JP2020092052A - Drive system - Google Patents

Abstract

To suppress deterioration of estimation accuracy of internal resistance of a secondary battery.SOLUTION: A drive system includes: a drive device; a secondary battery charged and discharged according to a drive state of the drive device; a current sensor for detecting a current of the secondary battery; a voltage sensor for detecting a voltage of the secondary battery; and a control unit for controlling the drive device and estimating internal resistance of the secondary battery using a plurality of sets of currents and voltages. The control unit then controls the drive device so that the secondary battery is charged when an energy storage ratio of the secondary battery is less than a predetermined ratio and estimates internal resistance after the energy storage ratio reaches or exceeds the predetermined ratio.SELECTED DRAWING: Figure 2

Description

The present invention relates to drive systems.

Conventionally, in this type of drive system, a drive device having a motor and the like, an assembled battery that has a plurality of battery cells and is charged and discharged according to the drive state of the drive device, and a voltage measurement that measures the voltage of each battery cell A circuit, a current measuring circuit for detecting the current of the assembled battery, and a memory for storing the measured voltage value measured by the voltage measuring circuit and the current measured value detected by the current measuring circuit have been proposed. (For example, see Patent Document 1). In this voltage system, a measured voltage value and a measured current value are stored in a memory for each first period, and an average voltage value and a plurality of measured voltage values of a plurality of measured voltage values measured in a second period including a plurality of first periods. The average current value of the current values is calculated, the difference value of the average voltage values of the continuous second period and the difference value of the average current value are calculated, and the average voltage value of the third period including the plurality of second periods is calculated. The slope of the regression line is calculated as the internal resistance from a plurality of pairs of the difference value and the difference value of the average current value.

JP, 2011-128010, A

In the region where the charge ratio of the secondary battery is comparatively low, the inventors of the present invention have found that when the charge of the secondary battery continues, the relationship between the charge ratio and the open-circuit voltage moves along the charging curve. When the secondary battery continues to be discharged, this relationship moves along a discharge curve different from the charging curve, and when the secondary battery is switched between charging and discharging, the relationship transitions between the charging curve and the discharging curve. It was confirmed. That is, in a region where the charge ratio of the secondary battery is relatively low, the same charge ratio is released depending on the charge/discharge history of the secondary battery (whether continuous charging or continuous discharging or switching between charging and discharging). It was confirmed that the voltage was different. When the relationship between the storage rate of the secondary battery and the open circuit voltage is different, the relationship between the current and the voltage of the secondary battery is also different. In the drive system described above, the internal resistance is estimated without considering the charge ratio of the secondary battery, so it is considered that the estimation accuracy of the internal resistance is not sufficient.

The drive system of the present invention mainly aims to suppress a decrease in estimation accuracy of the internal resistance of the secondary battery.

The drive system of the present invention employs the following means in order to achieve the main object described above.

The drive system of the present invention is
A drive,
A secondary battery that is charged and discharged according to the driving state of the driving device,
A current sensor for detecting the current of the secondary battery,
A voltage sensor for detecting the voltage of the secondary battery,
A control unit that controls the drive device and estimates the internal resistance of the secondary battery by using a plurality of sets of the current and the voltage,
A drive system comprising:
The control unit controls the driving device so that the secondary battery is charged when the storage ratio of the secondary battery is less than a predetermined ratio, and the internal unit after the storage ratio becomes equal to or higher than the predetermined ratio. To estimate resistance,
That is the summary.

In the drive system of the present invention, the internal resistance of the secondary battery is estimated using a plurality of sets of the secondary battery current detected by the current sensor and the secondary battery voltage detected by the voltage sensor. Then, when the storage ratio of the secondary battery is less than the predetermined ratio, the drive device is controlled so that the secondary battery is charged, and the internal resistance is estimated after the storage ratio becomes equal to or higher than the predetermined ratio. According to the analysis and the like, in the region where the charge ratio of the secondary battery is less than the predetermined ratio, the inventors have analyzed the open circuit voltage and the current and the voltage for the same charge ratio according to the charge/discharge history of the secondary battery. In the region where the charge ratio of the secondary battery is greater than or equal to a predetermined ratio, the open circuit voltage becomes almost the same for the same charge ratio regardless of the charge/discharge history of the secondary battery. It was confirmed that the variation in the relationship of was sufficiently small. Therefore, when the storage ratio of the secondary battery is less than the predetermined ratio, the estimation accuracy of the internal resistance of the secondary battery decreases by estimating the internal resistance after controlling the drive device to make the storage ratio equal to or higher than the predetermined ratio. Can be suppressed.

