The present subject matter described herein, relates to an electric vehicle. More particularly, the present subject matter relates to a traction battery pack protection system that safeguard the traction battery pack when software protection system fails to protect the traction battery back when voltage and temperature of the traction battery pack breach the threshold limits.
BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention.
[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, such as 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] A 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 BMS controls the output of the traction battery pack.
[0006] In the existing traction battery pack, the master BMS or the VCU controls opening and closing of high voltage contactors (HV+, HV-) based on the plurality of battery modules states. The master BMS or the VCU may perform the function of software protection having pre-stored conditions for supplying low voltage (LV) signal to control opening and closing of the high voltage contactors (HV+, HV-). Upon closing the high voltage contactors, the high voltage can be drawn from the traction battery pack. Similarly, traction battery pack can be charged by closing the high voltage contactors (HV+, HV-). The master BMS receives and analyses the safety conditions of the traction battery pack and opens the high voltage contactors to safeguard the battery pack. Conditions such as SOC, SOH, high voltage, over-charge, over-discharge are analysed by the master BMS, i.e., controller having a software module to decide when to open and to close the high voltage contactors.
[0007] Technical Problem in the existing traction battery pack where master BMS or VCU operates high voltage contactors is that when there is any failure in the software protection of the master BMS or VCU due to any of the problems such as software hang, ill-defined algorithm, controller clock disruption, or frequent software timer reset, the master BMS or VCU does not control the high voltage contactor effectively or on time to protect the traction battery pack from battery failure conditions, such as over-charge or over-discharge conditions.
[0008] Therefore, there is a need for a system that can over-ride the software controller, such as master BMS or VCU in software protection failure condition to control opening and closing of high voltage contactors to protect the traction battery pack in case of any software failure conditions.

OBJECTS OF THE DISCLOSURE
[0009] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.
[0010] The principal object of the present subject matter is to provide a traction battery pack protection system that can override software protection system comprising controller of master BMS during software protection failure condition to control opening and closing of high voltage contactors.
[0011] Another object of the present subject matter is to provide a method for over-riding the software protection system when the software protection system fails to control the opening and closing of high voltage contactors during battery failure conditions.
[0012] Another object of the present subject matter is to provide a hardware battery protection system for controlling the battery pack when software protection system fails to protect the same during battery failure conditions.
[0013] These and other objects and advantages will become more apparent when reference is made to the following description and accompanying drawings.
SUMMARY
[0014] This summary is provided to introduce concepts related to traction battery protection system for protecting traction battery pack by a controller and by a hardware protection circuitry during software failure conditions. 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.
[0015] In an embodiment, the present subject matter relates to a traction battery pack protection system to protect a traction battery pack in battery failure conditions where failure conditions are beyond predefined upper and lower threshold limits. The traction battery pack protection system comprising a master battery management system (BMS) to protect the traction battery pack using a

controller having predefined logics to open and close high voltage contactors (HV+, HV-) based on the battery failure conditions. The traction battery pack protection system further comprises a hardware protection circuitry provided in each of a plurality of slave battery management system (BMS) and the master BMS. The hardware protection circuitry comprising a voltage comparators, a temperature comparators, a OR block (1), and an isolator provided in each of the slave BMS, where output signal of the voltage comparators and the temperature comparators is received by the OR block (1) and output signal of the OR block (1) is received by the isolator to isolate the HV battery string ground from ECU/ VCU/ master BMS ground. The hardware protection circuitry comprises an OR block (2) in the master BMS to receive output of each of the isolator from the plurality of slave BMS and also receives an output signal of an over-current detection circuit. Further, a signal delay and filtering circuit provided in the master BMS to receive output signal of the OR block (2) to delay the output signal and attenuate the ripples in output signal. The hardware protection circuitry further comprises a first circuit having a first transistor, which can act as a closed or an open switch, receiving the output signal from the signal delay and filtering circuit, and a second circuit having a second transistor, which act as an open switch when the first transistor act as a closed switch and disconnects supply of low voltage to a relay coil; and a relay coil de-energizes to open the high voltage contactors (HV+, HV-).
[0016] In an aspect, the first transistor is a Bipolar Junction Transistor (BJT) and the second transistor is Metal Oxide Semiconductor Field Effect Transistor (MOSFET).
[0017] In an aspect, the output signal of the OR block (1) and the OR block (2) indicates that output signal of any of the voltage comparators, the temperature comparators, or the over current detection circuit is beyond a predefined upper and lower threshold limit (Th) where the controller (109) is not able to control the high voltage contactors.

