Low voltage battery health diagnosis

Abstract

A method of evaluating a low voltage (LV) battery system includes collecting parameters of the LV battery system, determining a health of the LV battery system based on one or more health indicators of a plurality of health indicators, and based on determining that the battery system is in an unhealth condition, identifying a cause of the unhealth condition based on a selection of a set of health indicators. Determining health includes identifying an enable condition associated with charging or discharging of the LV battery system, selecting a set of health indicators from a plurality of health indicators based on the identified enable condition, estimating a value for each of the set of health indicators, and determining health of the LV battery system. And determining whether the LV battery system is in a healthy condition or an unhealthy condition based on the collected parameter and a value of each of the set of health indicators.

Description

Technical Field

[0001] The subject disclosure relates to battery systems, and more particularly to systems and methods for evaluating or assessing low voltage battery systems in vehicles and / or other environments. Background Art

[0002] Vehicles, including gasoline and diesel powered vehicles, as well as electric and hybrid vehicles, feature battery storage for purposes such as powering electric motors, electronic devices, and other vehicle subsystems. Various battery assemblies may be included to provide power to a wide range of loads. For example, electric vehicles and hybrid vehicles include high voltage battery assemblies for powering high voltage loads (e.g., motors) and low voltage battery assemblies for powering low voltage loads (e.g., electronic devices, lighting, etc.). Summary of the invention

[0003] In one exemplary embodiment, a method of evaluating a low voltage (LV) battery system includes collecting parameters of the LV battery system, the parameters including at least one of voltage, current, temperature, and state of charge (SOC), determining a health of the LV battery system based on one or more health indicators of a plurality of health indicators, and based on determining that the battery system is in an unhealthy state, identifying a cause of the unhealthy state based on a selection of a set of health indicators. Determining the health includes identifying an enabling condition associated with charging or discharging the LV battery system, selecting a set of health indicators from the plurality of health indicators based on the identified enabling condition, estimating a value for each of the set of health indicators, and determining whether the LV battery system is in a healthy state or an unhealthy state based on the collected parameters and the values ​​of each of the set of health indicators.

[0004] In addition to one or more of the features described herein, the plurality of health indicators include charge resistance, ripple resistance, dynamic discharge resistance, and capacity ratio, which is a ratio of capacity change to voltage change.

[0005] In addition to one or more features described herein, the cause is identified as a shorted battery cell in the LV battery system based on the charging resistance having a value higher than a charging resistance threshold, the cause is identified as a low state of health (SOH) based on at least one of the value of the charging resistance being higher than a charging resistance threshold, the value of the fluctuation resistance being higher than a fluctuation resistance threshold, the value of the dynamic discharge resistance being higher than a discharge resistance threshold, and the value of the capacity ratio being at or below a capacity ratio threshold, and the cause is identified as a low SOC based on the collected SOC being lower than a selected SOC, and at least one of the value of the charging resistance being at or below a charging resistance threshold, the value of the fluctuation resistance being at or below a fluctuation resistance threshold, the value of the dynamic discharge resistance being at or below a discharge resistance threshold, and the value of the capacity ratio being higher than a capacity ratio threshold.

[0006] In addition to one or more features described herein, the enabling conditions for the charge resistance and the fluctuation resistance are charging conditions where the LV battery system is charging, and the enabling conditions for the dynamic discharge resistance and the capacity ratio are discharging conditions where the LV battery system is discharging.

[0007] In addition to one or more of the features described herein, the enabling conditions of the capacity ratio and the dynamic discharge resistance are conditions for shutting down the LV battery system for a selected period of time.

[0008] In addition to one or more features described herein, a value of the dynamic discharge resistor is calculated based on a regression of current values ​​sampled during a selected time period.

[0009] In addition to one or more features described herein, a value of the capacity ratio is calculated based on integrating current values ​​sampled during a selected time period.

[0010] In addition to one or more features described herein, the LV battery system is part of a vehicle that includes a high voltage battery system configured to power an electric motor.

[0011] In another exemplary embodiment, a system for evaluating a low voltage (LV) battery system includes a processing device configured to collect parameters of the LV battery system, the parameters including at least one of voltage, current, temperature, and state of charge (SOC), the processing device configured to determine a health of the LV battery system based on one or more health indicators of a plurality of health indicators, and based on determining that the battery system is in an unhealthy state, identify a cause of the unhealthy state based on a selection of a set of health indicators. The processing device is configured to determine the health by identifying an enabling condition of the battery system, the enabling condition being related to charging or discharging of the battery system, selecting a set of health indicators based on the identified enabling condition, estimating a value for each of the set of health indicators, and determining whether the LV battery system is in a healthy state or an unhealthy state based on the collected parameters and the values ​​of each of the set of health indicators.

[0012] In addition to one or more features described herein, the plurality of health indicators include charge resistance, fluctuation resistance, dynamic discharge resistance, and capacity ratio, which is a ratio of capacity change to voltage change.

