JP5515530B2 - Lithium secondary battery charging system - Google Patents

Description

  The present invention relates to a charging system for a lithium secondary battery.

  In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide has been strongly desired. In the automobile industry, there is a great expectation for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV), and the development of secondary batteries for motor drive that holds the key to commercialization of these is thriving. Has been done.

  As a secondary battery for driving a motor, it is required to have extremely high output characteristics and high energy as compared with a consumer lithium ion secondary battery used for a mobile phone, a notebook personal computer or the like. For this reason, lithium ion secondary batteries having the highest theoretical energy among all the batteries are attracting attention and are currently being developed.

  Generally, when a lithium ion secondary battery is charged using a pulse charging method, it can be fully charged in a short time. However, there is a problem that the battery deteriorates because the voltage of the battery exceeds the specified voltage during pulse charging.

  As a prior art, in order to avoid the deterioration of the battery due to the pulse charging method, there is a technique of detecting the ambient temperature and changing the set voltage when performing pulse charging according to the ambient temperature (Cited document 1).

JP 2001-16795 A

  However, since the battery resistance varies depending on the state of charge of the battery, the conventional technology has a problem that the deterioration of the battery is accelerated depending on the state of charge.

In order to solve the above-described problems, a charging system for a lithium secondary battery according to the present invention includes voltage change detection means and charging pulse current setting means. The voltage change detection means detects a change in the output voltage of the lithium secondary battery after charging the lithium secondary battery by applying at least one pulse current. The pulse current setting means sets a charging pulse current for charging the lithium secondary battery based on the output voltage change. Further, the voltage change detecting means is configured to provide a lithium secondary battery after the lithium secondary battery is charged with one pulse current based on a first time, a second time, and a third time after application of a predetermined pulse current. The change in the output voltage of the battery is the first voltage change from the application of the pulse current to the first time, the second voltage change from the first time to the second time, and from the second time to the third time. The charging pulse current setting means detects the third voltage change, the charging pulse current setting means, based on the first voltage change, the second voltage change, and the third voltage change, the lithium secondary by the charging pulse current Set the battery charging time .

  According to the present invention, the degree of deterioration of the secondary battery is determined based on the change in the output voltage of the secondary battery after charging the lithium secondary battery with one or more pulse currents. Then, the lithium secondary battery is charged with a charge pulse current optimized in consideration of the degree of deterioration of the secondary battery. This makes it possible to charge a lithium secondary battery in which the deterioration of the battery is suppressed.

It is a figure which shows the structure of the charging system of the lithium secondary battery which concerns on 1st-5th embodiment. It is a figure which shows the flowchart of the charging method of the lithium secondary battery using the charging system of the lithium secondary battery which concerns on 1st Embodiment. It is a figure which shows the time transition of the terminal voltage E when carrying out the electric current pulse charge of the assembled battery. It is a figure which shows the structure of the charging system with respect to each single battery cell unit. It is a figure which shows the flowchart of the charging method of the lithium secondary battery using the charging system of the lithium secondary battery which concerns on 2nd Embodiment. It is a figure which shows the flowchart of the charging method of the lithium secondary battery which concerns on 3rd Embodiment. It is a figure which shows 1st voltage change (DELTA) V1, 2nd voltage change (DELTA) V2, and 3rd voltage change (DELTA) V3 corresponding to ohmic loss resistance R1, reaction resistance R2, and mass transfer resistance R3. It is the figure which showed the time transition of the terminal voltage E of the assembled battery after 1 pulse charge. It is a figure which shows the flowchart of the charging method of the lithium secondary battery which concerns on 4th Embodiment. It is a figure which shows the relationship between SOC of a lithium secondary battery, and battery resistance R. FIG. It is a figure which shows the flowchart of the charging method of the lithium secondary battery which concerns on 5th Embodiment.

(First embodiment)
The lithium secondary battery charging system according to the first embodiment of the present invention will be described in detail. Hereinafter, as an example of a lithium secondary battery, an assembled battery in which a plurality of single battery cell units (laminated secondary battery or hyperbolic secondary battery) are connected in series will be described. Is not limited to this. In the drawings to be referred to below, the shape, thickness and the like of the components of the stacked battery are exaggerated for the purpose of facilitating understanding of the invention.

  FIG. 1 is a diagram illustrating a configuration of a charging system for a lithium secondary battery according to the present embodiment.

  A charging system 10 for a lithium secondary battery according to the present embodiment includes an assembled battery (lithium secondary battery) 100, a voltage sensor (voltage change detecting means) 110, a constant current power source (charging pulse current setting means) 120, and a switch (charging). Pulse current setting means) 130, current sensor 140, temperature sensor (temperature detection means) 160, high-voltage relays 180a and 180b, battery control device (voltage change detection means, charge pulse current setting means, battery resistance calculation means, charge pulse current determination Means, charging pulse current correcting means) 150, and control circuit (charging pulse current setting means) 160. The lithium secondary battery charging system 10 according to the present embodiment further includes a vehicle control device 170, an inverter 190, and a motor 200.

  The voltage sensor 110 is connected between the positive and negative output terminals of the battery pack 100. Thereby, the voltage sensor 110 detects the output voltage (total voltage) of the assembled battery 100.

