JP2015104138A - Charging method of secondary battery, and charging device employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging method of a secondary battery capable of reducing deterioration when charging the secondary battery by using a chemical reaction, and further capable of also performing deterioration diagnosis, and a charging device.SOLUTION: According to the charging method of the secondary battery for charging the secondary battery that is charged/discharged by using the chemical reaction, through an intermittent operation, each time charging of the intermittent operation is stopped, a polarization voltage is measured from a voltage of the secondary battery and when two-order time differentiation of a change of the polarization voltage with the passage of time is changed from positive to negative, control is performed to end charging by determining a full charge state.

Description

  The present invention relates to a method for charging a secondary battery and a charging device using the same, and more particularly to a method for charging a secondary battery capable of reducing deterioration of the secondary battery and a charging device using the same.

  Rechargeable batteries began with the invention of lead-acid batteries. In recent years, nickel-metal hydride batteries and lithium-ion batteries have been developed and put to practical use, and their applications have been expanded along with improvements in performance. Electric vehicles and hybrid vehicles combining a motor and an internal combustion engine are attracting attention for the reduction of carbon dioxide, and the secondary batteries used for these greatly affect the performance of electric vehicles and the like. In terms of its operation, a charging method that further reduces deterioration of the secondary battery and enables faster charging is desired.

  Secondary battery charging methods can be broadly divided into a constant current method and a constant voltage method. In the constant current method, the voltage applied between the terminals of the secondary battery increases with the progress of charging, which may cause deterioration of the secondary battery. The constant voltage method has a problem that it takes time to complete charging because charging current decreases as charging progresses. In addition, since charge / discharge characteristics and safety differ depending on the type of secondary battery, there are charging methods suitable for each secondary battery.

  In general, in charging a secondary battery, it is necessary to grasp the state of charging and the point in time when charging is completed, and to control the current and voltage during charging. In particular, in the quick charge that charges with a large current, it is important to accurately grasp the end point of the charge so as not to overcharge.

  Furthermore, when the battery is rapidly charged, there is a problem that the polarization becomes large and the charging voltage becomes high, causing deterioration of the secondary battery. Another problem is that the temperature of the secondary battery increases due to the generation of Joule heat during charging.

  Here, taking a nickel metal hydride battery as an example, a typical graph of the response waveform of the charging voltage with respect to the elapsed charging time is shown in FIG. When a nickel metal hydride battery is charged with a constant current, the charging voltage increases with the passage of charging time. After a certain period of time, the charging voltage suddenly increases, shows a peak, and then decreases. When the charge voltage increases at a peak and the time change rate of the charge voltage increase, that is, the time derivative of the charge voltage is obtained, dV / dt = 0 (zero). The voltage difference at which the charging voltage has dropped from the peak is called -ΔV.

  As a technique for grasping the end point of charging, a charging method for measuring the above-described peak of the charging voltage and -ΔV is disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-252086.

  Furthermore, Japanese Patent Application Laid-Open No. 5-083876 discloses that rapid charging is terminated when the second-order time derivative of the charging voltage changes from positive to negative.

Further, it is a method for charging a secondary battery of a non-aqueous electrolyte, and it is possible to detect a change in cell voltage generated when pulse charging is performed as a polarization voltage. 09-233725.
JP 2007-252086 A JP 05-038776 A JP 2008-181866 A JP 09-233725 A

  However, in the charging method for measuring the charging voltage peak or -ΔV, the charging voltage peak or decrease is detected, but when the charging voltage peak or decrease is detected, the secondary battery has already started to deteriorate. There is a fear. In addition, there is a method to control charging by capturing the temperature or temperature change of the secondary battery, but this method also detects the generation of Joule heat during charging, so detection is delayed compared to the method of measuring and judging voltage. Therefore, the secondary battery may be deteriorated.

  Further, since there is a possibility that the deterioration starts at the peak of the charging voltage, the charging is terminated when the second-order time derivative of the charging voltage is changed from positive to negative, which is an earlier timing, and the deterioration is suppressed. There is also. However, when the second-order time derivative of the charging voltage is detected, it is after the temperature starts to rise, and there is a possibility that the secondary battery has already started to deteriorate.

  The technique described in Japanese Patent Application Laid-Open No. 2008-181866 described above is a charging method for a secondary battery of a non-aqueous electrolyte, and lithium ion is assumed to be deteriorated by deposition of metallic lithium on the surface of the negative electrode. The increase in concentration polarization due to the uneven distribution of is detected. In addition, since this charging method is limited to the secondary battery of a nonaqueous electrolyte, it does not correspond to another secondary battery.

  The technology described in Japanese Patent Application Laid-Open No. 09-233725 described above is charged so that when the voltage of the secondary battery exceeds a certain level, gas is generated and deterioration occurs, so that the polarization voltage does not exceed a predetermined value. Control is performed to reduce the current value. At this time, the polarization voltage is calculated as a differential voltage obtained by obtaining the voltage twice at a predetermined timing after turning off the charging pulse current. With this method, it is difficult to obtain an accurate polarization voltage.

  Further, according to the charging time chart shown in FIG. 3 of the publication, a secondary battery is charged with a time (off time) of 100 milliseconds (0.1 seconds) with respect to a charging time (on time) of 1 second. The voltage between terminals is measured. It is stated that both the on time and the off time may be arbitrarily determined.

  Accordingly, an object of the present invention is to provide a secondary battery charging method capable of reducing deterioration during charging of a secondary battery that is charged and discharged using a chemical reaction, and a charging device using the same.

(Description of side reactions)
First, in order to facilitate understanding of the present invention before describing the present invention, the behavior of charging characteristics at the start of occurrence of a side reaction during charging of a secondary battery will be described.

  In order to understand the internal behavior associated with charging / discharging of the secondary battery, consider the equivalent circuit model of the secondary battery shown in FIG. On the electrode surfaces of the positive electrode 20 and the negative electrode 10, voltages are generated as electric double layers 50 and 40 based on the Nernst equation. At this time, the sum of the voltages 22 and 12 of the electric double layers in the positive electrode 20 and the negative electrode 10 in a steady state with no load becomes an electromotive force of the secondary battery.

  When the secondary battery is charged, the battery voltage increases from the electromotive force by the amount of pure resistance and polarization. This polarization is divided into polarization due to activation due to the activation energy of the electrode reaction and polarization due to diffusion caused by a decrease in the concentration of the reactant on the electrode surface as the electrode reaction proceeds. Charge transfer inside the battery during charging is divided into electron movement inside the electrode, a charging reaction involving electron movement on the electrode surface, and a process in which the active material diffuses from the solution to the electrode surface or vice versa. It is done.

  The polarization due to activation becomes prominent when the charging reaction on the electrode surface is in the rate-determining stage, and according to the Nernst equation, the voltage of the electric double layer increases to lower the activation energy of the charging reaction. The polarization due to diffusion becomes significant when the diffusion of the active material is at the rate-determining stage, and a difference in the concentration of the active material occurs between the electrode surface and the electrolyte bulk, and the voltage of the electric double layer increases according to the Nernst equation.

  By the way, a secondary battery using a chemical reaction is characterized in that electrons are transferred between an electrode and an electrolytic solution by a chemical reaction, and an electric current flows. The amount of electrons transferred by the charge / discharge reaction is limited to the amount of the active material previously filled in the battery.

FIG. 3 is a graph schematically showing the behavior of the battery when the secondary battery is charged beyond an amount capable of being charged.
As shown in FIG. 3A, when the secondary battery is continuously charged, the polarization voltage suddenly increases due to depletion of the active material for the charge reaction, and reaches a polarization voltage at which a side reaction occurs.
This is because, as shown in FIG. 3 (b), the main electrode reaction is changed from a charging reaction to a side reaction such as decomposition / reduction of the electrolytic solution or corrosion of the electrode lattice, and in a state close to a fully charged state. Yes, the charging efficiency with respect to the amount of charge injected into the battery decreases. Since the side reaction has higher activation energy than the charge reaction, the side reaction starts to dominate when the polarization voltage increases due to the difference in polarization due to activation.
FIG. 3C is a graph showing a state of charging, and shows a state of state (SOC) approaching 1 as the charging time elapses. The SOC approaching 1 indicates that the fully charged state is approaching.

