EP4569341A1 - A system for diagnosing loose contact in a battery pack - Google Patents

A system for diagnosing loose contact in a battery pack

Info

Publication number
EP4569341A1
EP4569341A1 EP23761615.6A EP23761615A EP4569341A1 EP 4569341 A1 EP4569341 A1 EP 4569341A1 EP 23761615 A EP23761615 A EP 23761615A EP 4569341 A1 EP4569341 A1 EP 4569341A1
Authority
EP
European Patent Office
Prior art keywords
cell group
control unit
contact terminal
reference cell
voltage drop
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23761615.6A
Other languages
German (de)
French (fr)
Inventor
Upender Rao Koleti
Madduri Saikranthi SURYA
Kishorekumar HANSDA
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TVS Motor Co Ltd
Original Assignee
TVS Motor Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by TVS Motor Co Ltd filed Critical TVS Motor Co Ltd
Publication of EP4569341A1 publication Critical patent/EP4569341A1/en
Pending legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/396—Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/54—Testing for continuity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/66—Testing of connections, e.g. of plugs or non-disconnectable joints

Definitions

  • the present invention generally relates to a battery pack and particularly relates to a system for diagnosing at least one loose contact in the battery pack and a method thereof.
  • a battery pack usually includes a plurality of battery modules or cell groups electrically interconnected with each other to produce desired current and voltage outputs.
  • a battery module includes a plurality of battery cells interconnected to each other. The battery module achieves desired voltage by connecting several battery cells in series, such that each battery cell adds its voltage potential to derive the total terminal voltage. Similarly, the battery module achieves desired current by connecting several battery cells in parallel. If higher voltages or currents are needed and larger battery cells are not available or do not fit the design constraint, one or more battery cells can be connected in series or parallel to achieve the desired electrical output. Generally, the battery module employs a combination of series and parallel connections for its plurality of battery cells.
  • the battery cell is provided with two cell tabs or terminals, one positive and other negative to connect the battery cell to another battery cell or to an external load.
  • the aforementioned series and/or parallel connections between individual battery cells of the battery module are achieved by electrically connecting the cell tabs or terminals of different battery cells.
  • a plurality of standard battery cells is employed in the battery modules used in various applications like automobiles, power tools, etc.
  • the plurality of standard cylindrical battery cells is electrically interconnected with each other in a combination of series and parallel to achieve the desired electrical output.
  • each of the battery modules of the battery pack may have a plurality of cell groups having a plurality of battery cells, all interconnected with each other.
  • the plurality of battery cells is connected together using connectors to the wiring harness in the vehicle.
  • many battery cells are connected in series.
  • Battery packs are also equipped with a BMS (Battery Management System) circuitry to monitor their health.
  • a cluster of battery cells may share one common BMS circuitry, i.e., a group of modules or cell groups can have the same common BMS circuitry.
  • Loose contacts at the positive and negative terminals of individual battery cells or of battery modules can lead to safety concerns from the potential arcing at the loose joints. Early detection of these loose contacts and ascertainment of the magnitude of voltage loss at the contact terminals is very important to avoid catastrophic events.
  • a plurality of temperature sensors is employed to detect loose contact at the terminals. The temperature sensors which are placed close to or on a connector cannot detect loose contact effectively as magnitude of electric current flowing through the connectors and heat distribution at connection joints influence the temperature rise. Further, arcing and momentary high heat losses at connection joints are difficult to detect using the temperature sensors. Also, temperature variation in electric connectors is a fairly slow process and thus will take time to reflect.
  • the BMS circuitry of a module or group of modules is capable of communicating with other BMS circuitries of other modules of the battery pack using a CAN bus. So, temperature variation measured at connection joints or terminals when communicated to a master controller of the battery pack will take a very long time before the measured values are communicated to the master controller and some instruction to remedy the fault is generated by the master controller. By this time damage would already have been done. Such unchecked loose contacts may turn catastrophic as the it encourages thermal runaway of the cells in the battery, if not addressed in time. BMS circuity of conventional battery packs are also not capable of interconnection of battery cells of its many battery modules.
  • Another way of monitoring loose contact in the battery pack is by measuring current in electrical wires in connecting the battery cells and the battery modules of the battery pack. A decrease in current is indicative of some fault in electrical connection. But this method does not indicate the location of fault. Thus, localization of fault will again require the use of multiple temperature sensors. Yet another way of measuring loose contact at connection joints or terminals is to measure the voltage across the joint. If there is loose contact, there will be a voltage drop across the connection joint. Thus, by measuring voltage across each battery cell, voltage drop and consequently loose contact may be detected. BMS circuitry for individual battery cells having capability to monitor health of the cells and loose contact at contact joints is known.
  • the present invention is directed to a system for diagnosing at least one loose contact in a battery pack.
  • the battery pack includes a plurality of battery cells which are organised into a plurality of cell groups. Each cell group has a first contact terminal and a second contact terminal, such that the first contact terminal of a reference cell group is connected to the second contact terminal of its preceding cell group and the second contact terminal of the reference cell group is connected to the first contact terminal of its succeeding cell group.
  • the system for diagnosing at least one loose contact in the battery pack includes a master control unit, a current sensor for each of the plurality of cell groups and a slave control unit for each of the plurality of cell groups.
  • the current sensor of the reference cell group is adapted to measure a current flowing through the reference cell group and communicate the measured current to the master control unit.
  • the slave control unit of the reference cell group is adapted to measure a voltage drop across its first contact terminal and the second contact terminal of its preceding cell group, and a voltage drop across its second contact terminal and the first contact terminal of its succeeding cell group.
  • the slave control unit of the reference cell group is adapted to measure a voltage drop across its first contact terminal and the last battery cell of its preceding cell group, and a voltage drop across its second contact terminal and the first battery cell of its succeeding cell group.
  • the slave control unit of the reference cell group is further adapted to communicate the measured voltage drops to the master control unit.
  • the master control unit is adapted to determine resistance between the first contact terminal of the reference cell group and the second contact terminal of its preceding cell group and/or the second contact terminal of the reference cell group and the first contact terminal of its succeeding cell group based on the measured voltage drop received from the slave control unit and measured current received from the current sensor.
  • the master control unit is adapted to determine resistance between the first contact terminal of the reference cell group and the last battery cell of its preceding cell group and/or resistance between the second contact terminal of the reference cell group and the first battery cell of its succeeding cell group based on the measured voltage drop received from the slave control unit and the measured current received from the current sensor.
  • the master control unit generates and communicates a warning indicating at least one loose contact, if at least one of the resistances determined is greater than a predetermined first threshold value.
  • the warning which indicates at least one loose contact generated and communicated by the master control unit includes information about the contact terminal where the loose contact has occurred.
  • the slave control unit of the reference cell group is adapted to measure a voltage drop across each battery cell of the reference cell group, and communicate the measured voltage drops to the master control unit.
  • the master control unit is adapted to determine resistance between each battery cell of the reference cell group based on the measured voltage drop received from the slave control unit and the measured current received from the current sensor. The master control unit generates and communicates said warning indicating at least one loose contact and a location of the loose contact if any of the resistances determined is greater than a predetermined second threshold value.
  • each of the plurality of cell groups includes a plurality of temperature sensors which are adapted to measure temperatures at the first contact terminal and the second contact terminal of the corresponding cell group, and at one or both terminals of one or more of the battery cells of the corresponding cell group.
  • the slave control units of the plurality of cell groups are adapted to communicate with each other and with the master control unit.
  • the present invention is directed to a method for diagnosing at least one loose contact in a battery pack.
  • the battery pack includes a plurality of battery cells which are organised into a plurality of cell groups. Each cell group has a first contact terminal and a second contact terminal, such that the first contact terminal of a reference cell group is connected to the second contact terminal of its preceding cell group and the second contact terminal of the reference cell group is connected to the first contact terminal of its succeeding cell group.
  • the method for diagnosing at least one loose contact in the battery pack includes the steps of measuring by a current sensor of the reference cell group, a current flowing through the reference cell group and communicating the measured current to a master control unit.
  • the method includes the steps of measuring by a slave control unit of the reference cell group, a voltage drop across the first contact terminal of the reference cell group and the second contact terminal of its preceding cell group, and a voltage drop across the second contact terminal of the reference cell group and the first contact terminal of its succeeding cell group.
  • the method includes the steps of measuring by the slave control unit of the reference cell group a voltage drop across the first contact terminal of the reference cell group and the last battery cell of its preceding cell group, and a voltage drop across the second contact terminal of the reference cell group and the first battery cell of its succeeding cell group.
  • the method includes the step of communicating by the slave control unit of the reference cell group, the measured voltage drops to the master control unit.