[0013] In addition to one or more features described herein, the cause is identified as a shorted battery cell in the LV battery system based on the charging resistance having a value higher than a charging resistance threshold, the cause is identified as a low state of health (SOH) based on at least one of the value of the charging resistance being higher than a charging resistance threshold, the value of the fluctuation resistance being higher than a fluctuation resistance threshold, the value of the dynamic discharge resistance being higher than a discharge resistance threshold, and the value of the capacity ratio being at or below a capacity ratio threshold, and the cause is identified as a low SOC based on the collected SOC being lower than a selected SOC, and at least one of the value of the charging resistance being at or below a charging resistance threshold, the value of the fluctuation resistance being at or below a fluctuation resistance threshold, the value of the dynamic discharge resistance being at or below a discharge resistance threshold, and the value of the capacity ratio being higher than a capacity ratio threshold.

[0014] In addition to one or more features described herein, the enabling conditions for the charge resistance and the fluctuation resistance are charging conditions where the LV battery system is charging, and the enabling conditions for the dynamic discharge resistance and the capacity ratio are discharging conditions where the LV battery system is discharging.

[0015] In addition to one or more of the features described herein, the enabling conditions of the capacity ratio and the dynamic discharge resistance are conditions for shutting down the LV battery system for a selected period of time.

[0016] In addition to one or more features described herein, a value of the dynamic discharge resistor is calculated based on a regression of current values ​​sampled during a selected time period.

[0017] In addition to one or more features described herein, a value of the capacity ratio is calculated based on integrating current values ​​sampled during a selected time period.

[0018] In addition to one or more features described herein, the LV battery system is part of a vehicle that includes a high voltage battery system configured to power an electric motor.

[0019] In yet another exemplary embodiment, a vehicle system includes a low voltage (LV) battery system configured to power a LV component of a vehicle, and a processing device configured to collect parameters of the LV battery system, the parameters including at least one of voltage, current, temperature, and state of charge (SOC), the processing device configured to determine a health state of the LV battery system based on one or more health indicators of a plurality of health indicators, and based on determining that the battery system is in an unhealthy state, identify a cause of the unhealthy state based on a selection of a set of health indicators. The processing device is configured to determine the health state by identifying an enabling condition of the battery system, the enabling condition being related to charging or discharging of the battery system, selecting the set of health indicators based on the identified enabling condition, estimating a value for each of the set of health indicators, and determining whether the LV battery system is in a healthy state or an unhealthy state based on the collected parameters and the value of each of the set of health indicators.

[0020] In addition to one or more features described herein, the plurality of health indicators include charge resistance, fluctuation resistance, dynamic discharge resistance, and capacity ratio, which is a ratio of capacity change to voltage change.

[0021] In addition to one or more features described herein, the cause is identified as a shorted battery cell in the LV battery system based on the charging resistance having a value higher than a charging resistance threshold, the cause is identified as a low state of health (SOH) based on at least one of the value of the charging resistance being higher than a charging resistance threshold, the value of the fluctuation resistance being higher than a fluctuation resistance threshold, the value of the dynamic discharge resistance being higher than a discharge resistance threshold, and the value of the capacity ratio being at or below a capacity ratio threshold, and the cause is identified as a low SOC based on the collected SOC being lower than a selected SOC, and at least one of the value of the charging resistance being at or below a charging resistance threshold, the value of the fluctuation resistance being at or below a fluctuation resistance threshold, the value of the dynamic discharge resistance being at or below a discharge resistance threshold, and the value of the capacity ratio being higher than a capacity ratio threshold.

[0022] In addition to one or more features described herein, the enabling conditions for the charge resistance and the fluctuation resistance are charging conditions where the LV battery system is charging, and the enabling conditions for the dynamic discharge resistance and the capacity ratio are discharging conditions where the LV battery system is discharging.

[0023] The above features and advantages and other features and advantages of the present disclosure are apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, advantages and details appear, by way of example only, in the following detailed description, which refers to the accompanying drawings, in which:

[0025] Figure 1is a top schematic view of a motor vehicle including a high-voltage battery system and a low-voltage battery system according to an exemplary embodiment;

[0026] Figure 2 is a flow chart depicting aspects of a method of assessing the health of a low-voltage battery based on one or more health indicators according to an exemplary embodiment;

[0027] Figure 3 is a flow chart depicting aspects of a method of estimating a dynamic discharge resistor health indicator according to an exemplary embodiment;

[0028] Figure 4 is a flow chart depicting aspects of a method of estimating a capacity ratio health indicator according to an exemplary embodiment;

[0029] Figures 5A-5D depicts examples of health indicator values ​​associated with healthy and unhealthy states of a low voltage battery; and

[0030] Figure 6 A computer system according to an exemplary embodiment is depicted. DETAILED DESCRIPTION

[0031] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate the same or corresponding parts and features.

[0032] According to one or more exemplary embodiments, methods, devices, and systems for monitoring and evaluating a battery system and / or estimating the health of a battery system are provided. Embodiments of the method include collecting measurement data of a low-voltage battery, such as in an electric vehicle. Based on the presence of one or more enabling conditions, one or more health indicators are selected and their values ​​are estimated for use in determining or predicting an unhealthy state. In one embodiment, one or more health indicators are selected from a group including charging resistance, fluctuation resistance, dynamic discharge resistance, and capacity ratio (i.e., the ratio of capacity change to voltage change).

