Battery overcurrent diagnostic system

Abstract

Diagnostic system for a vehicle (12), comprising: a traction battery (26) having a plurality of cells; and a controller configured to detect an overcurrent condition in response to that the battery current is greater than a value of an upper limit of a current sensor (44) and a difference between a measured battery voltage and an estimated battery voltage based on the value is greater than a threshold.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to systems and methods for diagnosing and managing an overcurrent condition in a vehicle battery. BACKGROUND

[0002] The term "electric vehicle" can be used to describe vehicles that have at least one electric motor for vehicle propulsion, such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). A BEV contains at least one electric motor, where the energy source for the motor is a battery rechargeable from an external electricity grid. An HEV contains an internal combustion engine and one or more electric motors, where the energy source for the internal combustion engine is fuel and the energy source for the motor is a battery. In an HEV, the internal combustion engine is the primary energy source for vehicle propulsion, with the battery providing additional energy for vehicle propulsion (the battery stores fuel energy and recovers kinetic energy in electrical form).A PHEV is like an HEV, except that the PHEV has a larger-capacity battery that can be recharged from the external electricity grid. In a PHEV, the battery is the primary energy source for propulsion until the battery depletes to a low energy level, at which point the PHEV operates like an HEV for propulsion.

[0003] From US 2012 / 0 212 871 A1, an overcurrent detection of a battery with measurement of the terminal voltage is known, whereby a temporal variation of the terminal voltage is evaluated. SUMMARY

[0004] A diagnostic system for a vehicle includes a traction battery having a plurality of cells and a controller configured to indicate an overcurrent condition in response to a battery current being greater than an upper limit value of a current sensor and a difference between a measured battery voltage and an estimated battery voltage based on the value being greater than a threshold value.

[0005] A method for a traction battery of a vehicle includes indicating, by a controller, an overcurrent condition in response to a battery current being greater than an upper limit value of a current sensor and a difference between a measured battery voltage and an estimated battery voltage based on the value being greater than a threshold value.

[0006] A traction battery for a vehicle includes a plurality of cells and a pair of sensors, each configured to measure a different operating parameter of the cells and transmit the measured parameter to a battery controller, wherein the controller is configured to indicate a diagnostic condition in response to at least one of the measured parameters being at least equal to an upper limit value of the corresponding sensor and a difference between another measured parameter and an estimate of the other measured parameter based on the value being greater than a threshold value. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a block diagram of a plug-in hybrid electric vehicle (PHEV) illustrating typical powertrain and energy storage components; Fig. 2 is a block diagram illustrating a traction battery assembly including battery cells and battery cell monitoring and control systems; Fig. 3 is a schematic diagram illustrating a circuit model of a battery cell; Fig. 4 is a graph illustrating a relationship between an open circuit voltage and a battery cell state of charge; and Fig. Figure 5 is a flowchart illustrating an algorithm for diagnosing and managing an overcurrent condition. DETAILED DESCRIPTION

[0007] Embodiments of the present disclosure are described herein. It should be understood, however, that the disclosed embodiments are merely examples, and that other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to variously employ the present invention.It will be apparent to one of ordinary skill in the art that various features illustrated and described with reference to one of the figures may be combined with features illustrated in one or more other figures to produce embodiments not explicitly illustrated or described. The combinations of illustrated features provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of this disclosure may be desired for particular applications or implementations.

[0008] Fig. 1 illustrates a plug-in hybrid vehicle (PHEV) power system 10. A PHEV 12, hereinafter vehicle 12, may include a hybrid transmission 14 mechanically connected to an internal combustion engine 16 and a driveshaft 18 that drives the wheels 20. The hybrid transmission 14 may also be mechanically connected to one or more electric machines 22 capable of operating as a motor or generator. The electric machines 22 may be electrically connected to an inverter system controller (ISC) 24 that provides bidirectional power transfer between the electric machines 22 and at least one traction battery 26.

[0009] The traction battery 26 typically provides a high-voltage (HV) direct current (DC) output. In a motoring mode, the ISC 24 may convert the DC output provided by the traction battery 26 to a three-phase alternating current (AC), as may be required for proper functionality of the electric machines 22. In a regenerative mode, the ISC 24 may convert the three-phase AC output from the electric machines 22, which act as generators, to the DC required by the traction battery 26. In addition to providing power for propulsion, the traction battery 26 may provide power to high-voltage loads 28, such as compressors and electric heaters, and low-voltage loads 30, such as electrical accessories, a 12V auxiliary battery, and so on.

