SYSTEM AND METHOD WITH A DIRECT CURRENT TO DIRECT CURRENT (DC/DC) PRE-CHARGER

A battery system may include a battery pack including a direct current to direct current (DC/DC) pre-charger and a battery cell. The battery pack may include a positive terminal and a negative terminal of the battery cell electrically connected to a first positive bidirectional terminal and a first negative bidirectional terminal, respectively. The positive terminal and the negative terminal may be electrically connected to a positive output terminal and a negative output terminal, respectively, via a positive electrical connection and a negative electrical connection. The battery pack may further include a high voltage bus bar electrically connected to the positive output terminal and the negative output terminal and a communication bus bar electrically connected to the DC/DC pre-charger. The DC/DC pre-charger may pre-charge the high voltage bus bar and/or discharge the high voltage bus bar via a second positive bidirectional terminal and a second negative bidirectional terminal.

TECHNICAL FIELD

Embodiments of this disclosure relate to a battery system and, more particularly, to a battery system that includes a direct current to direct current (DC/DC) pre-charger.

BACKGROUND

High voltage (HV) direct current (DC) systems, such as those used for battery electric vehicles, maintain isolation of the battery from the high voltage distribution and devices (e.g., on a HV bus bar) while not in operation. Prior to the start of operations, the voltage on the HV bus bar has to be brought up to within a tolerance of the battery voltage to prevent excessive current flow when the contactors are closed.

The conventional method of accomplishing this task is to use a high-wattage resistor and a contactor to bypass the main battery contactors. Depending on the design, this permits a limited amount of current to pass through and charge up a capacitance in the HV bus bar, thereby preventing the excessive current flow on closure of the battery contactors.

This method may be sufficient when the capacitance of the HV bus bar is known beforehand but can present problems if there are changes to the external configuration or deviations in the resistor, either as a result of damage to the device or manufacturing defects. Additionally, the resistor and contactor arrangement provides protective isolation for the battery system only so long as the contactor itself remains functional and failure of the contactor may result in the pre-charge circuit being in a constant on state, resulting in a loss of isolation between the HV bus bar and the battery system. As such, potentially dangerous DC voltage may be present on the HV bus bar even with the system powered off. Embodiments of the current disclosure may address these limitations and/or other problems in the art.

SUMMARY

Embodiments of the present disclosure relate to, among other things, battery systems for electric vehicles. Each of the embodiments disclosed herein may include one or more of the features described in connection with any of the other disclosed embodiments.

In one aspect, a battery system may include at least one battery pack including a direct current to direct current (DC/DC) pre-charger and at least one battery cell. The at least one battery pack may include a positive terminal and a negative terminal of the at least one battery cell electrically connected to a first positive bidirectional terminal and a first negative bidirectional terminal, respectively, associated with the DC/DC pre-charger. The positive terminal and the negative terminal may be electrically connected to a positive output terminal and a negative output terminal, respectively, of the at least one battery pack via at least one positive electrical connection and at least one negative electrical connection. The at least one battery pack may further include a high voltage bus bar electrically connected to the positive output terminal and the negative output terminal of the at least one battery pack and a communication bus bar electrically connected to the DC/DC pre-charger. The DC/DC pre-charger may be configured to pre-charge the high voltage bus bar and/or discharge the high voltage bus bar via a second positive bidirectional terminal and a second negative bidirectional terminal.

In another aspect, a method of using a direct current to direct current (DC/DC) pre-charger located within a battery pack of a battery system may be performed. The DC/DC pre-charger may be electrically connected to one or more battery cells of the battery pack. The method may include receiving, by a computing system, a signal to control the DC/DC pre-charger and controlling one or more battery pack contactors or the DC/DC pre-charger based on one or more parameters. The method may further include receiving or reporting data associated with operation of the DC/DC pre-charger while controlling the one or more battery pack contactors and the DC/DC pre-charger.

In yet another aspect, a method of using a direct current to direct current (DC/DC) pre-charger located within a battery pack of a battery system may be performed. The DC/DC pre-charger may be electrically connected to one or more battery cells of the battery pack. The method may include sampling, by a computer system, a voltage on a DC bus bar of the battery system and generating or transmitting limits for an operation of the DC/DC pre-charger. The method may further include receiving data related to the operation of the DC/DC pre-charger and closing one or more battery contactors of the battery pack when the voltage reaches a target voltage.

DETAILED DESCRIPTION

The present disclosure describes a system and method for a battery system including a DC/DC pre-charger. While principles of the current disclosure are described with reference to an electric bus, it should be understood that the disclosure is not limited thereto. Rather, the systems and methods of the present disclosure may be used in any vehicle having a battery system (e.g., electric vehicle, electric machine, electric tool, electric appliance, etc.). As used herein, the term “electric vehicle” includes any vehicle or transport machine that is driven at least in part by electricity (e.g., hybrid vehicles, all-electric vehicles, etc.). Heavy duty electric vehicles (e.g., electric buses, electric trucks, electric airplanes, electric boats, etc.) may store and/or consume a large amount of energy compared to smaller electric vehicles (e.g., electric cars, electric bicycles or motorcycles, electric carts, etc.).

In this disclosure, relative terms, such as “about,” “substantially,” or “approximately” are used to indicate a possible variation of ±10% of a stated value.

Any implementation described herein as exemplary is not to be construed as preferred or advantageous over other implementations. Rather, the term “exemplary” is used in the sense of example or illustrative.

FIGS.1A and1Billustrate an electric vehicle in the form of a bus10.FIG.1Ashows the bus10with its roof visible, andFIG.1Bshows the bus10with its undercarriage visible. In the discussion below, reference will be made to bothFIGS.1A and1B. The bus10may include a body12enclosing a space for passengers. In some embodiments, some (or substantially all) parts of the body12may be fabricated using one or more composite materials to reduce the weight of the bus10. Without limitation, the body12of the bus10may have any size, shape, and configuration. In some embodiments, the bus10may be a low-floor electric bus. In a low-floor electric bus, there may be no stairs at the front and/or the back doors of the bus10. In such a bus10, the floor may be positioned close to the road surface to ease entry and exit into the bus10. In some embodiments, the floor height of the low-floor bus may be about 30-45 centimeters from the road surface.

The bus10may include a powertrain24that propels the bus10along a road surface. The powertrain24may include one or more electric motors22that generate power, and a transmission that transmits the power to a pair of drive wheels (e.g., wheels18) of the bus10. A battery system14may store electrical energy to power the electric motors22of the powertrain24. In some embodiments, the batteries of the battery system14may be configured as a plurality of battery packs20positioned in cavities located under the floor of the bus10. In some embodiments, some or all of the battery packs20may be positioned elsewhere (e.g., roof) on the bus10. The batteries of the battery system14may have any chemistry and construction. The battery chemistry and construction may activate fast charging of the batteries. In some embodiments, the batteries may be lithium titanate oxide (LTO) batteries. In some embodiments, the batteries may be nickel metal cobalt oxide (NMC) batteries. It is also contemplated that, in some embodiments, the batteries may include multiple different chemistries.

