Patent Description:
A vehicle that uses one or more battery systems for providing all or a portion of the motive power for the vehicle can be referred to as an xEV, where the term "xEV" is defined herein to include all of the following vehicles, or any variations or combinations thereof, that use electric power for all or a portion of their vehicular motive force. For example, xEVs include electric vehicles (EVs) that utilize electric power for all motive force. As will be appreciated by those skilled in the art, hybrid electric vehicles (HEVs), also considered xEVs, combine an internal combustion engine propulsion system and a battery-powered electric propulsion system, such as <NUM> Volt (V) or 130V systems. The term HEV may include any variation of a hybrid electric vehicle. For example, full hybrid systems (FHEVs) may provide motive and other electrical power to the vehicle using one or more electric motors, using only an internal combustion engine, or using both. In contrast, mild hybrid systems (MHEVs) disable the internal combustion engine when the vehicle is idling and utilize a battery system to continue powering the air conditioning unit, radio, or other electronics, as well as to restart the engine when propulsion is desired. The mild hybrid system may also apply some level of power assist, during acceleration for example, to supplement the internal combustion engine. Mild hybrids are typically 96V to 130V and recover braking energy through a belt or crank integrated starter generator. Further, a micro-hybrid electric vehicle (mHEV) also uses a "Stop-Start" system similar to the mild hybrids, but the micro-hybrid systems of a mHEV may or may not supply power assist to the internal combustion engine and operate at a voltage below 60V. For the purposes of the present discussion, it should be noted that mHEVs typically do not technically use electric power provided directly to the crankshaft or transmission for any portion of the motive force of the vehicle, but an mHEV may still be considered an xEV since it does use electric power to supplement a vehicle's power needs when the vehicle is idling with internal combustion engine disabled and recovers braking energy through an integrated starter generator. In addition, a plug-in electric vehicle (PEV) is any vehicle that can be charged from an external source of electricity, such as wall sockets, and the energy stored in the rechargeable battery packs drives, or contributes to drive, the wheels. PEVs are a subcategory of EVs that include all-electric or battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicle conversions of hybrid electric vehicles and conventional internal combustion engine vehicles.

xEVs as described above may provide a number of advantages as compared to more traditional gas-powered vehicles using only internal combustion engines and traditional electrical systems, which are typically 12V systems powered by a lead acid battery. For example, xEVs may produce fewer undesirable emission products and may exhibit greater fuel efficiency as compared to traditional internal combustion vehicles and, in some cases, such xEVs may eliminate the use of gasoline entirely, as is the case of certain types of EVs or PEVs.

For example, <CIT> relates to a conventional rechargeable battery including an electrode assembly, a case in which the electrode assembly is installed, and a cap assembly. THE electrode assembly includes a first and second electrode and a separator disposed therebetween, and the cap assembly is combined to the case. The cap assembly includes a short circuit tab that is electrically connected to the first electrode and a deformable plate that is electrically connected to the second electrode and includes a notch so as to be opened according to the increase of pressure. The deformable plate is deformed according to the increase of pressure and thus electrically contacts the short circuit tab.

<CIT> relates to a further conventional rechargeable battery having a housing including a proportional valve that is arranged at an opening in a housing wall. The proportional valve has a valve body that is influenced by force in the direction of its closed position and towards the interior of the housing. The proportional valve is embodied at least partially from metal such that it allows the through-flow of gas if the pressure that is prevailing in the housing exceeds a construction-dependent pressure limit value. The proportional valve is configured to be connected electrically to the cathode of the rechargeable battery. A contact element embodied at least partially from metal is configured to be connected electrically to the anode of the rechargeable battery and is arranged on the outside of the housing such that the valve body comes into physical contact with the contact element after the proportional valve has achieved a defined open position.

As technology continues to evolve, there is a need to provide improved power sources, particularly battery modules, for such vehicles. For example, battery modules may undergo overcharge testing to determine boundaries and/or limits of the battery module and its individual battery cells. However, in certain instances, overcharging the battery module may lead to thermal runaway (e.g., an internal short circuit) caused by overheating or over pressurization of the battery cells. Thermal runaway may render the battery module permanently inoperable, and therefore, devices that may prevent or block thermal runaway are desired.

The invention is defined by the wording of independent claim <NUM>. Further embodiments are set out in the dependent claims.

The battery systems described herein may be used to provide power to various types of electric vehicles (xEVs) and other high voltage energy storage/expending applications (e.g., electrical grid power storage systems). Such battery systems may include one or more battery modules, each battery module having a number of battery cells (e.g., Lithium-ion (Li-ion) electrochemical cells) arranged to provide particular voltages and/or currents useful to power, for example, one or more components of an xEV. As another example, battery modules may be incorporated with or provide power to stationary power systems (e.g., non-automotive systems).

During the design and manufacturing process of a battery module, various tests may be performed upon the battery module and its individual battery cells to determine optimal performance parameters. For example, overcharge tests may provide excess electrical current to an individual battery cell of a battery module using a power supply with a voltage that exceeds a voltage of the individual battery cell. Overcharge testing may provide data related to temperature, heat output, and/or voltage of the overcharged battery cell, which may enable designers or manufacturers to modify various components of the battery cell to enhance performance (e.g., minimize damage to an overcharged battery cell). Therefore, such tests may be desirable for providing information that may enable manufacturers to optimize a battery module.

However, in certain cases, overcharging a battery cell may lead to thermal runaway (e.g., an internal short circuit) or another event that can permanently damage the battery cell. For instance, charging a battery cell may generate dendrites as a result of intercalation of positive ions in the anode. During an overcharge test, thermal runaway may result due to an excess buildup of dendrites on a separator of a battery cell (e.g., the dendrites may penetrate the separator enabling mixing of the positive electrode and the negative electrode). Thermal runaway may be undesirable because it generates excessive heat and pressure, which may cause permanent damage to the battery cell and/or render the battery cell permanently inoperable.

It is now recognized that various features may be included in the battery cell that prevent or block thermal runaway while performing overcharge tests. Some traditional battery cells may include a mechanism that disrupts a flow of electrical current to at least one terminal of the battery cell when a pressure in the battery cell reaches a certain level. However, such mechanisms may ultimately lead to decreased current capacity of the battery cell. Therefore, it is now recognized that it may be desirable to maintain the electrical connection to one or both terminals of the battery cell while preventing thermal runaway during overcharge. In accordance with aspects of the present disclosure, when a pressure in the battery cell exceeds a threshold level, an external short circuit may be triggered by electrically coupling the positive terminal and the negative terminal of the battery cell via a casing of the battery cell, for example. Accordingly, thermal runaway may be prevented and an electrical current capacity of the battery cell terminals is not reduced because the electrical pathway (e.g., connection) from an external load to the terminals remains intact. Other embodiments of the present disclosure include an overcharge protection assembly that may trigger an external short circuit on a battery cell that includes an electrically insulative casing.

