TECHNICAL FIELD
[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 provide a failsafe of high voltage (HV) traction battery pack in case of passive protection device weld (contactor weld) in the electric vehicle.
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 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, such as contactor or relay 106, 107 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 transmit to Vehicle Control Unit (VCU) for further analysis and protection functions. Further, the passive protection devices 106, 107 can be controlled by the VCU only, master BMS only, or in combination by the VCU and the master BMS.
[0005] As shown in fig. 1, the passive protection device, such as relays 106, 107 that are high voltage (HV) relays, which are directly operated by electronic module. Whenever there is a requirement to withdraw the current from the traction battery pack 100, the VCU 105 energizes relays 106, 107 in the positive relay 106 and the negative relay 107 in a particular sequence including pre-charge relay. The energized relays 106, 107 close the normally-opened (N/O) switch to make an electric connection of the positive relay 106 with a positive terminal (HV+) of the traction battery pack 100 and an electric connection of the negative relay 107 with negative terminal (HV-) of the traction battery pack 100. With closing of the normally-opened switches of the relays 106, 107, the system completes the connection path between the traction battery pack 100 and the high voltage connector 103 to supply voltage to operating units of the electric vehicle.
[0006] As shown in the fig. 1, a Main Service Disconnect (MSD) switch or fuse or plug 108 is provided in between the plurality of battery modules 102 of the traction battery pack 100. The MSD 108 divides the traction battery pack 100 into two parts equally or as per the required configuration. During any failure condition, the MSD 108 is removed manually to disconnect circuit of the traction battery pack 100 supply. Further, the MSD 108 is removed during maintenance working on the traction battery pack 100 for safety reasons to avoid any fatal shock to the operator of the traction battery pack 100.
[0007] In the traction battery pack 100, several failure modes occur, such as emergency shutdown, limp mode and emergency shutdown. The emergency shutdown mode may occur due to hood open condition, air bag open, current leakage detection, isolation failure detection, etc.

[0008] In the emergency shutdown mode, the master BMS 101, upon receiving inputs from the VCU 105 opens the passive protection device or contactor or relays 106, 107 to disconnect the connection between power supply from the traction battery pack 100 and the HV connector 103. With the sudden opening of the passive protection devices 106, 107 a high resistance is created which results in high heat losses because of high current and resistance. The high heat losses melt the passive protection device 106, 107 and welds the passive protection device and continues the power supply to the HV connector 103.
[0009] Further, when there is isolation failure between the traction battery pack 100 and the vehicle chassis due to sudden decrease of resistance between high voltage bus and vehicle chassis, the emergency shutdown mode should immediately disconnect the high voltage supply from the high traction battery pack 100 to avoid any hazards or accidents.
[0010] The continue supply of high voltage power during the emergency shutdown mode is dangerous to the vehicle as well as the occupant or operator of the vehicle.
[0011] The existing system detects the contactor weld or passive protection device weld condition and isolation failure condition, and indicates the same to the operator of the vehicle for corrective measures on instrument panel via visual indicator.
[0012] To disconnect the high voltage supply from the traction battery pack 100, the operator of the vehicle or maintenance operator has to remove the MSD 108 while wearing safety gloves.
[0013] Therefore, there is a need of a system and a method that can disconnect the high voltage supply during passive protection device weld condition and the isolation failure condition in the electric vehicle.
OBJECTS OF THE DISCLOSURE
[0014] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.

[0015] The principal object of the present invention is to provide a system and a method for failsafe of high voltage from a traction battery pack to avoid any fatal hazard to operator of electric vehicle.
[0016] Another object of the present invention is to provide a system with a passive protection device in place of existing Main Service Disconnect (MSD) to disconnect the high voltage supply during contactor weld condition and isolation failure condition.
[0017] Another object of the present invention is to provide a system where the high voltage supply from the traction battery pack is disconnected during emergency shutdown mode by a passive protection device which is operated by the Master BMS.
[0018] These and other objects and advantages will become more apparent when reference is made to the following description and accompanying drawings.
SUMMARY
[0019] This summary is provided to introduce concepts related to a system and a method to provide failsafe of high voltage traction battery pack in case of passive protection device weld condition and isolation failure condition of a traction battery pack of 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.
[0020] In an embodiment, the present subject matter relates to a safety system for an electric vehicle to disconnect high voltage supply from traction battery pack in an event of emergency shutdown mode. The safety system comprising a vehicle control unit (VCU) coupled to an auxiliary battery and the traction battery pack. The traction battery pack comprising a master battery management system (BMS) coupled with a plurality of slave BMS that are coupled to a plurality of battery modules that are connected in series. The traction battery pack further includes a positive side relay and a negative side relay to receive operating input voltage to

