JP5372208B2 - Secondary battery charging method and charging device using the same - Google Patents

Description

  The present invention relates to a secondary battery charging method and a charging device using the same, and further relates to a secondary battery charging method capable of performing deterioration diagnosis 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. In applications such as electric vehicles and hybrid electric vehicles that are attracting attention for reducing carbon dioxide, secondary batteries greatly affect their performance. In operation of a secondary battery, a quick charging is possible, and a charging method that further reduces deterioration of the battery 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 completion 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 completion time of charging, a charging method for measuring the above-described charging voltage peak and −ΔV is disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-252086.

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 2008-181866 A JP 09-233725 A

  However, in the charging method that measures the peak of the charging voltage and -ΔV, the increase in the charging voltage is detected. Therefore, when the increase in the charging voltage is detected, there is a possibility that the secondary battery has already started to deteriorate. 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.

  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. This charging method does not support charging of nickel metal hydride batteries or lead acid batteries.

  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.

  An object of this invention is to provide the charging method of a secondary battery which can reduce deterioration at the time of charge of the secondary battery charged / discharged using a chemical reaction, and a charging device using the same.

A method for charging a secondary battery according to the present invention, comprising:
Invention according to claim 1,
The secondary battery for charging and discharging by using a chemical reaction, in the charging method of the rechargeable battery to be charged by an intermittent operation,
When controlling the charging current to be lowered by the polarization voltage obtained from the voltage of the secondary battery during the charging suspension of the intermittent operation,
First, every time charging is stopped during the intermittent operation, the polarization voltage is measured from the voltage of the secondary battery, and when the second-order time derivative of the polarization voltage changes from positive to negative, the charging current is controlled to decrease. With
In advance, for the secondary battery, the charging current when charging by intermittent operation is increased, and the polarization voltage is measured at the time of charging suspension after charging with the respective charging current, and the polarization voltage with respect to the increase of the charging current A value obtained by multiplying the polarization voltage when the slope of the increase of the current by the current dependency coefficient of the polarization voltage of the secondary battery is a first threshold value,
The secondary battery charging method is characterized in that when the polarization voltage measured at each charging pause exceeds the first threshold value, the charging current is controlled to decrease.

The invention described in claim 2
In the charging method of the secondary battery according to claim 1 ,
First, the secondary battery is charged intermittently with respect to a plurality of charging currents, and the polarization voltage is measured every time charging is stopped in the intermittent operation. The second-order time derivative of the polarization voltage is negative to positive. The polarization voltage at the time of becoming the inflection point polarization voltage, respectively, to obtain a graph of the current dependence of the inflection point polarization voltage,
Next, for the secondary battery, the charging current when charging in an intermittent operation is increased stepwise, the polarization voltage is measured at the time of charging suspension after charging with each charging current, and the charging current is increased. The charging current Ib and the polarization voltage b when the inclination of the increase in the polarization voltage is reduced with respect to
Further, the polarization voltage a on the graph at the time of the charging current Ib is obtained,
A method for charging a secondary battery, wherein the current dependency coefficient of the polarization voltage is a value obtained by multiplying the graph of the current dependency of the inflection point polarization voltage by b / a.

The invention according to claim 3
In the charging method of the secondary battery according to claim 1 or 2 ,
When the polarization voltage measured at each charging pause is equal to or higher than a predetermined value for switching the charging operation, the diagnosis is performed more frequently than the normal operation from the normal operation in which the charging suspension frequency within the predetermined time is a predetermined number of times. A charging method for a secondary battery, wherein the charging is performed by switching to an operation.

The invention according to claim 4
In the charging method of the secondary battery of any one of Claims 1-3 ,
In advance, at the beginning of the secondary battery, the charging current when charging by intermittent operation is increased stepwise, and the polarization voltage is measured at the time of charging suspension after charging at each charging current , and the charging current The polarization voltage when the slope of increase of the polarization voltage becomes smaller with respect to the increase of the polarization voltage is determined as a second threshold, and the charging current at that time is the initial charging current,
Similarly, in the secondary battery in use, the charging current when charging in the intermittent operation is increased stepwise, and the polarization voltage is measured at the time of charging suspension after charging with the respective charging currents. Obtaining the charging current when the voltage exceeds the second threshold value, the charging current during use,
The secondary battery charging method is characterized in that the degree of deterioration of the secondary battery is determined based on a ratio of the charging current in use to the initial charging current.

The invention described in claim 5
In the charging method of the secondary battery of any one of Claims 1-3 ,
In addition, a data table that can store individual information on multiple secondary batteries is prepared.
For the secondary battery to be charged among the plurality of secondary batteries, the electromotive force value is measured from the polarization voltage measured at every charging suspension and the voltage value of the secondary battery, and together with the identification symbol of the secondary battery Accumulate in the data table;
The degree of deterioration of the secondary battery is determined from data in the data table relating to the secondary battery and data on the degree of deterioration measured in advance with a secondary battery of the same type as the secondary battery. 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 1-3 ,
A charging method for a secondary battery, wherein charging is performed by increasing the charging current if a polarization voltage measured at each charging pause time is equal to or less than a predetermined ratio of the set first threshold value. It is.

