Abstract:
A battery pack according to an exemplary aspect of the present disclosure includes, among other things, a battery monitoring integrated circuit (BMIC) associated with a grouping of battery cells, a calibration microcontroller configured to store battery data associated with the grouping of battery cells, a main microcontroller; and a data transmission node establishing a shared path for communicating both a status signal from the BMIC and the battery data from the calibration microcontroller.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to a battery communication system for a battery pack. The battery communication system is configured to request and transmit battery data along a path that is shared with a heartbeat generation circuit of a battery monitoring integrated circuit (BMIC). 
       BACKGROUND 
       [0002]    The desire to reduce automotive fuel consumption and emissions is well documented. Therefore, vehicles are being developed that reduce or completely eliminate reliance on internal combustion engines. Electrified vehicles are one type of vehicle currently being developed for this purpose. In general, electrified vehicles differ from conventional motor vehicles because they are selectively driven by one or more battery powered electric machines. Conventional motor vehicles, by contrast, rely exclusively on the internal combustion engine to drive the vehicle. 
         [0003]    A high voltage battery pack typically powers the electric machines and other electrical loads of the electrified vehicle. The battery pack includes a plurality of battery cells arranged in one or more cell stacks or groupings. The battery cells require monitoring to maximize efficiency, maximize performance, and detect potential battery malfunctions. Some battery packs utilize battery monitoring integrated circuits (BMIC&#39;s) for performing various battery cell monitoring tasks. 
       SUMMARY 
       [0004]    A battery pack according to an exemplary aspect of the present disclosure includes, among other things, a battery monitoring integrated circuit (BMIC) associated with a grouping of battery cells, a calibration microcontroller configured to store battery data associated with the grouping of battery cells, a main microcontroller, and a data transmission node establishing a shared path for communicating both a status signal from the BMIC and the battery data from the calibration microcontroller. 
         [0005]    In a further non-limiting embodiment of the foregoing battery pack, the BMIC includes a heartbeat generation circuit configured to periodically generate the status signal. 
         [0006]    In a further non-limiting embodiment of either of the foregoing battery packs, the heartbeat generation circuit includes a switching device. 
         [0007]    In a further non-limiting embodiment of any of the foregoing battery packs, the calibration microcontroller includes a memory device configured to store the battery data. 
         [0008]    In a further non-limiting embodiment of any of the foregoing battery packs, the main microcontroller includes a data transmission circuit and a data reception circuit. 
         [0009]    In a further non-limiting embodiment of any of the foregoing battery packs, the BMIC and the calibration microcontroller are part of a permanent memory circuit board mounted on or near the grouping of battery cells. 
         [0010]    In a further non-limiting embodiment of any of the foregoing battery packs, the permanent memory circuit board includes a data transmission circuit and a data reception circuit. 
         [0011]    In a further non-limiting embodiment of any of the foregoing battery packs, the data transmission circuit includes a first switching transistor, a first resistor, a second resistor, and a second switching transistor, and the data reception circuit includes a switching device and a third resistor. 
         [0012]    In a further non-limiting embodiment of any of the foregoing battery packs, the main microcontroller is located remotely from the calibration microcontroller. 
         [0013]    In a further non-limiting embodiment of any of the foregoing battery packs, the calibration microcontroller includes a data transmission pin connected to a data transmission circuit and a receiver pin connected to a data reception circuit. 
         [0014]    In a further non-limiting embodiment of any of the foregoing battery packs, the data transmission node is a single node connecting between the calibration microcontroller and the main microcontroller. 
         [0015]    A method according to another exemplary aspect of the present disclosure includes, among other things, transmitting battery data within a battery communication system of a battery pack along a path that is shared with a status signal from a battery monitoring integrated circuit (BMIC). 
         [0016]    In a further non-limiting embodiment of the foregoing method, the path is established by a single data transmission node of the battery communication system. 
         [0017]    In a further non-limiting embodiment of either of the foregoing methods, the method includes comparing a cyclic redundancy check (CRC) signal sent by a calibration microcontroller with a CRC value saved on a main microcontroller. 