  FIG. 4 shows a graph in which the polarization voltage on the electrode surface during charging of the secondary battery is measured. In the graph, the polarization voltage increases exponentially as it approaches near full charge. As the polarization voltage increases, a side reaction starts to occur, and the battery temperature rises due to the heat generated by the side reaction, so the polarization voltage decreases.

  The phenomenon described above will be described using the equivalent circuit model of the secondary battery shown in FIG. When the secondary battery is charged to reach the end of charging and the remaining amount of the charging active material decreases, the supply of the charging active material to the electrode surface cannot catch up. Since the charge active material is insufficient on the electrode surface, the polarization voltage due to diffusion increases exponentially, and the electric double layer voltage increases significantly. When a side reaction starts to occur due to an increase in the electric double layer voltage, the charging current apparently decreases due to the current consumption of the side reaction and the supply of the charging active material catches up, so that the rate of increase in polarization due to diffusion can be suppressed. At this time, the increasing slope of the polarization voltage becomes gentle. Thereafter, the polarization voltage decreases due to the heat generated by the side reaction.

  When a side reaction occurs, the discharge capacity is reduced due to an increase in internal resistance, and the secondary battery deteriorates. Therefore, if the polarization voltage is monitored during charging, it can be determined whether or not the side reaction is activated at that time, and charging can be appropriately terminated, so that deterioration during charging can be reduced.

(Comparison with conventional method)
Next, the present invention can terminate charging at a more appropriate timing than the conventional methods described above (Japanese Patent Laid-Open No. 2007-252086 and Japanese Patent Laid-Open No. 05-08876), and can reduce deterioration of the secondary battery. Explain that.

If the secondary battery continues to be charged beyond the fully charged state, the following phenomenon occurs, leading to an overcharged state.
(1) Side reaction starts to occur,
(2) The temperature inside the battery rises due to heat generated by side reactions,
(3) The charging voltage decreases as the battery temperature rises.

  As a conventional method for terminating charging, in the method based on the peak of the charging voltage or -ΔV, the end point is a stage where the charging voltage is lowered due to the temperature rise. When this is detected, the overcharging state has already been reached.

  On the other hand, in this invention, generation | occurrence | production of a side reaction is detected from a battery voltage, and charge is complete | finished. Specifically, since the side-reaction starts to occur and the increasing slope of the polarization voltage becomes gentle, this is detected as when the second-order time derivative of the polarization voltage changes from positive to negative. That is, according to the present invention, since the timing of the side reaction can be detected exactly, occurrence of the side reaction during charging can be suppressed, and deterioration of the secondary battery can be reduced.

  Here, among the prior arts, there is a method of detecting when the second-order time differentiation of the charging voltage has changed from positive to negative as the timing for terminating charging. At first glance, this prior art is a method that is similar to the present invention in determination, but has a different basic technical idea. The difference will be described below.

  Since the charging voltage has a negative temperature characteristic, as the side reaction is activated from the fully charged state to the overcharged state and the battery temperature rises due to reaction heat, the charging voltage changes from increasing to decreasing. Here, the time when the second-order time differentiation of the charging voltage changes from positive to negative is a stage where the battery temperature starts to rise. Since there is a time lag between the start of the side reaction and the temperature starting to rise, the side reaction occurs until the second time differential of the charging voltage is detected from positive to negative after the side reaction starts. If it continues, a secondary battery will deteriorate. Therefore, as compared with the second-order time derivative of the polarization voltage that detects the side reaction at the same time as the occurrence of the side reaction, the reduction of deterioration is insufficient with the second-order time derivative of the charging voltage.

  FIG. 5 shows changes over time in the first-order time derivative of the polarization voltage and the charging voltage when the secondary battery is charged by the intermittent charging operation. FIG. 5A and FIG. 5B are first-order time derivatives of the polarization voltage and the charging voltage, respectively, and the broken line in the figure indicates the time point when the first-order time derivative becomes maximum. Yes. In general, the maximum point of the first-order time derivative of a function is the point at which the second-order time derivative of the function changes from positive to negative. As is apparent from FIG. 5, it can be seen that the charge voltage is delayed from the timing at which the second-order time derivative of the polarization voltage changes from positive to negative.

  Therefore, since the present invention can detect the start of deterioration at a more accurate timing, it is possible to suppress the occurrence of side reactions during charging and to further reduce the deterioration of the secondary battery. Is clear.

  On the other hand, secondary batteries have not only a need to suppress deterioration but also a need for rapid charging. If charging is performed with a large charging current in order to shorten the charging time, a side reaction may occur due to the large charging current. For this reason, it is important not only to accurately detect the end of charging of the secondary battery, but also to appropriately reduce the charging current during the charging in the case of rapid charging with a large charging current.

  For example, it is preferable to reduce the charging current while confirming the change over time during charging with respect to the polarization voltage, the internal resistance, and the time constant of the voltage transient response during charging suspension. According to such a charging method of the secondary battery, it is possible to charge with a charging current as large as possible while reducing deterioration at the time of charging. Therefore, rapid charging is possible while suppressing deterioration.

  In addition, the judgment criteria for reducing the charging current obtained from changes in internal resistance and time constant over time are grasped as changes in polarization voltage over time, and when the secondary battery is actually charged, Control may be performed to lower the charging current based on a change in the target.

That is, the present invention is a method for charging a secondary battery,
The invention described in claim 1
In the charging method of the secondary battery that charges the secondary battery that charges and discharges using a chemical reaction by intermittent charging operation,
Each time charging is stopped in the intermittent charging operation, the polarization voltage is measured from the voltage of the secondary battery, and when the second-order time derivative of the time-dependent change of the polarization voltage changes from positive to negative, A charging method for a secondary battery, characterized in that charging is terminated as there is.

The invention described in claim 2
In the charging method of the secondary battery that charges the secondary battery that charges and discharges using a chemical reaction by intermittent charging operation,
Each time charging is stopped in the intermittent charging operation, the polarization voltage is measured from the voltage of the secondary battery, and when the second-order time derivative of the time-dependent change of the polarization voltage changes from positive to negative, Assuming that the charging under the intermittent charging operation is temporarily terminated,
After that, the secondary battery charging method is characterized in that the auxiliary charging is performed under a condition different from the charging condition and then the charging is terminated.

The invention according to claim 3
In the charging method of the secondary battery according to claim 1 or 2,
The secondary battery is characterized in that, when the change with time of the polarization voltage measured at each charging pause of the intermittent charging operation passes a minimum point, the charging current of the intermittent charging operation is lowered to perform subsequent charging. It is a charging method.

The invention according to claim 4
In the charging method of the secondary battery according to claim 1 or 2,
When the absolute value of the slope in the time-dependent change of the polarization voltage measured at each charging suspension of the intermittent charging operation becomes smaller than a predetermined value, the charging current of the intermittent charging operation is lowered to perform subsequent charging. It is the charging method of the secondary battery characterized.

The invention described in claim 5
In the charging method of the secondary battery of any one of Claims 1-4,
The internal resistance is measured every time the charging of the intermittent charging operation is stopped, and when the time-dependent change of the internal resistance passes a minimum point, the charging current of the intermittent charging operation is lowered to perform subsequent charging. This is a secondary battery charging method.

The invention described in claim 6
In the charging method of the secondary battery of any one of Claims 1-4,
The internal resistance is measured every time charging is stopped during the intermittent charging operation, and when the absolute value of the slope of the internal resistance over time is smaller than a predetermined value, the charging current of the intermittent charging operation is decreased and thereafter A method for charging a secondary battery, wherein charging is performed.

The invention described in claim 7
In the charging method of the secondary battery of any one of Claims 1-6,
Measure the time constant of the voltage transient response from the voltage of the secondary battery every time charging is stopped in the intermittent charging operation, and if the time constant of the time constant is bent, the charging current of the intermittent charging operation is lowered and then The secondary battery charging method is characterized in that the charging is performed.

The invention according to claim 8 provides:
In the charging method of the secondary battery according to claim 1 or 2,
At the time of charging suspension in the intermittent charging operation, when performing control to reduce the charging current by the polarization voltage obtained from the voltage of the secondary battery,
Among the secondary batteries, a certain secondary battery is charged in advance by intermittent charging operation for a plurality of charging currents, and at the time of charging suspension in the intermittent charging operation, polarization voltage, internal resistance, and time constant of voltage transient response Measure at least one of the
The polarization voltage when the change of the polarization voltage with time is minimized, and the judgment reference value by the polarization voltage,
The polarization voltage when the change in the internal resistance over time is minimized and the judgment reference value by the internal resistance,
The polarization voltage when the time-dependent change of the time constant of the voltage transient response is bent is set as a reference value by the time constant, and each of the plurality of charging current values is obtained,
The value of the polarization voltage measured when the secondary battery of the same type as the certain secondary battery is charged during the intermittent charging operation is
(1) Judgment reference value based on the polarization voltage,
(2) Judgment reference value by the internal resistance,
(3) Judgment reference value based on the time constant,
The secondary battery charging method is characterized in that the charging current of the intermittent charging operation is lowered when any of the above values is passed.

