DYNAMIC TARGET CHARGE STATE FOR CAPACITY ESTIMATION OF HYBRID VEHICLES

Abstract

A vehicle includes a system that performs a procedure for calculating the capacity of the vehicle's battery. The system includes a processor configured to operate the vehicle to discharge the battery and reach a low target state of charge, to measure a low resting state of charge after allowing the battery to rest for an initial rest period once it reaches the low target state of charge, to operate the vehicle to charge the battery until it reaches a high target state of charge, to measure a high resting state of charge after allowing the battery to rest for a second rest period once it reaches the high target state of charge, and to calculate the battery's capacity from the low resting state of charge and the high resting state of charge.

Description

INTRODUCTION

[0001] The present disclosure relates to determining an aging condition of a battery used in a hybrid vehicle, and more particularly to a system and method for determining the charge capacity of the battery.

[0002] The battery is a critical component of a motor vehicle. In a hybrid vehicle, the battery serves to supply the vehicle with power in electric mode and to provide ignition for the internal combustion engine in combustion mode. Knowing the battery's aging state is an important factor in maintaining the vehicle's operational readiness. Since the battery can be either discharged or charged depending on the vehicle's operating mode, there is no direct method for knowing the battery's state of charge or aging. Accordingly, it is desirable to provide a method for determining the state of charge of a battery used in a hybrid vehicle. SUMMARY

[0003] In an exemplary embodiment, a method for calculating a capacity of a battery of a vehicle is disclosed. The battery is discharged to achieve a low target state of charge during operation of the vehicle. The battery is allowed to rest for a first rest period after the battery reaches the low target state of charge. A low rest state of charge is determined after the first rest period. The battery is charged to achieve a high target state of charge during operation of the vehicle. The battery is allowed to rest for a second rest period after the battery reaches the high target state of charge. A rest state of charge is determined after the second rest period. A capacity of the battery is calculated from the low rest state of charge and the high rest state of charge.

[0004] In addition to one or more of the features described herein, the method further comprises measuring an accumulated charge of the battery while charging the battery and calculating the capacity of the battery from the low resting state of charge, the high resting state of charge, and the accumulated charge.

[0005] In addition to one or more of the features described herein, the low desired state of charge is at a lower end of an operating range of the battery and the high desired state of charge is at an upper end of the operating range.

[0006] In addition to one or more of the features described herein, the method further comprises at least one of measuring a first voltage of the battery after the first rest period and determining the low rest state of charge from the first voltage and measuring a second voltage of the battery after the second rest period and determining the high rest state of charge from the second voltage.

[0007] In addition to one or more of the features described herein, determining at least one of the low resting state of charge and the high resting state of charge further comprises one of using a lookup table relating the state of charge to voltage and using a model equation relating the state of charge to voltage.

[0008] In addition to one or more of the features described herein, the method further comprises estimating the capacity of the battery based on at least one of a time since a previous update that is greater than a selected time criterion, a number of miles since the previous update that is greater than a selected mileage criterion, and a variance of the values ​​in the previous updates that is greater than a variance criterion.

[0009] In addition to one or more of the features described herein, the method further comprises at least one of performing a diagnostic test on the battery based on the estimated capacity, calculating a state of charge for the battery based on the estimated capacity, and sending a signal indicative of a state of deterioration of the battery.

[0010] In another exemplary embodiment, a system for calculating the capacity of a battery of a vehicle is disclosed. The system includes a processor configured to operate the vehicle to discharge the battery and reach a low desired state of charge, measure a low resting state of charge after allowing the battery to rest for a first rest period after the battery reaches the low desired state of charge, operate the vehicle to charge the battery to reach a high desired state of charge, measure a high resting state of charge after allowing the battery to rest for a second rest period after the battery reaches the high desired state of charge, and calculate a capacity of the battery from the low resting state of charge and the high resting state of charge.

[0011] In addition to one or more of the features described herein, the processor is further configured to measure an accumulated charge of the battery during charging of the battery and to calculate the capacity of the battery from the low resting state of charge, the high resting state of charge, and the accumulated charge.

[0012] In addition to one or more of the features described herein, the processor is configured to set the low desired state of charge at a lower end of an operating range of the battery and to set the high desired state of charge at an upper end of the operating range.

[0013] In addition to one or more of the features described herein, the processor is further configured to perform at least one of measuring a first voltage of the battery after the first rest period and determining the low rest state of charge from the first voltage and measuring a second voltage of the battery after the second rest period and determining the high rest state of charge from the second voltage.