In the drive system of the present invention, the control unit may not estimate the internal resistance when the degree of dispersion of the plurality of currents is less than a predetermined degree. Further, the control unit may not estimate the internal resistance when the degree of variation in the storage ratio of the secondary battery when the current and the voltage are acquired is larger than a predetermined variation. By doing so, it is possible to avoid estimating the internal resistance with low accuracy.

It is a block diagram which shows the outline of a structure of the hybrid vehicle 20 which mounts the drive system as one Example of this invention. 7 is a flowchart showing an example of an internal resistance estimation routine executed by a battery ECU 52. It is explanatory drawing which shows an example of the relationship between the storage ratio SOC of the battery 50, and the open circuit voltage OCV. 7 is an explanatory diagram for explaining a method of estimating an internal resistance Rb of the battery 50. FIG.

Next, modes for carrying out the present invention will be described using examples.

FIG. 1 is a configuration diagram showing a schematic configuration of a hybrid vehicle 20 equipped with a drive system as one embodiment of the present invention. As illustrated, the hybrid vehicle 20 of the embodiment includes an engine 22, a planetary gear 30, motors MG1 and MG2, inverters 41 and 42, a battery 50 as a secondary battery, and a hybrid electronic control unit (hereinafter, “HVECU”) 70.

The engine 22 is configured as an internal combustion engine that outputs power using gasoline, light oil, or the like as fuel, and a crankshaft 26 is connected to a carrier of a planetary gear 30 via a damper 28. The operation of the engine 22 is controlled by an engine electronic control unit (hereinafter referred to as “engine ECU”) 24.

Although not shown, the engine ECU 24 is configured as a microprocessor centered on a CPU, and in addition to the CPU, includes a ROM for storing a processing program, a RAM for temporarily storing data, an input/output port, and a communication port. Prepare Signals from various sensors necessary for controlling the operation of the engine 22, for example, a crank angle θcr from a crank position sensor 23 that detects a rotational position of a crankshaft 26 of the engine 22 are input to the engine ECU 24 via an input port. Has been entered. Various control signals for controlling the operation of the engine 22 are output from the engine ECU 24 through the output port. The engine ECU 24 calculates the rotation speed Ne of the engine 22 based on the crank angle θcr from the crank position sensor 23.

The planetary gear 30 is configured as a single pinion type planetary gear mechanism. The sun gear of the planetary gear 30 is connected to the rotor of the motor MG1. The ring gear of the planetary gear 30 is connected to a drive shaft 36 that is connected to the drive wheels 39a and 39b via a differential gear 38. As described above, the crankshaft 26 of the engine 22 is connected to the carrier of the planetary gear 30 via the damper 28.

The motor MG1 is configured as, for example, a synchronous generator motor, and the rotor is connected to the sun gear of the planetary gear 30 as described above. The motor MG2 is configured as, for example, a synchronous generator motor, and the rotor is connected to the drive shaft 36. Inverters 41 and 42 are used to drive motors MG1 and MG2, and are connected to battery 50 via power line 54. A smoothing capacitor 57 is attached to the power line 54. The motors MG1 and MG2 are rotationally driven by a plurality of switching elements (not shown) of the inverters 41 and 42 being switching-controlled by a motor electronic control unit (hereinafter referred to as “motor ECU”) 40.

Although not shown, the motor ECU 40 is configured as a microprocessor centered on a CPU, and in addition to the CPU, includes a ROM that stores a processing program, a RAM that temporarily stores data, an input/output port, and a communication port. Prepare Signals from various sensors necessary for driving and controlling the motors MG1 and MG2 are input to the motor ECU 40 via an input port. The signal input to the motor ECU 40 flows to, for example, rotational positions θm1 and θm2 from rotational position detection sensors 43 and 44 that detect rotational positions of rotors of the motors MG1 and MG2, and phases of the motors MG1 and MG2. The phase currents Iu1, Iv1, Iu2, Iv2 from the current sensors 45u, 45v, 46u, 46v for detecting the current can be mentioned. From the motor ECU 40, switching control signals and the like to the plurality of switching elements of the inverters 41 and 42 are output via the output port. The motor ECU 40 is connected to the HVECU 70 via a communication port. The motor ECU 40, based on the rotational positions θm1 and θm2 of the rotors of the motors MG1 and MG2 from the rotational position detection sensors 43 and 44, the electrical angles θe1 and θe2 of the motors MG1 and MG2, the angular velocities ωm1 and ωm2, the rotational speeds Nm1 and Nm2. Is being calculated.