The invention according to claim 9 is:
In the charging method of the secondary battery according to claim 1 or 2,
At the time of charging suspension in the intermittent charging operation, when performing control to reduce the charging current by the polarization voltage obtained from the voltage of the secondary battery,
Among the secondary batteries, a certain secondary battery is charged in advance by intermittent charging operation for a plurality of charging currents, and at the time of charging suspension in the intermittent charging operation, polarization voltage, internal resistance, and time constant of voltage transient response Measure at least one of the
The polarization voltage when the change of the polarization voltage with time is minimized, and the judgment reference value by the polarization voltage,
The polarization voltage when the change in the internal resistance over time is minimized and the judgment reference value by the internal resistance,
The polarization voltage when the time-dependent change of the time constant of the voltage transient response is bent is set as a criterion value by the time constant, and each of the plurality of charging current values is obtained,
The value of the polarization voltage measured at the time of charging suspension of the intermittent charging operation of the secondary battery of the same type as the certain secondary battery;
(1) Judgment reference value based on the polarization voltage,
(2) Judgment reference value by the internal resistance,
(3) Judgment reference value based on the time constant,
When the absolute value of the difference from any one of the above values is smaller than a predetermined value, the charging method for the secondary battery is characterized in that the charging current of the intermittent charging operation is lowered and the subsequent charging is performed. .

The invention according to claim 10 is:
In the charging method of the secondary battery of any one of Claims 1-9,
When the polarization voltage of a secondary battery among the secondary batteries is measured in advance, and the second-order time derivative of the change over time in the polarization voltage changes from positive to negative, the fully charged state of the secondary battery And the polarization voltage value at the time of full charge, the discharge capacity of the secondary battery at that time is measured, the polarization voltage value at the time of full charge and the discharge capacity Find the correlation,
The discharge capacity of the secondary battery of the same kind is estimated from the polarization voltage value at the time of full charge and the correlation measured when the secondary battery of the same kind as the certain secondary battery is charged by intermittent charging operation. This is a method for charging a secondary battery.

The present invention is also a secondary battery charging device,
The invention according to claim 11
In a secondary battery charging device that charges a secondary battery that charges and discharges using a chemical reaction by intermittent charging operation,
For each charging suspension in the intermittent charging operation, the measuring means for measuring the polarization voltage from the voltage of the charging secondary battery,
A charging device for a secondary battery comprising control means for terminating charging as a fully charged state when a change with time of second-order time differentiation of the polarization voltage changes from positive to negative.

The invention according to claim 12
In a secondary battery charging device that charges a secondary battery that charges and discharges using a chemical reaction by intermittent charging operation,
For each charging suspension in the intermittent charging operation, the measuring means for measuring the polarization voltage from the voltage of the charging secondary battery,
When the time-dependent change of the second-order time derivative of the polarization voltage has changed from positive to negative, it has a control means for temporarily terminating the charging under the charging condition of the intermittent charging operation, assuming that it is in a fully charged state,
After that, the secondary battery charging apparatus includes a control unit that terminates the charging after performing the auxiliary charging under a condition different from the charging condition.

The invention according to claim 13
The secondary battery charging device according to claim 11 or 12,
Detecting means for detecting that a minimum point has been passed in the change over time in the polarization voltage measured at each charging suspension of the intermittent charging operation;
When the detection means detects that the minimum point has been passed in the change in polarization voltage over time,
A charging device for a secondary battery, comprising control means for lowering a charging current of the intermittent charging operation and performing subsequent charging.

The invention according to claim 14
The secondary battery charging device according to claim 11 or 12,
Detecting means for detecting that the absolute value of the slope of the time-dependent change of the polarization voltage measured at each charging suspension of the intermittent charging operation is smaller than a predetermined value;
When the detection means detects that the absolute value of the slope of the change in polarization voltage with time is smaller than a predetermined value,
A charging device for a secondary battery, comprising control means for lowering a charging current of the intermittent charging operation and performing subsequent charging.

The invention according to claim 15 is:
In the rechargeable battery charger according to any one of claims 11 to 14,
Measuring means for measuring the internal resistance at each charging stop of the intermittent charging operation, and detecting means for detecting that the minimum point of the change with time of the internal resistance has passed,
If the detection means detects that a minimum point has been passed in the change over time of the internal resistance,
A charging device for a secondary battery, comprising control means for lowering a charging current of the intermittent charging operation and performing subsequent charging.

The invention described in claim 16
In the rechargeable battery charger according to any one of claims 11 to 14,
Measuring means for measuring the internal resistance at each charging stop of the intermittent charging operation, and detecting means for detecting that the absolute value of the slope of the change over time of the internal resistance is smaller than a predetermined value,
When the detecting means detects that the absolute value of the slope of the internal resistance change with time is smaller than a predetermined value,
A charging device for a secondary battery, comprising control means for lowering a charging current of the intermittent charging operation and performing subsequent charging.

The invention described in claim 17
The rechargeable battery charger according to any one of claims 11 to 16,
Measurement means for measuring the time constant of the voltage transient response from the voltage of the secondary battery at each charging stop in the intermittent charging operation, and detection means for detecting that the time change of the time constant is bent. And
If the detection means detects that the time-dependent change of the time constant is bent,
A charging device for a secondary battery, comprising control means for lowering a charging current of the intermittent charging operation and performing subsequent charging.

The invention described in claim 18
The secondary battery charging device according to claim 11 or 12,
At the time of charging suspension of the intermittent charging operation, having a control means for reducing the charging current by the polarization voltage obtained from the voltage of the secondary battery,
Among the secondary batteries, a certain secondary battery is charged in advance by intermittent charging operation for a plurality of charging currents, and at the time of charging suspension in the intermittent charging operation, polarization voltage, internal resistance, and time constant of voltage transient response Measure at least one of the
The polarization voltage when the change of the polarization voltage with time is minimized, and the judgment reference value by the polarization voltage,
The polarization voltage when the change in the internal resistance over time is minimized and the judgment reference value by the internal resistance,
The polarization voltage when the time-dependent change of the time constant of the voltage transient response is bent is used as a judgment reference value by the time constant, and has a measuring means for obtaining each of the plurality of charging current values,
The value of the polarization voltage measured when the secondary battery of the same type as the certain secondary battery is charged during the intermittent charging operation is
(1) Judgment reference value based on the polarization voltage,
(2) Judgment reference value by the internal resistance,
(3) Judgment reference value based on the time constant,
A secondary battery charging apparatus comprising: a control unit that reduces the charging current of the intermittent charging operation when any of the above values is passed.

The invention according to claim 19 is
The secondary battery charging device according to claim 11 or 12,
At the time of charging suspension in the intermittent charging operation, having a control means for reducing the charging current by the polarization voltage obtained from the voltage of the secondary battery,
Among the secondary batteries, a certain secondary battery is charged in advance by intermittent charging operation for a plurality of charging currents, and at the time of charging suspension in the intermittent charging operation, polarization voltage, internal resistance, and time constant of voltage transient response Measure at least one of the
The polarization voltage when the change of the polarization voltage with time is minimized, and the judgment reference value by the polarization voltage,
The polarization voltage when the change in the internal resistance over time is minimized and the judgment reference value by the internal resistance,
The polarization voltage when the time-dependent change of the time constant of the voltage transient response is bent is used as a judgment reference value by the time constant, and has a measuring means for obtaining each of the plurality of charging current values,
The value of the polarization voltage measured at the time of charging suspension of the intermittent charging operation of the secondary battery of the same type as the certain secondary battery;
(1) Judgment reference value based on the polarization voltage,
(2) Judgment reference value by the internal resistance,
(3) Judgment reference value based on the time constant,
When the absolute value of the difference from any one of the above values is smaller than a predetermined value, there is provided a control means for lowering the charging current of the intermittent charging operation and performing subsequent charging. It is a charging device.