  • the method further includes the steps of determining by the master control unit resistance between the first contact terminal of the reference cell group and the second contact terminal of its preceding cell group, and resistance between the second contact terminal of the reference cell group and the first contact terminal of its succeeding cell group based on the measured voltage drop received from the slave control unit and the measured current received from the current sensor.
  • the method includes the steps of determining by the master control unit, resistance between the first contact terminal of the reference cell group and the last battery cell of its preceding cell group, and resistance between the second contact terminal of the reference cell group and the first battery cell of its succeeding cell group based on the measured voltage drop received from the slave control unit and the measured current received from the current sensor.
  • the method includes the steps of generating and communicating by the master control unit, a warning indicating at least one loose contact, if at least one of the resistances determined is greater than a predetermined first threshold value.
  • the method includes the steps of measuring by the slave control unit of the reference cell group, voltage drop across each battery cell of the reference cell group, and communicating by the slave control unit of the reference cell group, the measured voltage drops to the master control unit.
  • the method further includes the steps of determining by the master control unit, resistance between each battery cell of the reference cell group based on the measured voltage drop received from the slave control unit and the measured current received from the current sensor, and generating and communicating by the master control unit, said warning indicating at least one loose contact, if any of the resistances determined is greater than a predetermined second threshold value.
  • Figure 1 illustrates a block diagram of an exemplary system for diagnosing at least one loose contact in a battery pack, in accordance with an embodiment of the present invention.
  • Figure 2 illustrates a schematic view of an exemplary reference cell group of the system for diagnosing at least one loose contact in the battery pack, in accordance with an embodiment of the present invention.
  • Figure 3 illustrates a schematic view of two cell groups of the system for diagnosing at least one loose contact in the battery pack, in accordance with a first embodiment of the present invention.
  • Figure 4 illustrates a schematic view of two cell groups of the system for diagnosing at least one loose contact in the battery pack, in accordance with a second embodiment of the present invention.
  • Figure 5 illustrates a method for diagnosing at least one loose contact in the battery pack, in accordance with the first embodiment of the present invention.
  • Figure 6 illustrates another method for diagnosing at least one loose contact in the battery pack, in accordance with the second embodiment of the present invention.
  • Figure 7 illustrates a schematic view of the system and method for diagnosing at least one loose contact in the battery pack, in accordance with the first embodiment of the present invention.
  • Figure 8 illustrates another schematic view of the system and method for diagnosing at least one loose contact in the battery pack, in accordance with the second embodiment of the present invention.
  • Figure 9 illustrates another method for diagnosing at least one loose contact in the battery pack, in accordance with an embodiment of the present invention.
  • the battery pack is illustrated as being constituted of cell groups connected in series. However, it is contemplated that the disclosure in the present invention may be applied to any type of battery pack capable of accommodating the present subject matter without defeating the scope of the present invention.
  • the present invention generally relates to a battery pack and particularly relates to a system for diagnosing at least one loose contact in the battery pack and a method thereof.
  • FIG. 1 illustrates a block diagram of an exemplary system 100 for diagnosing at least one loose contact in a battery pack 10, in accordance with an embodiment of the present subject matter.
  • the battery pack 10 includes a plurality of cell groups 1 10.
  • each cell group 110 is an individual battery module.
  • each cell group 1 10 is a group of cells in a battery module.
  • Each of the plurality of cell groups 1 10 are constituted of a plurality of battery cells 120.
  • Each battery cell 120 has one positive terminal and one negative terminal.
  • the battery cells 120 of each cell group 1 10 are electrically interconnected with each other using any connection means known in the art like thin copper wires.
  • the plurality of cell groups 1 10 of the battery pack 10 are further electrically and communicatively interconnected with each other.
  • a cell group 110 has been selected as a reference cell group 1 1 Ox.
  • the reference cell group 1 10x can be any cell group 110.
  • the cell groups 1 10 preceding the reference cell group 11 Ox has been indicated as 110x-1, 11 Ox-2, etc. and the cell groups 1 10 succeeding the reference cell group 110x has been indicated as 1 10x+i , 1 1 Ox+2, etc.
  • the system 100 includes a master control unit 140, current sensors 150 and slave control units 160.
  • Each of the plurality of cell groups 1 10 is provided with one current sensor 150.
  • the current sensor 150 of the reference cell group 1 10x is adapted to measure a current flowing through the reference cell group 110x and communicate the measured current to the master control unit 140.
  • a single current sensor 150 may be employed for all the cell groups 1 10.
  • FIG. 2 illustrates a schematic view of an exemplary reference cell group 1 10x of the system 100 for diagnosing at least one loose contact in the battery pack 10, in accordance with an embodiment of the present subject matter.
  • Each cell group 1 10 has a first contact terminal 1 12 and a second contact terminal 114.
  • the first contact terminal 1 12 of the reference cell group 1 10x is connected to the second contact terminal 1 14 of its preceding cell group 1 10x-i.
  • the second contact terminal 1 14 of the reference cell group 1 10x is connected to the first contact terminal 112 of its succeeding cell group 110x+i.
  • the cell groups 110 in the battery pack 10 are connected in series.
  • Each of the plurality of cell groups 1 10 is provided with one slave control unit 160.
  • each slave control unit 160 constitutes a BMS (Battery Management System) ASIC (Application Specific Integrated Circuit). In another embodiment the slave control units 160 constitute a CMU (Battery Cell Management Unit).
  • the slave control unit 160 is capable of measuring voltages across each of the battery cells 120 in the cell group 1 10.
  • the slave control unit 160 has input pins that are hardwired to be connected at the positive terminal of each of the battery cells 120 and negative terminal of the last battery cell 120N in the cell group 1 10.
  • the first contact terminal 1 12 is connected to or is the same as the positive terminal of the first battery cell 120i in the cell group 1 10 and the second contact terminal 114 is connected to or is the same as the negative terminal of the last battery cell 120N in the cell group 1 10.
  • the slave control unit 160 senses voltages available at each of the hardwired points and based on the sensed voltages, the slave control unit 160 computes the voltage drop across the hardwired points.
  • the slave control unit 160 may transmit all the sensed voltages to the master control unit 140 and the master control unit 140 computes the voltage drops across these hardwired points.
  • the slave control unit 160 passes the voltage drops to the master control unit 140 along with the pin numbers across which the voltage drop was determined.
  • the master control unit 140 is aware of the voltage drops at the hardwired points and the slave control unit 160 identifier transmitting the voltage drops to localise the location of the loose contact based on the methods described in Figures 5 and 6.
  • FIG. 3 illustrates a schematic view of two cell groups 1 1 Ox and 1 10x-1 of the system 100 for diagnosing at least one loose contact in the battery pack 10, in accordance with a first embodiment of the present subject matter.
  • the slave control unit 160 of the reference cell group 1 10x is adapted to measure a voltage drop across its first contact terminal 1 12 and the second contact terminal 1 14 of its preceding cell group 1 10x-i .
  • the slave control unit 160 of the reference cell group 1 10x is further adapted to measure a voltage drop across its second contact terminal 114 and the first contact terminal 1 12 of its succeeding cell group 1 10x+i .
  • the slave control unit 160 has input pins that are hardwired to be connected at the first contact terminal 1 12 of the reference cell group 1 10xand the second contact terminal 1 14 of its preceding cell group 1 10x-i , and/or the second contact terminal 1 14 of the reference cell group 1 1 Ox and the first contact terminal 1 12 of its succeeding cell group 110x+i respectively.
  • FIG. 4 illustrates a schematic view of two exemplary reference cell groups 1 10x and 1 10x-1 of the system 100 for diagnosing at least one loose contact in the battery pack 10, in accordance with a second embodiment of the present subject matter.
  • the slave control unit 160 of the reference cell group 1 1 Ox is adapted to measure a voltage drop across its first contact terminal 1 12 and the last battery cell 120N of its preceding cell group 110x-i.
  • the slave control unit 160 of the reference cell group 11 Ox is further adapted to measure a voltage drop across its second contact terminal 1 14 and the first battery cell 120i of its succeeding cell group 110x+i.
  • the slave control unit 160 has input pins that are hardwired to be connected at the first contact terminal 1 12 of the reference cell group 1 10x and the last battery cell 120N of its preceding cell group 110x-i, and/or the second contact terminal 1 14 of the reference cell group 11 Ox and the first battery cell 120i of its succeeding cell group 1 10x+i respectively.
  • the slave control unit 160 of the reference cell group 1 10x is adapted to measure a voltage drop across each battery cell 120 of the reference cell group 1 10x.
  • the voltage measurements are taken by tapping for voltage the corresponding first contact terminal 1 12 or second contact terminal 1 14 of the respective cell groups 1 10, or the corresponding positive or negative terminals of the respective battery cells 120, as the case may be, using any conventional voltage tapping means like thin copper wire connections.
  • the voltage drop is detected by monitoring the voltage drop in the electric wires connecting the battery cells 120 or the cell groups 1 10 as the case may be. For this, existing elements of a BMS of the battery pack 10 can be used without adding any extra circuits.
  • one among many existing cell voltage monitoring channels of the BMS ASIC of the battery pack 10 can be used to detect the voltage drops. These measurements are fairly accurate with less than ⁇ 2 mV error and are faster to detect within around 100 milliseconds. The measurement of voltage drop is not influenced by temperature variations in the battery pack 10.
  • the slave control unit 160 of the reference cell group 1 10x is further adapted to communicate the measured voltage drops to the master control unit 140.
  • the slave control units 160 of the plurality of cell groups 1 10 are adapted to communicate with each other and with the master control unit 140.
  • the communication may be enabled by a CAN bus of the battery pack 10.
  • each of the plurality of cell groups 110 includes a plurality of temperature sensors 170.
  • the plurality of temperature sensors 170 is adapted to measure temperatures at the first contact terminal 112 and the second contact terminal 1 14 of the corresponding cell group 1 10.
  • the plurality of temperature sensors 170 are provided at one or both terminals of one or more of the battery cells 1 10 of the corresponding cell group 1 10.
  • the temperature sensors can measure temperature at the positive and negative terminals of the battery cells 120 of each cell group 110.
