JP2015059814A - Soc estimation device and soc estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an SOC (State Of Charge) estimation device capable of accurately estimating SOC of a secondary battery.SOLUTION: An SOC estimation device 103 includes: a current integrated SOC calculation unit 94B that acquires integrated SOC by dividing the integrated value of a current within a cumulative period by the full battery capacity of a secondary battery 91, and calculates current integrated SOC by adding the integrated SOC to the SOC initial value of the secondary battery 91 before a start of the cumulative period; and a battery capacity estimation unit 95 that estimates the full battery capacity of the secondary battery 91 according to the deterioration degree of the secondary battery 91. The current integrated SOC calculation unit 94B updates the full battery capacity to the estimation full battery capacity of the secondary battery 91 estimated by the battery capacity estimation unit 95.

Description

  The present invention relates to an SOC estimation device and an SOC estimation method for estimating a state of charge (SOC) of a secondary battery.

  As a conventional battery state management device, Patent Document 1 discloses a calculation method for calculating a state of charge (SOC) of a battery from a battery current integration formula. In this calculation method, the integrated SOC is calculated by dividing the integrated amount of the battery current by the battery capacity, and the SOC based on the integrated current is calculated by adding the previous state of charge to the integrated SOC.

JP 2012-198175 A

  In the calculation method disclosed in Patent Document 1, a fixed battery capacity is used to calculate the SOC. However, the battery capacity decreases when the battery is used repeatedly and deteriorates. Therefore, in the method of calculating the SOC using a fixed battery capacity, the SOC of the battery cannot be accurately calculated when the battery has deteriorated. Therefore, when performing charge / discharge control of the battery based on the calculated SOC, the battery may be overcharged or overdischarged, which accelerates the deterioration of the battery.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an SOC estimation device and an SOC estimation method capable of accurately estimating the SOC of a secondary battery.

  The present invention relates to an SOC estimation device for estimating the SOC of a secondary battery, comprising: a current detector that detects the current of the secondary battery; and an integrated amount of current detected by the current detector within an accumulation period. A first SOC calculation unit that obtains an integrated SOC by dividing by a full battery capacity of the secondary battery, adds the integrated SOC to an initial SOC value of the secondary battery before the start of the accumulation period, and estimates a current integrated SOC; A battery capacity estimation unit that estimates a full battery capacity of the secondary battery according to a degree of deterioration of the secondary battery, and the battery capacity estimation unit estimates the full battery capacity in the first SOC calculation unit. The estimated full battery capacity of the secondary battery is updated.

  Further, the present invention is an SOC estimation method, estimating a full battery capacity of the secondary battery according to a degree of deterioration of the secondary battery, obtaining an initial SOC value of the secondary battery, An integrated value of the current flowing through the secondary battery is calculated, and the integrated value is divided by the estimated full battery capacity of the secondary battery to calculate an integrated SOC, and the integrated SOC is calculated before the cumulative period starts. The current integrated SOC is estimated by adding to the initial SOC value of the battery.

  According to the present invention, since the accumulated current SOC is calculated using the full battery capacity estimated according to the degree of deterioration of the secondary battery, the SOC of the secondary battery can be accurately estimated.

It is a schematic block diagram of the fluid pressure control system in the control system of the hybrid construction machine which concerns on embodiment of this invention. It is a schematic block diagram of the assist regeneration system connected to a fluid pressure control system. It is a block diagram which shows the SOC estimation apparatus which concerns on 1st Embodiment of this invention. It is a flowchart which shows the procedure of the arithmetic processing performed in the SOC calculating part of the SOC estimation apparatus which concerns on 1st Embodiment of this invention. It is a flowchart which shows the procedure of the calculation process of the open circuit voltage SOC. It is a flowchart which shows the procedure of the calculation process of electric current integration SOC. It is a flowchart which shows the procedure of the arithmetic processing performed in the battery capacity estimation part of the SOC estimation apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows an open circuit voltage SOC map. It is a flowchart which shows the procedure of the estimation method of a full battery capacity. It is a flowchart which shows the procedure of the estimation method of a full battery capacity. It is a flowchart which shows the procedure of the arithmetic processing performed in the battery capacity estimation part of the SOC estimation apparatus which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the procedure of the estimation method of a full battery capacity.

  Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
Hereinafter, a control system 100 for a hybrid construction machine according to a first embodiment of the present invention will be described with reference to the drawings.

  First, a fluid pressure control system 101 in the control system 100 for a hybrid construction machine according to the first embodiment of the present invention will be described with reference to FIG. The fluid pressure control system 101 is a device that controls the operation of a hydraulic construction machine such as a hydraulic excavator. For example, the fluid pressure control system 101 is a device that controls the operation of each actuator that drives the excavation attachment of a hydraulic excavator. Below, the case where the fluid pressure control system 101 controls the expansion / contraction operation | movement of the boom cylinder 10 which drives the boom 1 (load) of a hydraulic shovel is demonstrated.

  The fluid pressure control system 101 includes a boom cylinder 10 as an actuator and a main pump 21 as a fluid pressure pump that supplies hydraulic oil (working fluid) to the boom cylinder 10. The fluid pressure control system 101 further includes a pilot pump 22, a main control valve 30, a main passage 23, a first passage 41, a second passage 42, and a controller 50.

  The interior of the boom cylinder 10 is partitioned into a rod-side pressure chamber 11 and a bottom-side pressure chamber 12 by a piston rod 13 that slidably moves within the boom cylinder 10. The boom 1 is connected to the tip of the piston rod 13 located outside the boom cylinder 10.

  The main pump 21 and the pilot pump 22 are hydraulic supply sources that discharge hydraulic oil, and are variable displacement pumps that can adjust the inclination angle of the swash plate. The main pump 21 and the pilot pump 22 are driven by the engine 8 as a prime mover mounted on the hybrid construction machine. The engine 8 is provided with a rotational speed sensor 9 as a rotational speed detector that detects the rotational speed of the engine 8.

  The inclination angle of the swash plate of the main pump 21 is controlled by the inclination angle controller 20. The tilt angle controller 20 is controlled by the controller 50. By controlling the inclination angle of the swash plate of the main pump 21, the capacity of the main pump 21 changes, and the maximum value of the flow rate of hydraulic oil that can be discharged by the main pump 21 changes.

