[0001]The present subject matter described herein, relates to an electric vehicle. More particularly, the present subject matter provides a system and a method to detect loose connections between electric modules of an electric battery pack or traction battery pack.
BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] In electric vehicles, a traction battery pack is provided which is a primary energy source for providing energy for traction of vehicle. The traction battery pack has a battery string having a plurality of battery modules connected either in series or in parallel or in any combination with each other. A plurality of cells combined with each other to form a battery module and a plurality of battery modules combined with each other to form a battery pack or a traction battery pack. The traction battery pack generates a high voltage (HV) for traction of an electric motor of the electric vehicle. The traction battery pack can be controlled by the electronic modules, such as Electronic Control unit (ECU) or Vehicle control unit (VCU) from outside the traction battery pack, or can be controlled by electronic module Battery Management System (BMS) from inside the traction battery pack. The electronic module operates passive protection devices, such as contactor or relay to draw current from the traction battery pack. These electronic modules are also responsible for implementing various battery state estimations, such as State of Charge (SOC), State of Health (SOH), State of Function (SOF), State of Power (SOP), etc.

[0004] The Master Battery Management System (BMS) is provided to communicate with a plurality of slave BMS that are connected with the plurality of battery modules to collect the cell data of that module and transmit to Vehicle Control Unit (VCU) for further analysis.
[0005] In the battery module, a plurality of cells is welded with each other to form the battery module. In the traction battery pack, a plurality of battery modules are bolted with each other using a busbar (copper busbar) to form the traction battery pack. With running vibrations and/ or corrosion, there are high chances that bolted connections between the battery modules get loose, and resultantly increase the resistance between the battery modules which further reduces the efficiency of the traction battery pack.
[0006] Technical problem is to detect the loose connection between the battery modules accurately.
[0007] Existing technologies detect the loose connection between the battery modules of the traction battery pack that are dependent on the cell behaviour and environmental condition. In the existing method to detect the loose connection, a current is supplied to the battery and resistance of the traction battery pack is measured. Upon measuring the resistance, the measured resistance is compared with the threshold resistance value to determine whether there is any loose connection or not. The existing method depends on internal resistance of the cells that varies with state of health (SOH), temperature, and state of charge (SOC) conditions.
[0008] Aged cells give high resistance value as compared to new one. Similarly, with change in state of charge condition, resistance value of the battery module varies. As is known, with increase in temperature of cells, resistance of battery module decreases and with decrease in temperature of cells, resistance of the battery modules increases significantly.
[0009] Therefore, the existing method that senses the traction battery pack input voltage to measure the resistance of the battery pack to determine the loose

connection. With dependencies on cell behaviour and environmental condition and determining voltage drop and resistance increment in the traction battery pack, the existing method provides poor accuracy and may result in false measurements.
[0010] Further, the existing method detects only presence of loose connection, however does not detect location of the loose connection in the traction battery pack. As the traction battery pack comprises a plurality of battery modules. With the existing method, operator has to detect the location of the loose connection manually by checking each and every connection.
[0011] Therefore, there is a need of a system and a method that can detect the loose connection between the battery modules independently from the cell condition and also detect a location of the loose connection in the traction battery pack of the electric vehicle.
OBJECTS OF THE DISCLOSURE
[0012] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.
[0013] The principal object of the present invention is to provide a system and a method to detect loose connections between a plurality of battery modules of a traction battery pack.
[0014] Another object of the present invention is to provide a system and a method to detect loose connections between the plurality of battery modules independently from cell behaviour and environmental condition.
[0015] Another object of the present invention is to provide a system and a method that can detect location of the loose connection between the plurality of battery modules in the traction battery pack.
[0016] These and other objects and advantages will become more apparent when reference is made to the following description and accompanying drawings.