         [0018]    In a further non-limiting embodiment of any of the foregoing methods, the method includes operating the battery communication system in normal mode if the CRC signal matches the CRC value. 
         [0019]    In a further non-limiting embodiment of any of the foregoing methods, the method includes operating the battery communication system in data request mode if the CRC signal does not match the CRC value. 
         [0020]    In a further non-limiting embodiment of any of the foregoing methods, during the data request mode, the main microcontroller commands the calibration microcontroller to send the battery data over the path. 
         [0021]    In a further non-limiting embodiment of any of the foregoing methods, during the data request mode, the main microcontroller pulls a high portion of the status signal down to zero volts to request the battery data to be transmitted along the path. 
         [0022]    In a further non-limiting embodiment of any of the foregoing methods, the method includes storing the battery data within a memory device of a calibration microcontroller. 
         [0023]    In a further non-limiting embodiment of any of the foregoing methods, the battery data includes at least one of calibration data, health data, and pertinent constants associated with a grouping of battery cells of the battery pack. 
         [0024]    The embodiments, examples, and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
         [0025]    The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  schematically illustrates a powertrain of an electrified vehicle. 
           [0027]      FIG. 2  is a schematic, system diagram of a portion of a battery communication system for a battery pack. 
           [0028]      FIG. 3  schematically illustrates a process flow for an exemplary control strategy for requesting and transmitting battery data within a battery communication system of a battery pack. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    This disclosure details a system and method for monitoring battery cells of a battery pack. More particularly, this disclosure details a system and method for storing identification and calibration information related to battery cells in a modular battery pack. The identification and calibration information can be stored within the battery pack at a location away from the controlling electronics of the battery pack. 
         [0030]    An exemplary battery communication system includes a battery monitoring integrated circuit (BMIC), a calibration microcontroller, and a main microcontroller. The main microcontroller communicates with the calibration microcontroller to request and transmit battery data associated with a grouping of battery cells. In some embodiments, the battery data is transmitted along a path that is shared with a heartbeat generation circuit of the BMIC. In other embodiments, the battery data is stored in a memory device of the calibration microcontroller and therefore kept with the battery cells rather than remotely from the cells. These and other features are discussed in greater detail in the following paragraphs of this detailed description. 
         [0031]      FIG. 1  schematically illustrates a powertrain  10  for an electrified vehicle  12 . Although depicted as a hybrid electric vehicle (HEV), it should be understood that the concepts described herein are not limited to HEV&#39;s and could extend to other electrified vehicles, including, but not limited to, plug-in hybrid electric vehicles (PHEV&#39;s), battery electric vehicles (BEV&#39;s), fuel cell vehicles, etc. Moreover, although the battery communication systems of this disclosure are described in relation to electrified vehicles, it should be understood that the various features and advantages of the exemplary battery communication systems are applicable for use within battery packs of any type of device, machine, or system. Thus, the electrified vehicle  12  of  FIG. 1  is intended only as a non-limiting example of an environment which might include the battery communication systems and methods of this disclosure. 
         [0032]    In a non-limiting embodiment, the powertrain  10  is a power-split powertrain system that employs a first drive system and a second drive system. The first drive system includes a combination of an engine  14  and a generator  18  (i.e., a first electric machine). The second drive system includes at least a motor  22  (i.e., a second electric machine), the generator  18 , and a battery pack  24 . In this example, the second drive system is considered an electric drive system of the powertrain  10 . The first and second drive systems generate torque to drive one or more sets of vehicle drive wheels  28  of the electrified vehicle  12 . Although a power-split configuration is depicted in  FIG. 1 , this disclosure extends to any hybrid or electric vehicle including full hybrids, parallel hybrids, series hybrids, mild hybrids or micro hybrids. 