  The hydraulic oil discharged from the main pump 21 is supplied to the main control valve 30 through the main passage 23. Thus, the main pump 21 and the main control valve 30 are connected by the main passage 23. In addition to the hydraulic oil discharged from the main pump 21, the hydraulic oil discharged from the assist pump 61 of the assist regeneration system 102 (see FIG. 2) is guided to the main passage 23 through the assist passage 62. In addition, a first regeneration passage 75 is connected to the main passage 23, and hydraulic oil discharged from the main pump 21 is supplied to the regeneration motor 71 of the assist regeneration system 102 through the first regeneration passage 75.

  The main control valve 30 and the rod side pressure chamber 11 of the boom cylinder 10 are connected by a first passage 41, and the main control valve 30 and the bottom side pressure chamber 12 of the boom cylinder 10 are connected by a second passage 42. The second passage 42 is connected to a second regenerative passage 72 into which a part of the hydraulic oil discharged from the bottom side pressure chamber 12 flows. The hydraulic oil that has flowed into the second regeneration passage 72 is supplied to the regeneration motor 71 of the assist regeneration system 102 (see FIG. 2).

  The main control valve 30 switches supply and discharge of hydraulic oil to and from the boom cylinder 10. The main control valve 30 is operated by the pilot pressure of hydraulic oil supplied from the pilot pump 22 to the pilot chambers 31 and 32 through the pilot valve 24 as the crew of the excavator manually operates the operation lever.

  When the pilot pressure is supplied to the pilot chamber 31, the main control valve 30 is switched to the position a. As a result, the hydraulic oil discharged from the main pump 21 is supplied to the rod-side pressure chamber 11 through the first passage 41, and the hydraulic oil in the bottom-side pressure chamber 12 is discharged to the tank T through the second passage 42. As a result, the piston rod 13 in the boom cylinder 10 moves downward in FIG. 1, the boom cylinder 10 contracts, and the boom 1 descends.

  When the pilot pressure is supplied to the pilot chamber 32, the main control valve 30 is switched to the position b. As a result, the hydraulic oil discharged from the main pump 21 is supplied to the bottom side pressure chamber 12 through the second passage 42, and the hydraulic oil in the rod side pressure chamber 11 is discharged to the tank T through the first passage 41. As a result, the piston rod 13 in the boom cylinder 10 moves upward in FIG. 1, the boom cylinder 10 extends, and the boom 1 rises.

  On the other hand, when the pilot pressure is not supplied to the pilot chambers 31 and 32, the main control valve 30 is switched to the position c. Thereby, the supply and discharge of the hydraulic oil to and from the boom cylinder 10 is blocked. As a result, the expansion and contraction of the boom cylinder 10 stops, and the boom 1 is held at a predetermined position.

  Thus, the main control valve 30 has three switching positions: a contracted position a for contracting the boom cylinder 10, an extended position b for extending the boom cylinder 10, and a cutoff position c for holding the load of the boom cylinder 10. ing.

  The fluid pressure control system 101 further includes an assist regeneration system 102 shown in FIG. Next, the assist regeneration system 102 will be described with reference to FIG.

  The assist regeneration system 102 regenerates the hydraulic oil discharged from the main pump 21 or the hydraulic oil discharged from the bottom-side pressure chamber 12 when the boom cylinder 10 is contracted, and regenerates the boom cylinder 10. And assist control for applying assisting force during operation.

  The assist regeneration system 102 includes a regeneration motor 71, a motor generator 81, a battery 91, an inverter 92, an assist pump 61, a first regeneration passage 75, a second regeneration passage 72, and an assist passage 62. .

  The motor generator 81 is a rotating electrical machine having a function as an electric motor that rotates the electric power of the battery 91 to drive the assist pump 61 and a function as a generator that generates electric power by the rotation of the regenerative motor 71.

  The motor generator 81, the regenerative motor 71, and the assist pump 61 rotate coaxially. When the rotation shaft of the motor generator 81 rotates, the rotation shafts of the regenerative motor 71 and the assist pump 61 rotate in conjunction with each other. Similarly, when the rotating shaft of the regenerative motor 71 rotates, the rotating shafts of the motor generator 81 and the assist pump 61 rotate together.

  The regenerative motor 71 is a variable capacity motor capable of controlling the output torque by controlling the inclination angle of the swash plate. The regenerative motor 71 is driven by hydraulic oil discharged from the main pump 21 and supplied through the first regenerative passage 75 or hydraulic oil discharged from the bottom pressure chamber 12 of the boom cylinder 10 and supplied through the second regenerative passage 72. Is done. The inclination angle of the swash plate of the regenerative motor 71 is controlled by an inclination angle controller 73. The tilt angle controller 73 is controlled by the controller 50. By controlling the inclination angle of the swash plate of the regenerative motor 71, the capacity of the regenerative motor 71 changes, and the maximum value of the torque that can be generated by the regenerative motor 71 changes.

  The first regenerative passage 75 is provided with a first switching valve 76 that switches between supply and stop of hydraulic oil to the regenerative motor 71. The first switching valve 76 is an electromagnetic valve having a communication position f for supplying hydraulic oil to the regenerative motor 71 and a shut-off position g for stopping the supply of hydraulic oil to the regenerative motor 71. Can be switched.

  The second regeneration passage 72 is provided with a second switching valve 74 that switches between supply and stop of hydraulic oil to the regeneration motor 71. The second switching valve 74 is an electromagnetic valve having a communication position d for supplying hydraulic oil to the regenerative motor 71 and a shut-off position e for stopping the supply of hydraulic oil to the regenerative motor 71. Can be switched.

  The assist pump 61 is a variable displacement pump that can adjust the inclination angle of the swash plate. The assist pump 61 is driven by the motor generator 81 and supplies hydraulic oil to the main passage 23 through the assist passage 62. The inclination angle of the swash plate of the assist pump 61 is controlled by an inclination angle controller 63. The tilt angle controller 63 is controlled by the controller 50. By controlling the inclination angle of the swash plate of the assist pump 61, the capacity of the assist pump 61 changes, and the maximum value of the flow rate of hydraulic oil that can be discharged by the assist pump 61 changes.

  The assist passage 62 is provided with a third switching valve 64 that switches between supply and stop of hydraulic oil to the main passage 23. The third switching valve 64 is an electromagnetic valve having a communication position h for supplying hydraulic oil to the main passage 23 and a blocking position i for stopping the supply of hydraulic oil to the main passage 23. Can be switched.

