JP2009300362A - Soc calculation circuit, charge system, and soc calculation method - Google Patents

Abstract

An SOC calculation circuit, a charging system, and an SOC calculation capable of reducing the possibility that the SOC calculation accuracy is lowered even when the terminal voltage of the secondary battery fluctuates due to a factor other than the charge / discharge current value. Provide a method.
A current integrating unit 213 that calculates an integrated current value by integrating discharge currents, and an SOC estimating unit 214 that repeats a process of obtaining a converted value SOCK by estimating the SOC of a secondary battery from a terminal voltage Vb. And the SOC calculation unit 216 that repeats the SOC calculation process for calculating the SOC of the secondary battery based on the converted value SOCK, and the change amount of the SOC calculated by the SOC calculation unit 216 based on the integrated current value from the previous time is limited. And a limit value setting unit 215 that sets a fluctuation limit value SOCL for performing the calculation, and the SOC calculation unit 216 newly sets the difference between the previous SOC and the current SOC within the range of the fluctuation limit value SOCL. In addition, the SOC of the secondary battery was calculated.
[Selection] Figure 1

Description

  The present invention relates to an SOC calculation circuit for calculating the SOC of a secondary battery, and a charging system using the same. And it is related with the SOC calculation method utilized for a SOC calculation circuit.

  In recent years, secondary batteries have been widely used as power supply systems in combination with solar batteries and power generation devices. The power generation device is driven by natural energy such as wind power or hydraulic power or artificial power such as an internal combustion engine. The power supply system combining such secondary batteries accumulates surplus power in the secondary battery and supplies power from the secondary battery when a load device is required, thereby improving energy efficiency.

  An example of such a system is a solar power generation system. When the amount of power generated by sunlight is larger than the power consumption of the load device, the solar power generation system charges the secondary battery with surplus power. On the other hand, when the power generation amount is smaller than the power consumption of the load device, power is output from the secondary battery to supplement the insufficient power, and the load device is driven.

  As described above, in the solar power generation system, surplus power that has not been used in the past can be stored in the secondary battery, so that energy efficiency can be improved compared to a power supply system that does not use the secondary battery.

  In such a photovoltaic power generation system, if the secondary battery is fully charged, surplus power cannot be charged and a loss occurs. Therefore, in order to efficiently charge the secondary battery with surplus power, charge control is performed so that the state of charge of the secondary battery (hereinafter referred to as SOC: State Of Charge) does not become 100%. In addition, charging control is performed so that the SOC does not become 0 (zero)% so that the load device can be driven when necessary. Specifically, in a secondary battery, charge control is normally performed so that the SOC changes in a range of 20% to 80%.

  A hybrid electric vehicle (HEV) using an engine and a motor also uses such a principle. When the output from the engine is larger than the motive power required for traveling, the HEV drives the generator with the surplus engine output and charges the secondary battery. Further, the HEV charges the secondary battery by using the motor as a generator during braking or deceleration of the vehicle.

  In addition, load leveling power sources and plug-in hybrid vehicles that make effective use of nighttime power have recently attracted attention. The load leveling power source is a system that stores power in a secondary battery at night when the power consumption is low and the power rate is low, and uses the stored power during the day when the power consumption peaks. The purpose is to make the power generation amount constant by smoothing the power consumption, and to contribute to the efficient operation of power facilities and the reduction of capital investment.

Plug-in hybrid vehicles use electric power at night, mainly for EV driving that supplies power from secondary batteries when driving in urban areas where fuel efficiency is poor, and for HEV driving that uses an engine and motor for long distance driving. The goal is to reduce total CO ₂ emissions.

  By the way, the secondary battery deteriorates as it is used, and its capacity decreases. It is important to accurately grasp the SOC of the secondary battery. For example, if the secondary battery is overcharged without accurately knowing the SOC of the secondary battery, long-term reliability such as the life of the secondary battery may be impaired. For this reason, it is necessary to accurately determine the SOC of the secondary battery being used and perform charge control.

  As a method for determining the SOC, a method for converting the terminal voltage of the secondary battery into the SOC by using the correlation between the terminal voltage of the secondary battery and the SOC is widely used.

  FIG. 7 is a graph showing the relationship between elapsed time and SOC when the secondary battery is discharged at a constant current value. The horizontal axis in FIG. 7 indicates time (sec), and the vertical axis indicates the secondary battery SOC (%). Moreover, the graph G1 shown by a broken line is a graph showing the actual SOC of the secondary battery, and the graph G2 shown by a solid line is a graph showing the SOC calculated by converting the terminal voltage of the secondary battery into the SOC. is there.

  In general, when a secondary battery is discharged with a constant current, the actual SOC decreases monotonously with the passage of time, as indicated by a broken line. However, as indicated by the solid line, the SOC converted from the terminal voltage may fluctuate greatly in a short time even though the actual SOC does not fluctuate greatly.

  For example, when the discharge current or charging current of the secondary battery fluctuates in a short time, the voltage drop caused by the internal resistance of the secondary battery fluctuates and the terminal voltage fluctuates. As a result, the SOC converted from the terminal voltage also arises from fluctuations accompanying fluctuations in the terminal voltage.

  As described above, since the SOC of the secondary battery is used to control the charging / discharging of the secondary battery, if the erroneous SOC is calculated or the SOC calculation accuracy is low, the charging / discharging of the secondary battery is performed. Discharge cannot be appropriately controlled, and there is a possibility that the deterioration of the secondary battery is accelerated and the life is shortened, or the long-term reliability of the secondary battery is impaired.

  In view of the importance of calculating the correct SOC, for example, a self-diagnosis circuit is provided that determines that a malfunction has occurred in the SOC calculation circuit when the SOC fluctuates abnormally and greatly exceeds a preset reference value. In some cases. In this case, if the calculated SOC value fluctuates by 3% even though the SOC calculation circuit functions normally, for example, the SOC fluctuates by only 1% per second, the SOC There is a possibility that it is erroneously recognized that a problem has occurred in the calculation circuit.

  In order to solve such a problem, for example, for the purpose of improving the detection accuracy of the SOC, a method of limiting the fluctuation of the SOC based on the value of the current flowing through the battery has been proposed (for example, see Patent Document 1). . According to this proposal, if the variation of the SOC is limited to 1%, even if the calculated SOC varies by 3%, the variation of the SOC is regarded as 1%.

  As a result, the calculated SOC value gradually fluctuates, so that the possibility of erroneous recognition that a malfunction has occurred in the SOC calculation device is reduced, and the accuracy of SOC estimation may be reduced due to temporary terminal voltage fluctuations. Is reduced, and adverse effects on subsequent charging control are reduced.