The battery 50 is configured as, for example, a lithium ion secondary battery or a nickel hydrogen secondary battery, and is connected to the power line 54. The battery 50 is managed by a battery electronic control unit (hereinafter, referred to as “battery ECU”) 52.

Although not shown, the battery ECU 52 is configured as a microprocessor centered on a CPU, and in addition to the CPU, includes a ROM that stores a processing program, a RAM that temporarily stores data, an input/output port, and a communication port. Prepare Signals from various sensors necessary for managing the battery 50 are input to the battery ECU 52 via an input port. As the signal input to the battery ECU 52, for example, the voltage Vb of the battery 50 from the voltage sensor 51a attached between the terminals of the battery 50, or the voltage Vb of the battery 50 from the current sensor 51b attached to the output terminal of the battery 50, can be used. The current Ib (a positive value when discharged from the battery 50), the temperature Tb of the battery 50 from the temperature sensor 51c attached to the battery 50, and the like can be mentioned. The battery ECU 52 is connected to the HVECU 70 via a communication port. The battery ECU 52 calculates the charge ratio SOC based on the integrated value of the current Ib of the battery 50 from the current sensor 51b, and calculates the charge ratio SOC and the temperature Tb of the battery 50 from the temperature sensor 51c and the internal resistance of the battery 50. The input/output limits Win and Wout are calculated based on Rb. The charge ratio SOC is the ratio of the capacity of the electric power that can be discharged from the battery 50 to the total capacity of the battery 50, and the input/output limits Win and Wout are the maximum allowable electric power that may charge and discharge the battery 50. The internal resistance Rb of the battery 50 is estimated by an internal resistance estimation routine described later.

Although not shown, the HVECU 70 is configured as a microprocessor centered on a CPU, and includes, in addition to the CPU, a ROM that stores a processing program, a RAM that temporarily stores data, an input/output port, and a communication port. .. Signals from various sensors are input to the HVECU 70 via input ports. Examples of the signal input to the HVECU 70 include an ignition signal from the ignition switch 80 and a shift position SP from a shift position sensor 82 that detects the operation position of the shift lever 81. In addition, the accelerator opening Acc from the accelerator pedal position sensor 84 that detects the depression amount of the accelerator pedal 83, the brake pedal position BP from the brake pedal position sensor 86 that detects the depression amount of the brake pedal 85, and the vehicle speed sensor 88 from the vehicle speed sensor 88. The vehicle speed V can also be mentioned. The HVECU 70 is connected to the engine ECU 24, the motor ECU 40, and the battery ECU 52 via the communication port as described above.

In the "drive system" of the embodiment, the "drive device" mainly corresponds to the engine 22, the planetary gear 30, the motors MG1 and MG2, and the inverters 41 and 42, and the "control unit" includes the HVECU 70 and the engine. The ECU 24 and the motor ECUs 40 and 52 correspond.

The hybrid vehicle 20 of the embodiment thus configured is in a hybrid travel mode (HV travel mode) in which the engine 22 is driven and an electric travel mode (EV travel mode) in which the engine 22 is not driven. To run. Hereinafter, normal control in the HV traveling mode and the EV traveling mode will be described.

