VEHICLE WITH A TRACTION BATTERY WITH AT LEAST ONE CELL

Abstract

Vehicle (112) with a traction battery (124) comprising at least one cell, comprising the following: an internal combustion engine (118); and a control unit (146, 172) that is coupled and programmed to the traction battery (124) • a traction battery current, • an operating point of the internal combustion engine (118) and • a previously saved lookup table of battery charging power versus temperature to change in response to a difference between a lithium plating parameter target value and a current lithium plating parameter value in order to reduce the difference, wherein the lithium plating parameter is based on a ratio of a differential voltage of the at least one cell as a time function to a cell charging rate of the at least one cell; characterized by the fact that the controller (146, 172) is programmed to identify a lithium-plated cell based on a ratio between an open-circuit voltage and a traction battery state of charge for state-of-charge values ​​below a threshold after the traction battery (124) has been discharged for a predetermined time to allow complete lithium stripping.

Description

AREA OF TECHNOLOGY

[0001] This disclosure relates to closed-loop feedback control of an electrically powered vehicle in response to the detection of lithium plating in a vehicle battery. BACKGROUND

[0002] Electrically powered vehicles, such as hybrid, plug-in hybrid, and battery electric vehicles, use an electric motor powered by a traction battery to drive the vehicle's powertrain. Charging and discharging the battery results in electrochemical processes that affect the charge available to power the vehicle and can vary with environmental and operating conditions, such as battery state of charge (SOC), temperature, battery cell equilibrium, and / or charge / discharge rate or current. In lithium-ion (Li-ion) batteries, under certain operating conditions, metallic lithium can be deposited on the anodes of battery cells, which can degrade battery performance.

[0003] German patent application DE 10 2015 016 987 A1 discloses a method for detecting degradation of a rechargeable battery cell, in which a terminal voltage is recorded during a charging and / or discharging process, a state of charge is determined from it, a data set is created and the height of a peak is determined in the data set, and in which this is compared with the height of a peak in a data set preferably determined in the new state in order to estimate the degree of degradation of the battery cell.

[0004] Batteries are particularly susceptible to this process, known as lithium plating, at low operating temperatures and high charging currents, although lithium plating can also occur under other environmental and operating conditions.

[0005] Document US 2015 / 0147614A1 concerns a system and method for monitoring the condition and capacity of metal-ion batteries configured with a reference electrode. Document US 2013 / 0314050A1 concerns an automated charge preparation procedure for a variety of interconnected energy storage elements, and US 2013 / 0234648A1 concerns a charge control procedure for a secondary battery, such as a lithium-ion secondary battery. SUMMARY

[0006] The object of the present invention is to improve the aforementioned disadvantages in vehicles with traction batteries.

[0007] The problem is solved with a vehicle having the features of independent claims 1 and 5. Advantageous embodiments can be found in the dependent claims.

[0008] In various embodiments, a vehicle with a traction battery comprising at least one cell includes a control unit coupled to and programmed with the traction battery to provide closed-loop feedback control of the vehicle or the traction battery to reduce the difference between a measured value of a lithium plating indicator and a target or setpoint value of the plating indicator representing minimal or no lithium plating. Embodiments include controlling the battery charging rate, current supplied to the battery through regenerative braking, additional loads affecting the battery discharge current, and motor power. In one or more embodiments, a battery power versus temperature table is updated in response to the detection of lithium plating.Embodiments may further include updating an accumulated plating history based on battery power during charging when plating is detected.

[0009] Embodiments according to the present invention can offer one or more advantages. For example, closed-loop feedback control of a lithium plating indicator using one or more vehicle systems or components can reduce or eliminate plating to improve battery performance, capacity, and lifespan. Various embodiments employ program logic to perform closed-loop feedback control using existing battery and vehicle sensors, thus eliminating the need for additional hardware.