  The constant current power source 120 is connected to the positive output terminal of the assembled battery 100 via the switch 130. Thereby, the constant current power source 120 applies a charging current to the assembled battery 100. Here, the switch 130 is switched by a control signal from the control circuit 165 to convert the direct current supplied from the constant current power supply 120 into an alternating charge pulse current (hereinafter referred to as “charge pulse current”). That is, the constant current power supply 120 applies a charging pulse current to the assembled battery 100 together with the switch 130 and charges the assembled battery 100 with the charging pulse current. By using the pulse charging method, the assembled battery 100 can be charged in a short time.

  The current sensor 140 is connected to the positive output terminal of the assembled battery 100. Thereby, the current sensor 140 measures the discharge current and the charge current of the assembled battery 100.

  The temperature sensor 160 is mounted on the assembled battery 100. Thereby, the temperature sensor 140 measures the temperature of the assembled battery 100. The temperature of the assembled battery 100 is measured because the battery resistance R varies depending on the temperature of the assembled battery 100. Therefore, the battery resistance R is measured with high accuracy by correcting the battery resistance R with the temperature of the assembled battery 100. Because you can. The temperature sensor 160 is preferably a battery temperature sensor or an environmental temperature sensor.

  The high-power relays 180a and 180b are provided in each wiring (for example, a high-voltage harness) that connects the positive and negative output terminals of the assembled battery 100 and the inverter 190 that is a load of the assembled battery 100, respectively. The high-power relays 180a and 180b are turned on or off based on a control signal from the battery control device 150, respectively. Thereby, the high voltage relays 180a and 180b supply the power of the assembled battery 100 to the inverter 190 when conducting, and do not supply the electric power of the assembled battery 100 to the inverter 190 when not conducting.

  The battery control device 150 includes a CPU (Central Processing Unit) 151 and a memory 152. The CPU 151 has functions as a control device and an arithmetic device. The memory 152 has a function as a storage device. The memory 152 may be composed of, for example, various RAMs (Random Access Memory), various ROMs (Read Only Memory), and a hard disk.

  The battery control device 150 controls the high power relays 180a and 180b. Further, the battery control device 150 controls the switch 130 through the control circuit 165. However, the battery control device 150 may directly control the switch 130.

  In addition, the battery control device 150 controls the constant current power source 120.

  The battery control device 150 receives the signal of the output voltage of the battery pack 100 from the voltage sensor 110 and the signal of the discharge current and the charge current of the battery pack 100 from the current sensor 140, and stores these signals at a predetermined sampling frequency. .

  In the memory 152 of the battery control device 150, an open circuit voltage (hereinafter referred to as “OCV (Open Circuit Voltage)”) and a state of charge (hereinafter referred to as “SOC (State of Charge)”) of the assembled battery 100 are stored. The relationship data and the relationship data between the temperature of the battery pack 100 and the temperature correction coefficient are stored.

  The control circuit 165 outputs a voltage pulse having a predetermined magnitude and frequency based on the control signal of the battery control device 150, and turns on / off the switch 130. The control circuit 165 may be configured using an oscillator, for example.

  The vehicle control device 170 controls a vehicle using the motor 200 as a drive source. Therefore, the vehicle control device 170 controls the battery control device 150. For example, the vehicle control device 170 can control the timing at which the battery control device 150 charges the assembled battery 100.

  The inverter 190 converts the DC voltage output from the assembled battery 100 into a three-phase AC voltage.

  Motor 200 receives a three-phase AC voltage from inverter 190 and generates torque for driving the vehicle.

  It is desirable to charge and discharge the assembled battery 100 while the inverter 190 that is a load of the assembled battery 100 is connected. That is, the electric power from the assembled battery 100 is supplied to the motor 200 via the inverter 190 when the vehicle is started or accelerated. On the other hand, when the vehicle is decelerated, the motor 200 is caused to function as a generator, and electric power obtained from the motor 200 is regenerated (that is, charged) to the assembled battery 100. Thereby, power saving can be realized.

  FIG. 2 is a diagram illustrating a flowchart of a method for charging a lithium secondary battery using the lithium secondary battery charging system according to the present embodiment. The lithium secondary battery charging system according to this embodiment will be described below with the step numbers clearly specified.

  The OCV of the assembled battery 100 is measured (S500). In order to measure the OCV of the assembled battery 100, the battery control device 150 places the high-voltage relays 180a and 180b of the assembled battery 100 in a non-conductive state and opens the output terminal of the assembled battery 100. In this state, the OCV of the assembled battery 100 can be measured by measuring the voltage (output voltage) between the output terminals of the assembled battery 100 with the voltage sensor 110.

  One pulse charge is performed (S501). That is, by causing the control circuit 165 to control the switch 130, one pulse current is generated from the direct current constant current generated by the constant current power source 120, and the assembled battery 100 is charged with the pulse current (hereinafter referred to as “one pulse charge”). Called). At this time, in order to apply the charging pulse current to the assembled battery 100, the high-voltage relays 180a and 180b are kept in a conductive state. The magnitude of the charging pulse current is preferably set so that the terminal voltage E of the assembled battery 100 when the charging pulse current is applied to the assembled battery 100 becomes the maximum value in the specification range guaranteed by the assembled battery 100. . Hereinafter, the terminal voltage E of the assembled battery 100 set in this way is referred to as a set voltage.