  • Use of typical analog circuits to detect accurately the voltage drop (in the order of mV) is limited due to limited accuracy in measuring the high voltages at the first and second contact terminals 112, 1 14 of the cell groups 1 10 to arrive at their difference. Therefore, in an embodiment, the temperature sensors 170 are placed on or in the vicinity of the first and second contact terminals 1 12, 114 to measure temperature changes. In another embodiment, the temperature sensors placed in the vicinity of the positive and negative terminals of the plurality of battery cells 120 aids in more accurate measurement of voltage drop between the battery cells.
  • FIG. 5 illustrates a method 500 for diagnosing at least one loose contact in the battery pack 10, in accordance with the first embodiment of the present subject matter.
  • the slave control unit 160 of the reference cell group 1 1 Ox measures 508 the voltage drop across its first contact terminal 112 and the second contact terminal 1 14 of its preceding cell group 1 10x-i.
  • the slave control unit 160 of the reference cell group 110x also measures 510 the voltage drop across its second contact terminal 1 14 and the first contact terminal 112 of its succeeding cell group 1 10x+i.
  • the cell group 11 Ox may be connected as shown in Figure 3.
  • the current sensor 150 of the reference cell group 11 Ox measures 504 a current flowing through the reference cell group 1 10x.
  • the current sensor 150 of the reference cell group 1 10x further communicates 506 the measured current to the master control unit 140.
  • the method 500 includes the step of communicating 512, by the slave control unit 160 of the reference cell group 1 10x, the measured voltage drops to the master control unit 140.
  • the master control unit 140 determines 514 resistance between the first contact terminal 1 12 of the reference cell group 1 10x and the second contact terminal 114 of its preceding cell group 1 10x-i, based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150.
  • FIG. 6 illustrates another method 500 for diagnosing at least one loose contact in the battery pack 10, in accordance with the second embodiment of the present subject matter.
  • the slave control unit 160 of the reference cell group 1 1 Ox measures 522 the voltage drop across its first contact terminal 1 12 and the last battery cell 120N of its preceding cell group 1 10x-i.
  • the slave control unit 160 of the reference cell group 110x also measures 524 the voltage drop across its second contact terminal 1 14 and the first battery cell 120i of its succeeding cell group 1 10x+i.
  • the cell group 1 10x may be connected as shown in Figure 4.
  • the current sensor 150 of the reference cell group 1 10x measures 504 a current flowing through the reference cell group 11 Ox.
  • the current sensor 150 of the reference cell group 1 10x further communicates 506 the measured current to the master control unit 140.
  • the method 500 includes the step of communicating 512, by the slave control unit 160 of the reference cell group 1 1 Ox, the measured voltage drops to the master control unit 140.
  • the master control unit 140 determines 526 resistance between the first contact terminal 112 of the reference cell group 1 10x and the last battery cell 120N of its preceding cell group 1 10x-i, based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150.
  • the master control unit 140 determines 528 resistance between the second contact terminal 1 14 of the reference cell group 1 10x and the first battery cell 120i of its succeeding cell group 110x+i based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. If any of the one or more resistances determined by the master control unit 140 is greater than a predetermined first threshold value, the master control unit 140 generates 518 and communicates 518 a warning indicating at least one loose contact.
  • the warning generated and communicated by the master control unit 140 comprises information about the contact terminal 1 12, 1 14 where the loose contact has occurred.
  • the warning may be displayed on a display device 180 (shown in Figure 1 ) or screen for a user of the appliance using the battery to view and/or may be directly communicated to the service station.
  • the display device includes an instrument cluster of a vehicle employing the batter pack 10, a personal mobile device, a personal computer, a dedicated screen on the battery pack 10, a computer device at the service station and the like.
  • the warning may also be communicated to the BMS or an ECU (Electronic Control Unit) which may turn off the faulty cell group 1 10.
  • the master control unit 140 is able to receive the voltage drop across the first contact terminal 1 12 of the reference cell group 1 10x and the last battery cell 120N of its preceding cell group 1 10x-i and/or the voltage drop across the second contact terminal 1 14 of the reference cell group 1 10x and the first battery cell 120i of its succeeding cell group 110x+i , inclusive of the voltages of the respective battery cells 120i, 120N. Since the individual voltages of the respective battery cells 120i, 120N are also known to the master control unit 140, it can estimate and localize the voltage drop across the connectors.
  • Figure 7 illustrates a schematic view of the first embodiment of the system 100 and method the 500 for diagnosing at least one loose contact in the battery pack 10.
  • the cell group 1 1 Ox may be connected as shown in Figure 3.
  • the current sensor 150 of the reference cell group 1 1 Ox measures 504 a current flowing through the reference cell group 1 10x.
  • the current sensor 150 of the reference cell group 1 10x further communicates 506 the measured current to the master control unit 140.
  • the method 500 includes the step of communicating 512, by the slave control unit 160 of the reference cell group 110x, the measured voltage drops to the master control unit 140.
  • the master control unit 140 determines 526 resistance between the first contact terminal 1 12 of the reference cell group 110x and the last battery cell 120N of its preceding cell group 110x-i, based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. In another embodiment, the master control unit 140 determines 528 resistance between the second contact terminal 1 14 of the reference cell group 1 10x and the first battery cell 120i of its succeeding cell group 110x+i based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150.
  • the master control unit 140 If any of the one or more resistances determined by the master control unit 140 is greater than a predetermined first threshold value, the master control unit 140 generates 518 and communicates 518 a warning indicating at least one loose contact. This is communicated through a CAN bus to other ECUs. In an embodiment, the resistances are determined again by the master control unit 140 even after the warning is communicated. In another embodiment, if any of the resistances determined by the master control unit 140 is lesser than the predetermined first threshold value, all faults related to the terminals are cleared and the resistances are determined again by the master control unit 140.
  • Figure 8 illustrates a schematic view of the second embodiment of the system 100 and the method 500 for diagnosing at least one loose contact in the battery pack 10.
  • the cell group 1 1 Ox may be connected as shown in Figure 4.
  • the current sensor 150 of the reference cell group 1 10x measures 504 a current flowing through the reference cell group 1 10x.
  • the current sensor 150 of the reference cell group 1 10x further communicates 506 the measured current to the master control unit 140.
  • the method 500 includes the step of communicating 512, by the slave control unit 160 of the reference cell group 110x, the measured voltage drops to the master control unit 140.
  • the master control unit 140 determines 526 resistance between the first contact terminal 1 12 of the reference cell group 110x and the last battery cell 120N of its preceding cell group 110x-i, based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. In another embodiment, the master control unit 140 determines 528 resistance between the second contact terminal 1 14 of the reference cell group 1 10x and the first battery cell 120i of its succeeding cell group 110x+i based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150.
  • the master control unit 140 If any of the one or more resistances determined by the master control unit 140 is greater than a predetermined first threshold value, the master control unit 140 generates 518 and communicates 518 a warning indicating at least one loose contact. In an embodiment, the resistances are determined again by the master control unit 140 even after the warning is communicated. In another embodiment, if any of the resistances determined by the master control unit 140 is lesser than the predetermined first threshold value, all faults related to the terminals are cleared and the resistances are determined again by the master control unit 140.
  • FIG. 9 illustrates a method 500 for diagnosing at least one loose contact in the battery pack 10, in accordance with a third embodiment of the present subject matter.
  • the slave control unit 160 of the reference cell group 1 1 Ox measures 532 a voltage drop across each battery cell 120 of the reference cell group 1 10x.
  • the slave control unit 160 of the reference cell group 1 10x further communicates 512 the measured voltage drops to the master control unit 140.
  • the master control unit 140 determines 536 resistance between each battery cell 120 of the reference cell group 1 10x based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150.
  • the method 500 includes the steps of generating 518 and communicating 518 by the master control unit 140, said warning indicating at least one loose contact, if any of the resistances determined is greater than a predetermined second threshold value.
  • the first threshold value and the second threshold value can be pre set to different values based on the nature and type of battery pack 10 in which the system 100 and method 500 are incorporated. In an embodiment, the first threshold value and the second threshold value are equal.
  • the present claimed invention provides a system for diagnosing at least one loose contact in a battery pack and a method thereof.
  • the battery pack finds application in high voltage systems such as a vehicle where the BMS/ Slave control unit may be with the battery pack and the master control unit may be one of the control units of the vehicle.
  • System and method determine the loose connection and the location of it in real-time and quickly to avoid any catastrophe to high voltage systems such as the vehicle.
  • the location of the loose contact can be accurately determined as each battery cell and terminal is hardwired to a slave control unit and the slave control unit along with the voltage drop passes the pins between which the voltage drop is sensed.
  • master control unit is aware of the voltage drops and their corresponding locations.
  • the claimed configurations of the system and method for diagnosing at least one loose contact in the battery pack as discussed above are not routine, conventional, or well understood in the art, as the claimed configurations of the system and method for diagnosing at least one loose contact in the battery pack enable the following solutions to the existing problems in conventional technologies.
  • it is possible to accurately measure loose contacts between individual battery cells and between cell groups or modules with minor changes to existing hardware of the battery pack. It is simple and cost effective to implement in battery packs. It also does not consume a lot of space and weighs less. Further, terminals electrically connected using bus bars which may get loosened under vibrations may be monitored by the given system and method. It also allows for early and timely detection of loose contact and accurate detection of contact loss. Temperature sensors may not be needed, so installation cost is less.

