Functional assessment and redundancy of a battery pack voltage measurement of an electric or hybrid vehicle

Abstract

Vehicle (12) comprising: a traction battery pack (24) having a high voltage bus (50) and a plurality of individual battery cells (220), the traction battery pack (24) having a plurality of internal circuits providing a plurality of corresponding independent internal measurements of a voltage of the traction battery pack (24); a plurality of external circuits external to the traction battery pack (24) and coupled to the high voltage bus (50) and providing a plurality of corresponding independent external measurements of the voltage of the traction battery pack (24); an electric machine (14) operated by the traction battery pack (24) via one of the plurality of external circuits to propel the vehicle (12); and a controller in communication with the plurality of internal circuits and the plurality of external circuits and programmed to communicate a battery pack voltage to a vehicle network (230), wherein the battery pack voltage corresponds to a first independent internal measurement in response to a voltage difference among all of the independent internal measurements being less than a threshold, a second independent internal measurement in response to the voltage difference exceeding the threshold, and a statistical measure of the independent internal and external measurements in response to any one of the internal measurements being invalid.

Description

TECHNICAL FIELD

[0001] Aspects of the present disclosure relate to systems and methods for ensuring proper operation and backup redundancy of battery pack voltage measurements for electrified vehicles such as electric and hybrid vehicles. BACKGROUND

[0002] Electrified vehicles such as electric and hybrid vehicles have a battery pack, also known as a traction battery or traction battery pack, and an electric machine to power the vehicle. Hybrid vehicles have an internal combustion engine, which can be used to charge the battery pack and / or power the vehicle in combination with the electric machine. The traction battery pack has a plurality of individual battery cells connected together to provide power to the vehicle. A battery management system (BMS) in electrified vehicles measures the voltage of the traction battery pack as well as individual cell voltages. Various high-voltage (HV) modules or circuits can be powered by the battery pack and communicate with the BMS via a vehicle network. The battery pack voltage is often used in many aspects of vehicle and battery control, such as:in estimating battery online power capacity, cell balancing, battery overcharge and deep discharge protection, determining engine start availability (in hybrid vehicles), battery lifetime assessment, current dissipation measurement, contactor status determination, battery charging, etc.

[0003] US 2013 / 0 119 941 A1 is known from the prior art. This describes a method for measuring voltages using various analog-to-digital converters.

[0004] EP 2 428 809 A2 describes a battery controller that can detect an abnormal voltage condition.

[0005] A vehicle having the features of claim 1 is provided.

[0006] One or more functional industry specifications or standards may apply to specific functions of a BMS or related components and circuits. Vehicles may incorporate self-diagnostics and, in some cases, redundancy for various BMS-related components or functions to meet a specific standard or achieve a specific rating published by a standards committee or rating agency. SUMMARY

[0007] In one or more embodiments, a vehicle may include a traction battery pack having a high-voltage bus and a plurality of individual battery cells, the traction battery pack having a plurality of internal circuits providing a plurality of corresponding independent internal measurements of a traction battery pack voltage. The vehicle may also include a plurality of external circuits external to the traction battery pack and coupled to the high-voltage bus, providing a plurality of corresponding independent external measurements of the traction battery pack voltage. An electric machine powered by the traction battery pack via one of the plurality of external circuits to propel the vehicle communicates with a controller that communicates with the plurality of internal circuits and the plurality of external circuits and is programmed to communicate a battery pack voltage to a vehicle network.The battery pack voltage corresponds to a first independent internal measurement in response to a voltage difference among all independent internal measurements being less than a threshold, a second independent internal measurement in response to the voltage difference exceeding the threshold, and a statistical measure of the independent internal and external measurements in response to any one of the internal measurements being invalid. The external circuitry may include an inverter circuit, an electric air conditioning (eAC) circuit, and a DC / DC converter circuit that can convey or transmit associated independent external voltage measurements. The internal circuitry may include a battery pack voltage measurement circuit that measures the voltage of a traction battery pack across the plurality of individual battery cells.In one embodiment, the internal circuits include a plurality of integrated battery monitoring circuits, each measuring a voltage across a corresponding group of the individual battery cells.

[0008] Various embodiments may include a vehicle having a battery with internal circuitry that measures a battery pack voltage and individual cell voltages, an electric machine powered by the battery to power the vehicle via an external circuitry that measures the battery pack voltage, and a processor programmed to communicate the battery pack voltage based on a first internal circuit voltage in response to a voltage difference among the internal circuitry being less than a threshold and based on the individual cell voltages.The internal circuitry may include a positive-leg leakage detection circuit that measures the traction battery pack voltage from one of the most positive of the individual battery cells to the vehicle ground, and a negative-leg leakage detection circuit that measures the traction battery pack voltage from one of the most negative of the individual battery cells to the vehicle ground. The vehicle may also include a second external circuit that measures the battery pack voltage, wherein the processor is further programmed to communicate the battery pack voltage based on a statistical measure of central tendency of the battery pack voltage measurements from the internal circuitry and the external circuitry.The vehicle processor may be programmed to store a diagnostic code in response to a voltage difference among the external circuits exceeding a second threshold, and may be programmed to communicate the battery pack voltage based on a median of the battery pack voltage measurements from the internal circuits and the external circuits in response to a voltage difference among the external circuits being below the second threshold.

[0009] One or more embodiments include a control method for an electric vehicle having a traction battery coupled to an electric machine, wherein a vehicle processor outputs a battery pack voltage to a vehicle network based on internal voltage measurements in response to a voltage difference among the internal measurements being less than a threshold, and outputs the battery pack voltage based on a static function of the internal measurements and otherwise communicated voltage measurements from external circuitry. The control method may include using a statistical measure of central tendency, such as a median, and / or summing internal measurements associated with individual battery cells.In one embodiment, the statistical function includes a median value of the internal voltage measurements and the transmitted voltage measurements from the external circuits in response to a voltage difference of the transmitted voltage measurements from the external circuits being below an associated threshold.

[0010] Embodiments according to the present disclosure may provide one or more advantages. For example, embodiments according to the present disclosure may provide a functional assessment of the validity of battery pack voltage measurements from internal and / or external circuitry. Additionally, embodiments may provide a reliable indication of battery pack voltage if the functional assessment indicates one or more of the internal or external circuits is not functioning as expected. Various embodiments provide self-diagnostics that utilize the functional assessments described herein in combination with redundancy to provide a backup battery voltage measurement for use in controlling the battery and / or the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a representative electric vehicle having a vehicle processor or controller that controls the battery and / or the vehicle using a communicated battery pack voltage based on a functional assessment of internal and external voltage measurements, in accordance with embodiments of the present disclosure; Fig. 2 is a block diagram illustrating a representative embodiment of a vehicle with representative internal and external voltage measurement circuits or modules according to embodiments of the present disclosure; Fig. 3 is a block diagram illustrating representative internal circuitry including battery cell monitoring integrated circuits (ICs) for a traction battery pack for use in functional assessment and battery pack voltage redundancy according to embodiments of the present disclosure; Fig. 4 is a block diagram illustrating representative internal circuits including leakage detection circuits for use in functional evaluation and battery pack voltage redundancy according to embodiments of the present disclosure; and Fig. 5 is a block diagram illustrating the operation of a system or method for controlling an electric vehicle that includes outputting or communicating a battery pack voltage based on voltage measurements from internal and / or external circuitry, according to embodiments of the present disclosure. DETAILED DESCRIPTION

[0011] As required, detailed embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely representative of the claimed subject matter and may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Specific structural and functional details disclosed herein are, therefore, not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments.It will be appreciated by those of ordinary skill in the art that various features illustrated and described with reference to any of the figures may be combined with features illustrated in one or more other figures to create embodiments not explicitly illustrated or described. The illustrated combinations of features provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for specific applications or implementations.