The invention according to claim 20 provides
The rechargeable battery charger according to any one of claims 11 to 19,
A change in the polarization voltage of a secondary battery over time is measured in advance, and the secondary battery is fully charged when the second-order time derivative of the change in polarization voltage over time changes from positive to negative. The determination means, and the polarization voltage value at the time of full charge as the determination means, the discharge capacity of the secondary battery at that time is measured, the correlation between the polarization voltage value at the time of full charge and the discharge capacity Control means for obtaining
The discharge capacity of the secondary battery of the same kind is estimated from the polarization voltage value at the time of full charge and the correlation measured when the secondary battery of the same kind as the certain secondary battery is charged by intermittent charging operation. A charging device for a secondary battery comprising an estimating means.

In the invention described in claims 1 and 11,
Measure the polarization voltage from the voltage of the secondary battery at every intermittent charge operation, and when the second-order time derivative of the change over time in the polarization voltage changes from positive to negative, it is in a fully charged state and side reaction Is where it begins to occur actively. Since the control for terminating the charging is performed at that timing, the occurrence of a side reaction of the secondary battery can be suppressed, and therefore the deterioration of the secondary battery during charging can be reduced.

  In addition, even if the usage status of the secondary battery to be charged is unknown, it is possible to measure the polarization voltage while charging and to control the termination of the charging according to the change over time. Can be reduced.

In the invention described in claims 2 and 12,
The secondary battery is fully charged when the second-order time derivative of the time-dependent change in the polarization voltage changes from positive to negative. However, the secondary battery can be recharged by lowering the electrical energy injected into the secondary battery. The charging rate can be as close as possible to 100% without deteriorating the battery. Further, by continuing to charge the electric energy injected into the secondary battery further lower, the fully charged state can be maintained without degrading the secondary battery.

In the invention described in claims 3 and 13,
During charging, the charging current is appropriately reduced by detecting that the change in polarization voltage with time has passed the minimum point. Thereby, even if it charges with a big charging current in order to shorten charging time, since a charging current can be reduced appropriately, the deterioration of a secondary battery can be reduced.

In the invention described in claims 4 and 14,
The fact that the time-dependent change in the polarization voltage has passed the minimum point is determined as the time when the absolute value of the change in the polarization voltage over time has become a predetermined value or less. Depending on the interval of intermittent charging operation, control to lower the charging current at the timing before the change of polarization voltage with time passes the minimum point, or at the timing that does not greatly exceed even if it passes the minimum point Therefore, deterioration of the secondary battery can be reduced.

In the invention described in claims 5 and 15,
During charging, the charging current is appropriately lowered by detecting that the change in internal resistance with time has passed the minimum point. Thereby, even if it charges with a big charging current in order to shorten charging time, since a charging current can be reduced appropriately, the deterioration of a secondary battery can be reduced.

In the invention described in claims 6 and 16,
It is determined that the time-dependent change in internal resistance has passed the minimum point as the time when the absolute value of the time-dependent change in internal resistance has become a predetermined value or less. Although it depends on the interval of intermittent charging operation, the control to lower the charging current at the timing before the internal resistance changes over time or even if it passes the minimum point Therefore, deterioration of the secondary battery can be reduced.

In the invention described in claims 7 and 17,
In the middle of charging, the charging current is appropriately reduced by detecting that the time constant has changed over time. Thereby, even if it charges with a big charging current in order to shorten charging time, since a charging current can be reduced appropriately, degradation of a secondary battery can be reduced.

In the invention described in claims 8 and 18,
Predetermined reference values for the polarization voltage, internal resistance, or voltage transient response time constant are obtained in advance, and the time-dependent change in the polarization voltage measured during charging suspension during intermittent charging operation is one of the determination reference values. If it exceeds, the charging current is lowered. For example, depending on the state of the secondary battery, the change in polarization voltage, internal resistance, and time constant over time may not be clear. Since the side reaction of the battery is prevented from being activated, deterioration of the secondary battery can be reduced. In addition, it is possible to measure the time constant of the internal resistance or voltage transient response over time without measuring the time constant of the internal resistance or voltage transient response by measuring the change in polarization voltage over time during intermittent charging operation. The charging current can be lowered based on the change.

In the invention described in claims 9 and 19,
Judgment that the time-dependent change in polarization voltage or internal resistance is minimized or that the time-dependent change in time constant is bent as the absolute value of each time-dependent change is less than or equal to the specified value. doing. Although it depends on the interval of intermittent charging operation, the charging current is adjusted at the timing before the time-dependent change in polarization voltage or internal resistance becomes minimum, or at the timing that does not greatly exceed even if it becomes minimum. Since the lowering control can be performed, the deterioration of the secondary battery can be reduced.
Alternatively, since the charging current can be controlled at a timing before the time-dependent change in time constant bends, or at a timing that does not greatly exceed even if it is bent, deterioration of the secondary battery can be reduced.

In the invention described in claims 10 and 20,
When the second-order time derivative of the change in polarization voltage over time changes from positive to negative, the charging is terminated, and from the correlation between the value of the polarization voltage at that time and the discharge capacity with respect to the fully charged polarization voltage value obtained in advance, The discharge capacity of the secondary battery used is estimated. According to this method, it is not necessary to add a discharge circuit or the like to the charger, and the degree of deterioration of the secondary battery can be easily diagnosed simply by charging the secondary battery.

  In addition, examples of the secondary battery to which the present invention is applied include a nickel metal hydride battery, a lithium ion battery, and a lead storage battery.

It is a figure which shows the response waveform of the charge voltage in a nickel metal hydride battery. It is a figure which shows the equivalent circuit model of a secondary battery. It is a figure explaining the state of the charge reaction and side reaction with time progress. It is the graph which measured the polarization voltage of the electrode surface at the time of charge of a secondary battery. It is a transition of the first-order time derivative of the polarization voltage and the first-order time derivative of the charge voltage when the secondary battery is charged by intermittent operation. It is a block block diagram of the charging device of Embodiment 1 which is an example of this invention. It is a flowchart of the charging method of Embodiment 1 which is an example of this invention. It is a figure which shows the voltage response waveform by intermittent charge mode. It is a figure explaining the method of estimation of the polarization voltage by spreading | diffusion. It is a figure which illustrates typically the control which reduces a charging current. FIG. 10A shows the transition of the charging current when the charging current is lowered based on the time-dependent changes in the polarization voltage, the internal resistance, and the time constant. The time course of the polarization voltage, the internal resistance, and the time constant at that time. The changes are illustrated in FIGS. 10 (b), (c) and (d), respectively. FIG. 11A schematically shows a temporal change in the polarization voltage when the side reaction is activated in the constant current charging. FIG. 11B schematically illustrates the first-order differentiation of the polarization voltage. FIG. 11C schematically illustrates the second derivative of the polarization voltage. 3 is a flowchart for determining a battery state in the first embodiment. It is the graph which showed the mode of the increase in a charging / discharging cycle and the transition of discharge capacity in the charge by the charging method of this invention, and the constant current charge which is the conventional charging method. (A) In the charging method of this invention and the conventional charging method, it is a graph which shows an example of the time change of a charging current, (b) The graph which shows an example of the time change of the polarization voltage in the charging method of this invention It is. It is a flowchart of the degradation diagnostic method in Embodiment 2 which is an example of this invention. It is the figure which plotted the discharge capacity with respect to a full charge polarization voltage value in a charge / discharge cycle test.

(Embodiment 1)
FIG. 6 is a block configuration diagram of the charging device according to Embodiment 1 of the present invention.
The charging device detects a charging voltage or a battery voltage of the secondary battery 1, a charging circuit 9 that supplies electricity for charging the secondary battery 1, a current detection unit 3 that detects a charging current of the charging circuit 9, and the like. A voltage detection unit 2; a voltage change calculation unit 6 that calculates a rate of change of the charging voltage over time when a charging voltage from the voltage detection unit is input; a charging current from the current detection unit 3; a voltage and a voltage from the voltage detection unit 2; Charge determining unit 7 that determines the charging status of the secondary battery based on each signal of the time change rate of the charging voltage from the change calculating unit 6, and charging that controls the current and voltage supplied by the charging circuit based on the signal from the charge determining unit And a control unit 8. The voltage change calculation unit 6 and the charge determination unit 7 may be configured in a microprocessor.