[0014] In addition to one or more of the features described herein, the processor is further configured to determine at least one of the low resting state of charge and the high resting state of charge using one of a lookup table relating the state of charge to voltage and a model equation relating the state of charge to voltage.

[0015] In addition to one or more of the features described herein, the processor is further configured to estimate the capacity of the battery based on at least one of a time since a previous update that is greater than a selected time criterion, number of miles since the previous update that is greater than a selected mileage criterion, and a variance of the values ​​in the previous updates that is greater than a variance criterion.

[0016] In addition to one or more of the features described herein, the processor is further configured to perform at least one of performing a diagnostic test on the battery based on the estimated capacity, calculating a state of charge for the battery based on the estimated capacity, and sending a signal indicative of a state of deterioration of the battery to an operator.

[0017] In yet another exemplary embodiment, a vehicle is disclosed. The vehicle includes a battery and a processor. The processor is configured to operate the vehicle to discharge the battery and reach a low desired state of charge, measure a low resting state of charge after allowing the battery to rest for a first rest period after the battery reaches the low desired state of charge, operate the vehicle to charge the battery to reach a high desired state of charge, measure a high resting state of charge after allowing the battery to rest for a second rest period after the battery reaches the high desired state of charge, and calculate a capacity of the battery from the low resting state of charge and the high resting state of charge.

[0018] In addition to one or more of the features described herein, the processor is further configured to measure an accumulated charge of the battery during charging of the battery and to calculate the capacity of the battery from the low resting state of charge, the high resting state of charge, and the accumulated charge.

[0019] In addition to one or more of the features described herein, the processor is configured to set the low desired state of charge at a lower end of an operating range of the battery and to set the high desired state of charge at an upper end of the operating range.

[0020] In addition to one or more of the features described herein, the processor is further configured to perform at least one of measuring a first voltage of the battery after the first rest period and determining the low rest state of charge from the first voltage and measuring a second voltage of the battery after the second rest period and determining the high rest state of charge from the second voltage.

[0021] In addition to one or more of the features described herein, the processor is further configured to determine at least one of the low resting state of charge and the high resting state of charge using one of a lookup table relating the state of charge to voltage and a model equation relating the state of charge to voltage.

[0022] In addition to one or more of the features described herein, the processor is further configured to estimate the capacity of the battery based on at least one of a time since a previous update that is greater than a selected time criterion, number of miles since the previous update that is greater than a selected mileage criterion, and a variance of the values ​​in the previous updates that is greater than a variance criterion.

[0023] The above features and advantages, as well as other features and advantages of the disclosure, will be readily apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further features, advantages and details are listed only as examples in the following detailed description, which refers to the drawings, where: Fig. 1 illustrates an embodiment of a vehicle, in an exemplary embodiment; Fig. 2 is a flowchart illustrating a method for determining a charge capacity for the vehicle's battery system; and Fig. 3 illustrates a detailed flow diagram of a method for estimating the capacity of the battery system, in one embodiment. DETAILED DESCRIPTION

[0025] The following description is merely exemplary and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference characters designate like or corresponding parts and features.

[0026] According to an illustrative embodiment, Fig. 1 illustrates an embodiment of a motor vehicle 10 including a vehicle body 12 that at least partially defines a passenger compartment 14. The vehicle body 12 also supports various subsystems of the vehicle, including a propulsion system 16 and other subsystems for supporting functions of the propulsion system 16 and other vehicle components, such as a braking subsystem, a suspension system, a steering subsystem, a fuel injection subsystem, an exhaust subsystem, etc.

[0027] The vehicle 10 is a hybrid vehicle that includes an internal combustion engine assembly 18 and at least one electric motor assembly. The drive system 16 includes, for example, a first electric motor 20 and a second electric motor 21. The first electric motor 20 and the second electric motor 21 may be configured to drive wheels on opposite sides of the vehicle 10. Any number of motors may be positioned at different locations.

[0028] The vehicle 10 includes a battery system 22 that may be electrically connected to the first electric motor 20 and the second electric motor 21 and / or other components, such as the vehicle's electronics. The battery system 22 may be configured as a rechargeable energy storage system (RESS).