[0012] The embodiments of the present disclosure generally provide a plurality of internal and external circuits or other electrical devices. Any references to the circuits or other electrical devices and the functionality provided by each are not intended to be limited to include only what is illustrated and described herein. Although specific labels may be assigned to the various circuits or other electrical devices disclosed, these labels are not intended to limit the scope of functionality for the circuits and other electrical devices. Such circuits and other electrical devices may be combined and / or separated in any manner based on the particular type of electrical implementation desired.It is recognized that any circuit or other electrical device disclosed herein may include any number of 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 variations thereof), and software that cooperate with one another to perform operation(s) disclosed herein.Additionally, any one or more of the electrical devices may be configured to execute a computer program embodied in a non-transitory computer-readable storage medium having instructions for programming a computer or controller to perform any number of the functions as disclosed. As used herein, internal circuits generally refer to circuits having components within the battery pack, and external circuits generally refer to circuits or modules powered by the battery pack but located inside the vehicle and external to the battery pack.

[0013] Fig. Figure 1 is a block diagram of a representative electric vehicle having a vehicle processor or controller that controls the vehicle using a communicated battery pack voltage based on voltage measurements from internal and / or external battery circuits or modules, according to embodiments of the present disclosure. While a plug-in hybrid vehicle having an internal combustion engine is illustrated in this representative embodiment, those of ordinary skill in the art will recognize that the disclosed embodiments may also be implemented in a conventional hybrid vehicle, an electric vehicle, or other type of vehicle having a battery pack with individual battery cells used to power the vehicle under at least some operating conditions.

[0014] A plug-in hybrid electric vehicle 12 may include one or more electric machines 14 mechanically connected to a hybrid transmission 16. The electric machines 14 may be capable of operating as a motor or as a generator. For hybrid vehicles, a transmission 16 is mechanically connected to an internal combustion engine 18. The transmission 16 is also mechanically connected to a driveshaft 20, which is mechanically connected to the wheels 22. The description herein is equally applicable to a battery electric vehicle (BEV), where the hybrid transmission 16 may be a transmission connected to an electric machine 14, and the internal combustion engine 18 may not be present, as described above. The electric machines 14 may provide propulsion and braking functionality whether the internal combustion engine 18 is operating or not.The electric machines 14 also function as generators and can provide fuel economy benefits by recovering energy that would normally be lost as heat in the friction braking system. The electric machines 14 can also reduce vehicle emissions by allowing the internal combustion engine 18 to operate at more efficient speeds and by allowing the hybrid electric vehicle 12 to operate in electric mode with the internal combustion engine 18 off under certain circumstances. Similar benefits can be obtained with an electric vehicle that does not have the internal combustion engine 18.

[0015] A traction battery or traction battery pack 24 stores energy in a plurality of individual interconnected battery cells that can be used by the electric machines 14. The vehicle battery pack 24 typically provides a high-voltage DC output to a high-voltage bus 50, although the voltage and current may vary depending on the particular operating conditions and loads. The traction battery pack 24 is electrically connected to one or more external circuits 52, including, for example, a power electronics or inverter circuit 26, an electric air conditioning (eAC) circuit 27, a DC / DC converter circuit 28, and / or a power conversion module or circuit 32. One or more contactors (preferably in Fig. 2-3) may isolate the traction battery pack 24 from other components when open and connect the traction battery pack 24 to other components when closed. As described in more detail herein, various internal voltage sensing circuits may provide independent battery pack voltage measurements depending on which contactors are open or closed. The power electronics or inverter circuit 26 is also electrically connected to the electric machines 14 and provides the ability to transfer power in two directions between the traction battery pack 24 and the electric machines 14. For example, a typical traction battery pack 24 may provide a DC voltage, while the electric machines 14 may require three-phase AC voltage or current to function efficiently.The power electronics or inverter circuit 26 can convert the DC voltage into a three-phase AC current, which is supplied to the electric machines 14. In a regenerative mode, the power electronics or inverter circuit 26 can convert the three-phase AC current from the electric machines 14, which act as generators, into the DC voltage compatible with the traction battery pack 24.

[0016] In addition to providing power for propulsion, the traction battery pack 24 may provide power to other external circuits 52 connected to the high-voltage bus 50, as described above. The vehicle 12 may include a compressor (not shown) driven by the traction battery 24 via an associated electric air conditioning (eAC) module or circuit 27 to condition the vehicle interior and / or the traction battery 24. The vehicle 12 may also include a DC / DC converter module or circuit 28 that converts the high-voltage DC output of the traction battery 24 to a low-voltage DC supply compatible with other vehicle loads. Other external high-voltage circuits or loads, such as those for interior or component heaters, may be connected directly to the high-voltage bus 50 without the use of a DC / DC converter module 28.The low-voltage systems may be electrically connected to an auxiliary battery 30 (e.g., a 12 V, 24 V, or 48 V battery).

[0017] Embodiments of this disclosure may include vehicles such as vehicle 12, which may be a hybrid or range-extender hybrid or an electric vehicle, in which traction battery pack 24 may be charged from an external power source 36. External power source 36 may be a connection to an electrical port connected to the utility grid. External power source 36 may be electrically connected to Electric Vehicle Supply Equipment (EVSE) 38. EVSE 38 may provide circuitry and controls for regulating and managing the transfer of electrical energy between power source 36 and vehicle 12. External power source 36 may provide DC or AC electrical power to EVSE 38. EVSE 38 may include a charging connector 40 for plugging into a charging port 34 of vehicle 12.The charging port 34 may be any type of connector configured to transfer power from the EVSE 38 to the vehicle 12. The charging port 34 may be electrically connected to a charger or an on-board power conversion module 32. The power conversion module 32 may condition the power supplied from the EVSE 38 to provide the proper voltage and current levels to the traction battery 24. The power conversion module 32 may be connected to the EVSE 38 to coordinate the delivery of power to the vehicle 12. The EVSE connector 40 may have pins that mate with corresponding recesses of the charging port 34. Alternatively, various components described as being electrically connected may transfer power using inductive coupling.

