TECHNICAL FIELD
[0001] The present subject matter described herein, relates to an electric vehicle. More particularly, the present subject matter provides a traction battery pack and a method to detect un-authorized opening of cover of the traction battery pack when auxiliary low voltage is disconnected, for example, 12V supply source is disconnected.
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 comprising of 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 for traction 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 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 of the plurality of battery modules to collect the cell data and optionally transmit the same to vehicle control unit (VCU) for further analysis and protection functions. Further, the protection functions are controlled by the VCU only, master BMS only, or in combination by the VCU and the master BMS.
[0005] The traction battery pack supplies high current for traction of vehicle. The VCU or the master MBS controls the output of the traction battery pack.
[0006] Technical problem existing with traction battery pack is detection of un-authorized access of the traction battery pack.
[0007] Existing technologies do detect the un-authorized access of the traction battery pack and log the same into the memory for further processing. However, the disadvantage associated with the existing technologies is that a low voltage supply is required for detection and logging. With the existing technologies, the un-authorized access can be detected only when the traction battery pack is coupled with auxiliary battery supplying low voltage for functioning of the master BMS or battery open detection circuitry. In case of deliberate or accidental disconnection of the auxiliary battery supply, the existing technologies do not detect the un-authorized access of the traction battery pack or opening of the cover of the traction battery pack.
[0008] To change the battery modules, generally, the traction battery pack is disassembled from the vehicle by disconnecting all connections with VCU and the auxiliary battery. In this case, it becomes cumbersome to detect authorized or un¬authorized access of the traction battery pack.
[0009] Therefore, there is a need of a circuit for a traction battery pack and a method thereof that can detect authorized or un-authorized access of the traction battery pack even when the complete low voltage supply source is disconnected from BMS, VCU or traction battery pack.

OBJECTS OF THE DISCLOSURE
[0010] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.
[0011] The principal object of the present invention is to provide a system for supplying low voltage to master battery management system (BMS) in the traction battery pack from a plurality of battery cells.
[0012] Another object of the present invention is to provide a method for operating the circuit to supply low voltage to the master BMS for a short span of time to store cover opening event in the memory of the master BMS.
[0013] Another object of the present invention is to provide a system where low voltage is supplied to the master BMS when auxiliary low voltage supply source is disconnected.
[0014] These and other objects and advantages will become more apparent when reference is made to the following description and accompanying drawings.
SUMMARY
[0015] This summary is provided to introduce concepts related to a circuit of traction battery pack and a method to detect un-authorized opening of cover of the traction battery pack and storing the action into non-erasable memory of master BMS. 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.
[0016] In an embodiment, the present subject matter relates to a traction battery pack comprising a master battery management system (BMS) coupled with a plurality of battery cells from a battery string connected in series to receive low voltage (LV). The traction battery pack further comprises a first switch (SI) that is provided on a positive terminal line and a second switch (S2) that is provided on a negative terminal line and a resistor capacitor (RC) circuit including

a resistor (R2) and a capacitor (CI) that are provided on the positive terminal line in series. Further, an optical isolator is provided in between the resistor (R2) and the capacitor (CI) to supply the low voltage (LV) to the master BMS when the first switch (SI) and the second switch (S2) are closed.
[0017] In an aspect, the optical isolator comprises a light emitting diode (LED) that is coupled with the resistor (R2) to receive the low voltage (LV) from the positive terminal line and a photo transistor that receives the low voltage (LV) from the positive terminal line.
[0018] In an aspect, the master BMS comprises a cover open detection module to store cover opening action in a memory at event when opening of cover of the traction battery pack is detected. The cover opening action is detected by means of activation of master BMS in the absence of auxiliary battery to supply low voltage.
[0019] In an aspect, upon opening of the cover of the traction battery pack the first switch (SI) and the second switch (S2) are closed to supply the low voltage (LV) from the plurality of cells (101a) to the master BMS, where the first switch (SI) and the second switch (S2) are normally closed switches.
[0020] In an aspect, the master BMS receives the low voltage (LV) from the positive terminal line through the photo transistor of the optical isolator and the negative terminal line the plurality of cells.
[0021] In an aspect, the first switch (SI) and the second switch (S2) may be plunger type switches, inductive type switches, light dependent switches etc.
[0022] In an aspect, the optical isolator disconnects the positive terminal line to stop supply of the low voltage (LV) to the master BMS when the capacitor (CI) is fully charged.
[0023] In an aspect, a first fuse is provided on the positive terminal line and a second fuse is provided on the negative terminal line, where the first fuse is

