MULTI-VOLTAGE VEHICLE OPERATION

Abstract

A vehicle contains two or more battery packs configured to power a motor. A controller is configured to dynamically activate an operating mode during operation. The operating mode is one of several possible modes, including a first operating mode, which defines a series connection between the two or more battery packs, and a second operating mode, which defines a parallel connection between the two or more battery packs. The connection between the battery packs is controlled by several first switches. Several low-voltage loads are connected to a subset of the battery packs of the two or more battery packs such that a power output of the subset of battery packs provides full power to the several low-voltage loads. The several low-voltage loads are connected only to the subset of battery packs in both the first and second operating modes.

Description

INTRODUCTION

[0001] The subject matter of the disclosure relates to a multi-voltage vehicle operation.

[0002] An electric vehicle or a hybrid vehicle (e.g., a car, a truck, a piece of construction equipment, an agricultural implement, an automated factory facility) may contain two or more battery packs that provide power to the vehicle's propulsion. Typically, these packs are connected in parallel for vehicle operation. That is, the two or more battery packs are connected in parallel to supply the power inverter module (PIM) of each motor. For example, a vehicle may contain one or more front and rear motors. In some scenarios, the vehicle may benefit from more power. Therefore, it is desirable to provide multi-voltage vehicle operation. SUMMARY

[0003] According to an exemplary embodiment, a system in a vehicle includes two or more battery packs configured to supply power to one or more motors of the vehicle to move the vehicle; a controller configured to dynamically activate an operating mode of a multi-level voltage system of the vehicle during vehicle operation, wherein the operating mode is one of a plurality of possible operating modes, the plurality of possible operating modes comprising a first operating mode defining a series connection between the two or more battery packs and a second operating mode defining a parallel connection between the two or more battery packs, and the connection between the two or more battery packs is controlled by a plurality of first switches;a plurality of low-voltage loads connected to a subset of the battery packs of the two or more battery packs such that a power output of the subset of the battery packs of the two or more battery packs provides power to the plurality of low-voltage loads, wherein the plurality of low-voltage loads are connected only to the subset of the battery packs of both the first operating mode and the second operating mode;

[0004] In any of the examples described above, a high-voltage terminal of the subset of low-voltage loads is connected to a high-voltage terminal of the subset of batteries regardless of the modes of the plurality of first switches, and a low-voltage terminal of the subset of batteries is connected to a low-voltage terminal of the multi-level voltage system.

[0005] In any of the examples described above, a connection between the high-voltage terminal of the low-voltage load subset and the high-voltage terminal of the battery subset is a direct, non-switched connection.

[0006] In any of the examples described above, a low-voltage terminal of the subset of low-voltage loads is connected to a low-voltage terminal of the subset of batteries regardless of the states of the plurality of first switches, and a high-voltage terminal of the subset of batteries is connected to a high-voltage terminal of the multi-level voltage system.

[0007] In any of the examples described above, the connection between the low-voltage terminal of the low-voltage load subgroup and the low-voltage terminal of the battery subgroup is a direct, unswitched connection.

[0008] Any of the examples described above further includes a configurable low-voltage load connection including a first interconnect line connecting a high-voltage terminal of the subset of low-voltage loads to a high-voltage terminal of a first subset of batteries of the two or more battery packs, a second interconnect line connecting a high-voltage terminal of the subset of low-voltage loads to a high-voltage terminal of a second subset of batteries of the two or more battery packs, a third interconnect line connecting a low-voltage terminal of the low-voltage loads to a low-voltage terminal of the first subset of batteries of the two or more battery packs, and a fourth interconnect line connecting the low-voltage terminal of the low-voltage loads to a low-voltage terminal of the second subset of batteries of the two or more battery packs.

[0009] In any of the examples described above, the first interconnection line includes a first configurable low-voltage load switch, the second interconnection line includes a second configurable low-voltage load switch, the third interconnection line includes a third configurable low-voltage load switch, and the fourth interconnection line includes a fourth low-voltage load switch.

[0010] In any of the examples described above, the subset of low-voltage loads is connected to the first subset of batteries of the two or more battery packs while the first and third configurable low-voltage load switches are closed and the second and fourth configurable low-voltage load switches are open.

[0011] In any of the examples described above, the subset of low-voltage loads is connected to the second subset of batteries of the two or more battery packs while the second and fourth configurable low-voltage load switches are closed and the first and third configurable low-voltage load switches are open.