SUMMARY
[0017] This summary is provided to introduce concepts related to a system and a method to detect loose connection between a plurality of battery modules in a traction battery pack an electric vehicle. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0018] In an embodiment, the present subject matter relates to a system for detecting loose connection between a plurality of battery modules where two battery modules are connected by a busbar in a traction battery pack. The system comprising a differential analog to digital conversion (ADC) sensing unit and a loose connection detection unit. The differential ADC sensing unit is configured to measure voltage (Vc) across at least one cell in first battery module from the plurality of battery modules by closing switch (S2) and switch (S3) and measure voltage (VT) across the at least one cell in first battery module and the busbar connecting the first battery module and a second battery module including contacts of the first battery module and the second battery module by closing switch (S3) and switch (SI). The differential ADC sensing unit further determines the voltage difference between two conditions and calculates the resistance (CR) of the busbar and the contacts of the first battery module and the second battery module by using current flow. The loose connection detection unit detects loose connection between the first battery module and the second battery module when determined resistance (CR) is more than a predefined threshold resistance (RTH) of the busbar and the contacts of the first battery module and the second battery module in the traction battery pack.
[0019] In an aspect, the differential ADC sensing unit subtracts the measured voltage (Vc) from the measured voltage (VT) to determines the resistance of the busbar and the contacts of the first battery module and the second battery module.

[0020] In an aspect, the system is a slave battery management system where one slave-BMS is coupled to one battery module and each slave BMS is coupled to master-BMS.
[0021] In an aspect, the loose connection detection unit communicates the 5 detected loose connection between the first battery module and the second battery module to a master battery management system (BMS).
[0022] In an aspect, the differential ADC sensing unit measures the voltage (VC) and the voltage (VT) during constant current (CC) charge of the traction battery pack.
10 [0023] The present method detects loose connection between a plurality of battery modules connected by a busbar in a traction battery pack. The method comprising steps of: measuring, by a differential analog to digital conversion (ADC) sensing unit, voltage (VT) across at least one cell in first battery module and the busbar connecting the first battery module and a second battery module
15 including contacts of the first battery module and the second battery module by closing switch (S3) and switch (S1); measuring, by the differential analog to digital conversion (ADC) sensing unit, voltage (VC) across the at least one cell in the first battery module by connecting switch (S2) and switch (S3); determining, by the differential analog to digital conversion (ADC) sensing unit, resistance of
20 the busbar and contacts of the first battery module and the second battery module; and detecting a loose connection between the first battery module and the second battery module when determined resistance is more than a predefined threshold resistance (RTH) of the busbar and the contacts of the first battery module and the second battery module in the traction battery pack.
25 [0024] In an aspect, the differential ADC sensing unit measures the voltage (VC) and the voltage (VT) during constant charge (CC) of the traction battery pack.
[0025] In an aspect, the differential ADC sensing unit is implemented in a
slave battery management system (BMS).
6

[0026] In an aspect, the method further comprises communicating the detected loose connection between the first battery module and the second battery module to a master battery management system (BMS).
[0027] Various objects, features, aspects, and advantages of the inventive 5 subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The illustrated embodiments of the subject matter will be best 10 understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
15 [0029] Fig. 1 illustrates architecture of traction battery pack with slave battery management system coupled with each battery modules for detecting loose connection between the battery modules, in accordance with an embodiment of the present subject matter;
[0030] Fig. 2 illustrates architecture of slave BMS with battery modules and 20 master BMS, in accordance with an embodiment of the present subject matter; and
[0031] Fig. 3 illustrates a method for detecting loose connection between the battery modules in the traction battery pack, in accordance with an embodiment of the present subject matter.
25 [0032] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and
7

methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[0033] The detailed description of various exemplary embodiments of the 5 disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives 10 falling within the scope of the present disclosure as defined by the appended claims.
[0034] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, 15 and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a",” “an” and “the” are intended to include the
20 plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements,
25 components and/or groups thereof.
[0036] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may
8

sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0037] In addition, the descriptions of "first", "second", “third”, and the like in the present invention are used for the purpose of description only, and are not to 5 be construed as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Thus, features defining "first" and "second" may include at least one of the features, either explicitly or implicitly.
[0038] Unless otherwise defined, all terms (including technical and scientific 10 terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly 15 formal sense unless expressly so defined herein.
[0039] Non-limiting Definitions
[0040] In the disclosure hereinafter, one or more terms are used to describe various aspects of the present disclosure. For a better understanding of the present disclosure, a few definitions are provided herein for better understanding of the 20 present disclosure.
[0041] Master Battery Management System: A system which is any electronic system that manages a rechargeable battery (cell or battery pack), such as by protecting the battery from operating outside its safe operating area, monitoring its state, calculating secondary data, reporting that data, controlling its environment, 25 authenticating it and / or balancing it.
[0042] Slave Battery Management System: A system which is any electronic system that manages a plurality of cells in a battery module such as by detecting
9

