JP5137603B2 - Charge / discharge control method and charge / discharge control system for alkaline storage battery - Google Patents

Description

  The present invention relates to a charge / discharge control method and a charge / discharge control system for an alkaline storage battery that is effective in suppressing the memory effect.

  Demand for alkaline storage batteries such as nickel metal hydride storage batteries is expanding mainly in industrial applications such as hybrid vehicles (hereinafter referred to as HEV) and emergency power supplies. In particular, in HEV, an alkaline storage battery as a main power source needs to perform both motor drive (discharge) and storage (charge) of regenerative power from a generator. Therefore, it is necessary to always monitor the state of charge (SOC) of the alkaline storage battery and control charging and discharging according to the SOC.

  In an alkaline storage battery using nickel hydroxide as the positive electrode active material, a memory effect occurs when a cycle in which complete discharge (SOC is almost 0%) or complete charge (SOC is almost 100%) is not repeated. That is, the electromotive force value with respect to the remaining capacity of the storage battery is lowered, and the capacity is apparently reduced. In order to suppress the memory effect, it is desirable to perform charge / discharge in a wide SOC region in an alkaline storage battery.

  However, in applications such as HEV, charging / discharging with a large current is performed continuously and instantaneously. Therefore, when connecting a plurality of alkaline storage batteries each having a capacity difference, it is necessary to avoid that the storage battery having the smallest capacity enters overcharge or overdischarge. Therefore, an upper limit SOC (charge end voltage) for prohibiting charging and a lower limit SOC (discharge end voltage) for prohibiting discharge are provided so that complete discharge and full charge are not performed, and charge / discharge is performed between both end voltages. The method of controlling is adopted.

In order to suppress the memory effect, various techniques have been conventionally proposed. For example, Patent Document 1 discloses a method of widening a charge / discharge region by calculating a battery voltage from a battery discharge current to obtain an estimated battery voltage and correcting a discharge lower limit voltage based on the battery voltage. Yes.
JP 2001-186682 A

  However, when the discharge end voltage is lowered as in Patent Document 1, the reduction of the cobalt compound contained in the positive electrode is promoted, so that the positive electrode is likely to deteriorate. Further, when the end-of-charge voltage is increased, the amount of oxygen generated from the positive electrode increases, so that the oxidation of the hydrogen storage alloy as the negative electrode active material is promoted. As a result, the reaction resistance of the negative electrode increases. That is, when the end voltage is changed, the deterioration of the battery constituent material is promoted.

  That is, if the end voltage is varied during charging / discharging of the alkaline storage battery, the durability of the battery is lowered. For this reason, it has been difficult to apply alkaline storage batteries to applications that require durability, such as HEV applications.

  Then, an object of this invention is to provide the charging / discharging control method and charging / discharging control system of an alkaline storage battery which can suppress deterioration of a battery constituent material and can suppress a memory effect.

The charge / discharge control method for an alkaline storage battery according to the present invention performs a first charge on the alkaline storage battery up to a charge end voltage preset by a first charge current, and then a second charge current smaller than the first charge current. step of performing a second charge, and, in an alkali storage battery, until the discharge end voltage set in advance by the first discharge current performs a first discharge, then the in smaller than the first discharge current second discharge current Including a step of performing two discharges.

In the present invention, a second charge, or voltage of the alkaline storage battery has reached the charge voltage again, or Ru is stopped before reaching the final charging voltage. In the present invention, the second discharge, or the voltage of the alkaline storage battery again reaches the discharge end voltage, or Ru is stopped before reaching the discharge termination voltage.

In the present invention, the charging end voltage, Ri voltage der corresponding to state of charge (SOC) 70 to 85%, the discharge end voltage, Ru voltage der corresponding to state of charge (SOC) 15~30%.

The second charging current is preferably a value of 1/10 to 1/5 of the first charging current.
The second discharge current is preferably a value of 1/10 to 1/5 of the first discharge current.

The first charging current is preferably a current value of 0.1 to 0.3 hour rate.
The first discharge current is preferably a current value of 0.03 to 0.3 hour rate.

In a preferred aspect of the present invention, the end-of-charge voltage is set according to the first charging current or the battery temperature.
In a preferred embodiment of the present invention, the discharge end voltage is set according to the first discharge current or the battery temperature.
The time for performing the second charge is preferably 1 to 20 seconds.
The time for performing the second discharge is preferably 1 to 20 seconds.

  The charge / discharge control system of the present invention includes an alkaline storage battery, voltage detection means for detecting the voltage of the alkaline storage battery, temperature detection means for detecting the temperature of the alkaline storage battery, preset charge end voltage and discharge end voltage. Storage means for storing, and when the voltage detected by the voltage detection means reaches the end-of-charge voltage, charge control means for stopping the first charge and performing the second charge with a second charge current smaller than the first charge current, And / or discharge control means for stopping the first discharge and performing the second discharge with a second discharge current smaller than the first discharge current when the voltage detected by the voltage detection means reaches a discharge end voltage.