[0010] The advantages mentioned above, as well as further advantages and features relating to different embodiments, will be readily apparent to experts in the field based on the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a block diagram showing an electrically powered vehicle with a closed-loop control system of lithium plating according to a representative embodiment; Fig. Figure 2 is a graph of the cell voltage as a function of the SOC for battery cells without and with plating for use in a lithium plating parameter or indicator for closed-loop control according to a representative embodiment; Fig. Figure 3 is a graph of the ratio of cell voltage change rate to cell charge rate as a time function for battery cells without and with plating for use as a lithium plating indicator according to a representative embodiment; Fig. Figure 4 is a flowchart showing a calculation of one or more lithium plating indicators or parameters for use in closed-loop feedback control of lithium plating according to a representative embodiment; Fig. Figure 5 is a diagram showing the operation of a closed-loop feedback controller for controlling vehicle and / or battery operation based on a lithium plating indicator value according to a representative embodiment; and Fig. Figure 6 is a flowchart showing the operation of a vehicle or a closed-loop feedback control procedure of a plating indicator under the influence of vehicle and / or traction battery operating conditions. DETAILED EXECUTION

[0011] As requested, detailed embodiments are disclosed here. However, it should be understood that the disclosed embodiments are merely representative of the claimed subject matter and can be implemented in various and alternative forms. The figures are not necessarily to scale. Thus, some features may be exaggerated or minimized to show details of certain components. Specific structural and functional details disclosed here are not to be interpreted as limiting, but rather as a purely representative basis for conveying the diverse applications of the embodiments to those skilled in the art. As those skilled in the art will recognize, various features shown and described with respect to figures can be combined with features shown in one or more further figures to create embodiments that are not explicitly shown or described.The combinations of features shown provide representative embodiments for typical applications. However, for certain applications or implementations, different combinations and modifications of the features in accordance with the content of this disclosure may be desirable.

[0012] The embodiments of the present disclosure generally provide a plurality of circuits or other electrical devices. All references to the circuits and other electrical devices and the functionalities provided by each are not intended to be limited to only what is illustrated and described herein. While the various disclosed circuits or other electrical devices may be assigned specific designations, such designations are not intended to limit the functional scope of the circuits and other electrical devices. Such circuits and other electrical devices may be combined and / or separated in any way, based on which specific type of electrical implementation is desired.It is acknowledged that the circuits or other electrical devices disclosed herein may comprise a number of discrete passive and active components, such as resistors, capacitors, transistors, amplifiers, analog-to-digital converters (ADCs or A / D converters), microprocessors, integrated circuits, non-volatile memory devices (e.g., FLASH, random-access memory (RAM), read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or other suitable variants thereof), and software, which interact together to perform a process(s) disclosed herein.In addition, each or more of the electrical devices can be configured to execute a computer program contained in a non-volatile, computer-readable medium programmed to perform any number of the disclosed functions.

[0013] Fig. Figure 1 is a block diagram of a representative embodiment of an electrically powered vehicle with at least one controller programmed to provide closed-loop feedback control of a vehicle or traction battery in response to a lithium plating indicator value relative to a target value associated with minimal or no lithium plating. While this representative embodiment shows a plug-in hybrid vehicle with an internal combustion engine, those skilled in the field will recognize that the disclosed embodiments, which provide closed-loop feedback control based on a lithium plating indicator, can also be used in other types of electrically powered vehicles.The closed-loop feedback control systems and methods are, in representative embodiments, independent of the specific vehicle powertrain, although exceptions are obvious to those skilled in the field. For example, controlling a motor to reduce the current supplied to the traction battery would not be applicable to a battery-electric vehicle. Representative vehicle applications may include hybrid vehicles, electric vehicles, or other types of vehicles that have a battery susceptible to performance degradation associated with lithium plating.