         [0033]    The engine  14 , which in one embodiment is an internal combustion engine, and the generator  18  may be connected through a power transfer unit  30 , such as a planetary gear set. Of course, other types of power transfer units, including other gear sets and transmissions, may be used to connect the engine  14  to the generator  18 . In one non-limiting embodiment, the power transfer unit  30  is a planetary gear set that includes a ring gear  32 , a sun gear  34 , and a carrier assembly  36 . 
         [0034]    The generator  18  can be driven by the engine  14  through the power transfer unit  30  to convert kinetic energy to electrical energy. The generator  18  can alternatively function as a motor to convert electrical energy into kinetic energy, thereby outputting torque to a shaft  38  connected to the power transfer unit  30 . Because the generator  18  is operatively connected to the engine  14 , the speed of the engine  14  can be controlled by the generator  18 . 
         [0035]    The ring gear  32  of the power transfer unit  30  may be connected to a shaft  40 , which is connected to vehicle drive wheels  28  through a second power transfer unit  44 . The second power transfer unit  44  may include a gear set having a plurality of gears  46 . Other power transfer units may also be suitable. The gears  46  transfer torque from the engine  14  to a differential  48  to ultimately provide traction to the vehicle drive wheels  28 . The differential  48  may include a plurality of gears that enable the transfer of torque to the vehicle drive wheels  28 . In one embodiment, the second power transfer unit  44  is mechanically coupled to an axle  50  through the differential  48  to distribute torque to the vehicle drive wheels  28 . 
         [0036]    The motor  22  can also be employed to drive the vehicle drive wheels  28  by outputting torque to a shaft  52  that is also connected to the second power transfer unit  44 . In one embodiment, the motor  22  and the generator  18  cooperate as part of a regenerative braking system in which both the motor  22  and the generator  18  can be employed as motors to output torque. For example, the motor  22  and the generator  18  can each output electrical power to the battery pack  24 . 
         [0037]    The battery pack  24  is an exemplary electrified vehicle battery. The battery pack  24  may be a high voltage traction battery pack that includes a plurality of battery assemblies  25  (i.e., battery arrays or groupings of battery cells) capable of outputting electrical power to operate the motor  22 , the generator  18  and/or other electrical loads of the electrified vehicle  12 . Other types of energy storage devices and/or output devices could also be used to electrically power the electrified vehicle  12 . 
         [0038]    In one non-limiting embodiment, the electrified vehicle  12  has two basic operating modes. The electrified vehicle  12  may operate in an Electric Vehicle (EV) mode where the motor  22  is used (either with or without assistance from the engine  14 ) for vehicle propulsion, thereby depleting the battery pack  24  state of charge up to its maximum allowable discharging rate under certain driving patterns/cycles. The EV mode is an example of a charge depleting mode of operation for the electrified vehicle  12 . During EV mode, the state of charge of the battery pack  24  may increase in some circumstances, for example due to a period of regenerative braking. The engine  14  is generally OFF under a default EV mode but could be operated as necessary based on a vehicle system state or as permitted by the operator. 
         [0039]    The electrified vehicle  12  may additionally operate in a Hybrid (HEV) mode in which the engine  14  and the motor  22  are both used for vehicle propulsion. The HEV mode is an example of a charge sustaining mode of operation for the electrified vehicle  12 . During the HEV mode, the electrified vehicle  12  may reduce the motor  22  propulsion usage in order to maintain the state of charge of the battery pack  24  at a constant or approximately constant level by increasing the engine  14  propulsion. The electrified vehicle  12  may be operated in other operating modes in addition to the EV and HEV modes within the scope of this disclosure. 
         [0040]      FIG. 2  schematically illustrates a battery communication system  54  for monitoring battery cells  56  of a battery pack, such as the battery pack  24  of  FIG. 1  or any other battery pack. The battery cells  56  supply electrical power to various electrical loads. The battery communication system  54  may be configured to monitor any number of battery cells  56 . The battery cells  56  of this disclosure may include any geometry (prismatic, cylindrical, pouch, etc.) or chemistry (lithium-ion, nickel-hydride, lead-acid, etc.). 