  The secondary battery 1 is connected to the charging circuit 9, the voltage detection unit 2, and the current detection unit 3. The voltage detection unit 2 and the current detection unit 3 include A / D converters 4a and 4b that convert detected analog data into digital data for digital processing in the charge determination unit 7, respectively. Furthermore, it is preferable that the voltage detection unit 2 and the current detection unit 3 include filters 5a and 5b that remove quantization noise in A / D conversion.

Hereinafter, the operation of the charging apparatus according to the first embodiment will be described.
First, the basic operation of the charging device will be described. The secondary battery 1 is charged with a constant current by the charging circuit 9, and the charging current flowing through the secondary battery 1 at this time is measured by the current detector 3, converted into digital data by the A / D converter 4b, and the filter 5b. , And noise is removed and output to the charge determination unit 7. The charging voltage of the secondary battery is detected by the voltage detection unit 2, converted into digital data by the A / D converter 4a, passed through the filter 5a, noise is removed, and the voltage change measurement unit 6 and the charging determination Is output to the unit 7.

FIG. 7 shows a flowchart of the operation of the charging apparatus having the above-described configuration.
The charging device may include a step (S100) of determining the state of the secondary battery prior to the start of charging. This state determination step will be described later.

  For example, when it is determined that charging is performed from the state of the secondary battery, charging is started (S101). Charging is performed by intermittent operation in a constant current mode (S102), and the charging current and charging voltage during charging are measured (S103). When charging is stopped in the intermittent charging operation, the polarization voltage is calculated from the transient response of the battery voltage detected by the voltage detector (S104).

The calculation of the polarization voltage by diffusion will be described in detail.
FIG. 8 is a graph schematically showing a typical example of the transient response of the battery voltage. When charging is suspended, the battery voltage drops rapidly (V1). This V1 corresponds to a voltage drop due to a pure resistance. The battery voltage then gradually decreases with time, and after Δτ has elapsed, it decreases by ΔV2. When the time further elapses, the battery voltage converges and V2 corresponding to the polarization voltage due to diffusion decreases. The converged voltage corresponds to the electromotive force of the secondary battery.

  In order to accurately grasp the end point of charging, it is necessary to accurately measure the polarization voltage. ΔV 2 measured in Δτ time is not an accurate value of the polarization voltage. In order to accurately measure the polarization voltage, it is necessary to take a long measurement time, and charging cannot be performed during this time. For this reason, the charging suspension time becomes long despite the fact that rapid charging is attempted, and the time required for charging becomes long after all. Therefore, in order to obtain a more accurate value of the polarization voltage with a limited charging pause time, the polarization voltage may be calculated from the transient response of the battery voltage.

Here, the battery voltage V is attenuated by an exponential function expressed by the following equation (1) by polarization due to diffusion.
(Equation 1)
V = V 2 · exp (−t / τ) + E Formula (1)
V2: Polarization voltage, t: elapsed time, τ: time constant, E: electromotive force FIG. 9 shows an example of data obtained by actually measuring how the battery voltage V decays with time.

  Since the above equation (1) includes three unknowns, if there are three or more measurement data in the transient response of the battery voltage V, these three unknowns can be determined. Therefore, when curve fitting is performed from three or more measurement data, the polarization voltage V2 due to diffusion can be accurately calculated.

  Returning to FIG. 7, it is determined whether or not the second-order time derivative of the change in polarization voltage with time has changed from positive to negative (S105). If the second-order time derivative is changed from positive to negative, charging is terminated (S107). Moreover, you may implement supplementary charge immediately after S107.

  If the second-order time derivative of the change with time of the polarization voltage is not from positive to negative, charging in the intermittent charging operation is continued (S106).

  In addition, in order to shorten the charging time without degrading the secondary battery, it is preferable to add a control in which charging is performed with a large charging current in the initial stage of charging and the charging current is stepped toward the end of charging. At this time, it is preferable that the determination to decrease the charging current be provided immediately after S106.

  The timing to decrease the charging current is when the change in polarization voltage over time is minimized, when the change in internal resistance over time is minimized, or when the change over time in the time constant of the voltage transient response is bent. There are three points. When charging with a large charging current, it can be interpreted that the risk of side reactions occurring at these points increases.

  It should be noted here that the charging current is not necessarily lowered when the above-mentioned point is detected. For example, in charging where the charging time exceeds 10 hours, the charging current is sufficiently small, so that no side reaction occurs during charging, and there is no need to lower the charging current. That is, when the charging current is lowered so that side reactions do not occur during charging, the charging current does not have to be lowered even if the above-mentioned points are detected thereafter. How much charge current value is required to control to lower the charge current depends on the performance of the secondary battery to be charged. Based on empirical rules, it is often necessary to lower the charging current during charging at a charging current value at which charging of the secondary battery is completed in about one hour.

Here, an example of control for reducing the charging current using the above-described point determination criterion will be described.
FIG. 10A shows the transition of the charging current. The charging current is decreased from I1 to I4 by detecting the minimum point of the polarization voltage, the minimum point of the internal resistance, and the bending point of the time constant. Changes in polarization voltage, internal resistance, and time constant at that time are shown in FIGS.

First, charging is performed by an intermittent charging operation with a charging current I1. Note that the polarization voltage, the internal resistance, and the time constant are measured every time intermittent charging is stopped.
As the charging is proceeded with the charging current I1, the change in the polarization voltage with time is minimized among the respective judgment criteria. Therefore, the charging current is lowered from I1 to I2 and then the charging is proceeded.
When charging is proceeded with the charging current I2, the change with time of the internal resistance is minimized among the respective judgment criteria. Therefore, the charging current is lowered from I2 to I3 and then the charging is proceeded.
When charging is proceeded with the charging current I3, the temporal change of the time constant in each criterion is bent. Therefore, the charging current is lowered from I3 to I4, and then the charging is proceeded.

  Further, the control for decreasing each charging current may be determined using any of the polarization voltage, the internal resistance, and the time constant change over time.

  From the above, if the present invention is used, for example, in the rapid charging in which the charging time is less than 1 hour, it is possible to control the charging current to be reduced according to the above-described determination criteria. Effective for reduction.

  As described above, the charging current may be controlled to be lowered when the change in the polarization voltage or the internal resistance with time passes through the minimum point. However, the present invention is not limited to this, and from the viewpoint of further reducing deterioration, control may be performed to lower the charging current at a stage where it can be considered that the value has been minimized. When the change of the polarization voltage or the internal resistance with time becomes almost zero, it can be regarded as the local minimum. Depending on the type of secondary battery, the value of the polarization voltage and the value of the internal resistance also change. For example, when the absolute value of the amount of change over time of the polarization voltage or the internal resistance falls below a predetermined value, the charging current is lowered. You may control.

  Further, the determination when the change in internal resistance with time passes through the minimum point or when the time constant is bent may be replaced with the polarization voltage. First, precharge a secondary battery of the same type as the secondary battery to be charged, and the change in polarization voltage when the internal resistance changes over time or when the time constant is bent, The determination reference value based on the internal resistance and the determination reference value based on the time constant are obtained. At this time, each determination reference value may be obtained for each of a plurality of charging currents.

  The secondary battery to be charged is charged with a certain charging current value, and when the polarization voltage transition passes the judgment reference value corresponding to the charging current value, the charging current may be controlled to decrease. Thereafter, when the transition of the polarization voltage passes the judgment reference value corresponding to each charging current value, the charging current may be controlled to decrease. In this way, it is possible to control the charging current to be lowered at various timings by simply monitoring only the polarization voltage when charging is stopped during the intermittent charging operation.

  The operations described above can be executed by, for example, software means incorporated in the microprocessor.

  One of the features of the charging method according to the present invention is that the polarization voltage is measured from the voltage of the secondary battery every time charging is stopped in the intermittent charging operation, and the second-order time derivative of the change over time of the polarization voltage is negative to positive. When it becomes, it is determined that the fully charged state has been reached and charging is terminated. Therefore, the time change of the polarization voltage will be described in detail below.

FIG. 11A schematically shows a temporal change in the polarization voltage when the side reaction is activated in the constant current charging.
In the stage (1), the polarization voltage rapidly increases as a sign that the side reaction is activated.
In the stage (2), the side reaction starts to become active, so that the slope of the increase in the polarization voltage with time becomes gentle.
In the stage (3), the polarization voltage is reduced by the heat generated by the side reaction.

  FIG. 11B schematically shows a graph of the rate of change of the polarization voltage with time, that is, the first-order time derivative of the polarization voltage. Here, the first-order time derivative of the polarization voltage is obtained from the difference between the polarization voltage obtained during a certain intermittent operation and the previous polarization voltage.