[0033] One or more values ​​of the selected health indicator are compared to various thresholds (e.g., in conjunction with battery parameters such as state of charge and open circuit voltage). If the value is not within a healthy range defined by the threshold, the method includes determining or predicting that the low voltage battery is in an unhealthy state. The method may also include identifying a cause of the unhealthy state based on which health indicator(s) were selected. Information about the battery health may be stored and / or presented to a user or other system so that the unhealthy state can be addressed.

[0034] The embodiments described herein present many advantages and technical effects. The embodiments provide an effective method for determining battery health that overcomes existing limitations. For example, a low-voltage battery in a vehicle with an internal combustion engine can be evaluated by monitoring health indicators (e.g., crank voltage, current, and resistance) when the vehicle's starter is operated. However, pure electric vehicles do not have a starter; therefore, these indicators are not available. The embodiments provide effective battery monitoring by providing health indicators that are independent of the starter.

[0035] Additionally, monitoring low voltage batteries and assessing battery health is difficult using conventional battery measurements and health assessments. For example, isolating battery faults or health status from voltage and current measurements (e.g., current / voltage scatter plots) is challenging due to nonlinear data distributions and noise factors. Resistance estimation is also challenging due to a lack of battery excitation in many cases. Other indicators of battery health, such as capacity estimation, are difficult due to inaccuracies in state of charge measurements. The embodiments described herein overcome these limitations by using a variety of health indicators that can be evaluated under a variety of conditions.

[0036] Embodiments are not limited to use with any particular vehicle or device or system utilizing a battery assembly and may be applicable in a variety of environments. For example, embodiments may be used with automobiles, trucks, aircraft, construction equipment, farm equipment, automated factory equipment, and / or any other device or system that may use a high voltage battery pack or other battery assembly.

[0037] Figure 1 An embodiment of a motor vehicle 10 is shown that includes a body 12 that at least partially defines an occupant compartment 14. The body 12 also supports various vehicle subsystems, including a propulsion system 16, and other subsystems for supporting the functions of the propulsion system 16 and other vehicle components, such as a braking subsystem, a suspension system, a steering subsystem, and if the vehicle is a hybrid electric vehicle, a fuel injection subsystem, an exhaust subsystem, etc.

[0038] The vehicle 10 may be an electric vehicle (EV), a hybrid vehicle, or any other vehicle. In one embodiment, the vehicle 10 is an electric vehicle that includes one or more electric motors and one or more drive systems. For example, the propulsion system 16 includes a drive unit 20 having an electric motor 22 and an inverter 24, as well as other components such as a cooling system 26. The inverter 24 (e.g., a traction power inverter unit or TPIM) converts direct current (DC) power from a high voltage (HV) battery system 30 into multi-phase (e.g., two-phase, three-phase, six-phase, etc.) alternating current (AC) power to drive the motor 22. The battery system 30 may be configured as a rechargeable energy storage system (RESS).

[0039] The HV battery system 30 includes one or more battery assemblies. For example, the HV battery system 30 includes a high voltage (e.g., 400V) battery pack 32 connected to the inverter 24. The battery pack 32 includes a plurality of battery modules 34, and each module 34 includes a plurality of individual battery cells (not shown). The battery pack 32 may be a single pack as shown, or may include a plurality of packs. The HV battery system 30 may be a rechargeable energy storage system (RESS), which may include various sensors that may be read by a monitoring device such as a RESS controller 36.

[0040] The HV battery system 30 can be electrically connected to other components, such as vehicle electronics and / or other battery systems. For example, the vehicle 10 includes at least one low voltage (LV) battery system, which includes an LV battery 40 (e.g., a 12 volt (V) battery pack). The LV battery 40 has a lower rated voltage than the HV battery pack 32. The voltage of the LV battery 40 can be 12V, 48V, or any other suitable voltage. The LV battery 40 can also be a variable voltage battery system.

[0041] Note that the terms “high voltage” and “low voltage” are relative terms. Thus, these terms are not intended to limit the HV battery system 30 or the LV battery 40 to any particular rated voltage.

[0042] Various aspects of power transfer are controlled via a control device such as an auxiliary power module (APM), referred to as an LV controller 42. Power transfer includes discharging the LV battery 40, for example, to power electronics and other components of the vehicle 10. Power transfer also includes charging the LV battery 40 (e.g., from the battery pack 32 or an external source).

[0043] The LV battery 40 is used to power various components during vehicle modes or states. For example, when the vehicle 10 is turned on and / or in propulsion mode, the LV battery 40 powers vehicle controllers, power windows, power locks, lighting, and / or other LV components. When the vehicle 10 is turned off, the LV battery 40 powers all or selected vehicle controllers so that certain vehicle functions are maintained. For example, the LV battery 40 powers the controllers so that the vehicle 10 can be turned on and switched on. In one embodiment, when the vehicle is turned off, the vehicle 10 enters a power-off mode. During the power-off mode, the LV battery 40 continues to provide power to the vehicle controllers so that the vehicle 10 can be switched on.