[0014] In the Fig. In the representative implementation shown in Figure 1, a plug-in hybrid vehicle 112 can comprise one or more electric machines 114 mechanically connected to a transmission 116. The electric machines 114 can function as an electric motor or as a generator. In the case of hybrid vehicles, a transmission 116 is mechanically connected to an internal combustion engine 118. The transmission 116 is also mechanically connected to a drive shaft 120, which is mechanically connected to the wheels 122. This description also applies to a battery electric vehicle (BEV), in which the hybrid transmission 116 can be a transmission connected to an electric machine 114, and the engine 118 can be omitted, as already described. The electric machines 114 can provide acceleration and deceleration capabilities regardless of whether the engine 118 is operating or not.The electric machines 114 can also function as generators, providing a fuel-saving benefit by recovering energy that would normally be lost as heat in the friction braking system during regenerative braking. As described in more detail below, the motor 118 can be controlled to regulate the power supplied to the electric machines 114 via closed-loop feedback control to prevent a discrepancy between a target and a measured value of a lithium plating indicator. Similarly, regenerative braking can be controlled to modify the lithium plating indicator value and associated lithium plating processes.

[0015] In hybrid or electric vehicle applications, a traction battery or traction battery pack 124 stores energy in a plurality of individual battery cells connected to provide a desired voltage and charge capacity for the electric machines 114. In one embodiment, a battery pack 124 comprises an array of lithium-ion battery cells. Lithium plating (here also referred to as "plating") refers to the process by which metallic lithium is deposited on the negative electrodes or anodes of the battery cells and, depending on the specific structural properties of the deposited lithium, can have long-term consequences such as capacity loss, increased resistance, reduced efficiency, and in some cases, an internal short circuit. Plating can be reversed to some extent in a process called "stripping."Irreversible plating can lead to permanent damage to the cell anode. Therefore, various embodiments according to the present invention employ a vehicle or battery controller programmed to implement a closed-loop feedback control strategy based on a lithium plating indicator value. This strategy controls the vehicle and / or traction battery in response to a difference between a target indicator value and a measured / calculated indicator value, in order to reduce or eliminate lithium plating. Controlling the battery charge and discharge can be used to strip anodes with reversible plating and to reduce or eliminate additional plating. Battery cells are particularly susceptible to plating during charging at low temperatures, high states of charge (SOC), and high charge rates (high current).Thus, controlling the battery and / or the vehicle can include controlling the traction battery current to reduce or reverse (strip) lithium plating. Various strategies can be used to calculate a lithium plating indicator value for use by closed-loop feedback control, with representative strategies relating to [missing information]. Fig. 2 to 4 are shown and described.

[0016] The vehicle battery pack 124 typically provides a high-voltage DC output for a high-voltage bus 150, although voltage and current may vary depending on specific operating conditions and loads. The traction battery pack 124 is electrically connected to one or more external circuits 152, which may include, for example, power electronics or inverter circuits 126, a DC-DC conversion circuit 128, and / or a power converter module or circuit 132. One or more contactors may isolate the traction battery pack 124 from other components when open and connect the traction battery pack 124 to the other components when closed. The traction battery pack 124 may include various internal circuits for measuring and monitoring various operating parameters, including cell current and individual cell voltage.Parameters such as voltage, current and resistance for a battery cell or a group of battery cells (sometimes referred to as a block or component) can be monitored and / or controlled by the BECM 146.

[0017] In addition to providing energy for propulsion, the traction battery pack 124 can supply energy to other external circuits 152 connected to the high-voltage bus 150. The vehicle's power distribution system 112 can also include a DC-DC converter module or circuit 128 that converts the high-voltage DC output of the traction battery 124 into a low-voltage DC supply compatible with other vehicle loads that may be directly connected. Other external high-voltage circuits or loads, such as those for passenger compartment or component heating elements, can be directly connected to the high-voltage bus 50 without the use of a DC-DC converter module 128.