As is apparent from the figure, in the stage (1), it is understood that the first-order time derivative of the polarization voltage increases with the rapid increase of the polarization voltage due to the activation of the side reaction.
In the subsequent stage (2), the first-order time derivative of the polarization voltage decreases, and in the stage (3), the polarization voltage decreases by 1 due to the heat generated by the side reaction. The floor time derivative turns negative.

  Further, the second-order time derivative of the change in polarization voltage with time increases rapidly at the stage (1) and changes from positive to negative at the boundary with the stage (2). In the present invention, the deterioration of the secondary battery is reduced by capturing the time point and performing control to determine that the secondary battery is fully charged and terminate charging.

  As is clear from the above description, it is understood that the time change of the time change rate of the polarization voltage, that is, the second-order time derivative of the change of the polarization voltage with time changes in accordance with the occurrence of the side reaction. . Therefore, by detecting when the second-order time derivative of the change in polarization voltage over time changes from positive to negative, it is possible to capture signs that the side reaction is activated. As a result, charging can be terminated before the side reaction is activated, and deterioration of the secondary battery can be reduced.

  Next, a general technique will be described with reference to FIG. 12 for the step of determining the state of the secondary battery (S100). In this step (S100), the state of the secondary battery is diagnosed before starting charging, and it is determined whether or not charging is to be performed.

First, the battery voltage before applying the charging current is measured as an electromotive force (S1001). In this voltage measurement, it is preferable to wait until the change in battery voltage with time is substantially zero.
Next, intermittent charging operation for several cycles is performed (S1002), the battery voltage and charging current at that time are measured, and the internal resistance and polarization voltage are calculated from the voltage falling response and charging current value during the intermittent charging operation. Calculate (S1003).

Subsequently, it is determined whether or not charging is performed (S1004).
Generally, the electromotive force of the secondary battery becomes higher as the charging progresses, and the electromotive force in the fully charged state is the highest. If the value of the electromotive force calculated in S1001 is almost a fully charged value, it is determined that charging is not performed.
In general, the value of the internal resistance increases as the deterioration of the secondary battery proceeds. If the value of the internal resistance calculated in S1003 is greater than or equal to a predetermined value, it is determined that the secondary battery has not deteriorated and is not charged.
As described above, when it is determined that charging is performed by two determinations, the above-described charging is started.
The operations described above can be executed by software means incorporated in the microprocessor.

  The step of determining the state of the secondary battery shown in FIG. 12 is preferably applied before charging is started.

  According to the charging device having the configuration as described above, it is possible to detect where the main electrode reaction is switched from the charging reaction to the side reaction by detecting a sudden increase in the polarization voltage when charging with a constant current. become. As a result, it is possible to control charging to be terminated before a side reaction that causes deterioration of the battery is activated, and rapid charging is possible while suppressing deterioration of the secondary battery.

(Specific example 1)
The effect of suppressing deterioration during charging in the charging method according to the present invention will be described below using actually measured data.

  The characteristic of the charging method of the secondary battery shown in the specific example 1 is that the deterioration of the secondary battery is suppressed by having the control for detecting the timing for terminating the charging at the end of charging and the control for reducing the charging current during the charging. It is to enable rapid charging while suppressing.

  Therefore, in the charging method using the charging device described in the above-described first embodiment and the constant current charging method as the conventional technique, a graph showing an increase in the charge / discharge cycle and the transition of the discharge capacity is shown in FIG. Shown in The horizontal axis of the graph is the number of charge / discharge cycles, and the vertical axis of the graph is the discharge capacity when discharged at a current value of 2 amperes (A).

  Here, in the charging method according to the specific example 1, when the second-order time derivative of the time-dependent change in the polarization voltage is changed from positive to negative, the charge is terminated and the polarization voltage exceeds a predetermined criterion value. The charging current is stepped down. The constant current charging method which is a conventional technique is a charging method that is widely used in commercially available chargers.

  In general, a secondary battery deteriorates when a charge / discharge cycle is repeated, and for example, the discharge capacity is reduced to about half of the initial value in the vicinity of 500 charge / discharge cycles. Also, basically, the larger the current during charging / discharging, the easier side reactions occur, so the number of charging / discharging cycles until the secondary battery reaches the end of its life is shortened.

From the graph shown in FIG. 13, in the conventional constant current charging method, the initial discharge capacity was about 1800 mAh, and the discharge capacity after 500 charge / discharge cycles was about 1050 mAh.
On the other hand, in the charging method according to the present invention, as will be described in detail later, charging is performed with a current value larger than the charging current value in constant current charging, thereby shortening the charging time. Nevertheless, the initial discharge capacity is about 1800 mAh, the discharge capacity after 850 charge / discharge cycles is about 1050 mAh, and the effect of suppressing deterioration is about 1.7 times longer than the charge by the conventional method. I know that there is.

An additional feature of the charging method according to the present invention is that even if the secondary battery is charged with a large charging current value, deterioration of the secondary battery can be reduced by reducing the charging current at an appropriate timing.
In this specific example 1, the maximum value of the charging current was 4C, which is four times the capacity time ratio being C. On the other hand, in the conventional constant current charging method, a commercially available charger is reproduced in a simulated manner, and charging is performed at a current value that is one time the capacity time rate C.

  Next, the graph of FIG. 14 (a) shows an example of the change over time of the charging current in the charging method according to the present invention and the conventional method. In the graph of (b) and the charging method according to the present invention, An example of the temporal change of the polarization voltage is shown.

  As described above, the maximum value of the charging current in the charging method according to the present invention of Example 1 is 4C, and the capacity time rate C of the secondary battery used in Example 1 is 2 amps. did. On the other hand, the maximum value of the charging current in the conventional charging method was set to 2 amperes, which is 1 times the capacity time rate C.

As shown in FIG. 14, in the charging method according to the present invention, for example, charging is started at a current value of 4 amperes, and the polarization voltage is measured during charging suspension in a cycle in which charging is performed in an intermittent operation. When the secondary battery starts charging from an empty state, the polarization voltage immediately after the start of charging decreases, the polarization voltage in the middle of charging gradually increases, and the polarization voltage at the end of charging rapidly increases and then decreases. Here, since the polarization voltage at the start of charging is high, charging is not performed at the maximum current from the beginning, and after the decreasing slope of the polarization voltage becomes gentle, the charging current value is increased to 8 amps to charge the next cycle. Is going.
Thus, in order to reduce the deterioration, it is preferable not to charge at the maximum current at the start of charging, but to appropriately increase the charging current by looking at the state.

  Then, while confirming the polarization voltage, the value of the charging current is sequentially decreased, for example, by 2 amperes at an appropriate timing. In charging with a charging current of 8 amperes, when it is detected that the minimum point of the polarization voltage has been passed, the charging current value is reduced to 6 amperes and the charging is continued. For charging currents of 6 amps and 4 amps, the values of the polarization voltage when the internal resistance is minimized and the values of the polarization voltage when the time constant is bent are used as judgment reference values of 6 amp and 4 amp, respectively. As the charging proceeds, when the polarization voltage value is likely to pass the judgment reference value in each case, the charging current value is sequentially decreased to perform charging in the next cycle. In charging at a charging current value of 2 amperes, the second-order time differentiation of the polarization voltage changed from positive to negative, so that it was determined that charging was finished. At this time, the time required for charging was 30 minutes.

  On the other hand, in the conventional charging method, charging was performed at a constant current value of 2 amperes, and charging was terminated when the battery voltage became 10 mV lower than the maximum value (−ΔV method). At this time, the time required for charging was 70 minutes.

  Thus, in the charging method of the present invention, which is controlled based on the polarization voltage, as shown in FIG. 13, although charging is performed with a larger current value than the constant current charging method. When the lifetime is observed at the cycle number at which the discharge capacity is reduced to 60% of the initial value, it can be seen that the present invention has a lifetime about 1.7 times that of the constant current charging method. That is, in the charging method of the present invention, it is understood that the degree of deterioration can be suppressed more than the constant current charging of 1C due to the deterioration suppressing effect even though the charging is rapidly performed with the charging current value of the maximum value 4C.