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  • General Physics & Mathematics (AREA)
  • Secondary Cells (AREA)
  • Tests Of Electric Status Of Batteries (AREA)
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  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

The present invention relates to a system for diagnosing at least one loose contact in a battery pack. The battery pack includes battery cells organised into cell groups with a first contact terminal and a second contact terminal. The system includes a current sensor and a slave control unit for each cell group. A master control unit determines resistance between the first contact terminal of a reference cell group and the second contact terminal of its preceding cell group and/or resistance between the second contact terminal of the reference cell group and the first contact terminal of its succeeding cell group based on measured voltage drop received from the slave control unit and measured current received from the current sensor. The master control unit generates and communicates a warning indicating at least one loose contact, if at least one of the resistances determined is greater than a predetermined threshold value.

Description

TITLE OF INVENTION
A SYSTEM FOR DIAGNOSING LOOSE CONTACT IN A BATTERY PACK
FIELD OF THE INVENTION
[001 ] The present invention generally relates to a battery pack and particularly relates to a system for diagnosing at least one loose contact in the battery pack and a method thereof.
BACKGROUND OF THE INVENTION
[002] A battery pack usually includes a plurality of battery modules or cell groups electrically interconnected with each other to produce desired current and voltage outputs. A battery module includes a plurality of battery cells interconnected to each other. The battery module achieves desired voltage by connecting several battery cells in series, such that each battery cell adds its voltage potential to derive the total terminal voltage. Similarly, the battery module achieves desired current by connecting several battery cells in parallel. If higher voltages or currents are needed and larger battery cells are not available or do not fit the design constraint, one or more battery cells can be connected in series or parallel to achieve the desired electrical output. Generally, the battery module employs a combination of series and parallel connections for its plurality of battery cells. This enables for design flexibility and achieves the desired voltage and current ratings with a standard battery cell size. Conventionally, the battery cell is provided with two cell tabs or terminals, one positive and other negative to connect the battery cell to another battery cell or to an external load. The aforementioned series and/or parallel connections between individual battery cells of the battery module are achieved by electrically connecting the cell tabs or terminals of different battery cells. Generally, a plurality of standard battery cells is employed in the battery modules used in various applications like automobiles, power tools, etc. The plurality of standard cylindrical battery cells is electrically interconnected with each other in a combination of series and parallel to achieve the desired electrical output. Alternatively, each of the battery modules of the battery pack may have a plurality of cell groups having a plurality of battery cells, all interconnected with each other.
[003] Conventionally, in applications involving the battery pack, the plurality of battery cells is connected together using connectors to the wiring harness in the vehicle. In high voltage applications, many battery cells are connected in series. Battery packs are also equipped with a BMS (Battery Management System) circuitry to monitor their health. A cluster of battery cells may share one common BMS circuitry, i.e., a group of modules or cell groups can have the same common BMS circuitry.
[004] Loose contacts at the positive and negative terminals of individual battery cells or of battery modules can lead to safety concerns from the potential arcing at the loose joints. Early detection of these loose contacts and ascertainment of the magnitude of voltage loss at the contact terminals is very important to avoid catastrophic events. In conventional approaches, a plurality of temperature sensors is employed to detect loose contact at the terminals. The temperature sensors which are placed close to or on a connector cannot detect loose contact effectively as magnitude of electric current flowing through the connectors and heat distribution at connection joints influence the temperature rise. Further, arcing and momentary high heat losses at connection joints are difficult to detect using the temperature sensors. Also, temperature variation in electric connectors is a fairly slow process and thus will take time to reflect. Furthermore, when each connection between battery cells which constitute each battery module are monitored by temperature sensors, numerous such sensors will be required, costing space, weight and money in the application. Also, when temperature sensors are employed, it is not possible to detect the extent of contact loss or torque loss at the connection joints.
[005] Further, the BMS circuitry of a module or group of modules is capable of communicating with other BMS circuitries of other modules of the battery pack using a CAN bus. So, temperature variation measured at connection joints or terminals when communicated to a master controller of the battery pack will take a very long time before the measured values are communicated to the master controller and some instruction to remedy the fault is generated by the master controller. By this time damage would already have been done. Such unchecked loose contacts may turn catastrophic as the it encourages thermal runaway of the cells in the battery, if not addressed in time. BMS circuity of conventional battery packs are also not capable of interconnection of battery cells of its many battery modules.
[006] Another way of monitoring loose contact in the battery pack is by measuring current in electrical wires in connecting the battery cells and the battery modules of the battery pack. A decrease in current is indicative of some fault in electrical connection. But this method does not indicate the location of fault. Thus, localization of fault will again require the use of multiple temperature sensors. Yet another way of measuring loose contact at connection joints or terminals is to measure the voltage across the joint. If there is loose contact, there will be a voltage drop across the connection joint. Thus, by measuring voltage across each battery cell, voltage drop and consequently loose contact may be detected. BMS circuitry for individual battery cells having capability to monitor health of the cells and loose contact at contact joints is known. However, when battery cells are connected in series or when modules or groups of battery cells are connected in series it is not possible to measure voltage drop at the connection joints using existing BMS circuitries of the battery pack. [007] Thus, there is a need in the art for a system for diagnosing at least one loose contact in the battery pack and a method thereof which addresses at least the aforementioned problems and limitations.
SUMMARY OF THE INVENTION
[008] In one aspect, the present invention is directed to a system for diagnosing at least one loose contact in a battery pack. The battery pack includes a plurality of battery cells which are organised into a plurality of cell groups. Each cell group has a first contact terminal and a second contact terminal, such that the first contact terminal of a reference cell group is connected to the second contact terminal of its preceding cell group and the second contact terminal of the reference cell group is connected to the first contact terminal of its succeeding cell group. The system for diagnosing at least one loose contact in the battery pack includes a master control unit, a current sensor for each of the plurality of cell groups and a slave control unit for each of the plurality of cell groups. The current sensor of the reference cell group is adapted to measure a current flowing through the reference cell group and communicate the measured current to the master control unit. In an embodiment, the slave control unit of the reference cell group is adapted to measure a voltage drop across its first contact terminal and the second contact terminal of its preceding cell group, and a voltage drop across its second contact terminal and the first contact terminal of its succeeding cell group. In another embodiment, the slave control unit of the reference cell group is adapted to measure a voltage drop across its first contact terminal and the last battery cell of its preceding cell group, and a voltage drop across its second contact terminal and the first battery cell of its succeeding cell group. The slave control unit of the reference cell group is further adapted to communicate the measured voltage drops to the master control unit. In an embodiment, the master control unit is adapted to determine resistance between the first contact terminal of the reference cell group and the second contact terminal of its preceding cell group and/or the second contact terminal of the reference cell group and the first contact terminal of its succeeding cell group based on the measured voltage drop received from the slave control unit and measured current received from the current sensor. In another embodiment, the master control unit is adapted to determine resistance between the first contact terminal of the reference cell group and the last battery cell of its preceding cell group and/or resistance between the second contact terminal of the reference cell group and the first battery cell of its succeeding cell group based on the measured voltage drop received from the slave control unit and the measured current received from the current sensor. The master control unit generates and communicates a warning indicating at least one loose contact, if at least one of the resistances determined is greater than a predetermined first threshold value.