         [0041]    The battery communication system  54  includes a permanent memory circuit board  58  and a main microcontroller  60 . In a non-limiting embodiment, the permanent memory circuit board  58  is mounted directly to, or in close proximity to, one or more of the battery cells  56 , and the main microcontroller  60  is mounted within the battery pack  24  at a location remote from the battery cells  56 . An imaginary divider  62  is illustrated by a dashed line in  FIG. 2 . The imaginary divider  62  is included to schematically indicate that the permanent memory circuit board  58  and the main microcontroller  60  of the battery communication system  54  are remote from one another inside the battery pack  24 . 
         [0042]    In another non-limiting embodiment, the permanent memory circuit board  58  includes a battery monitoring integrated circuit (BMIC)  64 , a calibration microcontroller  66 , a first data transmission circuit  68 , and a first data reception circuit  70 . The main microcontroller  60  may include a second data transmission circuit  72  and a second data reception circuit  74 . A data transmission node  76  connects between the permanent memory circuit board  58  and the main microcontroller  60 . Battery data is transmitted between the calibration microcontroller  66  and the main microcontroller  60  over the data transmission node  76 , in a first embodiment. In another embodiment, status signals from the BMIC  64  are also communicated over the data transmission node  76 . 
         [0043]    The BMIC  64  performs multiple functions. Non-limiting examples of the various functions of the BMIC  64  include measuring voltages of the battery cells  56 , balancing each cell of the grouping of battery cells  56 , and performing battery cell diagnostics. Battery data analyzed and collected by the BMIC  64  is selectively communicated to the main microcontroller  60  for further processing, as discussed in greater detail below. 
         [0044]    A non-limiting example of a suitable BMIC is the Freescale MC3371. However, other integrated circuits may also be utilized within the scope of this disclosure. Moreover, although a single BMIC  64  is illustrated in  FIG. 2 , the battery communication system  54  could incorporate additional BMIC&#39;s. For example, the battery pack  24  could include multiple groupings of battery cells  56 , and one BMIC  64  may be dedicated to each separate grouping of battery cells  56 . In another non-limiting embodiment, one BMIC  64  may be associated with each individual battery cell  56  of the battery pack  24 . This disclosure is thus not limited to any specific number of battery cells or BMIC&#39;s. 
         [0045]    In another non-limiting embodiment, the BMIC  64  includes a heartbeat generation circuit  78 . The heartbeat generation circuit  78  includes a switching device  82 , such as a transistor. The BMIC  64  is configured to periodically generate a status signal, sometimes referred to as a “heartbeat” signal, indicating that the BMIC  64  is operating correctly. The status signal (non-faulted) is typically high for a short duration (e.g., approximately 500 μs) and low for a longer duration (e.g., approximately 10 to 100 ms). The high portion of the status signal will be at the voltage potential or magnitude of the grouping of battery cells  56  that power the BMIC  64 , and the low portion will be equipotential with the bottom of the battery pack  24 . In a non-limiting embodiment, the high portion of the status signal pulls the data transmission node  76  close to the potential of the voltage of the grouping of battery cells  56 . The low portion of the status signal occurs as the heartbeat generation circuit  78  releases the status signal onto the data transmission node  76 . This causes the voltage on the data transmission node  76  to float down to the bottom of the battery pack  24 . 
         [0046]    The first data transmission circuit  68  of the permanent memory circuit board  58  is designed to communicate with the second data reception circuit  74  and includes a first switching transistor  84 , a first resistor  86 , a second resistor  88 , and a second switching transistor  90 . The first switching transistor  84  is controlled by a transmission pin  92  of the calibration microcontroller  66 . The first switching transistor  84  turns ON as the transmission pin  92  of the calibration microcontroller  66  gets pulled above the turn-on voltage of the first switching transistor  84  with respect to the bottom of the battery pack  24  (e.g., into saturation). This pulls current through the first and second resistors  86 ,  88  and turns the second switching transistor  90  ON, thus pulling the data transmission node  76  close to the voltage potential of the grouping of battery cells  56 . In a non-limiting embodiment, the calibration microcontroller  66  transmits battery data via the first data transmission circuit  68  only while the status signal from the heartbeat generation circuit  78  is low. 