[0010] The vehicle 12 may be configured to recharge the traction battery 26 via a connection to an electrical grid. For example, the vehicle 12 may cooperate with electric vehicle supply equipment (EVSE) 32 of a charging station to coordinate the transfer of charge from the electrical grid to the traction battery 26. In one example, the EVSE 32 may include a charging connector for plugging into a charging port 34 of the vehicle 12, such as via connector pins that mate with corresponding recesses of the charging port 34. The charging port 34 may be electrically connected to an on-vehicle power conversion controller or charging device 36. The charging device 36 may condition the power supplied by the EVSE 32 to provide the appropriate voltage and current levels to the traction battery 26.The charging device 36 can be connected to the EVSE 32 to coordinate the delivery of power to the vehicle 12.

[0011] The vehicle 12 may be configured to receive single- or three-phase AC power from the EVSE 32. The vehicle 12 may further be capable of receiving various levels of AC voltage, including, but not limited to, Level 1 120 volt (V) AC charging, Level 2 240 V AC charging, and so forth. In one example, both the charging port 34 and the EVSE 32 may be configured to meet industry standards related to charging electrified vehicles, such as Society of Automotive Engineers (SAE) J1772, J1773, J2954, International Organization for Standardization (ISO) 15118-1, 15118-2, 15118-3, the German DIN specification 70121, and so forth.

[0012] The traction battery 26 may include a battery controller 42 configured to operate multiple plugs and switches of a bussed electrical center (BEC) 40 to enable the supply and removal of electrical energy to and from the traction battery 26. The battery controller 42 may be configured to determine one or more operating parameters associated with the traction battery 26 based on one or more measured and / or estimated characteristics of the traction battery 26. The battery controller 42 may be electrically connected and in communication with one or more other vehicle controllers.

[0013] In one example, the battery controller 42 is in communication with a telematics controller 43 of the vehicle 12. The telematics controller 43 may be configured to communicate with one or more off-board data storage and processing systems 45, such as via a wireless transceiver and / or a vehicle modem, using, for example, a wide area network 47. The battery controller 42 may be configured to transmit a signal indicative of a request to process one or more operating parameters associated with one or more vehicle components to the off-board data system 45, such as via the telematics controller 43.

[0014] The battery controller 42 may further be electrically connected to vehicle controls, such as a powertrain controller configured to control the control of engine operating components (e.g., idle control components, fuel delivery components, emissions control components, etc.) and monitor engine operating components (e.g., the status of engine diagnostic codes); a body controller configured to control various power control functions, such as exterior lighting, interior lighting, keyless entry, remote start, and access point status verification (e.g.,closure status of the hood, doors, and / or trunk of the vehicle 12); a radio transceiver configured to communicate with remote keyless entry systems or other local devices of the vehicle 12; and a climate control management controller configured to provide control and monitoring of heating and cooling system components (e.g., compressor clutch and blower control, temperature sensor information, etc.).

[0015] Although Fig. 1 depicts a plug-in hybrid electric vehicle, the description herein is equally applicable to a pure electric vehicle. In a pure electric vehicle, e.g., a battery electric vehicle (BEV), the hybrid transmission 14 may be a transmission connected to an electric machine 22, and the internal combustion engine 16 may not be present. The various components discussed may have one or more associated controllers to control and monitor the operation of the components. The controllers may communicate via a serial bus (e.g., Controller Area Network (CAN)) or via discrete conductors.

[0016] With reference to Fig. 2, an exemplary traction battery 26 for the vehicle 12 is shown. The traction battery 26 may include a plurality of battery cells 38, e.g., electrochemical cells, electrically connected to the BEC 40. The plurality of connectors and switches of the BEC 40 enable the supply and removal of electrical energy to and from the battery cells 38. In one example, the BEC 40 includes a positive main contactor electrically connected to a positive terminal of the battery cells 38 and a negative main contactor electrically connected to a negative terminal of the battery cells 38. Closing the positive and negative main contactors may enable the flow of electrical energy to and from the battery cells 38. Although the traction battery 26 is described herein as including electrochemical cells, other types of energy storage device implementations, such as capacitors, are also contemplated.