[009] In an embodiment, the warning which indicates at least one loose contact generated and communicated by the master control unit includes information about the contact terminal where the loose contact has occurred.
[010] In another embodiment, the slave control unit of the reference cell group is adapted to measure a voltage drop across each battery cell of the reference cell group, and communicate the measured voltage drops to the master control unit. In an embodiment, the master control unit is adapted to determine resistance between each battery cell of the reference cell group based on the measured voltage drop received from the slave control unit and the measured current received from the current sensor. The master control unit generates and communicates said warning indicating at least one loose contact and a location of the loose contact if any of the resistances determined is greater than a predetermined second threshold value.
[01 1 ] In yet another embodiment, each of the plurality of cell groups includes a plurality of temperature sensors which are adapted to measure temperatures at the first contact terminal and the second contact terminal of the corresponding cell group, and at one or both terminals of one or more of the battery cells of the corresponding cell group.
[012] In a further embodiment, the slave control units of the plurality of cell groups are adapted to communicate with each other and with the master control unit.
[013] In another aspect, the present invention is directed to a method for diagnosing at least one loose contact in a battery pack. The battery pack includes a plurality of battery cells which are organised into a plurality of cell groups. Each cell group has a first contact terminal and a second contact terminal, such that the first contact terminal of a reference cell group is connected to the second contact terminal of its preceding cell group and the second contact terminal of the reference cell group is connected to the first contact terminal of its succeeding cell group. The method for diagnosing at least one loose contact in the battery pack includes the steps of measuring by a current sensor of the reference cell group, a current flowing through the reference cell group and communicating the measured current to a master control unit. In an embodiment, the method includes the steps of measuring by a slave control unit of the reference cell group, a voltage drop across the first contact terminal of the reference cell group and the second contact terminal of its preceding cell group, and a voltage drop across the second contact terminal of the reference cell group and the first contact terminal of its succeeding cell group. In another embodiment, the method includes the steps of measuring by the slave control unit of the reference cell group a voltage drop across the first contact terminal of the reference cell group and the last battery cell of its preceding cell group, and a voltage drop across the second contact terminal of the reference cell group and the first battery cell of its succeeding cell group. The method includes the step of communicating by the slave control unit of the reference cell group, the measured voltage drops to the master control unit. The method further includes the steps of determining by the master control unit resistance between the first contact terminal of the reference cell group and the second contact terminal of its preceding cell group, and resistance between the second contact terminal of the reference cell group and the first contact terminal of its succeeding cell group based on the measured voltage drop received from the slave control unit and the measured current received from the current sensor. In another embodiment the method includes the steps of determining by the master control unit, resistance between the first contact terminal of the reference cell group and the last battery cell of its preceding cell group, and resistance between the second contact terminal of the reference cell group and the first battery cell of its succeeding cell group based on the measured voltage drop received from the slave control unit and the measured current received from the current sensor. The method includes the steps of generating and communicating by the master control unit, a warning indicating at least one loose contact, if at least one of the resistances determined is greater than a predetermined first threshold value.
[014] In an embodiment, the method includes the steps of measuring by the slave control unit of the reference cell group, voltage drop across each battery cell of the reference cell group, and communicating by the slave control unit of the reference cell group, the measured voltage drops to the master control unit. The method further includes the steps of determining by the master control unit, resistance between each battery cell of the reference cell group based on the measured voltage drop received from the slave control unit and the measured current received from the current sensor, and generating and communicating by the master control unit, said warning indicating at least one loose contact, if any of the resistances determined is greater than a predetermined second threshold value. BRIEF DESCRIPTION OF THE DRAWINGS
[015] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 illustrates a block diagram of an exemplary system for diagnosing at least one loose contact in a battery pack, in accordance with an embodiment of the present invention.
Figure 2 illustrates a schematic view of an exemplary reference cell group of the system for diagnosing at least one loose contact in the battery pack, in accordance with an embodiment of the present invention.
Figure 3 illustrates a schematic view of two cell groups of the system for diagnosing at least one loose contact in the battery pack, in accordance with a first embodiment of the present invention.
Figure 4 illustrates a schematic view of two cell groups of the system for diagnosing at least one loose contact in the battery pack, in accordance with a second embodiment of the present invention.
Figure 5 illustrates a method for diagnosing at least one loose contact in the battery pack, in accordance with the first embodiment of the present invention.
Figure 6 illustrates another method for diagnosing at least one loose contact in the battery pack, in accordance with the second embodiment of the present invention.
Figure 7 illustrates a schematic view of the system and method for diagnosing at least one loose contact in the battery pack, in accordance with the first embodiment of the present invention. Figure 8 illustrates another schematic view of the system and method for diagnosing at least one loose contact in the battery pack, in accordance with the second embodiment of the present invention.
Figure 9 illustrates another method for diagnosing at least one loose contact in the battery pack, in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[016] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder. In the ensuing exemplary embodiments, the battery pack is illustrated as being constituted of cell groups connected in series. However, it is contemplated that the disclosure in the present invention may be applied to any type of battery pack capable of accommodating the present subject matter without defeating the scope of the present invention.
[017] The present invention generally relates to a battery pack and particularly relates to a system for diagnosing at least one loose contact in the battery pack and a method thereof.
[018] Figure 1 illustrates a block diagram of an exemplary system 100 for diagnosing at least one loose contact in a battery pack 10, in accordance with an embodiment of the present subject matter. The battery pack 10 includes a plurality of cell groups 1 10. In an embodiment, each cell group 110 is an individual battery module. In another embodiment, each cell group 1 10 is a group of cells in a battery module. Each of the plurality of cell groups 1 10 are constituted of a plurality of battery cells 120. Each battery cell 120 has one positive terminal and one negative terminal. The battery cells 120 of each cell group 1 10 are electrically interconnected with each other using any connection means known in the art like thin copper wires. The plurality of cell groups 1 10 of the battery pack 10 are further electrically and communicatively interconnected with each other. For purposes of explanation a cell group 110 has been selected as a reference cell group 1 1 Ox. The reference cell group 1 10x can be any cell group 110. The cell groups 1 10 preceding the reference cell group 11 Ox has been indicated as 110x-1, 11 Ox-2, etc. and the cell groups 1 10 succeeding the reference cell group 110x has been indicated as 1 10x+i , 1 1 Ox+2, etc. The system 100 includes a master control unit 140, current sensors 150 and slave control units 160. Each of the plurality of cell groups 1 10 is provided with one current sensor 150. The current sensor 150 of the reference cell group 1 10x is adapted to measure a current flowing through the reference cell group 110x and communicate the measured current to the master control unit 140. In an embodiment, a single current sensor 150 may be employed for all the cell groups 1 10.