  In a preferred aspect of the present invention, the storage means stores a plurality of charge end voltages, and the charge control means selects an appropriate charge end voltage from the plurality of charge end voltages according to the temperature of the alkaline storage battery. .

  In a preferred aspect of the present invention, the storage means stores a plurality of discharge end voltages, and the discharge control means selects an appropriate discharge end voltage from the plurality of discharge end voltages according to the temperature of the alkaline storage battery. .

  In a preferred aspect of the present invention, the charge / discharge control system further includes a current detection unit that detects a current from the alkaline storage battery, the storage unit stores a plurality of charge end voltages, and the charge control unit includes: An appropriate charge end voltage is selected from a plurality of charge end voltages according to the first charging current detected by the current detecting means.

  In a preferred aspect of the present invention, the charge / discharge control system further includes current detection means for detecting current from the alkaline storage battery, the storage means stores a plurality of discharge end voltages, and the discharge control means includes An appropriate discharge end voltage is selected from a plurality of discharge end voltages according to the first discharge current detected by the current detecting means.

  ADVANTAGE OF THE INVENTION According to this invention, while suppressing the deterioration of the constituent material of an alkaline storage battery, a memory effect can be suppressed.

  The present invention includes a step of performing a first charge on an alkaline storage battery up to a charge end voltage set in advance with a first charge current, and then performing a second charge with a second charge current smaller than the first charge current; and And / or an alkaline storage battery including a step of performing a first discharge to a discharge end voltage set in advance with a first discharge current and then performing a second discharge with a second discharge current smaller than the first discharge current. Provided is a charge / discharge control method for a storage battery.

  In charge / discharge of an alkaline storage battery, if the charge end voltage is increased or the discharge end voltage is lowered, the constituent materials of the battery are deteriorated. Therefore, in the charge / discharge control method of the present invention, after performing the first charge and / or the first discharge, the second charge and / or the second discharge is performed with a second current smaller than the first current, whereby the battery Deterioration of the constituent materials is suppressed. Thereby, since it is not necessary to change the end voltage, the memory effect can be suppressed without deteriorating the durability of the alkaline storage battery.

  The charge / discharge control method of the present invention will be described with reference to the drawings. FIG. 1 is a graph showing the relationship between the charge / discharge current and the end voltage in one embodiment of the charge / discharge control method of the present invention. In FIG. 1, the discharge end voltage (lower limit end voltage) is a voltage equivalent to SOC 20%, and the charge end voltage (upper limit end voltage) is a voltage equivalent to SOC 80%.

(1) Charging of alkaline storage battery Charging is performed until the voltage of the alkaline storage battery reaches the upper limit end voltage at a relatively large first charging current I3 (for example, a current value of 0.1 to 0.3 hour rate) (first charging). The current value of the X time rate is a current value at which the SOC becomes 0% to 100% (or 100% to 0%) in X time. When the voltage of the alkaline storage battery reaches the upper limit end voltage, the first charging is stopped. At this time, due to the polarization, the SOC of the battery does not actually reach 80%, so the voltage decreases. Thereafter, charging is performed with a second charging current I4 smaller than the first charging current I3 (second charging). By performing the second charging, the polarization is reduced, and charging up to SOC 80% becomes possible.

(2) Discharge of alkaline storage battery Discharge is performed until the voltage of the alkaline storage battery reaches the lower limit end voltage at a relatively large first discharge current I1 (for example, a current value of 0.03 to 0.3 hour rate) (first Discharge). When the voltage of the alkaline storage battery reaches the lower limit end voltage, the first discharge is stopped. At this time, due to the polarization, the SOC of the battery does not actually reach 20%, so the voltage rises. Thereafter, discharge is performed with a second discharge current I2 smaller than the first discharge current I1 (second discharge). By performing the second discharge, the polarization becomes small, and discharge up to SOC 20% becomes possible.

  By performing charging and / or discharging as described above, the memory effect of the alkaline storage battery can be effectively suppressed without changing the end voltage. That is, the charge / discharge control system can be operated efficiently.

  The effect of the present invention can be obtained by performing at least one of discharging and charging by the above control method, but the memory effect can be further effectively suppressed by performing both discharging and charging by the above control method. Can do.