A charging device for a secondary battery according to the present invention , comprising:
The invention described in 請 Motomeko 7,
In a secondary battery charging device that charges a secondary battery that is charged and discharged using a chemical reaction in an intermittent operation,
A control mechanism for lowering the charging current by the polarization voltage obtained from the voltage of the secondary battery at the time of charging suspension of the intermittent operation;
The control mechanism first measures the polarization voltage from the voltage of the secondary battery every time the charging is stopped, and the control means reduces the charging current when the second-order time derivative of the polarization voltage changes from positive to negative. And having
For the secondary battery, the charging current when charging in an intermittent operation is increased in advance, the polarization voltage is measured at the time of charging suspension after charging with each charging current , and the charging current is increased to increase the polarization voltage. The first threshold value is a value obtained by multiplying the polarization voltage when the inclination of the increase in the polarization voltage with respect to the increase in the charging current is reduced by the current dependence coefficient of the polarization voltage of the secondary battery,
The secondary battery charging device according to claim 1, further comprising control means for reducing a charging current when a polarization voltage measured at each charging suspension exceeds the first threshold value.

The invention according to claim 8 provides:
The secondary battery charging device according to claim 7 ,
First, for the secondary battery, charging is performed intermittently with respect to a plurality of charging currents, and the polarization voltage is measured every time charging is stopped in the intermittent operation, and the second-order time derivative of the polarization voltage is changed from positive to negative. Obtain the polarization voltage at each time as the inflection point polarization voltage, obtain a graph of the current dependence of the inflection point polarization voltage,
Next, for the secondary battery, the charging current when charging in an intermittent operation is increased stepwise, the polarization voltage is measured at the time of charging suspension after charging with each charging current, and the charging current is increased. The charging current Ib and the polarization voltage b when the inclination of the increase in the polarization voltage is reduced with respect to
Further, the polarization voltage a on the graph at the time of the charging current Ib is obtained,
A charging device for a secondary battery, comprising means for setting the current dependency coefficient of the polarization voltage to a value obtained by multiplying the graph of the current dependency of the inflection point polarization voltage by b / a.

The invention according to claim 9 is:
The secondary battery charging device according to claim 7 or 8 ,
When the polarization voltage measured at each charging pause becomes equal to or higher than a predetermined value for switching the charging operation, a diagnosis with a larger number of charging pauses than the normal operation is performed from the normal operation in which the number of charging pauses within a predetermined time is a predetermined number. A charging device for a secondary battery comprising a control means for charging by switching to operation.

The invention according to claim 10 is:
The secondary battery charging device according to any one of claims 7 to 9 ,
In advance, at the beginning of the secondary battery, the charging current when charging by intermittent operation is increased stepwise, and the polarization voltage is measured at the time of charging suspension after charging at each charging current , and the charging current The polarization voltage when the slope of increase of the polarization voltage becomes smaller with respect to the increase of the polarization voltage is determined as a second threshold, and the charging current at that time is the initial charging current,
Similarly, in the secondary battery in use, the charging current when charging in the intermittent operation is increased stepwise, and the polarization voltage is measured at the time of charging suspension after charging with the respective charging currents. Obtaining the charging current when the voltage exceeds the second threshold value, the charging current during use,
A charging device for a secondary battery, comprising means for determining a degree of deterioration of the secondary battery based on a ratio of the charging current at the time of use to the initial charging current.

The invention according to claim 11
The secondary battery charging device according to any one of claims 7 to 9 ,
In addition, a data table that can store individual information on multiple secondary batteries is prepared.
For the secondary battery to be charged among the plurality of secondary batteries, the electromotive force is measured from the polarization voltage measured at every charging suspension and the voltage of the secondary battery, and the data together with the identification symbol of the secondary battery Accumulate on the table,
Means for judging the degree of deterioration of the secondary battery from the data in the data table relating to the secondary battery and the data of the degree of deterioration measured in advance for the same type of secondary battery of the secondary battery. It is the charging device of the secondary battery characterized.

The invention according to claim 12
The secondary battery charging device according to any one of claims 7 to 9 ,
A charging device for a secondary battery, characterized in that it has means for increasing the charging current and charging if the polarization voltage measured at each charging pause is less than or equal to a predetermined ratio of the first threshold value. It is.

In the invention described in claims 1 and 7 ,
The polarization voltage is measured from the voltage of the secondary battery every time charging is stopped during the intermittent operation, and the second-order time derivative of the polarization voltage changes from positive to negative before the side reaction starts. Since the charging current is controlled to decrease at that timing, the occurrence of side reactions can be suppressed in the secondary battery, so that the deterioration of the secondary battery can be reduced.

  Even if the usage status of the secondary battery is unknown, the polarization voltage can be measured while charging, and the charging current can be controlled by changing the voltage. Therefore, the deterioration of the secondary battery can be reduced.