  The terminal voltage E of the assembled battery 100 is measured (S502). The terminal voltage E of the assembled battery 100 is measured with time from immediately after one pulse is charged in step S501 by the voltage sensor 100 connected between the terminals of the assembled battery 100. The battery control device 150 digitizes and stores the measured terminal voltage E of the assembled battery 100 at an appropriate sampling frequency.

  FIG. 3 is a diagram showing a time transition of the terminal voltage E when the assembled battery 100 is charged with current pulses.

  FIG. 3A is a diagram showing a time transition of the terminal voltage E of the assembled battery 100 when one-pulse charging is performed a plurality of times. The magnitude of the current pulse is adjusted so that the terminal voltage E of the assembled battery 100 does not exceed the set voltage. As shown in A of FIG. 3, the terminal voltage E of the assembled battery 100 approaches the set voltage by performing one-pulse charging from the state where the current is OFF (that is, the charging current is 0).

  FIG. 3B is an enlarged view of a portion before and after one-pulse charging in A of FIG. Part a of FIG. 3B corresponds to step S500, and shows the terminal voltage E of the assembled battery 100 when the charging current to the assembled battery 100 is zero. The part b corresponds to step S501 and shows the time transition of the terminal voltage E of the assembled battery 100 when one-pulse charging is performed. The part c corresponds to step S502 and shows the time transition of the terminal voltage E of the assembled battery 100 immediately after one pulse charge.

  As the deterioration of the assembled battery 100 proceeds, the change ΔV of the terminal voltage E of the assembled battery 100 after one pulse charge (hereinafter referred to as “post-charge output voltage change ΔV”) becomes larger than the normal value. That is, the post-charge output voltage change ΔV is closely related to the degree of deterioration of the assembled battery 100. Therefore, the deterioration of the battery can be suppressed by adjusting the magnitude of the charging pulse based on the post-charging output voltage change ΔV indicating the degree of deterioration of the assembled battery 100.

  A post-charge output voltage change ΔV is calculated (S503). The battery control device 150 calculates a post-charging output voltage change ΔV from the stored terminal voltage E of the assembled battery 100. The change in output voltage after charging ΔV is a change in the terminal voltage E of the battery pack 100 from the moment when the charging current of one-pulse charging is switched to 0 (that is, the moment when the switch 130 is switched from ON to OFF) until a predetermined time elapses Can be calculated as Here, the predetermined time may be set empirically. For example, the predetermined time can be set when the change per second of the terminal voltage E of the assembled battery 100 falls within a certain range.

  The post-charge output voltage change ΔV is compared with a threshold voltage (S504). That is, the post-charging output voltage change ΔV calculated in step S503 is compared with the threshold voltage stored in advance in the battery control device 150. The threshold voltage can be, for example, the largest post-charge output voltage change ΔV value in the specification range of the post-charge output voltage change ΔV of the assembled battery 100.

  When the post-charge output voltage change ΔV is equal to or lower than the threshold voltage (S505, Yes), one-pulse charging is performed with the same charging current as that in step S501 (S507). In this case, it is considered that the deterioration of the assembled battery 100 is not progressing.

  If the post-charging output voltage change ΔV is not less than or equal to the threshold voltage (S505, No), that is, if the post-charging output voltage change ΔV exceeds the threshold voltage, the charging pulse current is corrected (S506). When the post-charge output voltage change ΔV exceeds the threshold voltage, it is considered that the battery pack 100 is being deteriorated. Therefore, after that, the magnitude of the charging pulse current is corrected to be small, and one-pulse charging is performed with the corrected charging pulse current (S507). Thereby, charging of the assembled battery 100 which suppressed the deterioration of the battery for a short time can be realized.

  In step S507, one-pulse charging is performed, but the assembled battery 100 may be charged with a plurality of charging pulse currents.

  The charge pulse current can be corrected as follows, for example. The relationship between the output voltage change ΔV after charging and the pulse current value that does not cause deterioration of the assembled battery 100 is obtained in advance and stored in the battery control device 150. Then, a charge pulse current that does not cause deterioration of the assembled battery 100 can be obtained by comparing the above relationship with the measured post-charge output voltage change ΔV, and this can be used as a corrected charge pulse current. The relationship between the post-charge output voltage change ΔV and the charge pulse current value that does not cause deterioration of the assembled battery 100 may be obtained, for example, by testing a plurality of assembled batteries 100.

  It is determined whether or not the assembled battery 100 has reached a predetermined charge amount (S508). When the assembled battery 100 has a predetermined charge amount (S508, Yes), this flowchart ends. When the assembled battery 100 does not have the predetermined charge amount (S508, No), the process returns to step S502 again, and the subsequent flow is performed.

  In addition, in this embodiment, although the output voltage of the assembled battery 100 whole is detected, you may detect the output voltage of each single battery cell unit 101 which comprises the assembled battery 100. FIG. FIG. 4 is a diagram showing a configuration of a charging system for each single battery cell unit 101.