From the viewpoint of suppressing deterioration of the constituent materials of the alkaline storage battery, the second charging is preferably stopped before the voltage of the alkaline storage battery reaches the end-of-charge voltage again or before reaching the end-of-charge voltage. When the second charge is stopped before reaching the charge end voltage V ₁ , the voltage v ₁ for stopping the second charge is, for example, 95% or more of the charge end voltage V ₁ (0.95 × V ₁ ≦ v ₁ ). It is preferable that When the voltage v ₁ for stopping the second charge exceeds the charge end voltage V ₁ , the constituent materials may be deteriorated. On the other hand, if the voltage v ₁ for stopping the second charge is smaller than 95% of the charge end voltage V ₁ , the memory effect may not be sufficiently suppressed.

The second discharge is preferably stopped before the voltage of the alkaline storage battery reaches the discharge end voltage again or reaches the discharge end voltage from the viewpoint of suppressing deterioration of the constituent material of the alkaline storage battery. When the second discharge is stopped before reaching the discharge end voltage V ₂ , the voltage v ₂ for stopping the second discharge is, for example, 105% or less of the discharge end voltage V ₂ (v ₂ ≦ 1.05 × V ₂ ). It is preferable that If the voltage v ₂ for stopping the second discharge is smaller than the discharge end voltage V ₂ , the constituent materials may be deteriorated. On the other hand, if the voltage v ₂ for stopping the second discharge exceeds 105% of the discharge end voltage V ₂ , the memory effect may not be sufficiently suppressed.

  The time for performing the second charge is not particularly limited as long as the voltage of the alkaline storage battery reaches a predetermined voltage. For example, the effect of the present invention can be obtained even if the time for performing the second charge is several seconds. It is done. Especially, it is preferable that the time which performs 2nd charge is 1 to 20 seconds from a viewpoint of making the effect which suppresses the fall of the output of a charging / discharging control system larger.

  The time for performing the second discharge is not particularly limited as long as the voltage of the alkaline storage battery reaches a predetermined voltage. For example, the effect of the present invention can be obtained even if the time for performing the second discharge is several seconds. It is done. Especially, it is preferable that the time which performs a 2nd discharge is 1 to 20 second from a viewpoint of making the effect which suppresses the fall of the output of a charging / discharging control system larger, for example.

  The second charge or the second discharge may not be performed every charge / discharge cycle. For example, even when the second charge or the second discharge is performed every tens of cycles in the charge / discharge cycle of the alkaline storage battery, the memory effect can be effectively reduced. Especially, it is preferable to perform 2nd charge or 2nd discharge for every 5-50 cycles from a viewpoint of making the effect which suppresses the fall of the output of a charge / discharge control system larger.

  The end-of-discharge voltage is preferably a voltage corresponding to a state of charge (SOC) of 15 to 30%. When the discharge end voltage is a voltage corresponding to SOC 15% or more, the reduction of cobalt contained in the positive electrode can be sufficiently suppressed. On the other hand, when the discharge end voltage is a voltage corresponding to an SOC of 30% or less, the memory effect can be effectively suppressed.

  The end-of-charge voltage is preferably a voltage corresponding to SOC 70 to 85%. When the charge end voltage is a voltage corresponding to SOC 70% or more, the memory effect can be effectively suppressed. On the other hand, when the end-of-charge voltage is a voltage corresponding to an SOC of 85% or less, the generation of oxygen from the positive electrode can be sufficiently suppressed.

  The second charging current may be any value as long as it is smaller than the first charging current, and can be arbitrarily changed by changing the end voltage as the cycle proceeds. Especially, it is preferable that a 2nd charging current is a value of 1/10 to 1/5 of a 1st charging current. If the second charging current is smaller than one-tenth of the first charging current, a long charging time may be required to sufficiently eliminate the memory effect. On the other hand, if the second charging current is larger than one fifth of the first charging current, the end-of-charge voltage may be reached before the memory effect is sufficiently eliminated.

  The second discharge current may be any value as long as it is smaller than the first discharge current, and the value can be arbitrarily changed by changing the end voltage with the progress of the cycle. Especially, it is preferable that a 2nd discharge current is a value of 1/10 to 1/5 of a 1st discharge current. If the second discharge current is smaller than one tenth of the first discharge current, a long discharge time may be required to sufficiently eliminate the memory effect. On the other hand, if the second discharge current is larger than one fifth of the first discharge current, the discharge end voltage may be reached before the memory effect is sufficiently eliminated.

  In a preferred aspect of the present invention, the end-of-charge voltage is set according to the first charging current or the battery temperature. When the charging current and the battery temperature are different, the polarization of the battery is also different, and the closed circuit voltage at the time of charging is also changed. That is, the conditions under which the constituent materials of the battery are likely to deteriorate and the voltage range in which the memory effect can be suppressed are different. Therefore, the memory effect can be more effectively suppressed by performing the control at the end-of-charge voltage suitable for each condition.