FIG. 8 shows the SOC obtained by conversion from the terminal voltage under the condition that the fluctuation of the terminal voltage is the same as that in FIG. 7, when the fluctuation is not limited and when the fluctuation range is limited to 1%. It is the graph compared. A case where the variation is not limited is indicated by a graph G2 (solid line), and a case where the variation range is limited to 1% is indicated by a graph G3 (broken line). As shown by the graph G3, it can be confirmed that by limiting the fluctuation of the SOC, the deviation from the actual SOC (graph G1) shown in FIG. 7 is smaller than the graph G2 that does not limit the fluctuation.
JP 2005-345254 A

  By the way, in the technique described in Patent Document 1, in order to improve the accuracy when calculating the SOC by converting from the terminal voltage of the secondary battery, the SOC variation limit is set based on the charge / discharge current. However, the factor that affects the terminal voltage of the secondary battery is not only the charge / discharge current value, but also the terminal voltage of the secondary battery varies depending on other factors. As described above, when the terminal voltage of the secondary battery fluctuates due to a factor other than the charge / discharge current value, it is impossible to set the SOC fluctuation range to an appropriate value, and the calculation accuracy of the SOC is reduced. there were.

  An object of the present invention is to provide an SOC calculation circuit, a charging system, and an SOC calculation circuit that can reduce the possibility that the calculation accuracy of the SOC will decrease even when the terminal voltage of the secondary battery fluctuates due to factors other than the charge / discharge current value. And providing an SOC calculation method.

  An SOC calculation circuit according to the present invention integrates a voltage detection unit that detects a terminal voltage of a secondary battery, a current detection unit that detects a current flowing through the secondary battery, and a current detected by the current detection unit. A current integrating unit that calculates an integrated current value, and an SOC estimating unit that repeats a process of obtaining the SOC estimated value by estimating the SOC of the secondary battery from the terminal voltage detected by the voltage detecting unit, Based on the SOC estimation value estimated by the SOC estimation unit, an SOC calculation unit that repeats an SOC calculation process for calculating the SOC of the secondary battery, and the SOC based on the integrated current value calculated by the current integration unit A limit value setting unit for setting a limit value for limiting a change amount of the SOC calculated by the calculation unit from the previous time, and the SOC calculation unit includes the previous S In the current SOC calculation process, the difference between the SOC calculated in the C calculation process and the SOC calculated in the current SOC calculation process is within the limit value set by the limit value setting unit. The SOC of the secondary battery is calculated.

  Further, the SOC calculation method according to the present invention includes a current integration step of calculating an integrated current value by integrating the current flowing through the secondary battery, and the SOC of the secondary battery from the terminal voltage of the secondary battery. An SOC estimation step that repeats a process of obtaining an estimated SOC value by estimating, an SOC calculation step that repeats an SOC calculation process that calculates an SOC of the secondary battery based on the estimated SOC estimate value, and the calculated A limit value setting step for setting a limit value for limiting the amount of change of the SOC calculated in the SOC calculation step from the previous time based on the accumulated current value. In the SOC calculation step, The difference between the SOC calculated in the SOC calculation process and the SOC calculated in the current SOC calculation process is the control value set in the limit value setting step. As it will be within a range of values, and calculates the SOC of new secondary battery in the current SOC calculation process.

  According to this configuration, the current flowing through the secondary battery is integrated as an integrated current value. Then, since the integrated current value increases as the deterioration of the secondary battery proceeds, the integrated current value indicates the degree of deterioration of the secondary battery. Further, the SOC of the secondary battery is estimated as the estimated SOC value from the terminal voltage of the secondary battery. Then, based on the calculated integrated current value, a limit value for limiting the amount of change of the newly calculated SOC from the previous time is set. Further, based on the estimated SOC value in the current SOC calculation process, the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is within the range of the limit value. The SOC of the secondary battery is newly calculated.

  Since the actual SOC gradually changes as the secondary battery is charged and discharged, if the difference between the previously calculated SOC and the SOC estimated as the current SOC estimated value is so large that it exceeds the limit value, the actual SOC The terminal voltage of the secondary battery changes due to a factor different from the change in the SOC, and the SOC is estimated from the terminal voltage. Therefore, there is a high possibility that the difference is large. Then, if this SOC estimated value is used as the SOC of the secondary battery as it is, there is a high possibility that the SOC error will increase. Therefore, by limiting the difference between the SOC calculated last time and the SOC calculated in the current SOC calculation processing within the range of the limit value, it is possible to reduce the possibility of an increase in SOC error.

  Here, as the secondary battery deteriorates, the internal resistance value increases. When the internal resistance value increases, a voltage drop caused by the internal resistance when current flows through the secondary battery appears to be added to the terminal voltage of the secondary battery, so that an error in the estimated SOC value estimated from this terminal voltage increases. Will be. Therefore, based on the integrated current value, that is, information indicating the degree of deterioration of the secondary battery, a limit value is set to limit the amount of change in the calculated value of the current SOC from the previous calculated value of the SOC. The amount of change in the SOC is limited so that the difference between the SOC calculated in the current SOC calculation process and the SOC calculated in the current SOC calculation process is within the range of the limit value. As a result of calculating the SOC of the secondary battery, the possibility that the error included in the estimated SOC value is reflected in the new SOC is reduced. As a result, the secondary battery is deteriorated, thereby causing factors other than the charge / discharge current value. Even if the terminal voltage of the secondary battery fluctuates due to the above, it is possible to reduce the possibility that the calculation accuracy of the SOC will decrease.

  Further, it is preferable that the limit value setting unit sets the limit value so that the limit value decreases as the integrated current value calculated by the current integration unit increases.

  According to this configuration, as the integrated current value increases, that is, the secondary battery deteriorates and the internal resistance increases, and the condition that the error between the SOC estimated value by the SOC estimating unit and the actual SOC becomes larger is satisfied. Since the limit value is set to a small value and the amount of change in the newly calculated SOC value from the previous SOC calculated value is limited to a small range, the SOC calculation error can be reduced.

  Further, the limit value setting unit includes a terminal voltage detected by the voltage detection unit when the SOC estimation unit previously estimated by the SOC estimation unit and a terminal voltage newly detected by the voltage detection unit this time. Preferably, the difference is calculated as a voltage change amount, and the limit value is set by further using the voltage change amount.

  As described above, when the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is limited to be within the range of the limit value, the actual SOC greatly varies. As a result, when the terminal voltage of the secondary battery fluctuates greatly, and the estimated SOC value estimated from the terminal voltage exceeds the limit value range, the change of the new SOC is excessively limited. The calculation error may increase. Therefore, according to this configuration, a voltage that is a difference between the terminal voltage detected by the voltage detection unit when the SOC estimation unit was previously estimated by the SOC estimation unit and the terminal voltage newly detected by the voltage detection unit this time. Since the limit value is further set by using the change amount, setting the limit value according to the voltage change amount reduces the possibility that the SOC calculation error will increase due to excessively limited SOC change. Easy to do.

  The SOC calculation circuit according to the present invention includes a voltage detection unit that detects a terminal voltage of a secondary battery, a current detection unit that detects a current flowing through the secondary battery, and a terminal voltage detected by the voltage detection unit. An SOC estimation unit that repeats the process of obtaining the SOC estimation value by estimating the SOC of the secondary battery from the SOC, and the SOC that calculates the SOC of the secondary battery based on the SOC estimation value estimated by the SOC estimation unit An SOC calculation unit that repeats the calculation process, a terminal voltage detected by the voltage detection unit when the SOC was previously estimated by the SOC estimation unit, and a terminal voltage newly detected by the voltage detection unit this time The difference is calculated as a voltage change amount, and based on the voltage change amount, a control for limiting the change amount from the previous time of the SOC calculated by the SOC calculation unit is calculated. A limit value setting unit for setting a value, and the SOC calculation unit determines whether the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is different by the limit value setting unit. In the current SOC calculation process, the SOC of the secondary battery is newly calculated so as to be within the set limit value range.