  The configuration of the charging system in FIG. 4 differs from the configuration in FIG. 1 in that voltage sensors 110A, 110B, 110C, and 110D are provided for each unit cell unit 101 that constitutes the assembled battery 100. In addition, individual switches 210 </ b> A, 210 </ b> B, 210 </ b> C, and 210 </ b> D are provided between the positive electrode terminal of each unit cell unit 101 and the current sensor 140, respectively. According to the configuration of the charging system shown in FIG. 4, (a) measurement of the output voltage of each unit cell unit, (b) application of an independent charging pulse current to each unit cell unit, (c) each unit cell Measurement of the charge / discharge current of the cell unit becomes possible. That is, by turning on any one of the individual switches 210A, 210B, 210C, and 210D, the charging system for the assembled battery 100 can function as a charging system for the selected single battery cell unit 101.

  Since the other components of the charging system for each single battery cell unit shown in FIG. 4 are the same as those in FIG. 1, description of these components is omitted.

Below, the effect of the charging system of the lithium secondary battery which concerns on this embodiment is shown.
・ Determining the degree of deterioration of the lithium secondary battery based on the change in the output voltage of the battery after charging the lithium secondary battery with one or more pulse currents, and using the charge pulse current optimized in consideration of the degree of deterioration Charge the secondary battery. Thereby, charge of the lithium secondary battery which suppressed degradation of a battery is realizable.
(Second Embodiment)
Next, a second embodiment of the lithium secondary battery charging system according to the present invention will be described in detail.

  Both the present embodiment and the first embodiment are based on the change in the output voltage of the battery after charging the lithium secondary battery with one or more charging pulse currents (the change in output voltage after charging ΔV). The same is true in that the degree of deterioration is determined and the charging pulse current is corrected based on the degree of deterioration. However, in the present embodiment, the battery resistance value R is calculated from the output voltage change ΔV after charging and the charging current to the lithium secondary battery, the degree of deterioration of the lithium secondary battery is determined based on the battery resistance value R, and This is different from the first embodiment in that the charging current is corrected based on the degree of deterioration.

  Hereinafter, although the charging system of the lithium secondary battery according to the present embodiment will be described, the description overlapping the first embodiment will be omitted.

  FIG. 5 is a diagram showing a flowchart of a method for charging a lithium secondary battery according to the present embodiment. The lithium secondary battery charging method according to the present embodiment can use the lithium secondary battery charging system shown in FIG. 1 as in the first embodiment.

  The lithium secondary battery charging system according to this embodiment will be described below with the step numbers clearly specified.

  As in the first embodiment, the OCV of the battery pack 100 is measured (S700) and one-pulse charging is performed (S701). After charging one pulse, the terminal voltage E of the assembled battery 100 is measured (S702) and stored in the battery control device 150 over time. The post-charging output voltage change ΔV is calculated from the terminal voltage E of the assembled battery 100 stored in the battery control device 150 (S703).

  The battery resistance R of the assembled battery 100 is calculated (S704). The battery resistance R is calculated by dividing the output voltage change ΔV after charging by the charging pulse current value I as in the following formula (1). Here, the charge pulse current value I means the amplitude of the charge pulse current.

  As the charging pulse current value I, a current value set in the constant current power source 120 can be used. However, the current value measured by the current sensor 140 may be used. When the current value measured by the current sensor 140 is used, when the terminal voltage E of the assembled battery 100 is measured in step S702, the pulse current for charging the assembled battery 100 is also measured, and digital at an appropriate sampling frequency. And stored in the battery control device 150 over time. Then, the pulse current value I can be calculated from the charging pulse current stored in the battery control device 150.

  When the deterioration of the assembled battery 100 proceeds, the battery resistance R increases. That is, the battery resistance R is closely related to the degree of deterioration of the assembled battery 100. Therefore, the deterioration of the battery can be suppressed by adjusting the magnitude of the charging pulse current based on the battery resistance R indicating the degree of deterioration of the assembled battery 100.

  The battery resistance R of the assembled battery 100 is compared with a threshold value (S705). That is, the battery resistance R calculated in step S704 is compared with the threshold value stored in advance in the battery control device 150. For example, the threshold value may be the largest value of the battery resistance R in the specification range of the battery resistance R of the assembled battery 100.

  When the battery resistance R is equal to or less than the threshold value (S706, Yes), one pulse charging is performed with the same charging pulse current as that in step S701 (S708). In this case, it is considered that the deterioration of the assembled battery 100 is not progressing.

  When the battery resistance R is not less than or equal to the threshold value (S706, No), that is, when the battery resistance R exceeds the threshold value, the charging pulse current is corrected (S707). When the battery resistance R exceeds the threshold value, it is considered that the battery pack 100 is being deteriorated. Therefore, the magnitude of the charging pulse current is corrected to be small, and one pulse charging is performed with the corrected charging pulse current (S708). Thereby, charging of the assembled battery 100 which suppressed the deterioration of the battery for a short time can be realized.

  The charge pulse current can be corrected as follows, for example. Data on the relationship between the battery resistance R and the charge pulse current value that does not cause deterioration of the assembled battery 100 is acquired in advance and stored in the battery control device 150. Then, by comparing the data with the measured battery resistance R, a charging pulse current that does not cause deterioration of the assembled battery 100 can be obtained, and this can be used as a corrected charging pulse current. The relationship between the battery resistance R and the charge pulse current value that does not cause deterioration of the assembled battery 100 may be acquired, for example, by testing a plurality of assembled batteries 100.