The bus10may include a charging interface. For example, the bus10may include a charge port (e.g., an electric socket) that is configured to receive a charging plug and charge the bus10using power from a utility grid. In such embodiments, the bus10may be charged by connecting the plug to the socket. In some embodiments, the charge port may be a standardized charge port (e.g., a Society of Automotive Engineers (SAE) J1772 charge port) that is configured to receive a corresponding standardized connector (e.g., a SAE J1772 connector). However, in general, the charge port and the mating connector may be of any type and form (custom design or standardized). As illustrated inFIG.1A, to protect the charge port from the environment (rain, snow, debris, etc.), a hinged lid16may cover the charge port when not in use. Additionally, or alternatively, a charging interface may be provided on the roof of the bus10(not illustrated inFIGS.1A and1B) to charge the batteries of the battery system14. For example, the charging interface may include components that interface with a charging head (e.g., an inverted pantograph that interfaces with a set of rails mounted on the forward rooftop of the bus10) of an external charging station to charge the batteries.

FIG.2is a schematic illustration of an exemplary battery system14of the bus10ofFIGS.1A and1B, according to the present disclosure. The battery system14may include a plurality of battery packs20. Each battery pack20may include a plurality of battery modules34, and each battery module34may include a plurality of battery cells38arranged therein. InFIG.2, the inside structure of one of the battery packs20, and the inside structure of one of the battery modules34of the battery pack20, are shown to aid in the discussion below. The battery cells38may have any chemistry and construction. In some embodiments, the battery cells38may have a lithium-ion chemistry. Lithium-ion chemistry comprises a family of battery chemistries that employ various combinations of anode and cathode materials. In automotive applications, these chemistries may include lithium-nickel-cobalt-aluminum (NCA), lithium-nickel-manganese-cobalt (NMC), lithium-manganese-spinel (LMO), lithium titanate (LTO), and lithium-iron phosphate (LFP), for example. In consumer applications, the battery chemistry may also include lithium-cobalt oxide (LCO), for example.

The plurality of battery packs20of the battery system14may be connected together in series or in parallel. In some embodiments, these battery packs20may also be arranged in strings. For example, the battery system14may include multiple strings connected in parallel, with each string including multiple battery packs20connected together in series. Configuring the battery system14as parallel-connected strings may allow the bus10to continue operating with one or more strings disconnected if a battery pack20in a string fails or experiences a problem. The plurality of battery modules34in each battery pack20, and the plurality of battery cells38in each battery module34, may also be electrically connected together in series or parallel. In some embodiments, some of the battery modules34in a battery pack20may be connected together in series, and groups of the series-connected battery modules34connected together in parallel. Similarly, in some embodiments, a group of battery cells38in each battery module34may be connected together in series to form multiple series-connected groups of battery cells38, and these series-connected groups may be connected together in parallel. That is, some or all battery packs20in the battery system14may include both series-connected and parallel-connected battery modules34, and some or all battery modules34in each battery pack20may include both series-connected and parallel-connected battery cells38. In some embodiments, each battery pack20of the battery system14may be substantially identical (in terms of number of battery modules34, number of battery cells38in each battery module34, how the battery modules34are connected, etc.) to each other. In other embodiments, one or more of the battery packs20of the battery system14may have a different configuration than one or more other battery packs20of the battery system14.

In general, the battery packs20of the battery system14may be physically arranged in any manner. In some embodiments, the battery packs20may be arranged in a single layer on a common horizontal plane to decrease the height of the battery system14, so that it may be positioned under the floor of the low-floor bus10. For example, the battery packs20may have a height less than or equal to about 18 centimeters, to allow the battery system14to be accommodated under the floor of the low-floor bus10. The low height profile of the battery system14may allow the battery system14to be more aerodynamic, and may increase its surface area relative to the number of battery cells38, which may increase heat dissipation and improve temperature regulation. In general, the battery system14may be configured to store any amount of energy and to export or import electrical power (in terms of Watts (W)) at a voltage (V). Increasing the amount of energy stored in the battery system14may increase the distance that the bus10can travel between recharges. In some embodiments, the number of the battery packs20, the battery modules34, the battery cells38, and the chemistry of the battery cells38, etc. may be configured such that the total energy capacity of the battery system14may be between, for example, about 200-700 kilowatt hours (KWh).

In general, the battery system14may have any number (e.g., 1, 2, 3, 4, 6, 8, 10, etc.) of battery packs20. In some embodiments, the number of battery packs20in the battery system14may be between about 2 and 6. Each battery pack20may have a protective housing28that encloses the plurality of battery modules34(and other components of the battery pack20) therein. Although the battery pack20ofFIG.2is illustrated as including six battery modules34arranged in two columns, this is merely an example. In general, any number (e.g., 1, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, etc.) of battery modules34may be provided in a battery pack20, and each battery module34may include any number of battery cells38(e.g., 1, 100, 101, 200, 300, 400, 500, 600, 800, etc.) arranged in any manner. In some embodiments, the number of battery modules34in each battery pack20may be between about 10 and 20, and the number of battery cells38housed in each battery module34may be between about 400 and 700. In some embodiments, the battery modules34housed in the housing28of a battery pack20may be separated from each other with dividers (not shown) that provide electrical and thermal insulation. The dividers may protect the other battery modules34if any battery module34fails (e.g., experiences a high temperature event). The dividers may be made of a material that does not oxidize or otherwise become damaged when exposed to electrical arcs and/or high temperatures.

The housing28of each battery pack20may have a box-like structure, and may be shaped to allow the battery modules34of the battery pack20to be arranged in a single layer on a common horizontal plane to decrease the height of the battery pack20. In some embodiments, the housing28may be watertight (e.g., to about 1 meter) and may have a rating for dust and water resistance (e.g., an International Protection (IP)67rating). The housing28may be configured to contain any failures (e.g., electric arcs, fires, etc.) within the battery pack20in order to prevent damage to other battery packs20or other portions of the bus10if a component inside a battery pack20fails. In some embodiments, the housing28may be constructed of corrosion and puncture resistant materials. For example, the materials of which the housing28may be constructed may include composite materials, Kevlar, stainless steel, aluminum, high strength plastics, etc.