  In addition, as for the charging time, it was confirmed that the constant current charging method required 70 minutes to complete the predetermined charging, whereas the charging method of the present invention can be charged in 30 minutes. This result shows that the charging method controlled using the polarization voltage of the present invention can suppress the deterioration due to charging while enabling the charging time to be reduced to half or less of the conventional constant current charging method. ing. That is, even when the current value during charging is increased as in the present invention, the occurrence of side reactions can be suppressed by controlling the polarization voltage so as not to increase.

  Further, in the charging method according to the present invention of this specific example 1, when the second-order time derivative of the change in polarization voltage with time changes from positive to negative, the auxiliary charging is performed without immediately ending the charging operation. May be. However, since the secondary battery is almost fully charged at this point, the electrical energy input to the secondary battery must be minimized. For example, it is preferable to reduce the on-duty ratio or the charging current value in the intermittent charging operation. Alternatively, constant voltage charging may be performed with an electromotive force value at full charge, or constant current charging with a fine current may be performed.

(Embodiment 2)
The charging device according to the second embodiment of the present invention is characterized in that in addition to terminating charging when the second-order time derivative of the polarization voltage changes from positive to negative, the polarization voltage value at that time is changed to a fully charged polarization voltage value. As a result, the function of diagnosing the degree of deterioration of the secondary battery as the discharge capacity maintenance rate from the correlation between the fully charged polarization voltage value recorded in advance in the charge determination unit 7 and the discharge capacity is added.

  Hereinafter, the operation of the charging apparatus according to the second embodiment will be described with reference to the flowchart shown in FIG. The deterioration diagnosis is performed after the secondary battery is completely charged.

  First, it is determined whether or not the second-order time derivative of the change over time in the polarization voltage has changed from positive to negative during charging before the start of diagnosis (S200).

If the second-order time derivative of the time-dependent change in the polarization voltage is changed from positive to negative, it is determined that the diagnosis is performed (S201), and at that time, the polarization voltage value is read as the fully charged polarization voltage value (S202).
The discharge capacity is estimated from the full charge polarization voltage value of the secondary battery to be diagnosed using the correlation equation of the discharge capacity with respect to the full charge polarization voltage value obtained in advance (S203). A capacity maintenance rate is calculated by dividing the estimated discharge capacity by the discharge capacity at the time of a new article (S204), and the deterioration diagnosis is terminated (S206). Note that S204 may be omitted and the discharge capacity may be output as a diagnosis result.

  If the second-order time derivative of the time-dependent change in the polarization voltage is not changed from positive to negative, the deterioration diagnosis is not performed (S205), and the charging is terminated.

  In addition, even if charging is performed multiple times and data is not accumulated, if there is data obtained by measuring the degree of deterioration in advance with a secondary battery of the same type as the secondary battery, the degree of deterioration of the secondary battery even with one measurement. Can be judged.

  FIG. 16 is a diagram in which the charge / discharge cycle test is actually performed as an example of the deterioration diagnosis, and the discharge capacity with respect to the polarization voltage measured at the time of full charge is plotted. In FIG. 16, the vertical axis represents the discharge capacity of the secondary battery, and the horizontal axis represents the full charge polarization voltage value.

  As is apparent from FIG. 16, the secondary battery repeats charging / discharging, so that the polarization voltage increases, and the discharge capacity decreases accordingly. Therefore, when charging / discharging is repeated, it is possible to estimate the progress of deterioration of the secondary battery by grasping the full charge polarization voltage value.

  Furthermore, the deterioration diagnosis technique according to the present invention is preferably applied to a secondary battery that is used in such a manner as to be repeatedly charged and discharged. As a problem in the above-described deterioration diagnosis of the secondary battery, since the value of the polarization voltage including the charge voltage, the discharge voltage, and the internal resistance depends on the SOC, the SOC at the time of the deterioration diagnosis must be the same every time. Since the deterioration diagnosis according to the present invention is performed after charging the secondary battery, it is satisfied each time by using the value of the polarization voltage when the second-order time derivative of the change of the polarization voltage with time changes from positive to negative. Deterioration can be estimated in the charged state.

  Furthermore, according to this configuration, by simply adding a function of accumulating and diagnosing data output from the voltage change calculation unit to the charge determination unit without changing the configuration of the charging device, it is possible to use the secondary battery repeatedly. The progress of deterioration can be estimated. That is, when adding a degradation diagnosis function to the charger, the diagnostic accuracy is easily degraded without much difference from general diagnostic methods such as the short-time discharge method, although additional mounting of a discharge circuit or the like is not required. Since it can be diagnosed, it is preferably used.

  The charging method of the secondary battery according to the present invention and the charging device used therefor are preferable because quick charging is possible while suppressing deterioration of the secondary battery in charging such as a nickel hydride battery, a lithium ion battery, and a lead storage battery. Available.

DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Voltage detection part 3 Current detection part 4a, 4b A / D converter 5a, 5b Filter 6 Voltage change calculation part 7 Charge diagnostic part 8 Charge control part 9 Charging circuits 11, 21 Pure resistance 30 of electrode Electrolytic solution 31 Electrolyte ion diffusion resistance 12, 22 Electric double layer voltage 13, 23 in steady state with no load Charge transfer resistance and diffusion resistance 14, 24 Electric double layer capacity 60 Separator

Claims (20)