  When the assembled battery 100 has a predetermined charge amount (S709, Yes), this flowchart ends. When the assembled battery 100 does not have the predetermined charge amount (S709, No), the process returns to step S702 again, and the subsequent flow is performed.

Below, the effect of the charging system of the lithium secondary battery which concerns on this embodiment is shown.
-Determining the degree of deterioration of the lithium secondary battery based on the battery resistance obtained from the change in the output voltage of the battery after charging the lithium secondary battery with one or more charging pulse currents and the charging pulse current value, and the deterioration The lithium secondary battery is charged with a charge pulse current optimized in consideration of the degree. Thereby, charge of the lithium secondary battery which suppressed degradation of a battery is realizable.
(Third embodiment)
Next, a third embodiment of the lithium secondary battery charging system according to the present invention will be described in detail.

  Both the present embodiment and the first embodiment are similar in that the deterioration of the lithium secondary battery is determined based on the post-charge output voltage change ΔV, and the charge pulse current is set based on the post-charge output voltage change ΔV. It is. However, this embodiment is different in that the output voltage change ΔV after charging is measured by dividing it into a plurality of different time zones, and the charging pulse current and the charging time are set based on the voltage change in each time zone.

  Hereinafter, although the charging system of the lithium secondary battery according to the present embodiment will be described, the description overlapping the first embodiment will be omitted.

  FIG. 6 is a diagram showing a flowchart of a method for charging a lithium secondary battery according to the present embodiment. The lithium secondary battery charging method according to the present embodiment can use the lithium secondary battery charging system shown in FIG. 1 as in the first embodiment.

  The lithium secondary battery charging system according to this embodiment will be described below with the step numbers clearly specified.

  As in the first embodiment, the OCV of the assembled battery 100 is measured (S800), and one-pulse charging is performed (S801). After charging one pulse, the terminal voltage E of the assembled battery 100 is measured (S802) and is stored in the battery control device 150 over time.

  A change in the terminal voltage E of the assembled battery 100 every predetermined time after one pulse charge, that is, a first voltage change ΔV1, a second voltage change ΔV2, and a third voltage change VΔ3 are calculated (S803).

  The first voltage change ΔV1, the second voltage change ΔV2, and the third voltage change VΔ3 will be described.

The component of the battery resistance R of the assembled battery 100 obtained in the second embodiment can be classified into the following three components.
1. Ohm loss resistance R1 due to current collector, electrolyte, and electrode area
2. Reaction resistance R2 caused by difficulty in battery reaction
3. Mass transfer resistance R3 caused by difficulty in movement of lithium ions in battery
The above three resistance components are resistances generated for different reasons, and are caused by phenomena having different time constants. Therefore, the battery resistance R can be measured with the above three components by dividing and measuring the output voltage change ΔV after charging into appropriate time zones. The first voltage change ΔV1, the second voltage change ΔV2, and the third voltage change ΔV3 are voltage drops caused by the ohmic loss resistance R1, the reaction resistance R2, and the mass transfer resistance R3, respectively, and are expressed by the following equation (2). There is a correspondence.

Here, I indicates a charge pulse current value.

  When the deterioration of the assembled battery 100 progresses, any one of the ohmic loss resistance R1, the reaction resistance R2, and the mass transfer resistance R3 becomes larger than the normal value, so that the charging pulse current or the charging time is based on these resistance values. By optimizing the above, it is possible to realize the charging of the lithium secondary battery that suppresses the deterioration of the battery in a short time.

  FIG. 7 is a diagram illustrating a first voltage change ΔV1, a second voltage change ΔV2, and a third voltage change ΔV3 corresponding to the ohmic loss resistance R1, the reaction resistance R2, and the mass transfer resistance R3.

  FIG. 7A is a diagram illustrating a time transition of the terminal voltage E of the assembled battery 100 before and after one-pulse charging. FIG. 7B is a diagram illustrating a time transition of the terminal voltage E of the assembled battery 100 after one pulse charge, and is an enlarged view of a region c in FIG. 7A. As shown in FIG. 7B, when attention is paid to the inflection point of the graph, three voltage drop regions can be recognized, and these three voltage drop regions are represented by a first voltage change ΔV1, a second voltage change ΔV2, This corresponds to a region to which the third voltage change ΔV3 is applied. The ohmic loss resistance R1, the reaction resistance R2, and the mass transfer resistance R3 are resistances caused by phenomena having different time constants. Therefore, the first voltage change ΔV1, the second voltage change ΔV2, and the third voltage change ΔV3 appear as the terminal voltage E of the assembled battery 100 with a specific delay time. Then, the time after one pulse charge is divided into three time zones by selecting an appropriate time, and the voltage change of the terminal voltage E of the assembled battery 100 in the time zone is measured, whereby the first voltage change ΔV1. The second voltage change ΔV2 and the third voltage change ΔV3 can be measured.

  FIG. 8 is a diagram showing a time transition of the terminal voltage E of the assembled battery 100 after one pulse charging.

  As shown in FIG. 8, the time after one pulse charge is 0.01 second (first time) after the application of the charge pulse current, and 0.01 second (first time) to 1 second (second time). Until then, it is divided into three time zones of 1 second (second time) and thereafter. Thereby, the change of the terminal voltage E of the assembled battery 100 in the three time zones can be calculated as the first voltage change, the second voltage change, and the third voltage change, respectively.