Certain embodiments of the present disclosure relate to an overcharge protection assembly for battery modules having battery cells with neutral cans. As used herein a "neutral can" may be defined as a battery cell casing that is not electrically coupled to either the positive terminal or the negative terminal of the individual battery cell. Conversely, a "polarized can" may be defined as a battery cell casing which is electrically coupled to the positive terminal or the negative terminal (e.g., the positive terminal or the negative terminal contacts the battery cell casing) of the battery cell.

<FIG> is a perspective view of a vehicle <NUM>, which may utilize a regenerative braking system. Although the following discussion is presented in relation to vehicles with regenerative braking systems, the techniques described herein are adaptable to other vehicles that capture/store electrical energy with a battery, which may include electric-powered and gas-powered vehicles.

As discussed above, it would be desirable for a battery system <NUM> to be largely compatible with traditional vehicle designs. Accordingly, the battery system <NUM> may be placed in a location in the vehicle <NUM> that would have housed a traditional battery system. For example, as illustrated, the vehicle <NUM> may include the battery system <NUM> positioned similarly to a lead-acid battery of a typical combustion-engine vehicle (e.g., under the hood of the vehicle <NUM>). Furthermore, as will be described in more detail below, the battery system <NUM> may be positioned to facilitate managing temperature of the battery system <NUM>. For example, positioning a battery system <NUM> under the hood of the vehicle <NUM> may enable an air duct to channel airflow over the battery system <NUM> and cool the battery system <NUM>.

In other words, the battery system <NUM> may supply power to components of the vehicle's electrical system, which may include radiator cooling fans, climate control systems, electric power steering systems, active suspension systems, auto park systems, electric oil pumps, electric super/turbochargers, electric water pumps, heated windscreen/defrosters, window lift motors, vanity lights, tire pressure monitoring systems, sunroof motor controls, power seats, alarm systems, infotainment systems, navigation features, lane departure warning systems, electric parking brakes, external lights, or any combination thereof. Illustratively, the energy storage component <NUM> supplies power to the vehicle console <NUM> and the ignition system <NUM>, which may be used to start (e.g., crank) an internal combustion engine <NUM>.

Additionally, the energy storage component <NUM> may capture electrical energy generated by the alternator <NUM> and/or the electric motor <NUM>. The alternator <NUM> may generate electrical energy while the internal combustion engine <NUM> is running. More specifically, the alternator <NUM> may convert the mechanical energy produced by the rotation of the internal combustion engine <NUM> into electrical energy. Additionally or alternatively, when the vehicle <NUM> includes an electric motor <NUM>, the electric motor <NUM> may generate electrical energy by converting mechanical energy produced by the movement of the vehicle <NUM> (e.g., rotation of the wheels) into electrical energy. Thus, the energy storage component <NUM> may capture electrical energy generated by the alternator <NUM> and/or the electric motor <NUM> during regenerative braking. As such, the alternator <NUM> and/or the electric motor <NUM> are generally referred to herein as a regenerative braking system.

To facilitate capturing and supplying electric energy, the energy storage component <NUM> may be electrically coupled to the vehicle's electric system via a bus <NUM>. For example, the bus <NUM> may enable the energy storage component <NUM> to receive electrical energy generated by the alternator <NUM> and/or the electric motor <NUM>. Additionally, the bus <NUM> may enable the energy storage component <NUM> to output electrical energy to the ignition system <NUM> and/or the vehicle console <NUM>. Accordingly, when a <NUM> volt battery system <NUM> is used, the bus <NUM> may carry electrical power typically between <NUM>-<NUM> volts.

Additionally, as depicted, the energy storage component <NUM> may include multiple battery modules. For example, as illustrated, the energy storage component <NUM> includes a lithium ion (e.g., a first) battery module <NUM> and a lead-acid (e.g., a second) battery module <NUM>, which each includes one or more battery cells. Alternatively, the energy storage component <NUM> may include any number of battery modules. Additionally, although the lithium ion battery module <NUM> and lead-acid battery module <NUM> are depicted adjacent to one another, they may be positioned in different areas around the vehicle. For example, the lead-acid battery module <NUM> may be positioned in or about the interior of the vehicle <NUM> while the lithium ion battery module <NUM> may be positioned under the hood of the vehicle <NUM>.

The energy storage component <NUM> may include multiple battery modules to utilize multiple different battery chemistries. For example, when the lithium ion battery module <NUM> is used, performance of the battery system <NUM> may be improved since the lithium ion battery chemistry generally has a higher coulombic efficiency and/or a higher power charge acceptance rate (e.g., higher maximum charge current or charge voltage) than the lead-acid battery chemistry. As such, the capture, storage, and/or distribution efficiency of the battery system <NUM> may be improved.

To facilitate controlling the capturing and storing of electrical energy, the battery system <NUM> may additionally include a control module <NUM>. More specifically, the control module <NUM> may control operations of components in the battery system <NUM>, such as relays (e.g., switches) within energy storage component <NUM>, the alternator <NUM>, and/or the electric motor <NUM>. For example, the control module <NUM> may regulate an amount of electrical energy captured/supplied by each battery module <NUM> or <NUM> (e.g., to de-rate and re-rate the battery system <NUM>), perform load balancing between the battery modules <NUM> and <NUM>, determine a state of charge of each battery module <NUM> or <NUM>, determine temperature of each battery module <NUM> or <NUM>, control voltage output by the alternator <NUM> and/or the electric motor <NUM>, and the like.

Accordingly, the control unit <NUM> may include one or more processors <NUM> and one or more memory components <NUM>. More specifically, the one or more processors <NUM> may include one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more general purpose processors, or any combination thereof. Additionally, the one or more memory components <NUM> may include volatile memory, such as random access memory (RAM), and/or non-volatile memory, such as read-only memory (ROM), optical drives, hard disc drives, or solid-state drives. The control unit <NUM> may include portions of a vehicle control unit (VCU) and/or a separate battery control module.