[0012] Any of the examples described above further includes a controller configured to control a state of the first, second, third, and fourth configurable low-voltage load switches, wherein the controller is further configured to change a state of the first, second, third, and fourth configurable low-voltage load switches, thereby changing which subset of the batteries of the two or more battery packs is connected to the low-voltage loads.

[0013] In any of the examples described above, the controller is configured to change the state of the first, second, third, and fourth configurable low-voltage load switches in response to a state of charge of the first subset of batteries of the two or more battery packs and the second subset of batteries of the two or more battery packs.

[0014] In any of the examples described above, each battery of the two or more battery packs is included in exactly one of the first subset of batteries or the second subset of batteries of the two or more battery packs.

[0015] According to another exemplary embodiment, a method of arranging a system in a vehicle includes arranging two or more battery packs to power one or more motors of the vehicle to move the vehicle, configuring a controller to dynamically activate an operating mode of a multi-level voltage system of the vehicle during vehicle operation, the operating mode being one of a plurality of possible operating modes, the plurality of possible operating modes including a first operating mode defining a series connection between the two or more battery packs and a second operating mode defining a parallel connection between the two or more battery packs, and arranging a group of low-voltage loads to receive power from a subset of the two or more battery packs regardless of which operating mode is activated.

[0016] In any of the examples described above, arranging the group of low-voltage loads to receive power from the subgroup of two or more battery packs regardless of the operating mode that is enabled includes connecting a high-voltage terminal of the subgroup of low-voltage loads to a high-voltage terminal of the subgroup of batteries regardless of the modes of the plurality of first switches, and connecting a low-voltage terminal of the subgroup of batteries to a low-voltage terminal of the multi-level voltage system.

[0017] In any of the examples described above, a connection between the high-voltage terminal of the low-voltage load subset and the high-voltage terminal of the battery subset is a direct, non-switched connection.

[0018] In any of the examples described above, the two or more battery packs include a plurality of mutually exclusive subsets, wherein the controller is configured to change which mutually exclusive subset is connected to the low voltage loads using a configurable connection and in response to at least one detected condition.

[0019] In any of the examples described above, the configurable connection comprises a configurable low-voltage load connection comprising a first connection line connecting a high-voltage terminal of the subset of low-voltage loads to a high-voltage terminal of a first subset of batteries of the two or more battery packs, a second connection line connecting a high-voltage terminal of the subset of low-voltage loads to a high-voltage terminal of a second subset of batteries of the two or more battery packs, a third connection line connecting a low-voltage terminal of the low-voltage loads to a low-voltage terminal of the first subset of batteries of the two or more battery packs, and a fourth connection line,which connects the low-voltage terminal of the low-voltage loads to a low-voltage terminal of the second subgroup of batteries of the two or more battery packs.

[0020] In any of the examples described above, at least one detected condition is an unbalanced state of charge of the two or more battery packs or an initiation of a charging operation of the two or more battery packs.

[0021] In any of the examples described above, the detected condition is an unbalanced state of charge, wherein the configurable connection is changed so that the low voltage loads are connected to a most highly charged subset of the subset of batteries.

[0022] In any of the examples described above, the detected condition is an initiation of a charging operation, wherein the configurable connection is changed such that the low voltage loads are connected to a first subset of the subset of batteries while a second subset of the subset of batteries is being charged, and to a second subset of the subset of batteries while the first subset of batteries is being charged.

[0023] The above-described features and advantages and other features and advantages of the disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further features, advantages and details appear only as examples in the following detailed description, which refers to the drawings; they show: Fig. 1 is a block diagram of a vehicle having a multi-voltage drive system according to one or more embodiments; Fig. 2 a block diagram of the vehicle of Fig. 1, including a low-voltage connection to a subset of the supply loads, according to another embodiment; Fig. 3 a block diagram of the vehicle of Fig. 1, including a low-voltage connection to a subset of the supply loads, according to yet another embodiment; and Fig. 4 a block diagram of the vehicle of Fig. 1, including a switched low-voltage connection to a subset of the supply loads, according to yet another embodiment. DETAILED DESCRIPTION

[0025] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference characters indicate similar or corresponding portions and features.

[0026] The embodiments of the systems and methods described herein relate to multi-voltage vehicle operation. An electric vehicle or a hybrid vehicle may include two or more battery packs. A battery pack refers to multiple batteries or battery cells managed by a battery management system (BMS). The battery pack and associated BMS may collectively be referred to as a smart battery pack. The battery packs are typically connected in parallel during vehicle operation. This allows, for example, two 400-volt (V) battery packs to be connected in parallel to supply 400 V to each PIM of each motor of the vehicle and also to various loads (e.g., the integrated power electronics, the air conditioning system).