[0018] The various components used in Fig. 1 may include one or more associated controllers within the internal or external circuitry, as well as one or more other controllers or processors to control and monitor the operation of the components. The controllers may communicate via a Serial Peripheral Interface (SPI) bus (e.g., Controller Area Network (CAN)) or via discrete conductors. As described in more detail below, various operating parameters may be sent or communicated using the CAN or other conductors for use by vehicle control modules or sub-modules in controlling the vehicle or vehicle components such as the traction battery pack 24. One or more controllers may operate independently without communication with one or more other controllers. As described with reference to Fig. 2-5, one of the controls may be implemented by a BECM (Battery Energy Control Module) module 46 to control various charging and discharging functions, battery cell charge balancing, battery pack voltage measurements, individual battery cell voltage measurements, battery overcharge protection, battery overdischarge protection, battery life determination, etc. In one embodiment, the BECM 46 is programmed to communicate a battery pack voltage based on a first internal circuit voltage in response to a voltage difference among the internal circuits being less than a threshold and based on the individual cell voltages for use in controlling the traction battery pack 24 and / or vehicle 12.The BECM 46 may be disposed within the traction battery pack 24 and may communicate with various types of non-transitory computer-readable storage media, including persistent and temporary storage devices, to store battery voltage measurements and related statistical measures of central tendency, which may include a mean, median, mode, etc., as well as various other data or mathematical results such as a sum of voltage values, difference values, integrals, differentials, etc.

[0019] Vehicle traction battery packs can be constructed using various physical arrangements or architectures and various chemical formulations. Typical battery pack chemistries include lead acid, nickel metal hydride (NIMH), or lithium-ion. Fig. Figure 2 illustrates a typical traction battery pack 24 in a simple series configuration of multiple individual battery cells, generally shown at 220 and described with reference to Fig. 3. Battery packs may be composed of any number of individual battery cells connected in series, parallel, or a combination thereof. As described above, a typical system may include one or more controllers, such as the BECM 46, communicating over a vehicle network 230 via a communication link 232 to monitor and control various functions of the traction battery pack 24 and vehicle 12. The BECM 46 and / or other controllers or control modules may monitor a variety of battery pack bulk properties, such as battery pack current, battery pack voltage across all individual battery cells 220, battery pack temperature, and properties associated with individual battery cells 220.Each controller or control module may include non-volatile memory so that data may be retained when the controller is in an off condition for use after a subsequent key-on event, or may transfer data over a vehicle network 230 for storage from another controller with associated non-volatile memory.The controller(s) may include non-transitory computer-readable memory containing instructions for programming the controller(s) or associated processor(s) to control the battery pack 24 and / or the vehicle 12, the instructions for outputting, by a vehicle processor, a battery pack voltage to the vehicle network 230 based on internal voltage measurements within the traction battery pack 24 in response to a voltage difference among the internal measurements being less than a threshold, and for outputting the battery pack voltage based on a statistical measure or function of the internal measurements and otherwise communicated voltage measurements from external circuitry 52, as described with reference to FIG. Fig. 5 described in more detail.

[0020] With further reference to Fig. 1 and Fig. 2, the BECM 46 performs many monitoring and control functions for the traction battery pack 24. For example, the BECM 46 monitors the traction battery cell string 220 and controls the operation of a positive main contactor 236 and a negative main contactor 238. The BECM 46 communicates with one or more external high-voltage modules or circuits 52 via communication links 232 to the vehicle network 230 or through another communication bus such as an SPI bus. In Fig. 2 only one external high voltage module / circuit 52 is shown, which includes, for example, the inverter circuit 26, the eAC circuit 27, the DC / DC converter circuit 28 (all of which are Fig. 1) as well as any other external circuits or modules on the high voltage bus 50 that can provide an independent measurement of the battery pack voltage and communicate the voltage value on a vehicle network 230 or otherwise communicate the measurement to the BECM 46 or other controller for use in communicating or outputting a battery pack voltage as described herein.

[0021] In various embodiments, external modules or circuits 52 include circuits that measure the voltage between the VCONT_POS node 250 and the VCONT_NEG node 252. This voltage may be referred to as the DC link voltage or, alternatively, the high-voltage bus voltage of the electrified vehicle 12. One or more of the external modules or circuits 52 measure this DC link voltage and transmit the number as a message on the vehicle network 230. The DC link analog voltage may be measured by any suitable circuit or device and digitized in an associated controller or microprocessor for each of the external circuits 52 and translated into a corresponding message for the vehicle network 230, which in one embodiment is implemented by a CAN.In various embodiments, the network or CAN message containing the external measurement of the DC link voltage from the inverter circuit 26 includes a header or identifier INV_PACKV_MEAS. Similarly, the CAN message containing the independent external measurement of the DC link voltage determined by the DC / DC converter 28 includes a header or identifier DCDC_PACKV_MEAS, and the CAN message containing the independent external measurement of the DC link voltage determined by the eAC 27 includes a header or identifier EAC_PACKV_MEAS.

[0022] As in Fig. 2, the VCONT_POS node or pin 250 connects the positive (+) high voltage or DC link bus node to the BECM module 46. Alternatively, the BECM 46 may be described as having a VCONT_POS pin 250. The VCONT_POS node or pin 250 is connected to internal circuitry in the traction battery pack 24 and the BECM 46, as shown in the upper right portion of Fig. 4 shown (DIV1).

[0023] As in Fig. 2, the positive main contactor 236 and the negative main contactor 238 must be closed for the battery pack voltage of the traction battery 24 to appear on the DC link or high voltage bus 50. If either the positive main contactor 236 or the negative main contactor 238 is open, the DC link voltage eventually drops to zero volts. However, if the contactors 236, 238 are closed, the DC link voltage is essentially the same as the battery pack voltage of the traction battery pack 24 because the voltage is dropped by the contactors 236, 238 and the associated high voltage wiring is small. Accordingly, when the contactors 236, 238 are closed, the DC link voltage matches the battery pack voltage of the traction battery 24. So if the VCONT_POS node / pin 250 is configured to set the voltage of the positive DC connection (+) with respect to the VBOT node ( Fig. 4) to measure which is the negative node or terminal of cell string 220 (also referred to as the most negative individual battery cell), then the voltage at VCONT_POS 250 measures the battery pack voltage across the individual cells of cell string 220. Under the same operating conditions (contactors 236 and 238 closed), the DC link voltage or the voltage of the high voltage bus that drives external modules or circuitry 52 is at the same voltage as the traction battery cell string 220. Therefore, CAN messages communicated by the external circuitry in accordance with independent external measurements identified by INV_PACKV_MEAS, DCDC_PACKV_MEAS, and EAC_PACKV_MEAS provide voltage measurements that are substantially the same as the cell string 220 voltage.