[0018] In an aspect, the first circuit comprises a first resistor and a second resistor connected in series with each other; the first transistor having a base terminal (B) receiving output of the first resistor, an emitter terminal (E) in parallel position with the second resistor and a collector terminal (C) coupled to the controller; and a third resistor connected in series with the emitter terminal (E) of the first transistor and a fourth resistor connected in series with the collector terminal (C) of the first transistor, where the third resistor and the fourth resistor are in parallel with each other when the first transistor acts as a closed switch.
[0019] In an aspect, the first transistor acts as a closed switch when voltage drop at the base terminal (B) and the emitter terminal (E) is more than that of the cut-in voltage for the semiconductor.
[0020] In an aspect, the second transistor acts as an open switch when the voltage drop at source and gate voltage terminal, which is same as output voltage of the first transistor at junction point (X), is less than threshold voltage (THv) of the second transistor (121).
[0021] In an embodiment, the present subject matter relates to a method for protecting a traction battery pack in battery failure conditions through hardware protection circuitry. The method comprising receiving output signals from each of voltage comparators and temperature comparators; determining whether any of the output signal from any of the voltage comparators or temperature comparators is beyond predefined upper and lower threshold limit (Th); isolating the output signals from the HV battery string ground to ECU/ VCU/ Master BMS ground; determining whether any of the output signals from any of the voltage comparators or temperature comparators or over current detection circuit is beyond predefined upper and lower threshold limit (Th); delaying and attenuating the output signal received from an OR block (2) to add the delay and to perform attenuation of ripples or false triggering; closing a first transistor when the determined output signal is beyond the predefined upper and lower threshold limits (Th); and opening a second transistor when the first transistor is closed.

[0022] In an aspect, the method comprises opening high voltage contactors when the second transistor is opened.
[0023] In an aspect, the method includes the closing the first transistor when voltage drop at base terminal (B) and emitter terminal (E) of the first transistor is more than that of the cut-in voltage for the semiconductor.
[0024] In an aspect, the method includes the opening the second transistor when voltage drop at source and gate terminal of the second transistor, which is same as output voltage of the first transistor at junction point (X), is less than threshold voltage (THv) of the second transistor.
[0025] 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
[0026] 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:
[0027] Fig. 1 illustrates architecture of traction battery pack protection system having hardware protection system and software protection system, in accordance with an embodiment of the present subject matter; and
[0028] Fig. 2 illustrates a method for working of the traction battery pack protection system, in accordance with an embodiment of the present subject matter.
[0029] 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
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] Non-limiting Definitions
[0037] 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.
[0038] Master battery management system (BMS): 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.
[0039] Slave BMS: A system which is any electronic system that manages a plurality of cells in a battery module such as by detecting state of health (SOH), temperature, state of charge (SOC) condition, over-charge and over-discharge

voltage conditions, and communicating the conditions of the plurality of cells to master BMS.
[0040] Battery failure conditions: Over-charge, deep-discharge, higher charge or discharge current. For example, in NMC chemistry, safe operating range is 3V to 4.1V & extreme limits are 2.5V and 4.2V.
[0041] Low voltage: Less than 60V
[0042] High voltage: 60V or more
[0043] MOSFET: A metal-oxide-semiconductor field-effect transistor is a field-effect transistor (FET with an insulated gate) where the voltage determines the conductivity of the device. It is used for switching or amplifying signals. The ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. The MOSFET has four terminals, source (S), gate (G), drain (D) and body (B) terminals.
[0044] Bipolar Junction Transistor (BJT): The Bipolar Junction Transistor construction consists of two PN-junctions with three connecting terminals with each terminal being given a name to identify it from the other two. These three terminals are known and labelled as the Emitter (E), the Base (B) and the Collector (C) respectively. The BJT can be of two types, such as NPN and PNP.
[0045] Isolator: Purpose of isolator is to isolate the HV battery string ground and ECU/ VCU/ master BMS ground from short circuit.
[0046] 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.
[0047] Technical objective of the present subject matter is to protect the traction battery pack when software protection system fails to control opening and