In addition, a polarization voltage threshold is used in consideration of the current dependency of the polarization voltage, and when this value is exceeded, the charging current is controlled to decrease. For example, depending on the state of the secondary battery, it may be unclear when the second-order time derivative of the polarization voltage changes from positive to negative, and even in such a case, control for reducing the charging current can be reliably performed. Since the secondary battery can suppress the occurrence of side reactions, deterioration of the secondary battery can be reduced.

In the invention described in claims 2 and 8 ,
In the invention described in claims 1 and 7 ,
The current dependency coefficient of the polarization voltage of the secondary battery can be obtained reliably.

In the invention described in claims 3 and 9 ,
Even if the polarization voltage of the secondary battery increases and a side reaction is likely to occur, the secondary battery is charged by a diagnostic operation that has a higher number of charging pauses than the normal operation. For this reason, since it can grasp | ascertain without missing the increase in the polarization voltage which becomes a symptom of generation | occurrence | production of a side reaction, the control which reduces a charging current can be implemented reliably.

In the invention described in claims 4 and 10 ,
In the charging method of the secondary battery of any one of Claims 1-3 ,
Since the degree of deterioration of the secondary battery can be determined based on the ratio of the charging current at the time of use to the initial charging current in the secondary battery, more accurate determination can be made.
The initial secondary battery is often the start of use of a new secondary battery. If the current usage status is unknown, the secondary battery can be charged by the charging method or the charging device according to the present invention. It may be the time to start.

In the invention described in claims 5 and 11 ,
In addition, data related to secondary batteries can be stored individually using a data table that can store individual information on a plurality of secondary batteries. Therefore, secondary batteries can be more accurately compared with standard deterioration data. It is possible to determine the degree of deterioration of the.

In the invention described in claims 6 and 12 ,
If the polarization voltage measured at each charging stop is equal to or less than a predetermined ratio of the set first threshold value, charging is performed by increasing the charging current. Therefore, since the secondary battery can be charged with a charging current as large as possible within the range of the charging current that does not deteriorate, charging can be completed in as short a time as possible.

  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 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. 3 is a time chart of a charging voltage, a charging current, and a polarization voltage in the first embodiment. FIG. 10A schematically shows a temporal change in the polarization voltage when a side reaction is activated in constant current charging. FIG. 10B schematically illustrates the first derivative of the polarization voltage. FIG. 10 (c) schematically illustrates the second derivative of the polarization voltage. 3 is a flowchart for determining a battery state in the first embodiment. It is a figure explaining the method of calculating | requiring the point where the inclination of the increase in the polarization voltage with respect to the increase in charging current became small. It is a figure explaining a current dependence coefficient. It is a figure explaining the mode of degradation of a secondary battery. It is a figure explaining the difference in the side reaction start by the difference in charging current. 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) is a graph showing an example of a temporal change in charging current in the charging method of the present invention and the conventional charging method, and (b) a graph showing an example of a temporal change in polarization voltage in the charging method of the present invention. It is. It is the figure which plotted each fall amount in discharge capacity with respect to the internal resistance and polarization voltage which were measured at the time of a full charge in a charging / discharging cycle test.

(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, an equivalent circuit model of the secondary battery is shown in FIG. On the electrode surface, a voltage is generated as an electric double layer based on the Nernst equation. At this time, the sum of the voltages at the positive and negative electric double layers 12 and 22 in a steady state with no load becomes the electromotive force of the secondary battery.

  When the secondary battery is charged, the battery voltage increases from the electromotive force by the polarization voltage. This polarization is due to the resistance due to the electrical resistance of the electrolyte and electrode, the polarization due to the activation due to the activation energy of the electrode reaction, and the concentration of the reactant on the electrode surface decreases as the electrode reaction proceeds. And polarization caused by diffusion. 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 step, and according to the Nernst equation, the voltage of the electric double layer increases and acts to lower the activation energy of the charging reaction. The polarization due to diffusion becomes significant when the diffusion of the active material is in the rate-determining stage, and a difference in the concentration of the active material occurs between the electrode surface and the solution 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. 3 (a), 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 of the electrolytic solution or corrosion of the electrode grid, and the battery is almost fully charged. 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 the 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, after the polarization voltage increases and reaches a polarization voltage at which a side reaction occurs, 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. In the secondary battery, when charging progresses and the charge reaction amount starts to decrease with the amount of the charge active material, an increase in polarization due to diffusion becomes significant, and the charge voltage increases with the voltage of the electric double layer. At this time, charging reaction and side reaction are likely to occur on the electrode surface, but since the amount of active material remaining in the charging reaction is small, the charging reaction does not increase and the side reaction starts to occur actively. When a side reaction occurs, the discharge capacity is reduced due to an increase in internal resistance, and the secondary battery deteriorates. Therefore, if an increase in the polarization voltage existing on the electrode surface can be suppressed, deterioration during charging can be reduced.
Therefore, if the polarization voltage due to diffusion is monitored during charging, it can be determined whether the side reaction is activated at that time, and the charging current can be appropriately controlled, so that deterioration during charging can be reduced.