[0024] Fig. 3 is a block diagram illustrating representative internal circuitry including integrated circuits (ICs) for battery cell monitoring for a traction battery pack for use in functional evaluation and battery pack voltage redundancy according to embodiments of the present disclosure. Cell string 220 includes strings of connected cells 2201, 2202, ... 220 mm , where mm is the total number of cells. In this arrangement, cell 2201 is the most negative cell and 220 mm is the most positive cell. A group, block, or module of cells may have an associated BMIC (Battery Monitor Integrated Circuit) circuit 310, 312. In many applications, a BMIC accommodates only a relatively small number of channels, such as 6 or 12, assigned to respective cells to provide individual cell voltages. Therefore, a number of BMICs are included in a typical battery pack.

[0025] As briefly explained above, the voltage of each cell in the cell string 220 is individually measured by an associated BMIC 320, 312. This is achieved using a pair of voltage sense wires that connect each cell to associated input pins such as V0 and V1 on the BMIC 310. The measured battery pack voltage, represented by PACKV, is measured or sampled at a sampling time instant represented by T s The measurements of the individual cells obtained by the BMICs 310, 312 can be synchronized in time such that the voltage of all cells is within a short time period or a short time window (e.g., 100 µS) around the sampling time T s . is measured. In addition, the BMIC 310, 312 may include a feature that sums the voltages of connected cells and outputs a corresponding device voltage. As in the representative embodiment of Fig. As shown in Figure 3, BMICs 310, 312 each read six channels, providing individual cell voltages for six corresponding cells. The associated device voltage is provided in response to a "device read" input 320, 322 associated with each BMIC 310, 312, respectively, and connected as shown.

[0026] As in Fig. 3, the BMIC 310 has a device read input 320 connected to the same node as the V6 input. However, the V6 input typically measures the cell voltage of the cell connected between pins V5 and V6 on the BMIC 310. The device read input 320 reads the voltage with respect to the V ss pin on the BMIC 320. The device read input captures the voltage of the group or device of, for example, six cells associated with the BMIC 310. In the representative embodiment of Fig. 3, a low-voltage (LV) master microcontroller with control software 330 communicates with each BMIC 310, 312, as generally represented by communication links 340, and controls the contactors 236, 238. Accordingly, the BMIC 310, 312, in combination with the cell string 220 and the LV master microcontroller 330, provide internal circuitry that provides independent internal voltage measurement of the battery pack voltage. If all device read circuits on all BMICs are read at close temporal intervals, for example, within 100 µS of the sampling instant T s, then the brick voltage from each BMIC 310, 312 can be summed together to create the independent internal battery pack voltage measurement. A battery pack voltage measured in this manner (by the brick read circuits 320, 322) can be communicated to the vehicle network and / or an SPI bus and represented by or referred to as SUM_OF_BRICK_VS. Those of ordinary skill in the art will recognize that individual cell voltages (rather than brick voltages) can also be used as an independent battery pack voltage measurement for applications where a brick voltage may not be available.

[0027] As mentioned above and in the block diagram from Fig. 4, the BECM has another internal circuit that measures a battery pack voltage (PACKV). The PACKV circuit 410 has a V_TOP input 412 of a divider circuit 420 (DIV1). As shown in Fig. 3 and Fig. 4, V_TOP 412 is connected to the most positive point on the traction cell string 220. The V_BOT node 414 is the most negative point in the cell string 220. The voltage divider circuit 420 has a reference input connected to V_BOT 414. Similarly, an analog-to-digital converter 422 (ADC2) has a reference input connected to V_BOT 414. Accordingly, a PACV circuit 410, and more specifically, the voltage divider 420, provides an internal measurement of the battery pack voltage via the inputs connected to V_TOP and V_BOT 412, 414, respectively.

[0028] The analog voltage divider 420 includes resistors and capacitors configured to perform the following two functions. First, the divider 420 divides, or staggers, the battery pack voltage PACKV from a high voltage (e.g., 400 V) to a low voltage range suitable for ADC 422. Many ADCs have an input voltage range of, for example, 0-5 V or 0-3.3 V. If the DC transfer function of DIV1 420 is divided by 100, for example, then a 400 V PACKV input is scaled to a 4 V signal suitable for input to the ADC 422. The divider 420 is also configured to implement an analog RC filter to satisfy the Nyquist criterion associated with half the sampling frequency.In one embodiment, analog divider 420 includes two RC sections to implement a two-pole passive analog RC filter to satisfy the Nyquist criterion while digitizing or sampling the battery pack voltage. The scaled or divided and filtered battery pack voltage provided to ADC 422 is then provided to BECM master micro 330 via the SPI bus connection and SPI isolator 430. This internal measurement, provided by the PACKV circuit, is available in digital form inside master micro 330 and is represented by PACKV_MEAS.

[0029] In a representative embodiment, the system is designed to make PACKV_MEAS a high-fidelity voltage measurement of the battery pack voltage, which is communicated on the vehicle network for use in various battery and vehicle control functions. The use of a high-quality two-pole filter in the divider 420 and a high-quality ADC 422, combined with programming the master micro 330 to sample the battery pack voltage fast enough to meet the Nyquist criterion and synchronizing the battery pack voltage sampling times via the ADC 422 with other key system quantities such as the battery pack current from the current sensor 360, which is also read by the master micro 330, provides a high-fidelity or high-quality measurement of the battery pack voltage PACKV_MEAS. This voltage is designed to be the most accurate indication of the measured battery pack voltage.Any other representation of the battery pack voltage provided by external circuitry represented by INV_PACKV_MEAS, DCDC_PACKV_MEAS, and EAC_PACKV_MEAS is generally not as accurate. Furthermore, battery pack voltage measurements provided by other internal and / or external circuitry may use different filter cutoff frequencies and may not be synchronized in measurement time. Accordingly, these independent battery pack voltage measurements are generally less accurate when the battery pack voltage changes rapidly (high dV / dt for PACKV), and the agreement between PACKV_MEAS and INV_PACKV_MEAS, DCDC_PACKV_MEAS, and EAC_PACKV_MEAS may be poor. These battery pack voltages have better correlation when the battery pack current is close to zero and the battery pack voltage does not change significantly over a corresponding period of time.

[0030] As also shown in the block diagram from Fig. 4, internal battery pack voltage circuits may include one or more leakage or dissipation detection circuits. In this embodiment, the dissipation detection circuit includes a positive branch 440 and a negative branch 460. The positive branch 440 includes a resistor 442 (R1), a MOSFET transistor 444, and a voltage sense resistor 446 (R2) connected between V_TOP 412 and the vehicle ground 448 (PWR_GND) or the vehicle body reference. A gate driver circuit 450 controls the gate of the MOSFET 444. The positive branch 440 also includes a differential amplifier 452 (DA1), the output of which is connected to an analog-to-digital converter 454 (ADC1) of the vehicle body reference. The ADC1 454 has a communication path, typically an SPI bus, which allows the BECM Master Micro 330 to read the analog voltages from DA1 452 and DA2 472, which is part of the negative branch 460.Similar to the positive branch 440, the negative branch 460 includes a resistor 462, a MOSFET transistor 464, and a voltage sense resistor 466 (R3). The transistor 464 is controlled by an associated gate driver circuit 470.