In addition to the battery modules34, the housing28may also enclose a battery management system (BMS)30that monitors or controls the operation of the battery modules34and a thermal management system32that assists in managing the temperature of the battery modules34of the battery pack20(i.e., heat, cool, etc.). As described in more detail elsewhere herein, the BMS30and/or one or more other pack controllers may monitor the state (e.g., humidity, state of charge (SOC), current, temperature, etc.) of the battery modules34and the battery cells38in the battery pack20, and may control the operations of the battery pack20to ensure that power is safely and efficiently directed into and out of the battery pack20. The thermal management system32may include components that circulate air and/or a liquid coolant to the battery modules34to heat or cool the battery modules34. These components may include, for example, circulating fans, coolant conduits, heat exchangers, etc. that assist in circulating air and/or a coolant through the battery modules34packaged in the housing28to manage the temperature of the battery pack20.

The battery system14may include an energy storage management (ESM) system26that communicates with the BMS30included in the battery pack20to control the operation of the battery system14on a per-battery pack20basis. The ESM system26may include circuit boards, electronic components, sensors, and controllers that monitor the performance of the components (e.g., the battery packs20, the battery modules34, and the battery cells38) of the battery system14based on sensor input (e.g., voltage, current, temperature, humidity, etc.), provide feedback (e.g., alarms, alerts, etc.), and control the operation of the battery system14for safe and efficient operation of the bus10. In some embodiments, the ESM system26may perform charge balancing between different battery packs20, battery modules34and/or battery cells38during recharging or during operation of the bus10. The ESM system26may also thermally and/or electrically isolate sections (e.g., battery cells38, battery modules34, battery packs20, etc.) of the battery system14when one or more sensor readings (e.g., temperature, etc.) exceed a threshold value. As will be described in more detail elsewhere herein, in some embodiments, the ESM system26may initiate or control energy discharge from all or selected battery packs20, battery modules34, or battery cells38based on the occurrence of predefined trigger events.

FIG.3is a schematic illustration of an exemplary battery module34of the battery system14ofFIG.2, according to the present disclosure. The battery module34includes a casing36that encloses the plurality of battery cells38of the battery module34therein. Similar to the housing28of the battery pack20, the casing36may be configured to contain any failures (e.g., electric arcs, fires, etc.) of the battery cells38of the battery module34within the casing36in order to prevent the damage from spreading to other battery modules34of the battery pack20. The casing36may be made of any material suitable for this purpose. In some embodiments, the casing36may be constructed of one or more of materials such as, for example, Kevlar, aluminum, stainless steel, composite materials, etc. In some embodiments, the casing36may be substantially air-tight to hermetically seal the battery cells38of the battery module34therein.

In general, the battery cells38may have any shape and structure (e.g., a cylindrical cell, a prismatic cell, a pouch cell, etc.). Typically, all the battery cells38of a battery module34may have the same shape. However, it is also contemplated that different shaped battery cells38may be packed together in the casing36of a battery module34. In addition to the battery cells38, the casing36may also include sensors (e.g., a temperature sensor, a voltage sensor, a humidity sensor, etc.) and controllers (e.g., a battery module controller44) that monitor and control the operation of the battery cells38. Although not illustrated, the casing36also may include electrical circuits (e.g., voltage and current sense lines, low voltage lines, high voltage lines, etc.), and related accessories (e.g., fuses, switches, etc.), that direct electrical current to and from the battery cells38during recharging and discharging.

As explained previously, the battery cells38of the battery module34may be electrically connected together in any manner (e.g., in parallel, in series, or in groups of series-connected battery cells38connected together in parallel). These battery cells38may also be physically arranged in any manner. In some embodiments, the battery cells38of a battery module34may be packed together tightly to fill the available volume within the casing36. In some embodiments, the battery cells38may be arranged together to form multiple groups (e.g., bricks) of battery cells38electrically connected together in series. The multiple bricks (each comprising multiple battery cells38electrically connected together) may then be electrically connected together (e.g., in series or parallel) and packaged together in the casing36. In some embodiments, one or more sensors may be associated with each brick of the battery module34. Terminals (e.g., positive and negative terminals) electrically connected to the battery cells38of the battery module34may be provided on an external surface of the casing36.

The casing36may also include a coolant loop46configured to circulate a coolant through the battery module34. The coolant loop46may comprise fluid conduits arranged to pass through, or meander (e.g., zigzag) through, the volume enclosed by the casing36. An inlet port40and an outlet port42of the casing36may fluidly couple the coolant loop46to a coolant circuit of the battery system14. The coolant may enter the coolant loop46through the inlet port40and may exit the casing36through the outlet port42. In some embodiments, where the battery module34is air cooled, the casing36may also include inlet and outlet vents configured to direct cooling air into and out of the casing36. In some embodiments, the coolant may cool all the battery modules34of a battery pack20before exiting the battery pack20. That is, the coolant loops46of the battery modules34of the battery pack20may be connected in series such that the coolant exiting one battery module34enters the coolant loop46of another battery module34. In some embodiments, coolant may be directed into each battery module34individually (for e.g., from a common coolant gallery of the battery pack20). In some embodiments, groups of battery modules34within a battery pack20may be fluidly connected in series and multiple series-connected battery modules34may be connected together in parallel.

During operation of the battery system14, the battery cells38of the battery module34release heat. This released heat may be transferred to the coolant circulating through the coolant loop46and then removed from the casing36along with the coolant. In general, any known fluid may be used as the coolant. In some embodiments, water (with suitable additives such as antifreeze, etc.) or another suitable liquid may be used as the coolant. The battery cells38of the battery module34may be arranged to enhance heat dissipation into the coolant circulating through the battery module34. For example, in some embodiments, the battery cells38may be in close thermal contact with the coolant loop46. In some embodiments, the battery cells38may be placed in close thermal contact with metal plates that serve as heat conducting pathways to the coolant loop46.

The battery module34may also include one or more heaters48positioned within the casing36(or in close thermal contact with the casing36). In general, any type of heating device (e.g., a resistance heater, a positive temperature coefficient (PTC) heater, etc.) may be used as the heater48. In some embodiments, the heater48may be a PTC cartridge heater. Unlike a resistance heater which generates heat at a constant rate, a PTC heater may use PTC resistive elements which generate heat at a lower rate at higher temperatures. Therefore, a PTC heater is self-regulating to a fixed working temperature.

In some embodiments, the heater48(or the multiple heaters48) of each battery module34may be powered solely by the battery cells38of that battery module34. The heater48may be activated by the battery module controller44and/or by another controller (e.g., the ESM system26, the BMS30, etc.) of the battery system14. When the heater48is activated, it generates heat using the energy stored in the battery cells38of that battery module34. Consequently, the stored energy (or SOC) of the battery cells38in the battery module34decrease as a result of activation of the heater48. The heat dissipated by the heater48may be removed from the battery module34by the circulating coolant (or by conduction). A temperature sensor (or thermistor) of the battery module34may monitor the heat dissipated by the heater48.