[0044] The vehicle 10 also includes a charging system that can be used to charge the battery system 30 and / or supply power from the battery system 30 to charge another energy storage system (e.g., vehicle-to-vehicle (V2V) and / or vehicle-to-everything (V2X) charging). In one embodiment, the charging system includes a charging control device 44, such as an on-board charging module (OBCM). The charging control device 44 connects the battery system 30 to a charging port 46 for charging the vehicle battery system and / or providing charge to an external storage system.

[0045] The vehicle 10 also includes a computer system 50, which includes one or more processing devices 52 and a user interface 54. The computer system 50 can communicate with other controllers, for example, to provide commands thereto in response to user input. The various processing devices, modules, and units can communicate with each other via a communication device or system, such as a controller area network (CAN) or a transmission control protocol (TCP) bus.

[0046] The charging system, RESS controller 36, LV controller 42, computer system 50, and / or other processing components in vehicle 10 may be configured to communicate with various remote devices and systems such as charging stations and other vehicles. Such communication may be achieved, for example, via a network 56 (e.g., a cellular network, the cloud, etc.) and / or via wireless communications. For example, vehicle 10 may communicate with one or more charging stations 58, remote entities 60 (e.g., a workstation, a fleet management system, a computer, a server, a service provider, a technician, an engineer, etc.), and / or another vehicle 62.

[0047] The vehicle 10 includes or is connected to a battery monitoring and diagnostic system that is configured to collect various parameters of the LV battery 40 and assess the battery health based on one or more health indicators. The diagnostic system includes at least one processing device, which may be an internal control device such as the LV controller 42 or the RESS controller 36, and / or a remote device such as a processing device of the remote entity 60. The diagnostic system may include any number and combination of processing devices that may acquire battery measurements and other information and determine battery health as described herein.

[0048] The diagnostic system utilizes one or more estimated or predicted battery characteristics or properties, which are referred to herein as "health indicators." The health indicators are used to determine whether an LV battery system, such as LV battery 40, is healthy, and may also be used to identify the cause of an unhealthy battery condition. The diagnostic system may utilize any number and combination of health indicators to determine battery health.

[0049] For purposes of illustration, the health indicators and methods are described herein in conjunction with the LV battery 40 and the vehicle 10. It should be appreciated that the embodiments described herein are applicable to any suitable battery system in any suitable context.

[0050] As further discussed herein, the diagnostic system is configured to determine battery health by selecting one or more health indicators from a plurality of health indicators. In one embodiment, the plurality of health indicators include charge resistance, fluctuation resistance, dynamic discharge resistance, and capacity ratio.

[0051] The charge resistance is the resistance of the battery system during charging, denoted as Rc. This health indicator, which may also be characterized as charge acceptance, is estimated based on measurements taken during a vehicle mode in which a charge is provided to the LV battery 40. The LV battery 40 may be charged from the HV battery system 30 during vehicle operation, and / or when the HV battery system 30 is charging (e.g., when the vehicle 10 is plugged into an electrical grid or a charging station). In one embodiment, Rc is estimated based on measurements taken when a constant or varying charging current is applied to the LV battery 40.

[0052] Rc is estimated by collecting voltage (V) and current (I) measurements along with other information such as the open circuit voltage and state of charge of the battery system. Rc can be estimated using the Shepherd equation, which relates the voltage drop across an internal resistor to the charging current.

[0053] For example, Rc is calculated based on the following equation:

[0054]

[0055] Where OCV is the open circuit voltage, SOC is the state of charge, Vc is the voltage measured during constant charge, and Ic is the current measured during constant charge. Cn is the nominal capacity, Mc is the charge transfer overvoltage coefficient, and Cc is the normalized capacity. Generally, lower Rc values ​​correspond to greater battery health.

[0056] Another health indicator is the resistance of the battery system during discharge, which is called the dynamic discharge resistance and is represented by Rd. This health indicator is estimated based on measurements performed during discharge. For example, Rd is estimated based on measurements performed when the vehicle 10 is in accessory mode or other operating state where the LV battery 40 is providing power to various low voltage components (such as controllers, lighting, infotainment systems, etc.).

[0057] As discussed further herein, Rd is estimated by collecting voltage and current measurements and performing a regression of the samples performed during the power-off period. Generally, lower Rd values ​​correspond to greater battery health. The dynamic discharge resistance can be determined by sampling the current and voltage over a short period of time (e.g., a few seconds).

[0058] The capacity ratio is another health indicator, which is the ratio of the change in capacity Q to the change in voltage V during discharge. The change in capacity is represented as dQ, and the change in voltage is represented as dV. Therefore, the capacity ratio can be expressed as dQ / dV. A larger value of dQ / dV corresponds to a greater health.

[0059] The fluctuation resistance (also called nominal resistance) is denoted Rn and is a measure of the resistance to small disturbances (fluctuations) during charging. Lower Rn values ​​correspond to greater battery health.

[0060] The fluctuation resistance Rn is the ratio of the voltage change to the current change during charging. For example, Rn is calculated based on the following equation:

[0061]

[0062] Where V p1 is the voltage measured at the first sample time, V p2 is the voltage measured at the second sample time, I p1 is the current measured at the first sample time, and I p2 is the current measured at the second sample time.