  The SOC calculation method according to the present invention includes an SOC estimation step that repeats a process of obtaining an SOC estimated value by estimating an SOC of the secondary battery from a terminal voltage of the secondary battery, and the estimated SOC estimation. An SOC calculation step of repeating an SOC calculation process for calculating an SOC of the secondary battery based on the value, a terminal voltage of the secondary battery when the previous SOC was estimated, and the secondary battery newly detected this time A limit value setting for setting a limit value for limiting a change amount of the SOC from the previous time calculated by the SOC calculation process based on the voltage change amount. In the SOC calculation step, the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is determined by the control. So that within the limit value set by the value setting step, calculating the SOC of new secondary battery in the current SOC calculation process.

  As described above, the internal resistance value of the secondary battery increases as the deterioration progresses, and a voltage drop caused by the internal resistance when current flows through the secondary battery is added to the terminal voltage of the secondary battery. For this reason, as the deterioration of the secondary battery proceeds, the terminal voltage of the secondary battery is likely to fluctuate according to the change of the charge / discharge current. Therefore, when the secondary battery deteriorates, the voltage change amount is likely to increase.

  Therefore, according to this configuration, a limit for limiting the amount of change in the calculated value of the current SOC from the previous calculated value of the SOC using information indicating the amount of voltage change, that is, the degree of deterioration of the secondary battery. A value is set, and the amount of change in the SOC is limited so that the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is within the range of the limit value, By newly calculating the SOC of the secondary battery based on the SOC estimated value, the possibility that an error included in the SOC estimated value is reflected in the new SOC is reduced. As a result, secondary battery deterioration that is a factor other than the charge / discharge current value, for example, secondary battery deterioration caused by temperature environment or mechanical stress that is a deterioration factor other than the accumulation of secondary battery charge / discharge, etc. Even if the terminal voltage of the secondary battery fluctuates due to the influence, it is possible to reduce the possibility that the calculation accuracy of the SOC will decrease.

  Moreover, it is preferable that the limit value setting unit sets the limit value so that the limit value decreases as the voltage change amount increases.

  According to this configuration, as the voltage change amount increases and the possibility that the secondary battery is deteriorated is increased, the limit value is reduced and the SOC change is more severely limited. Therefore, even when the terminal voltage of the secondary battery increases due to the influence of the deterioration of the secondary battery, it is possible to reduce the possibility that the SOC calculation accuracy is lowered.

  The temperature detection unit further detects a temperature of the secondary battery, and the limit value setting unit further sets the limit value using the temperature of the secondary battery detected by the temperature detection unit. It is preferable.

  The internal resistance value of the secondary battery changes according to the temperature. For this reason, when the internal resistance value increases according to the temperature change, a voltage drop caused by the internal resistance when current flows through the secondary battery appears to be added to the terminal voltage of the secondary battery, and is estimated from this terminal voltage. The error of the SOC estimated value will increase. Therefore, the limit value setting unit sets the limit value by further using the temperature of the secondary battery detected by the temperature detection unit, thereby causing a temperature change of the secondary battery to cause a factor other than the charge / discharge current value. Even when the terminal voltage of the secondary battery fluctuates, it is possible to reduce the possibility that the calculation accuracy of the SOC will decrease.

  Further, it is preferable that the limit value setting unit sets the limit value so that the limit value decreases as the temperature detected by the temperature detection unit decreases.

  The internal resistance value of the secondary battery generally increases as the temperature decreases. Therefore, according to this configuration, as the temperature of the secondary battery decreases, that is, the internal resistance of the secondary battery increases, and the condition that the error between the SOC estimated value by the SOC estimation unit and the actual SOC becomes larger is satisfied. Since the limit value is set to a small value and the amount of change in the newly calculated SOC value from the previous SOC calculated value is limited to a small range, the SOC calculation error can be reduced.

  Further, the SOC calculation unit is configured such that a difference between the SOC calculated in the previous SOC calculation process and the SOC estimated value newly estimated by the SOC estimation unit is a range of the limit value set by the limit value setting unit. If the difference is outside the range of the limit value set by the limit value setting unit, the newly estimated SOC estimate value is obtained as the SOC of the secondary battery. A value obtained by changing the SOC calculated in the calculation process by the limit value is preferably calculated as the SOC of the secondary battery.

  According to this configuration, it is possible to limit the difference between the SOC calculated in the previous SOC calculation process and the SOC newly calculated this time within the range of the limit value, thereby reducing the SOC calculation error. be able to.

  Further, the SOC calculation unit is configured such that a difference between the SOC calculated in the previous SOC calculation process and the SOC estimated value newly estimated by the SOC estimation unit is a range of the limit value set by the limit value setting unit. If the SOC estimated value newly estimated by the SOC estimating unit is larger than the SOC calculated in the previous SOC calculation process, the restriction is applied to the SOC calculated in the previous SOC calculation process. A value obtained by adding the values is calculated as the SOC of the secondary battery. When the SOC estimated value newly estimated by the SOC estimation unit is smaller than the SOC calculated in the previous SOC calculation process, the previous SOC is calculated. A value obtained by subtracting the limit value from the SOC calculated in the calculation process is preferably calculated as the SOC of the secondary battery. There.

  According to this configuration, the difference between the SOC calculated in the previous SOC calculation process and the SOC estimated value newly estimated by the SOC estimating unit is so large that it exceeds the limit value range set by the limit value setting unit. In this case, when the SOC is increasing, when the SOC is increasing, a value obtained by adding the limit value to the SOC calculated in the previous SOC calculating process is calculated as the SOC of the new secondary battery, and when the SOC is decreasing. The value obtained by subtracting the limit value from the SOC calculated in the previous SOC calculation process is calculated as the SOC of the new secondary battery. Therefore, when the difference between the previous SOC and the newly estimated SOC value is so large that it exceeds the range of the limit value, the newly calculated SOC of the previous calculated SOC regardless of the charge / discharge direction of the secondary battery. The amount of change from the calculated SOC can be limited to the limit value.

  The current integrating unit preferably calculates the integrated current value by integrating any one of a discharge current and a charging current of the secondary battery detected by the current detecting unit.

  The deterioration of the secondary battery is mainly caused by charge / discharge. Therefore, as the cumulative value of the charged / discharged current amount increases, the deterioration of the secondary battery progresses. Here, since the secondary battery discharges the charged electric charge, the integrated value of the charging current and the integrated value of the discharging current are substantially equal in the long term. Therefore, if any one of the charging current and the charging current is integrated, the integrated value indicates the degree of deterioration of the secondary battery. Therefore, the current integrating unit calculates an integrated current value as information indicating the degree of deterioration of the secondary battery by integrating any one of the discharge current and the charging current. As a result, the integrated current value becomes a smaller value than the integration of both the charging current and the discharging current, and it becomes easy to reduce the circuit scale used for integration.