[0017] A battery controller 42 is electrically connected to the BEC 40 and controls the flow of energy to and from the battery cells 38 via the BEC 40. For example, the battery controller 42 may command the BEC 40 to open or close one or more switches in response to one or more operating parameters of the traction battery 26 and / or the battery cells 38 reaching a predetermined threshold. In another example, the battery controller 42 may be electrically connected to and in communication with one or more other vehicle controllers, such as a powertrain controller, a body controller, a climate control management controller, and so on, and command the BEC 40 to open or close one or more switches in response to a predetermined signal from the other vehicle controllers.

[0018] The battery controller 42 may monitor and control the performance of the traction battery 26. The battery controller 42 may monitor several traction battery charging characteristics, such as the traction battery current measured by a current sensor 44, the traction battery voltage measured by a voltage sensor 46, and the traction battery temperature measured by a temperature sensor 48. The performance of the current sensor 44 may be essential in certain arrangements to construct a reliable battery monitoring system. As described in more detail below, the accuracy of the current sensor 44 may be useful for estimating the battery capacity C and the battery state of charge (SOC), which is the actual capacity of the traction battery 26 expressed as a percentage of the battery capacity C when the traction battery 26 is fully charged.

[0019] In addition to the traction battery characteristics, the battery controller 42 may measure and monitor battery cell charge characteristics, such as, but not limited to, the terminal voltage and temperature of the one or more battery cells 38. In one example, the battery controller 42 may be configured to receive a signal from cell sensors 50 indicative of operating parameters of the one or more battery cells 38. The operating parameters may include, but are not limited to, the battery cell terminal voltage, temperature, age, number of charge / discharge cycles, and so forth. The battery controller 42 may include non-volatile memory so that battery charge and / or battery cell charge data may be retained when the battery controller 42 is turned off. In one example, the retained data may be available after the next ignition cycle.

[0020] Typically, the cell sensors 50 will measure the terminal voltage of the battery cells 38. The cell sensors 50 may be configured to transmit a signal to the battery controller 42 indicative of the measured terminal voltage of the battery cells 38. In one example, the cell sensors 50 may not be configured to directly measure the current of the battery cells 38, but the configuration and / or arrangement of the one or more battery cells 38 of the traction battery 26, e.g., the series arrangement, may define the current through the one or more battery cells 38 as the traction battery current measured by the current sensor 44.

[0021] Current sensor 44 may be configured to measure the charging and / or discharging current of traction battery 26. Current sensor 44 may be configured to measure the current directly, i.e., to measure a voltage drop associated with the current flowing through a passive electrical component, such as a resistor, or indirectly, i.e., to measure a magnetic field surrounding a conductor through which the current flows. In one example, current sensor 44 may be a closed-loop current sensor that uses feedback control to provide an output proportional to a measured current. In another example, current sensor 44 may be an open-loop current sensor, such as a Hall sensor mounted in an air gap of a magnetic core, which provides an output without relying on feedback control.

[0022] The current sensor 44 may be configured to measure the battery current between a predetermined lower operating point (or lower limit) I MIN and a predetermined upper operating point (or upper limit) I MAX For example, the battery current I MIN be negative and represent the charging current of the traction battery 26, while the battery current I MAX may be positive and may represent the discharge current of the traction battery 26. In one example, the current sensor 44 may provide an output proportional to I MAX in response to detecting the battery current equal to or greater than its upper operating point I MAXAn internal or external short circuit and other events may cause the traction battery 26 and / or battery components to operate outside of one or more predetermined operating limits. For example, an overcurrent condition may prevent the effective and efficient operation of the traction battery 26. It may be desirable to identify the presence of an overcurrent condition as early as possible.

[0023] The battery controller 42 may be configured to control the battery SOC SOC est using the Coulomb counting method, i.e., by integrating the measured battery current over time. In one example, in response to receiving a signal from the current sensor 44 indicating that the measured battery current of the traction battery 26 or the one or more battery cells 38 is equal to I MAX is, the battery controller 42 may be configured to control the battery SOC SOCest based on the Coulomb counting method, as expressed in equation (1): SOCest=SOC0−∫IMAXdtC where SOC0 is an initial battery SOC (either a known or estimated amount) and C is the battery capacity.