provided in between the optical isolator and the master BMS on the negative terminal line.
[0024] In an aspect, in an event of isolation fault, the first fuse and the second fuse blow to protect the other part of detection circuit and master BMS.
[0025] In an embodiment the present subject matter relates to a method for storing an event of un-authorized opening of cover of traction battery pack. The method comprises steps of closing, upon opening of the cover of the traction battery pack, a first switch (SI) and a second switch (S2); drawing, through a positive terminal line and a negative terminal line, current from a plurality of cells connected in series from a battery string; supplying the current through a resistor capacitor (RC) circuit via input to an optical isolator; closing switch in the optical isolator by a photo transistor based on signals received from a light emitting diode (LED) of the optical isolator to make connection on the positive terminal line to supply current to a master BMS; and storing, by a cover open detection module, the event of the opening of the cover of the traction battery pack in a memory of the master BMS.
[0026] In an aspect, the method includes opening, when the capacitor of the RC circuit is fully charged, the switch of the optical isolator to disconnect the connection of the positive terminal line and to stop the supply of current to the master BMS; and switching OFF the master BMS.
[0027] In an aspect, the method includes at an event of isolation fault and short circuit in BMS, blowing a first fuse (Fl) and a second fuse (F2) to protect the master BMS from high current supply.
[0028] In an aspect, the method includes the supplying comprises receiving current by the light emitting diode (LED) of the optical isolator from the resistor and the photo transistor closing the switch based upon the signals in the form of light received from the light emitting diode (LED) to close the positive terminal line to supply current to the master BMS.

[0029] Various objects, features, aspects, and advantages of the inventive 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
[0030] The illustrated embodiments of the subject matter will be best 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:
[0031] Fig. 1 illustrates architecture of traction battery pack with RC circuit and optical isolator, in accordance with an embodiment of the present subject matter;
[0032] Fig. 2 illustrates block diagram of Master BMS, in accordance with an embodiment of the present subject matter; and
[0033] Fig. 3 illustrates a method for supplying low voltage to the master BMS at an event of un-authorized cover opening of the traction battery pack and storing the action in memory of the master BMS, in accordance with an embodiment of the present subject matter.
[0034] 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 methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[0035] The detailed description of various exemplary embodiments of the 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 falling within the scope of the present disclosure as defined by the appended claims.
[0036] 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, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0037] 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 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, components and/or groups thereof.
[0038] 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 sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0039] 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 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.
[0040] Unless otherwise defined, all terms (including technical and scientific 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 formal sense unless expressly so defined herein.
[0041] Non-limiting Definitions
[0042] 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 present disclosure.
[0043] 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, authenticating it and / or balancing it.
[0044] Low voltage: Less than 60V
[0045] High voltage: 60V or more
[0046] Optical Isolator: It is an electronic component that transfers electrical signals between two isolated circuits by using light.
[0047] RC Circuit: RC circuit is resistor capacitor circuit which is driven by voltage or current. The RC circuit may comprise a plurality of resistors and a plurality of capacitors. A first order RC circuit comprises one resistor and one capacitor. In the RC circuit, the resistor and the capacitor can be placed in parallel and can be placed in series. When the resistor is connected in series with the

capacitor forming an RC circuit, the capacitor will charge up gradually through the resistor until the voltage across the capacitor reaches that of the supply voltage. The time also called the transient response, required for the capacitor to fully charge is equivalent to about 5 time constants or 5T. Where T is R *C.
[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 various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0049] Technical objective of the present subject matter is to detect un-authorised cover opening of the traction battery pack when there is no supply of current from outside.
[0050] The present subject matter can be implemented in any electric vehicle having traction battery pack. Further, the present subject matter overcomes all the technical problems as mentioned in the background section by providing a circuit that can use a plurality of battery cells, for example, 4-7 cells which are connected in series to supply low voltage to the master BMS of the traction battery pack to detect the opening of cover and storing the action into electrically-erasable memory of the master BMS.
[0051] Exemplary Implementations
[0052] To this, as shown in fig. 1, an architecture of a traction battery pack 100 for an electric vehicle is explained. The architecture of traction battery pack 100 comprises a battery string 101 and a master battery management system (BMS) 110 coupled with the battery string 101. The master BMS 110 is coupled to a plurality of battery cells 101a from the battery string 101. The plurality of battery cells 101a are 4-7 cells of the battery string 101. The plurality of battery cells 101a are used to draw small current or low voltage from the high voltage battery string 101.