  The charging system according to the present invention includes the above-described SOC calculation circuit, the secondary battery, and a charge control unit that controls charging of the secondary battery based on the SOC calculated by the SOC calculation circuit. Prepare.

  According to this configuration, in the charging system of the secondary battery, even when the terminal voltage of the secondary battery fluctuates due to a factor other than the charge / discharge current value, the SOC can be reduced while reducing the possibility that the calculation accuracy of the SOC decreases. And charging of the secondary battery can be controlled based on this SOC. Therefore, when the terminal voltage of the secondary battery fluctuates due to a factor other than the charge / discharge current value, the accuracy of charge control of the secondary battery is improved. It is possible to reduce the risk of lowering.

  The SOC calculating circuit and the SOC calculating method having such a configuration change the calculated value of the current SOC from the previous calculated value of the SOC based on the integrated current value, that is, information indicating the degree of deterioration of the secondary battery. A limit value for limiting the amount is set, and the SOC value is set so that the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is within the range of the limit value. As a result of newly calculating the SOC of the secondary battery based on the estimated SOC value while limiting the amount of change, the possibility that an error included in the estimated SOC value is reflected in the new SOC is reduced. As a result of the deterioration, even if the terminal voltage of the secondary battery varies due to factors other than the charge / discharge current value, the possibility that the SOC calculation accuracy may be reduced can be reduced.

  Further, the SOC calculation circuit and the SOC calculation method having such a configuration are the difference between the terminal voltage detected by the voltage detection unit when the SOC was estimated last time and the terminal voltage newly detected this time. Since the limit value is set by further using the voltage change amount, setting the limit value according to the voltage change amount may limit the SOC change excessively and may increase the SOC calculation error. It becomes easy to reduce.

  The charging system having such a configuration calculates the SOC while reducing the possibility that the calculation accuracy of the SOC will decrease even when the terminal voltage of the secondary battery fluctuates due to factors other than the charge / discharge current value. Since the charging of the secondary battery can be controlled based on this SOC, the accuracy of the charging control of the secondary battery may be reduced when the terminal voltage of the secondary battery fluctuates due to a factor other than the charge / discharge current value. Can be reduced.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. FIG. 1 is a block diagram illustrating an example of a configuration of a charging system 1 including a charging control circuit 4 corresponding to an example of an SOC calculation circuit according to an embodiment of the present invention. The charging system 1 shown in FIG. 1 is configured by combining a battery pack 2 and a charging device 3 (charging unit).

  The charging system 1 further includes a load device (not shown) to which power is supplied from the battery pack 2, an electronic device such as a portable personal computer, a digital camera, and a mobile phone, a vehicle such as an electric vehicle and a hybrid car, etc. It may be configured as a battery-mounted device system. In this case, FIG. 1 shows an example in which the battery pack 2 is directly charged from the charging device 3, but the configuration in which the battery pack 2 is mounted on the load device and charged from the charging device 3 via the load device. It may be.

  The charging device 3 may be a power supply circuit that generates a charging current for the battery pack 2 from a commercial power supply voltage, for example, a power generation device that generates electric power based on natural energy such as sunlight, wind power, or hydropower, or an internal combustion engine For example, a power generation device that generates power by using such power may be used.

  The battery pack 2 includes connection terminals 11, 12, 13, an assembled battery 14 (secondary battery), a charge control circuit 4, a communication unit 203, and switching elements Q1, Q2. The charge control circuit 4 includes an analog / digital (A / D) converter 201, a control unit 202, a voltage detection circuit 15 (voltage detection unit), a current detection resistor 16 (current detection unit), and a temperature sensor 17 (temperature detection). Part).

  Note that the charging system 1 is not necessarily limited to one configured to be separable into the battery pack 2 and the charging device 3, and one charging control circuit 4 may be configured in the entire charging system 1. Further, the charge control circuit 4 may be shared by the battery pack 2 and the charging device 3. The assembled battery 14 does not need to be a battery pack. For example, the charge control circuit 4 may be configured as an in-vehicle ECU (Electric Control Unit).

  The charging device 3 includes connection terminals 31, 32, 33, a control IC 34, and a charging current supply unit 35. The control IC 34 includes a communication unit 36 and a control unit 37. The charging current supply unit 35 is a power supply circuit that supplies a current corresponding to a control signal from the control unit 37 to the battery pack 2 via the connection terminals 31 and 32. The control unit 37 is a control circuit configured using, for example, a microcomputer.

  The battery pack 2 and the charging device 3 are connected to each other by connection terminals 11, 31; 12, 32 for power feeding and connection terminals 13, 33 for communication signals. The communication units 203 and 36 are communication interface circuits configured to be able to transmit / receive data to / from each other via the connection terminals 13 and 33.

  In the battery pack 2, the connection terminal 11 is connected to the positive electrode of the assembled battery 14 via the charging switching element Q2 and the discharging switching element Q1. As the switching elements Q1 and Q2, for example, p-channel FETs (Field Effect Transistors) are used. The switching element Q1 has a parasitic diode cathode in the direction of the assembled battery 14. The switching element Q2 has a parasitic diode cathode in the direction of the connection terminal 11.

  The connection terminal 12 is connected to the negative electrode of the assembled battery 14 via the current detection resistor 16, and the connection terminal 12 is connected from the connection terminal 11 via the switching elements Q 2 and Q 1, the assembled battery 14, and the current detection resistor 16. A current path leading to is configured. The current detection resistor 16 converts the charging current and discharging current of the assembled battery 14 into voltage values.

  The assembled battery 14 is configured by, for example, a plurality of battery blocks B1, B2,. In addition, each of the battery blocks B1, B2,..., BN includes, for example, a plurality of secondary batteries 141 connected in series. The assembled battery 14 may be, for example, a single battery, may be, for example, an assembled battery in which a plurality of secondary batteries are connected in parallel, or is an assembled battery connected in combination of series and parallel. May be. The secondary battery 141 is, for example, a lithium ion secondary battery.

  In this case, the secondary battery 141, the battery blocks B1, B2,..., BN, and the assembled battery 14 each correspond to an example of a secondary battery in the claims.

  The temperature sensor 17 is a temperature sensor that detects the temperature T of the assembled battery 14. The temperature of the assembled battery 14 is detected by the temperature sensor 17 and input to the analog-digital converter 201 in the charge control circuit 4. Further, the terminal voltages Vb1, Vb2,..., VbN of the battery blocks B1, B2,..., BN are respectively detected by the voltage detection circuit 15 and input to the analog-digital converter 201 in the charge control circuit 4. Is done.

  In the following description, the battery blocks B1, B2,..., BN, terminal voltages Vb1, Vb2,. When referring to individual configurations and voltages, they are denoted by reference numerals with suffixes.

  Furthermore, the current value of the charge / discharge current Ic detected by the current detection resistor 16 is also input to the analog-digital converter 201 in the charge control circuit 4. The analog-digital converter 201 converts each input value into a digital value and outputs the digital value to the control unit 202.