[0024] The battery controller 42 may be configured to, in response to receiving a signal from the current sensor 44 indicating that the measured battery current of the one or more battery cells 38 is equal to I MAX is to control the battery cell SOC SoC cell_est based on the Coulomb counting method, as shown in equation (2): SOCcell_est=SOC0_cell−∫IMAXdtCcell where SOC 0_cell is an initial battery cell SOC (either known or estimated quantity) and C cell , the capacity of the one or more battery cells 38 when fully charged.

[0025] With reference to Fig. 3, a circuit model 52 of at least one of the battery cells 38 is shown. In one example, the circuit model 52 may include an ideal voltage source 53 having a voltage V OC 54 and has an associated impedance. The impedance may include one or more resistors (generally indicated as a resistor 56). The voltage V OC 54 may, for example, represent an open circuit voltage of at least one of the battery cells 38, such as the voltage of the battery cell 38 under equilibrium conditions, ie, when no current flows into or out of the traction battery 26 and / or the battery cells 38. While the circuit model 52 with respect to Fig. 3 is directed to one battery cell, the application of the model to any combination of battery cells 38 is also provided. Values ​​of the parameters associated with the circuit model 52 can thus represent the values ​​of two battery cells 38, three battery cells 38, and so on. For example, in various configurations of the model, the open circuit voltage V OC 54 thus represent the open circuit voltage of one, two or any other number of the plurality of battery cells 38.

[0026] The resistor 56 may represent an internal resistance R of the battery cell 38 and / or the traction battery 26, including the resistance of a battery cable and other components associated with the traction battery 26. In an example where the circuit model 52 is applied to more than one battery cell, e.g., two cells, three cells, and so on, the resistor 56 may represent the internal resistance R of that combination of battery cells 38. The voltage V1 58 may represent a voltage drop across the resistor 56 as a result of the current i 60 flowing through the resistor 56. The terminal voltage V t 62 can represent the voltage across the positive and negative terminals of the battery cell 38. The terminal voltage V t 62 may differ from the open circuit voltage V OC54 as a result of the internal resistance R associated with the battery cell 38 and / or the one or more components of the traction battery 26.

[0027] Values ​​of the internal resistance R and other parameters of the traction battery 26 and / or the battery cells 38 may depend on the battery chemistry. The parameters may further vary based on the operating conditions of the traction battery 26. The values ​​of the parameters may also vary as a function of battery temperature. For example, the internal resistance R may decrease with increasing temperature, and so on. The parameter values ​​may also depend on the SOC of the traction battery 26.

[0028] Values ​​of the parameters of the traction battery 26 may also change over the lifetime of the traction battery 26. In one example, the internal resistance R may increase over the lifetime of the traction battery 26. The increase in the internal resistance R may further vary as a function of temperature and / or SOC during the lifetime of the traction battery 26.For example, operating the traction battery 26 at higher temperatures and / or at a higher SOC may result in a greater increase in the internal resistance R of the traction battery 26 over a predetermined period of time, such that the internal resistance R of the traction battery 26 operating at 80°C for a predetermined period of time may increase more than the internal resistance R of the traction battery 26 operating at 50°C for a similar period of time, and / or the internal resistance R of the traction battery 26 operating at 90% of the SOC may increase more than the internal resistance R of the traction battery 26 operating at the same temperature and 50% of the SOC. These relationships may further depend on the battery chemistry.

[0029] The battery controller 42 may be configured to determine the internal resistance R and other operating parameters associated with the traction battery 26 based on one or more measured and / or estimated characteristics of the traction battery 26. In one example, the battery controller 42 may be configured to determine the internal resistance R of the traction battery 26 based on measured and estimated characteristics, such as, but not limited to, the battery SOC, battery temperature, battery age, and so on. In another example, the battery controller 42 may be configured to determine the internal resistance of a portion of the traction battery 26, e.g., one or more battery cells 38, modules, and so on, based on one or more measured and / or estimated characteristics associated with the portion.

[0030] The battery controller 42 may be configured to transmit a signal to the off-vehicle data system 45, such as via the telematics controller 43, indicating a request to determine the internal resistance R of the traction battery 26 (or a portion of the traction battery 26) based on one or more measured and / or estimated characteristics associated with the traction battery 26 or the portion of the traction battery 26. The battery controller 42 may be configured to receive the internal resistance of the traction battery 26 and / or the internal resistance of a portion of the traction battery 26, e.g., the battery cell 38, determined based on the one or more measured and / or estimated characteristics.