In the normal control in the HV traveling mode, the HVECU 70 sets the required torque Td* required for the drive shaft 36 based on the accelerator opening Acc and the vehicle speed V, and rotates the drive shaft 36 at the set required torque Td*. The required power Pd* required for the drive shaft 36 is calculated by multiplying by the number Nd (the rotation speed Nm2 of the motor MG2). Subsequently, the charge/discharge request power Pb* required by the battery 50 (a positive value when discharging from the battery 50) is set based on the charge ratio SOC of the battery 50, and the charge/discharge request of the battery 50 is obtained from the request power Pd*. The required power Pe* required for the engine 22 is set by subtracting the power Pb*. Then, the target rotation speed Ne* of the engine 22 is output so that the required power Pe* is output from the engine 22 and the required torque Td* is output to the drive shaft 36 within the input/output limits Win and Wout of the battery 50. And target torque Te* and torque commands Tm1* and Tm2* for the motors MG1 and MG2 are set. Then, the target rotation speed Ne* of the engine 22 and the target torque Te* are transmitted to the engine ECU 24, and the torque commands Tm1* and Tm2* of the motors MG1 and MG2 are transmitted to the motor ECU 40. When the engine ECU 24 receives the target rotation speed Ne* and the target torque Te* of the engine 22, the engine ECU 24 controls the operation of the engine 22 (intake air so that the engine 22 operates based on the target rotation speed Ne* and the target torque Te*). Quantity control, fuel injection control, ignition control, etc.). When the motor ECU 40 receives the torque commands Tm1*, Tm2* of the motors MG1, MG2, the motor ECU 40 performs drive control of the motors MG1, MG2 so that the motors MG1, MG2 are driven by the torque commands Tm1*, Tm2* (specifically. Switching control of the plurality of switching elements of the inverters 41 and 42 is performed.

In the normal control in the EV traveling mode, the HVECU 70 sets the required torque Td* based on the accelerator opening Acc and the vehicle speed V, sets the torque command Tm1* of the motor MG1 to the value 0, and inputs/outputs the battery 50. The torque command Tm2* of the motor MG2 is set such that the required torque Td* is output to the drive shaft 36 within the limits Win and Wout. Then, torque commands Tm1* and Tm2* for motors MG1 and MG2 are transmitted to motor ECU 40. The drive control of the motors MG1 and MG2 by the motor ECU 40 has been described above.

Next, the operation of the hybrid vehicle 20 of the embodiment thus configured, particularly the operation when estimating the internal resistance Rb of the battery 50 will be described. FIG. 2 is a flowchart showing an example of an internal resistance estimation routine executed by the battery ECU 52. This routine is repeatedly executed every predetermined time (for example, about several tens to several hundreds of msec).

When the internal resistance estimation routine is executed, the CPU (not shown) of the battery ECU 52 first inputs the current Ib, the voltage Vb, and the storage ratio SOC of the battery 50 (step S100). Here, as the current Ib of the battery 50, a value detected by the current sensor 51b (a positive value when the battery 50 is discharged) is input. As the voltage Vb of the battery 50, the value detected by the voltage sensor 51a is input. As the power storage ratio SOC, a value calculated by the battery ECU 52 in parallel with this routine is input.

When the data is input in this way, the input storage ratio SOC of the battery 50 is compared with the threshold value Sref (step S110). Here, as the threshold value Sref, for example, 35%, 40%, 45% or the like is used. FIG. 3 is an explanatory diagram showing an example of the relationship between the charge ratio SOC of the battery 50 and the open circuit voltage OCV. In the figure, the solid line is the charge curve, the broken line is the discharge curve, and the alternate long and short dash line is the intermediate curve.

As shown in FIG. 3, the inventors of the present invention have performed an analysis and the like, and in a region where the charge ratio SOC of the battery 50 is less than the threshold value Sref, when the charge of the battery 50 continues, the charge ratio SOC of the battery 50 and the open circuit voltage OCV. When the relationship of No. moves to the side where the charge ratio SOC is large along the charge curve (see the solid line in the figure) and the battery 50 continues to be discharged, this relationship becomes the charge ratio along the discharge curve (see the broken line in the figure). It was confirmed that this relationship transitions between the charge curve and the discharge curve when the battery 50 moves to the smaller SOC side and the charging and discharging of the battery 50 are switched. That is, in the region where the charge ratio SOC of the battery 50 is less than the threshold value Sref, the same charge ratio SOC for the same charge and discharge history of the battery 50 (whether charging continues, discharging continues, or switching between charging and discharging) is performed. It was confirmed that the open circuit voltage OCV was different (has hysteresis). Further, it was confirmed that in the region where the charge ratio SOC of the battery 50 is equal to or higher than the predetermined ratio Sref, the open circuit voltage OCV is substantially the same for the same charge ratio SOC regardless of the charge/discharge history of the battery 50. The relationship between the current Ib of the battery 50 and the voltage Vb is determined according to the relationship between the charge ratio SOC of the battery 50 and the open circuit voltage OCV.