[0027] Example embodiments include changing a connection to the two or more battery packs to allow some loads to receive high voltage from the battery packs connected in series with one or more PIMs and one or more loads, while allowing other loads to receive low voltage from one of the battery packs, regardless of whether the battery packs are currently connected in parallel or in series. According to one or more embodiments, the battery packs may be dynamically connected in series to supply high voltage to the PIMs and one or more loads. According to another embodiment, the battery packs may be statically connected in series to supply high voltage to the PIMs and the one or more loads.This may be desirable for a higher power mode of operation, while paralleling the battery packs may be desirable for a higher efficiency mode of operation. Certain loads will always require low voltage for operation, but efficiency can be increased by allowing the low voltage loads to be constantly connected to a single battery pack of the two or more battery packs. For illustrative purposes, the multi-voltage output will be described using two battery packs. However, any number of battery packs may be used, with the static connections shown for a single battery pack. For example, three 400 V battery packs may be connected in series to supply 1200 V to a first group of loads, while a single 400 V battery pack is connected to the loads requiring a low voltage supply.

[0028] According to an exemplary embodiment, Fig. 1 is a block diagram of a vehicle 100 having a multi-voltage propulsion system 110. The example vehicle 100 is a motor vehicle 101. Two example battery packs 120-A and 120-B (generally referred to as 120) power a front motor 130-F, a left rear motor 130-LR, and a right rear motor 130-RR (generally referred to as motor 130). The battery packs 120 also power the loads 150. The battery packs 120 may be charged by a direct current fast charger (DCFC) 160 or by an on-board charging module (OBCM) 180 powered by the alternating current (AC) grid 170. Each of the battery packs 120-A and 120-B is shown with a corresponding BMS 125-A and 125-B (generally designated 125). According to alternative examples, both battery packs 120-A and 120-B are controlled by a single BMS 125.

[0029] The BMS 125 of each battery pack 120 or the single, shared BMS 125 may indicate the state of charge, temperature, voltage, current, and other parameters used to make decisions such as whether charging is required. These parameters may also indicate, according to embodiments that include such capability, when a change in the low-voltage load supply from a first battery pack 120-A to a second battery pack 120-B (or vice versa) is warranted. The drive system 110 includes, in addition to components not specifically explained here, the battery packs 120 and the motors 130 (shown in Fig. 1).

[0030] The vehicle 100 is shown with a controller 115. The controller 115 can, as described in detail herein, implement the dynamic change between the series and parallel connection of the battery packs 120. According to a practical example, the controller 115 is a software module and incorporated into the functionality of the BMS 125. According to alternative examples, the functionality of the controller 115 can be implemented in a dedicated controller, as a software system distributed across multiple vehicle controllers, or as any similar system. The various switches SA1, SA2, SA3, SB1, SB2, SB3, SA, and SB are controlled to facilitate the dynamic change between the series and parallel connection of the battery packs 120 and are described in the Fig. 1-4 are all shown in the open position, where the switches can be controlled by the controller 115 to close as indicated by the arrows. The implementation of the dynamic change between the series and parallel connection of the battery packs 120 due to a change in the operating mode of the vehicle 100 (e.g., between high power and high efficiency) has been previously disclosed and will not be discussed in detail here.

[0031] The controller 115 may include processing circuitry, which may include an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) with memory executing one or more software or firmware programs, combinational logic circuitry, and / or other suitable components that provide the described functionality. The memory of the controller 115 may include non-transitory computer-readable media storing instructions that, when processed by one or more of the processors of the controller 115, implement the dynamic change and also control of the switches to provide a direct low-voltage connection to the low-voltage loads 150 while simultaneously providing a high-voltage connection for the motors 130 and the on-board charging module 180.

[0032] When battery packs 120-A and 120-B are connected in series, switches SB2, SA, SB, and SA1 are closed, creating a high-voltage output for motors 130 and loads 150 and 180 by connecting a high-voltage terminal of first battery pack 120-A to a high-voltage terminal P2 of multi-level voltage system 110, a low-voltage terminal of first battery pack 120-A to the high-voltage terminal of second battery pack 120-B, and the low-voltage terminal of second battery pack 120-B to a low-voltage terminal P1 of multi-level voltage system 110. In some existing systems, any loads 150 that cannot accept the high voltage resulting from the series connection of the battery packs 120 can be supplied via a DC-DC converter that reduces the voltage of the battery packs 120 to a voltage that is accepted by the loads 150. In the examples of Fig. 2-4, the connections to a single battery pack allow the 150 loads requiring low voltage to be directly connected to a single 120 battery pack, and DC-DC converters can be omitted. Eliminating the DC-DC converters reduces vehicle weight and complexity.