[0031] The circuit model 52 can be expressed using equation (3): Vt=VOC−iR

[0032] The battery controller 42 may be configured to receive a signal indicative of the terminal voltage V t 62 of the battery cell 38, such as via a signal generated by the cell sensor 50. The open circuit voltage V OC 54 can be a function of the battery cell SOC, ie, V OC = f(SOC), so that the open circuit voltage V OC 54 may vary as a function of charging and discharging of the battery cell 38.

[0033] The battery controller 42 may be further configured to receive a signal indicative of the terminal voltage V t of the traction battery 26, such as via a signal generated by the voltage sensor 46. The battery open circuit voltage V OC can be a function of the battery SOC, ie, V OC = f(SOC), so that the battery open circuit voltage V OC may vary as a function of charging and discharging of the traction battery 26.

[0034] In Fig. 4 shows a curve 64 which shows an exemplary relationship between the open circuit voltage V OC 54 and the SOC of at least one of the battery cells 38 (or the cells V OC -SOC curve). The relationship between the SOC and the open circuit voltage V OC 54 may be based on one or more properties of the battery cell 38. The exact shape of the cells V OC -SOC curve 64 may vary based on the chemical formulation and other variables associated with the at least one of the battery cells 38. A battery V OC -SOC curve can be calculated using a relationship between the battery open circuit voltage V OC and the battery SOC. The exact shape of the battery V OC -SOC curve may vary based on one or more variables associated with the traction battery 26.

[0035] In one example, the V OC-SOC curves of the battery cells 38 are determined using tests. The battery controller 42 may be configured to maintain data related to the internal resistance R, the SOC, and / or the open circuit voltage V OC 54 of the battery cells 38 in the non-volatile memory. In one example, in response to estimating the battery cell SOC, SOC cell_est the battery control 42 the open circuit voltage V OC 54 using the V OC -SOC curve, e.g., curve 64.

[0036] The battery controller 42 may be configured to control the terminal voltage V t_gesch of at least one of the battery cells 38 and / or the traction battery 26 in response to receiving a signal from the current sensor 44 indicative of a measured current. In one example, the battery controller 42 may be configured to measure the terminal voltage V t_geschin response to receiving a signal from the current sensor 44 indicating that a measured current is equal to I MAX In such an example, the battery controller 42 may estimate the terminal voltage V t_gesch of at least one of the battery cells 38 and / or the traction battery 26, as shown in equation (4): Vt_est=VOC−IMAXR

[0037] As previously explained with respect to equations (1) and (2), the battery controller 42 may be configured to control the terminal voltage V t_gesch during battery charging and / or battery cell charging using corresponding values ​​of internal resistance R and open circuit voltage V OC , which are created using the V OC -SOC curve. Although the terminal voltage V t_geschis estimated in the description using parameters identified at least in equations (3) and (4), other methods are also provided which use various parameters, variables and operating characteristics.

[0038] The battery controller 42 may be configured to measure the measured battery terminal voltage V t_gemessen in response to receiving a signal from the voltage sensor 46 indicative of the measured battery voltage. In one example, the battery controller 42 may be configured to determine that the measured terminal voltage V t_gemessen is equal to the measured battery voltage obtained from the voltage sensor 46. The battery controller 42 may be configured to measure the measured terminal voltage V t_gemessen in battery cell charging in response to receiving a signal from the cell sensor 50 indicative of the measured cell voltage.

[0039] The battery controller 42 may be configured to detect a difference ΔV (or delta_V) between the estimated terminal voltage V t_gesch and the measured terminal voltage V t_gemessen The battery controller 42 may be further configured to determine whether delta_V is greater than a predetermined threshold. In one example, the battery controller 42 determines delta_V during battery charging, e.g., using the estimated battery terminal voltage V t_gesch and the measured battery terminal voltage V t_gemessen , and compares delta_V to a predetermined threshold associated with the terminal voltage during battery charging. In another example, the battery controller 42 determines delta_V during cell charging, e.g., using the estimated cell terminal voltage V t_gesch and the measured cell terminal voltage V t_gemessen, and compares delta_V with a predetermined threshold value linked to the terminal voltage during cell charging.