[0018] The vehicle 112 may also have an auxiliary battery 130 with a relatively low nominal voltage (e.g., 24V or 48V) and may be implemented using different battery chemical properties than the traction battery pack 124. The auxiliary battery 130 may also be referred to as a low-voltage battery, starter battery, or simply vehicle battery in various applications. The auxiliary battery 130 can be used to power various low-voltage components, controllers, modules, motors, actuators, sensors, etc., which are generally represented by electrical loads 160. One or more relays / voltage converters 168 can be used to power the electrical load(s) 160.In this embodiment, the relay / voltage converter 168 comprises a relay controlled by a relay input signal 170 provided by a vehicle control module (VCM) 172, which can further be used to directly or indirectly control the vehicle and / or the traction battery 124 using the battery energy control module (BECM) 146. As described in more detail below, one or more electrical components or accessories can be controlled by the VCM 172 and / or the BECM 146 to control lithium plating by controlling battery current.

[0019] The traction battery pack 124 can be charged by an external power source 136. The external power source 136 can include an electrical outlet connected to the power supply network. The external power source 136 can be connected to the vehicle electrical supply equipment (EVSE) 138. The EVSE 138 can provide circuitry and control for regulating and managing the energy transfer between the power source 136 and the vehicle 112. The external power source 136 can supply the EVSE 138 with direct current (DC) or alternating current (AC) power. The EVSE 138 can have a charging plug 140 for insertion into a charging port 134 of the vehicle 112. The charging port 134 can be electrically connected to a charging or on-board power conversion module 132. Alternatively, various components described as electrically connected can transfer power using wireless inductive coupling.As described in more detail below, the power conversion module 132 is another representative electrical device that can be controlled directly or indirectly to limit or reverse lithium plating by controlling the battery current. In some applications, the battery current can be reduced or stopped during charging, or conversely, the current can be reversed to supply current to the external power source 136 to reduce or reverse lithium plating.

[0020] The various in Fig. The components shown in Figure 1 can have one or more associated controllers, control modules, and / or processors, such as the VCM 172, to control the operation of the vehicle and the traction battery based on a lithium-plating indicator value. The controllers can communicate via a Serial Peripheral Interface (SPI) bus (e.g., Controller Area Network (CAN)) or via discrete conductors. Various operating parameters or variables can be transmitted or published using the CAN bus or other conductors for use by vehicle control modules or submodules when controlling the vehicle or vehicle components, such as the traction battery pack 124 or the electrical load(s) 160. One or more controllers can operate independently without communicating with one or more other controllers.The controllers can include a Battery Energy Control Module (BECM) 146 to control various charging and discharging functions, battery cell charge balancing, battery pack voltage measurements, individual battery cell voltage measurements, battery overcharge protection, determination of the end of battery life, closed-loop feedback control of lithium plating, battery current polarity or direction (charging and discharging), etc.

[0021] The controllers can include and / or communicate with various types of non-volatile, computer-readable storage media, including permanent and temporary storage devices for storing control logic, algorithms, programs, operating variables, and the like. In one embodiment, the BECM 146 can communicate with a memory for storing values ​​associated with desired battery cell idle voltage values, thresholds, or patterns. Similarly, the BECM 146 can communicate with a memory containing values ​​stored in lookup tables or arrays that are associated with the battery cell's internal resistance based on battery parameters such as temperature, state of charge (SOC), age, etc.In one embodiment, the BECM 146 communicates with a memory containing a lookup table for battery power versus temperature and modifies one or more values ​​in the lookup table in response to the detection of lithium plating. The BECM 146 can further communicate with a memory storing an accumulated plating history corresponding to the battery charging power supplied under lithium plating conditions to estimate battery lifetime.

[0022] Fig. Figure 2 is a graph of the cell voltage as a SOC function for battery cells with and without plating for calculating a lithium plating indicator value and for closed-loop feedback control of the indicator value according to a representative embodiment. The graph of Fig. 2 was generated using empirical data for representative lithium-ion cells that are in a battery pack in an electrically powered vehicle, such as the plug-in hybrid vehicle from Fig. 1. The data represented by line 210 correspond to the cell voltage during discharge over time for a normal lithium-ion cell with little or no plating. The data represented by lines 212 and 214 correspond to cell voltages during discharge over time for cells affected by lithium plating, the plating being confirmed by disassembling and examining visibly damaged anodes of the affected cells. Due to the chemical properties of lithium, when a battery cell is affected by plating as described above, the open-circuit voltage (OCV) of the battery cell is higher than that of a cell with little or no plating.