  In addition, in the secondary battery charging method according to the present invention, it is preferable to increase the charging current while confirming the polarization voltage. 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 during charging, so that rapid charging becomes possible.

(Embodiment 1)
FIG. 5 is a block configuration diagram of the charging device according to the first embodiment 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. 6 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 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 the constant current mode (S102), and the charging current and charging voltage during charging are measured (S103). Then, when charging is stopped in intermittent 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. 7 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 polarization due to 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 completion time of charging, it is necessary to accurately measure polarization due to diffusion. ΔV 2 measured in Δτ time is not an accurate value of polarization due to diffusion. In order to accurately measure the polarization due to diffusion, 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 polarization due to diffusion with a limited charging pause time, it is preferable to calculate the polarization voltage due to diffusion from the transient response of the battery voltage.

Here, the battery voltage V is attenuated by an exponential function expressed by the following equation by polarization due to diffusion.
(Equation 1)
V = V2 · exp (-t / τ) + E (1)
V2: Polarization voltage due to diffusion, t: elapsed time, τ: time constant, E: electromotive force FIG. 8 shows an example of data obtained by actually measuring how the battery voltage V decays with time.

  Since the 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. 6, it is determined whether the calculated polarization voltage is equal to or higher than the voltage for switching the charging operation to the diagnostic operation (S105).
When it is determined that the voltage is higher than the switching voltage, in order to accurately grasp the activation of the side reaction, the interval of the intermittent operation is shortened, and the diagnosis operation is more frequently stopped within a predetermined time than the normal operation. It may be controlled to charge with (S106).
If it is less than the switching voltage and the interval of the immediately preceding intermittent operation is short, the interval of the intermittent operation is returned to the initial value, and if the interval of the intermittent operation is the initial value, it is maintained.

  Then, it is determined whether or not the second-order time derivative of the polarization voltage has changed from positive to negative (S108). If the second-order time derivative changes from positive to negative, it is checked whether the charging current is below the set lower limit (S110). If the charging current is not below the set lower limit, the charging current is lowered and charging continues. If the charging current is not more than the set lower limit value (S111), the charging is terminated (S112).

If the second-order time derivative of the polarization voltage does not change from positive to negative, it is determined whether or not the polarization voltage is greater than or equal to a threshold value (first threshold value) (S109).
If the polarization voltage is equal to or higher than the threshold value, it is checked whether the charging current is equal to or lower than the set lower limit value (S110) .If the polarization voltage is lower than the threshold value, charging in intermittent operation is continued (S102). .

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

Here, typical examples of the first-order time differentiation and the second-order time differentiation of the charging voltage, the charging current, and the polarization voltage during charging of the charging device of Embodiment 1 are shown in FIG. 9 as a schematic graph.
First, the charging voltage increases with time. When the polarization voltage increases and becomes the diagnostic operation switching voltage, charging is performed in the diagnostic operation. In the diagnostic operation, the number of charging pauses is large, and the frequency of measuring the polarization voltage is high. Thus, when charged in the diagnostic operation, an increase in polarization voltage can be reliably captured.

  In this example, the charging current is the same as the normal operation even when the diagnosis operation is switched. When it is determined that the polarization voltage further increases and the second-order time derivative of the polarization voltage has changed from positive to negative, the charging current is reduced. When the charging current is lowered, the charging voltage is suddenly lowered, and it can be seen that charging is performed while suppressing deterioration.

  One of the features of the charging according to the present invention is that the polarization voltage is measured from the voltage of the secondary battery every time charging is stopped during intermittent operation, and when the second-order time derivative of the polarization voltage changes from positive to negative, The control is to lower the charging current. Therefore, the time change of the polarization voltage will be described in detail below.

FIG. 10A schematically shows a temporal change in the polarization voltage when a side reaction is activated in 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. 10 (b) schematically shows a graph of the time change rate of the polarization voltage, 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.

  Furthermore, the second-order time derivative of the polarization voltage 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 taking control at this point and reducing the charging current.

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

Next, the step of determining the state of the secondary battery (S100) will be described using FIG.
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 (S1001).
Next, an intermittent operation for one cycle is charged (S1002). A constant current is applied to the secondary battery, and the polarization voltage V1 due to resistance and the polarization voltage V2 due to diffusion are measured from the falling response of the battery voltage (S1003). In the measurement of V2, the above-described calculation method may be used.

The battery voltage before current application increases with the progress of charging, and the polarization voltage V2 increases rapidly in the vicinity of the fully charged state where the charging active material is exhausted. When the battery voltage is equal to or higher than the threshold value, in order to avoid overcharging, it is determined that no further charging is necessary, and the charging is terminated. When the battery voltage is lower than the threshold value and the polarization voltage is higher than the threshold value, it is determined that the secondary battery has deteriorated and the result is displayed. And the charge mentioned above 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. 11 is preferably applied before charging is started.

