 3B and 3C show an overall view of measurement waveforms of the battery current and the battery voltage, and an enlarged view of the time axis corresponding to the transient phenomenon. In addition, the storage battery used for the experiment is a 12V lead storage battery for automobiles, and the 5-hour current rate is equivalent to 28 Ah. In the battery voltage measurement, direct current measurement and alternating current measurement (bandwidth 10 MHz) were shown. From these, the internal resistance in the equivalent circuit of FIG. 2 can be estimated.

[Application of transient current switch circuit to battery current interruption]
Mechanical switches and relays are convenient for opening and closing the current from the battery. However, when the current is interrupted, an unstable current interrupting phenomenon such as a bridge phenomenon or an arc discharge phenomenon often occurs. In order to avoid this, application of a transient current switch circuit is advantageous. When the current is interrupted by the transient current switch circuit, the current of the switch that interrupts the current is interrupted when the current is interrupted, but the current of the energizing circuit continues to flow as the charging current of the capacitor. In the switch part, the current can be cut off in a time when the voltage change is small. The battery current decreases gently with a time constant determined by the capacitor and load resistance. As a result, a sudden increase in the surge voltage of the load or the distribution circuit can be suppressed, and a bridge phenomenon or arc discharge at a mechanical switching contact can be suppressed. Since the transient phenomenon at the time of current interruption after energization of the storage battery can be controlled, the battery voltage as the transient phenomenon can be measured stably.

  FIG. 4 is a diagram for explaining the operating principle of the transient current switch circuit (TCS circuit). As shown in FIG. 5A, the transient current switch circuit stably shuts off the battery current with a time constant determined by the load resistance and the capacitor capacity of the transient current switch circuit. In addition, the storage battery used for the experiment is a 12V storage battery for automobiles, and the 5-hour current rate is equivalent to 28 Ah. FIG. 5B shows a response example when the discharge current is cut off by a mechanical switch without applying the transient current switch circuit, and unstable current cut-off and noise remarkably appear. Even if the applied switch is a semiconductor switch such as a MOSFET, the same effect can be obtained for surge voltage and noise suppression.

[Measurement with an AC circuit that blocks the DC signal component and applies a filter to the high frequency range that becomes a noise source in the measurement of the transient phenomenon of the battery voltage]
When observing the battery voltage as a transient phenomenon, in order to remove the DC component and further eliminate noise, “AC measurement” is performed in combination with a high-frequency cutoff filter. When charged normally and used normally, the battery voltage difference between energization and current interruption is small. By taking out a transient phenomenon as an AC measurement, an amplifier adapted to the bandwidth can be applied, so that the S / N ratio can be improved. FIG. 6 shows the validity of transient voltage measurement by AC measurement under the same conditions as in FIG. However, this is a comparison between DC voltage measurement and AC voltage measurement in a transient phenomenon immediately after interruption of the discharge current under the condition that the battery is consumed. A condition that allows comparison within the same voltage range is when the internal resistance is relatively large. DC measurement is for an input resistance of 1 MΩ, and AC measurement is for an input resistance of 1 MΩ and a bandwidth of 10 MHz.

[Measurement of internal resistance due to current interruption during charging of storage battery]
FIG. 2 shows an equivalent circuit of a storage battery. When a battery and a load, and a battery and a charging power source are connected, a phenomenon such as an electric double layer is removed, and at the same time, this equivalent circuit can be considered to be reversible. The internal resistance of the same equivalent circuit can be obtained from the voltage difference before and after the current during charging is cut off. FIG. 7 shows a specific example of a battery voltage / current measurement circuit at the start and end of charging (at the time of current interruption). The current is in the opposite direction to that during discharge shown in FIG. The charging power supply voltage is set to 13V, the current after stabilization is 1.3A, and the return voltage is 12.8V. In FIG. 8, the measurement result of the internal resistance measured by the charging current immediately after the completion of charging is compared with the measurement result of the internal resistance measured by the discharge current immediately after that. Both showed almost the same value.

[Measurement of internal resistance independent of discharge current during discharge]
FIG. 9 shows the internal resistance values measured by changing the load resistance during discharge. Internal resistance measurement independent of load current is possible. This suggests that a special electronic load device or the like is unnecessary and measurement is possible with a discharge current at an actual load. Measurement at the end of load energization (discharge state) is possible in a normal operation state.

[Simultaneous measurement of both battery voltage and internal resistance simultaneously]
When the discharge continues, the internal resistance increases and the electromotive voltage (return voltage) decreases. Although the change in the electromotive voltage is small, the change in the internal resistance is large compared to that and shows a stable numerical value, so that it is easier to estimate the state of the storage battery. FIG. 10 shows an example of measurement of electromotive voltage (return voltage) and internal resistance with respect to discharge time. The black line in the figure is three times the initial internal resistance. It may be said to be a value indicating the storage battery life.

[Measures specific gravity and internal resistance of electrolyte simultaneously]
Since the measurement time is short, the specific gravity and internal resistance of the electrolyte can be measured along the way while continuing the discharge. FIG. 11 shows an example of the measurement. Specific gravity was measured with a general-purpose hydrometer for batteries. Both correspond well. The specific gravity value has been frequently used for battery life prediction.