[0023] During discharge, reversibly affected lithium can be stripped off such that the OCV discharge curves versus SOC are the same for cells with and without plating. The low SOC section of the curves, generally designated by the reference numeral 216, can be used after the stripping process is complete to identify the SOC value of the cells with plating.

[0024] In various embodiments, the expected or normal battery OCV and / or the battery cell internal resistance for specific battery operating parameters, such as temperature, current, SOC, age, etc., can be stored in a memory that communicates with the BECM 146. The lithium plating indicator value can correspond to the difference between a measured OCV of at least one cell and the previously stored expected OCV under similar operating conditions. The measured OCV can be calculated based on a measured battery cell voltage, the current flow through the battery cell, and the battery cell internal resistance, as calculated or previously stored in a memory associated with the battery control system, as follows: OCV=V_battery−I*R_cell where OCV represents the battery cell open-circuit voltage (V), V_battery represents the measured battery cell voltage (V), I represents the current flowing through the battery cell (A), and R_cell represents the internal resistance of the battery cell (ohms). The lithium plating indicator value, which corresponds to the differential OCV, is then used for closed-loop feedback control of the lithium plating process. The plating indicator value can be determined as follows: Plating Indicator=OCVmeasured−OCVexpected

[0025] One or more control units communicating with the traction battery can be programmed to provide closed-loop feedback control to reduce / eliminate a difference between a target value for the plating indicator and the measured value based on the differential OCV voltage, for example to control the traction battery and / or the vehicle, reduce the charging current, or warm the battery with an external heating unit or battery internal resistance.

[0026] Fig. Figure 3 is a graph of the ratio of a cell voltage change rate to a cell charge rate as a function of time for battery cells with and without plating, for use as a plating indicator value for closed-loop feedback control of lithium plating according to a representative embodiment. Data represented by line 310 correspond to ratios for a battery cell with little or no lithium plating, while data represented by lines 312 and 314 correspond to ratios for battery cells exhibiting lithium plating. Line 320 represents a representative threshold that can be used to compare the ratios for detecting lithium plating, with lithium plating being detected as a response to exceeding the threshold by the calculated ratio, as shown at Figure 330 for line 312 and at Figure 340 for line 314.Lithium plating can also be detected through system identification techniques to identify an associated pattern related to lithium plating.

[0027] Experts in the field will recognize that the specified threshold can vary based on battery and / or environmental operating parameters or conditions, can be estimated online and stored in a memory configured as a lookup table, or can be calculated based on a formula or equation using empirical data to mathematically express the threshold. Similarly, the pattern generated by the data from one or more cells over time can be compared to a corresponding expected or desired pattern for a cell without plating using a mathematical or statistical parameter, such as through correlation, to detect plating. Likewise, other ratios can be calculated and used to detect plating based on empirical data associated with cells exhibiting plating.The target value for the plating indicator for use in closed-loop feedback control may be lower than the plating threshold when attempting to prevent plating by having the closed-loop feedback control try to keep the plating indicator value below the threshold associated with plating.

[0028] As is generally the case in Fig. As shown in Figure 3, the ratio of the cell voltage change rate or differential voltage versus the cell charge rate (which may be indicated, for example, by cell current) will exhibit a clear transition when the deposited lithium has ceased to participate in the reaction during the process. Since the cell voltage change rate versus cell charge rate ratio, as represented by lines 310, 312, and 314, is robust compared to a time-based ratio, it is also robust to various battery operating conditions. Thus, lithium plating can be controlled using the cell voltage change rate versus cell charge rate ratio to prevent the ratio from exceeding the associated threshold that indicates lithium plating, or to limit this as much as possible.Lithium plating can also be controlled by updating the battery power lookup table over temperature to reduce battery power at the plating temperature to prevent lithium plating during subsequent battery operation.