Here, how to obtain the first threshold value will be described.
FIG. 12 is a diagram for explaining a method for obtaining a point at which the slope of increase in polarization voltage with respect to increase in charging current is reduced. In FIG. 12, the horizontal axis is the charging current, and the vertical axis is the polarization voltage.

  For a secondary battery, the charging current is increased stepwise to measure the polarization voltage, and the measurement points are plotted on a graph. As the plots are connected, there is a point where the inclination of the increase in the polarization voltage with respect to the increase in the charging current becomes smaller. The charging current at this point is Ib and the polarization voltage b. The polarization voltage at this time may be used as a threshold value, but a value obtained by further multiplying the current dependency coefficient of the polarization voltage of the secondary battery may be set as the first threshold value.

Next, how to obtain the current dependency coefficient of the polarization voltage will be described with reference to FIG.
Regarding the secondary battery, charging was performed intermittently with respect to a plurality of charging currents, and the polarization voltage was measured at each charging pause in the intermittent operation, and the second-order time derivative of the polarization voltage was changed from positive to negative. Each polarization voltage is obtained as an inflection point polarization voltage. Then, the current dependency of the inflection point polarization voltage is plotted on a graph, and the current dependency of the threshold value is obtained by connecting the plots.
Subsequently, the value on the graph of the charging current obtained previously in Ib is read to obtain the polarization voltage a.
Then, b / a is calculated, and a value obtained by multiplying the current dependence graph of the inflection point polarization voltage by b / a is defined as a current dependence coefficient of the polarization voltage.

  Apart from this, in the charging method and the charging device according to the present invention, for example, it is possible to make a determination of deterioration from another viewpoint with respect to a fully charged secondary battery that has been charged. When the charging current applied to the fully charged secondary battery is increased, the degree of deterioration can be determined based on the charging current when the polarization voltage exceeds the second threshold value. Specifically, when the charge current when the polarization voltage exceeds the second threshold value during use is smaller than the initial charge current, it can be determined that the secondary battery has deteriorated. it can. This will be described below.

FIG. 14 (a) is a graph schematically showing how the polarization voltage increases when the charging current is increased.
Until the stage (1), the polarization voltage hardly increases even if the charging current increases. At this time, the side reaction hardly occurs.
In the stage (2), as the charging current increases, the polarization voltage increases rapidly, and a side reaction begins to occur when the slope of increase in the polarization voltage becomes gentle.
In the stage (3), even if the charging current increases, the polarization voltage is almost saturated and hardly increases.

  FIG. 14B schematically shows a state in which the value of the charging current varies depending on the state of deterioration of the secondary battery. For example, if the rechargeable battery is in the same charging state, the charging current at which the polarization voltage starts to increase, i.e. the charging current when the slope of the increase in the polarization voltage becomes smaller with respect to the increase in the charging current, It can be seen that the value is small. That is, in a fully charged secondary battery, the degree of deterioration of the secondary battery can be determined from the magnitude of the charging current value at which the polarization voltage starts to increase.

Furthermore, if the charging current at the beginning of the secondary battery is measured in advance, and the degree of deterioration of the secondary battery is determined from the ratio between the initial charging current and the charging current at the time of use, the accuracy of the determination is further improved. Since it becomes high, it is preferable.
Such a function can be realized by software means incorporated in the microprocessor.

Here, it will be described that the side reaction start timing varies depending on the charging current. In FIG. 15, (a) is a graph obtained by measuring the state of increase in polarization voltage with respect to charging time when charging is performed at a charging current of 2 amperes (A). (B) is also a graph when it is charged with a charging current of 4 amperes.
From FIG. 15, it can be seen that the side reaction is started at an earlier timing when the battery is charged with the charging current 4 </ b> A.

  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. Thus, it becomes possible to control to lower the charging current before the side reaction that causes the deterioration of the battery is activated. As a result, rapid charging is possible while suppressing deterioration of the secondary battery due to large current charging. Therefore, a charging current larger than that of the conventional quick charging method can be set, and the charging time can be further shortened.

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

  One of the features of charging according to the present invention is that control is performed to reduce the charging current when the second-order time derivative of the polarization voltage changes from positive to negative.

  Therefore, in the charging using the charging device described in the first embodiment as the charging according to the present invention and the constant current charging which is the conventional method, a graph showing the state of the increase in the charge / discharge cycle and the transition of the discharge capacity is shown. As shown in FIG. 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, constant current charging, which is a conventional method, 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. 16, first, in the constant current charging of the conventional method, the initial discharge capacity was about 1750 mAh, and the discharge capacity after 500 charge / discharge cycles was about 1050 mAh. On the other hand, as will be described in detail later, the charging according to the present invention is performed by charging 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 1850 mAh, the discharge capacity after 500 charge / discharge cycles is about 1020 mAh, and it can be seen that the degree of deterioration of charging by the conventional method is comparable.