[0063] Typically, the diagnostic system is configured to perform a method of estimating one or more health indicators and determining or predicting whether the battery is healthy. As described herein, a "healthy" battery has no detected faults and has a high state of health (SOH). The SOH can be determined as a percentage of the maximum battery charge to the rated capacity of the battery. A "high SOH" is an SOH above a selected value (e.g., 10%, 25%, or 50%).

[0064] The method includes measuring various battery parameters and determining whether a LV battery system (such as LV battery 40) is in an enabled condition. Based on the enabled condition, a set of health indicators (i.e., one or more) are selected. Values ​​of the selected health indicators are estimated and used to determine whether the LV battery system is healthy or unhealthy. Note that embodiments of the method can be passive (i.e., the battery can be evaluated without injecting a signal). Thus, the method can be performed without the need for an external signal source or a separate battery tester.

[0065] When determining that the battery system is unhealthy, the diagnostic system utilizes the selection of health indicators to identify the cause of the unhealthy condition. In this way, the health indicators can be used not only to determine the health of the battery system, but also to distinguish between various causes or problems that lead to the unhealthy condition.

[0066] Figure 2 An embodiment of a method 70 of assessing the health of a battery system is depicted. In one embodiment, the method is performed to assess a low voltage battery system (eg, 12V, 48V, etc.), such as the LV battery 40.

[0067] Method 70 includes a number of steps or stages represented by blocks 71-82. Method 70 is not limited to the number or order of steps therein, as some steps represented by blocks 71-82 may be performed in a different order than described below, or fewer than all steps may be performed.

[0068] Combination Figure 1 The method 70 is described with reference to, but not limited to, the LV controller 42 of FIG. The method 70 may be performed by any suitable processing device or system, such as a local processor (e.g., a BMS controller or RESS controller 36) and / or a remote processor (e.g., a fleet management system, a data center, or other remote entity 60).

[0069] Method 70 can be used to make a final determination about the health and / or causes of an unhealthy battery. Alternatively, aspects of method 70 (e.g., selection of health indicators and / or calculation of health indicator values) can be performed as part of and / or in conjunction with other diagnostic methods.

[0070] Additionally, the method 70 is not limited to the specific health indicator calculations and conditions described therein, as other combinations of health indicators may be used. Additionally, the method 70 may encompass multiple variations in techniques for calculating or estimating health indicator values.

[0071] At box 71, a trigger signal is received by a processor such as the LV controller 42. For example, the collection of battery parameters is triggered by a power-on signal or a wake-up signal from the vehicle controller.

[0072] At box 72, various battery parameters associated with the LV battery 40 (or other low voltage battery system) are collected during a given vehicle mode. The various parameters include current, voltage, SOC, OCV, and / or other information related to battery health and health indicators. OCV can be obtained from stored information (e.g., automatically measured when the vehicle 10 is turned off).

[0073] A set of health indicators (i.e., one or more) is selected from a plurality of health indicators. In one embodiment, the plurality of health indicators include a charging resistance Rc, a dynamic discharge resistance Rd, a capacity ratio dQ / dV, and a fluctuation resistance Rn. The values ​​of the health indicators can take any suitable form. For example, the health indicator values ​​can be original values, normalized values, and / or various derivative values ​​from the original values. For example, the health indicator values ​​can be expressed as discrete values, ranges of values, maximum values, minimum values, medians, average values, trends, variances, standard deviations, or other measurements. In addition, the health indicator values ​​can be normalized to SOC, temperature, and / or other parameters.

[0074] In one embodiment, health indicator selection is performed in response to vehicle 10 and / or battery system satisfying one or more enabling conditions. An enabling condition is a condition that facilitates estimating at least one health indicator.

[0075] One enabling condition is a charging condition, such as a condition that the LV battery 40 is being charged. The charging condition may occur when the LV battery 40 is charged from an external source, or when the LV battery 40 is charged by the HV battery system 30. The charging condition is an enabling condition of the charging resistor Rc and the fluctuating resistor Rn.

[0076] Another enabling condition is a discharge condition, in which the LV battery 40 supplies power to the controller and / or other vehicle components. The discharge condition may be an enabling condition for the dynamic discharge resistance Rd and the capacity ratio dQ / dV. Other enabling conditions for Rd and dQ / dV are discussed further herein (see Figure 3 and Figure 4 ).

[0077] At box 73, the SOC is compared to an SOC threshold and at least one selected health indicator value is compared to a corresponding threshold. If the SOC is greater than the SOC threshold and at least one health indicator value indicates a healthy battery, the processor determines that the LV battery 40 is in a healthy state (box 74).

[0078] For example, if the vehicle 10 is in a charging state, the value of the charging resistance Rc is compared with the charging resistance threshold, and the value of the fluctuation resistance Rn is compared with the fluctuation resistance threshold. If the SOC exceeds the SOC threshold, and the charging resistance Rc value indicates a healthy battery (i.e., Rc is less than the charging resistance threshold) or the fluctuation resistance Rn value indicates a healthy battery (i.e., Rn is less than the fluctuation resistance threshold), the LV battery 40 is determined to be in a healthy state.