  In a preferred embodiment of the present invention, the discharge end voltage is set according to the first discharge current or the battery temperature. When the discharge current and the battery temperature are different, the polarization of the battery is different, and the closed circuit voltage at the time of discharge is also changed. That is, the conditions under which the constituent materials of the battery are likely to deteriorate and the voltage range in which the memory effect can be suppressed are different. Therefore, as in the case of charging, the memory effect can be more effectively suppressed by performing the control with the discharge end voltage suitable for each condition.

  A method for setting the charge end voltage and the discharge end voltage will be described. The charge end voltage and the discharge end voltage are preferably set to voltages corresponding to a predetermined SOC from the viewpoint of easy setting.

The voltage corresponding to the predetermined SOC can be quantified in percentage by the following method, for example.
A calibration curve indicating the relationship between the SOC and the voltage-current characteristic (IV value) is created in advance. If the IV value is appropriately measured and collated with a calibration curve, the SOC can be monitored. In addition, by correcting the SOC monitored by the integrated value of charge / discharge current (a theoretical SOC can be calculated), quantification by percentage of SOC can be performed with higher accuracy.

  Next, an alkaline storage battery, a voltage detection means for detecting the voltage of the alkaline storage battery, a temperature detection means for detecting the temperature of the alkaline storage battery, a storage means for storing preset charge end voltage and discharge end voltage, and charging A charge / discharge control system having control means and / or discharge control means will be described.

When the voltage detected by the voltage detection means reaches the charge end voltage, the charge control means stops the first charge and performs the second charge with a second charge current smaller than the first charge current.
The discharge control means stops the first discharge when the voltage detected by the voltage detection means reaches the discharge end voltage, and performs the second discharge with a second discharge current smaller than the first discharge current.

  FIG. 2 is a block diagram showing an example of a charge / discharge control system according to the present invention. The charge / discharge control system 10 includes a main power supply, voltage detection means, temperature detection means, storage means, charge control means and / or discharge control means.

The main power supply 1 in FIG. 2 includes a plurality of alkaline storage batteries, but may include a single alkaline storage battery. The main power supply 1 is connected to a voltage sensor 2 as voltage detection means and a temperature sensor 3 as temperature detection means. The storage unit 4 that is a storage unit stores each end voltage of the main power supply 1 and the relationship between the SOC of the main power supply 1 and (IV value). A control unit 5 including a charge control unit and a discharge control unit is connected to the storage unit 4. Although not shown, the charge / discharge control system 10 may include a current sensor as current detection means.
The voltage of the main power source 1 measured by the voltage sensor 2 and the temperature of the main power source 1 measured by the temperature sensor 3 are transmitted to the control unit 5.

  An operation of the charge / discharge control system 10 when charging is described. The controller 5 sets an appropriate charge end voltage according to the battery surface temperature detected by the temperature sensor 3 and the first charging current detected by a current sensor (not shown). When the voltage detected by the voltage sensor 5 reaches the charge end voltage, the control unit 5 stops the first charge. Thereafter, the control unit 5 performs the second charging with a second charging current smaller than the first charging current until the voltage reaches a predetermined value.

  An operation of the charge / discharge control system 10 when discharging is described. The controller 5 sets an appropriate discharge end voltage according to the battery surface temperature detected by the temperature sensor 3 and the first discharge current detected by a current sensor (not shown). When the voltage detected by the voltage sensor 5 reaches the discharge end voltage, the control unit 5 stops the first discharge. Thereafter, the control unit 5 performs the second discharge with a second discharge current smaller than the first discharge current until the voltage reaches a predetermined value.

  In a preferred aspect of the present invention, the storage means stores a plurality of end-of-charge voltages. At this time, the charge control means selects an appropriate charge end voltage from a plurality of charge end voltages in accordance with the first charge current and / or the temperature of the alkaline storage battery.

  In a preferred aspect of the present invention, the storage means stores a plurality of discharge end voltages. At this time, the discharge control means selects an appropriate discharge end voltage from a plurality of discharge end voltages according to the first discharge current and / or the temperature of the alkaline storage battery.

  The main power supply 1 is charged by a generator (not shown). For example, for HEV applications, it is common to use an inverter that can convert kinetic energy of an internal combustion engine or frictional energy at the time of stopping into a charging current as a generator. In addition, it is efficient to use this inverter when converting electrical energy into kinetic energy during discharge.

  The alkaline storage battery includes a positive electrode, a negative electrode, a separator, and an alkaline electrolyte. Although the kind of alkaline storage battery is not specifically limited, For example, a nickel hydrogen storage battery, a nickel cadmium storage battery, etc. are mentioned.