make an electric connection with positive terminal and negative terminal of the traction battery pack by closing normally opened (N/O) switches. To provide safety to the traction battery pack in the emergency shutdown event, a safety relay is provided in between the plurality of battery modules connected in series. At an event of starting of the electric vehicle the safety relay receives operating input low voltage from the master BMS to close normally opened (N/O) switch to connect circuit between the plurality of battery modules to supply high voltage. At event of an emergency shutdown condition, the master BMS stops supply of the input low voltage to de-energize the safety relay to open the normally opened (N/O) switch to disconnect the circuit between the plurality of battery modules of the traction battery pack.
[0021] In an aspect, input of the safety relay comprises a low voltage (LV) relay and a main service disconnect (MSD) switch. The MSD switch is in series connection with the low voltage (LV) relay. Further, the low voltage (LV) relay is controlled by the Master BMS.
[0022] In an aspect, the MSD switch is passive device with low voltage contacts.
[0023] In an aspect, the emergency shutdown condition includes welding of the positive side relay or the negative side relay or both and / or isolation failure.
[0024] In an aspect, the master BMS is coupled with the VCU to receive low voltage input from the auxiliary battery. The master BMS comprises a weld detection module to detect weld condition of the positive side relay or the negative side relay or both; an isolation failure detection module to detect isolation failure condition; and a safety relay operating module to stop supply of the input low voltage to the safety relay when any of the positive side relay (202) and / or the negative side relay is weld; and / or isolation failure condition is detected.
[0025] In another embodiment of the present subject matter, a method for disconnecting high voltage supply from a traction battery pack in an event of emergency shutdown conditions is disclosed. The method comprising steps of

detecting, by a master BMS having a weld detection module, weld condition of a positive side relay or a negative side relay or both; detecting, by the master BMS having an isolation failure detection module, isolation failure condition; opening, by the master BMS having a safety relay operating module, a safety relay to disconnect circuit between a plurality of battery modules, when any of the positive side relay and / or the negative side relay is weld; and / or isolation failure condition is detected.
[0026] 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
[0027] 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:
[0028] Fig. 1 illustrates conventional architecture of traction battery pack with Main Service Disconnect (MSD) switch;
[0029] Fig. 2 illustrates architecture of traction battery pack with safety relay, in accordance with an embodiment of the present subject matter; and
[0030] Fig. 3 illustrates a method for disconnecting circuit between plurality of battery modules at an event of emergency condition, in accordance with an embodiment of the present subject matter.
[0031] 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
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] Non-limiting Definitions
[0039] 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.
[0040] 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, authenticating it and / or balancing it.
[0041] Failsafe condition: The condition when circuit path between the plurality of battery modules of a traction battery pack is broken.
[0042] Low voltage: 12V
[00431 High voltage: 60V or more

[0044] Contactor or passive protection device: Relay are referred as contactor, switches or passive protection device.
[0045] Emergency shutdown condition: Emergency shutdown condition occurs due to important component failure which can cause serious safety issues.
[0046] Isolation detection module: Isolation detection module is similar to earth fault detection, which has capability to measure the resistance between high voltage bus and low voltage ground or vehicle chassis and if that resistance is below certain defined threshold, then isolation failure is generated.
[0047] Weld detection module: Weld detection module measures the weld condition by measuring the voltage before and after the contactor. If the contactor is welded, it has same before and after voltage even when the contactor input is already de-energized.
[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 problem: In the existing traction battery pack, when any of the contactor is weld and isolation failure condition, there is no way to keep the traction battery pack safe and to stop unwanted high voltage flow outside the traction battery pack.
[0050] Main objective of the present invention is to provide a safety system that can stop unwanted high voltage flow outside the traction battery pack in an event of welding of any of the contactor and isolation failure.
[0051] The present invention can be implemented in any electric vehicle having traction battery pack. Further, the present invention overcomes all the technical problems as mentioned in the background section by providing a pair of