[0053] A positive terminal line is coming out from the positive terminal of the plurality of cells 101a and a negative terminal line is coming output from the negative terminal of the plurality of cells 101a. A first switch SI 102 is provided on the positive terminal line to complete the connection between the positive terminal of the plurality of cells 101a and the positive terminal (+) of the master BMS 110 and a second switch S2 103 is provided on the negative terminal line to complete the connection between the negative terminal of the plurality of cells 101a and the negative terminal (-) of the master BMS 110. A first resistor Rl may be provided on the positive terminal line to limit the inrush current in BMS.
[0054] The first switch SI 102 and the second switch S2 103 are switches that remain in open condition when cover of the traction battery pack is intact with body of the traction battery pack. At an event of opening of the cover, the normally closed switches SI and S2 are closed and makes the connection across the plurality of battery cells 101a and the master BMS 110.
[0055] Further, a RC circuit 109 comprising a second resistor 'R2' 104 and a capacitor CI 105 is provided in a series on the positive terminal line. An optical isolator 106 comprising a light emitting diode (LED) 106a and a photo transistor 106b is provided in between the resistor 104 and the capacitor 105 on the positive terminal line to supply low voltage from the plurality of battery cells 101a to the master BMS 110. The positive terminal line bifurcates into two lines where one positive terminal line goes to the optical isolator 106 through the resistor 104 of the RC circuit and other line goes to the optical isolator 106 directly. The LED 106a of the optical isolator 106 receives the current due to voltage difference to emit light whose intensity is proportional to the electrical signal. The emitted light falls upon the photo transistor 106b of the optical isolator 106 to make the connection of the other positive terminal line and supply the low voltage to the master BMS 110.

[0056] The RC circuit 109 has a time constant 5T which defines the time taken by capacitor 105 to get almost fully charged. The time constant can be calculated by equation 1:
5T = 5R* C Equation 1
For example, value of resistor Rl is 1Q and R2 is 5 KQ and capacitor C is lOOuF.
Time constant (seconds) = 5* 5* 103 * 100 * 10"6
Time constant (seconds) = 2.5 seconds
[0057] When the capacitor 105 gets fully charged, the current flowing through the RC circuit 109 stops, resultantly the LED 106a stops emitting any light. In the absence of light, the photo transistor 106b opens the connection and disconnects the connection between the low voltage positive line and the master BMS 110.
[0058] For example, considering the above values, the present capacitor 105 gets fully charged in around 2.5 seconds and disconnects the connections for further supply of low voltage to the master BMS 110. Such short period of time is enough to store the event in memory of master BMS, and further to prevent unbalance of plurality of cells 101a from rest of cells of string 101.
[0059] The time constant defines the operating time of the master BMS 110 on the low voltage supply by the plurality of battery cells 101a. In the present operating time, the master BMS 110 store the cover opening action in non-erasable or EEPROM memory for further process and accessing. The status of the EEPROM further can be accessed through CAN communication with any computing device about the un-authorized access or opening of the cover of the traction battery pack 100.
[0060] In an implementation, a first fuse 107 is provided in between the optical isolator 106 and the master BMS 110 on the positive terminal line and a second fuse 108 is provided on the negative terminal in between the second switch S2 103 and the master BMS 110. At an event of the isolation fault or short circuit, the either of the fuse 107 or 108 blow to disconnect the connection

between the high voltage battery string 101 and the master BMS 110 to safe or protect the master BMS 110 from high current or high voltage supply. Further, the traction battery pack stops supplying any voltage for traction. Even in that case, the operator will get information that cover of the battery pack was opened.
[0061] Fig. 2 illustrates block structure of the master BMS 110, 200 with a cover open detection module 201 along with a non-erasable memory 202 to store the signal or inputs indicating cover opening action. Upon receiving the low voltage from the plurality of battery cells 101a in the absence of the auxiliary battery supply, the cover open detection module 201 sends a signal to the memory 202 indicating actuation of either or both the switches 102, 103. The memory 202 can be an electrically erasable programmable read-only memory (EEPROM). The memory 202 can be accessed through CAN communication with any computing device, such as computer to check the status. In case authorized access of the traction battery pack 100 during servicing or repairing by the authorized service centre, the action stored in the memory 202 can be erased later, using method and/ or tools known to authorized-personals only.
[0062] In an embodiment, the master BMS 110, 200 may store the cover open action in the memory 202 along with the date, time, odometer reading etc.
[0063] In an embodiment, the memory 202 may be non-erasable memory to store all events when the cover of the battery pack is opened with flag of authorized or un-authorized.
[0064] Fig. 3 illustrates a method (300) for supplying low voltage to the master BMS at an event of un-authorized cover opening of the traction battery pack and storing the cover opening action in memory of the master BMS. The method for operating the traction battery pack at an event when no external low voltage supply is connected and cover of the battery pack is opened. The method comprising:

[0065] At step 302, the method includes determining whether battery cover is opened or not. When the battery cover is opened, the method proceeds to step 304. In case cover is not opened, the method ends.
[0066] At step 304, the method includes closing switch SI 102 and switch S2 103 and remaining in normally closed condition. Upon opening the cover, the switch actuates and closes the switches to make the connection between a plurality of battery cells 101a of the battery string 101 and the master BMS 110, as shown in fig. 1.
[0067] At step 306, the method includes determining whether there is any isolation fault or short circuit fault in the traction battery pack 100. In case, there is an isolation fault, the method proceeds to step 308 else method proceeds to step 310.
[0068] At step 308, the method includes blowing the fuse 107 and the fuse 110 at an event when there is any isolation or short circuit fault in the traction battery pack 100. Fuses 107, 108 blow to disconnect the connection between high voltage battery string and the master BMS to protect the master BMS from any damage.
[0069] At step 310, the method includes drawing current/low voltage from a plurality of battery cells 101a connected in series from the high voltage battery string 101 across the positive terminal line and the negative terminal line. For example, the number of cells are 4-7 that provides low voltage, i.e., 12V to the master BMS 110 for its operations.
[0070] At step 312, the method includes supplying current to the RC circuit 109 provided on the low voltage supply line to the master BMS 110. Further, an optical isolator 106 is provided in between a resistor 104 and a capacitor 105 of the RC circuit 109. The optical isolator 106 receives input from the resistor 104.
[0071] At step 314, the method includes supplying current to light emitting diode (LED) 106a of the optical isolator 106 through the resistor 104. The LED

106a emits lights that falls on a photo transistor 106b of the optical isolator 106, which in response closes the circuit to join the positive terminal line to supply low voltage (LV) to the master BMS 110.
[0072] At step 316, the method includes storing the cover open detection action into the memory 202 of the master BMS 110 when the low voltage from the optical isolator 106 supplies to the master BMS 110. Upon receiving the low voltage (LV) from the optical isolator, the master BMS 110 activates and recognizes the present activation due to opening of the cover of the traction battery pack. The master BMS 110, 200 comprises a cover open detection module 201 that detects the low voltage supply and generates a signal and stores the same into the memory 202. The memory 202 may be EEPROM memory or non¬erasable memory.
[0073] In one implementation, the cover open detection module 201 may store the cover opening action along with time, date, odometer reading etc. into the memory.
[0074] At step 318, the method includes opening the switch operated by the photo transistor 106b of the optical isolator when the capacitor 105 of the RC circuit 109 is fully charged. Upon full charge, the capacitor 105 has attained same voltage as of supply voltage therefore, there is no or very minimal flow of current across the RC circuit 109. In the absence of the current through the RC circuit 109, the LED 106a of the optical isolator 106 does not emit any light. The photo transistor 106b in response opens the switch to disconnect the connection made on the positive terminal line and no low voltage is supplied to the master BMS 110.
[0075] The capacitor 105 gets fully charged as per the time constant 5T of the RC circuit 109. For example, the capacitor 105 gets fully charged within 2-3 seconds. Within this time period, the master BMS 110 gets low voltage supply and logs/stores the cover open action into the memory 202 of the master BMS 110,200.