  The positive electrode of the alkaline storage battery includes a positive electrode active material as an essential component, and includes a conductive material and other additives as optional components. An example of the positive electrode active material is nickel hydroxide. Examples of the conductive material include metallic cobalt and cobalt compounds. Examples of the cobalt compound include cobalt oxide and cobalt hydroxide. Examples of other additives include rare earth compounds and zinc oxide. A positive electrode is obtained by mixing these and filling the three-dimensional metal porous body or applying the two-dimensional metal porous body.

  The negative electrode of an alkaline storage battery contains a negative electrode active material as an essential component and an additive as an optional component. In the case of a nickel metal hydride storage battery, a hydrogen storage alloy is used as the negative electrode active material. In the case of a nickel cadmium storage battery, cadmium or a cadmium compound is used as the negative electrode active material. Examples of the additive include a carbon material and a binder. A negative electrode can be obtained by mixing these and filling the three-dimensional metal porous body or coating the two-dimensional metal porous body.

As the separator, a nonwoven fabric made of polyolefin resin or the like can be used.
For example, an alkaline aqueous solution such as an aqueous potassium hydroxide solution may be used as the electrolytic solution.

  A positive electrode and a negative electrode are wound or laminated through a separator to produce an electrode group. The obtained electrode group is inserted into a battery can, and an electrolytic solution made of an alkaline aqueous solution is injected to obtain an alkaline storage battery. The shape of the battery is not particularly limited, and examples thereof include a cylindrical shape and a rectangular shape.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited to a following example.

Example 1
1. Preparation of alkaline storage battery A long positive electrode containing nickel hydroxide as a positive electrode active material was prepared. In addition, a long negative electrode including a hydrogen storage alloy as a negative electrode active material was produced. The positive electrode and the negative electrode were wound through a separator made of a sulfonated polypropylene nonwoven fabric to form an electrode group. This electrode group was inserted into a cylindrical battery can having an inner diameter of 30 mm and a length of 60 mm. An aqueous potassium hydroxide solution was poured into the battery can as an electrolytic solution and sealed to obtain a nickel hydride storage battery having a nominal capacity of 6 Ah.

2. Production of Charge / Discharge Control System Nickel metal hydride batteries were connected in series in 12 cells to constitute a main power source.
The main power source 1, voltage sensor 2, temperature sensor 3, storage unit 4 and control unit 5 were connected as shown in FIG.

3. Charge / Discharge Control of Charge / Discharge Control System For the charge / discharge control system, the first discharge was set to 30A (corresponding to 0.2 hour rate), and the first discharge was performed until the discharge end voltage corresponding to SOC 20% was reached. . Thereafter, the second discharge current was set to 5 A, and the second discharge was performed until the discharge end voltage corresponding to SOC 20% was reached. The second discharge time was 20 seconds.

  After performing the above-described discharge, the first charging was performed at a first charging current of 30 A (corresponding to a 0.2 hour rate) until the end-of-charge voltage corresponding to SOC 80% was reached. Thereafter, the second charge current was set to 5 A, and the second charge was performed until the charge end voltage corresponding to SOC 80% was reached. The second charging time was 20 seconds.

  With this charge / discharge cycle as one cycle, 1000 cycles of charge / discharge were performed under the condition where the battery surface temperature was 25 ° C.

<< Examples 2-3 and Reference Examples 1-2 >>
A charge / discharge cycle was performed in the same manner as in Example 1 except that the end-of-discharge voltage was set to voltages corresponding to SOC 15%, 30%, 10%, and 35%, respectively.

<< Examples 4 to 5 and Reference Examples 3 to 4 >>
A charge / discharge cycle was performed in the same manner as in Example 1 except that the end-of-charge voltage was set to a voltage corresponding to SOC 70%, 85%, 65%, and 90%.

Example 6
A charge / discharge cycle was performed in the same manner as in Example 1 except that the time for performing the second charge and the second discharge was 5 seconds.

<< Example 7 >>
A charge / discharge cycle was performed in the same manner as in Example 1 except that the second charge and the second discharge were performed once every 20 cycles.

Example 8
Both the first charging current and the first discharging current were set to 50A. Further, a voltage corresponding to SOC 80% when the first charging current is assumed to be 30A is defined as a charge end voltage, and a voltage corresponding to SOC 20% when the first discharge current is assumed to be 30A is defined as a discharge end voltage. The charge / discharge cycle was performed in the same manner as in Example 1.

Example 9
Both the first charging current and the first discharging current were set to 50A. Further, a voltage corresponding to SOC 80% when the first charging current is 50 A is set as a charge end voltage, and a voltage corresponding to SOC 20% when the first discharge current is 50 A is set as a discharge end voltage. A charge / discharge cycle was carried out in the same manner as in Example 1.