  The control unit 202 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. For example, a table storage unit 217 including an EEPROM (Electrically Erasable and Programmable Read Only Memory), a ROM, and the like, a timer circuit, and peripheral circuits thereof are configured. Then, the control unit 202 executes a control program stored in the ROM, so that the protection control unit 211, the charging processing unit 212, the current integration unit 213, the SOC estimation unit 214, the limit value setting unit 215, and the SOC calculation unit It functions as 216.

  The current integration unit 213 integrates the current value in the discharge direction detected by the current detection resistor 16 and calculates the integrated current value IDC. The current integration unit 213 may calculate the integrated current value IDC by, for example, integrating the product of the integration execution interval time and the discharge current value, and the current detection resistor 16 may be calculated every unit time (1 second). The integrated current value IDC may be calculated by integrating the discharge current value detected in step.

  The current accumulation unit 213 continuously accumulates the accumulated current value IDC, for example, when the battery pack 2 is assembled at the factory, a new assembled battery 14 is attached to the battery pack 2, and the control unit 202 is activated. Then, integration of the integrated current value IDC is executed.

  The deterioration of the secondary battery 141 is mainly caused by the execution of charging / discharging. Therefore, as the cumulative value of the charged / discharged current amount increases, the deterioration of the secondary battery 141 progresses. Here, since the secondary battery 141 discharges the charged electric charge, the integrated value of the charging current and the integrated value of the discharging current are substantially equal in the long term. Therefore, if any one of the charging current and the charging current is integrated, the integrated value indicates the degree of deterioration of the secondary battery.

  Therefore, the current integration unit 213 calculates the integrated current value IDC as information indicating the degree of deterioration of the secondary battery by integrating only the discharge current detected by the current detection resistor 16. The current integrating unit 213 may calculate the integrated current value IDC by integrating only the charging current.

  The current integration unit 213 may calculate the integrated current value IDC by integrating the absolute values of both the charging current and the discharging current. However, the integrated current value IDC is smaller when one of the charging current and the charging current is integrated than when the absolute values of both the charging current and the discharging current are integrated. It is preferable in that it is easy to reduce the circuit scale of a register, an adder, and a memory used for integration.

  The SOC estimation unit 214 converts the terminal voltages Vb1, Vb2,..., VbN detected by the voltage detection circuit 15 at, for example, a preset time Δt into, for example, an SOC converted in advance stored in the table storage unit 217. The SOC of the battery blocks B1, B2,..., BN is estimated as the converted value SOCK (SOC estimated value) by converting into SOC using the table.

  The SOC estimation unit 214 may estimate the converted value SOCK for each secondary battery 141 based on the terminal voltage of each secondary battery 141, and the converted value of the entire assembled battery 14 based on the terminal voltage of the entire assembled battery 14 The SOCK may be estimated.

  In the table storage unit 217, for example, an SOC conversion table indicating a correspondence relationship between the terminal voltage Vb of the battery block B and the SOC of each battery block is stored in advance. Further, the table storage unit 217 includes three parameters including an integrated current value IDC, a voltage fluctuation amount ΔV / Δt indicating a change amount per unit time of the terminal voltage Vb, and a temperature T of the assembled battery 14, A variation limit value table, which is a three-dimensional data table showing a correspondence relationship with a variation limit value SOCL (limit value) indicating a range in which variation in SOC (%) is allowed, is stored in advance.

  2, 3, and 4 are explanatory diagrams illustrating an example of a variation limit value table stored in the table storage unit 217. The variation limit value tables shown in FIGS. 2, 3, and 4 show an example of the variation limit value table when a secondary battery with a rated capacity of 2 (Ah) is assumed, for example. 2 corresponds to the case where the temperature T is 0 ° C., FIG. 3 corresponds to the case where the temperature T is 20 ° C., and FIG. 4 corresponds to the case where the temperature T is 40 ° C.

  2, 3, and 4, the horizontal axis indicates the integrated current value IDC, and the vertical axis indicates the voltage fluctuation amount ΔV / Δt. The integrated current value IDC and the voltage fluctuation amount Δ In the column where V / Δt intersects, variation limit values SOCL corresponding to the three parameters of temperature T, integrated current value IDC, and voltage change amount ΔV / Δt in each figure are described.

  In the fluctuation limit value tables shown in FIGS. 2, 3, and 4, the fluctuation limit value SOCL is set such that the fluctuation limit value SOCL decreases as the integrated current value IDC increases. In this variation limit value table, the variation limit value SOCL is set so that the variation limit value SOCL decreases as the voltage change amount ΔV / Δt increases. Further, in this fluctuation limit value table, the fluctuation limit value SOCL is set so that the fluctuation limit value SOCL increases as the temperature T increases.

  In the variation limit value tables shown in FIGS. 2, 3, and 4, since the accuracy of the variation limit value SOCL is rough, the variation limitation value is limited with respect to changes in the temperature T, the integrated current value IDC, or the voltage change amount ΔV / Δt. There is a region where the value SOCL does not change. As a tendency of the entire fluctuation limit value table, the fluctuation limit value SOCL is smaller as the integrated current value IDC is larger, and is smaller as the voltage change amount ΔV / Δt is larger. The variation limit value SOCL is set so as to decrease as T decreases.

  Limit value setting unit 215 has terminal voltage Vb detected by voltage detection circuit 15 when SOC was estimated by SOC estimation unit 214 last time (the initial value of terminal voltage Vb may be 0 V immediately after activation). The voltage difference ΔV / Δt per unit time is calculated by dividing the voltage difference ΔV, which is the difference from the terminal voltage Vb newly detected by the voltage detection circuit 15 this time, by the time Δt. .

  Then, the limit value setting unit 215 is associated with the temperature T, the integrated current value IDC, and the voltage variation amount ΔV / Δt by the variation limit value table stored in the table storage unit 217. Get the SOCL.

  The SOC calculation unit 216 is based on the estimated SOC value estimated by the SOC estimation unit 214 each time the SOC estimation unit 214 estimates the SOC of the battery blocks B1, B2,. Thus, the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is within the range of the fluctuation limit value SOCL set by the limit value setting unit 215. , SOC of the battery blocks B1, B2,..., BN are newly calculated.

  The protection control unit 211 detects an abnormality outside the battery pack 2 such as a short circuit between the connection terminals 11 and 12, an abnormal current, an abnormal temperature rise of the assembled battery 14, or the like from each input value from the analog-digital converter 201. Detect anomalies. Specifically, for example, when the current value detected by the current detection resistor 16 exceeds a preset abnormal current determination threshold, it is determined that an abnormality based on a short circuit between the connection terminals 11 and 12 has occurred, for example, the temperature When the temperature of the assembled battery 14 detected by the sensor 17 exceeds a preset abnormal temperature determination threshold, it is determined that an abnormality has occurred in the assembled battery 14. When such an abnormality is detected, the switching elements Q1 and Q2 are turned off, and a protective operation for protecting the assembled battery 14 from an abnormality such as overcurrent or overheating is performed.