As discussed above, before a battery module may be used to supply power to an xEV, various tests may be conducted upon the battery module and its individual battery cells to optimize operating parameters of the battery module. One such test may be an overcharge test that determines how much electrical current a battery cell may receive, or how long a battery cell may receive an electrical current, before damage occurs to the battery cell. However, in certain instances, overcharge tests may result in thermal runaway (e.g., an internal short circuit within the battery cell), which may cause permanent damage to the battery cell because of excess heat and pressure generated from the overcharge. It is now recognized that it may be desirable to prevent thermal runaway (e.g., an internal short circuit) by triggering an external short circuit (e.g., electrically coupling the positive terminal and the negative terminal of the battery cell) before thermal runaway occurs. In examples useful for understanding the invention, the external short circuit may be triggered by establishing an electrical connection between a positive terminal of a battery cell and a casing of the battery cell as well as between a negative terminal of the battery cell and the casing (e.g., can). Alternatively, a conductive component (e.g., a conductive piece), other than the battery cell casing, may be utilized to establish the electrical connection. Accordingly, an electrical connection may be established between the positive cell and the negative cell, thereby triggering a short circuit.

<FIG> is a side view of a battery cell <NUM> that may include an overcharge protection assembly <NUM> to prevent thermal runaway during overcharge tests according to an example useful for understanding the invention. The battery cell <NUM> may be used in the lithium-ion battery module <NUM> that supplies power to an xEV. It should be noted that while the current discussion focuses on an overcharge protection assembly in a lithium-ion battery cell <NUM>, aspects of the overcharge protection assembly may be employed in any suitable battery cell that undergoes overcharge tests.

As shown in <FIG>, the battery cell <NUM> includes a positive terminal <NUM> and a negative terminal <NUM>. The battery cell <NUM> illustrated in <FIG> includes a neutral can (e.g., casing) because both the positive terminal <NUM> and the negative terminal <NUM> are electrically insulated from a casing <NUM> of the battery cell <NUM> (e.g., the casing <NUM> includes an electrically conductive material). The casing <NUM> may be used to establish an electrical connection between the positive terminal <NUM> and the negative terminal <NUM>, or a conductive piece attached to the battery cell <NUM> may be used instead of the casing <NUM> to form the electrical connection. The positive terminal <NUM> may include a first insulative gasket <NUM> configured to prevent electrical current from flowing from the positive terminal <NUM> to the casing <NUM>, or vice versa. Similarly, the negative terminal <NUM> may include a second insulative gasket <NUM> that prevents electrical current from flowing from the negative terminal <NUM> to the casing <NUM>, or vice versa. A portion of the casing <NUM> is non-conductive and prevents electrical current from flowing from the positive and negative terminals <NUM>, <NUM> or to conductive parts of the casing <NUM>. Accordingly, a conductive piece may be used to trigger the external short circuit and to establish the electrical connection between the positive and negative terminals <NUM>, <NUM>.

Additionally, <FIG> shows the overcharge protection assembly <NUM> having a vent flap <NUM>, a first conductive spring <NUM>, a second conductive spring <NUM>, and an insulative component <NUM>. The first conductive spring <NUM> may be electrically coupled to the positive terminal <NUM> and the second conductive spring <NUM> may be electrically coupled to the negative terminal <NUM>. The first and second conductive springs <NUM>, <NUM> may be disposed over the positive and/or negative terminals <NUM>, <NUM> via a hole or opening in the first and second conductive springs <NUM>, <NUM> that is configured to receive the positive and/or negative terminals <NUM>, <NUM>. Further, the first and second conductive springs <NUM>, <NUM> may be electrically coupled to the positive and/or negative terminals <NUM>, <NUM> via a weld (e.g., a laser weld). Alternatively, the first and second conductive springs <NUM>, <NUM> may be electrically coupled to the positive and/or negative terminals <NUM>, <NUM> via a fastener (e.g., screw or bolt). The first and second conductive springs <NUM>, <NUM> may be electrically coupled to the positive and/or negative terminals <NUM>, <NUM> using any suitable technique for establishing an electrical connection between the positive and/or negative terminals <NUM>, <NUM> and the first and second conductive springs <NUM>, <NUM>.

Additionally, the first and second conductive springs <NUM>, <NUM> may include a conductive metal (e.g., aluminum or copper) such that an electrical connection may be established between the first conductive spring <NUM> and the casing <NUM> and/or between the second conductive spring <NUM> and the casing <NUM>. The first and second conductive springs <NUM>, <NUM> may be shaped in such a manner as to bias the first and second conductive springs <NUM>, <NUM> towards the casing <NUM>. For example, when the first conductive spring <NUM> is coupled to the positive terminal <NUM>, a first recessed portion <NUM> of the first conductive spring <NUM> may be driven towards the casing <NUM>. When the first recessed portion <NUM> contacts the casing <NUM>, an electrical connection may be established between the positive terminal <NUM> and the casing <NUM>. Similarly, when the second conductive spring <NUM> is coupled to the negative terminal <NUM>, a second recessed portion <NUM> of the second conductive spring <NUM> may be driven towards the casing <NUM>. When the second recessed portion <NUM> contacts the casing <NUM>, an electrical connection may be established between the negative terminal <NUM> and the casing <NUM>. When both the first and second recessed portions <NUM>, <NUM> contact the casing <NUM>, an electrical connection may be established between the positive terminal <NUM> and the negative terminal <NUM> via the casing <NUM>, which may trigger a short circuit.

However, it may be undesirable to trigger such a short circuit during normal operation of the battery cell <NUM> (e.g., when the battery cell <NUM> is not overcharged). Therefore, when a pressure in the casing <NUM> of the battery cell <NUM> is below the threshold value, it may be desirable to prevent formation of the electrical connection between the positive terminal <NUM> and the negative terminal <NUM>. Accordingly, to avoid establishing such an electrical connection during normal operation of the battery cell <NUM> (e.g., when the pressure in the casing <NUM> is below the threshold value), the insulative component <NUM> may be disposed between the first recessed portion <NUM> of the first conductive spring <NUM> and the casing <NUM>. Similarly, the insulative component may be disposed between the second recessed portion <NUM> of the second conductive spring <NUM> and the casing <NUM>. Alternatively, the insulative component <NUM> may be disposed between first recessed portion <NUM> or the second recessed portion <NUM> and the casing <NUM>. A second insulative component may also be utilized such that the insulative component <NUM> is disposed between the first recessed portion <NUM> and the casing <NUM>, and the second insulative component may be disposed between the second recessed portion <NUM> and the casing <NUM>.