[0040] The battery controller 42 may transmit a signal indicating that an overcurrent condition has occurred in response to determining that delta_V is greater than a predetermined threshold. The battery controller 42 may command the BEC 40 to open one or more switches in response to determining that delta_V is greater than a predetermined threshold. In one example, the battery controller 42 may command the BEC 40 to open the positive and negative main contactors, thereby disconnecting the traction battery 26 from a high-voltage (HV) bus. In another example, the battery controller 42 may be configured to reduce the available power of the traction battery 26.

[0041] With reference to Fig.5, a control strategy 70 for diagnosing an overcurrent condition is shown. The control strategy 70 may begin at block 72, where the battery controller 42 receives a signal from the current sensor 44 indicating the value of the measured current I GEMESSEN In an example, the measured current I GEMESSEN Current through the traction battery 26. In certain configurations and / or arrangements of the one or more battery cells 38 of the traction battery 26, e.g., a series arrangement, the obtained measured current I GEMESSEN current through the one or more battery cells 38. The battery controller 42 at block 74 determines whether the measured current I GEMESSEN as strong as the upper operating point (or upper limit) I MAX of the current sensor 44. The battery controller 42 terminates the control strategy 70 in response to determining that the measured current I GEMESSENnot as strong as the upper operating point (or upper limit) I MAX of the current sensor 44.

[0042] In response to determining at block 74 that the measured current I GEMESSEN as strong as the upper operating point (or upper limit) I MAX of the current sensor 44, the battery controller 42 estimates the terminal voltage V at block 76 t_gesch . In one example, the battery controller 42 estimates the cell terminal voltage V t_gesch based on the internal resistance R, the value of I MAX and the open circuit voltage V OC 54, which is based on cells V OC -SOC curve is determined as previously described with respect to equation (4). In another example, the battery controller 42 estimates the terminal voltage V t_gesch of the traction battery 26 based on the internal resistance R of the battery, the value of I MAX and the battery open circuit voltage V OC, where the internal voltage R of the battery can be a sum of the internal resistances of the battery cells 38 and the battery open circuit voltage V OC a sum of the open circuit voltages V OC the battery cells can be 38.

[0043] At block 78, the battery control 42 determines the measured terminal voltage V t_gemessen In one example, the measured terminal voltage V t_gemessen the voltage of the one or more battery cells 38 measured by the cell sensor 50. In another example, the measured terminal voltage V t_gemessen the voltage of the traction battery 26, which is measured by the voltage sensor 46.

[0044] At block 80, the battery controller 42 determines a difference ΔV (or delta_V) between the estimated terminal voltage V t_gesch and the measured terminal voltage V t_gemessen. The battery controller 42 determines at block 82 whether delta_V is greater than a predetermined threshold. The battery controller 42 terminates the control strategy 70 in response to determining that delta_V is less than a predetermined threshold. At block 84, in response to determining at block 82 that delta_V is greater than a predetermined threshold, the battery controller 42 issues a diagnostic message, i.e., transmits a signal indicating that an overcurrent condition has occurred. In one example, the battery controller 42 may be configured to command the BEC 40 to open the positive and negative main contactors, thereby disconnecting the traction battery 26 from a high-voltage (HV) bus in response to determining at block 82 that delta_V is greater than a predetermined threshold.In another example, battery controller 42 may be configured to decrease the available power of traction battery 26 in response to determining at block 82 that delta_V is greater than a predetermined threshold. At this point, control strategy 70 may end. In some embodiments, control strategy 70 may be repeated in response to receiving a signal indicative of a battery current value or in response to another signal or request.

[0045] The processes, methods, or algorithms disclosed herein may be delivered to or implemented by a processing device, controller, or computer, which may include any existing programmable electronic control unit or dedicated electronic control unit. Likewise, the processes, methods, or algorithms may be stored as data and instructions executable by a controller or computer in many forms, including, but not limited to, information permanently stored on non-writable storage media, such as read-only memory devices, and information modifiably stored on writable storage media, such as floppy disks, magnetic tapes, compact discs, RAM devices, and other magnetic and optical media. The processes, methods, or algorithms may also be implemented in a software-executable object.Alternatively, the processes, methods, or algorithms may be implemented in whole or in part using suitable hardware components, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), state machines, controllers, or other hardware components or devices, or a combination of hardware, software, and firmware components.