  Further, the protection control unit 211 detects overcharge when the maximum value of each SOC of the battery blocks B1, B2,..., BN exceeds 100% based on the SOC calculated by the SOC calculation unit 216, for example. The battery pack 14 is protected from overcharging by judging and turning off the switching element Q2 to cut off the charging current. Further, the protection control unit 211 detects overdischarge when the minimum value of each SOC of the battery blocks B1, B2,..., BN falls below 3% based on the SOC calculated by the SOC calculation unit 216, for example. The battery pack 14 is protected from overdischarge by judging and turning off the switching element Q1 to cut off the discharge current.

  The protection control unit 211 determines overdischarge or overcharge based on the SOC of the battery block B calculated by the SOC calculation unit 216 in this way, so that a temporary change occurs according to the load current or the charge current. The determination accuracy of overdischarge or overcharge can be improved as compared with the case where overdischarge or overcharge is determined based on the terminal voltage of the assembled battery 14 (secondary battery 141) that is likely to occur.

  The charging processing unit 212 controls charging of the assembled battery 14 based on the SOC calculated by the SOC calculating unit 216. Specifically, the charging processing unit 212 calculates the SOC of the entire assembled battery 14 by, for example, averaging the SOC of each battery block B calculated by the SOC calculation unit 216. Then, for example, when the SOC of the entire assembled battery 14 exceeds 80%, the charging processing unit 212 requests the charging device 3 to stop charging via the communication unit 203, and the SOC of the entire assembled battery 14 is 20%. When the value is lower than, the SOC of the assembled battery 14 is adjusted to 20% to 80% by requesting the charging device 3 to start charging via the communication unit 203.

  In this case, the protection control unit 211 and the charge processing unit 212 correspond to an example of the charge control unit in the claims.

  In the charging device 3, a request from the control unit 202 is received by the communication unit 36 in the control IC 34, and the control unit 37 controls the charging current supply unit 35, so that the request is received from the control unit 202. The charging current is supplied to the battery 14 or the supply of the charging current to the assembled battery 14 is stopped.

  Next, the operation of the charging system 1 configured as described above will be described. FIG. 5 is a flowchart showing an example of the SOC calculation operation in charging system 1 shown in FIG. The calculation of the SOC is executed every time Δt. The following processing is executed for each of the battery blocks B1, B2,.

  First, the terminal voltage Vb is detected by the voltage detection circuit 15, the charge / discharge current Ic is detected by the current detection resistor 16, and the temperature T is detected by the temperature sensor 17 (step S1).

  Next, the integrated current value IDC is calculated by the current integrating unit 213 (step S2). Specifically, only the current value in the discharge direction of the charging / discharging current Ic is multiplied by the time Δt that is the calculation interval of the integrated current value IDC by the current integrating unit 213, and the multiplied value is multiplied when the battery pack 2 is manufactured. Alternatively, the accumulated current value IDC is calculated cumulatively from the time of shipment. The larger the integrated current value IDC is, the more the battery 14 is deteriorated.

  Note that steps S1 and S2 are not limited to the example executed every time Δt, and the integrated current value IDC may be constantly updated, for example, by executing it every unit time. As the calculation interval of the integrated current value IDC is shorter, the accuracy of the integrated current value IDC is improved.

  Next, the terminal voltage Vb1, Vb2,..., VbN detected by the voltage detection circuit 15 when the SOC was previously estimated by the limit value setting unit 215, that is, before the time Δt, and the current voltage detection circuit. The voltage difference ΔV / Δ per unit time is obtained by dividing each voltage difference ΔV, which is a difference from the terminal voltages Vb1, Vb2,. t is calculated for each battery block (step S3).

  Then, the limit value setting unit 215 associates the temperature limit, the integrated current value IDC, and the voltage variation amount ΔV / Δt with the variation limit value table stored in the table storage unit 217. The SOCL is acquired (step S4).

  FIG. 6 shows a specific example of the fluctuation limit value SOCL obtained from the voltage fluctuation amount ΔV / Δt, the integrated current value IDC, and the temperature T based on the fluctuation limit value tables shown in FIGS. It is a list shown. FIG. 6 shows an example assuming a case where the rated capacity of the secondary battery is 2 (Ah), similarly to FIGS. 2, 3, and 4.

  In Example 1 shown in FIG. 6, the temperature T is a standard 20 ° C., and a variation limit value table corresponding to 20 ° C. shown in FIG. 3 is used. When the temperature T is 20 ° C., the increase in the internal resistance of the assembled battery 14 due to the temperature is small. Further, in Example 1, since the integrated current value IDC is 50 Ah and a relatively small value, it is considered that the assembled battery 14 has not deteriorated so much. The voltage fluctuation amount ΔV / Δt is 0.20 V / sec. From the voltage fluctuation amount ΔV / Δt, it is considered that the degree of deterioration of the assembled battery 14 is relatively small, for example.

  Then, Example 1 is considered to be a condition in which an error of the converted value SOCK with respect to the actual SOC hardly occurs. In such a case, it is desirable to set the fluctuation limit value SOCL to a relatively small standard value. In Example 1, from FIG. 3, the fluctuation limit value SOCL is set to 1% as a standard value.

  In Example 2 shown in FIG. 6, the voltage fluctuation amount ΔV / Δt and the temperature T are the same as in Example 1, but the integrated current value IDC is large, and the assembled battery 14 is more deteriorated than in Example 1. . If it does so, internal resistance of the assembled battery 14 will increase with deterioration. Therefore, even when the actual charge / discharge current is small and therefore the actual SOC fluctuation is small, the terminal voltage Vb greatly appears due to the voltage drop caused by the internal resistance. Therefore, there is a possibility that the fluctuation of the SOC conversion value SOCK obtained by conversion from the terminal voltage Vb is estimated to be larger than the actual fluctuation of the SOC.

  In such a case, it is desirable to set the fluctuation limit value SOCL to a smaller value than the standard case as in Example 1. As a result, the SOC calculation unit 216 reduces the possibility that the SOC may be changed and calculated more greatly than actual due to the fluctuation of the terminal voltage Vb that is different from the actual fluctuation of the SOC. In Example 2, from FIG. 3, the fluctuation limit value SOCL is set to 0.1%, which is smaller than in Example 1.

  In Example 3 shown in FIG. 6, the voltage fluctuation amount ΔV / Δt and the integrated current value IDC are the same as in Example 1, but the temperature T is low and the internal resistance of the assembled battery 14 is increased. Then, even if the actual charge / discharge current is small and therefore the actual SOC variation is small, the terminal voltage Vb varies greatly due to the voltage drop caused by the internal resistance. Therefore, there is a possibility that the fluctuation of the SOC conversion value SOCK obtained by conversion from the terminal voltage Vb is estimated to be larger than the actual fluctuation of the SOC.

  In such a case, it is desirable to set the fluctuation limit value SOCL to a smaller value than the standard case as in Example 1. As a result, the SOC calculation unit 216 reduces the possibility that the SOC may be changed and calculated more greatly than actual due to the fluctuation of the terminal voltage Vb that is different from the actual fluctuation of the SOC. In Example 3, from FIG. 2, the variation limit value SOCL is set to 0.5%, which is smaller than Example 1.