The insulative component <NUM> and/or the second insulative component may include any material (e.g., plastic, ceramic, rubber, or another non-conductive material) that may be configured to prevent electrical current from flowing through the insulative component <NUM> and/or the second insulative component. Therefore, during normal operation of the battery cell <NUM>, the insulative component <NUM> and/or the second insulative component may block formation of the electrical connection between the positive terminal <NUM> and the negative terminal <NUM> (e.g., via the first and/or second conductive springs <NUM>, <NUM> and the casing <NUM>).

To produce electrical power in the battery cell <NUM>, one or more chemical reactions may take place. In some cases, such reactions form a gas (e.g., electrolyte) as a byproduct, and thus, the pressure within the casing <NUM> increases as more gas is produced. As a battery is overcharged, a temperature within the casing <NUM> may increase (e.g., from an excess of electric current), which in turn, may further increase the pressure in the casing <NUM>. The vent flap <NUM> may be calibrated to open (e.g., from a pressure force within the casing <NUM>) when the pressure within the casing <NUM> reaches a threshold value (e.g., a predetermined pressure value lower than a pressure known to indicate thermal runaway). When the vent flap <NUM> opens, gas within the casing <NUM> may escape (e.g., flow out of) into a housing of the battery module <NUM>.

<FIG> illustrates a side view of the battery cell <NUM> when the vent flap <NUM> is in an open position as a result of the pressure in the casing <NUM> reaching the threshold value. When the pressure in the casing <NUM> reaches the threshold value, the vent flap <NUM> may be configured to open as shown in <FIG>. Accordingly, the vent flap <NUM> may be biased towards a closed position (e.g., the position illustrated in <FIG>), but when the pressure in the casing <NUM> reaches the threshold value, the pressure force may be sufficient to overcome the bias and urge the vent flap <NUM> to the open position (e.g., the position shown in <FIG>).

The vent flap <NUM> may include a dual-door configuration such that the vent flap <NUM> opens down a crease (e.g., seam) in a center of the vent flap <NUM> (e.g., as if the vent flap <NUM> is connected to the casing <NUM> via two hinges, one for each door). For example, the vent flap <NUM> may include an indented crease (e.g., punctures in the vent flap that do not enable gas to pass out of the casing <NUM>) located in the center of the vent flap <NUM>. Accordingly, when the pressure in the casing <NUM> reaches the threshold value, the indented crease may break (e.g., rupture) and enable two doors of the vent flap <NUM> to open in a direction <NUM> to drive the insulative component <NUM> from between the first and/or second conductive springs <NUM>, <NUM> and the casing <NUM>. The crease may be thinner than other parts of the casing <NUM> and hinges on either side of the crease may also be thinner than the casing <NUM>, but not as thin as the crease. Alternatively, the vent flap <NUM> may be configured to open as if connected to the casing <NUM> via a single hinge (e.g., the vent flap <NUM> includes a single door). For example, the vent flap <NUM> may include a perimeter that includes an indented portion. Accordingly, when the pressure in the casing <NUM> reaches the threshold value, the indented portion may break (e.g., rupture) such that the entire vent flap <NUM> moves in the direction <NUM> to drive the insulative component <NUM> from beneath the first and/or second conductive springs <NUM>, <NUM>. In still further embodiments, the vent flap <NUM> may be configured to open in any suitable manner that may move the insulative component <NUM> from between the first conductive spring <NUM> and the casing <NUM> as well as from between the second conductive spring <NUM> and the casing <NUM>. In any event, when the vent flap <NUM> opens, the first and second conductive springs <NUM>, <NUM> may be configured to contact the casing <NUM> and establish an electrical connection between the positive terminal <NUM> and the negative terminal <NUM> via the casing <NUM>.

Accordingly, when the pressure in the casing <NUM> reaches the threshold value, the vent flap <NUM> may move to the open position (e.g., in the direction <NUM>) and move the insulative component <NUM> such that it no longer is positioned between the first and second conductive springs <NUM>, <NUM> and the casing <NUM>. When the insulative portion <NUM> is moved by the vent shield <NUM>, the first and second conductive springs <NUM>, <NUM> may contact the casing <NUM> and establish an electrical connection between the positive terminal <NUM> and the negative terminal <NUM>, via the casing <NUM>. The electrical connection may then cause a short circuit, which may lead to a discharge of electrical current from the cell <NUM>. Additionally, the short circuit may form an alternative path for charge current received from a power supply because a resistance of the short circuit may be substantially smaller than an internal resistance of the cell <NUM>. Such an external short circuit may avoid thermal runaway within the battery cell <NUM> when the battery cell <NUM> is overcharged (e.g., during an overcharge test). The external short circuit may be triggered via contact between the casing and the insulated positive and negative terminals <NUM>, <NUM>. However, an electrical connection between the positive and/or negative terminal <NUM>, <NUM> and an external load (e.g., another battery) is not disrupted (e.g., by breaking a connection between the terminal <NUM>, <NUM> and the external load) by the external short circuit. Rather, electrical connections between the positive and/or negative terminals <NUM>, <NUM> are maintained (e.g., a current capacity of the battery cell <NUM> is not substantially affected), while the external short circuit serves to discharge the battery cell <NUM> and avoid thermal runaway.

More than one battery cell may be included in the battery module <NUM>. The power supplied by the battery module <NUM> may be generated from each of the individual battery cells <NUM> included in the battery module <NUM>. Therefore, the battery cells <NUM> may be coupled to one another such that the power supplied by the battery module <NUM> is cumulative of a power associated with each of the individual battery cells <NUM>. Accordingly, it may be desirable to incorporate conductive springs into a bus bar that interconnects battery cells <NUM> in the battery module <NUM> to simplify assembly and manufacturing of the battery module <NUM>.

<FIG> illustrates a bus bar <NUM> that includes the first conductive spring <NUM> and a third conductive spring <NUM> incorporated into a single piece (e.g., the bus bar <NUM>). The third conductive spring <NUM> may be disposed on a terminal <NUM> (e.g., a positive terminal or a negative terminal) of a second battery cell <NUM> positioned adjacent to the battery cell <NUM>. For example, the first conductive spring <NUM> may be coupled to the positive terminal <NUM> of the battery cell <NUM>. Additionally, the third conductive spring <NUM> may be coupled to the terminal <NUM> of the second battery cell <NUM>. When the terminal <NUM> is a positive terminal, the battery cell <NUM> may be coupled to the second battery cell <NUM> in a parallel configuration via the bus bar <NUM>. Connecting two battery cells <NUM>, <NUM> in a parallel configuration may be desirable because a parallel connection enables the battery module <NUM> to have a voltage output equal to the sum of the individual battery cells <NUM> connected in parallel. Conversely, when the terminal <NUM> is a negative terminal of the second battery cell <NUM>, the battery cell may be coupled to the second battery cell <NUM> in a series configuration via the bus bar <NUM>.