sub relays that are connected with input voltage supply of main relays. Further, the pair of sub relays are controlled by the master BMS.
[0052] Exemplary Implementations
[0053] To this, as shown in fig. 2, a system for a traction battery pack 200 for an electric vehicle is explained. The safety system comprises a traction battery pack 200 and a Vehicle Control Unit (VCU) (not shown). The output of the traction battery pack 200 is connected with High Voltage (HV) connector to operate the electric vehicle. The vehicle control unit (VCU) is coupled to an auxiliary battery and the traction battery pack 200. The traction battery pack 200 comprises a master battery management system (BMS) 201 that is coupled with a plurality of slave BMS to check safety functions a plurality of battery modules. Further, the master BMS 201 is coupled with the VCU via a CAN network or CAN bus. The VCU is coupled with the low voltage connector that is coupled with auxiliary battery to supply low voltage, i.e., 12V to the traction battery pack 200, in particularly to the master BMS 201.
[0054] The traction battery pack 200 further includes a positive side relay 202 and a negative side relay 203 that are provided in between positive terminals (HV+) of the traction battery pack 200 and the HV connector and negative terminals (HV-) of the traction battery pack 200 and the HV connector, respectively. The positive side relay 202 and the negative side relay 203 energizes upon receiving input voltage from the master BMS 201 to make connections between the traction battery pack 200 and the HV connector.
[0055] To break the circuit path between the plurality of battery modules or to stop unwanted flow of High voltage from the traction battery pack 200, existing MSD 108 (as shown in figure 1) is replaced by a safety relay 204 (or safety contactor, herein after relay can be interchangeably referred as contactor). The safety relay 204 is provided in between the plurality of battery modules that are connected in series. The safety relay 204 divides the plurality of battery modules of the traction battery pack in equal or unequal segments.

[0056] The input drive of the safety relay 204 comprises a low voltage (LV) relay 205 and a main service disconnect (MSD) switch 206. The MSD switch 206 is in series connection with the low voltage (LV) relay 205. The input of the LV relay 205 is controlled by the master BMS 201 and small MSD switch 206 is passive device with low voltage contacts. The low voltage (LV) relay 205 is controlled by the Master BMS 201 and is operated on a low voltage, i.e., 12V.
[0057] At an event of starting of the electric vehicle, the safety relay 204 receives operating input low voltage from the master BMS 201 to close normally opened (N/O) switch 209 to connect circuit between the plurality of battery modules to supply high voltage from the traction battery pack 200. The master BMS 201 supplies low input voltage to the LV relay 205 that energizes to close the normally opened (N/O) switch 207 to further supply the low voltage to the safety relay 204 that closes the normally opened (N/O) switch 209 to complete the circuit for supplying the high voltage from the traction power pack 200.
[0058] At event of an emergency shutdown condition, the master BMS 201 stops supply of the input low voltage to de-energize the safety relay 204 to open the normally opened (N/O) switch 209 to disconnect the circuit between the plurality of battery modules of the traction battery pack 200. The master BMS 201 stops supplying low voltage to the LV relay 205 that results in de-energizing of the LV relay 205 and opening of the normally opened switch (N/O) 207. With opening of the normally opened switch 207, the low voltage supplies to the safety relay 205 is also stopped, that results in opening of the normally open switch (N/O) 209 and breaking / disconnecting circuit between the plurality of battery modules of the traction battery pack 200 and stopping unwanted flow of high voltage current to the high voltage connector.
[0059] In an aspect, the emergency shutdown condition includes welding of any of the positive side relay 202 or the negative side relay 203 or both, and / or isolation failure.
[0060] Referring to fig. 3 that illustrates master BMS 201, 300 of the traction battery pack 200. The master BMS 300 comprises a weld detection condition 301,

isolation failure detection module 302, and a safety relay operating module 303. The master BMS 300 is coupled with the VCU to receive low voltage input from the auxiliary battery. The weld detection module 301 to detect welding of any of the positive side relay 202 or the negative side relay 203 or both during emergency shutdown condition. Further, working of the weld detection module
301 is well known to a person skilled in the art, therefore, the present disclosure does not explain how the weld detection module works to detect the weld condition of any of the relay. The isolation failure detection module 302 to detect isolation failure condition between the traction battery pack 200 and the electric vehicle chassis or body. Further, working of the isolation failure detection module
302 is well known to a person skilled in the art, therefore, the present disclosure does not explain how the isolation failure detection module works to detect the isolation failure condition between the vehicle chassis or body and the traction battery pack 200.
[0061] Based on the inputs from the weld detection module 301 and the isolation failure detection module 302, the safety relay operating module 303 stops supply of the input low voltage to the safety relay 204 when any of the positive side relay 202 or the negative side relay 203 or both is welded and / or isolation failure condition is detected.
[0062] In the emergency condition, the master BMS 201 stops supplying power to the safety relay 204 that resultantly opens the normally open switch 209 that breaks circuit between the high voltage strings of the traction battery pack 200.
[0063] The LV MSD switch 206 is connected in series with the LV relay controlled by the master BMS 201 which is operated on low voltage, therefore, the LV MSD switch 206 is operated on low voltage. The LV MSD switch 206 provides better safety as compared to high voltage MSD in the existing traction battery packs.