closing of High Voltage Contactors of the battery pack during battery failure conditions.
[0048] 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 protection system having a hardware protection circuitry to override the software protection system, i.e., controller of the master BMS when the controller is not able to control the opening of the high voltage contactors to protect the traction battery pack from damage during battery failure conditions.
[0049] Exemplary Implementations
[0050] To this, as shown in fig. 1, an architecture of a traction battery pack protection system 100 for an electric vehicle is explained. The architecture of traction battery pack protection system 100 comprises a master battery management system (BMS) 102 coupled with a plurality of slave BMS 101. The master BMS 102 comprises a controller 109 having predefined logics to open and close high voltage contactors (HV+, HV-) based on the battery failure conditions.
[0051] Each of the battery module is coupled with a slave BMS 101 and each of the slave BMS 101 is coupled with the master BMS 102 to communicate the battery estimations, such as SOC, SOH, over-charge, over-discharge, temperature of battery cells. The present traction battery pack protection system 100 includes a master BMS 102 protection system using the controller 109 which is commonly known as software protection system and a hardware protection circuitry 200 that overrides the software protection system when the controller 109 is not able to control the high voltage contactors (HV+, HV-) due to software failure conditions.
[0052] The hardware protection circuitry 200 comprises hardware circuitry in the plurality of slave BMS 101 as well as hardware circuitry in the master BMS 102. In each of the plurality of slave BMS 101, a voltage comparators 104 and a temperature comparators 105 that generate alarm signal when voltage and temperature of the battery modules are going beyond predefined upper and lower

threshold limits. The predefined upper and lower threshold limits are those limits where the controller 109 of the master BMS 102 does not work properly to control the high voltage contactors 118, 119. Upon reaching the predefined upper and lower threshold limits (Th), the hardware protection circuitry 200 overrides the controller 200 inputs to control the opening of the high voltage contactors 118, 119.
[0053] The hardware protection circuitry 200 in each of the plurality of slave BMS 101 has an OR block (1) to receive output signal from each of the voltage comparators 104 and the temperature comparators 105. When output signal of any of the voltage comparators 104 and the temperature comparators 105 indicate breaching of the predefined upper and lower threshold limit (Th), the OR block (1) gives output signal corresponding to the output signal of the voltage comparators 104 and/ or the temperature comparators 105. Further, an optical isolator 106 is provided in each of the plurality of slave BMS 101 to isolate the HV battery string ground and ECU/ VCU/ master BMS ground from short circuit.
[0054] In the master BMS 102, output signal from the isolator 106 of each of the plurality of slave BMS 101 is given to an OR block (2) along with output signal of an over current detection circuit 107 that determines whether current in the battery modules are beyond predefined limit. The hardware protection circuitry 200 comprises a signal delay and filtering circuit 108 to receive output signal from the OR block (2). The signal delay and filtering circuit attenuates the ripples in signal and provide adequate delay to avoid false triggering.
[0055] The hardware protection circuitry 200 comprises a first circuit 115 having a first transistor 120 along with a plurality of resistors. The first transistor 120 receives the output signal from the signal delay and filtering circuit (108) and acts as a closed switch. The output signal indicates that voltage, temperature, and current of the battery modules are beyond the predefined upper and lower threshold limits (Th). In normal operation, when voltage, temperature, and current of the battery modules are within the predefined upper and lower threshold limits (Th), the controller 109 of the master BMS 102 controls the opening and closing

of the high voltage contactors 118, 119 for charge and discharge of the plurality of battery modules.
[0056] The hardware protection circuitry 200 further comprises a second circuit 116 having a second transistor 121 that acts as an open switch when the first transistor 120 acts as a closed switch and disconnects the supply of low voltage 122 to a relay coil 117 provided to open and close the high voltage contactors 118, 119.
[0057] In another case, during normal operation conditions, when the first transistor 120 acts as an open switch irrespective of software control, the second transistor 121 is controlled by software controller to act as a closed or an open switch by energizing or de-energizing the relay coil 117 to control the high voltage contactors 118, 119.
[0058] In an embodiment, the first transistor 120 is Bipolar Junction Transistor (BJT) and the second transistor 121 is Metal Oxide Semiconductor Field Effect Transistor (MOSFET). However, the implementation of the present subject matter is not limited to use of combination of BJT and MOSFET transistor, it can be combination of any other transistor where opening of one transistor is based on closing of other transistor. In the present embodiment, the first transistor 120 is NPN BJT and the second transistor 121 is NMOS MOSFET.
[0059] The first circuit 115 comprises a first resistor 110 and a second resistor
111 connecting in series with each other. The first transistor 120 having a base terminal (B) receiving output of the first resistor 110, an emitter terminal (E) which is in parallel position with the second resistor 111 and a collector terminal (C) coupled to the controller (109) of the master BMS 102. Further, a third resistor 112 connected in series with the emitter terminal (E) of the first transistor 120 and a fourth resistor 113 connected to the controller (109). The third resistor
112 and the fourth resistor 113 are in parallel with each other when the first transistor 120 acts as a closed switch.