The heater48may be positioned at any location within the casing36. In general, the location of the heater48may be selected such that the maximum energy discharged by the heater48does not damage (or jeopardize the safety of) the battery cells38of the battery module34. Therefore, in some embodiments, the heater48may be spaced away from (i.e., not directly in contact with) the battery cells38such that the heater48is thermally isolated from the battery cells38. The location of the heater48may also be selected such that the dissipated heat can be easily transferred to the body of the battery pack20(thus allowing the heater48to dissipate more heat without a resulting increase in temperature). Therefore, in some embodiments, the heater48may be positioned in direct contact with the metal frame of the battery pack20to enhance heat conduction. In some embodiments, the heater48may be positioned close to (as illustrated inFIG.3) the coolant loop46of the battery module34so that the dissipated heat may be easily transferred to the coolant circulating through the coolant loop46. It is also contemplated that, in some embodiments, the heater48may be positioned within the coolant loop46(i.e., submerged in the coolant of the coolant loop46). In some embodiments, as illustrated inFIG.3, the heater48may be positioned about midway of the coolant loop46in the battery module34. That is, the heater48may be positioned proximate to (on within) the coolant loop46, and substantially equidistant from the inlet port40and the outlet port42.

Although a single heater48is illustrated inFIG.3, in some embodiments, multiple heaters (similar to the heater48) may be positioned within the casing36of each battery module34. Each of these multiple heaters48may be powered by the battery cells38of that battery module34so that activating these multiple heaters48may discharge energy from all the battery cells38at a faster rate as compared to a case when a single heater48is used. In some embodiments, a first group of battery cells38of the battery module34(e.g., a brick) may power a first heater48, and a second group of battery cells38of the battery module34may power a second heater48. In such an embodiment, activating the first heater48may selectively discharge energy from the first group of battery cells38, and activating the second heater48may selectively discharge energy from the second group of battery cells38. The multiple heaters48may be positioned adjacent to each other or spaced apart from each other in the casing36. In some embodiments, the multiple heaters48may be positioned such that desired regions of the battery module34can be selectively discharged by activating different heaters48.

As explained previously, the heater48may be activated by the BMS30alone or in cooperation with the battery module controller44and/or the ESM system26. In some embodiments, the BMS30may simultaneously activate the heaters48embedded in (inserted in, positioned in, included in, etc.) each battery module34of the battery system14to discharge energy from the battery cells38of every battery module34, and thereby, reduce the SOC of the entire battery system14. In some embodiments, the BMS30may selectively activate the heaters48embedded in selected battery modules34to preferentially discharge energy from (and thereby reduce the SOC of) the selected battery modules34. For example, if sensors detect that one battery module34of a battery pack20includes a damaged battery cell38, the BMS30may selectively activate the heaters48embedded in all the other battery modules34of the battery pack20(i.e., except the battery module34with the damaged battery cell38) to safely decrease the SOC of the battery pack20. In embodiments where multiple heaters48are embedded in a battery module34, the BMS30may also be configured to selectively activate some heaters48of the battery module34to preferentially discharge energy from selected battery cells38(e.g., bricks) of the battery module34.

The BMS30may activate the heaters48embedded in the battery modules34to discharge energy from (and thus decrease the SOC of) the battery system14of a stranded (or otherwise incapacitated) bus10before service personnel operate on (repair, remove the batteries from, etc.) the bus10. The battery system14of the bus10may store a relatively large amount of energy (e.g., between about 200-700 KWh). Operating on a bus10with such a large amount of stored energy may be undesirable. Dissipating the stored energy from the battery system14by activating the heaters48lowers the SOC of the battery system14. After the SOC of the battery system14has been lowered to a suitable level, the heaters48may be deactivated. Although the discussion above describes embedding a heater48in a battery module34of a battery pack20, this is merely exemplary. In general, any electric load may be embedded in a battery module34to selectively dissipate energy from the battery cells38of the battery module34

In general, the heat produced by the heaters48may be dissipated from the battery system14by conduction, convection, or radiation. The heaters48may be positioned in the battery modules34such that the heat produced by them can be removed without overheating the battery cells38of the battery module34. In some embodiments, the heat produced by the heaters48of a battery module34may be used to increase the temperature of the battery cells38of the battery module34. In some embodiments, the inlet port40and/or the outlet port42of the coolant loop46may be selectively opened and closed (e.g., using adjustable valves41and43shown by the dashed lines inFIG.3) by the BMS30, based on sensor readings (e.g., humidity, temperature, etc.) from within the battery module34. The BMS30may use these adjustable valves to redirect the coolant flow within the battery system14based on the local conditions within the battery modules34.

The implementation of a heater48in every battery module34of the battery system14(as opposed to providing a coolant heater external to the battery system14) may activate the battery cells38of the battery system14to be heated more quickly and efficiently. Further, locating the heater48to be substantially in the middle of the coolant loop46may activate the heat dissipated by the heater48to be distributed throughout the coolant loop46which may result in improved heating performance in a short amount of time.

The BMS30(and/or other controllers of the battery system14) may selectively activate the heaters48of a battery module34in response to any triggering event. In some embodiments, the triggering event may include input from a human operator or one or more sensors of the bus10. In response to the triggering signal, the BMS30may selectively activate one or more of the heaters48embedded in selected battery modules34(i.e., all or some of the battery modules34).

FIG.4is a schematic illustration of connections between the battery pack20ofFIG.2and peripheral devices or systems of the bus10ofFIGS.1A and1B, according to the present disclosure. As illustrated, the schematic inFIG.4includes the battery pack20, a high voltage (HV) bus bar50, a high voltage peripheral device or system52, a low voltage bus bar54, and a low voltage peripheral device or system56. The battery pack20may be electrically connected (e.g., through one or more electrical terminals62,66not illustrated inFIG.4) to the high voltage bus bar50. The high voltage bus bar50may provide one or more electrical connections between the battery pack20and the high voltage peripheral device or system52for carrying high voltage power (e.g., at greater than or equal to approximately 100 V) from the battery pack20to the high voltage peripheral device or system52. The high voltage peripheral device or system52may include, for example, devices or systems of the bus10used during operation of the bus10, such as the powertrain24, an heating, ventilation, and air conditioning (HVAC) system, an external DC/DC system, or the like.

Similarly, the battery pack20may be electrically connected to the low voltage bus bar54. The low voltage bus bar54may provide one or more electrical connections between the battery pack20and the low voltage peripheral device or system56for carrying low voltage power (e.g., at less than 100 V) from the battery pack20to the low voltage peripheral device or system56. The low voltage device or system56may include, for example, devices or systems that are operational when the bus10is not in use or is in an idle state, such as a fire suppression system, a security system, a lighting system, an indicator, a cooling pump, or the like. In some implementations, the low voltage device or system56may include any device or system of the bus10that does not operate on a high voltage energy storage system.