The motor generator 81 is connected to the battery 91 via the inverter 92.
The inverter 92 is controlled by the controller 50 and converts direct current into alternating current or alternating current into direct current. When the motor generator 81 is caused to function as an electric motor, DC power output from the battery 91 is converted into three-phase AC power having an arbitrary frequency and supplied to the motor generator 81. On the other hand, when the motor generator 81 functions as a generator, the three-phase AC power output from the motor generator 81 is converted into DC power and supplied to the battery 91. The battery 91 will be described in detail later.

  With reference to FIG.1 and FIG.2, the effect | action of the fluid pressure control system 101 of a hybrid construction machine is demonstrated.

  First, regenerative control by the assist regenerative system 102 performed as necessary when the boom 1 is lowered will be described.

  When a lever operation for contracting the boom cylinder 10 is performed by a crew member of the hydraulic excavator, the main control valve 30 is switched to the contracted position a. As a result, the hydraulic oil is supplied to the rod side pressure chamber 11 of the boom cylinder 10 and the hydraulic oil is discharged from the bottom side pressure chamber 12.

  At this time, when the battery 91 needs to be charged, the second switching valve 74 is switched to the communication position d, and a part of the hydraulic oil discharged from the bottom side pressure chamber 12 passes through the second regenerative passage 72. 71. At the same time, the inclination angle of the swash plate of the assist pump 61 is controlled so that the capacity of the assist pump 61 is minimized.

  Thus, since the motor generator 81 rotates in synchronization with the regenerative motor 71, the motor generator 81 generates power and charges the battery 91. That is, the hydraulic energy of the hydraulic oil discharged from the boom cylinder 10 is converted into electric energy.

  On the other hand, when it is not necessary to charge the battery 91, the second switching valve 74 is switched to the cutoff position e, and all the hydraulic oil discharged from the bottom pressure chamber 12 of the boom cylinder 10 is tanked through the second passage 42. Discharged to T.

  Next, regenerative control by the assist regenerative system 102 performed by the hydraulic oil supplied from the main pump 21 will be described.

  In a state where there is no lever operation by the crew of the hydraulic excavator, the main control valve 30 is in the cutoff position c, and each actuator including the boom cylinder 10 mounted on the hydraulic excavator is stopped. Even in this state, the main pump 21 maintains driving by the rotation of the engine 8 and enters a standby state.

  When there is no lever operation by the crew of the excavator, that is, when each actuator including the boom cylinder 10 mounted on the excavator continues for a predetermined time, the second switching valve 74 is switched to the cutoff position e. At the same time, the first switching valve 76 is switched to the communication position f, and the hydraulic oil discharged from the main pump 21 in the standby state is supplied to the regeneration motor 71 through the first regeneration passage 75. At the same time, the inclination angle of the swash plate of the assist pump 61 is controlled so that the capacity of the assist pump 61 is minimized.

  Thus, since the motor generator 81 rotates in synchronization with the regenerative motor 71, the motor generator 81 generates power and charges the battery 91. As described above, the hydraulic oil discharged from the main pump 21 in the standby state is not returned to the tank but is guided to the regenerative motor 71 for effective use. That is, the hydraulic energy of the hydraulic oil discharged from the main pump 21 is converted into electric energy.

  As described above, when the state where there is no lever operation by the crew of the hydraulic excavator continues for a predetermined time, the regenerative motor 71 is rotated by the hydraulic oil discharged from the main pump 21 so that the motor generator 81 serves as a generator. Standby charging is performed, in which the battery 91 is charged. During standby charging, the capacity of the main pump 21 is controlled to be optimal for standby charging, and the rotational speed of the engine 8 is also controlled to be optimal for standby charging. The flow rate of the hydraulic oil is stable with little fluctuation. As described above, in standby charging, regeneration is performed by hydraulic oil that is stably discharged from the main pump 21, and therefore, fluctuation in charging current is small and stable continuous compared to regeneration performed when the boom 1 is lowered. Charging is performed.

  Next, assist control by the assist regeneration system 102 performed as necessary when the boom 1 is raised will be described.

  When a lever operation for extending the boom cylinder 10 is performed by a crew member of the hydraulic excavator, the main control valve 30 is switched to the extended position b. As a result, hydraulic oil is supplied to the bottom side pressure chamber 12 of the boom cylinder 10 and hydraulic oil in the rod side pressure chamber 11 is discharged to the tank T through the first passage 41.

  Since the engine that drives the main pump 21 and the like is operated at a predetermined rotational speed and load with good operating efficiency, when it is desired to quickly extend the boom cylinder 10, only the discharge flow rate from the main pump 21 causes the bottom pressure chamber. The flow rate of the hydraulic oil supplied to 12 may be insufficient. In such a case, assist control by the assist regeneration system 102 is executed.

  During the assist control, the third switching valve 64 is switched to the communication position h, and the motor generator 81 is driven as an electric motor by the battery 91 to drive the assist pump 61. At the same time, the inclination angle of the swash plate of the regenerative motor 71 is controlled so that the torque of the regenerative motor 71 is minimized. As a result, the hydraulic oil discharged from the assist pump 61 joins the main passage 23 through the assist passage 62, so that the assisting force by the assist pump 61 can be applied when the boom cylinder 10 is extended. Accordingly, the boom cylinder 10 can be quickly extended. Thus, when the motor generator 81 functions as an electric motor, the battery 91 functions as a drive source for the boom cylinder 10 (drive body).

  The control system 100 of the hybrid construction machine includes an SOC estimation device 103 that estimates a state of charge (SOC) of the battery 91. Hereinafter, the SOC estimation apparatus 103 will be described with reference to FIG.

  The battery 91 is a secondary battery having a rated battery capacity of 50 Ah (ampere hour), for example. The battery 91 has a large number of cells that can be charged and discharged, and each cell is connected in series. As the battery 91, for example, a lithium ion battery is used.

  The SOC estimation device 103 includes a battery state detection unit 93 that detects the state of the battery 91, an SOC calculation unit 94 that calculates the SOC of the battery 91, and a battery capacity estimation unit 95 that estimates the full battery capacity of the battery 91. Prepare. Note that the SOC estimation device 103 may be provided in the controller 50.

  The battery state detector 93 includes a voltage detector 93A that detects the voltage of the battery 91, a current detector 93B that detects the current of the battery 91, and a temperature detector 93C that detects the temperature of the battery 91. The voltage detection unit 93A, current detection unit 93B, and temperature detection unit 93C detect the voltage, current, and temperature of the battery 91 with a measurement cycle of several ms, respectively. For example, the voltage detection unit 93A detects a voltage (cell voltage) between electrodes of a cell provided inside the battery. The current detector 93 </ b> B detects the magnitude of the current flowing through each cell of the battery 91. The temperature detector 93 </ b> C detects the surface temperature of the battery case of the battery 91.