[0031] The leakage detection circuit provides detection of a leakage current, but can also be used to provide an internal measurement of the battery pack voltage through the operation of the positive branch 440 and the negative branch 460. For leakage current detection, one of the switches implemented by transistors 444, 464 is closed for a specified period of time. To detect an undesired leakage resistance from 448 to V_BOT 414, transistor 464 is controlled by a gate driver circuit 470 so that transistor 464 is left open while gate driver circuit 450 controls transistor 444 to close for a specified period of time, such as 1.5 seconds. During this time, the voltage across sense resistor 446 stabilizes and is processed by DA1 452 and read as an analog voltage by ADC1 454.Similarly, to detect an undesirable leakage resistance between PWR_GND 448 and V_TOP 412, transistor 444 is controlled to open by gate driver circuit 450, while transistor 464 is controlled to close by gate driver circuit 470. This allows a leakage indication to appear across sense resistor 466. This voltage is applied to DA2 472 and transferred to ADC1 454, converted to digital form, and read by the BECM master micro 330.

[0032] As described above, the leakage detection circuit can be operated to provide an independent internal measurement of the battery pack voltage. In this mode of operation, the MOSFET transistors 444, 464 are closed or turned on simultaneously. When both transistors 444, 464 are turned on, the resistive divider formed by resistors 442, 446, 466, and 462 can be used to determine the voltage applied from V_TOP 412 to V_BOT 414. If the high-fidelity measurement PACKV_MEAS is not available, this mode of operation can be used to provide an alternative internal measurement of the battery pack voltage, which can be used with one or more internal measurements and external measurements from corresponding internal or external circuitry to determine a transmitted battery pack voltage, as described in more detail herein.In this mode, ADC1 454 reads a first voltage across resistor 446 (R2) through DA1 452 and simultaneously reads a second voltage across resistor 466 (R3) through DA2 472. The combination or summation of the voltages from positive branch 440 and negative branch 460 provides a quantity that is linearly related to or scaled to the battery pack voltage based on the values of the resistors and the operation of the differential amplifiers.

[0033] In one embodiment, the drain detection circuit operating in a battery voltage measurement mode may determine a battery pack voltage according to: LKMEAS_PACKV=(Vr2+Vr3)*[(R1+R2+R3+R4) / (R2+R3)] where Vr2 is the voltage across resistor 446 (R2), Vr3 is the voltage across resistor 466 (R3), and R1 through R4 are the resistances of resistors 442, 446, 466, and 462, respectively. This provides an alternative measure of battery pack voltage, read by a different hardware path than that of PACKV_MEAS, to provide an independent internal circuit measurement of the battery pack voltage. Independence from the circuitry used to provide PACKV_MEAS allows the use of the leakage detection circuit to provide a redundant backup measurement in the event that PACKV_MEAS is unavailable or the functional assessment or self-diagnostics indicate that PACKV_MEAS is inaccurate or unreliable.

[0034] With reference to Fig. Figure 3 shows another internal circuit that can be used to provide an independent internal measurement of the battery pack voltage. Similar to the use of the device voltages described above, individual cell voltages of cells 2201 to 220 mmsummed or combined to provide a battery pack voltage measurement. The BMICs 310, 312 measure the cell voltages with a relatively long period or sampling interval, such as 100 mS, so that, for example, each cell is measured once in a 100 mS period. The BMIC readings of the cell voltages have excellent redundancy, making it relatively easy to self-test the uniformity of the BMIC inputs. Under normal operating conditions, the cell voltages of each of the cells are essentially the same, varying by less than a few millivolts. While the cells may occasionally become unbalanced and vary by more than the typical value, the BMICs 310, 312 monitor the cell voltages and rebalance the cells at regular intervals. A voltage variation of an individual battery cell can be represented by ΔV and can be determined by measuring all cell voltages at a time T sThe Master-Micro 330 processor is programmed to determine a maximum cell voltage, referred to as Vmax, and a minimum voltage, referred to as Vmin, where the difference is represented by ΔV = Vmax - Vmin.

[0035] The BMICs 310 and 312 may incorporate a number of self-diagnostic and other features that can raise a flag or other indication when abnormal operation is detected. These features are not described in detail here. However, functional descriptions are available in the product literature for commercially available BMICs such as the AD7280 analog devices.

[0036] The most reliable and redundant indication of the available battery pack voltage, other than PACKV_MEAS in the BECM 46, is the sum of individual cell voltages obtained by the BMICs 310, 312 at a time when the BMICs' self-diagnostic features indicate no errors (which means no IC failures as well as no open wires to the BECM module, which is also detected by the BMICs 310, 312) and when ΔV, as specified above, is below a corresponding threshold value represented by MIN_ACCEPTABLE_DELTA_V, which can be, for example, 50 mV. In other words, the following applies: the BMIC 310, 312 do not display any self-diagnostic errors or external errors AND ΔV <MIN_ACCEPTABLE_DELTA_V then the battery pack voltage provided by the internal circuitry associated with the sum of individual cell voltages is a highly reliable indication of the battery pack voltage and is represented by SUM_OF_CELLS_RELIABLE. This variable could be VALID or INVALID depending on whether the above conditions are met. This value is sampled relatively slowly (e.g., 100 mS), so while it provides a reliable indication of the battery pack voltage, it is not as accurate as the high-fidelity version provided by PACKV_MEAS. However, this is generally the most useful battery pack voltage measurement for backup purposes, especially when the voltage varies slowly.

[0037] In various embodiments, the PACKV_MEAS readings (from the PACKV circuit) are taken every 2 mS or, for example, every 10 mS. The battery pack voltage is read much faster than the cell voltage because PACKV is used for power calculations for the battery pack by multiplying PACKV_MEAS by the battery pack current from the current sensor 360 to obtain an instantaneous power. As described above, the system was designed to provide a high-fidelity reading of PACKV that is time-synchronized with the battery pack current reading from the master micro 330. Because the PACKV voltage and associated current amounts are synchronized, the two numbers can be directly multiplied to obtain a valid instantaneous power figure for the battery pack 24.

[0038] The following signals, variables, or messages provide independent internal measurements of the battery pack voltage as described above and are ideally the same value: VCONT_POS_MEAS, PACKV_MEAS, and SUM_OF_CELLS_RELIABLE. Similarly, the following signals, variables, or messages provide independent external measurements of the battery pack voltage as described above and are ideally the same value: INV_PACKV_MEAS, DCDC_PACKV_MEAS, and EAC_PACKV_MEAS. Each internal and external measurement has an associated flag or indication that is set to VALID and changed to INVALID if it is either out of range, has an internal error, or at a time when the measured value cannot be compared to the other circuit measurements of the battery pack voltage.For example, if the battery pack current is much greater than zero, the battery pack voltage will vary over time due to the equivalent series resistance (ESR) of the cells. Therefore, the functional evaluations described herein cannot run at all times, but only when contactors 236, 238 (. Fig. 2) are closed and the battery pack voltage is close to zero. At other times (for example, when contactors are open or the battery pack current is greater than a threshold value such as 1A), the BECM 46 uses the same configuration as when all valid measurements are available.