[0079] Likewise, if the vehicle 10 is in a discharge state, the value of the dynamic discharge resistance Rd is compared to the discharge resistance threshold, and the value of the capacity ratio dQ / dV is compared to the capacity ratio threshold. If the SOC exceeds the SOC threshold, and the dynamic discharge resistance Rd value indicates a healthy battery (i.e., Rd is less than the discharge resistance threshold) or the capacity ratio dQ / dV value indicates a healthy battery (i.e., dQ / dV is greater than the capacity ratio threshold), the LV battery 40 is determined to be in a healthy state.

[0080] At box 75, if the LV battery 40 is not in a healthy state, the processor compares the OCV to a threshold value. If the OCV is less than the threshold value (i.e., "low OCV"), and the vehicle 10 is in a charging condition, the charging resistance Rc value is compared to the charging resistance threshold value (box 76). If the Rc value exceeds the threshold value, the processor determines that the LV battery 40 is in a "short cell battery condition" in which a cell in the battery 40 has been or will be shorted (box 77).

[0081] At box 78 , if the OCV is greater than or equal to the OCV threshold, the selected health indicator is compared to its corresponding threshold. If none of the health indicators meet their respective thresholds, the processor determines at box 79 that the LV battery 40 is in a low state of health (SOH).

[0082] At box 80, the processor determines whether the SOC is below a selected SOC threshold. If so, the processor determines that the LV battery 40 has a low SOC (box 81), and may output this to a user or other system. If not, the LV battery 40 is considered to be in a healthy state (box 82).

[0083] Any of the identified conditions and battery measurements may be stored for later analysis. In addition, any of the identified conditions and / or measurements may be presented to a user (such as a driver or technician).

[0084] Figure 3 An embodiment of a method 90 for estimating a dynamic discharge resistance Rd is depicted. The method 90 includes a plurality of steps or stages represented by blocks 91-107. The method 90 is not limited to the number or order of steps therein, as some of the steps represented by blocks 91-107 may be performed in a different order than described below, or fewer than all of the steps may be performed. The method 90 may have a plurality of variations, such as different enabling conditions and different parameters for calculating Rd.

[0085] Combination Figure 1 The method 90 is described with reference to, but not limited to, the LV controller 42. The method 90 may be performed by any suitable processing device or system, such as a local processor and / or a remote processor.

[0086] At box 91, a processor such as LV controller 42 receives a trigger signal (e.g., a "power on" signal) from a vehicle control unit. In response, the processor determines the power mode of vehicle 10. For example, the collection of battery parameters is triggered by a power on signal or a wake-up signal from the vehicle controller.

[0087] If the vehicle 10 has been started (box 92), the power-on time is recorded at box 93. The processor monitors the power mode of the vehicle 10 and identifies when the power is turned off (box 94). When the power is off, the power off time is recorded (box 95).

[0088] At box 96, the processor calculates a power duration indicating the amount of time during which power is on, and compares the power duration to a minimum duration (e.g., 300 seconds). If the power duration is sufficient, the processor reads the current, voltage, and time for the desired time increment (box 97). Measurements are made at multiple sample times during the time increment. For example, at each sample time, a current value is measured.

[0089] At block 98, the current measured at the time increment is compared to the selected current value. For example, the sampled current (the current value at the sample time) is checked, and if the sampled current is negative (indicating discharge) and / or less than a threshold value (e.g., -1 amp), the sampled current value (e.g., having voltage and time samples) is stored in a circular buffer or other suitable data structure at block 99. Otherwise, the sampled current is not stored (e.g., discarded).

[0090] At box 100, the processor confirms that the vehicle control unit is still receiving power. If so, the processor compares the difference between the highest stored current value and the lowest stored current value over the time increment at box 101 and compares the difference to a threshold value (e.g., 8 amps). If the vehicle control unit is not receiving power, the method 90 ends (box 100a).

[0091] At box 102, if the difference is greater than or equal to the difference threshold, then a sufficient number of samples have been collected for performing regression and / or other analysis. At box 103, the stored current values ​​(data points) are checked, and at box 104 the data size (i.e., the number of selected data points) is compared to a minimum size (e.g., 10 points). If the data size is less than the minimum size, then method 90 ends (box 104a). If the data size is greater than or equal to the minimum size, then the sampled current values ​​are used to estimate Rd.

[0092] At box 105, the selected current values ​​(samples) are used to create a one-dimensional array A = [I, 1], where I is the selected data point. At box 106, Rd is calculated based on the following equation:

[0093] Rd=(A T A) -1 A T V

[0094] Among them A T is the transpose of A, and V is the battery voltage during the power duration. This array is used for regression to calculate Rd as the slope between the minimum current and the maximum current. Blocks 105 and 106 represent one example of performing a regression; various other techniques may be used to perform the regression.

[0095] The calculated discharge resistance is stored and may be presented to a user or other entity (block 107 ).

[0096] Figure 4 An embodiment of a method 110 for estimating a capacity ratio dQ / dV is depicted. The method 110 includes a plurality of steps or stages represented by blocks 111-125. The method 110 is not limited to the number or order of steps therein, as some of the steps represented by blocks 111-125 may be performed in a different order than described below, or fewer than all of the steps may be performed.