The first conductive spring <NUM> may be electrically coupled to the positive terminal <NUM> or the negative terminal <NUM> of the battery cell <NUM>. Similarly, the third conductive spring <NUM> may be electrically coupled to the terminal <NUM> of the second battery cell <NUM>, which may be either positive or negative. The first conductive spring <NUM> may be disposed over a respective terminal <NUM>, <NUM> via a first opening <NUM> (e.g., a hole aligned with the respective terminal <NUM>, <NUM>) of the bus bar <NUM> configured to receive the positive and/or negative terminals <NUM>, <NUM>. Similarly, the third conductive spring <NUM> may be disposed over the terminal <NUM> via a second opening <NUM> (e.g., a hole aligned with the terminal <NUM>) of the bus bar <NUM> configured to receive the terminal <NUM> of the second battery cell <NUM>. Further, the first and/or third conductive springs <NUM>, <NUM> of the bus bar <NUM> may be electrically coupled to respective terminals <NUM>, <NUM>, and/or <NUM> via a weld (e.g., a laser weld). Alternatively, the first and third conductive springs <NUM>, <NUM> of the bus bar <NUM> may be electrically coupled to the respective terminals <NUM>, <NUM>, and/or <NUM> via a fastener (e.g., screw or bolt). In still further embodiments, the first and third conductive springs <NUM>, <NUM> of the bus bar <NUM> may be secured to the respective terminals <NUM>, <NUM>, and/or <NUM> using any suitable technique for establishing an electrical connection between the respective terminals <NUM>, <NUM>, and/or <NUM> and the first and third conductive springs <NUM>, <NUM>.

<FIG> illustrates another overcharge protection assembly <NUM>. As shown in <FIG>, the first and second conductive springs <NUM>, <NUM> may not be directly coupled to the positive terminal <NUM> and the negative terminal <NUM>, respectively. Rather, intermediate components (e.g., terminal pads) may be directly coupled to the terminals <NUM>, <NUM>, as well as to the first and second conductive springs <NUM>, <NUM>. Therefore, a first terminal pad <NUM> may be coupled to the positive terminal <NUM> at a first end <NUM> of the first terminal pad <NUM> and to the first conductive spring <NUM> at a second end <NUM> of the first terminal pad <NUM>. Similarly, a second terminal pad <NUM> may be coupled to the negative terminal <NUM> at a first end <NUM> of the second terminal pad <NUM> and to the second conductive spring <NUM> at a second end <NUM> of the second terminal pad <NUM>. The terminal pads <NUM>, <NUM> may include "Z"-shaped cross-sections. Accordingly, the terminal pads <NUM>, <NUM> may be configured to couple two components that are positioned on different planes (e.g., two components with different heights). For example, the positive terminal has an end <NUM> that lies on a different plane than the first conductive spring <NUM> when it contacts the casing <NUM>. Therefore, the "Z" shape of the terminal pads <NUM>, <NUM> may enable such components to be electrically coupled to one another.

As shown in <FIG>, the first terminal pad <NUM> is coupled to the first conductive spring <NUM> via a TOXD joint, which is a registered trademark of TOXD PRESSOTECHNIK L. Additionally, the second terminal pad <NUM> is coupled to the second conductive spring <NUM> via a TOXD joint. A TOXD joint may be a joint between two components that secures the two components together. Additionally, when the two components include a conductive material, an electrical connection may also be established between the two components via the TOPX joint. Alternatively, the terminal pads <NUM>, <NUM> may be coupled to the conductive springs <NUM>, <NUM> via welding (e.g., laser welding) and/or a fastener (e.g., rivets, screws, bolts).

Additionally, the terminal pads <NUM>, <NUM> may be coupled to the terminals <NUM>, <NUM> via a weld (e.g., laser weld) such that the terminal pads <NUM>, <NUM> are secured to the terminals <NUM>, <NUM> and form an electrical connection between the terminal pads <NUM>, <NUM> and the terminals <NUM>, <NUM>. In other embodiments, the terminal pads <NUM>, <NUM> may be coupled to the terminals <NUM>, <NUM> via fasteners (e.g., rivets, screws, or bolts), or any other suitable technique for securing and electrically coupling two components to one another.

The terminal pads <NUM>, <NUM> and the conductive springs <NUM>, <NUM> may further be secured to the battery cell <NUM> via various grooves <NUM> (e.g., fabricated recesses or slots) within a separate carrier device (e.g., a housing component coupled to the casing <NUM>). As shown in <FIG>, the terminal pads <NUM>, <NUM> and the conductive springs <NUM>, <NUM> may be substantially fixed within the grooves <NUM>. The grooves <NUM> may prevent substantial movement of the terminal pads <NUM>, <NUM> and/or the conductive springs <NUM>, <NUM> due to movement of the battery module <NUM> caused by the xEV, for example. When the vent flap <NUM> opens, the insulative component <NUM> may be removed from between the first and second conductive springs <NUM>, <NUM> and the casing <NUM> such that the first and second conductive springs <NUM>, <NUM> will both contact the casing <NUM> and trigger a short circuit.

<FIG> also illustrates another insulative component <NUM>. As shown, the insulative component <NUM> may include a first slot <NUM> configured to be positioned between the casing <NUM> and the first conductive spring <NUM> when the pressure within the casing <NUM> is below the threshold value (e.g., the vent flap <NUM> is closed). Similarly, the insulative component <NUM> may include a second slot <NUM> configured to be positioned between the casing <NUM> and the second conductive spring <NUM> when the pressure within the casing <NUM> is below the threshold value (e.g., the vent flap <NUM> is closed).