[0046] The terms used in the specification are for the purpose of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments may be combined to form other embodiments of the invention that may not be explicitly described or illustrated. However, while various embodiments have been described as being advantageous or preferred with respect to one or more desired characteristics over other embodiments or prior art implementations, it will be apparent to one of ordinary skill in the art that one or more characteristics may be compromised to achieve the desired overall system characteristics, depending on the particular application and implementation.These features may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Thus, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for certain applications.

Claims

[1] Diagnostic system for a vehicle (12), comprising: a traction battery (26) having a plurality of cells; and a controller configured to detect an overcurrent condition in response to that the battery current is greater than a value of an upper limit of a current sensor (44) and a difference between a measured battery voltage and an estimated battery voltage based on the value is greater than a threshold. [2] The diagnostic system of claim 1, wherein the measured and estimated battery voltages are voltages (54) associated with the battery or one of the plurality of cells of the battery, and wherein the difference is greater than a threshold associated with the battery or one of the plurality of cells. [3] The diagnostic system of claim 2, wherein the estimated voltage (54) associated with the battery is further based on a sum of voltages (54) associated with the plurality of cells. [4] The diagnostic system of claim 1, wherein the controller is further configured to indicate the overcurrent condition based on a difference between an open circuit voltage (54) and a product of the value and an internal resistance of the battery. [5] The diagnostic system of claim 1, wherein the controller is further configured to indicate the overcurrent condition based on the battery age, the battery state of charge, and the battery temperature when the battery current was measured. [6] The diagnostic system of claim 5, wherein the battery charge level is based on the value and the battery capacity. [7] The diagnostic system of claim 1, wherein the controller is further configured to, in response to indicating the overcurrent condition, reduce the available battery power or disconnect the battery by opening battery contactors connecting the battery to a high voltage bus. [8] Method for a traction battery (26) of a vehicle (12), comprising: Indicating by a controller an overcurrent condition in response to the battery current being greater than an upper limit value of a current sensor (44) and a difference between a measured battery voltage and an estimated battery voltage based on the value is greater than a threshold. [9] The method of claim 8, wherein the measured and estimated battery voltages are voltages (54) associated with the battery or one of a plurality of cells of the battery, and wherein the difference is greater than a threshold associated with the battery or one of the plurality of cells. [10] The method of claim 9, wherein the estimated voltage (54) associated with the battery is further based on a sum of voltages (54) associated with the plurality of cells. [11] The method of claim 8, wherein indicating the overcurrent condition is further based on a difference between an open circuit voltage (54) and a product of the value and an internal resistance of the battery. [12] The method of claim 8, wherein indicating the overcurrent condition is further based on battery age, battery state of charge, and battery temperature when the battery current was measured. [13] The method of claim 12, wherein the battery state of charge is based on the value and a battery capacity. [14] The method of claim 8, further comprising reducing available battery power or disconnecting the battery by opening battery contactors connecting the battery to a high voltage bus in response to the indication of the overcurrent condition. [15] Traction battery (26) for a vehicle (12), comprising: several cells; and a pair of sensors, each configured to measure a different operating parameter of the cells and to transmit the measured parameter to a battery controller (42), wherein the controller is configured to indicate a diagnostic condition in response to at least one of the measured parameters being at least equal to an upper limit value of the corresponding sensor and a difference between another measured parameter and an estimate of the other measured parameter based on the value being greater than a threshold. [16] The traction battery (26) of claim 15, wherein the pair of sensors are a current sensor (44) and a terminal voltage sensor, and wherein the other measured parameter is a measured voltage (54) and the estimate of the other measured parameter is an estimated voltage (54). [17] The traction battery (26) of claim 16, wherein the controller is further configured to obtain the estimated voltage (54) based on an open circuit voltage (54) that is based on a state of charge based on the value. [18] The traction battery (26) of claim 16, wherein the controller is further configured to obtain the estimated voltage (54) based on a difference between an open circuit voltage (54) and a product of the value and an internal resistance. [19] The traction battery (26) of claim 16, wherein the controller is further configured to indicate the diagnostic condition based on the internal resistance resulting from the cell age, the cell state of charge, and the cell temperature when the current was measured. [20] The traction battery (26) of claim 16, wherein the controller is further configured to, in response to indicating the diagnostic condition, reduce available battery power or disconnect the traction battery (26) by opening battery contactors connecting the traction battery (26) to a high voltage bus.

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