state of health (SOH), temperature, and state of charge (SOC) condition and communicating the conditions of the plurality of cells to master BMS.
[0043] Failsafe condition: The condition when circuit path between the plurality of battery modules of a traction battery pack is broken.
5 [0044] Low voltage: 12V
[0045] High voltage: 60V or more
[0046] Switches: Switches can be PCB mounted MOSFETS or relays.
[0047] Differential Analog to Digital Converter (ADC) sensing: Differential ADC measures the voltage difference between two points while converting analog 10 signals into digital signals.
[0048] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise 15 various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0049] Technical problem: In the existing traction battery pack, when there is any loose connection between any two battery modules, the resistance of complete traction battery pack is measured along with internal resistance of the 20 cells to determine possibility of loose connection in the battery pack and then to manually locate loose connections in the traction battery pack.
[0050] Exemplary Implementations
[0051] In the present disclosure, first battery module and second battery module may indicate any two adjacent battery modules in a plurality of battery 25 modules which are connected in a series by a busbar in traction battery pack.
[0052] To this, as shown in fig. 1, a system for a traction battery pack 100 for an electric vehicle is explained. The system comprises a traction battery pack 100
10

and a plurality of battery modules 101, 103, a plurality of slave battery management system (BMS) 102, 104. In the traction battery pack 100, one slave BMS is connected to one battery module to detect all the health conditions of the battery module and communicate the same to a master BMS of the traction battery
5 pack 100 for further processing. The master BMS further connected with the vehicle control unit (VCU) (not shown) that takes final decisions on the traction battery pack 100 based on the inputs received from the master BMS. The output of the traction battery pack 100 is connected with high voltage (HV) connector to operate the electric vehicle. The vehicle control unit (VCU) is coupled to an
10 auxiliary battery and the traction battery pack 100. The traction battery pack 100 comprises a master battery management system (BMS) 400 (shown in fig. 2) that is coupled with a plurality of slave BMS 200 (shown in fig. 2) to check safety functions of a plurality of battery modules 300 (shown in fig. 2).
[0053] Each of the slave BMS from the plurality of slave BSM 102, 104 is 15 connected to a battery module. The battery module 101, 103 comprises a plurality of cells 101a, 103a connected in a series. The plurality of battery modules is connected in series to form a traction battery pack 100. Further, the two battery modules are bolted at contacts 101b, 103b by a busbar 105 that is made of metal material, preferably, copper metal. The busbar 105 may vary in length and 20 accordingly, resistance of the busbar 105 varies. Each slave BMS 102, 104 has a cell voltage (CV) sensing unit and a differential analog to digital conversion (ADC) unit 102a, 104a. The differential ADC unit 102a, 104a coupled with two adjacent battery modules 101, 103 connected by the busbar 105.
[0054] To explain working of system, working of one slave BMS 102 is 25 explained in reference to two battery modules 101, 103 to detect loose connection between them. The differential ADC unit 102a is coupled with at least one cell 101a of first battery module 101 from the plurality of battery modules via a pair of switch S2 and S3 to measure voltage ‘VC’ across the atleast one cell 101a.
11

[0055] During constant current (CC) charging of the traction battery pack 100, the differential ADC unit 102a closes the normally opened (N/O) switch ‘S2’ and the normally opened (N/O) switch ‘S3’ provided across the atleast one cell 101a to measure the voltage ‘VC’ by passing contact current for short period of time, 5 for example, 10ms. The measured voltage ‘VC’ includes voltage of cell during that time period and noise in the cell. Further, other cell characteristics remain constant for such as small time period.
r £ "* ■ f^rr * fTifftfH ii i ii i ii i m ii i ii i ii i ii i ii i ii i ■ i ii i ii i ■ £ tfvtvttitiffc L
10 [0056] As shown in the fig. 1, the differential ADC unit 102a (201 of fig. 2) is also coupled with at least one cell 101a of first battery module 101 and the second battery module 103 across the busbar 105 which connects the first battery module 101 and the second battery module 103 by joining the contacts 101b, 103b of the first battery module 101 and the second battery module 103, respectively. The
15 differential ADC unit 102a measures voltage ‘VT’ across the at least one cell 101a in the first battery module 101 and the busbar 105 connecting the first battery module 101 and the second battery module 103 including contacts of the first battery module 101 and the second battery module 103 by closing the normally opened (N/O) switch ‘S3’ and the normally opened (N/O) switch ‘S1’ during
20 constant current (CC) charging of the traction battery pack 100 for a short time period, for example, 10ms. The measured voltage ‘VT’ includes voltage of cell during that time period, noise in the cell, voltage across busbar, and voltage across contacts.
YT - Y^ii + tffffrs + YgsstHT + YtcstoMB serctfitaff 2
25 [0057] Considering fig. 1 and fig. 2 together, upon measuring the voltage ‘VT’ and the voltage ‘VC’ the differential ADC sensing unit 102a (201 of fig. 2) determines resistance of the busbar 105 joining the first battery module 101 and the second battery module 103 and the contacts 101b, 103b of the first and second
12