[0029] As previously mentioned regarding Fig. As described in section 2, due to the chemical properties of lithium and the carbon anode of each battery cell, if a battery has plating, the cell OCV will be higher than a normal or nominal battery open-circuit voltage without plating. When the lithium stops participating in the reaction, the cell OCV returns to a normal OCV, as generally indicated at 350. In various applications, the battery cell voltage within the battery pack is measured for individual cells or groups or components of cells, so that the differential voltage for a particular cell or group of cells, dV / dt, can be calculated. The cell charge rate or cell charge change rate can be represented by the current cell current (I) as follows: dQdt=I

[0030] The ratio of the cell voltage change rate to the cell charge rate can be calculated as a plating indicator value by a vehicle or battery control unit as follows: Ratio(Plating indicator value)=dV_batterydQ=(dV_batterydt) / (dQdt)=(dVdt) / I

[0031] Where Q represents the accumulated battery cell charge (Coulomb), V_battery represents the measured battery cell voltage (V), and I represents the current flowing through the battery cell (A). Filters can be applied before and / or after the differential calculation to reduce or eliminate signal noise.

[0032] Fig. Figure 4 is a flowchart showing the calculation of one or more lithium plating indicators or parameters for use in closed-circuit feedback control of lithium plating according to a representative embodiment. The process(s), systems, methods, heuristics, etc., described herein may be described as occurring in an ordered sequence, although these processes could be carried out by performing the described steps in a different order than that described or shown. It is to be understood that certain steps could be performed simultaneously, that further steps could be added, or that certain steps described herein could be omitted, which would nevertheless be consistent with the teachings of this disclosure and encompassed by the claimed subject matter.The descriptions of methods or processes are provided to illustrate certain embodiments and are to be understood as representative of one of many variations and not limited to those shown or described.

[0033] As is generally understood by experts in the field, the system or procedure can be implemented by a computer algorithm, a machine-executable code, or software instructions programmed on one or more suitable programmable devices associated with the vehicle, e.g., the VCM 172, the BECM 146, another control unit, or a combination thereof.

[0034] The operation of the system or method 400 comprises storing expected or desired values ​​for various battery operating parameters, as in 410, in a non-volatile, computer-readable medium or memory for subsequent use in controlling lithium plating. As previously described, battery parameter values ​​may include expected or desired values ​​for the open-circuit voltage of a representative cell or groups of cells corresponding to current battery and / or environmental operating conditions. The internal resistance of battery cells may also be stored for subsequent use in calculating the OCV of a cell based on a measured cell voltage. Stored values ​​may further include a lookup table for battery performance versus temperature and a counter for accumulated plating history.Current operating conditions are measured or otherwise determined for various battery parameters as shown in block 412. Representative parameters may include cell voltage, cell current, state of charge (SOC), and temperature, as shown in 414.

[0035] One or more lithium plating parameters or indicators are determined as shown in block 416. As previously described, lithium plating parameters or indicators may be based on a differential cell voltage 418, which may, for example, include a differential OCV. Alternatively, the measured OCV may be calculated using measured cell current, cell voltage, and internal resistance, as shown in 420. A differential voltage ratio may be calculated as shown in 422 and may include a ratio of the differential voltage or voltage change to the cell charge rate, as shown in 426. One or more lithium plating indicator values / patterns may be provided to a closed-loop feedback control, as shown in 430.

[0036] Fig. Figure 5 is a diagram illustrating the operation of a feedback control system to the control vehicle and / or battery operation based on a lithium plating indicator value according to a representative embodiment. The control system 500 generally represents a simplified closed-loop proportional-integral (PI) feedback control system. Other closed-loop strategies can be used to control lithium plating conditions in accordance with the teachings of this disclosure and include feedback, feedforward, and hybrid controls using any combination of proportional, integral, and derivative control functions or equations. The control system 500 determines a plating indicator setpoint or target value as shown in Figure 510.The setpoint or target value can be based on current vehicle, battery, and / or environmental operating conditions and will vary depending on the specific plating indicator. The selected plating indicator can vary based on the current operating mode or through application and implementation. For example, in one embodiment, only a single plating indicator is provided. Other embodiments may include multiple plating indicators, with an arbitration strategy selecting a specific plating indicator for use by the closed-loop feedback control.