         [0047]    The first data reception circuit  70  of the permanent memory circuit board  58  includes a switching device  94 , such as a MOSFET device or any kind of transistor or logic, and a resistor  96 . The switching device  94  includes a source terminal  98  connected to the output of the heartbeat generation circuit  78  and the first data transmission circuit  68 , a gate terminal  100  connected to the data transmission node  76 , and a drain terminal  102  connected to a receiver pin  104  of the calibration microcontroller  66 . When the data transmission node  76  is pulled low by the main microcontroller  60 , the switching device  94  turns ON and the status signal voltage is received on the data transmission node  76 . In a non-limiting embodiment, the first data reception circuit  70  forms an AND function between the status signal from the heartbeat generation circuit  78  and the output of the second data transmission circuit  72  of the main microcontroller  60 . However, other circuit configurations can also be used to implement this functionality. 
         [0048]    The second data reception circuit  74  of the main microcontroller  60  includes an isolation device  106 . The isolation device  106  may be a photo-MOS or other similar device. The second data reception circuit  74  is configured to sense the waveform present on the data transmission node  76  through the control side of the isolation device  106 . When the output of the isolation device  106  is high, the base of a switching transistor  108  is tied to Vcc through a resistor  110 , thus biasing the switching transistor  108  forward-active. This pulls a receiver pin  112  of the main microcontroller  60  close to chassis ground. The effect of the second data reception circuit  74  is to output an inverted or non-inverted copy of whatever waveform is present on the data transmission node  76 . 
         [0049]    The second data transmission circuit  72  of the main microcontroller  60  is designed to communicate with the first data reception circuit  70  and includes yet another isolation device  114  and a MOSFET device  116 . The function of the second data transmission circuit  72  is to pull the data transmission node  76  down enough to bias the Switching device  94  of the calibration microcontroller  66  ON. When a transmission pin  118  of the main microcontroller  60  is high, the MOSFET device  116  is biased in saturation mode and allows current to flow through the transmission side of the isolation device  114 . Once the isolation device  114  is ON, the data transmission node  76  is pulled to the bottom of the battery pack  24  through a resistor  120 . 
         [0050]    In another non-limiting embodiment, the data transmission node  76  is a single node that crosses between the permanent memory circuit board  58  and the main microcontroller  60  and allows for communication between them without disrupting the status signal generated by the heartbeat generation circuit  78  of the BMIC  64 . The data transmission node  76  can be pulled high by the heartbeat generation circuit  78  and the transmission pin  92  of the calibration microcontroller  66 , or can be pulled low by the second data transmission circuit  72  of the main microcontroller  60 . The high or low status of the data transmission node  76  can be monitored and controlled at all times by the main microcontroller  60 , while the calibration microcontroller  66  only receives the status of the data transmission node  76  when the second data transmission circuit  72  of the main microcontroller  60  is active. Stated another way, the second data transmission circuit  72  of the main microcontroller  60  must transmit a window around the status signal sent by the heartbeat generation circuit  78  in order for the calibration microcontroller  66  to read the status of the data transmission node  76 . In such a case, the calibration microcontroller  66  sees a double pulse when the main microcontroller  60  is asserting its status bit. 
         [0051]    The calibration microcontroller  66  includes a memory device  122  for selectively storing battery data prior to sending the data to the main microcontroller  60  via the communication circuitry of the battery communication system  54 . The memory device  122  may include any type of memory including but not limited to RAM, ROM, SRAM, FLASH, EEPROM, etc. In a non-limiting embodiment, the battery data may include calibration data, health data, pertinent constants, or any other information collected by the BMIC  64  that is related to the battery cells  56 . Because the battery data is stored in the calibration microcontroller  66 , which is part of the permanent memory circuit board  58  and thus mounted in proximity to the battery cells  56 , this data is always located with the battery cells  56 . 