<< Example 1 0 >>
The battery surface temperature was 45 ° C. Further, a voltage corresponding to SOC 80% when the battery surface temperature is assumed to be 25 ° C. is defined as a charge end voltage, and a voltage corresponding to SOC 20% when the battery surface temperature is assumed to be 25 ° C. is defined as a discharge end voltage. The charge / discharge cycle was performed in the same manner as in Example 1.

<< Example 1 1 >>
The battery surface temperature was 45 ° C. Furthermore, the voltage corresponding to SOC 80% when the battery surface temperature is 45 ° C. is defined as a charge end voltage, and the voltage corresponding to SOC 20% when the battery surface temperature is 45 ° C. is defined as a discharge end voltage. A charge / discharge cycle was carried out in the same manner as in Example 1.

<< Comparative Example 1 >>
A charge / discharge cycle was performed in the same manner as in Example 1 except that the second charge and the second discharge were not performed.

<< Comparative Example 2 >>
A charge / discharge cycle was performed in the same manner as in Example 9 except that the second charge and the second discharge were not performed.

<< Comparative Example 3 >>
Except that was not performed second charging and second discharging was subjected to a charge-discharge cycles in the same manner as in Example 1 1.

<< Comparative Example 4 >>
The second charge and the second discharge were not performed. Further, the charge / discharge cycle was performed in the same manner as in Example 1 except that the discharge end voltage was set to a voltage corresponding to SOC 20% and the discharge end voltage was decreased by 0.100 V every 50 charge / discharge cycles.

<< Comparative Example 5 >>
The second charge and the second discharge were not performed. Further, a charge / discharge cycle was performed in the same manner as in Example 1 except that the charge end voltage was set to a voltage corresponding to SOC 80% and the charge end voltage was increased by 0.100 V every 50 cycles of charge / discharge.

In the above examples and comparative examples, in the initial state, the IV values at every SOC, current value, and temperature were measured, and a calibration curve was created.
The IV value at the time of charging / discharging was measured, the SOC was monitored and converted into a percentage, and reflected in the control. A part of SOC and IV value in each condition is shown to Tables 1-3.

(1) Evaluation of memory effect For each battery after 1000 cycles, the discharge capacity from the end-of-charge voltage to the end-of-discharge voltage was evaluated. When the discharge capacity is less than 2 Ah, the memory effect is “significant”. When the discharge capacity is 2 Ah or more and less than 3 Ah, the memory effect is “Yes”. When the discharge capacity is 3 Ah or more and less than 3.5 Ah, the memory effect is “A little”. A memory effect of “5 Ah or more” was set to “None”.

(2) Evaluation of battery capacity After performing (1), the battery temperature was 25 ° C., the current value was 3 A, and discharging was performed until the voltage of the main power source reached 12V. Thereafter, the following charge / discharge test was performed for 3 cycles, and the discharge capacity at the third cycle was defined as the battery capacity of the main power source. Here, the discharge capacity of 95% or more of the initial capacity was “equivalent”, the discharge capacity of 90% or more and less than 95% was “slightly reduced”, and the discharge capacity was less than 90% “reduced”.
Charging-2.4 hours at 3A Pause-1 hour Discharge-Until voltage reaches 12V at 3A

(3) Output test After charging the charge / discharge control system after performing (2) at 3A for 1 hour, the following four types of charge / discharge were performed.
Charge / Discharge a: 20 seconds at Discharge-6A, 5 minutes pause, Charge-6A 20 seconds, 5 minutes pause Charge / Discharge b: 20 seconds at Discharge-18A, 5 minutes pause, 20 seconds at Charge-18A Charging / discharging c: 20 seconds at discharging-36A, 5 minutes at resting, 20 seconds at charging-36A, 5 minutes at resting Charging / discharging d: 20 seconds at discharging-60A, 5 minutes at resting, charging-60A 20 seconds, 5 minutes pause

  In these four types of discharges, the amount of voltage drop VA 10 seconds after the start of discharge is read, and this VA is divided by each current value to calculate DCIR (internal resistance value). The difference of internal resistance of each charge / discharge control system was calculated | required on the basis of the internal resistance value of the system. Here, the difference from Example 1 was less than 1 mΩ, “equivalent”, 1 mΩ or more, less than 3 mΩ was “slightly increased”, and 3 mΩ or more was “increased”, which was used as an index of output characteristics. Tables 4 and 5 show the measurement conditions and results.