[0060] The first transistor 120 acts as a closed switch when voltage drop at the base terminal (B) and emitter terminal (E) is more than that of the cut-in voltage for the semiconductor. In normal conditions, the voltage drop at the base terminal (B) and emitter terminal (E) is more than that of the cut-in voltage for the semiconductor.
[0061] The second transistor 121 is a MOSFET type switch, specifically, an NMOS type switch. In the present MOSFET transistor, gate terminal is connected with junction point 'X' joining the output voltage of the first transistor 120 and output voltage of the controller 109. Where drain terminal (D) is connected with the low voltage 122 and source terminal (S) is connected with the relay coil 117. The MOSFET type transistor acts as a closed switch when voltage across gate and source terminals is more than a predefined threshold voltage (THv) and act as an open switch when voltage across gate and source terminals is less than a predefined threshold voltage (THv).
[0062] In the present embodiment, the second transistor 121 acts as an open switch when voltage drop at gate and source terminals, which is same as output voltage of the first transistor 120 at junction point (X), is less than the threshold voltage (THv) of the second transistor 121.
[0063] When the second transistor 121 acts as open switch, the low voltage 122 from the drain terminal is not reaching the relay coil 117 hence the relay coil de-energizes to open the high voltage contactors 118, 119.
[0064] Working example for closing the first transistor and opening the second transistor when battery failure conditions exceed the predefined upper and lower threshold limits (Th).
[0065] For example, the signal delay and filtering circuit 108 gives 1A current as an output. And the second transistor 121 has threshold voltage value IV.
[0066] First resistor 110 is 1 Q, the second resistor 111 is 10 Q, the third resistor 112 is 0.4 Q, and the fourth resistor 113 is 10 Q.

[0067] When 1A current passes through the first resistor 110, the voltage drop across the first resistor is IV calculated using below equation:
V = I*R
V=l*l
V=1V
[0068] As the first resistor 110 and the second resistor 111 are in series, the voltage drop across the second resistor 111 is 10V, as calculated below:
V=10*l
V=10V
[0069] As second resistor 111 is in parallel with base and emitter terminals of the first transistor 121, the voltage drop across the base and emitter terminals is same as voltage drop across second resistor 111, which is IV. As voltage drop at the base terminal (B) and emitter terminal (E) is more than that of the cut-in voltage for the semiconductor, the first transistor 120 acts as closed switch.
[0070] Upon closing the switch, the third resistor 112 and the fourth resistor 113 are in parallel with each other and resultant resistance across the close loop of collector terminal and the emitter terminal is .38 Q.
Rparallel=(Rl*R2)/(Rl+R2) Rparallel = (0.4*10)/(0.4+10) Rparallel = 4/10.4 Rparallel = 0.38
V = IR
V=.38Q* 1A
V= .38V
[0071] The voltage drop at the junction point X or at the source gate terminals of the second transistor 121 is 0.38V which is smaller than the threshold voltage

(THv) IV of the second transistor 121. Therefore, the second transistor 121 will not close the drain terminal with the source terminal, and acts as an open switch. Accordingly, the low voltage 122 provided at the drain terminal will not flow to the relay coils 117 to control the high voltage contactors 118, 119.
[0072] In the absence of the low voltage 122, the relay coil 117 de-energizes and opens the high voltage contactors 118, 119 to protect the traction battery pack from the battery failure conditions.
[0073] Fig. 2 illustrates a method 300 for protecting a traction battery pack in battery failure conditions through hardware protection circuitry (200). The method comprising:
[0074] At step 302, the method 300 includes receiving output signals from each of voltage comparators 104 and/ or temperature comparators 105 at OR block (1).
[0075] At step 304, the method 300 includes determining whether any of the output signal from any of the voltage comparators 104 or temperature comparators 105 is high.
[0076] At step 306, the method 300 includes isolating the output signals from HV string to BMS LV ground.
[0077] At step 308, the method 300 includes determining whether any of the output signal from any of the voltage comparators 104 or temperature comparators 105 or over current detection circuit 107 is high.
[0078] At step 310, the method includes delaying and attenuating the output signal from an OR block (2) to avoid the false triggering of the signal.
[0079] At step 312, the method includes closing a first transistor 120 when the determined output signal is high. The first transistor 120 is closed when voltage drop at base and emitter terminal of the first transistor 120 is more that the cut-in voltage for the semiconductor.