The charging according to the present invention may be understood from another point of view by setting a polarization voltage threshold value and charging with a charging current in a range in which the polarization voltage during charging does not exceed the threshold value.
The maximum value of the charging current in this specific example 1 was 3C, which is three times the capacity time ratio C. On the other hand, in the constant current charging method which is a conventional method, a commercially available charger is simulated, and charging is performed at a current value that is one time the capacity time rate C.

  Next, the graph of FIG. 17A shows an example of the temporal change of the charging current in the charging according to the present invention and the conventional method. In the graph of FIG. An example of the temporal change in voltage is shown.

  As described above, the maximum value of the charging current in the charging according to the present invention of the specific example 1 is 3 C, and the capacity time rate C of the secondary battery used in the specific example 1 is 2 amperes, so that it is 6 amperes. . On the other hand, the maximum value of the charging current in the conventional charging is 2 amperes, which is 1 times the capacity time rate C.

  A specific feature of charging according to the present invention is understood that the charging current is controlled so that the polarization voltage does not exceed the set threshold as shown in FIG. Good. More specifically, the threshold value to be set is slightly smaller than the threshold value obtained by the above-described method, for example, set as a 90% threshold value, and the diffusion polarization voltage exceeds the 90% threshold value. In such a case, the charging current may be reduced. Thus, for example, the reason why the 90% threshold value is set as the threshold value is that safety is expected in order to prevent side reactions as much as possible.

  As shown in FIG. 17, in the charging according to the present invention, charging is started at a current value of, for example, 4 amperes, and the polarization voltage is measured during an intermittent cycle of charging in an intermittent operation. Since the polarization voltage at the beginning of charging is, for example, 16 mV or less, which is 80% or less of the set threshold value 20 mV, in order to perform more rapid charging, the charging current value is increased to, for example, 4.5 amperes, The next cycle is being charged.

  Then, when the charging current value is sequentially increased while confirming the polarization voltage, the set maximum charging current value (6 amperes) is reached. If charging continues at 6 amps, the value of the polarization voltage increases and exceeds, for example, the 90% threshold value. Therefore, the charging current value is lowered to 5.5 amps and the next cycle is charged. . Even if the charging current value is maintained at 5.5 amperes, as the charging progresses, the value of the polarization voltage increases again and reaches the 90% threshold value. The battery is charged to the next cycle after being lowered to 4 amps. Then, when the charging current value was charged at 4 amperes, the charged secondary battery reached a predetermined temperature, so that it was determined that charging was completed. At this time, the time required for charging was 24 minutes.

On the other hand, in the conventional charging, the charging was continued at a constant current value of 2 amperes. Similarly, the charging is completed when the secondary battery reaches a predetermined temperature. At this time, the time required for charging was 60 minutes.
In the first embodiment described above, the charging is terminated when the charging current becomes equal to or lower than the set lower limit value. However, in the first specific example, the determination of the completion of charging is performed at the time when the secondary battery reaches a predetermined temperature for simplification. Furthermore, the determination of the completion of charging may be performed at the time when the charging amount (current × time) becomes a predetermined value.

  Thus, in the charging method of the present invention, which is controlled based on the polarization voltage, as shown in FIG. 16, although charging is performed with a larger current value than in the constant current charging method. It can be seen that the discharge capacity is almost the same as that of the constant current charging method and has the same life. That is, it can be seen that the charging method according to the present invention can suppress the deterioration rate to the same level as that of the constant current charging of 1C, although it is rapidly charged with the charging current value of the maximum value of 3C.

  Moreover, with regard to the charging time, it was confirmed that the constant current charging method required 60 minutes to complete predetermined charging, whereas the charging method of the present invention can be charged in 24 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 activation due to the occurrence of a side reaction can be suppressed by controlling the polarization voltage so as not to increase.

  Further, in the charging according to the present invention of the specific example 1, if the polarization voltage is a predetermined value, for example, less than 80% of the threshold value, it is preferable to perform control to increase the charging current. By performing such control, charging can be performed with a larger charging current within a range in which the degree of deterioration due to charging is not increased. Therefore, such control is preferable from a practical viewpoint because the secondary battery is charged more rapidly and does not increase the degree of deterioration due to charging. If the voltage value of diffusion polarization is not less than 80% and less than 90% of the set threshold value, the charging current value may be maintained.

(Embodiment 2)
A feature of the charging device according to the second embodiment of the present invention is that the charging judgment unit 7 accumulates data output from the voltage change calculation unit 6 in a data table and diagnoses the progress of deterioration in the secondary battery from the tendency. Is added.

  For example, a function for storing the electromotive force, the charging voltage, and the internal resistance and a function for registering the identification number of the secondary battery in the data table are added to the charging diagnosis unit 7. When charging the secondary battery, the secondary battery identification number is entered by the user to determine the end of charging, such as the electromotive force, the charging voltage, the polarization voltage, the capacity drop during discharging, etc. Data relating to battery deterioration can be accumulated in the data table, and when charging is repeated, the progress of secondary battery deterioration can be estimated from the tendency of these data.