         [0052]    In a non-limiting embodiment, the main microcontroller  60  is a battery energy control module (BECM). In another non-limiting embodiment, the main microcontroller  60  is part of an overall vehicle control unit, such as a vehicle system controller (VSC). The main microcontroller  60  is programmed with executable instructions for interfacing with and operating the various components of the battery communication system  54 . The main microcontroller  60  includes various inputs and outputs for interfacing with the various components of the battery communication system  54 . In addition, although not shown, the main microcontroller  60  may include a processing unit and non-transitory memory for executing the various control strategies and modes of the battery communication system  54 . 
         [0053]      FIG. 3 , with continued reference to  FIGS. 1 and 2 , illustrates a control strategy  200  for requesting and transmitting battery data within the battery communication system  54  of the battery pack  24 . The control strategy  200  allows battery data associated with the grouping of battery cells  56  to be requested and transmitted along a path (e.g., established by the data transmission node  76 ) that is shared with the status signals generated by the heartbeat generation circuit  78  of the BMIC  64 . 
         [0054]    The control strategy  200  begins at block  202  in response to a Key-On event of the electrified vehicle  12 . At block  204 , the heartbeat generation circuit  78  of the BMIC  64  initializes and then generates a status signal. The main microcontroller  60  asserts a “0” in the middle of every other status signal at block  206 . Next, at block  208 , the calibration microcontroller  66  sends a cyclic redundancy check (CRC) signal to the main microcontroller  60 . 
         [0055]    The CRC signal sent at block  208  is compared with a CRC value stored in the main microcontroller  60  at block  210 . The CRC value may be stored in a look-up table, in a non-limiting embodiment. If the CRC signal from the calibration microcontroller  66  matches that CRC value stored in the main microcontroller  60 , the control strategy  200  proceeds to block  212 , at which the main microcontroller  60  asserts a “0” in the middle of every other status signal from the BMIC  64 . This indicates normal operation and thus battery data is not requested from the calibration microcontroller  66 . 
         [0056]    Alternatively, if the CRC signal from the calibration microcontroller  66  does not match that CRC value stored in the main microcontroller  60  at block  210 , the control strategy  200  proceeds to block  214 . During block  214 , the main microcontroller  60  behaves in a data request mode and asserts a status bit in the middle of every status signal, thus signaling the calibration microcontroller  66  to send battery data during the time the status signal is low. This occurs at block  216 . 
         [0057]    In a non-limiting embodiment, the battery data request and transmission must be hidden in the status signal pulse without disrupting its original function in diagnosing the state of the BMIC  64 . To that end, the main microcontroller  60  uses a status bit during the high portion of the status signal pulse to control the behavior of the calibration microcontroller  66 . In other words, the main microcontroller  60  pulls the high pulse of the status signal down to zero volts with respect to the bottom of the battery pack  24  for a short time. The effect of this is that the calibration microcontroller  66  sees a double pulse when the main microcontroller  60  is asserting its status bit. 
         [0058]    The calibration microcontroller  66  finishes sending battery data at block  218 . The battery data is stored in the memory device  122  of the calibration microcontroller  66  and a new CRC signal is calculated from this battery data. 
         [0059]    Next, at block  220 , the calibration microcontroller  66  sends the revised CRC signal to the main microcontroller  60 . The revised CRC signal is compared with the CRC value stored in the main microcontroller  60  at block  222 . If the CRC signal from the calibration microcontroller  66  matches that CRC value stored in the main microcontroller  60 , the control strategy  200  proceeds to block  212  and normal operation is confirmed. However, if the revised CRC signal and the CRC value do not match, the control strategy  200  returns to block  214 . The control strategy  200  ends at block  224 . 
         [0060]    Although the different non-limiting embodiments are illustrated as having specific components or steps, the embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
         [0061]    It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should be understood that although a particular component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the teachings of this disclosure. 
         [0062]    The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.