[0097] Combination Figure 1 The method 110 is described with reference to, but not limited to, the LV controller 42. The method 110 may be performed by any suitable processing device or system, such as a local processor and / or a remote processor.

[0098] At box 111, a processor such as the LV controller 42 receives a trigger signal (e.g., a "power on" signal) from a vehicle control unit. In response, the processor determines the power mode of the vehicle 10. The method 110 is applicable to various vehicle modes (e.g., power on or wake up mode). It should be noted that the specific enabling conditions may vary for different vehicle modes.

[0099] If the vehicle 10 has been started (box 112), the power-on time is recorded at box 113. The processor monitors the power mode of the vehicle 10 and identifies when the power is turned off (box 114). When the power is off, the power-off time is recorded (box 115).

[0100] At block 116, the processor calculates a power duration indicating the amount of time during which power is on, and compares the power duration to a minimum duration (e.g., 300 seconds). If the power duration is sufficient, the processor reads the current, voltage, and time for the desired time increment (block 117). Measurements are made at multiple sample times during the time increment. For example, at each sample time, a current value is measured.

[0101] At block 118, the current measured at the time increment is compared to the selected current value. For example, the sampled current (the current value at the sample time) is checked, and if the sampled current is negative (indicating discharge) and / or less than a current threshold (e.g., -1 amp), the sampled current and voltage values ​​are stored in a circular buffer or other suitable data structure at block 119. Otherwise, the sampled current is not stored (e.g., discarded).

[0102] At block 120, the processor continues to receive current samples until the total sample time is at least a minimum time (e.g., 120 seconds). Once the total sample time exceeds the minimum time, at block 121, the processor selects a sample in which the current is less than a selected current value (e.g., -5 amps) and the voltage is within a selected range (e.g., greater than 12.7 V and less than 12.9 V).

[0103] At block 122, the number of selected samples is compared to a minimum number, such as 3. If the number of selected samples meets the criteria, the capacity ratio dQ / dV is calculated.

[0104] For example, at block 123, the charge value Q is calculated by integrating the current sample over time t as follows:

[0105]

[0106] Where t1 is the initial sample time and t2 is the final sample time.

[0107] At block 124, the capacity ratio dQ / dV may be calculated as:

[0108]

[0109] Where charge[0] is the Q value at time t1, charge[end] is the Q value at time t2, V[0] is the voltage at time t1, and V[end] is the voltage at time t2.

[0110] The capacity ratio dQ / dV is stored and may be presented to a user or other entity (block 125).

[0111] Figures 5A-5D Examples of health indicator values ​​are shown, and illustrate the advantages of the health indicators described herein. Figures 5A-5D Bar graphs are shown for each health indicator with the associated uncertainty as error bars. Figure 5A Estimated Rn values ​​in ohms (bar 130 ) and an average Rn value 132 for healthy batteries are shown compared to Rn values ​​134 and a median Rn value 136 for unhealthy batteries. Figure 5BEstimated dQ / dV values ​​in ampere-hours per volt (Ah / V) (bar 138 ) and average dQ / dV values ​​140 for healthy batteries are shown compared to dQ / dV values ​​142 and average dQ / dV values ​​144 for unhealthy batteries.

[0112] Figure 5C Estimated Rd values ​​(bar 146 ) and average Rn values ​​148 for healthy batteries are shown compared to Rd values ​​150 and average Rd values ​​152 for unhealthy batteries. Figure 5D Estimated Rc values ​​(bar 154 ) and average Rc value 156 for healthy batteries are shown compared to Rc values ​​158 and average Rc value 160 for unhealthy batteries.

[0113] As shown, these health indicators show very good separation between values ​​that indicate a healthy battery and values ​​that indicate an unhealthy battery. This separation makes detection of problems much easier than with other conventional indicators.

[0114] Figure 6 Aspects of an embodiment of a computer system 240 are shown that can perform various aspects of the embodiments described herein. The computer system 240 includes at least one processing device 242, which typically includes one or more processors for performing various aspects of the image acquisition and analysis methods described herein.

[0115] Components of computer system 240 include processing device 242 (such as one or more processors or processing units), memory 244, and bus 246, which couples various system components including system memory 244 to processing device 242. System memory 244 can be a non-transitory computer-readable medium and can include various computer system-readable media. Such media can be any available media that can be accessed by processing device 242, and includes volatile and non-volatile media and removable and non-removable media.

[0116] For example, system memory 244 includes non-volatile memory 248, such as a hard drive, and may also include volatile memory 250, such as random access memory (RAM) and / or cache memory. Computer system 240 may also include other removable / non-removable, volatile / non-volatile computer system storage media.

[0117] The system memory 244 may include at least one program product having a set (i.e., at least one) of program modules configured to perform the functions of the embodiments described herein. For example, the system memory 244 stores various program modules that generally perform the functions and / or methods of the embodiments described herein. A module 252 for performing functions related to acquiring signals and data may be included, and a module 254 for performing functions related to battery health determination as discussed herein may be included. The system 240 is not limited in this regard, as other modules may be included. As used herein, the term "module" refers to a processing circuit, which may include an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or grouped) and memory that executes one or more software or firmware programs, combinational logic circuits, and / or other suitable components that provide the described functions.