  The detection results of the voltage detection unit 93A, the current detection unit 93B, and the temperature detection unit 93C are output to the SOC calculation unit 94. In the current of the battery 91, the charging current at the time of charging is indicated by a positive value, and the discharging current at the time of discharging is indicated by a negative value.

  The SOC calculation unit 94 includes two calculation units: an open-circuit voltage SOC calculation unit 94A as a second SOC calculation unit, and a current integration SOC calculation unit 94B as a first SOC calculation unit.

  The open circuit voltage SOC calculation unit 94A calculates the open circuit voltage SOC based on the open circuit voltage of the battery 91 detected by the voltage detection unit 93A. The open circuit voltage is a cell voltage when charging and discharging of the battery 91 are stopped.

  The open-circuit voltage SOC calculation unit 94A stores an open-circuit voltage SOC map (see FIG. 8) in which the open-circuit voltage and the open-circuit voltage SOC are associated with each other for each battery temperature. The open-circuit voltage SOC calculation unit 94A acquires the battery temperature from the temperature detection unit 93C, acquires the open-circuit voltage of the battery 91 from the voltage detection unit 93A, and corresponds to the temperature and the open-circuit voltage with reference to the open-circuit voltage SOC map. The attached open circuit voltage SOC is calculated.

  Thus, the calculation accuracy of the open-circuit voltage SOC can be increased by using the open-circuit voltage SOC map for each battery temperature in the open-circuit voltage SOC calculation unit 94A. Open-circuit voltage SOC calculation unit 94A outputs the calculated open-circuit voltage SOC to current integration SOC calculation unit 94B and battery capacity estimation unit 95.

  The current integration SOC calculation unit 94B is based on the initial SOC value (SOC initial value) of the battery 91, the integrated value of the battery current detected by the current detection unit 93B, and the full battery capacity of the battery 91. Calculate the SOC. For example, the open-circuit voltage SOC output from the open-circuit voltage SOC calculation unit 94A is set as the SOC initial value. The SOC initial value is obtained before current integration is started by the current detector 93B. The battery 91 may be fully charged to set the SOC initial value to 100%, or the SOC initial value may be obtained in any way. Specifically, the current integration SOC is calculated by the following equation (1).

  In the present embodiment, the current integration SOC calculation unit 94B integrates the current value (A) for each measurement cycle during the charge / discharge time (accumulation period) (hr) during which the battery 91 is discharged or charged. Calculate the integrated amount. Current integration SOC calculation unit 94B calculates an integrated SOC by dividing the integrated amount of current by the full battery capacity of battery 91, and adds the integrated SOC to the SOC initial value to calculate current integration SOC. Note that the value of the full battery capacity in the equation (1) used when calculating the current integration SOC is corrected according to the deterioration of the battery 91 as will be described later.

  The open circuit voltage SOC and the current integration SOC calculated by the SOC calculation unit 94 are output to the controller 50. The controller 50 limits charging / discharging of the battery 91 based on the comparison between the open circuit voltage SOC or the current integration SOC and the charge / discharge limit threshold. For example, when the current integration SOC is higher than the charge / discharge limit threshold, the battery 91 is not charged by controlling the inverter 92 to prevent the battery 91 from being overcharged. When the current integration SOC is lower than the charge / discharge limit threshold, the battery 91 is prevented from discharging.

  Generally, when the magnitude of the discharge current of the battery 91 is constant, the discharge time of the battery 91 becomes shorter as the deterioration of the battery 91 increases with repeated charge / discharge, and the full charge capacity at the time of full charge is reduced. Decreases. Therefore, the battery capacity estimation unit 95 estimates the full battery capacity of the battery 91 according to the degree of deterioration of the secondary battery. The battery capacity estimation unit 95 includes a total charge / discharge time determination unit 95A that determines whether the total charge / discharge time of the battery 91 has reached a predetermined time, and a standby charge determination that determines whether the battery 91 is in a standby charge state. Part 95B.

  Next, an SOC estimation method for estimating the SOC of the battery 91 will be described with reference to FIGS.

  First, an SOC calculation method will be described with reference to FIGS. 4 is a flowchart showing a procedure of calculation processing executed by the SOC calculation unit 94 of the SOC estimation device 103, FIG. 5 is a flowchart showing a procedure of calculation processing of the open circuit voltage SOC, and FIG. 6 is a current integration SOC. It is a flowchart which shows the procedure of this arithmetic processing.

  As shown in FIG. 4, in step 11, the ignition key of the excavator is set to ON, and the SOC estimation device 103 is activated.

  In step 12, the open-circuit voltage SOC calculation unit 94A calculates the open-circuit voltage SOC as the SOC initial value. Thus, at the time of starting the hydraulic excavator, the open circuit voltage SOC is calculated before the battery 91 is charged and discharged. The above steps 11 and 12 are performed only when the excavator is started.

  Hereinafter, with reference to FIG. 5, the calculation process of open-circuit voltage SOC (the calculation process of steps 12 and 16) executed by open-circuit voltage SOC calculation unit 94 </ b> A will be described.

  In step 51, the battery temperature is acquired from the temperature detector 93C, and the average temperature Ta of the plurality of cells is calculated.

  In step 52, the cell voltage of the battery 91 is acquired as the open voltage Vb from the voltage detector 93A.

  In step 53, the open circuit voltage SOC associated with the average temperature Ta and the open circuit voltage Vb of the battery 91 is calculated with reference to the open circuit voltage SOC map (see FIG. 8). For example, when the average temperature Ta of the cell is 30 ° C. and the open circuit voltage Vb is 3.95 V, the open circuit voltage SOC is calculated as 80% from the open circuit voltage SOC map of FIG. Thus, the open circuit voltage SOC calculation process is completed, and the process returns to the process shown in FIG. In addition to the cell average temperature Ta of 30 ° C., for example, a plurality of maps of the open circuit voltage SOC with respect to the open circuit voltage Vb in the case of 0 ° C., 10 ° C., and 20 ° C. are provided. The open circuit voltage SOC is calculated using a map of temperatures close to the calculated cell average temperature Ta.

  In step 13, it is determined whether charging / discharging of the battery 91 is performed. Specifically, it is determined whether or not the battery current Ib acquired from the current detection unit 93B exceeds a discharge threshold and a charge threshold for determining whether to stop charging or discharging the battery 91. For example, the charging threshold is set to 5A and the discharging threshold is set to -5A.