In the charging method of the secondary battery that charges the secondary battery that charges and discharges using a chemical reaction by intermittent charging operation,
Each time charging is stopped in the intermittent charging operation, the polarization voltage is measured from the voltage of the secondary battery, and when the second-order time derivative of the time-dependent change of the polarization voltage changes from positive to negative, A charging method for a secondary battery, characterized in that charging is terminated as there is. In the charging method of the secondary battery that charges the secondary battery that charges and discharges using a chemical reaction by intermittent charging operation,
Each time charging is stopped in the intermittent charging operation, the polarization voltage is measured from the voltage of the secondary battery, and when the second-order time derivative of the time-dependent change of the polarization voltage changes from positive to negative, Assuming that the charging under the intermittent charging operation is temporarily terminated,
Thereafter, the secondary battery is charged under the condition different from the charge condition, and then the charge is terminated. In the charging method of the secondary battery according to claim 1 or 2,
The secondary battery is characterized in that, when the change with time of the polarization voltage measured at each charging pause of the intermittent charging operation passes a minimum point, the charging current of the intermittent charging operation is lowered to perform subsequent charging. Charging method. In the charging method of the secondary battery according to claim 1 or 2,
When the absolute value of the slope in the time-dependent change of the polarization voltage measured at each charging suspension of the intermittent charging operation becomes smaller than a predetermined value, the charging current of the intermittent charging operation is lowered to perform subsequent charging. A charging method for a secondary battery, which is characterized. In the charging method of the secondary battery of any one of Claims 1-4,
The internal resistance is measured every time the charging of the intermittent charging operation is stopped, and when the time-dependent change of the internal resistance passes a minimum point, the charging current of the intermittent charging operation is lowered to perform subsequent charging. Rechargeable battery charging method. In the charging method of the secondary battery of any one of Claims 1-4,
The internal resistance is measured every time charging is stopped during the intermittent charging operation, and when the absolute value of the slope of the internal resistance over time is smaller than a predetermined value, the charging current of the intermittent charging operation is decreased and thereafter A method for charging a secondary battery, wherein charging is performed. In the charging method of the secondary battery of any one of Claims 1-6,
Measure the time constant of the voltage transient response from the voltage of the secondary battery every time charging is stopped in the intermittent charging operation, and if the time constant of the time constant is bent, the charging current of the intermittent charging operation is lowered and then A method for charging a secondary battery, comprising: In the charging method of the secondary battery according to claim 1 or 2,
At the time of charging suspension in the intermittent charging operation, when performing control to reduce the charging current by the polarization voltage obtained from the voltage of the secondary battery,
Among the secondary batteries, a certain secondary battery is charged in advance by intermittent charging operation for a plurality of charging currents, and at the time of charging suspension in the intermittent charging operation, polarization voltage, internal resistance, and time constant of voltage transient response Measure at least one of the
The polarization voltage when the change of the polarization voltage with time is minimized, and the judgment reference value by the polarization voltage,
The polarization voltage when the change in the internal resistance over time is minimized and the judgment reference value by the internal resistance,
The polarization voltage when the time-dependent change of the time constant of the voltage transient response is bent is set as a criterion value by the time constant, and each of the plurality of charging current values is obtained,
The value of the polarization voltage measured when the secondary battery of the same type as the certain secondary battery is charged during the intermittent charging operation is
(1) Judgment reference value based on the polarization voltage,
(2) Judgment reference value by the internal resistance,
(3) Judgment reference value based on the time constant,
A charging method of a secondary battery, wherein the charging current of the intermittent charging operation is lowered when any of the above values is passed. In the charging method of the secondary battery according to claim 1 or 2,
At the time of charging suspension in the intermittent charging operation, when performing control to reduce the charging current by the polarization voltage obtained from the voltage of the secondary battery,
Among the secondary batteries, a certain secondary battery is charged in advance by intermittent charging operation for a plurality of charging currents, and at the time of charging suspension in the intermittent charging operation, polarization voltage, internal resistance, and time constant of voltage transient response Measure at least one of the
The polarization voltage when the change of the polarization voltage with time is minimized, and the judgment reference value by the polarization voltage,
The polarization voltage when the change in the internal resistance over time is minimized and the judgment reference value by the internal resistance,
The polarization voltage when the time-dependent change of the time constant of the voltage transient response is bent is set as a criterion value by the time constant, and each of the plurality of charging current values is obtained,
The value of the polarization voltage measured at the time of charging suspension of the intermittent charging operation of the secondary battery of the same type as the certain secondary battery;
(1) Judgment reference value based on the polarization voltage,
(2) Judgment reference value by the internal resistance,
(3) Judgment reference value based on the time constant,
When the absolute value of the difference from any one of the above values is smaller than a predetermined value, the charging method of the secondary battery is performed by lowering the charging current of the intermittent charging operation and performing subsequent charging. In the charging method of the secondary battery of any one of Claims 1-9,
The polarization voltage of a secondary battery among the secondary batteries is measured in advance, and when the second-order time derivative of the change over time in the polarization voltage changes from positive to negative, the secondary battery is fully charged. Assuming that the value of the polarization voltage is the polarization voltage value at full charge, and measuring the discharge capacity of the secondary battery at that time, the correlation between the polarization voltage value at full charge and the discharge capacity Seeking a relationship,
The discharge capacity of the secondary battery of the same kind is estimated from the polarization voltage value at the time of full charge and the correlation measured when the secondary battery of the same kind as the certain secondary battery is charged by intermittent charging operation. A method for charging a secondary battery. In a secondary battery charging device that charges a secondary battery that charges and discharges using a chemical reaction by intermittent charging operation,
For each charging suspension in the intermittent charging operation, the measuring means for measuring the polarization voltage from the voltage of the charging secondary battery,
A charging device for a secondary battery, comprising: a control unit that terminates charging as a fully charged state when a temporal change of the second-order time derivative of the polarization voltage changes from positive to negative. In a secondary battery charging device that charges a secondary battery that charges and discharges using a chemical reaction by intermittent charging operation,
For each charging suspension in the intermittent charging operation, the measuring means for measuring the polarization voltage from the voltage of the charging secondary battery,
When the time-dependent change of the second-order time derivative of the polarization voltage has changed from positive to negative, it has a control means for temporarily terminating the charging under the charging condition of the intermittent charging operation, assuming that it is in a fully charged state,
Thereafter, a charging device for a secondary battery, comprising: a control unit that terminates charging after performing supplementary charging under conditions different from the charging conditions. The secondary battery charging device according to claim 11 or 12,
Detecting means for detecting that a minimum point has been passed in the change over time in the polarization voltage measured at each charging suspension of the intermittent charging operation;
When the detection means detects that the minimum point has been passed in the change in polarization voltage over time,
A charging device for a secondary battery, comprising control means for lowering a charging current of the intermittent charging operation and performing subsequent charging. The secondary battery charging device according to claim 11 or 12,
Detecting means for detecting that the absolute value of the slope of the time-dependent change of the polarization voltage measured at each charging suspension of the intermittent charging operation is smaller than a predetermined value;
When the detection means detects that the absolute value of the slope of the change in polarization voltage with time is smaller than a predetermined value,
A charging device for a secondary battery, comprising control means for lowering a charging current of the intermittent charging operation and performing subsequent charging. In the rechargeable battery charger according to any one of claims 11 to 14,
Measuring means for measuring the internal resistance at each charging stop of the intermittent charging operation, and detecting means for detecting that the minimum point of the change with time of the internal resistance has passed,
If the detection means detects that a minimum point has been passed in the change over time of the internal resistance,
A charging device for a secondary battery, comprising control means for lowering a charging current of the intermittent charging operation and performing subsequent charging. In the rechargeable battery charger according to any one of claims 11 to 14,
Measuring means for measuring the internal resistance at each charging stop of the intermittent charging operation, and detecting means for detecting that the absolute value of the slope of the change over time of the internal resistance is smaller than a predetermined value,
When the detecting means detects that the absolute value of the slope of the internal resistance change with time is smaller than a predetermined value,
A charging device for a secondary battery, comprising control means for lowering a charging current of the intermittent charging operation and performing subsequent charging. The rechargeable battery charger according to any one of claims 11 to 16,
Measurement means for measuring the time constant of the voltage transient response from the voltage of the secondary battery at each charging stop in the intermittent charging operation, and detection means for detecting that the time change of the time constant is bent. And
If the detection means detects that the time-dependent change of the time constant is bent,
A charging device for a secondary battery, comprising control means for lowering a charging current of the intermittent charging operation and performing subsequent charging. The secondary battery charging device according to claim 11 or 12,
At the time of charging suspension of the intermittent charging operation, having a control means for reducing the charging current by the polarization voltage obtained from the voltage of the secondary battery,
Among the secondary batteries, a certain secondary battery is charged in advance by intermittent charging operation for a plurality of charging currents, and at the time of charging suspension in the intermittent charging operation, polarization voltage, internal resistance, and time constant of voltage transient response Measure at least one of the
The polarization voltage when the change of the polarization voltage with time is minimized, and the judgment reference value by the polarization voltage,
The polarization voltage when the change in the internal resistance over time is minimized and the judgment reference value by the internal resistance,
The polarization voltage when the time-dependent change of the time constant of the voltage transient response is bent is used as a judgment reference value by the time constant, and has a measuring means for obtaining each of the plurality of charging current values,
The value of the polarization voltage measured when the secondary battery of the same type as the certain secondary battery is charged during the intermittent charging operation is
(1) Judgment reference value based on the polarization voltage,
(2) Judgment reference value by the internal resistance,
(3) Judgment reference value based on the time constant,
A charging device for a secondary battery, comprising control means for reducing a charging current of the intermittent charging operation when any of the above values is passed. The secondary battery charging device according to claim 11 or 12,
At the time of charging suspension in the intermittent charging operation, having a control means for reducing the charging current by the polarization voltage obtained from the voltage of the secondary battery,
Among the secondary batteries, a certain secondary battery is charged in advance by intermittent charging operation for a plurality of charging currents, and at the time of charging suspension in the intermittent charging operation, polarization voltage, internal resistance, and time constant of voltage transient response Measure at least one of the
The polarization voltage when the change of the polarization voltage with time is minimized, and the judgment reference value by the polarization voltage,
The polarization voltage when the change over time of the internal resistance becomes a minimum point is a judgment reference value by the internal resistance,
The polarization voltage when the time-dependent change of the time constant of the voltage transient response is bent is used as a judgment reference value by the time constant, and has a measuring means for obtaining each of the plurality of charging current values,
The value of the polarization voltage measured at the time of charging suspension of the intermittent charging operation of the secondary battery of the same type as the certain secondary battery;
(1) Judgment reference value based on the polarization voltage,
(2) Judgment reference value by the internal resistance,
(3) Judgment reference value based on the time constant,
When the absolute value of the difference from any one of the above values is smaller than a predetermined value, there is provided a control means for lowering the charging current of the intermittent charging operation and performing subsequent charging. Charging device. The rechargeable battery charger according to any one of claims 11 to 19,
A means for measuring in advance the polarization voltage of a secondary battery, and determining that the secondary battery is in a fully charged state when the second-order time derivative of the change in polarization voltage over time is changed from positive to negative; Control means for determining the correlation between the polarization voltage value at the time of full charge and the discharge capacity by measuring the discharge capacity of the secondary battery at that time as the polarization voltage value at the time of full charge. Have
The discharge capacity of the secondary battery of the same kind is estimated from the polarization voltage value at the time of full charge and the correlation measured when the secondary battery of the same kind as the certain secondary battery is charged by intermittent charging operation. A charging device for a secondary battery comprising an estimating means.

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