  In Example 4 shown in FIG. 6, the integrated current value IDC and the temperature T are the same as in Example 1, but the voltage fluctuation amount ΔV / Δt is smaller than in Example 1. In Example 4, as in Example 1, the temperature T is 20 ° C., so the increase in internal resistance of the assembled battery 14 due to temperature is small. Further, since the integrated current value IDC is 50 Ah and a relatively small value, it is considered that the deterioration of the assembled battery 14 has not progressed so much. Furthermore, since the voltage fluctuation amount ΔV / Δt is smaller than Example 1, it is considered that the deterioration of the assembled battery 14 is less than that of Example 1.

  Therefore, the voltage drop caused by the internal resistance of the assembled battery 14 is small, and it is considered that there is little error between the SOC converted value SOCK obtained by conversion from the terminal voltage Vb and the actual SOC. Therefore, in Example 4, the variation limit value SOCL is set to 3.0%, which is larger than that in Example 1, so that the change in the converted value SOCK is larger than that in Example 1 and reflected in the calculated SOC.

  Thus, in the fluctuation limit value tables shown in FIGS. 2, 3, and 4, it is considered that the error of the converted value SOCK is small from the calculated current value IDC, the temperature T, and the voltage fluctuation amount ΔV / Δt. A variation limit value SOCL is set according to the degree.

  Thus, in step S4, it is considered that the error between the converted value SOCK and the actual SOC increases as the integrated current value IDC increases, the temperature T decreases, the voltage fluctuation amount ΔV / Δt increases. The variation limit value SOCL is set to a smaller value as the conditions are satisfied.

  In addition, although the example which sets the fluctuation | variation limitation value SOCL using the three parameters of temperature T, integrated current value IDC, and voltage variation | change_quantity (DELTA) V / (DELTA) t was shown, either one of three parameters or The fluctuation limit value SOCL may be set using any two of them.

  Next, the SOC estimation unit 214 converts the terminal voltage Vb detected by the voltage detection circuit 15 into a conversion value SOCK using, for example, an SOC conversion table stored in the table storage unit 217 (step S5).

  Next, the SOC calculation unit 216 calculates a difference (SOCK−SOCP) between the previous value SOCP, which is the SOC calculated before time Δt (previous), and the converted value SOCK as the difference value SOCV (step S6). ). Note that immediately after the activation, the initial value of the previous value SOCP may be set to 0%, for example.

  Next, the SOC calculation unit 216 compares the absolute value of the difference value SOCV with the fluctuation limit value SOCL (step S7). If the absolute value of difference value SOCV is equal to or smaller than fluctuation limit value SOCL (NO in step S7), the amount of change in converted value SOCK from the previous time is within the range of fluctuation limit value SOCL. The converted value SOCK is acquired as a new SOC of the battery block B (step S8).

  On the other hand, if the absolute value of difference value SOCV exceeds fluctuation limit value SOCL (YES in step S7), positive / negative of difference value SOCV is confirmed by SOC calculation unit 216 (step S9). If the difference value SOCV is a positive value (YES in step S9), since the SOC is in an increasing direction, the SOC calculation unit 216 adds the variation limit value SOCL to the previous value SOCP, and the battery block B1, The SOC of B2,..., BN is calculated (step S10).

  On the other hand, if the difference value SOCV is a negative value (NO in step S9), the SOC is in a decreasing direction. Therefore, the SOC calculation unit 216 subtracts the fluctuation limit value SOCL from the previous value SOCP, and the battery block B1, The SOC of B2,..., BN is calculated (step S11).

  Then, when time Δt has elapsed (YES in step S12), SOC calculation unit 216 proceeds to step S1 to calculate a new SOC again, and the processes in steps S1 to S12 are repeated.

  As described above, according to the processing of steps S1 to S12, the integrated current value IDC increases and the assembled battery 14 deteriorates, the temperature T decreases and the internal resistance of the assembled battery 14 increases, that is, the converted value SOCK. The variation limit value SOCL is set to a smaller value as the condition that an error from the actual SOC is considered to be larger, and the amount of change from the previous value SOCP in the newly calculated SOC value is limited to a smaller range. Therefore, the calculation error of SOC can be reduced.

  Further, when the voltage fluctuation amount ΔV / Δt is large and there is a possibility that the SOC error may increase if the change in the SOC is excessively limited, the fluctuation limit value SOCL is increased, and the converted value Since SOCK is easily reflected in the calculated SOC as it is, an SOC error caused by excessive limitation is reduced.

  Thereby, even if the secondary battery is in a fresh state, a deteriorated state, or a case where it is affected by temperature, it is possible to reduce the possibility that the SOC calculation accuracy is lowered. In addition, even when the actual SOC changes greatly and the voltage fluctuation amount ΔV / Δt increases, the possibility that the SOC calculation accuracy may be reduced can be reduced.

  By the way, in the technique described in Patent Document 1 as the background art, in order to improve the calculation accuracy of the SOC, the SOC fluctuation limit is set based on the charge / discharge current. The secondary battery deteriorates due to repeated charge / discharge and the passage of time. The internal resistance value of the deteriorated secondary battery increases. Since the change in the terminal voltage of the secondary battery is the product of the internal resistance value and the current, the increase in the internal resistance value increases the voltage fluctuation even at a small current value. However, if the current value is small, the actual SOC variation is also small.

  Therefore, as in the technique described in Patent Document 1, when the limit value of the SOC fluctuation range is set according to the current value flowing through the secondary battery without considering deterioration, the secondary battery deteriorates. When the fluctuation of the terminal voltage with respect to the current flowing through the secondary battery increases, there is a disadvantage that the SOC fluctuation range cannot be set to an appropriate value and the SOC calculation accuracy is lowered.

  However, according to the charge control circuit 4 shown in FIG. 1, the secondary battery is deteriorated by setting the fluctuation limit value SOCL using the integrated current value IDC indicating the degree of deterioration of the secondary battery. In addition, it is possible to reduce the possibility that the calculation accuracy of the SOC is lowered.

  The present invention relates to an electronic device such as a portable personal computer, a digital camera, and a mobile phone, a vehicle such as an electric vehicle and a hybrid car, and a battery-mounted device such as a power supply system in which a solar battery or a power generator and a secondary battery are combined The present invention can be suitably used as an SOC calculation method for calculating the SOC of a secondary battery, an SOC calculation circuit, and a charging system using the same.