As discussed above, gas may be produced as a byproduct of the chemical reactions taking place within the casing <NUM>. Such gas may build up during an overcharge test, thereby increasing the pressure in the casing. When the pressure reaches or exceeds a threshold value, the vent flap <NUM> may be configured to open. Moreover, the pressure force applied to the vent flap <NUM> by the gas in the casing <NUM> may further be utilized to remove the insulative component <NUM> from between the casing <NUM> and the first and second conductive springs <NUM>, <NUM>. For example, when the vent flap <NUM> opens, doors of the vent flap <NUM> may press against the insulative component <NUM> and drive the insulative component <NUM> in a direction <NUM>. Accordingly, the first slot <NUM> may be removed from the position between the first conductive spring <NUM> and the casing <NUM> and the second slot <NUM> may be removed from the position between the second conductive spring <NUM> and the casing <NUM>. Therefore, the first and second conductive springs <NUM>, <NUM> may then contact the casing <NUM>, which may establish an electrical connection between the positive terminal <NUM> and the negative terminal <NUM>. Such an electrical connection may trigger an external short circuit, which may discharge the battery cell <NUM>. It may be desirable to trigger the external short circuit before an internal short circuit (e.g., thermal runaway) occurs because the internal short circuit (e.g., thermal runaway) may cause permanent damage to the battery cell <NUM> and/or render the battery cell <NUM> inoperable.

<FIG> illustrates a perspective view of the battery cell <NUM> and the overcharge protection assembly <NUM> of <FIG>. As can be seen in <FIG>, a separate carrier <NUM> is attached to the battery cell <NUM>. The separate carrier <NUM> may house the positive terminal <NUM>, the negative terminal <NUM>, the first conductive spring <NUM>, the second conductive spring <NUM>, the insulative component <NUM>, as well as other components of the battery cell <NUM> that may be positioned proximate to the vent flap <NUM>. The separate carrier <NUM> may include an insulative material (e.g., a material that prevents or blocks electrical current from flowing through it). For example, it may be desirable to utilize an insulative material to construct the separate carrier <NUM> to avoid inadvertent short circuits (e.g., the separate carrier may block metal particles from contacting the positive terminal <NUM> and/or the negative terminal <NUM>). Additionally, when both the first and second conductive springs <NUM>, <NUM> are housed within the separate carrier <NUM>, a short circuit may be avoided even when the first and/or second conductive springs <NUM>, <NUM> contact the separate carrier <NUM>.

The separate carrier <NUM> may include protrusions <NUM> that hold the insulative component <NUM> in place. For example, the battery cell <NUM> may be disposed within the battery module <NUM>, which may be utilized to power an xEV. As the xEV moves, the xEV may subject the battery module <NUM> to various vibrations and/or other disturbances that may cause the insulative component <NUM> to become misaligned with the vent flap <NUM>. Accordingly, the protrusions <NUM> may provide a barrier to movement of the insulative component <NUM> in the direction <NUM>, such that the protrusions <NUM> may prevent the insulative component <NUM> from enabling the first and second conductive springs <NUM>, <NUM> to contact the casing <NUM> inadvertently (e.g., due to a bump in the road or other vibration). It should be noted that the force applied by the vent flap <NUM> to the insulative component <NUM> may be sufficient to move the insulative component in the direction <NUM> past the protrusions <NUM>. The protrusions <NUM> may therefore be configured to prevent the insulative component <NUM> from moving in the direction <NUM> unless a sufficient force is applied by the vent flap <NUM>.

Additionally, <FIG> illustrates the insulative component <NUM> having an opening <NUM>. The opening <NUM> may enable gas to flow from the casing <NUM> into the housing of the battery module <NUM> when the vent flap <NUM> is open. It should be noted that, alternatively, the insulative component <NUM> may not include the opening <NUM>. For example, when the insulative component <NUM> moves in the direction <NUM>, a gap may be formed between the vent flap <NUM> and the insulative component <NUM>. In particular, the gap may be sufficient to enable gas to flow out of the casing <NUM>, around the insulative component <NUM>, and into the housing of the battery module <NUM>.

<FIG> illustrates another insulative component <NUM> of <FIG> and <FIG>. In <FIG>, the insulative component <NUM> may include a length <NUM> and a width <NUM>. The length <NUM> and the width <NUM> of the insulative component <NUM> may be configured to ensure that the insulative component <NUM> will move in the direction <NUM> when the vent flap <NUM> opens. A smaller (e.g., shorter length <NUM> and/or width <NUM>) insulative component may facilitate movement of the insulative component <NUM> in the direction <NUM> when compared to a larger (e.g., longer length <NUM> and/or width <NUM>) insulative component subjected to the same force. Therefore, shortening the width <NUM> of the insulative component <NUM> may be desirable.

As shown in <FIG>, the separate carrier <NUM> coupled to the battery cell <NUM> may include a narrow portion <NUM>. The narrow portion <NUM> may be adjacent to the vent flap <NUM> such that the narrow portion <NUM> of the separate carrier <NUM> houses just the insulative component <NUM>. The narrow portion <NUM> may be desirable when the insulative component <NUM> may include a shorter width <NUM>. For example, the narrow portion <NUM> may enable the smaller insulative component <NUM> to be secured by the separate carrier <NUM>, while other components of the battery cell <NUM> may remain a standard size (e.g., other battery cell components are not modified). Accordingly, the configuration of <FIG> may enable the insulative component <NUM> to move in the direction <NUM> when a smaller force is applied to the insulative component <NUM> by the vent flap <NUM>.

<FIG> illustrates another insulative component <NUM> of the overcharge protection assembly <NUM> of <FIG>. The illustrated configuration of <FIG> shows that the insulative component <NUM> includes a first insulative member <NUM>, a second insulative member <NUM>, and an insulative bistable beam <NUM>. The insulative bistable beam <NUM> may be incorporated into the separate carrier <NUM> of the battery cell <NUM>. Alternatively, the insulative bistable beam <NUM> may be a separate component of the separate carrier <NUM>.

As used herein, the insulative bistable beam <NUM> may be a component that includes a first position <NUM> and a second position <NUM>. To transition from the first position <NUM> to the second position <NUM> a force may be exerted upon the insulative bistable beam <NUM>, which then causes the transition. For example, during normal operation of the battery cell <NUM> (e.g., when the pressure in the casing <NUM> is below the threshold value), the insulative bistable beam <NUM> may be in the first position <NUM>. The insulative bistable beam <NUM> may be configured to remain in the first position <NUM> until a force from the vent flap <NUM> acts upon the insulative bistable beam <NUM>, thereby driving the insulative bistable beam <NUM> to the second position <NUM>. Accordingly, the insulative bistable beam <NUM> may be configured to withstand outside forces acting upon the battery module <NUM> caused by movement of the xEV, for example. In certain embodiments, once the insulative bistable beam <NUM> reaches the second position <NUM>, the insulative bistable beam <NUM> may not be configured to return to the first position <NUM> (e.g., the transition from the first position <NUM> to the second position <NUM> is irreversible).