battery module 101, 103 joining the busbar 105. The differential ADC sensing unit 102a subtracts the measured voltage ‘VC’ from the measured voltage ‘VT’ to determine the voltage of across the busbar 105 and the contacts 101b, 103b.

5

w - fort + net™ + rAri»F + U^ - {v*t + * <«


M-2
Where CR is resistance and I is constant current during CC charging of the traction battery pack 100.
10 [0058] The differential ADC unit 102a determines resistance (CR) of the busbar 105 and the contacts 101b, 103b of the first battery module 101 and the second battery module 103.
[0059] As shown in the fig. 2, the loose connection detection unit 202 detects loose connection between the first battery module 101 and the second battery
15 module 103 when determined resistance ‘CR’ is more than a predefined threshold resistance ‘RTH’ of the busbar 105 and the contacts 101b, 103b of the first battery module 101 and the second battery module 103 in the traction battery pack 100. Each slave BMS 102 (200 of fig. 2) comprises a memory to store the predefined threshold resistance for each busbar provided between two adjacent battery
20 modules and their corresponding contacts. Further, length of busbar can vary accordingly, their resistance can vary. Therefore, the slave BMS 102 corresponding to the busbar has a predefined threshold value which is used to detect the loose connection corresponding battery modules.
[0060] Referring to fig. 2, the slave BMS 200 is coupled to a master BMS 300
25 to communicate the detected loose connection between the first battery module
13

101 and the second battery module 103. The master BMS 300 further communicates the detected loose connection condition to the VCU to indicate the same to display device of the vehicle to inform operator of the vehicle about the condition and also displays location of the detected loose connection.
5 [0061] In another embodiment, the master BMS 400 logs the location of the detected loose connection based on the inputs received from the slave BMS 200. For example, the slave BMS 200 of the battery module 1 indicates the loose connection and logs the corresponding signal into the master BMS 400. During servicing of the traction battery pack, the service operator locate the location of
10 the loose connection based on the signal logged by the slave BMS 200 as each signal has an identification number corresponding to the slave BMS which directs to corresponding battery module. For example, if a battery pack has 10 battery modules, there are 10 slave BMS which are coupled to the 10 battery modules. Accordingly, based on the logged signal of the slave BMS, the signal indicates the
15 location of the loose connection between the corresponding battery modules.
[0062] Referring to fig. 3 a method for detecting a loose connection between two battery modules independently from cell behaviour and environmental conditions during constant current (CC) charge condition of traction battery pack 100. The method comprising:
20 [0063] Measuring 302, by a differential analog to digital conversion (ADC) sensing unit 102a, voltage (VT) across at least one cell 101a in first battery module 101 and busbar 105 connecting the first battery module 101 and a second battery module 103 including contacts 101b, 103b of the first battery module 101 and the second battery module 103 by closing switch (S3) and switch (S1).
25 [0064] Measuring 304, by the differential analog to digital conversion (ADC) sensing unit 102a, voltage (VC) across the at least one cell 101a in the first battery module 101 by connecting switch (S2) and switch (S3).
[0065] The method steps 302 and 304 can be performed in any sequence, for
example, measuring 304 of the voltage (VC) performed before method steps 302.
14