[0076] At step 320, the method includes switching OFF the master BMS 110, 200 when the capacitor 105 is fully charged and no current flows through the RC circuit 109. The optical isolator 106 opens the switch to disconnect the connection on the positive terminal line.
[0077] With the present subject matter, it becomes possible to log or store cover opening action into memory of the master BMS. Further, this action can be accessed by any computing device, for example, computer to check un-authorized access of the traction battery pack.
[0078] In an implementation, the master BMS may not allow supply of high voltage for traction of vehicle when the traction battery pack is accessed in an un¬authorised manner.
[0079] 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 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 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 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."
[0080] 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

1.A traction battery pack (100) comprising:
a master battery management system (BMS) (110, 200) coupled with a plurality of battery cells (101a) from a battery string (101) connected in series to receive low voltage (LV);
a first switch (SI) (102) provided on a positive terminal line and a second switch (S2) (103) provided on a negative terminal line;
a Resistor Capacitor (RC) circuit (109) including a resistor (R2) (104) and a capacitor (CI) (105) provided on the positive terminal line in series;
an optical isolator (106) provided in between the resistor (R2) (104) and the capacitor (CI) (105) to supply the low voltage (LV) to the master BMS (110) when the first switch (SI) (102) and the second switch (S2) (103) are closed.
2. The traction battery pack (100) as claimed in claim 1, wherein the optical isolator (106) comprises a light emitting diode (LED) (106a) that is coupled with the resistor (R2) (104) to receive the low voltage (LV) from the positive terminal line and a photo transistor (106b) to receive the low voltage (LV) from the positive terminal line.
3. The traction battery pack (100) as claimed in claim 1, wherein the master BMS (110, 200) comprises a cover open detection module (201) to store cover opening action into a memory (202) at an event when opening of cover of the traction battery pack (100) is detected.
4. The traction battery pack (100) as claimed in claim 3, wherein upon opening of the cover of the traction battery pack (100):
the first switch (SI) (102) and the second switch (S2) (103) are closed to supply the low voltage (LV) from the plurality of cells (101a) to the master BMS (110, 200), where the first switch (SI) (102) and the second switch (S2) (103) are normally closed switches.

5. The traction battery pack (100) as claimed in claim 3, wherein the master BMS (110, 200) receives the low voltage (LV) from the positive terminal line coming out from the photo transistor (106b) of the optical isolator (106) and the negative terminal line of the plurality of cells (101a).
6. The traction battery pack (100) as claimed in claim 1, wherein the first switch (SI) (102) and the second switch (S2) (103) are plunger type switches.
7. The traction battery pack (100) as claimed in claim 1, wherein the optical isolator (106) disconnects the positive terminal line to stop supply of the low voltage (LV) to the master BMS (110, 200) when the capacitor (CI) (105) gets fully charged.
8. The traction battery pack (100) as claimed in claim 1, wherein
a first fuse (107) is provided on the positive terminal line; and
a second fuse (108) is provided on the negative terminal line, where
the first fuse (107) is provided in between the optical isolator (106) and the
master BMS (110) on the positive terminal line.
9. The traction battery pack (100) as claimed in claim 8, wherein, at an event of isolation fault, the first fuse (107) and the second fuse (108) blow to protect the master BMS (110).
10. A method for storing an event of un-authorized opening of cover of traction battery pack (100), the method comprising:
closing (304), upon opening of the cover of the traction battery pack (100), a first switch (SI) and a second switch (S2) (103);
drawing (310), through a positive terminal line and a negative terminal line, current from a plurality of cells (101a) connected in series with a battery string (101);
supplying (312) the current through a Resistor Capacitor (RC) circuit (109) via input to an optical isolator (106);
closing (314) switch in the optical isolator (106) by a photo transistor (106b) based on light signals received from a light emitting diode (LED)

(106a) of the optical isolator (106) to make connection on the positive terminal line to supply current to a master BMS (110, 200); and
storing (316), by a cover open detection module (201), the event of the opening of the cover of the traction battery pack (100) in a memory (202) of the master BMS (110, 200).
11. The method as claimed in claim 10, wherein the method comprising:
opening (318), when a capacitor (105) of the RC circuit (109) is fully charged, the switch of the optical isolator (106) to disconnect the connection of the positive terminal line and to stop the supply of the current to the master BMS (110, 200); and
switching OFF (320) the master BMS (110, 200).
12. The method as claimed in claim 10, wherein the method comprising:
at an event of isolation fault, blowing (308) a first fuse (Fl) (107) and a second fuse (F2) (108) to protect the master BMS (110, 200) from high current supply.
13. The method as claimed in claim 10, wherein the supplying (312) comprises
receiving current by the light emitting diode (LED) (106a) of the optical
isolator (106) from the resistor (104) and the photo transistor (106b) closes
the switch based upon the light signals received from the light emitting
diode (LED) (106a) to connect the positive terminal line to supply current to
the master BMS (110, 200).