The first insulative member <NUM> and the second insulative member <NUM> may be coupled to the insulative bistable beam <NUM>. The insulative bistable beam <NUM> may include grooves <NUM> configured to receive the first and second insulative members <NUM>, <NUM>. Further, the first and second insulative members <NUM>, <NUM> may be secured in the grooves <NUM> via an adhesive (e.g., glue, epoxy, or tape), via a fastener (e.g., a screw, a bolt, or a rivet), or via a heat seal. Alternatively, the first and second insulative members <NUM>, <NUM> may be configured to couple to the insulative bistable beam <NUM> using any suitable technique.

As shown in <FIG>, the first insulative member <NUM> is disposed between the first conductive spring <NUM> and the casing <NUM> when the insulative bistable beam <NUM> is in the first position <NUM>. Similarly, the second insulative member <NUM> is disposed between the second conductive spring <NUM> and the casing <NUM> when the insulative bistable beam <NUM> is in the first position <NUM>. When the pressure within the casing <NUM> reaches the threshold level, the vent flap <NUM> may open, which may then apply a force to the insulative bistable beam <NUM> causing the insulative bistable beam <NUM> to move in the direction <NUM> from the first position <NUM> to the second position <NUM>. Accordingly, when the insulative bistable beam <NUM> moves towards the second position <NUM>, the insulative bistable beam <NUM> may pull the first and second insulative members <NUM>, <NUM> out from between the first and second conductive springs <NUM>, <NUM> and the casing <NUM>. The first and second conductive springs <NUM>, <NUM> may then contact the casing <NUM>, thereby establishing an electrical connection between the positive terminal <NUM> and the negative terminal <NUM>. Establishing such an electrical connection may trigger an external short circuit, which may discharge the battery cell <NUM> and prevent thermal runaway during an overcharge test.

The insulative component <NUM> may include the insulative bistable beam <NUM> and a single insulative member. Accordingly, the single insulative member may be coupled to the insulative bistable beam <NUM>. When the insulative bistable beam <NUM> is in the first position <NUM>, the single insulative member may be disposed between the first conductive spring <NUM> and the casing <NUM> and between the second conductive spring <NUM> and the casing <NUM>. Conversely, when the insulative bistable beam <NUM> moves to the second position <NUM>, the single insulative member may be pulled by the bistable beam <NUM> from between the first conductive spring <NUM> and the casing <NUM> and from between the second conductive spring <NUM> and the casing <NUM>. In such configurations that include the single insulative member, the groove <NUM> may serve as a hinge joint to secure the single insulative member to the insulative bistable beam <NUM> and to facilitate the insulative bistable beam's <NUM> transition between positions <NUM> and <NUM>. <FIG> illustrates a perspective view of the insulative component <NUM> of <FIG> in the first position <NUM>. For example, the insulative bistable beam <NUM> may include a first arm <NUM>, a second arm <NUM>, and an elbow <NUM>, where the elbow <NUM> connects the first arm <NUM> and the second arm <NUM> to one another. As the insulative bistable beam <NUM> moves from the first position <NUM> to the second position <NUM>, the elbow moves in the direction <NUM>. The elbow <NUM> may be at a lowest position with respect to the arms <NUM>, <NUM> when the insulative bistable beam <NUM> is in the first position <NUM>, and the elbow <NUM> may be at a highest position with respect to the arms <NUM>, <NUM> when the insulative bistable beam <NUM> is in the second position <NUM>. As illustrated in <FIG>, the elbow <NUM> is at the lowest point with respect to the arms <NUM>, <NUM>, and thus, is in the first position <NUM>. When the pressure in the casing <NUM> reaches the threshold level, the vent flap <NUM> may open and drive the insulative bistable beam <NUM> to the second position <NUM>. Accordingly, the elbow <NUM> may transition to the highest position with respect to the arms <NUM>, <NUM> upon reaching the second position <NUM>.

<FIG> illustrates the overcharge protection assembly <NUM> according to the present invention that may utilize a casing <NUM> having an insulative material (e.g., a material that prevents electrical current from readily flowing through it). In regards to the discussion related to <FIG>, the casing <NUM> included an electrically conductive material to establish the electric pathway between the positive terminal <NUM> and the negative terminal <NUM> when the conductive springs <NUM>, <NUM> contacted the casing <NUM>. However, in the illustrated embodiment of <FIG>, the casing <NUM> may include an electrically insulative material and the overcharge protection assembly <NUM> may still create an external short circuit to prevent thermal runaway during an overcharge test.

For example, the overcharge protection assembly <NUM> of <FIG> includes a conductive bistable arc <NUM>. Additionally, the separate carrier <NUM> (e.g., the separate carrier <NUM> including insulative material) includes a first notch <NUM> and a second notch <NUM> configured to retain the conductive bistable arc <NUM> in a first position <NUM> when the pressure in the casing <NUM> is below the threshold value. For example, a first end <NUM> of the conductive bistable arc <NUM> is disposed in the first notch <NUM> and a second end <NUM> of the conductive bistable arc <NUM> is disposed in the second notch <NUM>. In certain embodiments, the first notch <NUM> may also provide support for the first conductive spring <NUM> (e.g., secure the first conductive spring <NUM> such that it remains substantially stationary with respect to the separate carrier <NUM>). Similarly, the second notch <NUM> may provide support for the second conductive spring <NUM> (e.g., secure the second conductive spring <NUM> such that it remains substantially stationary with respect to the separate carrier <NUM>).

It should be noted that the separate carrier <NUM>, as well as the first notch <NUM> and the second notch <NUM> include an insulative material. Therefore, an electrical connection is absent between the conductive bistable arc <NUM> and the first and second conductive springs <NUM>, <NUM> when the pressure in the casing <NUM> is below the threshold value.

In certain embodiments, the conductive bistable arc <NUM> may be configured to contact the vent flap <NUM> when the conductive bistable arc <NUM> is in the first position <NUM>. In other embodiments, a gap may be formed between the conductive bistable arc <NUM> and the vent flap <NUM> when the conductive bistable arc <NUM> is in the first position <NUM>. In any event, the vent flap <NUM> is configured to apply a force to the conductive bistable arc <NUM> when the vent flap <NUM> opens (e.g., as a result of the pressure in the casing <NUM> reaching or exceeding the threshold value) and drive the conductive bistable arc <NUM> to a second position <NUM>.