[019] Figure 2 illustrates a schematic view of an exemplary reference cell group 1 10x of the system 100 for diagnosing at least one loose contact in the battery pack 10, in accordance with an embodiment of the present subject matter. Each cell group 1 10 has a first contact terminal 1 12 and a second contact terminal 114. In the illustrated embodiment, the first contact terminal 1 12 of the reference cell group 1 10x is connected to the second contact terminal 1 14 of its preceding cell group 1 10x-i. The second contact terminal 1 14 of the reference cell group 1 10x is connected to the first contact terminal 112 of its succeeding cell group 110x+i. Thus, the cell groups 110 in the battery pack 10 are connected in series. Each of the plurality of cell groups 1 10 is provided with one slave control unit 160. In an embodiment, each slave control unit 160 constitutes a BMS (Battery Management System) ASIC (Application Specific Integrated Circuit). In another embodiment the slave control units 160 constitute a CMU (Battery Cell Management Unit). The slave control unit 160 is capable of measuring voltages across each of the battery cells 120 in the cell group 1 10. The slave control unit 160 has input pins that are hardwired to be connected at the positive terminal of each of the battery cells 120 and negative terminal of the last battery cell 120N in the cell group 1 10. The first contact terminal 1 12 is connected to or is the same as the positive terminal of the first battery cell 120i in the cell group 1 10 and the second contact terminal 114 is connected to or is the same as the negative terminal of the last battery cell 120N in the cell group 1 10. By virtue of the hardwired connections between the positive and negative terminals of the battery cells 120 and the pins of the slave control unit 160, the slave control unit 160 senses voltages available at each of the hardwired points and based on the sensed voltages, the slave control unit 160 computes the voltage drop across the hardwired points. In an embodiment, the slave control unit 160 may transmit all the sensed voltages to the master control unit 140 and the master control unit 140 computes the voltage drops across these hardwired points. Also, in an embodiment, the slave control unit 160 passes the voltage drops to the master control unit 140 along with the pin numbers across which the voltage drop was determined. Thus, the master control unit 140 is aware of the voltage drops at the hardwired points and the slave control unit 160 identifier transmitting the voltage drops to localise the location of the loose contact based on the methods described in Figures 5 and 6.
[020] Figure 3 illustrates a schematic view of two cell groups 1 1 Ox and 1 10x-1 of the system 100 for diagnosing at least one loose contact in the battery pack 10, in accordance with a first embodiment of the present subject matter. In the illustrated embodiment, the slave control unit 160 of the reference cell group 1 10x is adapted to measure a voltage drop across its first contact terminal 1 12 and the second contact terminal 1 14 of its preceding cell group 1 10x-i . The slave control unit 160 of the reference cell group 1 10x is further adapted to measure a voltage drop across its second contact terminal 114 and the first contact terminal 1 12 of its succeeding cell group 1 10x+i . In the first embodiment, the slave control unit 160 has input pins that are hardwired to be connected at the first contact terminal 1 12 of the reference cell group 1 10xand the second contact terminal 1 14 of its preceding cell group 1 10x-i , and/or the second contact terminal 1 14 of the reference cell group 1 1 Ox and the first contact terminal 1 12 of its succeeding cell group 110x+i respectively..
[021 ] Figure 4 illustrates a schematic view of two exemplary reference cell groups 1 10x and 1 10x-1 of the system 100 for diagnosing at least one loose contact in the battery pack 10, in accordance with a second embodiment of the present subject matter. In the illustrated embodiment, the slave control unit 160 of the reference cell group 1 1 Ox is adapted to measure a voltage drop across its first contact terminal 1 12 and the last battery cell 120N of its preceding cell group 110x-i. The slave control unit 160 of the reference cell group 11 Ox is further adapted to measure a voltage drop across its second contact terminal 1 14 and the first battery cell 120i of its succeeding cell group 110x+i. In the second embodiment, the slave control unit 160 has input pins that are hardwired to be connected at the first contact terminal 1 12 of the reference cell group 1 10x and the last battery cell 120N of its preceding cell group 110x-i, and/or the second contact terminal 1 14 of the reference cell group 11 Ox and the first battery cell 120i of its succeeding cell group 1 10x+i respectively.
[022] Referring to Figures 3 and 4, the slave control unit 160 of the reference cell group 1 10x is adapted to measure a voltage drop across each battery cell 120 of the reference cell group 1 10x. In an embodiment, the voltage measurements are taken by tapping for voltage the corresponding first contact terminal 1 12 or second contact terminal 1 14 of the respective cell groups 1 10, or the corresponding positive or negative terminals of the respective battery cells 120, as the case may be, using any conventional voltage tapping means like thin copper wire connections. In another embodiment, the voltage drop is detected by monitoring the voltage drop in the electric wires connecting the battery cells 120 or the cell groups 1 10 as the case may be. For this, existing elements of a BMS of the battery pack 10 can be used without adding any extra circuits. In an embodiment, one among many existing cell voltage monitoring channels of the BMS ASIC of the battery pack 10 can be used to detect the voltage drops. These measurements are fairly accurate with less than ±2 mV error and are faster to detect within around 100 milliseconds. The measurement of voltage drop is not influenced by temperature variations in the battery pack 10.
[023] The slave control unit 160 of the reference cell group 1 10x is further adapted to communicate the measured voltage drops to the master control unit 140. In an embodiment, the slave control units 160 of the plurality of cell groups 1 10 are adapted to communicate with each other and with the master control unit 140. The communication may be enabled by a CAN bus of the battery pack 10. In another embodiment, each of the plurality of cell groups 110 includes a plurality of temperature sensors 170. The plurality of temperature sensors 170 is adapted to measure temperatures at the first contact terminal 112 and the second contact terminal 1 14 of the corresponding cell group 1 10. In yet another embodiment, the plurality of temperature sensors 170 are provided at one or both terminals of one or more of the battery cells 1 10 of the corresponding cell group 1 10. Thus, the temperature sensors can measure temperature at the positive and negative terminals of the battery cells 120 of each cell group 110. Use of typical analog circuits to detect accurately the voltage drop (in the order of mV) is limited due to limited accuracy in measuring the high voltages at the first and second contact terminals 112, 1 14 of the cell groups 1 10 to arrive at their difference. Therefore, in an embodiment, the temperature sensors 170 are placed on or in the vicinity of the first and second contact terminals 1 12, 114 to measure temperature changes. In another embodiment, the temperature sensors placed in the vicinity of the positive and negative terminals of the plurality of battery cells 120 aids in more accurate measurement of voltage drop between the battery cells.
[024] Figure 5 illustrates a method 500 for diagnosing at least one loose contact in the battery pack 10, in accordance with the first embodiment of the present subject matter. In the illustrated embodiment, the slave control unit 160 of the reference cell group 1 1 Ox measures 508 the voltage drop across its first contact terminal 112 and the second contact terminal 1 14 of its preceding cell group 1 10x-i. The slave control unit 160 of the reference cell group 110x also measures 510 the voltage drop across its second contact terminal 1 14 and the first contact terminal 112 of its succeeding cell group 1 10x+i. For doing this measurement, the cell group 11 Ox may be connected as shown in Figure 3. Referring to Figures 3 and 5, the current sensor 150 of the reference cell group 11 Ox measures 504 a current flowing through the reference cell group 1 10x. The current sensor 150 of the reference cell group 1 10x further communicates 506 the measured current to the master control unit 140. The method 500 includes the step of communicating 512, by the slave control unit 160 of the reference cell group 1 10x, the measured voltage drops to the master control unit 140. In an embodiment, the master control unit 140 determines 514 resistance between the first contact terminal 1 12 of the reference cell group 1 10x and the second contact terminal 114 of its preceding cell group 1 10x-i, based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. In another embodiment, the master control unit 140 determines 516 resistance between the second contact terminal 114 of the reference cell group 1 10x and the first contact terminal 1 12 of its succeeding cell group 1 10x+i based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. If any of the one or more resistances determined by the master control unit 140 is greater than a predetermined first threshold value, the master control unit 140 generates 518 and communicates 518 a warning indicating at least one loose contact.
[025] Figure 6 illustrates another method 500 for diagnosing at least one loose contact in the battery pack 10, in accordance with the second embodiment of the present subject matter. In the illustrated embodiment, the slave control unit 160 of the reference cell group 1 1 Ox measures 522 the voltage drop across its first contact terminal 1 12 and the last battery cell 120N of its preceding cell group 1 10x-i. The slave control unit 160 of the reference cell group 110x also measures 524 the voltage drop across its second contact terminal 1 14 and the first battery cell 120i of its succeeding cell group 1 10x+i. For doing this measurement, the cell group 1 10x may be connected as shown in Figure 4. Referring to Figures 4 and 6, the current sensor 150 of the reference cell group 1 10x measures 504 a current flowing through the reference cell group 11 Ox. The current sensor 150 of the reference cell group 1 10x further communicates 506 the measured current to the master control unit 140. The method 500 includes the step of communicating 512, by the slave control unit 160 of the reference cell group 1 1 Ox, the measured voltage drops to the master control unit 140. In an embodiment, the master control unit 140 determines 526 resistance between the first contact terminal 112 of the reference cell group 1 10x and the last battery cell 120N of its preceding cell group 1 10x-i, based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. In another embodiment, the master control unit 140 determines 528 resistance between the second contact terminal 1 14 of the reference cell group 1 10x and the first battery cell 120i of its succeeding cell group 110x+i based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. If any of the one or more resistances determined by the master control unit 140 is greater than a predetermined first threshold value, the master control unit 140 generates 518 and communicates 518 a warning indicating at least one loose contact.