[0029] In one embodiment, the battery system 22 includes a battery assembly, such as the high-voltage battery pack 24, having a plurality of battery modules 26. Each of the battery modules 26 includes a number of individual cells (not shown). The battery system 22 may also include a monitoring unit 28 (e.g., RESS controller) configured to receive measurements from sensors 30. Each sensor 30 may be an assembly or system including one or more sensors for measuring various battery and environmental parameters, such as temperature, current, and voltages. The monitoring unit 28 includes components such as a processor, memory, an interface, a bus, and / or other suitable components.

[0030] The battery system 22 is electrically connected to a direct current (DC)-to-DC converter module 32 and an inverter module 34. The inverter module 34 (e.g., a traction power inverter or TPIM) converts direct current (DC) from the battery assembly to three-phase alternating current (AC) to drive the motors. In one embodiment, the inverter module 34 includes a first inverter 36 connected to the first electric motor 20 and a second inverter 38 connected to the second electric motor 21.

[0031] The battery system 22 may also be connected to other vehicle components or systems. For example, the battery system 22 is connected to an auxiliary power module (APM) 40, which controls the power output to components such as a heating system. The APM 40 may be used to provide power from the battery system 22 for heating the passenger compartment 14.

[0032] The vehicle 10 may include a charging system that may be used to charge the high-voltage battery 24 and / or to provide power from the high-voltage battery 24 to charge another energy storage system (e.g., vehicle-to-vehicle charging). The charging system includes an on-board charging module (OBCM) 42 electrically connected to a charging port 44.

[0033] In one embodiment, the vehicle 10 includes a hybrid operating system 55 configured to control the operation of the vehicle 10, including controlling the selection and operation of the internal combustion engine assembly 18 and the at least one electric motor assembly. The hybrid operating system 55 is in communication with and receives data from the monitoring unit 28. The hybrid operating system 55 includes a processing device or processor, which may be any suitable processor, such as the monitoring unit (e.g., RESS controller) 28, the OBCM 42, or a dedicated controller 46. The hybrid operating system 55 or processor may be used to perform various operations disclosed herein for determining or estimating the charge capacity of a battery of the vehicle.

[0034] The vehicle 10 also includes a computer system 48 that includes one or more processing devices 50 and a user interface 52. The various processing devices and units may communicate with each other via a communication device or system, such as a Controller Area Network (CAN) or Transmission Control Protocol (TCP) bus.

[0035] Fig. 2 depicts a flowchart 200 illustrating a method for determining a charge capacity for the battery system 22 of the vehicle 10. In box 202, the battery is discharged until the battery state of charge reaches a low desired state of charge (SOC TL). The SOCTL is selected such that the SOC is at a lower end of an operating range of the battery system 22. The battery system 22 is discharged by operation of the vehicle 10, such as by driving the vehicle in electric mode. In field 204, a low resting low state of charge (SOC RL ) is recorded after the battery system 22 is allowed to rest for an initial rest period. In field 206, the battery is charged until the SOC reaches a high target state of charge (SOC TH ). The SOC TH is selected to be at a high end of an operating range of the battery system 22. The battery is charged by operation of the vehicle 10, such as by driving the vehicle in combustion mode, in which the engine assembly 18 charges the battery. During the charging process, an accumulated charge on the battery is measured. In field 208, a high resting state of charge (SOCRH ) after the battery system 22 is allowed to rest for a second rest period. In field 210, the battery capacity is determined from the low rest SOC value (SOC RL ) and the high resting SOC value (SOC RH ) and the accumulated charge measured when charging the battery.

[0036] Fig.3 illustrates a detailed flowchart 300 of a method for estimating the capacity of the battery system 22, in one embodiment. The method begins in block 302. In block 304, the processor determines whether an update to the estimated capacity of the battery is necessary based on one or more criteria. For example, the processor may start a new estimation process if the time since the last update is greater than a selected time criterion. In another example, the processor may start a new estimation process if the number of miles since the last update is greater than a selected mileage criterion. In another example, the processor may start a new estimation process if a variance in charge capacities calculated from previous updates is greater than a selected variance criterion.If no update is necessary in field 304, the process continues with field 338, where it ends. If an update is necessary, the process continues with field 306.

[0037] In box 306, the vehicle's drive mode is determined. If the drive mode is not suitable for performing the capacity update (i.e., a sport or performance mode), the method continues to box 338, where the method ends. If the drive mode is suitable for performing the upper power range (i.e., normal driving), the method continues to box 308.

[0038] In field 308, the processor sets a low target state of charge (SOC TL ). The SOC TL is set at the lower end of a usable SOC range for the battery. The SOC TL can be, for example, 30% of the battery charge capacity.