It is a block diagram which shows an example of a structure of the charging system provided with the charge control circuit corresponded to an example of the SOC calculation circuit which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the fluctuation | variation limitation value table memorize | stored in the table memory | storage part shown in FIG. It is explanatory drawing which shows an example of the fluctuation | variation limitation value table memorize | stored in the table memory | storage part shown in FIG. It is explanatory drawing which shows an example of the fluctuation | variation limitation value table memorize | stored in the table memory | storage part shown in FIG. 3 is a flowchart showing an example of an SOC calculation operation in the charging system shown in FIG. 1. FIG. 3 is a list showing specific examples of the fluctuation limit value SOCL obtained from the voltage fluctuation amount ΔV / Δt, the integrated current value IDC, and the temperature T based on the fluctuation limit value tables shown in FIGS. is there. It is a graph which shows the relationship between elapsed time and SOC when a secondary battery is discharged with a fixed electric current value. It is the graph which compared the case where the fluctuation | variation restriction | limiting was limited and the fluctuation | variation range was limited within 1% about the SOC obtained by converting from a terminal voltage on the conditions where the fluctuation | variation of a terminal voltage is the same.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging system 2 Battery pack 3 Charging device 4 Charging control circuit 14 Battery assembly 15 Voltage detection circuit 16 Current detection resistor 17 Temperature sensor 141 Secondary battery 201 Analog to digital converter 202 Control unit 211 Protection control unit 212 Charging processing unit 213 Current integration Unit 214 SOC estimation unit 215 limit value setting unit 216 SOC calculation unit 217 table storage unit B, B1, B2,..., BN battery block DSOC fluctuation value IDC integrated current value Q1, Q2 switching element SOCK converted value SOCL fluctuation limit value SOCP Previous value SOCV Difference value Vb, Vb1, Vb2, ..., VbN Terminal voltage

Claims (13)

A voltage detector for detecting the terminal voltage of the secondary battery;
A current detector for detecting a current flowing in the secondary battery;
A current integrating unit that calculates an integrated current value by integrating the current detected by the current detecting unit;
An SOC estimation unit that repeats the process of obtaining an SOC estimation value by estimating the SOC of the secondary battery from the terminal voltage detected by the voltage detection unit;
An SOC calculating unit that repeats an SOC calculating process for calculating the SOC of the secondary battery based on the SOC estimated value estimated by the SOC estimating unit;
A limit value setting unit for setting a limit value for limiting the amount of change from the previous time of the SOC calculated by the SOC calculation unit based on the integrated current value calculated by the current integration unit;
The SOC calculation unit
The current SOC calculation process so that the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is within the range of the limit value set by the limit value setting unit. A SOC calculation circuit characterized in that the SOC of the secondary battery is newly calculated. The limit value setting unit includes:
The SOC calculation circuit according to claim 1, wherein the limit value is set such that the limit value decreases as the integrated current value calculated by the current integration unit increases. The limit value setting unit includes:
The difference between the terminal voltage detected by the voltage detection unit when the SOC was estimated last time by the SOC estimation unit and the terminal voltage newly detected by the voltage detection unit this time is calculated as a voltage change amount, The SOC calculation circuit according to claim 1, wherein the limit value is set by further using the voltage change amount. A voltage detector for detecting the terminal voltage of the secondary battery;
A current detector for detecting a current flowing in the secondary battery;
An SOC estimation unit that repeats the process of obtaining an SOC estimation value by estimating the SOC of the secondary battery from the terminal voltage detected by the voltage detection unit;
An SOC calculating unit that repeats an SOC calculating process for calculating the SOC of the secondary battery based on the SOC estimated value estimated by the SOC estimating unit;
The difference between the terminal voltage detected by the voltage detection unit when the SOC was estimated last time by the SOC estimation unit and the terminal voltage newly detected by the voltage detection unit this time is calculated as a voltage change amount, A limit value setting unit that sets a limit value for limiting the amount of change from the previous SOC calculated by the SOC calculation unit based on the voltage change amount;
The SOC calculation unit
The current SOC calculation process so that the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is within the range of the limit value set by the limit value setting unit. A SOC calculation circuit characterized in that the SOC of the secondary battery is newly calculated. The limit value setting unit includes:
5. The SOC calculation circuit according to claim 3, wherein the limit value is set such that the limit value decreases as the voltage change amount increases. A temperature detection unit for detecting the temperature of the secondary battery;
The limit value setting unit includes:
The SOC calculation circuit according to claim 1, wherein the limit value is set by further using the temperature of the secondary battery detected by the temperature detection unit. The limit value setting unit includes:
The SOC calculation circuit according to claim 6, wherein the limit value is set so that the limit value decreases as the temperature detected by the temperature detection unit decreases. The SOC calculation unit
When the difference between the SOC calculated in the previous SOC calculation process and the SOC estimated value newly estimated by the SOC estimating unit is within the limit value set by the limit value setting unit, Obtain the estimated SOC estimated value as the SOC of the secondary battery,
When the difference is outside the range of the limit value set by the limit value setting unit, a value obtained by changing the SOC calculated in the previous SOC calculation process by the limit value is used as the SOC of the secondary battery. The SOC calculation circuit according to claim 1, wherein the SOC calculation circuit is calculated. The SOC calculation unit
When the difference between the SOC calculated in the previous SOC calculation process and the SOC estimated value newly estimated by the SOC estimating unit is outside the limit value set by the limit value setting unit,
When the SOC estimation value newly estimated by the SOC estimation unit is larger than the SOC calculated in the previous SOC calculation process, a value obtained by adding the limit value to the SOC calculated in the previous SOC calculation process is Calculated as the SOC of the secondary battery,
When the SOC estimation value newly estimated by the SOC estimation unit is smaller than the SOC calculated in the previous SOC calculation process, a value obtained by subtracting the limit value from the SOC calculated in the previous SOC calculation process is The SOC calculation circuit according to claim 8, wherein the SOC calculation circuit calculates the SOC of the secondary battery. The current integrating unit is
The integrated current value is calculated by integrating any one of a discharge current and a charging current of a secondary battery detected by the current detection unit. The SOC calculation circuit according to item 1. The SOC calculation circuit according to any one of claims 1 to 10,
The secondary battery;
A charging system comprising: a charging control unit that controls charging of the secondary battery based on the SOC calculated by the SOC calculating circuit. A current integrating step of calculating an integrated current value by integrating the current flowing through the secondary battery;
An SOC estimation step that repeats the process of obtaining the SOC estimated value by estimating the SOC of the secondary battery from the terminal voltage of the secondary battery;
An SOC calculation step of repeating an SOC calculation process for calculating an SOC of the secondary battery based on the estimated SOC estimated value;
A limit value setting step for setting a limit value for limiting the amount of change from the previous SOC calculated in the SOC calculation step based on the calculated integrated current value;
In the SOC calculation step,
The current SOC calculation process so that the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is within the range of the limit value set in the limit value setting step. A SOC calculation method characterized in that the SOC of the secondary battery is newly calculated. An SOC estimation step that repeats the process of obtaining the SOC estimated value by estimating the SOC of the secondary battery from the terminal voltage of the secondary battery;
An SOC calculation step of repeating an SOC calculation process for calculating an SOC of the secondary battery based on the estimated SOC estimated value;
The difference between the terminal voltage of the secondary battery when the SOC was estimated last time and the terminal voltage of the secondary battery newly detected this time is calculated as a voltage change amount, and based on the voltage change amount, A limit value setting step for setting a limit value for limiting the amount of change from the previous SOC calculated by the SOC calculation process,
In the SOC calculation step,
The current SOC calculation process so that the difference between the SOC calculated in the previous SOC calculation process and the SOC calculated in the current SOC calculation process is within the range of the limit value set in the limit value setting step. A SOC calculation method characterized in that the SOC of the secondary battery is newly calculated.

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