As shown in the illustrated embodiment of <FIG>, the first and second conductive springs <NUM>, <NUM> are substantially straight (e.g., parallel to the casing <NUM>). Therefore, the first and second conductive springs <NUM>, <NUM> may not be biased towards a surface of the casing <NUM> in the illustrated embodiment of <FIG>. Rather, the first and second conductive springs <NUM>, <NUM> may be positioned in such a manner as to enable the conductive bistable arc <NUM> to contact both the first conductive spring <NUM> and the second conductive spring <NUM> when the conductive bistable arc <NUM> is in the second position <NUM>. Accordingly, when the conductive bistable arc <NUM> is in the second position <NUM>, the conductive bistable arc <NUM> forms the electrical connection between the first conductive spring <NUM> and the second conductive spring <NUM> (e.g., as opposed to the casing <NUM> in the embodiments illustrated in <FIG>). Therefore, when the conductive bistable arc <NUM> is in the second position <NUM>, an electrical connection is established between the positive terminal <NUM> and the negative terminal <NUM> via the first and second conductive springs <NUM>, <NUM> as well as the conductive bistable arc <NUM>.

In the embodiment illustrated in <FIG>, the casing <NUM> is not utilized to establish the electrical connection between the positive terminal <NUM> and the negative terminal <NUM>. Therefore, the casing <NUM> may include an insulative material, while the external short circuit is still formed (e.g., via the conductive bistable arc <NUM>) to prevent thermal runaway during an overcharge test. Moreover, an electrical connection between the positive terminal <NUM> and/or the negative terminal <NUM> and an external load is not disrupted. Accordingly, the battery cell <NUM> may avoid thermal runaway while also maintaining a current capacity level (e.g., the current capacity may not decrease).

<FIG> illustrates a perspective view of the overcharge protection assembly <NUM> of <FIG>. As shown in <FIG>, the conductive bistable arc <NUM> is in the first position <NUM> because the conductive bistable arc <NUM> is concave with respect to the casing <NUM>. Conversely, when the conductive bistable arc <NUM> is in the second position <NUM>, the conductive bistable arc <NUM> is convex with respect to the casing <NUM>.

<FIG> illustrates a graphical representation <NUM> of data from an overcharge test performed on a battery cell utilizing the overcharge protection assembly <NUM> of the present disclosure. The graph <NUM> shows an example of an effect of the overcharge protection assembly <NUM> on a battery cell during an overcharge test. The graph <NUM> includes a first curve <NUM> representing voltage <NUM> as a function of state of charge (SOC) <NUM> for a battery cell that includes the overcharge protection assembly <NUM>. The first curve <NUM> shows how voltage <NUM> generally increases as SOC <NUM> increases for the battery cell including the overcharge protection assembly <NUM>. However, as SOC <NUM> continues to increase, the pressure in the casing <NUM> of the battery cell also increases. As shown in the illustrated embodiment of <FIG>, when the pressure reaches the threshold value, the overcharge protection assembly <NUM> triggers an external short circuit by creating an electrical connection between the positive terminal <NUM> and the negative terminal <NUM> (e.g., via the casing <NUM> or the conductive bistable arc <NUM>). Therefore, at point <NUM>, the short circuit occurs and the voltage <NUM> of the battery cell decreases significantly. Accordingly, the battery cell <NUM> discharges, thereby preventing thermal runaway.

Conversely, a second curve <NUM> shows an effect on a battery cell that does not include the overcharge protection assembly <NUM> of the present disclosure. Accordingly, the voltage <NUM> continues to increase beyond the point <NUM> as the SOC <NUM> increases. Eventually, thermal runaway occurs. Additionally, graph <NUM> illustrates a third curve <NUM> representing a temperature <NUM> as a function of SOC <NUM> for a battery cell that includes the overcharge protection assembly <NUM>. As shown, the temperature <NUM> also increases as SOC <NUM> increases. Additionally, at the point <NUM> (e.g., when the external short circuit is triggered), the temperature <NUM> continues to increase. However, the temperature <NUM> does incur a significant spike. Rather, the temperature <NUM> increases to a maximum point, but eventually decreases. Accordingly, thermal runaway does not occur.

Claim 1:
A battery module (<NUM>), comprising:
- a plurality of battery cells (<NUM>) disposed in a housing of the battery module (<NUM>),
wherein each of the plurality of battery cells (<NUM>) comprises a positive terminal (<NUM>), a negative terminal (<NUM>), an overcharge protection assembly (<NUM>), and a casing (<NUM>);
wherein the overcharge protection assembly (<NUM>) comprises a vent, a first conductive component (<NUM>), a second conductive component (<NUM>), and a conductive bistable arc (<NUM>),
wherein the first conductive component (<NUM>) is electrically coupled to the positive terminal (<NUM>),
wherein the second conductive component (<NUM>) is electrically coupled to the negative terminal (<NUM>),
wherein the vent comprises a vent flap (<NUM>) configured to transition from a closed position to an open position to drive the conductive bistable arc (<NUM>) into contact with both the first and second conductive components (<NUM>, <NUM>) when a pressure in the casing (<NUM>) exceeds a threshold value, wherein the conductive bistable arc (<NUM>) comprises a first position (<NUM>) and a second position (<NUM>), the conductive bistable arc (<NUM>) is in the first position (<NUM>) when the pressure in the casing (<NUM>) is at or below the threshold value, and the conductive bistable arc (<NUM>) is driven to the second position (<NUM>) by the vent flap (<NUM>), when the pressure in the casing (<NUM>) exceeds the threshold value,
wherein the conductive bistable arc (<NUM>) is secured in the first position (<NUM>) by a first notch (<NUM>) and a second notch, and wherein the first notch (<NUM>) and the second notch (<NUM>) each comprise an insulative material, and
wherein the conductive bistable arc (<NUM>) is concave with respect to the casing (<NUM>), when the conductive bistable arc (<NUM>) is in the first position (<NUM>), and wherein the conductive bistable arc (<NUM>) is convex with respect to the casing (<NUM>), when the conductive bistable arc (<NUM>) is in the second position (<NUM>), and
wherein the first conductive component (<NUM>) and the second conductive component (<NUM>) are substantially parallel to the casing (<NUM>).