[0039] In field 310, the battery is discharged with the aim of reducing the SOC TLThe battery is discharged while driving, typically using the first electric motor 20 or a second electric motor 21. In field 312, the actual SOC is compared with the SOC TL compared. If the SOC TL has not been reached, the method continues with field 314. In field 314, the vehicle's driving mode is checked. If the driving mode is not suitable for performing the capacity update, the method continues with field 338, where the method ends. Otherwise, if the driving mode is suitable, the method continues with field 310. Upon returning to field 312, the method continues if the SOC TL is reached, continue with field 316.

[0040] In field 316, the battery is charged to the low target SOC (SOC TL) until a key-off event is received to turn off the vehicle. In field 318, the battery is allowed to rest for an initial rest period, after which a low resting SOC value (SOC LR ) of the battery is determined. In various embodiments, the first rest period can be between 1-3 hours. After the first rest period, a first voltage of the battery is measured, and the SOC LR is determined using the first voltage. In one embodiment, the SOC RL using the measured voltage and a lookup table that relates the voltage to the SOC. Alternatively, other methods for calculating the SOC can be used. RL from the first voltage, including equations, battery models, etc.

[0041] If no low battery resting SOC has been determined in field 318, the method continues to field 320. If the vehicle is not in the appropriate mode (i.e., sleep mode), the method continues to field 338, where the method ends. Otherwise, the method continues to field 316. Upon returning to field 318 once the low battery resting SOC has been determined, the method continues to field 322.

[0042] In field 322, a high target SOC (SOC TH ) set. The SOC TH can be adjusted during key-up (i.e., when the vehicle is switched on). The SOC TH is set at the upper end of the battery's usable range. For example, the SOC TH for example, 70% of the battery capacity.

[0043] In field 324, the battery is charged with the aim of reaching the high target SOC (SOC TH). The battery is charged while driving, usually using the internal combustion engine assembly 18. While the battery is being charged, the processor calculates the accumulated charge Q Akkum . In one embodiment, the accumulated charge of the pack is calculated using an iterative process as shown in equation (1). QAccum(k)=QAccum(k−1)+(l*Δt) / 3600 where Q Akkum where I is the accumulated battery charge (in ampere-hours), I is the current (in amperes) through the battery or battery pack, and t is the time (in seconds). The accumulated charge at a time step k is calculated based on the accumulated charge at a previous time step k-1.

[0044] In field 326 a decision is made whether the SOC TH has been reached. If the SOC THhas not been reached, the method continues with field 328. In field 328, the driving mode of the vehicle is checked. If the driving mode is not suitable for performing the capacity update (i.e., if it is not a normal driving mode), the method continues with field 338, where the method ends. Otherwise, if the driving mode is suitable, the method continues with field 324. Upon returning to field 326, the method continues if the SOC TH is reached, continue with field 330.

[0045] In field 330, the processor maintains the battery SOC at or near the high desired SOC until a key off command is received that shuts down the vehicle.

[0046] In field 332, the battery system 22 is allowed to rest for a second rest period and a high rest SOC value (SOC RH) of the battery is determined. In various embodiments, the second rest period can be between 1-3 hours. After the first rest period, a second voltage of the battery is measured, and the SOC RH is determined based on the second voltage. In one embodiment, the SOC RH based on the measured voltage and a lookup table that relates the voltage to the SOC. Alternatively, other methods for calculating the SOC can be used. RH from the second voltage, including equations, battery models, etc.

[0047] If a low battery resting SOC has not been determined in field 332, the method continues to field 334. If the vehicle is not in the appropriate mode (i.e., sleep mode) at field 334, the method continues to field 338, where the method ends. Otherwise, the method continues to field 330. Upon returning to field 332, once the high battery resting SOC is determined, the method continues to field 336.

[0048] An estimated capacity of the battery is calculated in field 336. The estimated capacity can be calculated based on the low resting state of charge (SOC RL ), the high resting state of charge (SOC RH ) and the accumulated charge Q Akkum be calculated as shown in equation (2): Capacity estimate=QAccum / (SOCRH−SOCRL)

[0049] After estimating the battery capacity, the method continues to box 338, where the method ends.