  If it is determined in step 13 that the current Ib of the battery 91 exceeds the range from the discharge threshold value to the charge threshold value, that is, the battery 91 is being charged / discharged, the process proceeds to step 14 where the current integration is performed. The SOC calculation unit 94B calculates the current integration SOC.

  Below, with reference to FIG. 6, the calculation process (current calculation process of step 14) of the current integration SOC executed by the current integration SOC calculation unit 94B will be described.

  In step 61, the current Ib of the battery 91 is acquired from the current detector 93B for each measurement cycle.

  In step 62, the integrated SOC based on the integrated value of the current Ib of the battery 91 is calculated by the above equation (1). Specifically, within the accumulation period, each current amount obtained by multiplying the measurement period by the current Ib is added to calculate an integrated value of the current (battery current × charge / discharge period). Then, the integrated SOC is calculated by dividing the integrated value of the current by the full battery capacity of the battery 91. The full battery capacity of the battery 91 uses the rated battery capacity of the battery 91 as an initial value.

  The cumulative period is a period from when the current Ib exceeds the calculation stop range from the discharge threshold to the charge threshold until the current Ib within the calculation stop range continues for a predetermined time. That is, the cumulative period is a period from the start of charging or discharging of the battery 91 to the end of charging or discharging of the battery 91.

  In step 63, the integrated current SOC calculated in step 62 is added to the open circuit voltage SOC as the SOC initial value calculated in step 12 to calculate the current integrated SOC. For example, when the full battery capacity of the battery 91 is 50 Ah of the rated battery capacity, the open-circuit voltage SOC calculated in step 12 is 70%, and discharge is performed at a discharge current of 10 A for 1 hour, the following formula (2) is satisfied. The current integration SOC is calculated as 50%. The current integration SOC calculation process is thus completed, and the process returns to the process shown in FIG.

  The calculation of the current integrated SOC in step 14 is performed in step 15 because it is determined in step 13 that the current Ib of the battery 91 does not exceed the range from the discharge threshold value to the charge threshold value, that is, the battery 91 is not charged or discharged. The process is continued until it is determined that the state has continued for 3 minutes. The duration time is determined according to a decrease in current due to a change in the internal resistance of the battery 91, a rising characteristic, or the like when charging / discharging of the battery 91 is stopped.

  If it is determined in step 15 that the state in which the battery 91 is not charged / discharged continues for 3 minutes, the process proceeds to step 16 where the open circuit voltage SOC is newly calculated. That is, unless the state in which the battery 91 is not charged / discharged continues for 3 minutes, the SOC of the battery 91 is continuously calculated by the current integration SOC calculation unit 94B. The calculation method of the open circuit voltage SOC in step 16 is the same as the above-described method described with reference to FIG. After step 16, the process returns to step 13 and the process is repeated.

  After the open circuit voltage SOC is calculated in step 16, when the current integrated SOC is calculated using the above equation (1) in step 14, not the open circuit voltage SOC calculated in step 12 but the step 16. The open circuit voltage SOC calculated in this way is used as the SOC initial value. In other words, when calculating the current integrated SOC in step 14, the open-circuit voltage SOC calculated in step 12 is used only when the current integrated SOC is calculated for the first time after the excavator is started.

  As described above, the SOC calculation unit 94 calculates the current integration SOC or the open circuit voltage SOC according to the charge / discharge state of the battery 91. The calculated current integration SOC and open circuit voltage SOC are output to the controller 50 (see FIG. 3). The controller 50 compares the open-circuit voltage SOC or current integration SOC with the charge / discharge limit threshold, and forcibly prohibits charging / discharging of the battery 91 when the open-circuit voltage SOC or current integration SOC exceeds the charge / discharge limit value. Thus, overcharge and overdischarge of the battery 91 are prevented.

  Next, a method for estimating the full battery capacity of the battery 91 will be described with reference to FIG. FIG. 7 is a flowchart showing a procedure of calculation processing executed by the battery capacity estimation unit 95 of the SOC estimation apparatus 103.

  The following processing is performed after the ignition key of the hydraulic excavator is set to ON and the SOC estimation device 103 is activated.

  In step 71, it is determined whether or not the total charge / discharge time of the battery 91 has reached a predetermined time. Specifically, the charge / discharge time of the battery 91 is stored in the storage unit of the control board of the SOC estimation device 103, and whether or not the total of the stored charge / discharge time has reached a predetermined time. Determine.

  When the condition of step 71 is satisfied, that is, when it is determined in step 71 that the total charging / discharging time of the battery 91 has reached a predetermined time, the battery capacity estimation state for estimating the full battery capacity of the battery 91 is entered. Transition. The predetermined time is determined according to the degree of deterioration of the battery 91 due to repeated charge / discharge, and for example, a time corresponding to several months is set. As the predetermined time, instead of calculating the total charge / discharge time, the predetermined time may be determined based on mere passage of time.

  In step 72, it is determined whether or not the battery 91 is in a standby charging state. As described above, the standby charging state is a state in which each actuator of the hydraulic excavator is stopped, and the motor generator 81 functions as a generator when the regenerative motor 71 is rotated by the hydraulic oil discharged from the main pump 21. That is, the battery 91 is being charged. Whether or not the battery 91 is in the standby charging state is determined by the positions of the second switching valve 74 and the first switching valve 76 (see FIG. 2). Specifically, when the second switching valve 74 is switched to the cutoff position e by the command signal from the controller 50 and the first switching valve 76 is switched to the communication position f, the battery 91 is in the standby charging state. It is determined that there is. That is, whether or not the battery 91 is in the standby charging state is determined based on a signal output from the controller 50 to the second switching valve 74 and the first switching valve 76.

  If it is determined in step 72 that the battery 91 is not in the standby charging state, the calculation process is terminated and the process returns to step 71. On the other hand, if it is determined in step 72 that the battery 91 is in the standby charging state, the process proceeds to step 73, where the current integrated SOC acquired from the current integrated SOC calculation unit 94B and the open voltage SOC calculation unit 94A are acquired. The full battery capacity is estimated based on the open circuit voltage SOC. In the standby charging state, regeneration is performed by the hydraulic oil that is stably discharged from the main pump 21, so that fluctuation of the charging current is small and stable continuous charging is performed. Therefore, by performing the estimation of the full battery capacity in the standby charging state, it is possible to suppress a measurement error when integrating the current flowing through the battery 91, and therefore it is possible to improve the accuracy of the estimation of the full battery capacity.