[Measurement of internal resistance during storage battery charging]
The internal resistance can be measured by instantaneous current interruption during the charging period. An example of the measurement is shown in FIG. In the figure, measured values of internal resistance due to discharges performed before and after charging are entered, which are equal to the measurement results of charging current at the start and end of charging. By charging, the internal resistance decreased from 16.6 mΩ to 11 mΩ. During that time, the electromotive voltage slightly increased from 12V to 12.5V. During the charging period, the current was momentarily interrupted to measure the internal resistance. Since measurement during such charging is possible, overcharge can be prevented.

[Application to lithium-ion batteries]
The measurement of the internal resistance focusing on the transient response at the time of current interruption can be applied not only to the lead storage battery but also to other batteries. FIG. 13 shows a measurement example using a lithium ion secondary battery. This is discharge when a load of 5Ω is connected to a battery with an electromotive voltage of 38V. The measurement circuit is the same as that shown in FIG. As with lead batteries, the internal resistance can be measured. A similar technique can be used to measure the discharge of a dry battery. FIG. 14 shows changes in discharge resistance measured by the discharge current / electromotive voltage and transient phenomenon with respect to the discharge time of the lithium ion battery.

[Combination with digital technology]
In the measurement of current voltage, the waveform was observed with a general-purpose synchroscope type measurement. Practically, a dedicated current / voltage measurement circuit and digital memory are combined, and a digital signal of the required time is extracted and compared. This is a technical field where microcomputer technology can be easily applied.

According to the battery evaluation apparatus and the battery evaluation method of the embodiment of the present invention, the following can also be realized.
(1) Estimation of residual power during discharge.
For example, as shown in FIG. 10, the remaining usable power can be estimated by measuring the relationship between the initial internal resistance of the battery and the power consumption in advance and then measuring the change in the internal resistance. Also, the residual power and the time required for charging can be predicted based on the absolute value of the internal resistance, the slope of the change, and the correspondence between the measurement result of the hydrometer and the internal resistance.

(2) Prevention of overcharge by measuring internal resistance during charging The internal resistance of a battery can be measured by a simple technique of interrupting the circuit during charging for a short time.

(3) Detection of irreversible resistance increase In addition to the reversible resistance that can be restored by charging, the internal resistance includes parts due to lead sulfate crystallization and electrode wear and tear. It can be a basis for such prediction and judgment of failure and functional degradation. That is, it is possible to provide estimated data on the disposal time.

  The battery evaluation apparatus and the battery evaluation method according to the present invention can construct a system that enables estimation of usable residual power in the use of a storage battery. Further, in charging the storage battery, a charging system that can avoid battery deterioration due to overcurrent can be constructed. In addition, it is possible to quantitatively evaluate deterioration that does not recover even when the storage battery is charged, and reduce unnecessary disposal.

Electromotive force of V ₀ battery Rs Internal resistance Rl Load resistance
Cb Equivalent capacity of electric double layer.
Rr Equivalent resistance associated with electrical double layer D1, D2 TCS circuit diode R2 TCS circuit capacitor discharge resistance C TCS circuit capacitor SW1 TCS circuit current switch

Claims (6)

A battery evaluation device for measuring the internal resistance of a chemical battery,
A load provided to flow current from the chemical battery;
A switch connected between the chemical battery and the load so as to cut off a discharge current from the chemical battery;
A measurement circuit provided so as to be able to measure a battery current and a battery voltage of the chemical battery,
The measurement circuit measures a transient phenomenon before and after the interruption of the discharge current with a battery voltage, and calculates the internal resistance of the chemical battery from the ratio of the measured battery voltage difference before and after the interruption of the discharge current and the discharge current. A battery evaluation device configured to be measurable. A battery evaluation device for measuring the internal resistance of a secondary battery,
A charger provided to be able to charge the secondary battery;
A switch connected between the secondary battery and the charger so as to cut off a charging current to the secondary battery;
A measurement circuit provided so as to be able to measure a battery current and a battery voltage of the secondary battery,
The measurement circuit measures a transient phenomenon before and after the interruption of the charging current with a battery voltage, and calculates the internal resistance of the secondary battery from the ratio of the measured battery voltage difference before and after the interruption of the charging current and the charging current. A battery evaluation apparatus characterized by being configured to measure the above.   3. The battery evaluation apparatus according to claim 1, wherein the measurement circuit is configured to cut off a direct current and remove a high frequency region that becomes a noise source when measuring a battery voltage. 4.   The battery evaluation apparatus according to claim 1, wherein the switch includes a transient current switch circuit. A battery evaluation method for measuring and evaluating the internal resistance of a chemical battery,
Connect a load to the chemical battery to pass current,
Measure the transient phenomenon before and after the interruption when the discharge current is interrupted with the battery voltage,
From the ratio of the battery voltage difference before and after the interruption of the discharge current and the discharge current, the internal resistance of the chemical battery is measured,
A battery evaluation method, wherein the chemical battery is evaluated based on the measured internal resistance. A battery evaluation method for measuring and evaluating the internal resistance of a secondary battery,
Connect a charger to the secondary battery to charge the secondary battery,
Measure the transient phenomenon before and after the interruption when the charging current is interrupted with the battery voltage,
From the ratio of the battery voltage difference before and after the interruption of the charging current and the charging current, the internal resistance of the secondary battery is measured,
A battery evaluation method comprising evaluating the secondary battery based on the measured internal resistance.