[0080] At step 314, the method includes opening a second transistor 121 when the first transistor 120 is closed. The second transistor 121 is opened when voltage drop at source and gate terminals of the second transistor 121, which is same as output voltage of the first transistor 120 at junction point (X), is less than threshold voltage (THv) of the second transistor 121.
[0081] At step 316, the method includes opening high voltage contactors (118, 119) when the second transistor (121) is opened.
[0082] 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."
[0083] 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 protection system (100) to protect a traction battery pack in battery failure conditions, the traction battery pack protection system (100) comprising:
a master battery management system (BMS) (102) to protect the traction battery pack using a controller (109) having predefined logics to open and close high voltage contactors (HV+, HV-) based on the battery failure conditions; characterized in that
a hardware protection circuitry (200) provided in each of a plurality of slave battery management system (BMS) (101) and the master BMS (102), the hardware protection circuitry (200) comprising:
a voltage comparators (104), and a temperature comparators (105), and an OR block (1) provided in each of the slave BMS (101), where an output signal from any of the voltage comparators (104) or the temperature comparators (105) is received by the OR block (1);
an OR block (2) provided in the master BMS (102) to receive output of each of the isolator (106) from the plurality of slave BMS (101) and also receives output signal of an over current detection circuit (107);
a signal delay and filtering circuit (108) provided in the master BMS (102) to receive output signal of the OR block (2) to delay and attenuate the output signal to avoid false triggering;
a first circuit (115) having a first transistor (120) receives the output signal from the signal delay and filtering circuit (108) and work as a closed switch;
a second circuit (116) having a second transistor (121) act as an open switch when the first transistor (115) acts as a closed

switch and disconnects supply of low voltage (122) to a relay coil (117); and
a relay coil (117) de-energizes to open the high voltage contactors (HV+, HV-) (118, 119).
2. The traction battery pack protection system (100) as claimed in claim 1, wherein the first transistor (120) is Bipolar Transistor (BJT) and the second transistor (121) is Metal Oxide Semiconductor Field Effect Transistor (MOSFET).
3. The traction battery pack protection system (100) as claimed in claim 1, wherein the output signal of the OR block (1) and the OR block (2) indicate that input signal of any of the voltage comparators (104), the temperature comparators (105), or the over current detection circuit (107) is beyond predefined upper or lower threshold limit (Th) where the controller (109) is not able to control the high voltage contactors (117, 118).
4. The traction battery pack protection system (100) as claimed in claim 1, wherein the first circuit (115) comprises:
a first resistor (110) and a second resistor (111) connected in series with each other;
the first transistor (120) having a base terminal (B) receiving output of the first resistor (110), an emitter terminal (E) in parallel position with the second resistor (111) and a collector terminal (C) coupled the controller (109); and
a third resistor (112) connected in series with the emitter terminal (E) of the first transistor (120) and a fourth resistor (113) connected in series with the collector terminal (C) of the first transistor (120), where the third resistor (112) and the fourth resistor (113) are in parallel with each other when the first transistor (120) acts as a closed switch.
5. The traction battery pack protection system (100) as claimed in claim 1,
wherein the first transistor (120) acts as a closed switch when:

voltage drop at the emitter base terminal of first transistor (120) is more than the cut-in voltage of the first transistor (120). The traction battery pack protection system (100) as claimed in claim 1, wherein the second transistor (121) acts as an open switch when:
voltage drop at source terminal, which is same as output voltage of the first transistor (120) at junction point (X), is less than the threshold voltage (THv) of the second transistor (121).
A method (300) for protecting a traction battery pack in battery failure conditions through hardware protection circuitry (200), the method comprising:
receiving (302) output signals from each of voltage comparators (104) or temperature comparators (105);
determining (304) whether any of the input signal of any of the voltage comparators (104) or temperature comparators (105) is beyond predefined upper and lower threshold limit (Th);
isolating (306) the output signals from HV string to LV BMS;
determining (308) whether any of the input signal of any of the voltage comparators (104) or temperature comparators (105) or over current detection circuit (107) is beyond predefined upper and lower threshold limit (Th);
delaying and attenuating (310) the output signal from an OR block (2) to avoid false triggering of signal;
closing (312) a first transistor (120) when the determined output signal is high; and
opening (314) a second transistor (121) when the first transistor (120) is closed.
The method (300) as claimed in claim 7, wherein the method comprises:
opening (316) high voltage contactors (118, 119) when the second transistor (121) is opened.

The method (300) as claimed in claim 7, wherein closing (312) of the first transistor (120) when:
voltage drop at emitter and base terminal of the first transistor (120) is more that the cut-in voltage (120) of the first transistor (120). The method (300) as claimed in claim 7, wherein opening (314) of the second transistor (121) when:
voltage drop at source voltage terminal (VG) of the second transistor (121), which is same as output voltage of the first transistor (120) at junction point (X), is less than threshold voltage (THv) of the second transistor (121).