  With reference to FIG. 9, the estimation method of the full battery capacity in step 73 is demonstrated. FIG. 9 is a flowchart showing the procedure of the method for estimating the full battery capacity.

  First, in step 91, the current SOC is acquired as the SOC initial value from the SOC calculation unit 94 in the standby charging state. For example, it is assumed that the SOC initial value is 50%. As the SOC initial value, the SOC calculated by either the open circuit voltage SOC calculation unit 94A or the current integration SOC calculation unit 94B may be used.

  In step 92, the current integration SOC at the time when the standby charging is completed is obtained from the current integration SOC calculation unit 94B. Here, when calculating the current integration SOC, the value obtained in step 91 is used as the SOC initial value in the above equation (1). For example, when the full battery capacity of the battery 91 is 50 Ah, which is the rated battery capacity, and the battery 91 is charged for 1 hour with a charging current of 10 A, the current integration SOC is calculated as 70% as shown in the following equation (3).

  In step 93, the difference between the SOC initial value acquired in step 91 and the current integrated SOC acquired in step 92 is taken, and the charge amount CI of the battery 91 by standby charging is calculated. Thus, in step 93, the charge amount CI of the battery 91 within a predetermined period during standby charging is calculated using the current integration SOC. Here, the charge amount CI is calculated as 20%.

  In step 94, the open-circuit voltage SOC at the time when standby charging is completed is obtained from the open-circuit voltage SOC calculation unit 94A. For example, it is assumed that the average temperature Ta of the cell is 30 ° C., the open circuit voltage Vb is 3.9 V, and the open circuit voltage SOC is calculated as 75% from the open circuit voltage SOC map.

  In step 95, the difference between the SOC initial value acquired in step 91 and the open circuit voltage SOC acquired in step 92 is taken, and the charge amount CV of the battery 91 by standby charging is calculated. Thus, in step 94, the charge amount CV of the battery 91 within a predetermined period during standby charging is calculated using the open circuit voltage SOC. Here, the charge amount CV is calculated as 25%.

  In step 96, the ratio between the charge amount CI of the battery 91 calculated from the current integration SOC and the charge amount CV of the battery 91 calculated from the open circuit voltage SOC is calculated. Here, the ratio is calculated as 0.8.

  Here, in the calculation formula (1) of the current integration SOC, the full battery capacity of the battery 91 stored in the storage unit described later is used. Therefore, when the battery 91 is deteriorated and the full battery capacity is reduced, the actual full battery capacity when calculating the current integrated SOC becomes smaller than the full battery capacity used in the calculation formula (1). Therefore, the current integration SOC calculated in step 92 is a value that does not reflect the deterioration of the battery 91 after the full battery capacity of the battery 91 is stored in the storage unit.

  On the other hand, in the calculation method of the open circuit voltage SOC, when the battery 91 deteriorates and the full charge capacity decreases, the cell voltage decreases according to the degree of deterioration of the battery 91 even if the battery 91 is discharged at the same discharge rate for a certain time. Therefore, open circuit voltage SOC is a value reflecting the degree of deterioration of battery 91.

  For this reason, the ratio between the charge amount of the battery 91 calculated from the current integration SOC and the charge amount of the battery 91 calculated from the open circuit voltage SOC represents the degree of deterioration of the battery 91.

  In step 97, the full battery capacity of the current battery 91 is estimated by multiplying the full battery capacity of the current battery 91 by the ratio calculated in step 96. Here, the full battery capacity of the current battery 91 is estimated to be 40 Ah. In this way, the deterioration degree of the battery 91 is determined based on the ratio between the charge amount of the battery 91 within a predetermined period calculated from the current integration SOC and the charge amount of the battery 91 within a predetermined period calculated from the open-circuit voltage SOC. The full charge capacity corresponding to the is estimated. That is, the full charge capacity of the battery 91 is estimated by comparing the current integration SOC within a predetermined period estimated by the current integration SOC calculation unit 94B with the open-circuit voltage SOC estimated by the open-circuit voltage SOC calculation unit 94A after the lapse of the predetermined period. Is done.

  Here, since the cell voltage is not stable until a predetermined time elapses after the standby charging is completed, there is a possibility that an accurate open-circuit voltage cannot be detected. Therefore, the acquisition of the open circuit voltage SOC in step 94 is desirably performed after a predetermined time has elapsed, for example, a few minutes after standby charging ends. Thereby, the estimation accuracy of the full charge capacity of the battery 91 can be improved. However, when charging / discharging of the battery 91 is performed before a predetermined time elapses after standby charging is completed, it is difficult to accurately grasp the charging amount during standby charging. Therefore, it is desirable not to charge / discharge the battery 91 until the predetermined time has elapsed after the standby charging is completed and the open circuit voltage SOC is calculated. Alternatively, it is desirable not to estimate the full charge capacity when charging / discharging of the battery 91 is performed before a predetermined time elapses after standby charging ends.

  In step 98, the estimated full charge capacity (40Ah) of the battery 91 estimated in step 97 is output to the current integration SOC calculation unit 94B, and the full charge capacity in the above equation (1) is updated to the estimated full charge capacity. That is, the battery capacity estimation unit 95 (see FIG. 3) outputs the estimated full charge capacity of the estimated battery 91 to the current integration SOC calculation unit 94B, and converts the full charge capacity in the above equation (1) to the estimated full charge capacity. Update. Here, the full charge capacity in the above formula (1) is updated from the rated battery capacity of 50 Ah to the estimated full charge capacity of 40 A. The current integration SOC calculation unit 94B uses the estimated full charge capacity of the battery 91 estimated in step 97 when calculating the current integration SOC using the above equation (1). In other words, after the full charge capacity of the battery 91 is estimated by the battery capacity estimation unit 95, the battery estimated by the battery capacity estimation unit 95 is calculated when calculating the current integration SOC in step 14 of FIG. An estimated full charge capacity of 91 is used. Therefore, after the full charge capacity is updated, the current integration SOC calculated by the current integration SOC calculation unit 94B (current integration SOC calculated in step 14 of FIG. 4) takes into account the degree of deterioration of the battery 91. Value.

  The SOC estimation device 103 has a storage unit that stores the full charge capacity of the battery 91. The storage unit includes, for example, an EEPROM or a flash memory, and the storage unit stores the full charge capacity estimated by the battery capacity estimation unit 95. The current integration SOC calculation unit 94B calculates the current integration SOC from the above equation (1) using the full charge capacity stored in the storage unit. By storing the full charge capacity in the storage unit, it is possible to calculate the current integrated SOC reflecting the battery deterioration even when the SOC estimation device 103 is restarted.