AlthoughFIG.4illustrates a single battery pack20, there may be multiple battery packs20electrically connected to the high voltage bus bar50or the low voltage bus bar54, and the multiple battery packs20may be organized into electrically parallel strings of battery packs20(with the battery packs20included in a string connected in series). In addition, the illustration of a single high voltage peripheral device or system52and a single low voltage peripheral device or system56is merely exemplary and some embodiments may include multiple high voltage peripheral devices or systems52and/or multiple low voltage peripheral devices or systems56.

FIG.5is a schematic illustration of a first configuration of a battery pack20of the battery system14ofFIG.2that includes a DC/DC pre-charger58, according to the present disclosure. The schematic illustrated inFIG.5includes a battery pack20, a BMS30, a battery module34, a high voltage bus bar50, a DC/DC pre-charger58, positive electrical connections60, positive electrical terminals62, negative electrical connections64, negative electrical terminals66, software layer communication lines68, a hardware layer communication line70, and battery pack contactors72.FIG.5illustrates a positive battery pack contactor72on a positive electrical connection60and a negative battery pack contactor72on a negative electrical connection64. Any of the components of a battery pack20may be configured for bidirectional current flow. For example, the components may be configured to import energy into the battery pack20or export energy out of the battery pack20(e.g., pre-charge or discharge a HV bus bar50).

The DC/DC pre-charger58may include one or more electrical circuits or electromechanical devices that pre-charges or discharges the HV bus bar50. For example, the DC/DC pre-charger58may draw power from the battery module34and may provide the power to the HV bus bar50in a controlled manner to charge capacitances on the HV bus bar50, thereby causing the voltage of HV bus bar50to rise. As one specific example of providing power in a controlled manner, the DC/DC pre-charger58may limit the maximum current throughput allowed (e.g., by limiting the pre-charge current to less than 5 amps (A)). As another specific example of providing power in a controlled manner, the DC/DC pre-charger58may ramp the amount of power provided to the HV bus bar50to a target amount by stepping through multiple intermediate voltage targets between the DC bus bar50voltage and the battery pack20voltage. For example, the DC/DC pre-charger58may start pre-charging operations at 0V and may increase the voltage to 10V, then to 25V, then to 50V, then to 100V in sequence and in a linear or exponential manner.

As illustrated inFIG.5, the DC/DC pre-charger58may be electrically connected to the battery module34via a positive electrical terminal62and a negative electrical terminal66, which may be separate components from the DC/DC pre-charger58, and thus separately controllable (e.g., control of on/off states) from the DC/DC pre-charger58. This electrical connection may meet electrical connections60,64from the battery module34between the battery module34and battery pack contactors72. The DC/DC pre-charger58may be further electrically connected to the electrical connections60,64from the battery module34between the battery pack contactors72and the electrical contactors62,66to the high voltage bus bar50. The DC/DC pre-charger58may include one or more relays and fuses (e.g., thermal fuses, thermal-magnetic breakers, pyrotechnic fuses, etc.) for protection from the high voltage connections to the battery module34and/or the high voltage bus bar50.

In some embodiments, the DC/DC pre-charger58may be located in an ancillary bay of the battery pack20. Additionally, or alternatively, the DC/DC pre-charger58may be included in the coolant system of the battery pack20. For example, the DC/DC pre-charger58may have one or more mechanical connections to the coolant loop46. This may reduce or eliminate a need for a DC/DC pre-charger58external to the battery pack20or for independent cooling channels, heat sinks, or fans for cooling the DC/DC pre-charger58.

The DC/DC pre-charger58may be bidirectional. For example, the DC/DC pre-charger58may receive electrical power from the battery module34and may control provisioning of the power to the high voltage bus bar50. Alternatively, the DC/DC pre-charger58may discharge power from the high voltage bus bar50.

The software layer communication lines68may include wired or wireless connections for bidirectional communication between the DC/DC pre-charger58and the BMS30. For example, the software layer communication lines68may include a controller area network (CAN) bus, a serial communication line, and/or the like. As described in more detail elsewhere herein, the BMS30may send instructions to the DC/DC pre-charger58to configure the DC/DC pre-charger58to operate in a particular manner and/or may receive data related to the operation of the DC/DC pre-charger58via the software layer communication lines68. The hardware communication line70may include an electrical connection for logic and/or voltage signaling from the BMS30to the DC/DC pre-charger58, or vice versa. As described in more detail elsewhere herein, the BMS30may provide enabling/disabling signaling to the DC/DC pre-charger58via the hardware communication line70. The software layer communication lines68and/or the hardware communication lines70may form a communication bus bar and the BMS30may be controlled by the ESM system26.

The battery pack20may include one or more additional components not illustrated inFIG.5(or elsewhere herein). For example, the battery pack20may include a high voltage interlock loop (HVIL), which may be configured to protect people from electrical power stored in the battery pack20during maintenance, assembly, etc. In some embodiments, the BMS30may activate or deactivate the HVIL, such as when the bus10is in a maintenance facility. In some embodiments, an activate signal for enabling the DC/DC pre-charger58via the software layer communication lines68and/or the hardware layer communication line70may be part of the enabling signal for the HVIL. For example, when the DC/DC pre-charger58is activated to import power to or export power from a battery pack20, DC terminal pins for the bus10may be deactivated for safety.

In this way, control by the BMS30may facilitate independent operation of the battery pack20, regardless of application. For example, communications with components outside of the battery pack20may be reduced as the battery pack20may just have to be instructed to start pre-charging or discharging operations.

FIG.6is a schematic illustration of a second configuration of a battery pack20of the battery system14ofFIG.2that includes a DC/DC pre-charger58, according to the present disclosure. The battery pack20illustrated inFIG.6may include some of the same components as the battery pack20illustrated inFIG.5. For example, the second configuration may include battery pack contactors72that can be opened or closed by the DC/DC pre-charger58(or the BMS30) depending on whether the DC/DC pre-charger58is to discharge or pre-charge the HV bus bar50. However, rather than being connected to the BMS30via the software layer communication lines68, the DC/DC pre-charger58ofFIG.6may be connected directly to the ESM system26(not illustrated inFIG.6) via the software layer communication lines68. Thus, in some embodiments, the ESM system26, rather than the BMS30, may directly control certain operations of the DC/DC pre-charger58. For example, the ESM system26may set whether the DC/DC pre-charger58is operating in a charging mode (e.g., where the DC/DC pre-charger58is pre-charging the HV bus bar50) or a discharging mode (e.g., where the DC/DC pre-charger58is discharging the HV bus bar50), may set or modify voltage limits or targets for the DC/DC pre-charger58, may power on or power off the DC/DC pre-charger58, and/or the like.