  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. 18 is a diagram in which the charge / discharge cycle test is actually performed as an example of the deterioration diagnosis, and the respective reduction amounts in the discharge capacity are plotted against the internal resistance and the polarization voltage measured at the time of full charge. In FIG. 16, the vertical axis represents the amount of decrease in discharge capacity with respect to the initial discharge capacity value of 1800 mAh. In the horizontal axis, the polarization voltage value is set to the same current application condition by applying a current value correction at the time of measurement in order to indicate the ease of increase of the polarization voltage.

  As can be seen from FIG. 18, the secondary battery is repeatedly charged and discharged, whereby the polarization voltage and the internal resistance increase, and the discharge capacity decreases accordingly. Therefore, when charging / discharging is repeated, the progress of deterioration of the secondary battery can be estimated by grasping the tendency of the polarization voltage and internal resistance data.

Furthermore, in the secondary cell, as well as the polarization voltage and the internal resistance of the data, the should also be accumulated capacity reduction amount at the time of discharge, in the secondary battery, without have any measured progression of pre-degradation It is preferable because the progress of deterioration of the secondary battery can be estimated.

  The identification function may be another method. In addition, the acquisition timing of the accumulated data may be not only at the time of charging end determination, but also at a step before starting charging (S100). When diagnosing with data before the start of charging, since the charging state of the secondary battery can be considered from a fully charged state to a fully discharged state, the polarization voltage data is a function of the number of times of charging and the charging state. By preparing a map showing the polarization voltage with respect to the electromotive force that increases with the state of charge, and plotting the acquired data, it is possible to estimate the progress of deterioration due to repeated charging from the increasing tendency of the polarization voltage.

  According to this configuration, without changing the configuration of the charging device, the function of accumulating and diagnosing data output from the voltage change calculation unit is added to the charging determination unit, and deterioration due to repeated use of the secondary battery is prevented. Progress can be estimated. In addition, if the diagnosis is based on the acquired data at the end of charging, only the fully charged state data can be obtained, and the load on the diagnostic process can be reduced. Information on the polarization voltage can be obtained.

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

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 circuit 11, 21 Pure resistance 31 of electrode Electrolytic solution 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 capacitance

Claims (12)