[0066] Determining 306, by the differential analog to digital conversion (ADC) sensing unit 102a, resistance of the busbar 105 and contacts 101b, 103b of the first battery module 101 and the second battery module 103; and
[0067] Comparing 308, the determined resistance ‘CR’ with a predefined 5 threshold in the slave BMS.
[0068] Detecting 310, a loose connection between the first battery module 101 and the second battery module 103 when determined resistance ‘CR’ is more than the predefined threshold resistance ‘RTH’ of the busbar 105 and the contacts 101b, 103b of the first battery module 101 and the second battery module 103 in the 10 traction battery pack 100.
[0069] The differential ADC sensing unit 102a measures the voltage (VC) and the voltage (VT) during constant charge (CC) charging of the traction battery pack 100. In an aspect, the differential ADC sensing unit is implemented in a slave battery management system (BMS).
15 [0070] The method further comprises communicating the detected loose connection between the first battery module 101 and the second battery module 103 to a master battery management system (BMS).
[0071] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended
20 claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such
25 an intent will be explicitly recited in the claim, and in the absence of such
recitation no such intent is present. For example, as an aid to understanding, the
following appended claims may contain usage of the introductory phrases “at least
one” and “one or more” to introduce claim recitations. However, the use of such
phrases should not be construed to imply that the introduction of a claim recitation
15

by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."
[0072] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the

claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

We claim:

A system (102, 104, 200) for detecting loose connection between a plurality of battery modules (101, 103) where two battery modules (101, 103) are connected by a busbar (105) in a traction battery pack (100), the system (102, 104, 200) comprising:
a differential analog to digital conversion (ADC) sensing unit (102a) to:
measure voltage (Vc) across at least one cell (101a) in first battery module (101) from the plurality of battery modules (101, 103) by closing switch (S2) and switch (S3);
measure voltage (VT) across the at least one cell (101a) in the first battery module (101) and the busbar (105) connecting the first battery module (101) and a second battery module (103) including contacts (101b, 103b) of the first battery module (101) and the second battery module (103) by closing switch (S3) and switch (SI);
determine resistance (CR) of the busbar (105) and the contacts (101b, 103b) of the first battery module (101) and the second battery module (103); and a loose connection detection unit (202) to:
detect loose connection between the first battery module (101) and the second battery module (103) when determined resistance (CR) is more than a predefined threshold resistance (RTH) of the busbar (105) and the contacts (101b, 103b) of the first battery module (101) and the second battery module (103) in the traction battery pack (100).
The system (102, 104, 200) as claimed in claim 1, wherein the differential ADC sensing unit (102a) subtracts the measured voltage (Vc) from the measured voltage (VT) to determines the resistance (CR) of the busbar (105) and the contacts (101b, 103b) of the first battery module (101) and the second battery module (103).

The system (102, 104, 200) as claimed in claim 1, wherein the system (102,
104, 200) is a slave battery management system (102, 104, 200) where one
slave BMS is coupled to one battery module and each slave BMS (102, 104,
200) is coupled to a master battery management system (400).
The system (102, 104, 200) as claimed in claim 1, wherein the loose
connection detection unit (202) communicates the detected loose connection
between the first battery module (101) and the second battery module (105)
to a master battery management system (400).
The system (102, 104, 200) as claimed in claim 1, wherein the differential
ADC sensing unit (102a) measures the voltage (Vc) and the voltage (VT)
during constant current (CC) charge of the traction battery pack (100).
A method for detecting loose connection between a plurality of battery modules (101, 103) connected by a busbar (105) in a traction battery pack (100), the method comprising:
measuring (302), by a differential analog to digital conversion (ADC) sensing unit (102a), voltage (VT) across at least one cell (101a) in first battery module (101) and the busbar (105) connecting the first battery module (101) and a second battery module (103) including contacts (101b, 103b) of the first battery module (101) and the second battery module (103) by closing switch (S3) and switch (SI);
measuring (304), by the differential analog to digital conversion (ADC) sensing unit (102a), voltage (Vc) across the at least one cell (101a) in the first battery module (101) by closing switch (S2) and switch (S3);
determining (306), by the differential analog to digital conversion (ADC) sensing unit (102a), resistance (CR) of the busbar (105) and contacts (101b, 103b) of the first battery module (101) and the second battery module (103); and

detecting, (310) a loose connection between the first battery module (101) and the second battery module (103) when determined resistance (CR) is more than a predefined threshold resistance (RTH) of the busbar (105) and the contacts (101b, 103b) of the first battery module (101) and the second battery module (103) in the traction battery pack (100).
The method as claimed in claim 6, wherein the differential ADC sensing
unit (102a) measures the voltage (Vc) and the voltage (VT) during constant
current (CC) charge of the traction battery pack (100).
The method as claimed in claim 6, wherein the differential ADC sensing
unit (102a) is implemented in a slave battery management system (102, 104,
200).
The method as claimed in claim 6, wherein the method further comprises
communicating the detected loose connection between the first battery
module (101) and the second battery module (103) to a master battery
management system (400).