[0050] In various embodiments, the processor may send a signal indicating the aging state or state of charge of the battery to a display that can be viewed by a driver or operator once the calculation is complete. In an alternative embodiment, the processor may perform a diagnostic test on the battery or vehicle based on the calculated capacity. In an alternative embodiment, the processor may calculate a state of charge of the battery based on the estimated capacity. In an alternative embodiment, the processor may provide the driver with a signal indicating the need for repair or maintenance.

[0051] The terms "a / an / an" do not imply a quantity limitation, but denote the presence of at least one of the mentioned items. The term "or" means "and / or" unless the context clearly indicates otherwise. References to "an aspect" throughout this specification mean that a particular element (e.g., a feature, structure, step, or property) described in connection with the aspect is included in at least one of the aspects described herein and may or may not be present in other aspects. In addition, it is understood that the described elements in the various aspects may be combined in any suitable manner.

[0052] When an element such as a layer, film, region, or substrate is described as lying "on" another element, it may lie directly on top of the other element, or there may be intervening elements. In contrast, when an element is described as lying "directly on" another element, there are no intervening elements.

[0053] Unless otherwise stated herein, all examination standards are the most recent standard in effect on the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the examination standard appears.

[0054] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0055] Although the above disclosure has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and equivalent elements may be substituted without departing from the scope thereof. In addition, many changes may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Therefore, the present disclosure is not intended to be limited to the particular embodiments disclosed, but is intended to include all embodiments falling within its scope. legend

[0056] In the drawings, N stands for No and Y stands for Yes.

Claims

[1] A method for calculating a capacity of a battery of a vehicle, comprising: Discharging the battery to achieve a low target state of charge during vehicle operation; Allowing the battery to rest for an initial rest period after the battery reaches the low target state of charge; Determining a low resting state of charge after the first rest period; Charging the battery to achieve a high target state of charge during vehicle operation; Allowing the battery to rest for a second rest period after the battery reaches the high target state of charge; Determining a high resting state of charge after the second rest period; and Calculate a battery capacity from the low resting state of charge and the high resting state of charge. [2] The method of claim 1, further comprising measuring an accumulated charge of the battery while charging the battery and calculating the capacity of the battery from the low resting state of charge, the high resting state of charge and the accumulated charge. [3] The method of claim 1, further comprising at least one of: (i) measuring a first voltage of the battery after the first rest period and determining the low rest state of charge from the first voltage; and (ii) measuring a second voltage of the battery after the second rest period and determining the high rest state of charge from the second voltage. [4] The method of claim 1, further comprising estimating the capacity of the battery based on at least one of: (i) a time since a previous update that is greater than a selected time criterion; (ii) a number of miles since the previous update that is greater than a selected mileage criterion; and (iii) a variance of the values ​​in the previous updates that is greater than a variance criterion. [5] The method of claim 1, further comprising at least one of: (i) performing a diagnostic test on the battery based on the calculated capacity; (ii) calculating a state of charge for the battery based on the calculated capacity; and (iii) sending a signal indicative of an aging condition of the battery. [6] System for calculating the capacity of a battery of a vehicle, comprising: a processor configured to: operate the vehicle to discharge the battery and achieve a low target state of charge; measure a low resting state of charge after allowing the battery to rest for an initial rest period after the battery reaches the target low state of charge; to operate the vehicle to charge the battery until a high target state of charge is reached; measure a high resting state of charge after allowing the battery to rest for a second rest period after the battery reaches the high target state of charge; and to calculate the battery capacity from the low resting state of charge and the high resting state of charge. [7] The system of claim 6, wherein the processor is further configured to measure an accumulated charge of the battery during charging of the battery and calculate the capacity of the battery from the low resting state of charge, the high resting state of charge, and the accumulated charge. [8] The system of claim 6, wherein the processor is further configured to perform at least one of: (i) measuring a first voltage of the battery after the first rest period and determining the low rest state of charge from the first voltage; and (ii) measuring a second voltage of the battery after the second rest period and determining the high rest state of charge from the second voltage. [9] The system of claim 6, wherein the processor is further configured to estimate the capacity of the battery based on at least one of: (i) a time since a previous update that is greater than a selected time criterion; (ii) a number of miles since the previous update that is greater than a selected mileage criterion; and (iii) a variance of the values ​​in the previous updates that is greater than a variance criterion. [10] The system of claim 6, wherein the processor is further configured to perform at least one of: (i) performing a diagnostic test on the battery based on the calculated capacity; (ii) calculating a state of charge for the battery based on the calculated capacity; and (iii) sending a signal indicating an aging condition of the battery to an operator.

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