[0037] A difference or error value is calculated by a summer 520 based on a difference between the indicator setpoint or target value and a feedback signal corresponding to a calculated plating indicator value, as shown by block 530, and offset by a time delay 532. The corresponding difference value 536 is applied to a proportional term 540 and an integral term 542, and the resulting values ​​are combined in the summer 550. The resulting value can be used to modify battery conditions, as shown in 560, to reduce the difference value 536 towards zero. The proportional term 540 and the integral term 542 can be adjusted to provide desired system performance.

[0038] Block 560 generally indicates a direct or indirect modification of battery conditions by controlling one or more battery or vehicle parameters or components to reduce or reverse lithium plating in the battery. For example, in electric hybrid vehicles and electric plug-in hybrid vehicles with an internal combustion engine, using an external heating unit or by discharging the battery to utilize the battery's internal resistance to increase the battery temperature, modifying battery conditions may involve reducing the battery charging rate or current to the permitted minimum charge level, which may vary based on current operating conditions.During vehicle operation, reducing battery current may involve reducing or stopping the current provided by regenerative braking, or changing an engine operating point or mode from maximum efficiency to minimum battery charging power.

[0039] In various embodiments, changing operating conditions, as shown by block 560, can include heating the battery block 124 by controlling one or more electrical accessories to provide power from the battery instead of from the electric machine(s) operating in generator mode. This can also include reducing the additional power provided by the engine, thus increasing the electrical load on the battery and the corresponding current to generate more heat. Increasing the additional electrical load can include operating a battery block heating element or increasing the heating element load to a maximum load to rapidly heat the battery block.

[0040] Fig. Figure 6 is a flowchart illustrating the operation of a representative embodiment of a vehicle or a closed-loop feedback control method for a plating indicator influenced by vehicle and / or traction battery operating conditions. In the representative embodiment shown in Figure 6, the vehicle is equipped with a plateing indicator that is driven by vehicle and / or traction battery operating conditions. Fig. As shown in Figure 6, the control strategy 600 involves retrieving a plating indicator setpoint based on current operating conditions, as shown in Figure 610. Current operating conditions can include vehicle, battery, and / or environmental conditions such as temperature, battery current, battery block voltage, battery cell voltage, state of charge (SOC), battery age, and accumulated battery plating history. In applications using more than one plating indicator, a setpoint or target value for each plating indicator can be derived from previously stored values.

[0041] A current value for each plating indicator is calculated as shown in 612. As previously described, representative plating indicators can include, for example, a differential voltage or a differential voltage-to-charge-rate ratio. One or more indicator values ​​are used to detect plating, as shown in 614. In one embodiment, plating can be detected by comparing an indicator to an appropriate threshold. In another embodiment, the closed-loop feedback control can determine lithium plating when the difference or error between the target indicator value and the current indicator value exceeds a threshold. If plating is not detected, the control continues to update the target value and the current value by returning to block 610.

[0042] When plating is detected, as shown in Block 614, battery power can be updated as a function of the temperature lookup table using current operating conditions to reduce the likelihood of plating conditions occurring during subsequent operation. For example, power supplied to the battery to charge it may be subject to a current limit as a temperature function based on values ​​in the lookup table. If plating is detected, these values ​​can be modified to reduce the power limit for a specific temperature at which plating was previously detected.