Although the DC/DC pre-charger58may be connected to the ESM system26, rather than the BMS30, via the software layer communication lines68in the example ofFIG.6, the DC/DC pre-charger58may be connected to the BMS30via the hardware layer communication line70. With this configuration, the BMS30may provide enabling/disabling signaling to the DC/DC pre-charger58via the hardware layer communication line70(e.g., to power the DC/DC pre-charger58on or off) and the ESM system26may provide signaling for voltage targets or limits, direction of operation (e.g., discharge or pre-charge), and/or the like. In this way, certain embodiments may provide for localized powering on or off of a DC/DC pre-charger58, which may reduce latency in powering on or off, while a centralized ESM system26may coordinate parameters for operation across multiple DC/DC pre-chargers58.

In some embodiments, a positive electrical terminal62and a negative electrical terminal66may be included in the DC/DC pre-charger58and may be controlled in conjunction with the DC/DC pre-charger58. For example, the positive electrical terminal62and the negative electrical terminal66may be controlled by the same enabling/disabling signals as the DC/DC pre-charger58and/or may be controlled directly by the DC/DC pre-charger58based on signaling received from the ESM system26. Although the schematics ofFIGS.5and6have been described separately, the schematics may be combined in some embodiments. For example, the battery pack20ofFIG.5may be modified in some embodiments such that the DC/DC pre-charger58is directly connected to the ESM system26, as in the schematic ofFIG.6.

In this way, control by the ESM system26may facilitate efficient external and centralized control of pre-charging or discharging operations. For example, the ESM system26may facilitate optimized control of multiple DC/DC pre-chargers58. Additionally, or alternatively, use of a centralized ESM system26may facilitate better fault handling through direct communications with components across multiple battery packs20.

FIG.7is a schematic illustration of a third configuration of a battery pack of the battery system ofFIG.2that includes a DC/DC pre-charger, according to the present disclosure. The battery pack20illustrated inFIG.7may include some of the same components as the battery pack20illustrated inFIG.6. However, rather than being electrically connected to electrical connections60,64between the battery pack contactors72and the electrical terminals62,66to the high voltage bus bar50, the DC/DC pre-charger58ofFIG.7may be electrically connected directly to dedicated electrical terminals62,66at an interface between the battery pack20and other components external to the battery pack20. Thus, in some embodiments, the DC/DC pre-charger58may have a dedicated external pre-charge output (shown inFIG.7as “EXTERNAL PRE-CHARGE OUTPUT”) from or input to the battery pack20(rather than sharing electrical terminals with the battery module34).

Although the schematics ofFIGS.5,6, and7have been described separately, the schematics may be combined in some embodiments. For example, the battery pack20ofFIG.5may be modified in some embodiments such that the DC/DC pre-charger58is electrically connected to components external to the battery pack20via dedicated terminals62,66, as in the schematic ofFIG.7.

In this way, the external pre-charge output may facilitate using a single battery pack20to pre-charge or discharge a string of battery packs20, rather than using multiple battery packs20working in tandem.

FIG.8is a schematic illustration of a junction box73that includes a DC/DC pre-charger58, according to the present disclosure. As illustrated inFIG.8, the junction box73may include the pre-charger58where various output terminals62,66(collectively identified by reference number74) of the DC/DC pre-charger58are electrically connected to electrical connections60,64between various contactors78(illustrated as shaded circles) and various HV outputs (“HV OUT 1,” “HV OUT 2,” and “HV OUT 3”) of the junction box73. As further illustrated inFIG.8, inputs terminals62,66(collectively identified by reference number76) of the DC/DC pre-charger58may be electrically connected to electrical connections60,64between the various contactors78and electrical terminals62,66to the high voltage bus bar50. In some embodiments, the contactors78may be separate components from the battery pack20. For example, certain implementations may include separate battery pack contactors72and contactors78to control connection to a bus bar.

In this configuration, each individual output from the junction box73may be individually powered. For example, one or more of the HV outputs (e.g., HV OUT 1, HV OUT 2, and HV OUT 3) may be closed while one or more other HV outputs are opened for pre-charging or discharging. Additionally, or alternatively, one or more parameters (e.g., voltage targets, voltage limits, etc.) for pre-charging or discharging may be applied to each HV output separately. For example, the DC/DC pre-charger58may apply different one or more parameters to different HV outputs. Additionally, or alternatively, if there is a high voltage event or non-catastrophic equipment failure on a high voltage out circuit, the circuit may be opened and discharged without disabling the entire high voltage system. Certain embodiments may selectively power on portions of the high voltage system without bringing the entire high voltage system online. For example, if a battery thermal management system (BTMS) is needed while the bus10is charging, certain embodiments may just power on the BTMS without powering on other elements of the high voltage system, such as an air compressor, a drivetrain, or an HVAC system.

FIG.9is a schematic illustration of a string of battery packs20of the battery system14ofFIG.2, according to the present disclosure. For example,FIG.9illustrates a string of two battery packs20(battery packs20-1and20-2) electrically connected to each other in series. While only two battery packs20are depicted in the string ofFIG.9, it is contemplated that a greater number of battery packs20can be included in a string, as needed or required. AlthoughFIG.9illustrates battery packs20that are each configured in a manner similar to that illustrated inFIG.7, battery packs20with other configurations according to the disclosure herein may be electrically connected in a string of battery packs20. In some embodiments, two or more strings of battery packs20may be electrically connected in parallel.

As further illustrated inFIG.9, certain electrical terminals62,66of the battery pack20-1may be electrically connected to a DC bus bar77. This configuration may utilize a wide output voltage range to pre-charge the bus bar77via an external connection, which may reduce or eliminate the need to rely on two or more DC/DC pre-chargers58operating in tandem with each other, thereby making the process of pre-charging more efficient. In addition, this configuration may increase a redundancy of certain systems of the bus10. For example, this may increase redundancy in a system with a single string of two battery packs20in parallel, where the DC/DC pre-chargers58may operate in tandem, by reducing or eliminating a failure of one pre-charger58causing a failure of the entire string. Continuing with the previous example, a bus bar may still be pre-charged despite a failed pre-charger58in this example.

FIG.10is another schematic illustration of a string of battery packs20of the battery system14ofFIG.2, according to the present disclosure. For example,FIG.10illustrates a string of two battery packs20(battery packs20-1and20-2) electrically connected to each other in series. AlthoughFIG.10illustrates battery packs20configured in a manner similar to that illustrated inFIG.6, battery packs20with other configurations according to the disclosure herein may be electrically connected in a string of battery packs20. As described herein for other strings of battery packs20, multiple strings of battery packs20may be electrically connected in parallel. In some embodiments, different configurations of battery packs20may be included in the same string of battery packs20and/or in different strings of battery packs20.

As used herein, “Vess” is an acronym for voltage-energy storage system. In the example illustrated inFIG.10, each high voltage battery pack20may contribute half of the overall string voltage (illustrated as “1/2 Vess”). As such, the DC/DC pre-chargers58in each battery pack20may pre-charge approximately half of the total string voltage or may discharge approximately half of the voltage from the HV bus bar50.