In a charging method of a secondary battery that charges a secondary battery that charges and discharges using a chemical reaction in an intermittent operation,
When controlling the charging current to be lowered by the polarization voltage obtained from the voltage of the secondary battery during the charging suspension of the intermittent operation,
First, every time the charging is stopped, the polarization voltage is measured from the voltage of the secondary battery, and when the second-order time derivative of the polarization voltage changes from positive to negative, the charging current is controlled to be reduced,
In advance, for the secondary battery, the charging current when charging by intermittent operation is increased, and the polarization voltage is measured at the time of charging suspension after charging with the respective charging current, and the polarization voltage with respect to the increase of the charging current A value obtained by multiplying the polarization voltage when the slope of the increase of the current by the current dependency coefficient of the polarization voltage of the secondary battery is a first threshold value,
A charging method for a secondary battery, characterized in that when the polarization voltage measured at each charging pause exceeds the first threshold value, the charging current is controlled to decrease. In the charging method of the secondary battery according to claim 1 ,
First, the secondary battery is charged intermittently with respect to a plurality of charging currents, and the polarization voltage is measured at each charging pause in the intermittent operation. The second-order time derivative of the polarization voltage is negative to positive. The polarization voltage at the time of becoming the inflection point polarization voltage, respectively, to obtain a graph of the current dependence of the inflection point polarization voltage,
Next, for the secondary battery, the charging current when charging in an intermittent operation is increased stepwise, the polarization voltage is measured at the time of charging suspension after charging with each charging current, and the charging current is increased. The charging current Ib and the polarization voltage b when the inclination of the increase in the polarization voltage is reduced with respect to
Further, the polarization voltage a on the graph at the time of the charging current Ib is obtained,
A method for charging a secondary battery, wherein the current dependency coefficient of the polarization voltage is a value obtained by multiplying the graph of the current dependency of the inflection point polarization voltage by b / a. In the charging method of the secondary battery according to claim 1 or 2 ,
When the polarization voltage measured at each charging pause becomes equal to or higher than a predetermined value for switching the charging operation, a diagnosis with a larger number of charging pauses than the normal operation is performed from the normal operation in which the number of charging pauses within a predetermined time is a predetermined number. A charging method for a secondary battery, wherein the charging is switched to operation. In the charging method of the secondary battery of any one of Claims 1-3 ,
In advance, at the beginning of the secondary battery, the charging current when charging by intermittent operation is increased stepwise, and the polarization voltage is measured at the time of charging suspension after charging at each charging current , and the charging current The polarization voltage when the slope of increase of the polarization voltage becomes smaller with respect to the increase of the polarization voltage is determined as a second threshold, and the charging current at that time is the initial charging current,
Similarly, in the secondary battery in use, the charging current when charging in the intermittent operation is increased stepwise, and the polarization voltage is measured at the time of charging suspension after charging with the respective charging currents. Obtaining the charging current when the voltage exceeds the second threshold value, the charging current during use,
A method for charging a secondary battery, comprising: determining a degree of deterioration of the secondary battery based on a ratio of the charging current at the time of use to the initial charging current. In the charging method of the secondary battery of any one of Claims 1-3 ,
In addition, a data table that can store individual information on multiple secondary batteries is prepared.
For the secondary battery to be charged among the plurality of secondary batteries, the electromotive force is measured from the polarization voltage measured at every charging suspension and the voltage of the secondary battery, and the data together with the identification symbol of the secondary battery Accumulate on the table,
The degree of deterioration of the secondary battery is determined from data in the data table relating to the secondary battery and data on the degree of deterioration measured in advance with a secondary battery of the same type as the secondary battery. Rechargeable battery charging method. In the charging method of the secondary battery of any one of Claims 1-3 ,
A charging method for a secondary battery, wherein charging is performed by increasing the charging current if a polarization voltage measured at each charging pause time is equal to or less than a predetermined ratio of the first threshold value. In a secondary battery charging device that charges a secondary battery that is charged and discharged using a chemical reaction in an intermittent operation,
A control mechanism for lowering the charging current by the polarization voltage obtained from the voltage of the secondary battery at the time of charging suspension of the intermittent operation;
The control mechanism first measures the polarization voltage from the voltage of the secondary battery at every charging stop of the intermittent operation, and when the second-order time derivative of the polarization voltage changes from positive to negative, the charging current Control means for lowering
In advance, for the secondary battery, the charging current when charging by intermittent operation is increased, and the polarization voltage is measured at the time of charging suspension after charging with the respective charging current, and the polarization voltage with respect to the increase of the charging current A value obtained by multiplying the polarization voltage when the slope of the increase of the current by the current dependency coefficient of the polarization voltage of the secondary battery is a first threshold value,
A charging device for a secondary battery, comprising control means for reducing a charging current when a polarization voltage measured at each charging suspension exceeds the first threshold value. The secondary battery charging device according to claim 7 ,
First, the secondary battery is charged intermittently with respect to a plurality of charging currents, and the polarization voltage is measured at each charging pause in the intermittent operation. The second-order time derivative of the polarization voltage is negative to positive. The polarization voltage at the time of becoming the inflection point polarization voltage, respectively, to obtain a graph of the current dependence of the inflection point polarization voltage,
Next, for the secondary battery, the charging current when charging in an intermittent operation is increased stepwise, the polarization voltage is measured at the time of charging suspension after charging with each charging current, and the charging current is increased. The charging current Ib and the polarization voltage b when the inclination of the increase in the polarization voltage is reduced with respect to
Further, the polarization voltage a on the graph at the time of the charging current Ib is obtained,
A charging device for a secondary battery, comprising means for setting the current dependency coefficient of the polarization voltage to a value obtained by multiplying the graph of the current dependency of the inflection point polarization voltage by b / a. The secondary battery charging device according to claim 7 or 8 ,
When the polarization voltage measured at each charging pause becomes equal to or higher than a predetermined value for switching the charging operation, a diagnosis with a larger number of charging pauses than the normal operation is performed from the normal operation in which the number of charging pauses within a predetermined time is a predetermined number. A charging device for a secondary battery, comprising control means for charging by switching to operation. The secondary battery charging device according to any one of claims 7 to 9 ,
In advance, at the beginning of the secondary battery, the charging current when charging by intermittent operation is increased stepwise, and the polarization voltage is measured at the time of charging suspension after charging at each charging current , and the charging current The polarization voltage when the slope of increase of the polarization voltage becomes smaller with respect to the increase of the polarization voltage is determined as a second threshold, and the charging current at that time is the initial charging current,
In the secondary battery in use, the charging current when charging by intermittent operation is increased stepwise, and the polarization voltage is measured at the time of charging suspension after charging with the respective charging current. The charge current when the second threshold value is exceeded is determined as the charge current during use.
A charging device for a secondary battery, comprising means for determining a degree of deterioration of the secondary battery based on a ratio of the charging current at the time of use to the initial charging current. The secondary battery charging device according to any one of claims 7 to 9 ,
In addition, a data table that can store individual information on multiple secondary batteries is prepared.
For the secondary battery to be charged among the plurality of secondary batteries, the electromotive force is measured from the polarization voltage measured at every charging suspension and the voltage of the secondary battery, and the data together with the identification symbol of the secondary battery Accumulate on the table,
Means for judging the degree of deterioration of the secondary battery from the data in the data table relating to the secondary battery and the data of the degree of deterioration measured in advance for the same type of secondary battery of the secondary battery. A rechargeable battery charging device. The secondary battery charging device according to any one of claims 7 to 9 ,
A charging device for a secondary battery, characterized in that it has means for increasing the charging current and charging if the polarization voltage measured at each charging pause is less than or equal to a predetermined ratio of the first threshold value. .

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