[0043] A count for accumulated plating history can be updated in response to the detection of plating conditions, as shown in Figure 618. For example, the count, or other historical value, can be updated to record the total amount of power or ampere-hours (Ah) for which the battery has been subjected to lithium plating. The accumulated lithium plating Ah can be used to adjust the battery life estimate. Alternatively, or in combination with this, more aggressive mitigation strategies can be employed as the accumulated plating count increases or when it exceeds one or more associated thresholds.

[0044] Block 620 shows the control of battery current to reduce the lithium plating indicator differential or error value to provide closed-loop feedback control. As previously described, this can involve controlling a motor operating point to decrease the charging current supplied to the battery, as shown in 630; controlling regenerative braking to decrease the charging current supplied to the battery, as shown in 632; or controlling additional loads to increase the discharge current and raise the battery temperature, as shown in 634. The battery temperature can be raised indirectly by controlling accessories to increase the electrical load and current supplied by the battery, and / or directly by controlling a battery heating unit.

[0045] As experts in the field will recognize, the described representative embodiments can provide one or more advantages, such as controlling a traction battery to reduce or reverse lithium plating based on closed-loop feedback control of a lithium plating indicator. Non-destructive online lithium plating indicators are provided to mitigate irreversible lithium plating and its associated performance degradation, thereby increasing battery life and capacity.

[0046] Although various embodiments are described above, these embodiments are not intended to describe all possible forms encompassed by the claims. The terms used in the description are descriptive and not limiting, and it is pointed out that various modifications can be made without altering the essence and scope of protection of the disclosure. Furthermore, the features of different embodiments can be combined to form further embodiments of the disclosure that may not be expressly described or illustrated.Although various embodiments have been described as advantageous or preferred over other embodiments or implementations in the prior art with respect to one or more desired features, those skilled in the art will recognize that one or more functions or features can be modified to achieve desired general system properties that depend on the specific applications and implementations. These properties include, but are not limited to, cost, strength, service life, life cycle costs, marketability, appearance, packaging, size, ease of maintenance, weight, manufacturability, ease of assembly, etc.Embodiments that are described as less desirable than other embodiments or implementations in the prior art with respect to one or more features are not necessarily outside the scope of protection of the disclosure and may be desirable for certain applications.

Claims

[1] Vehicle (112) with a traction battery (124) comprising at least one cell, comprising the following: an internal combustion engine (118); and a control unit (146, 172) that is coupled to and programmed with the traction battery (124) to • a traction battery current, • an operating point of the internal combustion engine (118) and • a previously saved lookup table of battery charging power versus temperature to change in response to a difference between a lithium plating parameter target value and a current lithium plating parameter value in order to reduce the difference, wherein the lithium plating parameter is based on a ratio of a differential voltage of the at least one cell as a time function to a cell charging rate of the at least one cell; characterized by , that the controller (146, 172) is programmed to identify a lithium-plated cell based on a ratio between an open-circuit voltage and a traction battery state of charge for state-of-charge values ​​below a threshold after the traction battery (124) has been discharged for a predetermined time to allow complete lithium stripping. [2] Vehicle (112) according to claim 1, wherein the control (146, 172) changes an operating point to reduce a battery charging current. [3] Vehicle (112) according to claim 1, wherein the control (146, 172) reduces a regenerative braking current to change a battery current. [4] Vehicle (112) according to claim 1, wherein the control unit (146, 172) changes a stored battery power limit associated with a current battery temperature in response to the difference rising above a threshold. [5] Vehicle (112) with a traction battery (124) comprising at least one cell, comprising the following: an internal combustion engine (118); and a control unit (146, 172) that is coupled to and programmed with the traction battery (124) to • a traction battery current, • an operating point of the internal combustion engine (118) and • a previously saved lookup table of battery charging power versus temperature to change in response to a difference between a lithium plating parameter target value and a current lithium plating parameter value in order to reduce the difference, wherein the lithium plating parameter is based on a ratio of a differential voltage of the at least one cell as a time function to a cell charge rate of the at least one cell, characterized by , that The control system tracks accumulated traction battery power during battery charging if the difference exceeds a certain threshold.

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