FIG.11illustrates an exemplary method100of controlling pre-charge operations of a DC/DC pre-charger58using a BMS30, according to the present disclosure. Although the method100is described as being performed by the BMS30, in some embodiments the ESM system26and/or one or more controllers associated with the battery system14may perform the method100(or portions of the method100). In some implementations, a combination of the ESM system26, the BMS30, and/or the one or more controllers may perform the method100. For example, the ESM system26may perform the operations illustrated at102and the BMS30may perform the operations illustrated at104and106.

The method100may include, at operation102, receiving a signal to control the DC/DC pre-charger58. For example, the BMS30may receive the signal from the ESM system26after the engine of a bus10is started and the ESM system26boots up. The signal may include an instruction for the BMS30to enable the DC/DC pre-charger58(e.g., to power on the DC/DC pre-charger58), may provide one or more parameters to the DC/DC pre-charger58, and/or the like. A parameter may include an output power limit, a maximum current limit, an indication of whether the DC/DC pre-charger58is to pre-charge the HV bus bar50or discharge the HV bus bar50, a target voltage for the HV bus bar50or the DC/DC pre-charger58, a time limit parameter for certain operations (e.g., a timeout fault after a certain amount of time), and/or the like. In some embodiments, various sets of parameters may be applied to a DC/DC pre-charger58. For example, a first set of parameters may be applied to the DC/DC pre-charger58to allow for a faster pre-charge or discharge than a second set of parameters for certain scenarios.

As illustrated at104, the method100may further include controlling a battery pack contactor72and/or the DC/DC pre-charger58. For example, the BMS30may send an instruction to the DC/DC pre-charger58to operate according to the one or more parameters (e.g., the instruction may cause the DC/DC pre-charger58to ramp voltage on the HV bus bar50to a target voltage, may cause the DC/DC pre-charger58to start to discharge the HV bus bar50, and/or the like). Additionally, or alternatively, the BMS30may cause one or more battery pack contactors72to open or close depending on whether the DC/DC pre-charger58is to discharge or pre-charge the HV bus bar50. Additionally, or alternatively, the BMS30may configure the DC/DC pre-charger58to provide data related to the operation of the DC/DC pre-charger58to the ESM system26and/or the BMS30. For example, the BMS30may configure the DC/DC pre-charger58to provide certain statistics related to the operation and/or the manner in which the DC/DC pre-charger58is to provide the statistics (e.g., in a stream of data, according to a schedule, etc.).

The method100may further include, at106, receiving and/or reporting data associated with the operation of the DC/DC pre-charger58. For example, the DC/DC pre-charger58may provide the data to the BMS30via the software communication lines68, and the BMS30may store the data in memory and/or may provide the data to the ESM26. In some embodiments, the BMS30may process the data prior to, or in connection with, receiving and/or reporting the data. For example, the BMS30may aggregate the data for a time period, may filter the data for outlier data points, may generate warnings or other alarms based on the data, and/or the like. This may reduce an amount of data that the BMS30has to record and/or report, may facilitate more efficient aggregation of data from multiple BMSs30by the ESM system26, and/or the like, thereby conserving computing resources of the battery system14.

The data may include an output voltage from the DC/DC pre-charger58, a pre-charging runtime, an estimated completion time for discharging or pre-charging, a DC bus bar capacitance (calculated or estimated), faults detected during the pre-charging or discharging, and/or the like. The DC/DC pre-charger58may monitor the data during operation.

FIG.12illustrates an exemplary method200of controlling pre-charge operations of a DC/DC pre-charger58using an ESM system26, according to the present disclosure. Although the method200is described as being performed by the ESM system26, in some embodiments the BMS30and/or one or more controllers associated with the battery system14may perform the method200(or portions of the method200). In some implementations, a combination of the ESM system26, the BMS30, and/or the one or more controllers may perform the method200. For example, the ESM system26may perform the operations illustrated at202and204, the BMS30may perform the operations illustrated at206, and a controller may perform the operations illustrated at208.

As illustrated at202, the method200may include sampling a voltage on a DC bus bar77. For example, the ESM system26may provide an instruction to the DC/DC pre-charger58to provide voltage samples to the ESM26and/or the ESM system26may sample the voltage directly from the DC bus bar77. The voltage may be sampled using a sensor, a voltage probe, and/or the like.

The method200may further include, at204, determining and/or transmitting parameters for a DC/DC pre-charger58. For example, the ESM system26may determine the parameters when the ESM system26boots up, based on whether the DC/DC pre-charger50is to discharge or pre-charge the DC bus bar77, and/or the like. The ESM system26may transmit the parameters to the DC/DC pre-charger58via the software communication lines68. Additionally, or alternatively, the ESM system26may transmit the parameters upon booting up, at a scheduled time for pre-charging or discharging, and/or the like.

As illustrated at206, the method200may include receiving data related to an operation of the DC/DC pre-charger58. For example, the ESM system26may receive the data from the DC/DC pre-charger58via the software communication lines68. The ESM system26may receive the data in a manner similar to that described above in connection with step106of the method100ofFIG.11. Additionally, or alternatively, the ESM system26may store the data in memory after receiving the data and/or may provide the data to a system external to the bus10, such as when the bus10is connected to an external diagnostic system. Additionally, or alternatively, the ESM system26may process the data after receiving the data. For example, the ESM system26may filter the data, identify faults in operation of the DC/Dc pre-charger58, aggregate the data with data from one or more other DC/DC pre-chargers58, aggregate the data with historical data for the DC/DC pre-charger58and/or the like.

When the voltage reaches a target voltage, the method200may include, at208, closing one or more battery contactors72. For example, the ESM26may close the battery pack contactors72such that current flows from a battery module34to the HV bus bar50. In some embodiments, the ESM system26may provide an instruction to the DC/DC pre-charger58to close the battery pack contactors72. In some embodiments, the ESM system26may configure the DC/DC pre-charger58to close the battery pack contactors72when the target voltage is reached.

FIG.13illustrates an exemplary method300of controlling discharge operations of a DC/DC pre-charger58using an ESM system26, according to the present disclosure. Although the method300is described as being performed by the ESM system26, in some embodiments the BMS30and/or one or more controllers associated with the battery system14may perform the method300(or portions of the method300). In some implementations, a combination of the ESM system26, the BMS30, and/or the one or more controllers may perform the method300. For example, the ESM system26may perform the operations illustrated at302, the BMS30may perform the operations illustrated at304, and a controller may perform the operations illustrated at306.

As illustrated at302, the method300may include determining that an active DC bus bar77has to be discharged. For example, the ESM system26may determine that the DC bus bar77has to be discharged when an engine of the bus10is powered off. At the start of the method300, the battery pack contactors72may be in an open state.