In Comparative Example 1 in which the second charge and the second discharge were not performed, a remarkable memory effect occurred. On the other hand, in each of the examples in which the second charge and the second discharge were performed, the memory effect was suppressed.
However, in Reference Example 2 where the end-of-discharge voltage was equivalent to SOC 35% and Reference Example 3 where the end-of-charge voltage was equivalent to SOC 65%, the memory effect was seen, although not as much as Comparative Example 1.
In the reference example 2 , the memory effect is caused by the fact that the deep discharge cannot be performed, and in the reference example 3 , the memory effect is caused by the fact that the deep charge cannot be performed.

In Reference Example 1 in which the end-of-discharge voltage was a voltage equivalent to SOC 10%, the internal resistance of the main power supply slightly increased and the battery capacity also decreased slightly. This is due to the fact that since the discharge has entered too deeply, the cobalt compound contained in the positive electrode is gradually eluted into the electrolytic solution, and the conductivity of the positive electrode is reduced. Furthermore, in Reference Example 4 in which the end-of-charge voltage was set to a voltage equivalent to SOC 90%, the internal resistance of the main power supply slightly increased. This is due to the fact that the amount of oxygen generated from the positive electrode is increased due to excessive charging, and the reaction resistance is increased due to the formation of an oxide film on the surface of the hydrogen storage alloy which is the active material of the negative electrode.
From the above, it was found that the discharge end voltage is preferably a voltage equivalent to SOC 15 to 30%, and the charge end voltage is preferably a voltage equivalent to SOC 70 to 80%.

In the second charging and second discharging Example 6 was carried out only for 5 seconds, and the second charging and Example 7 and the second discharge performed only once 20 cycles, but not as much as in Example 1, sufficiently memory The effect was suppressed.

A large output may be difficult to obtain during the second charge or the second discharge. However, it is also possible to shorten the time for the second charge and the second discharge as in Example 6 or reduce the number of cycles for performing the second charge and the second charge as in Example 7 , A more efficient charge / discharge control system can be obtained for use in applications requiring high output such as HEV.

In Example 8 , in which both the first charging current and the first discharging current were set to 50 A, and the charge end voltage and the discharge end voltage were not set to appropriate values, the memory effect was slightly observed as compared to Example 1. This is considered because charging / discharging was not fully performed. On the other hand, in Example 9 in which the charge end voltage and the discharge end voltage suitable for the first charge current and the first discharge current were set, the memory effect was reduced as compared with Example 8 . In Examples 8 and 9 , the first charging current and the first discharging current were both set to 50 A, but similar effects were obtained with other current values.

However, even when the charge end voltage and the discharge end voltage suitable for the first charge current and the first discharge current are set, the memory effect is remarkably generated in the comparative example 2 in which the second charge and the second discharge are not performed. It was.
From the above, it has been found that the effect of the present invention is further increased by setting the charge end voltage and the discharge end voltage according to the first charge current and the first discharge current.

The battery surface temperature of 45 ° C., the charge end voltage and discharge end voltage Example 1 0 is not set to a value appropriate to the internal resistance of the main power supply was slightly increased. This is presumably because the oxygen generation overvoltage decreased and the oxygen generation amount increased. On the other hand, in Example 1 1 was set charge voltage and discharge end voltage suitable for the battery surface temperature, increase in the internal resistance of the main power than Example 1 0 was suppressed. In Example 1 0 and 1 1, although the battery surface temperature and 45 ° C., were obtained similar effects on other cell surface temperature.

However, even when the charge end voltage and the discharge end voltage suitable for the battery surface temperature were set, in Comparative Example 3 in which the second charge and the second discharge were not performed, the memory effect was remarkably generated.
From the above, it was found that the effect of the present invention is further increased by setting the charge end voltage and the discharge end voltage according to the battery surface temperature.

  In Comparative Example 4 in which the second charge and the second discharge were not performed and the end-of-discharge voltage was reduced by 0.100 V every 50 cycles from the voltage corresponding to SOC 20%, although the memory effect was suppressed, The increase in internal resistance and the decrease in capacity were remarkable.

Further, in Comparative Example 5 in which the second charge and the second discharge were not performed and the charge end voltage was increased by 0.100 V every 50 cycles from the voltage corresponding to SOC 80%, the increase in the internal resistance of the main power supply was significant. .
From the above, it was found that the charge end voltage and the discharge end voltage are preferably not changed.

  According to the charge / discharge control method of the present invention, it is possible to suppress the memory effect without suppressing the deterioration of the constituent material of the alkaline storage battery and reducing the durability. Thereby, it is possible to provide a charge / discharge control system having excellent durability and suppressing the memory effect. The application of the charge / discharge control system of the present invention is not particularly limited, but is particularly suitable for applications such as HEV, household cogeneration, and industrial use.