[0039] The signal, variable, or message represented by DELTA_INTERNAL_TRIAD has an associated flag set to VALID if the internal circuit measurement flags (VCONT_POS_MEAS, PACKV_MEAS, SUM_OF_CELLS_RELIABLE) are VALID. The Master Micro 330 marks these flags as VALID if the circuits have no internal errors and the signals are WITHIN RANGE. The signals are WITHIN RANGE if the values are within a predetermined calibratable range based on expected values during operation. The Master Micro 330 marks a signal flag as INVALID if there is an internal module error for the given circuit or if the given signal is OUT OF RANGE. DELTA_INTERNAL_TRIAD represents the voltage difference among all battery pack voltage measurements by the internal circuits and is specified as follows: DELTA_INTERNAL_TRIAD=MAX(VCONT_POS_MEAS, PACKV_MEAS, SUM_OF_CELLS_RELIABLE)−MIN(VCONT_POS_MEAS, PACKV_MEAS, SUM_OF_CELLS_RELIABLE) where MAX is a function that selects the maximum value of the parentheses variable, and MIN is a function that selects the minimum value of the parentheses variable.

[0040] Accordingly, DELTA_INTERNAL_TRIAD provides a measure of variation among the internal circuitry in the BECM, providing independent internal measurements of the battery pack voltage. As described above, VCONT_POS_MEAS uses the input circuitry of DIV1 420 with the V_CONT_POS input 250 relative to V_BOT 414 to measure DC_LINK, or the battery pack voltage. At a time when contactors 236, 238 are closed, VCONT_POS_MEAS provides a reading that approximately corresponds to the battery pack voltage reading. PACKV_MEAS is the high-fidelity battery pack voltage reading from the battery pack voltage reading circuitry in DIV1 420, which measures the voltage between V_TOP 412 and V_BOT 414. The SUM_OF_CELLS_RELIABLE is provided by BMIC 310, 312 and is valid under the conditions described above.If DELTA_INTERNAL_TRIAD < THRESHOLD_DELTA_INTERNAL_TRIAD, then the internal BECM circuits VCONT_POS_MEAS, PACKV_MEAS, and SUM_OF_CELLS_RELIABLE are considered reliable. Otherwise, one or more of the internal variables are inaccurate, and further steps are required to obtain a reliable battery pack voltage reading. For example, in one embodiment, THRESHOLD_DELTA_INTERNAL_TRIAD corresponds to 20 V.

[0041] Similarly, DELTA_EXTERNAL_TRIAD provides a measure of the variation among the external circuits that provide independent external measurements of the battery pack voltage and is determined as follows: DELTA_EXTERNAL_TRIAD=MAX(INV_PACKV_MEAS, DCDC_PACKV_MEAS, EAC_PACKV_MEAS)−MIN(INV_PACKV_MEAS, DCDC_PACKV_MEAS, EAC_PACKV_MEAS) where INV_PACKV_MEAS represents the external battery pack voltage measurement determined by inverter circuit 26, DCDC_PACKV_MEAS represents the external battery pack voltage measurement determined by DC / DC converter circuit 28, and EAC_PACKV_MEAS represents the external battery pack voltage measurement determined by eAC circuit 27. If DELTA_EXTERNAL_TRIAD < THRESHOLD_DELTA_EXTERNAL_TRIAD, then the external measurements represented by INV_PACKV_MEAS, DCDC_PACKV_MEAS, and EAC_PACKV_MEASE are all considered reliable. Otherwise, one or more of these external measurements are considered inaccurate, and further steps are required to determine a reliable measurement. For example, in one embodiment, THRESHOLD_DELTA_EXTERNAL_TRIAD corresponds to 20 V.

[0042] The BECM 46 may communicate a battery pack voltage to the vehicle network 230 based on a statistical measure of central tendency, such as a mean, median, or mode of the independent internal and external measurements. In one embodiment, a median battery pack voltage is determined as follows: MEDIAN_PACKV=MEDIAN(VCONT_POS_MEAS, PACKV_MEAS, SUM_OF_CELLS_RELIABLE,INV_PACKV_MEAS, DCDC_PACKV_MEAS, EAC_PACKV_MEAS) NOTE: Before executing this MEDIAN function, invalid elements such as VCONT_POS_MEAS, PACKV_MEAS, etc., are removed from the calculation. Therefore, this MEDIAN function operates on a list of values that are all valid. where the MEDIAN function is a statistical measure that determines the median of the parenthesized values by sorting or ordering the values from lowest to highest, taking the average or mean of the two middle values in the ordered data set. Using the median battery pack voltage in response to conditions specified below rejects input signals that are abnormal or out of range and can be unaffected if two of the six inputs are erroneously low or high.

[0043] Another variable, signal, or message is represented by RELIABLE_PACKV as follows: SWITCH (CASE)

[0044] { CASE ((PACKV_MEAS is VALID) ANDAND ((DELTA_INTERNAL_TRIAD is VALID) AND (DELTA_INTERNAL_TRIAD THRESHOLD_DELTA_INTERNAL_TRIAD))): {RELIABLE_PACKV = PACKV_MEAS}; BREAK; CASE (SUM_OF_CELLS_RELIABLE is VALID): RELIABLE_PACKV=SUM_OF_CELLS_RELIABLE; BREAK; CASE(((DELTA_EXTERNAL_TRIAD ist VALID) AND (DELTA_EXTERNAL_TRIAD<THRESHOLD_DELTA_EXTERNAL_TRIAD))): {RELIABLE_PACKV=MEDIAN_PACKV} BREAK; default: {RELIABLE_PACKV=DTC_FLAG}}

[0045] The flow of the above logic or method, executed by a programmed processor or computer such as the BECM 46, is as follows. If DELTA_INTERNAL_TRIAD is trustworthy (in this representative example, lower than the threshold of 20 V), then PACKV_MEAS is indicated as reliable and communicated to the vehicle network 230 as the battery pack voltage. If not, SUM_OF_CELLS_RELIABLE is the next most reliable indication and is used.However, if one or the other of PACKV_MEAS or SUM_OF_CELLS_RELIABLE is invalid, then the system can determine which is correct and then uses the MEDIAN_PACKV measure, which is the next most reliable indication of battery pack voltage, unless DELTA_EXTERNAL_TRIAD exceeds the associated threshold, in which case a diagnostic trouble code (DTC) or associated flag is set and a default or last known valid value of battery pack voltage can be used.