  The ohmic loss resistance R1, reaction resistance R2, and mass transfer resistance R3 of the assembled battery 100 are calculated (S804). These resistance values can be calculated by applying the above-described equation (2) to the first voltage change, the second voltage change, and the third voltage change calculated in step S803. In Formula (2), as the charging pulse current value I, the current value set in the constant current power source 120 can be used. However, the current value measured by the current sensor 140 may be used.

  The ohmic loss resistance R1, the reaction resistance R2, and the mass transfer resistance R3 of the assembled battery 100 are compared with respective threshold values (S805). That is, each resistance R1-R3 calculated in step S804 is compared with each threshold value stored in advance in battery control device 150. Each threshold value can be set to the value of the largest resistance R1 to R3 in the specification range of each resistance R1 to R3 of the assembled battery 100, for example.

  When all of the resistors R1 to R3 are equal to or less than the threshold value (S806, Yes), one-pulse charging is performed with the same charging current as that in step S801 (S808). In this case, it is considered that the deterioration of the assembled battery 100 is not progressing.

  If any one or more of the resistors R1 to R3 is not less than the threshold (No in S806), that is, if any one or more of the resistors R1 to R3 exceeds the threshold, the charging pulse current is corrected. (S807). For example, when the ohmic loss resistance R1 of the assembled battery 100 exceeds the threshold and is large, the terminal voltage E of the assembled battery 100 may suddenly increase and exceed the set voltage from the time when the charging pulse current is applied. It is conceivable to perform correction to reduce the pulse current value. Further, when the mass transfer resistance R3 of the assembled battery 100 exceeds the threshold and is large, the terminal voltage E of the assembled battery 100 may suddenly rise from the middle of charging by the charging pulse current and exceed the set voltage. It is conceivable to make corrections to shorten the charging time. In this way, by charging the charging pulse current or the charging time based on the resistance values of the resistors R1 to R3, it is possible to realize charging of the lithium secondary battery that suppresses battery deterioration in a short time.

  The charge pulse current can be corrected as follows, for example. That is, data on the relationship between the resistors R1 to R3 and the charge pulse current value that does not cause deterioration of the assembled battery 100 is acquired and stored in the battery control device 150 in advance. Then, by comparing the data and the measured battery resistance R, a charging pulse current that does not cause deterioration of the assembled battery 100 can be obtained, and this can be used as a corrected pulse current. The relationship between the battery resistance R and the charge pulse current value that does not cause deterioration of the assembled battery 100 may be acquired, for example, by testing a plurality of assembled batteries 100. The same applies to the charging time.

  When the assembled battery 100 has a predetermined charge amount (S809, Yes), this flowchart ends. When the assembled battery 100 does not have the predetermined charge amount (S809, No), the process returns to step S802 again, and the subsequent flow is performed.

Below, the effect of the charging system of the lithium secondary battery which concerns on this embodiment is shown.
・ Deterioration degree of the lithium secondary battery based on the battery resistance obtained from the change in the output voltage of the battery and the charge pulse current value in the three time zones after charging the lithium secondary battery with one or more charging pulse currents, and Determine deterioration factors. Then, the lithium secondary battery is charged with the charge pulse current and the charge time optimized in consideration of the degree of deterioration and the deterioration factor. Thereby, the charge of the lithium secondary battery which suppressed the deterioration of the battery more is realizable.
(Fourth embodiment)
Next, a fourth embodiment of the lithium secondary battery charging system according to the present invention will be described in detail.

  In both of the present embodiment and the second embodiment, the battery resistance value R is calculated from the output voltage change ΔV after charging and the charging pulse current value to the lithium secondary battery, and the lithium secondary battery is calculated from the battery resistance value R. This is the same in that the degree of deterioration of the battery is determined and the charging current is corrected based on the degree of deterioration. However, this embodiment is different from the second embodiment in that the determination and the correction are performed only when the measured SOC is smaller than 30% or larger than 90%.

  Hereinafter, although the charging system of the lithium secondary battery according to the present embodiment will be described, description overlapping with the second embodiment will be omitted.

  FIG. 9 is a diagram showing a flowchart of a method for charging a lithium secondary battery according to the present embodiment. The lithium secondary battery charging method according to the present embodiment can use the lithium secondary battery charging system shown in FIG. 1 as in the second embodiment.

  The lithium secondary battery charging system according to this embodiment will be described below with the step numbers clearly specified.

  The SOC is measured (S1100). The measurement of the SOC can be performed, for example, by measuring the OCV as in the second embodiment (S700 in FIG. 5) and comparing the data with the correlation between the OCV and the SOC stored in the battery control device 150 in advance. it can.

  When the measured SOC is smaller than 30% or larger than 90% (S1101, Yes), the charging pulse current for charging the assembled battery 100 is corrected in subsequent steps S1102 to S1108. In other cases (S1101, No), one-pulse charging is performed without correcting the charging pulse current (S1109).

  The reason why the charging current is corrected only when the SOC is smaller than 30% or larger than 90% is that the battery resistance R of the assembled battery 100 tends to be high in such a case.