It is a graph which shows the relationship between the charging / discharging electric current and final voltage which concern on one Embodiment of the charging / discharging control method of this invention. It is a block diagram which shows an example of the charging / discharging control system which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main power supply 2 Voltage sensor 3 Temperature sensor 4 Memory | storage part 5 Control part 10 Charge / discharge control system

Claims (15)

An alkali storage battery, first was charged to a charge voltage set in advance by the first charging current, then the step of performing second charging with a small second charging current than the first charging current, and,
An alkali storage battery, until the discharge end voltage set in advance by the first discharge current performs a first discharge, then look including the step of performing a second discharge in the small second discharge current than the first discharge current,
The end-of-charge voltage is a voltage corresponding to a state of charge (SOC) of 70 to 85%,
The discharge end voltage is a voltage corresponding to a state of charge (SOC) of 15 to 30%,
The second charge is stopped before the alkaline storage battery voltage reaches the end-of-charge voltage again or before reaching the end-of-charge voltage;
The charge / discharge control method for an alkaline storage battery, wherein the second discharge is stopped before the voltage of the alkaline storage battery reaches the final discharge voltage again or before the final discharge voltage is reached . The second charging current, wherein a first value of 1 to 5 minutes of 10 minutes of the first charging current, charge and discharge control method of an alkaline storage battery of claim 1 Symbol placement. The charge / discharge control method for an alkaline storage battery according to claim 1 or 2 , wherein the second discharge current is a value of 1/10 to 1/5 of the first discharge current. Said first charging current, a current value of 0.1 to 0.3 hour rate, the charge and discharge control method of an alkaline storage battery according to any one of claims 1-3. Wherein the first discharge current, a current value of 0.03 to 0.3 hour rate, the charge and discharge control method of an alkaline storage battery according to any one of claims 1-4. The charge / discharge control method for an alkaline storage battery according to any one of claims 1 to 5 , wherein the end-of-charge voltage is set according to the first charging current or the battery temperature. The discharge end voltage, the set according to the first discharge current or battery temperature, charge and discharge control method of an alkaline storage battery according to any one of claims 1-6. The charge / discharge control method for an alkaline storage battery according to any one of claims 1 to 7 , wherein a time for performing the second charge is 1 to 20 seconds. The charge / discharge control method for an alkaline storage battery according to any one of claims 1 to 8 , wherein a time for performing the second discharge is 1 to 20 seconds. Alkaline storage battery,
Voltage detecting means for detecting the voltage of the alkaline storage battery;
Temperature detecting means for detecting the temperature of the alkaline storage battery;
Storage means for storing a preset charge end voltage and discharge end voltage;
When the voltage sensed at the voltage sensing means reaches the charge voltage, the charging control means for performing a second charge in the first charging current less than the second charging current to stop the first charge, and,
When the voltage sensed at the voltage sensing means reaches the discharge end voltage, have a discharge control means for performing a second discharge in the first discharge current smaller than the first discharge current and stops the first discharge,
The end-of-charge voltage is a voltage corresponding to a state of charge (SOC) of 70 to 85%,
The discharge end voltage is a voltage corresponding to a state of charge (SOC) of 15 to 30%,
The charge control means stops the second charge before the voltage of the alkaline storage battery reaches the charge end voltage again or reaches the charge end voltage,
It said discharge control means, the second discharge, or the voltage of the alkaline storage battery reaches the discharge end voltage again, or Ru is stopped before reaching the final discharge voltage, charge-discharge control system. Said storage means stores a plurality of charge voltage, the charging control means, in accordance with the temperature of the alkaline storage battery, selects the appropriate charge voltage from the plurality of charge voltage, claim 1 0 The charge / discharge control system described. Said storage means stores a plurality of discharge termination voltage, the discharge control means, in accordance with the temperature of the alkaline storage battery, to select an appropriate discharge termination voltage from the plurality of discharge end voltage, claim 1 0 or 1 1 charge and discharge control system according. Furthermore, it has a current detection means for detecting a current from the alkaline storage battery, the storage means stores a plurality of end-of-charge voltages, and the charge control means is a first detected by the current detection means. depending on the charge current, to select the appropriate charge voltage from the plurality of charge voltage, the charge and discharge control system according to claim 1 0, wherein. Furthermore, it has a current detection means for detecting a current from the alkaline storage battery, the storage means stores a plurality of discharge end voltages, and the discharge control means is a first detected by the current detection means. depending on the discharge current, to select an appropriate discharge termination voltage from the plurality of discharge end voltage, charge and discharge control system according to claim 1 0, wherein. Furthermore, it has a current detection means for detecting a current from the alkaline storage battery, the storage means stores a plurality of discharge end voltages, and the discharge control means is a first detected by the current detection means. The charge / discharge control system according to claim 13, wherein an appropriate discharge end voltage is selected from the plurality of discharge end voltages in accordance with a discharge current.

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