As illustrated at304, the method300may include determining and/or transmitting parameters for operation of a DC/DC pre-charger58in a discharge mode. For example, the ESM system26may determine and/or transmit parameters in a manner similar to that described above in connection with the operation at204of the method200ofFIG.12. A parameter for discharge operations may be similar to the parameters described elsewhere herein or may include other parameters specific for discharging, such as a safe threshold voltage as a secondary target (e.g., a fast discharge may be used for the system voltage down to 50V, but then a slower discharge may be used for voltages lower than 50V).

The discharge mode may include a mode of operation of the DC/DC pre-charger58where the DC/DC pre-charger58discharges energy from the HV bus bar50. As illustrated at306, the method300may include stopping operation of the DC/DC pre-charger58in the discharger mode. For example, when the HV bus bar50is discharged (or discharged below a certain level), the ESM system26may transmit an instruction to the DC/DC pre-charger58to stop the operation. Additionally, or alternatively, the ESM system26may configure the DC/DC pre-charger58to stop the operation automatically when the HV bus bar50is discharged.

FIG.14illustrates example components of a computing device400, according to the present disclosure. In particular,FIG.14is a simplified functional block diagram of a computing device400that may be configured as a device for executing methods of this disclosure, such asFIGS.11,12, and13. For example, the computing device may be configured as the ESM system26, the BMS30, a battery pack controller, the high voltage peripheral device or system52, the low voltage peripheral device or system56, and/or another device or system according to exemplary embodiments of the present disclosure. In various embodiments, any of the devices or systems described herein may be the computing device400illustrated inFIG.14and/or may include one or more of the computing devices400.

As illustrated inFIG.14, the computing device400may include a processor402, a memory404, an output component406, a communication bus408, an input component410, and a communication interface412. The processor402may include a central processing unit (CPU), a graphics processing unit (GPU), an accelerated processing unit (APU), a microprocessor, a microcontroller, a digital signal processor (DSP), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or another type of processing component. In some embodiments, the processor402includes one or more processors capable of being programmed to perform a function. The memory404may include a random access memory (RAM), a read only memory (ROM), and/or another type of dynamic or static storage device (e.g., a flash memory, a magnetic memory, and/or an optical memory) that stores information and/or instructions for use by the processor402.

The output component406may include a component that provides output information from the computing device400(e.g., a display, a speaker, and/or one or more light-emitting diodes (LEDs)). The communication bus408may include a component that permits communication among the components of the computing device400. The input component410may include a component that permits the computing device400to receive information, such as via user input (e.g., a touch screen display, a keyboard, a keypad, a mouse, a button, a switch, and/or a microphone). Additionally, or alternatively, the input component410may include a sensor for sensing information (e.g., a global positioning system (GPS) component, an accelerometer, a gyroscope, and/or an actuator). The communication interface412may include a transceiver-like component (e.g., a transceiver and/or a separate receiver and transmitter) that activates device400to communicate with other devices, such as via a wired connection, a wireless connection, or a combination of wired and wireless connections. The communication interface412may permit the computing device400to receive information from another device and/or provide information to another device. For example, the communication interface412may include a controller area network (CAN) bus, an Ethernet interface, an optical interface, a coaxial interface, an infrared interface, a radio frequency (RF) interface, a universal serial bus (USB) interface, a wireless local area network interface, a cellular network interface, and/or the like.

As noted above, the computing device400illustrated inFIG.14may perform one or more processes described herein. The computing device400may perform these processes based on the processor402executing software instructions stored by a non-transitory computer-readable medium, such as the memory404and/or another storage component. For example, the storage component may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, and/or a solid state disk), a compact disc (CD), a digital versatile disc (DVD), a floppy disk, a cartridge, a magnetic tape, and/or another type of non-transitory computer-readable medium, along with a corresponding drive. A computer-readable medium is defined herein as a non-transitory memory device. A memory device includes memory space within a single physical storage device or memory space spread across multiple physical storage devices.

Software instructions may be read into the memory404and/or a storage component from another computer-readable medium or from another device via the communication interface412. When executed, software instructions stored in the memory404and/or the storage component may cause the processor402to perform one or more processes described herein. Additionally, or alternatively, hardwired circuitry may be used in place of or in combination with software instructions to perform one or more processes described herein. Thus, embodiments described herein are not limited to any specific combination of hardware circuitry and software.

Certain embodiments described herein may provide various technological advantages or improvements. For instance, certain embodiments described herein may facilitate safe closure of battery pack contactors without a significant inrush of current into a battery pack, which may reduce or eliminate damage to components of an electric vehicle that might otherwise occur due to an inrush of current. Additionally, or alternatively, by utilizing a DC/DC pre-charger in each battery pack of a battery system, certain embodiments may still provide for failover of pre-charging or discharging of a HV bus bar50from one DC/DC pre-charger to another, which may improve safety and reduce damage to electrical components in the event of a failure of a battery pack. Additionally, or alternatively, certain embodiments may provide a safety mechanism to discharge a HV bus bar in an accelerated but controlled manner (e.g., in the case of a failure of an HV device's internal discharge circuit). In this scenario, one or more DC/DC pre-chargers may be used to reduce the voltage on the HV bus bar to an acceptable and safe level. This may also be used if a more rapid than normal reduction in the DC voltage is needed, such as in the event of an emergency. Additionally, or alternatively, certain embodiments may facilitate faster identification of faults in pre-charging or discharging, such as through in-battery pack monitoring.

Additionally, or alternatively, certain embodiments described above include the BMS30and/or the ESM system26controlling the pre-charging or discharging. Having the BMS30control certain operations may facilitate operation of the battery pack20in a standalone manner. For example, each battery pack20may be controlled independently from other battery packs20, which may simplify control by reducing or eliminating the need for battery packs20to be in communication with a central controller. Having the ESM system26control certain operations may facilitate better coordination of operations among multiple battery packs20(e.g., for tandem operations, reading faults or statuses, setting limits, etc.).

Additionally, or alternatively, certain embodiments may provide for selective enabling of high voltage circuits, either for partial operation, low power operation of certain components, or for recovery in the event of a non-powertrain failure. Additionally, or alternatively, certain control aspects described herein may provide for improved management of a battery system14compared to passive pre-charging circuits.

While principles of the present disclosure are described herein with reference to a battery pack that includes a DC/DC pre-charger for electric buses, it should be understood that the disclosure is not limited thereto. Rather, the systems and methods described herein may be employed in any type of electric vehicle. Also, those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, embodiments, and substitution of equivalents all fall within the scope of the embodiments described herein. Accordingly, the invention is not to be considered as limited by the foregoing description. For example, while certain features have been described in connection with various embodiments, it is to be understood that any feature described in conjunction with any embodiment disclosed herein may be used with any other embodiment disclosed herein.