  FIG. 10 is a diagram showing the relationship between the SOC of the lithium secondary battery and the battery resistance R. As shown in FIG. 10, when the SOC is smaller than 30% or larger than 90%, the battery resistance R increases. The reason for this can be considered as follows. That is, as the SOC is lower, the lithium site in the positive electrode active material is buried, so that the energy barrier for lithium insertion when the charge reaction proceeds is increased, and the battery resistance R is increased. In particular, the reaction resistance R2 and the mass transfer resistance R3 increase. On the other hand, when the SOC exceeds 90%, it becomes difficult to receive lithium ions into the negative electrode active material, and thus the reaction resistance R2 increases.

  Thus, the battery resistance R of the assembled battery 100 increases due to the SOC as well as the deterioration of the assembled battery. Therefore, when the SOC is smaller than 30% or larger than 90%, it can be considered that it is necessary to suppress the deterioration of the battery by measuring the battery resistance R and adjusting the magnitude of the charging pulse current.

  Since the correction of the charging pulse current in steps S1102 to S1108 is the same as that in the second embodiment (S702 to S707 in FIG. 5), description thereof is omitted.

  When the SOC is smaller than 30% and larger than 90%, one pulse charging (S1109) is performed with the corrected charging current until a predetermined charging amount is reached (S1110). In other cases, the charging voltage is set so that the terminal voltage E of the assembled battery 100 when the charging pulse current is applied becomes the maximum value within the specification range guaranteed by the assembled battery 100, and a predetermined charge amount (S1110), one-pulse charging (S1109) is performed.

Below, the effect of the charging system of the lithium secondary battery which concerns on this embodiment is shown.
When the SOC is smaller than 30% or larger than 90%, based on the battery resistance obtained from the change in the output voltage of the battery after charging the lithium secondary battery with one or more pulse currents and the pulse current value The lithium secondary battery is charged with the optimized charge pulse current. Thereby, the charge of the lithium secondary battery which suppressed the deterioration of the battery more is realizable.
(Fifth embodiment)
Next, a fifth embodiment of the lithium secondary battery charging system according to the present invention will be described in detail.

  In both of the present embodiment and the second embodiment, the battery resistance value R is calculated from the output voltage change ΔV after charging and the charging pulse current to the lithium secondary battery. The same is true in that the degree of deterioration is determined and the charging current is corrected based on the degree of deterioration. However, this embodiment is different from the second embodiment in that the battery resistance R is corrected by the temperature of the secondary battery.

  Hereinafter, although the charging system of the lithium secondary battery according to the present embodiment will be described, description overlapping with the second embodiment will be omitted.

  FIG. 11 is a diagram illustrating a flowchart of a method for charging a lithium secondary battery according to the present embodiment. The lithium secondary battery charging method according to the present embodiment can use the lithium secondary battery charging system shown in FIG. 1 as in the second embodiment.

  The lithium secondary battery charging system according to this embodiment will be described below with the step numbers clearly specified.

  The temperature of the battery pack 100 is measured by the temperature sensor 160 (S1300). The temperature of the assembled battery 100 may be an environmental temperature around the assembled battery, for example. Moreover, the temperature of the assembled battery 100 may be estimated from the climate data of the place where the assembled battery 100 is used, and may be corrected with the climate data.

  It is determined whether the temperature of the assembled battery 100 needs to be corrected (S1301). The battery resistance R may increase or decrease depending on the increase or decrease of the battery temperature of the lithium secondary battery. Therefore, for example, a threshold value may be provided in advance for the temperature of the assembled battery 100, and when the measured temperature of the assembled battery 100 exceeds the threshold value, it may be determined that the correction of the temperature of the assembled battery 100 is necessary.

  If it is determined that the temperature of the assembled battery 100 needs to be corrected (S1301, Yes), steps S1302 to S1311 are performed. When it is determined that correction of the temperature of the assembled battery 100 is not necessary (S1301, No), Steps S1312 to S1320 are performed. Steps S1312 to S1320 are a flow in the case where the battery resistance R is not corrected by the temperature of the assembled battery 100 and is the same as the flowchart of the method for charging the lithium secondary battery according to the second embodiment, and thus the description thereof is omitted. To do.

  When it is determined that the temperature of the assembled battery 100 needs to be corrected (S1301, Yes), one-pulse charging is performed (S1302), the terminal voltage E of the assembled battery 100 is measured (S1303), and the terminal voltage E is changed over time. The data is stored in the battery control device 150. The post-charging output voltage change ΔV is calculated from the terminal voltage E of the assembled battery 100 stored in the battery control device 150 (S1304).

  The battery resistance R of the battery pack 100 is calculated by dividing the post-charging output voltage change ΔV by the charging pulse current value I (S1305), and the calculated battery resistance R is corrected (S1306). The battery resistance R is corrected based on the temperature of the assembled battery 100 measured in step S1300. That is, for example, the temperature correction coefficient at the temperature is obtained by comparing the correlation data between the temperature of the assembled battery 100 and the temperature correction coefficient of the battery resistance R stored in advance in the battery control device 150. The battery resistance R can be corrected by multiplying the battery resistance R calculated in step S1305 by the obtained temperature correction coefficient of the battery resistance R. Here, the temperature correction coefficient may be, for example, a temperature change rate.