[026] With increase in loose contact at the respective terminals, i.e., when loosening of contact at the terminals increases or the distance between the electrical connectors and the respective terminals increase, the resistance at these points also increases correspondingly. In an embodiment, the warning generated and communicated by the master control unit 140 comprises information about the contact terminal 1 12, 1 14 where the loose contact has occurred. The warning may be displayed on a display device 180 (shown in Figure 1 ) or screen for a user of the appliance using the battery to view and/or may be directly communicated to the service station. The display device includes an instrument cluster of a vehicle employing the batter pack 10, a personal mobile device, a personal computer, a dedicated screen on the battery pack 10, a computer device at the service station and the like. The warning may also be communicated to the BMS or an ECU (Electronic Control Unit) which may turn off the faulty cell group 1 10. In the embodiment illustrated in Figure 6, the master control unit 140 is able to receive the voltage drop across the first contact terminal 1 12 of the reference cell group 1 10x and the last battery cell 120N of its preceding cell group 1 10x-i and/or the voltage drop across the second contact terminal 1 14 of the reference cell group 1 10x and the first battery cell 120i of its succeeding cell group 110x+i , inclusive of the voltages of the respective battery cells 120i, 120N. Since the individual voltages of the respective battery cells 120i, 120N are also known to the master control unit 140, it can estimate and localize the voltage drop across the connectors.
[027] Figure 7 illustrates a schematic view of the first embodiment of the system 100 and method the 500 for diagnosing at least one loose contact in the battery pack 10. For doing this measurement, the cell group 1 1 Ox may be connected as shown in Figure 3. The current sensor 150 of the reference cell group 1 1 Ox measures 504 a current flowing through the reference cell group 1 10x. The current sensor 150 of the reference cell group 1 10x further communicates 506 the measured current to the master control unit 140. The method 500 includes the step of communicating 512, by the slave control unit 160 of the reference cell group 110x, the measured voltage drops to the master control unit 140. In an embodiment, the master control unit 140 determines 526 resistance between the first contact terminal 1 12 of the reference cell group 110x and the last battery cell 120N of its preceding cell group 110x-i, based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. In another embodiment, the master control unit 140 determines 528 resistance between the second contact terminal 1 14 of the reference cell group 1 10x and the first battery cell 120i of its succeeding cell group 110x+i based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. If any of the one or more resistances determined by the master control unit 140 is greater than a predetermined first threshold value, the master control unit 140 generates 518 and communicates 518 a warning indicating at least one loose contact. This is communicated through a CAN bus to other ECUs. In an embodiment, the resistances are determined again by the master control unit 140 even after the warning is communicated. In another embodiment, if any of the resistances determined by the master control unit 140 is lesser than the predetermined first threshold value, all faults related to the terminals are cleared and the resistances are determined again by the master control unit 140.
[028] Figure 8 illustrates a schematic view of the second embodiment of the system 100 and the method 500 for diagnosing at least one loose contact in the battery pack 10. For doing this measurement, the cell group 1 1 Ox may be connected as shown in Figure 4. The current sensor 150 of the reference cell group 1 10x measures 504 a current flowing through the reference cell group 1 10x. The current sensor 150 of the reference cell group 1 10x further communicates 506 the measured current to the master control unit 140. The method 500 includes the step of communicating 512, by the slave control unit 160 of the reference cell group 110x, the measured voltage drops to the master control unit 140. In an embodiment, the master control unit 140 determines 526 resistance between the first contact terminal 1 12 of the reference cell group 110x and the last battery cell 120N of its preceding cell group 110x-i, based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. In another embodiment, the master control unit 140 determines 528 resistance between the second contact terminal 1 14 of the reference cell group 1 10x and the first battery cell 120i of its succeeding cell group 110x+i based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. If any of the one or more resistances determined by the master control unit 140 is greater than a predetermined first threshold value, the master control unit 140 generates 518 and communicates 518 a warning indicating at least one loose contact. In an embodiment, the resistances are determined again by the master control unit 140 even after the warning is communicated. In another embodiment, if any of the resistances determined by the master control unit 140 is lesser than the predetermined first threshold value, all faults related to the terminals are cleared and the resistances are determined again by the master control unit 140.
[029] Figure 9 illustrates a method 500 for diagnosing at least one loose contact in the battery pack 10, in accordance with a third embodiment of the present subject matter. In the illustrated embodiment, the slave control unit 160 of the reference cell group 1 1 Ox measures 532 a voltage drop across each battery cell 120 of the reference cell group 1 10x. The slave control unit 160 of the reference cell group 1 10x further communicates 512 the measured voltage drops to the master control unit 140. The master control unit 140 determines 536 resistance between each battery cell 120 of the reference cell group 1 10x based on the measured voltage drop received from the slave control unit 160 and the measured current received from the current sensor 150. The method 500 includes the steps of generating 518 and communicating 518 by the master control unit 140, said warning indicating at least one loose contact, if any of the resistances determined is greater than a predetermined second threshold value. The first threshold value and the second threshold value can be pre set to different values based on the nature and type of battery pack 10 in which the system 100 and method 500 are incorporated. In an embodiment, the first threshold value and the second threshold value are equal.
[030] Advantageously, the present claimed invention provides a system for diagnosing at least one loose contact in a battery pack and a method thereof. The battery pack finds application in high voltage systems such as a vehicle where the BMS/ Slave control unit may be with the battery pack and the master control unit may be one of the control units of the vehicle. System and method determine the loose connection and the location of it in real-time and quickly to avoid any catastrophe to high voltage systems such as the vehicle. The location of the loose contact can be accurately determined as each battery cell and terminal is hardwired to a slave control unit and the slave control unit along with the voltage drop passes the pins between which the voltage drop is sensed. Thus, master control unit is aware of the voltage drops and their corresponding locations. The claimed configurations of the system and method for diagnosing at least one loose contact in the battery pack as discussed above are not routine, conventional, or well understood in the art, as the claimed configurations of the system and method for diagnosing at least one loose contact in the battery pack enable the following solutions to the existing problems in conventional technologies. By employing the said system and method, it is possible to accurately measure loose contacts between individual battery cells and between cell groups or modules with minor changes to existing hardware of the battery pack. It is simple and cost effective to implement in battery packs. It also does not consume a lot of space and weighs less. Further, terminals electrically connected using bus bars which may get loosened under vibrations may be monitored by the given system and method. It also allows for early and timely detection of loose contact and accurate detection of contact loss. Temperature sensors may not be needed, so installation cost is less.
[031 ] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.
List of Reference Numerals: 10 - Battery pack
100 - System for diagnosing loose contact in a battery pack
110 - Plurality of cell groups
110x - A reference cell group
110x-i - A preceding cell group of the reference cell group 110x+i - A succeeding cell group of the reference cell group
112 - First contact terminal of a cell group
114 - Second contact terminal of a cell group
120 - Plurality of battery cells
140 - Master control unit 150 - Current sensor
160 - Slave control unit
170 - Plurality of temperature sensors
180 - Display device to display warning generated