The intermediate curve is defined as a curve between the charge curve and the discharge curve in order to estimate the open circuit voltage OCV of the battery 50 immediately after the ignition switch 80 is turned on based on the charge ratio SOC. In the embodiment, for the sake of simplicity, the intermediate curve is determined so that the average value of the open voltage OCVch of the charge curve and the open voltage OCVdi of the discharge curve becomes the open voltage OCVmi of the intermediate curve for each charge ratio SOC.

When the power storage ratio SOC of the battery 50 is equal to or higher than the threshold value Sref in step S110, an instruction to execute the normal control in the HV traveling mode or the EV traveling mode is transmitted to the HVECU 70 (step S120), and the current Ib and the voltage of the battery 50 are also transmitted. A set of Vb and the storage ratio SOC is stored in the RAM (not shown) as sample data (step S130). When the HVECU 70 receives this instruction, the above-mentioned normal control is performed by cooperative control among the HVECU 70, the engine ECU 24, and the motor ECU 40.

Then, the number of sample data stored in the RAM is compared with the predetermined number Nj (step S140). Here, the predetermined number Nj is the number of sample data required to accurately estimate the internal resistance Rb of the battery 50, and for example, 250, 300, 350 or the like is used. When the number of sampled data is less than the predetermined number Nj, it is determined that the number of sampled data required to accurately estimate the internal resistance Rb of the battery 50 is not complete, and this routine is ended.

When the number of sampled data is equal to or more than the predetermined number Nj in step S140, it is determined that the number of sampled data necessary for accurately estimating the internal resistance Rb of the battery 50 is complete, and the current Ib of the battery 50 is calculated using each sampled data. The variance amount ΔS of the variance Vi and the storage ratio SOC of is calculated (step S150). The variation amount ΔS of the power storage ratio SOC can be calculated as a difference between the maximum value and the minimum value of the power storage ratio SOC using each sample data, for example.

Then, the variance Vi of the current Ib of the battery 50 is compared with the threshold value Viref (step S160), and the variation amount ΔS of the storage ratio SOC of the battery 50 is compared with the threshold value ΔSref (step S170). Here, the threshold value Viref and the threshold value ΔSref are threshold values used to determine whether or not the current condition and the charge ratio condition for accurately estimating the internal resistance Rb of the battery 50 are satisfied, and the threshold value Viref. For example, 90A ² , 100A ² , 110A ² or the like is used, and the threshold value ΔSref is, for example, 4%, 5%, 6% or the like.

When the distribution Vi of the current Ib of the battery 50 is equal to or larger than the threshold value Viref in step S160 and the variation amount ΔS of the storage ratio SOC of the battery 50 is equal to or smaller than the threshold value ΔSref in step S170, the above-described current condition and storage ratio condition are satisfied. Then, the internal resistance Rb of the battery 50 is estimated using each sample data (step S180), all the sample data are reset (discarded) (step S190), and this routine is ended.

FIG. 4 is an explanatory diagram for explaining a method of estimating the internal resistance Rb of the battery 50. As shown in the figure, each sample data (a set of current Ib and voltage Vb) is plotted on a map in which the horizontal axis is current Ib and the vertical axis is voltage Vb, and the least squares method is used by using the plotted plot points. The approximate straight line is set by, and the inclination of the approximate straight line is estimated as the internal resistance Rb of the battery 50.

In a region where the charge ratio SOC of the battery 50 is equal to or higher than the predetermined ratio Sref, the open circuit voltage OCV is substantially the same for the same charge ratio SOC regardless of the charge/discharge history of the battery 50, and the relationship between the current Ib and the voltage Vb is shown. The variation is also small. Therefore, the internal resistance Rb of the battery 50 can be accurately estimated.

When the state of charge SOC of the battery 50 is less than the threshold value Sref in step S110, an instruction to execute the forced charge control is transmitted to the HVECU 70 so that the battery 50 is forcibly charged (step S200), and this routine ends. When the HVECU 70 receives this instruction, the HVECU 70, the engine ECU 24, and the motor ECU 40 cooperatively control the forced charging control. In the forced charge control, the HV traveling mode is selected, and a negative (on the charging side) and a large absolute value is set as the charge/discharge required power Pb* of the battery 50 regardless of the state of charge SOC of the battery 50. The same control as the normal control in the HV traveling mode is performed. By such control, the battery 50 is charged.