  The current integration SOC calculated by the current integration SOC calculation unit 94B is a value that takes into account the degree of deterioration of the battery 91. Therefore, since the SOC of the battery 91 is accurately estimated, the controller 50 can limit charging / discharging of the battery 91 according to the degree of deterioration of the battery 91. Therefore, overcharging and overdischarging of the battery 91 can be prevented with high accuracy, and the life of the battery 91 can be extended. Conventionally, it has been necessary to open the battery 91 in order to calculate the SOC in consideration of the degree of deterioration. However, in this embodiment, the SOC of the battery 91 can be estimated with high accuracy without opening the battery 91 even during charging / discharging of the battery 91 (steps 13 and 15 in FIG. 4).

  After the full charge capacity in the above formula (1) is updated to the estimated full charge capacity estimated in step 97 in step 98, the total charge / discharge time of the battery 91 reaches a predetermined time and the battery 91 is in standby charge. The case where it will be in a state is demonstrated. In this case, the full battery capacity of the battery 91 is estimated again according to the flowchart shown in FIG. At that time, when the current integrated SOC is calculated in step 92, the estimated full charge capacity updated as the full battery capacity in the above equation (1) is used. Here, 40 Ah (see step 97 in FIG. 9) is used as shown in the specific example. Then, if the ratio of CI and CV is calculated as 0.9 in step 96, for example, the full charge capacity of the battery 91 is calculated by multiplying the updated estimated full charge capacity 40Ah and 0.9 in step 97. It is estimated to be 36 Ah. In step 98, the full charge capacity in the above equation (1) is re-updated from 40 Ah to 36 Ah estimated in step 97. Thus, every time the total charging / discharging time of the battery 91 reaches a predetermined time and the battery 91 is in the standby charging state, the full battery capacity of the battery 91 is estimated.

  Here, when calculating the current integration SOC in step 92 of FIG. 9, instead of using the estimated full charge capacity updated as the full battery capacity in the above equation (1), the rated battery capacity of the battery 91 is used. You may do it. In this case, when the estimated value of the full charge capacity of the battery 91 is calculated in step 97, it is necessary to multiply the ratio of CI and CV calculated in step 96 by the rated battery capacity of the battery 91. is there.

  As described above, when the current integrated SOC is calculated in step 92 of FIG. 9, the updated estimated full charge capacity may be used as the value of the full battery capacity in the above equation (1), or the rated battery Capacity may be used.

  In FIG. 7, after the full battery capacity is estimated in step 73, the total charge / discharge time count of the battery 91 is reset in step 74. Thereafter, the arithmetic processing shown in FIG.

  Next, a modification of the first embodiment will be described with reference to FIG. FIG. 10 is a flowchart showing the procedure of a modified example of the full battery capacity estimation method in step 73 of FIG.

  In this modification, the estimation method of the full battery capacity in step 73 in FIG. 7 is different from the above method. In the first embodiment, as shown in FIG. 9, the full charge capacity is calculated based on the ratio between the charge amount of the battery 91 calculated from the current integration SOC and the charge amount of the battery 91 calculated from the open circuit voltage SOC. It was an estimate. Instead, the full battery capacity may be estimated by the method shown in FIG.

  Steps 91, 92, and 94 in FIG. 10 are the same as the procedure shown in FIG.

  In the following step 96 ′, the difference between the current integrated SOC calculated in step 92 and the open circuit voltage SOC calculated in step 94 is calculated. Here, the difference is calculated as 5%.

  In step 97 ′, the full battery capacity is estimated with reference to a map in which the relationship between the difference between the current integration SOC and the open circuit voltage SOC and the full charge capacity is defined. The map is determined in advance by experiments or the like and stored in the battery capacity estimation unit 95. Here, the full battery capacity is estimated to be 40 Ah from the map. Thus, in this modification, the full charge capacity according to the degree of deterioration of the battery 91 is estimated based on the difference between the current integrated SOC after the lapse of the predetermined period and the open circuit voltage SOC.

  In step 98, the estimated full charge capacity (40Ah) of the battery 91 estimated in step 97 'is output to the current integration SOC calculation unit 94B, and the full charge capacity in the above equation (1) is updated to the estimated full charge capacity. .

  According to the above 1st Embodiment, there exists an effect shown below.

  Since the current integration SOC calculation unit 94B calculates the current integration SOC using the full battery capacity estimated according to the degree of deterioration of the secondary battery, the SOC of the battery 91 can be accurately estimated. Therefore, overcharge and overdischarge of the battery 91 can be prevented with high accuracy, and the life of the battery 91 can be extended.

  In addition, the full battery capacity is estimated in a standby charging state in which stable continuous charging is performed with small fluctuations in charging current. Therefore, the full battery capacity of the battery 91 can be accurately estimated.

Second Embodiment
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. Below, it demonstrates centering on a different point from the said 1st Embodiment.

  FIG. 11 is a flowchart showing a procedure of calculation processing executed by the battery capacity estimation unit 95 of the SOC estimation apparatus 103. The same steps as those in the flowchart of FIG.

  In the first embodiment, the full battery capacity is estimated based on the current integration SOC acquired from the current integration SOC calculation unit 94B and the open-circuit voltage SOC acquired from the open-circuit voltage SOC calculation unit 94A (FIG. 7). Step 73). On the other hand, in the second embodiment, the full battery capacity is estimated based on the internal resistance and temperature of the battery 91 as shown in step 73 ′ of FIG. Hereinafter, the method for estimating the full battery capacity will be described in detail.

  With reference to FIG. 12, the full battery capacity estimation method in step 73 ′ of FIG. 11 will be described. FIG. 12 is a flowchart showing the procedure of the method for estimating the full battery capacity in step 73 ′ of FIG.

In step 121, the internal resistance of the battery 91 is acquired from the battery state detection unit 93.
Specifically, the internal resistance is detected from the voltage detected by the voltage detection unit 93A and the current detected by the current detection unit 93B, and the battery state detection unit is detected every measurement cycle of the voltage detection unit 93A and the current detection unit 93B. The internal resistance is obtained from 93. The internal resistance may be acquired for every predetermined measurement cycle, for example, 10 measurement cycles, without acquiring it for each measurement cycle of the voltage detection unit 93A and the current detection unit 93B. Here, it is assumed that the detected internal resistance Rd of the battery 91 is 4.62 mΩ.