[0064] The present MSD switch 206 can be removed by the operator during vehicle failure condition without any safety gloves that increases safety of the vehicle operator during maintenance conditions.
[0065] Referring to fig. 4, a method for disconnecting high voltage supply from a traction battery pack 200 in an event of emergency shutdown conditions. The method comprising:
[0066] Detecting (402), by a master BMS (201, 300) having a weld detection module (301), weld condition of a positive side relay (202) and a negative side relay (203);
[0067] Detecting (404), by the master BMS (201, 300) having an isolation failure detection module (302), isolation failure condition;
[0068] Opening (406), by the master BMS (201, 300) having a safety relay operating module (303), a safety relay (204) to disconnect circuit between a plurality of battery modules, when any of the positive side relay (202) and/or the negative side relay (203) is welded; and / or isolation failure condition is detected.
[0069] 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."
[0070] 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.

claim

1.A safety system for an electric vehicle, the safety system (204) comprising:
a vehicle control unit (VCU) coupled to an auxiliary battery and a traction battery pack (200), the traction battery pack (200) comprising:
a master battery management system (BMS) (201) coupled with a plurality of slave BMS that are coupled to a plurality of battery modules connected in series;
a positive side relay (202) and a negative side relay (203) to receive operating input voltage to make an electric connection with positive terminal and negative terminal of the traction battery pack
(200) by closing normally opened (N/O) switches;
characterized in that
a safety relay (204) provided in between the plurality of battery modules connected in series, at an event of starting of the electric vehicle the safety relay (204) receives operating input low voltage from the master BMS (201) to close normally opened (N/O) switch (209) to connect circuit between the plurality of battery modules to supply high voltage,
at event of an emergency shutdown condition, the master BMS
(201) stops supply of the input low voltage to de-energize the safety
relay (204) to open the normally opened (N/O) switch (209) to
disconnect the circuit between the plurality of battery modules of the
traction battery pack (200).
2.The safety system as claimed in claim 1, wherein input of the safety relay (204) comprises a low voltage (LV) relay (205) and a main service disconnect (MSD) switch (206), the MSD switch (206) is in series connection with the low voltage (LV) relay (205), the low voltage (LV) relay (205) is controlled by the master BMS (201).

3. The safety system as claimed in claim 2, wherein the MSD switch (206) is passive device with low voltage contacts.
4. The safety system as claimed in claim 1, wherein the emergency shutdown condition includes welding of any of the positive side relay (202) or the negative side relay (203) or both, and isolation failure.
5. The safety system as claimed in claim 1, wherein the master BMS (201, 300) coupled with the VCU to receive low voltage input from the auxiliary battery comprises:
a weld detection module (301) to detect weld of the positive side relay (202) and the negative side relay (203) during emergency condition;
an isolation failure detection module (302) to detect isolation failure condition; and
a safety relay operating module (303) to stop supply of the input low voltage to the safety relay (204) when:
any of the positive side relay (202) and / or the negative side relay (203) is weld; and / or
isolation failure condition is detected.
6. A method for disconnecting high voltage supply from a traction battery pack
(200) in an event of emergency shutdown conditions, the method
comprising:
detecting (402), by a master BMS (201, 300) having a weld detection module (301), weld condition of a positive side relay (202) and a negative side relay (203);
detecting (404), by the master BMS (201, 300) having an isolation failure detection module (302), isolation failure condition;

opening (406), by the master BMS (201, 300) having a safety relay operating module (303), a safety relay (204) to disconnect circuit between a plurality of battery modules, when
any of the positive side relay (202) and / or the negative side relay (203) is weld; and / or
isolation failure condition is detected.