[0118] Processing device 242 may also communicate with one or more external devices 256, such as a keyboard, pointing device, and / or any device that enables processing device 242 to communicate with one or more other computing devices (e.g., a network card, a modem, etc.). Communication with various devices may occur via input / output (I / O) interfaces 264 and 265.

[0119] The processing device 242 may also communicate with one or more networks 266, such as a local area network (LAN), a general wide area network (WAN), a bus network, and / or a public network (e.g., the Internet) via a network adapter 268. It should be appreciated that, although not shown, other hardware and / or software components may be used in conjunction with the computer system 240. Examples include, but are not limited to, microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, and data archival storage systems, among others.

[0120] The terms "a" and "an" do not indicate a limitation of quantity, but rather indicate the presence of at least one of the referenced item. Unless the context clearly indicates otherwise, the term "or" means "and / or". References to "aspects" throughout the specification mean that a particular element (e.g., a feature, structure, step, or characteristic) described in conjunction with that aspect is included in at least one aspect described herein, and may or may not be present in other aspects. In addition, it should be understood that the described elements may be combined in any suitable manner in the various aspects.

[0121] When an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present.

[0122] Unless stated to the contrary herein, all test standards are the most current standards in effect as of the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the test standards appear.

[0123] Unless defined otherwise, 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.

[0124] 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 equivalents may be substituted for its elements without departing from its scope. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the disclosure without departing from the basic scope of the disclosure. Therefore, it is intended that the disclosure is not limited to the specific embodiments disclosed, but will include all embodiments falling within its scope.

Claims

1. A method for evaluating a low voltage (LV) battery system, comprising: collecting a parameter of the LV battery system, the parameter comprising at least one of voltage, current, temperature, and state of charge (SOC); determining a health of the LV battery system based on one or more health indicators of a plurality of health indicators; as well as Based on determining that the battery system is in an unhealthy state, identifying a cause of the unhealthy state based on a selection of a set of health indicators, wherein determining the health of the LV battery system includes: identifying an enabling condition associated with charging or discharging the LV battery system; selecting the set of health indicators from the plurality of health indicators based on the identified enabling condition, and estimating a value for each of the set of health indicators; and A determination is made as to whether the LV battery system is in a healthy state or an unhealthy state based on the collected parameters and the value of each of the set of health indicators.

2. The method of claim 1, wherein the plurality of health indicators include charge resistance, fluctuation resistance, dynamic discharge resistance, and capacity ratio, which is a ratio of capacity change to voltage change.

3. The method according to claim 2, wherein: identifying the cause as a shorted battery cell in the LV battery system based on the charging resistance having a value above a charging resistance threshold; identifying the cause as a low state of health (SOH) based on at least one of: a value of a charge resistance being above a charge resistance threshold, a value of a fluctuation resistance being above a fluctuation resistance threshold, a value of a dynamic discharge resistance being above a discharge resistance threshold, and a value of a capacity ratio being at or below a capacity ratio threshold; as well as The cause is identified as low SOC based on the collected SOC being lower than the selected SOC and at least one of the following: the value of the charging resistance is at or below a charging resistance threshold, the value of the fluctuation resistance is at or below a fluctuation resistance threshold, the value of the dynamic discharge resistance is at or below a discharge resistance threshold, and the value of the capacity ratio is higher than a capacity ratio threshold.

4. The method according to claim 2, wherein the enabling condition of the charging resistance and the fluctuating resistance is a charging condition that the LV battery system is being charged, and the enabling condition of the dynamic discharge resistance and the capacity ratio is a discharging condition that the LV battery system is being discharged.

5. The method of claim 4, wherein the enabling condition of the capacity ratio and the dynamic discharge resistance is a condition for the LV battery system to be shut down for a selected period of time.

6. The method of claim 5, wherein the value of the dynamic discharge resistor is calculated based on a regression of current values ​​sampled during a selected time period. 7 . The method of claim 5 , wherein the value of the capacity ratio is calculated based on integrating current values ​​sampled during a selected time period.

8. The method of claim 1, wherein the LV battery system is part of a vehicle including a high voltage battery system configured to power an electric motor.

9. A system for evaluating a low voltage (LV) battery system, comprising: a processing device configured to collect a parameter of the LV battery system, the parameter including at least one of voltage, current, temperature, and state of charge (SOC), the processing device configured to determine a health of the LV battery system based on one or more health indicators of a plurality of health indicators, and based on determining that the battery system is in an unhealthy state, identify a cause of the unhealthy state based on a selection of a set of health indicators, wherein the processing device is configured to determine the health by: identifying an enabling condition of the battery system, the enabling condition being related to charging or discharging of the battery system; selecting the set of health indicators based on the identified enabling condition, and estimating a value for each of the set of health indicators; as well as A determination is made as to whether the LV battery system is in a healthy state or an unhealthy state based on the collected parameters and the values ​​of each of the set of health indicators.

10. The system of claim 9, wherein the plurality of health indicators include a charge resistance, a fluctuation resistance, a dynamic discharge resistance, and a capacity ratio, the capacity ratio being a ratio of a capacity change to a voltage change.

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