  When the voltage when the battery 91 is opened is E0, the terminal voltage of the battery 91 when current is supplied from the battery 91 to the load R, and the battery current is I, the detected internal resistance Rd is Rd = (E0−E) / I can be obtained. Further, when the value of the load R is known, the detected internal resistance Rd can be obtained by Rd = R × (E / E0-1) without using the battery current I.

  In step 122, the average cell temperature Ta is obtained from the temperature detector 93C. Here, it is assumed that the average temperature Ta of the cell is 0 ° C. Then, the ideal internal resistance Ri is calculated with reference to a map in which the relationship between the average temperature Ta of the cell and the ideal internal resistance Ri is defined. Here, the ideal internal resistance Ri is an internal resistance when the battery 91 is not deteriorated. The map is determined in advance by experiments or the like and stored in the battery capacity estimation unit 95. Here, the ideal internal resistance Ri is calculated as 4.2 mΩ from the map.

  In step 123, a ratio between the detected internal resistance Rd and the ideal internal resistance Ri is calculated. Here, the ratio is calculated as 1.1.

  Generally, the internal resistance of the battery 91 increases as the deterioration of the battery 91 increases as charging / discharging is repeated. Therefore, the ratio between the detected internal resistance Rd and the ideal internal resistance Ri represents the degree of deterioration of the battery 91.

  In step 124, the estimated full charge capacity ratio of the battery 91 is calculated with reference to a map in which the relationship between the ratio of the detected internal resistance Rd and the ideal internal resistance Ri and the estimated full charge capacity ratio is defined. Here, the estimated full charge capacity ratio is a value in which the full charge capacity of the battery 91 in a state where the battery 91 is not deteriorated is 100%. The map is determined in advance by experiments or the like and stored in the battery capacity estimation unit 95. Here, the estimated full charge capacity ratio is calculated as 95% from the map.

  In step 125, the current full battery capacity of the battery 91 is estimated from the current full battery capacity of the battery 91 and the estimated full charge capacity ratio calculated in step 124. Here, the full battery capacity of the current battery 91 is estimated to be 47.5 Ah. In this way, the full charge capacity corresponding to the degree of deterioration of the battery 91 is estimated based on the internal resistance and temperature of the battery 91.

  In step 126, the estimated full charge capacity (47.5 Ah) of the battery 91 estimated in step 125 is output to the current integration SOC calculation unit 94B, and the full charge capacity in the above equation (1) is updated to the estimated full charge capacity. To do.

  Also in the second embodiment described above, the same operational effects as in the first embodiment are obtained.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  For example, in the above-described embodiment, the case where the motor generator 81 functions as a generator and the battery 91 is charged while the actuators of the excavator are stopped is described as standby charging. Instead of this, standby charging is a case where the secondary battery is fixedly charged using, for example, an electrical outlet installed in a home while the electric vehicle (driving body) using the secondary battery as a drive source is stopped. Also good. In stationary charging, charging current fluctuation is small and stable continuous charging is performed. Thus, the SOC estimation apparatus according to the embodiment of the present invention can be applied to a secondary battery mounted on an electric vehicle or a hybrid vehicle.

DESCRIPTION OF SYMBOLS 100 Hybrid construction machine control system 101 Fluid pressure control system 102 Assist regeneration system 103 SOC estimation apparatus 10 Boom cylinder (actuator, drive body)
21 Main pump (fluid pressure pump)
50 Controller 71 Regenerative motor 81 Motor generator (rotary electric machine)
91 Battery (secondary battery)
93A Voltage detection unit 93B Current detection unit 93C Temperature detection unit 94A Open-circuit voltage SOC calculation unit (second SOC calculation unit)
94B Current integration SOC calculation unit (first SOC calculation unit)
95 Battery capacity estimation unit 95A Total charge / discharge time determination unit 95B Standby charge determination unit

Claims (6)

An SOC estimation device for estimating the SOC of a secondary battery,
A current detector for detecting the current of the secondary battery;
An accumulated SOC is obtained by dividing the accumulated amount of current detected by the current detection unit within the accumulation period by the full battery capacity of the secondary battery, and the accumulated SOC is calculated as the SOC of the secondary battery before the accumulation period starts. A first SOC calculator that estimates the current integrated SOC by adding to the initial value;
A battery capacity estimation unit that estimates a full battery capacity of the secondary battery according to a degree of deterioration of the secondary battery,
The first SOC calculation unit updates the full battery capacity to the estimated full battery capacity of the secondary battery estimated by the battery capacity estimation unit. A voltage detector for detecting the voltage of the secondary battery;
A second SOC calculation unit that estimates an open circuit voltage SOC based on an open circuit voltage of the secondary battery detected by the voltage detection unit;
The battery capacity estimation unit compares the current integrated SOC acquired from the first SOC calculation unit with the open-circuit voltage SOC acquired from the second SOC calculation unit after the accumulation period has elapsed, thereby providing a full battery for the secondary battery. The SOC estimation apparatus according to claim 1, wherein the capacity is estimated.   When the battery capacity estimating unit obtains the current integrated SOC from the first SOC calculating unit, the first SOC calculating unit uses the rated battery capacity of the secondary battery as the full battery capacity. The SOC estimation apparatus according to claim 2, wherein: A total charge / discharge time determination unit for determining whether the total charge / discharge time of the secondary battery has reached a predetermined time;
The battery capacity estimation unit estimates the full battery capacity of the secondary battery when the total charge / discharge time determination unit determines that the total charge / discharge time of the secondary battery has reached the predetermined time. The SOC estimation apparatus according to claim 1, wherein the SOC estimation apparatus is characterized. A standby charge determination unit that determines whether the drive of the driving body using the secondary battery as a drive source is in a stopped state and determines whether or not the secondary battery is in a standby charge state;
The battery capacity estimating unit estimates the full battery capacity of the secondary battery when the standby charging determining unit determines that the battery is in a standby charging state. The SOC estimation apparatus described in 1. Estimating the full battery capacity of the secondary battery according to the degree of deterioration of the secondary battery,
Obtaining an initial SOC value of the secondary battery;
Calculate the integrated value of the current flowing through the secondary battery within the accumulation period,
Calculate the integrated SOC by dividing the integrated value by the estimated full battery capacity of the secondary battery,
Adding the accumulated SOC to the SOC initial value of the secondary battery before the start of the accumulation period to estimate a current accumulated SOC;
The SOC estimation method characterized by the above-mentioned.