Claims

CLAIMS:
1. A system (100) for diagnosing at least one loose contact in a battery pack (10), the battery pack (10) having a plurality of battery cells (120) organised into a plurality of cell groups (110), each cell group (110) having a first contact terminal (112) and a second contact terminal (114), wherein the first contact terminal (1 12) of a reference cell group (1 10x) being connected to the second contact terminal (1 14) of a preceding cell group (110x-i) and the second contact terminal (1 14) of the reference cell group (1 10x) being connected to the first contact terminal (112) of a succeeding cell group (1 10x+i), the system (100) comprising: a master control unit (140); a current sensor (150) for each of the plurality of cell groups (1 10), the current sensor (150) of the reference cell group (110x) being configured to measure a current flowing through the reference cell group (1 10x) and communicate the measured current to the master control unit (140); and a slave control unit (160) for each of the plurality of cell groups (110), the slave control unit (160) of the reference cell group (1 10x) being configured to: measure one or both of a voltage drop across its first contact terminal (112) and the second contact terminal (1 14) of its preceding cell group (110x-i ) ; and a voltage drop across its first contact terminal (112) and the last battery cell (120N) of its preceding cell group (110x-i) ; measure one or both of a voltage drop across its second contact terminal (114) and the first contact terminal (1 12) of its succeeding cell group (110x+i) and a voltage drop across its second contact terminal (1 14) and the first battery cell (120i) of its succeeding cell group (110x+i) ; communicate the measured voltage drops to the master control unit (140); wherein, the master control unit (140) being configured to: determine resistance between the first contact terminal (112) of the reference cell group (1 1 Ox) and the second contact terminal (1 14) of its preceding cell group (1 10x-i) based on the measured voltage drop received from the slave control unit (160) and the measured current received from the current sensor (150) and determine resistance between the second contact terminal (1 14) of the reference cell group (11 Ox) and the first contact terminal (1 12) of its succeeding cell group (1 10x+i) based on the measured voltage drop received from the slave control unit (160) and the measured current received from the current sensor (150); or determine resistance between the first contact terminal (112) of the reference cell group (1 1 Ox) and the last battery cell (120N) of its preceding cell group (110x-i) based on the measured voltage drop received from the slave control unit (160) and the measured current received from the current sensor (150) and determine resistance between the second contact terminal (1 14) of the reference cell group (1 1 Ox) and the first battery cell (120i) of its succeeding cell group (1 10x+i) based on the measured voltage drop received from the slave control unit (160) and the measured current received from the current sensor (150) a voltage drop across its second contact terminal (1 14); and generate and communicate a warning on a display device (180) indicating at least one loose contact, if at least one of the resistances determined being greater than a predetermined first threshold value. The system (100) for diagnosing at least one loose contact in the battery pack (10) as claimed in claim 1 , wherein the warning generated and communicated by the master control unit (140) comprises information about the contact terminal (112, 1 14) where the loose contact has occurred. The system (100) for diagnosing at least one loose contact in the battery pack (10) as claimed in claim 1 , wherein the slave control unit (160) of the reference cell group (1 10x) being configured to: measure a voltage drop across each battery cell (120) of the reference cell group (1 10x); and communicate the measured voltage drops to the master control unit (140). The system (100) for diagnosing at least one loose contact in the battery pack (10) as claimed in claim 3, wherein the master control unit (140) being configured to: determine resistance between each battery cell (120) of the reference cell group (1 10x) based on the measured voltage drop received from the slave control unit (160) and the measured current received from the current sensor (150); generate and communicate said warning indicating at least one loose contact and a location of the loose contact if any of the resistances determined being greater than a predetermined second threshold value. The system (100) for diagnosing at least one loose contact in the battery pack (10) as claimed in claim 1 , wherein each of the plurality of cell groups (110) comprises a plurality of temperature sensors (170) configured to measure temperatures at the first contact terminal (1 12) and the second contact terminal (1 14) of the corresponding cell group (1 10), and at one or both terminals of one or more of the battery cells (1 10) of the corresponding cell group (1 10). The system (100) for diagnosing at least one loose contact in the battery pack (10) as claimed in claim 1 , wherein the slave control units (160) of the plurality of cell groups (1 10) being configured to communicate with each other and with the master control unit (140). A method (500) for diagnosing at least one loose contact in a battery pack (10), the battery pack (10) having a plurality of battery cells (1 10) organised into a plurality of cell groups (110), each cell group having a first contact terminal (112) and a second contact terminal (114), wherein the first contact terminal (112) of a reference cell group (1 10x) being connected to the second contact terminal (1 14) of a preceding cell group (1 10x-i) and the second contact terminal (1 14) of the reference cell group (1 10x) being connected to the first contact terminal (112) of a succeeding cell group (1 10x+i), the method (500) comprising the steps of: measuring (504), by a current sensor (150) of the reference cell group (1 1 Ox), a current flowing through the reference cell group (11 Ox) and communicating (506) the measured current to a master control unit (140); measuring (508, 522), by a slave control unit (160) of the reference cell group (110x), one or both of a voltage drop across the first contact terminal (112) of the reference cell group (1 1 Ox) and the second contact terminal (1 14) of its preceding cell group (1 10x-i) and a voltage drop across the first contact terminal (1 12) of the reference cell group (1 10x) and the last battery cell (120N) of its preceding cell group (110x-i); measuring (510, 524), by the slave control unit (160) of the reference cell group (1 10x), one or both of a voltage drop across the second contact terminal (1 14) of the reference cell group (11 Ox) and the first contact terminal (1 12) of its succeeding cell group (1 10x+i) and a voltage drop across the second contact terminal (1 14) of the reference cell group (1 10x) and the first battery cell (120i) of its succeeding cell group (1 10x+i); communicating (512), by the slave control unit (160) of the reference cell group (110x), the measured voltage drops to the master control unit (140); determining (514), by the master control unit (140), resistance between the first contact terminal (1 12) of the reference cell group (11 Ox) and the second contact terminal (1 14) of its preceding cell group (110x-i) based on the measured voltage drop received from the slave control unit (160) and the measured current received from the current sensor (150) and determining (516), by the master control unit (140), resistance between the second contact terminal (114) of the reference cell group (110x) and the first contact terminal (1 12) of its succeeding cell group (110x+i) based on the measured voltage drop received from the slave control unit (160) and the measured current received from the current sensor (150); or determining (526), by the master control unit (140), resistance between the first contact terminal (1 12) of the reference cell group (1 10x) and the last battery cell (120N) of its preceding cell group (1 10x-i) based on the measured voltage drop received from the slave control unit (160) and the measured current received from the current sensor (150) and determining (528), by the master control unit (140), resistance between the second contact terminal (114) of the reference cell group (1 10x) and the first battery cell (120i) of its succeeding cell group (110x+i) based on the measured voltage drop received from the slave control unit (160) and the measured current received from the current sensor (150); and generating (518) and communicating (518), by the master control unit (140), a warning indicating at least one loose contact, if at least one of the resistances determined being greater than a predetermined first threshold value. The method (500) for diagnosing at least one loose contact in the battery pack (10) as claimed in claim 7, wherein the method (500) comprising the steps of: measuring (532), by the slave control unit (160) of the reference cell group (110x), a voltage drop across each battery cell (120) of the reference cell group (1 10x); and communicating (512), by the slave control unit (160) of the reference cell group (110x), the measured voltage drops to the master control unit (140). The method (500) for diagnosing at least one loose contact in the battery pack (10) as claimed in claim 8, wherein the method (500) comprising the steps of: determining (536), by the master control unit (140), resistance between each battery cell (120) of the reference cell group (1 1 Ox) based on the measured voltage drop received from the slave control unit (160) and the measured current received from the current sensor (150); generating (518) and communicating (518), by the master control unit (140), said warning indicating at least one loose contact, if any of the resistances determined being greater than a predetermined second threshold value.
EP23761615.6A 2022-08-09 2023-08-08 A system for diagnosing loose contact in a battery pack Pending EP4569341A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IN202241045545 2022-08-09
PCT/IN2023/050759 WO2024033939A1 (en) 2022-08-09 2023-08-08 A system for diagnosing loose contact in a battery pack

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EP4569341A1 true EP4569341A1 (en) 2025-06-18

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EP (1) EP4569341A1 (en)
JP (1) JP2025525796A (en)
CN (1) CN119678061A (en)
WO (1) WO2024033939A1 (en)

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US10901019B2 (en) * 2013-03-15 2021-01-26 Atieva, Inc. Method of connecting cell voltage sensors
CN107153162B (en) * 2017-06-06 2019-07-26 山东大学 An online detection method for multiple faults of power battery pack
CN107861064B (en) * 2017-07-24 2024-05-07 广州微宏电源科技有限公司 Method for detecting electrical performance of multi-series power battery pack

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