  The battery resistance R of the assembled battery 100 is compared with a threshold value. That is, the battery resistance R corrected in step S1306 is compared with the threshold value stored in advance in the battery control device 150. For example, the threshold value may be the largest value of the battery resistance R in the specification range of the battery resistance R of the assembled battery 100.

  When the battery resistance R is equal to or less than the threshold value (S1308, Yes), one-pulse charging is performed with the same charging current as that in step S1302 (S1210). In this case, it is considered that the deterioration of the assembled battery 100 is not progressing.

  When the battery resistance R is not less than or equal to the threshold (S1308, No), that is, when the battery resistance R exceeds the threshold, the charging pulse current is corrected (S1309). When the battery resistance R exceeds the threshold value, it is considered that the battery pack 100 is being deteriorated. Therefore, the magnitude of the charging pulse current is corrected to be small, and one pulse charging is performed with the corrected charging pulse current (S1310). Thereby, charging of the assembled battery 100 which suppressed the deterioration of the battery for a short time can be realized with higher accuracy.

  When the assembled battery 100 has a predetermined charge amount (S1311, Yes), this flowchart ends. When the assembled battery 100 does not have the predetermined charge amount (S1311, No), the process returns to step S1303 again, and the subsequent flow is performed.

Below, the effect of the charging system of the lithium secondary battery which concerns on this embodiment is shown.
-The battery resistance obtained from the change in the output voltage of the battery after charging the lithium secondary battery with one or more pulse currents and the pulse current value is corrected with the lithium secondary battery, and the lithium is recalculated based on the corrected battery resistance. Determine the degree of deterioration of the secondary battery. Then, the lithium secondary battery is charged with a charge pulse current optimized in consideration of the degree of deterioration of the lithium secondary battery. Thereby, the charging of the lithium secondary battery in which the deterioration of the battery is suppressed can be realized with high accuracy.

  As mentioned above, although several embodiment of the charging system of the lithium secondary battery which concerns on this invention was described, the lithium secondary battery which concerns on each embodiment is not limited to an assembled battery. That is, the lithium secondary battery according to each embodiment includes, for example, a battery element (minimum unit of batteries connected in series in a bipolar secondary battery), a single battery cell unit (a laminated secondary battery or a bipolar battery laminated). Type secondary battery) or battery module (a plurality of single battery cell units arranged and connected).

  The assembled battery 100 and the single battery cell unit 101 in the embodiment correspond to the lithium secondary battery of the present invention. The voltage sensor 110 and the battery control device 150 correspond to voltage change detection means. The constant current power source 120, the switch 130, the battery control device 150, and the control circuit 165 correspond to charge pulse current setting means. The temperature sensor 160 corresponds to temperature detection means. The battery control device 150 further corresponds to battery resistance calculation means, charge pulse current determination means, and charge pulse current correction means.

10 Lithium secondary battery charging system,
100 battery pack (lithium secondary battery),
101 Single cell unit (lithium secondary battery)
110, 110A, 110B, 110C, 110D Voltage sensor (voltage change detection means),
120 constant current power supply (charging pulse current setting means),
130 switch (charging pulse current setting means),
140 current sensor,
150 battery control device (voltage change detection means, charge pulse current setting means, battery resistance calculation means, charge pulse current determination means, charge pulse current correction means),
160 temperature sensor (temperature detection means),
165 control circuit (charging pulse current setting means),
170 vehicle control device,
180a, 180b High-power relay,
190 inverter,
200 motor,
210A, 210B, 210C, 210D Individual switches.

Claims (5)

Voltage change detection means for detecting a change in output voltage of the lithium secondary battery after charging the lithium secondary battery by applying at least one pulse current;
Charging pulse current setting means for setting a charging pulse current for charging the lithium secondary battery based on the output voltage change, and
The voltage change detecting unit is configured to detect the lithium after the lithium secondary battery is charged with the one pulse current based on the first time, the second time, and the third time after the application of the pulse current. The change in the output voltage of the secondary battery includes a first voltage change from the application of the pulse current to a first time, a second voltage change from the first time to the second time, and a second voltage to the third time. Detect as the third voltage change until time,
The charging pulse current setting means is configured to apply the charging pulse current to the lithium secondary battery by the charging pulse current based on the first voltage change, the second voltage change, and the third voltage change. A charging system for a lithium secondary battery, characterized by setting a charging time . The charging pulse current setting means includes
A battery resistance calculation means for calculating a first voltage change, the second voltage change, and dividing by the corresponding battery resistance to the voltage change of the third voltage change in the value of each of said one pulse current,
Charging pulse current determining means for determining the charging pulse current based on battery resistance corresponding to each voltage change ;
The lithium secondary battery charging system according to claim 1, comprising: The first time in the following 0.01 seconds, the second time is greater than 0.01 seconds, and less than one second, claim 1, wherein the third time is at least 1 second or charging system of the lithium secondary battery according to 2. The lithium secondary battery charging system according to any one of claims 1 to 3 , wherein the lithium secondary battery is charged when the SOC is smaller than 30% or larger than 90%. Temperature detecting means for detecting the temperature of the lithium secondary battery;
Charging pulse current correcting means for correcting the charging pulse current based on the temperature detected by the temperature detecting means;
Charging system of the lithium secondary battery according to any one of claims 1 to 4, characterized in that it further comprises a.

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