[0046] With reference to Fig. Figure 5 is a block diagram illustrating the operation of a system or method for controlling an electric vehicle, including performing a health assessment and communicating a battery pack voltage based on at least one internal measurement and one external measurement in response to the health assessment. With reference to the processes, systems, methods, heuristics, etc. described herein, it should be understood that although the steps of such processes, etc., may have been described as occurring in a particular ordered sequence, such processes could be practiced with the described steps performed in a different order than the order described herein.It should be understood that certain steps could be performed concurrently, other steps could be added, or certain steps described herein could be omitted while maintaining the teachings of this disclosure and being encompassed by the claimed subject matter. In other words, the descriptions of methods or processes are provided to illustrate particular embodiments, and it should be understood that these represent one of many variations and are not limited to those illustrated or described.

[0047] The block diagram from Fig. 5 provides an alternative operational illustration of various embodiments according to the disclosure similar to those already described. In block 510, a battery pack voltage measurement is obtained from an associated internal circuit, such as PACKV. The particular internal circuit used to provide the battery pack voltage measurement may vary depending on the application and implementation. The battery pack voltage measurement could be obtained from an external circuit if the system is configured to provide a high-fidelity battery pack voltage measurement. In most applications, the more accurate or trusted indication of the battery pack voltage is provided by one or more internal circuits within the battery pack and / or the battery controller.Self-diagnosis of the circuit providing the battery pack voltage measurement is performed as shown at 512 with an appropriate flag or status indicator set at 514 if no error or out-of-range information is identified at 512. Otherwise, the flag or status indicator may be set to, for example, INVALID or UNRELIABLE.

[0048] A second independent internal circuit may be used to measure individual cell voltages or a voltage across one or more groups or devices of individual cells, illustrated at 520. In one embodiment, the individual cell voltage circuit comprises BMICs associated with groups or devices of cells, as described above, where the BMICs perform various self-diagnostic functions, as illustrated at block 522. A voltage difference or differential among individual cells or devices may be compared to an associated threshold, as illustrated at 524, as an additional functional assessment of the associated components and cells in the circuit.If blocks 522 and 524 do not detect any errors or otherwise abnormal operation, an appropriate flag or status indicator is set or stored, as represented by block 526, to indicate that the sum of individual cell voltages is reliable.

[0049] Other internal measurements of the battery pack voltage, determined by the corresponding independent internal circuits, may be performed as described above and are generally represented by block 530. For example, block 530 may determine a battery pack voltage through appropriate control and operation of the transistors and / or contactors associated with a leakage detection circuit, as described above with reference to Fig. 4 described.

[0050] As also in Fig. 5, one or more external circuits provide corresponding independent external measurements of the battery pack voltage, as illustrated at block 540. In one embodiment, independent external measurements of the battery pack voltage are provided by an inverter module or circuit, as indicated at 542, an eAC module or circuit, as indicated at 544, and a DC / DC converter module or circuit, as indicated at 546. One or more external modules or circuits may provide an external measurement of the battery pack voltage by outputting or transmitting a corresponding signal or message to a vehicle network. Some or all of the external modules or circuits may also include self-diagnostic functions and associated status indicators or flags not expressly illustrated.

[0051] Block 552 compares the voltage difference among all internal measurements to an associated threshold. If the voltage difference is less than the associated threshold, as indicated at 552, then the measured battery pack voltage is used, as indicated at 560, and communicated to the vehicle network, as indicated at 570, for use by one or more controllers to control the battery pack and / or the vehicle. If the voltage difference among all internal voltage measurements exceeds the associated threshold, as indicated at 552, then the status indicator or flag associated with the individual cell's internal measurement is checked, as indicated at 554.If the internal circuitry(s) associated with the individual cells or groups of cells provide a reliable measurement, as described above, then the battery pack voltage uses the measurement of the sum of cells, as indicated at 562, and the communicated battery pack voltage 570 corresponds to the value determined by the sum of individual cells.

[0052] If the sum of cell voltages is not indicated as reliable, then block 556 determines whether a voltage difference among all external measurements of the battery pack voltage exceeds a corresponding threshold. If the voltage difference is less than the corresponding threshold, then a statistical measure or function is used to determine the reported battery pack voltage. In the illustrated embodiment, block 564 determines a median voltage of the internal measurements and external measurements for the reported battery pack voltage, which is then output or communicated to the vehicle network, as indicated at 570.If the voltage difference exceeds the appropriate threshold, as indicated at 556, then a diagnostic trouble code (DTC) may be stored, as indicated at 580, and the reported battery pack voltage may be converted back to a previous value or may be modeled or estimated by another method.

[0053] As in Fig.5, a controller communicating with the internal circuitry and the external circuitry is programmed to communicate a battery pack voltage to the vehicle network. The battery pack voltage corresponds to a first independent internal measurement at 560 in response to a voltage difference at 552 among all independent internal measurements being less than a threshold, a second independent internal measurement at 562 in response to the voltage difference at 552 exceeding the threshold, and a statistical measure of the independent internal and external measurements at 564 in response to any one of the internal measurements being invalid at 552, 554.The controller may be further programmed to store a diagnostic code in an associated non-volatile storage medium at 580 in response to the voltage difference at 552 being above the threshold and a second voltage difference among all independent external measurements exceeding an associated threshold at 556. The controller is further programmed to transmit the battery pack voltage at 570 according to the statistical measure at 564 unless a second voltage difference among all independent external measurements exceeds an associated threshold at 556.

[0054] Accordingly, embodiments according to the present disclosure may provide one or more advantages, such as performing a functional assessment and self-diagnosis of the validity of battery pack voltage measurements using measurements from internal and / or external circuitry. Furthermore, embodiments may provide a reliable indication of battery pack voltage when the functional assessment indicates that one or more of the internal or external circuits are not functioning as expected. Various embodiments provide self-diagnosis that uses the functional assessments described herein in combination with redundancy to provide a backup battery voltage measurement for use in controlling the battery and / or vehicle.

[0055] While representative embodiments are described above, these embodiments are not intended to describe all possible embodiments within the scope of the disclosure or claimed subject matter. The terms used in the specification are for the purpose of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.