In this way, when the battery 50 continues to be charged, the storage ratio SOC of the battery 50 increases. Then, if it is determined in step S110 that the SOC of the battery 50 has reached the threshold value Sref or higher, the processing in step S120 and subsequent steps is executed. That is, when the charge ratio SOC of the battery 50 is less than the threshold value Sref, the forced charge control is executed, and the internal resistance Rb of the battery 50 is estimated after the charge ratio SOC of the battery 50 reaches the threshold value Sref or more. As a result, it is possible to suppress the estimation accuracy of the internal resistance Rb from being lowered as compared with the case where the internal resistance Rb of the battery 50 is estimated when the charge ratio SOC of the battery 50 is less than the threshold value Sref.

In the drive system mounted on the hybrid vehicle 20 of the embodiment described above, when the power storage ratio SOC of the battery 50 is less than the threshold Sref, the forced charge control is executed and the power storage ratio SOC of the battery 50 becomes the threshold Sref or more. From this, the internal resistance Rb of the battery 50 is estimated. This can prevent the estimation accuracy of the internal resistance Rb from decreasing.

In the drive system mounted on the hybrid vehicle 20 of the embodiment, the current condition (the condition that the dispersion Vi of the current Ib of the battery 50 is equal to or more than the threshold value Viref) and the charge ratio condition () are used as conditions for estimating the internal resistance Rb of the battery 50. The condition that the variation amount ΔS of the storage ratio SOC of the battery 50 is equal to or less than the threshold value ΔSref) is used. However, only one of them may be used, or none of them may be used.

Although the hybrid vehicle 20 of the embodiment includes the engine ECU 24, the motor ECU 40, the battery ECU 52, and the HVECU 70, at least two of them may be integrally configured.

In the embodiment, the form of the drive system mounted on the hybrid vehicle 20 is used, but the form of the drive system other than the car, for example, the form of the drive system mounted on stationary construction equipment or the like may be used.

Correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem will be described. In the embodiment, the engine 22, the planetary gear 30, the motors MG1 and MG2, and the inverters 41 and 42 correspond to "driving device", the battery 50 corresponds to "secondary battery", and the current sensor 51b corresponds to "current sensor". The voltage sensor 51a corresponds to a “voltage sensor”, and the HVECU 70, the engine ECU 24, the motor ECU 40, and the battery ECU 52 correspond to a “control unit”.

The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is the same as that of the embodiment described in the section of means for solving the problem. This is an example for specifically explaining the mode for carrying out the invention, and does not limit the elements of the invention described in the column of means for solving the problem. That is, the interpretation of the invention described in the column of means for solving the problem should be made based on the description in that column, and the embodiment is the invention of the invention described in the column of means for solving the problem. This is just a specific example.

Although the embodiments for carrying out the present invention have been described above with reference to the embodiments, the present invention is not limited to these embodiments, and various embodiments are possible within the scope not departing from the gist of the present invention. Of course, it can be implemented.

INDUSTRIAL APPLICABILITY The present invention can be used in the drive system manufacturing industry and the like.

20 hybrid vehicle, 22 engine, 23 crank position sensor, 24 engine ECU, 26 crank shaft, 28 damper, 30 planetary gear, 36 drive shaft, 38 differential gear, 39a, 39b drive wheel, 40 motor ECU, 41, 42 inverter, 43 , 44 rotational position detection sensor, 45u, 45v, 46u, 46v current sensor, 50 battery, 51a voltage sensor, 51b current sensor, 51c temperature sensor, 52 battery ECU, 54 power line, 57 capacitor, 70 HVECU, 80 ignition switch, 81 shift lever, 82 shift position sensor, 83 accelerator pedal, 84 accelerator pedal position sensor, 85 brake pedal, 86 brake pedal position sensor, 88 vehicle speed sensor.

Claims (1)

A drive,
A secondary battery that is charged and discharged according to the driving state of the driving device,
A current sensor for detecting the current of the secondary battery,
A voltage sensor for detecting the voltage of the secondary battery,
A control unit that controls the drive device and estimates the internal resistance of the secondary battery by using a plurality of sets of the current and the voltage,
A drive system comprising:
The control unit controls the driving device so that the secondary battery is charged when the storage ratio of the secondary battery is less than a predetermined ratio, and the internal unit after the storage ratio becomes equal to or higher than the predetermined ratio. To estimate resistance,
Drive system.

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