[0056] Furthermore, the features of various embodiments may be combined to form another embodiment, even if certain combinations are not explicitly described or illustrated. Various embodiments have been described with respect to one or more desired characteristics as providing advantages or as being preferred over other prior art embodiments or implementations. However, one of ordinary skill in the art will appreciate that one or more features or characteristics may be compromised to achieve desired overall system attributes, depending on the particular application and implementation. These features may include, but are not limited to, cost, strength, safety, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc.Embodiments that are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure or claims and may be desirable for certain applications. It further describes: A. Vehicle comprising: a traction battery pack having a high voltage bus and a plurality of individual battery cells, the traction battery pack having a plurality of internal circuits providing a plurality of corresponding independent internal measurements of a voltage of the traction battery pack; a plurality of external circuits external to the traction battery pack and coupled to the high voltage bus and providing a plurality of corresponding independent external measurements of the voltage of the traction battery pack; an electric machine powered by the traction battery pack via one of the plurality of external circuits to propel the vehicle; and a controller in communication with the plurality of internal circuits and the plurality of external circuits and programmed to communicate a battery pack voltage to a vehicle network, the battery pack voltage corresponding to a first independent internal measurement in response to a voltage difference among all independent internal measurements being less than a threshold, a second independent internal measurement in response to the voltage difference exceeding the threshold, and a statistical measure of the independent internal and external measurements in response to any one of the internal measurements being invalid. B. Vehicle according to A, wherein the plurality of external circuits comprise: an inverter circuit; an electric air conditioning (eAC) circuit; and a DC / DC converter circuit. C. The vehicle of A, wherein the plurality of internal circuits includes a battery pack voltage measuring circuit that measures a voltage of the traction battery pack across the plurality of individual battery cells. D. The vehicle of A, wherein the plurality of internal circuits comprises a plurality of integrated battery monitoring circuits, each measuring a voltage across a corresponding group of the individual battery cells. E. The vehicle of D, wherein the controller is further programmed to combine voltages from the plurality of integrated battery monitoring circuits to determine one of the plurality of independent internal measurements of the voltage of the traction battery pack. F. The vehicle of A, wherein each of the plurality of external circuits transmits a corresponding one of the plurality of independent external measurements to the vehicle network. G. The vehicle of A, wherein the plurality of internal circuits comprises: a positive leg leakage detection circuit that measures the traction battery pack voltage from one of the most positive of the individual battery cells to the vehicle ground; and a negative leg leakage detection circuit that measures the traction battery pack voltage from one of the most negative of the individual battery cells to the vehicle ground. H. Vehicle according to G, wherein one of the plurality of independent internal measurements is based on a voltage across the positive leg leakage detection circuit and the negative leg leakage detection circuit. I. Vehicle according to A, where the statistical measure comprises a median value of the internal and external measurements. J. The vehicle of A, wherein the controller is further programmed to store a diagnostic code in an associated non-volatile storage medium in response to the voltage difference being above the threshold and a second voltage difference among all independent external measurements exceeding an associated threshold. K. The vehicle of A, wherein the controller is further programmed to transmit the battery pack voltage according to the statistical measure unless a second voltage difference from all independent external measurements exceeds an associated threshold. L. Vehicle comprising: a battery with internal circuits that measure a battery pack voltage and individual cell voltages; an electric machine driven by the battery to power the vehicle via an external circuit that measures the battery pack voltage; and a processor programmed to communicate the battery pack voltage based on a first internal circuit voltage in response to a voltage difference among the internal circuits being less than a threshold and based on the individual cell voltages. M. The vehicle of L, further comprising a second external circuit that measures the battery pack voltage, wherein the processor is further programmed to communicate the battery pack voltage based on a statistical measure of central tendency of the battery pack voltage measurements from the internal circuits and the external circuits. N. Vehicle according to M, wherein the processor is programmed to store a diagnostic code in response to a voltage difference among the external circuits exceeding a second threshold. O. The vehicle of M, wherein the processor is programmed to communicate the battery pack voltage based on a median of the battery pack voltage measurements from the internal circuits and the external circuits in response to a voltage difference among the external circuits being below the second threshold. P. The vehicle of M, wherein the second external circuit comprises one of an electric air conditioning (eAC) circuit and a DC / DC converter circuit. Q. Vehicle to L, wherein the external circuit transmits a measurement of the battery pack voltage to a vehicle network. R. A control method for an electric vehicle having a traction battery coupled to an electric machine, comprising: Outputting, by a vehicle processor, a battery pack voltage to a vehicle network based on internal voltage measurements in response to that a voltage difference among the internal measurements is less than a threshold value, and Output the battery pack voltage based on a statistical function of the internal measurements and otherwise transmitted voltage measurements from external circuits. S. Control method according to R, wherein the statistical function comprises summing internal measurements associated with individual battery cells. T. The control method of R, wherein the statistical function comprises a median value of the internal voltage measurements and the transmitted voltage measurements from the external circuits in response to a voltage difference of the transmitted voltage measurements from the external circuits being below an associated threshold.

Claims

[1] Vehicle (12) comprising: a traction battery pack (24) having a high voltage bus (50) and a plurality of individual battery cells (220), the traction battery pack (24) having a plurality of internal circuits providing a plurality of corresponding independent internal measurements of a voltage of the traction battery pack (24); a plurality of external circuits external to the traction battery pack (24) and coupled to the high voltage bus (50) and providing a plurality of corresponding independent external measurements of the voltage of the traction battery pack (24); an electric machine (14) operated by the traction battery pack (24) via one of the plurality of external circuits to propel the vehicle (12); and a controller in communication with the plurality of internal circuits and the plurality of external circuits and programmed to communicate a battery pack voltage to a vehicle network (230), wherein the battery pack voltage corresponds to a first independent internal measurement in response to a voltage difference among all of the independent internal measurements being less than a threshold, a second independent internal measurement in response to the voltage difference exceeding the threshold, and a statistical measure of the independent internal and external measurements in response to any one of the internal measurements being invalid. [2] The vehicle (12) of claim 1, wherein the plurality of external circuits comprise: an inverter circuit (26); an electric air conditioning (eAC) circuit (27); and a DC / DC converter circuit (28). [3] The vehicle (12) of claim 1, wherein the plurality of internal circuits comprises a battery pack voltage measuring circuit that measures a voltage of the traction battery pack (24) across the plurality of individual battery cells (220). [4] The vehicle (12) of claim 1, wherein the plurality of internal circuits comprises a plurality of integrated battery monitoring circuits, each measuring a voltage across a corresponding group of the individual battery cells (220). [5] The vehicle (12) of claim 4, wherein the controller is further programmed to combine voltages from the plurality of integrated battery monitoring circuits to determine one of the plurality of independent internal measurements of the voltage of the traction battery pack (24). [6] The vehicle (12) of claim 1, wherein each of the plurality of external circuits communicates a corresponding one of the plurality of independent external measurements to the vehicle network (230). [7] The vehicle (12) of claim 1, wherein the plurality of internal circuits comprises: a positive leg leakage detection circuit (440) that measures the voltage of the traction battery pack (24) from one of the most positive of the individual battery cells (220) to a ground of the vehicle (12); and a negative leg leakage detection circuit (460) that measures the voltage of the traction battery pack (24) from one of the most negative of the individual battery cells (220) to a ground of the vehicle (12). [8] The vehicle (12) of claim 7, wherein one of the plurality of independent internal measurements is based on a voltage across the positive leg leakage detection circuit (440) and the negative leg leakage detection circuit (460). [9] The vehicle (12) of claim 1, wherein the statistical measure comprises a median value of the internal and external measurements. [10] The vehicle (12) of claim 1, wherein the controller is further programmed to store a diagnostic code in an associated non-volatile storage medium in response to the voltage difference being above the threshold and a second voltage difference among all independent external measurements exceeding an associated threshold.

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