[0033] When the connection between the battery packs 120 is dynamically changed, or when one or more battery packs 120 are first activated individually, in parallel, or in series (i.e., in a particular power mode), or when a given power mode is deactivated, the current imbalance between the battery packs 120 and the motors 130 or loads 150 may result in an inrush current in the motors 130 and loads 150. To limit the inrush current, the pre-charge contactors 140-A and 140-B and the pre-charge resistor 145 are first used in a specific sequence.

[0034] According to alternative examples of Fig. 1, one or more additional loads may require the same voltage as the motors 130 and be connected in parallel with the motors 130 similar to the low voltages 150. Also included in the multi-voltage drive system 110 are a set of positive high-voltage battery terminal fuses (pyroswitches) 210 and a plurality of voltage / current sensors 220. The pyroswitches 210 are positive high-voltage battery terminal fuses that destructively and irreversibly break the electrical connection to prevent short circuits, thereby preventing overcurrent and thermal runaway conditions. The voltage / current sensors 220 are conventional voltage and current sensors that provide feedback to any controller, including the OBCM 180 and / or the DCFC 16, for monitoring and adjusting the performance characteristics of the multi-voltage drive system 110.Communication with the voltage / current sensors 220 can be accomplished via any common communication protocol or connection.

[0035] With continued reference to Fig. 1 show the Fig. 2 and Fig. 3 illustrates an embodiment of the multi-voltage drive system 110 configured to provide low voltage power directly to the low voltage loads 150 while also providing high voltage power to the motors 130 and any other loads that may require high voltage power.

[0036] With special reference to Fig. 2, a high-voltage terminal 202 of each of the low-voltage loads 150 is directly connected to the positive terminal 201 of the second battery pack 120-B via a direct connection 155, and a negative / low-voltage terminal 204 of the low-voltage loads 150 and the OBCM 180 is connected to the negative / low-voltage terminal 203 of the second battery pack 120-B via the switch SB2 and the pyroswitch 210. This direct connection 155 allows each of the loads 150 and the OBCM 180 to receive power only from the second battery pack 120-B, regardless of whether the battery packs 120 are connected in series or in parallel.

[0037] With special reference to the design of the Fig. 3, the high-voltage terminals 202 of the low-voltage loads 150 and the OBCM 180 are directly connected via a direct connection 165 to a connection point P2 of the high-voltage terminal of the multi-level voltage system 110. A low-voltage terminal / 0-volt terminal 204 of each load 150 and of the OBCM 180 is connected through a pyroswitch 210 to the negative terminal 161 of the first battery pack 120-A. This direct connection 165 allows each of the loads 150 and the OBCM 180 to receive power only from the first battery pack 120-A, regardless of whether the battery packs 120 are connected in series or in parallel.

[0038] It is intended that the embodiments of the Fig. 2 and Fig. 3 can be combined so that a subset of the low-voltage loads 150 can be connected via the connection shown in Fig. 3, is connected to the first battery pack 120-A and a subset of the low voltage loads 150 via the Fig. 2 is connected to the second battery pack 120-B. According to such an example, the two embodiments of the Fig. 2 or 3 simultaneously incorporated into a single multi-voltage drive system.

[0039] According to some examples, the direct connection to the individual battery packs 120 of the Fig. 2 and Fig. 3 can be adapted to accommodate flexible connections by providing a switched connection from the high-voltage terminal 202 of the loads 150 and a switched connection from the low-voltage terminal 204 of the loads 150. The flexible connection is referred to as a configurable low-voltage load connection. Fig. Figure 4 shows one embodiment of the flexible connection with the high-voltage terminal 202 of each load 150 connected to the positive terminal 201 and 203 of each battery pack 120 via a corresponding switch 232-A and 232-B. The switches 232-A and 232-B may be combined into a single dual-mode switch. For example, the switches 232-A and 232-B may be electromechanical two-way switches or paired solid-state relays. Similarly, the low-voltage / 0-volt terminal 204 of each load 150 is connected to the negative terminal 205 and 207 of the corresponding battery pack 120-A and 120-B via a corresponding switch 234-A and 234-B. As with switches 232-A and 232-B, switches 234-A and 234-B can be combined into a single dual-mode switch. For example, switches 234-A and 234-B can be electromechanical two-way switches or paired solid-state relays.Each of the switches 232 and 234 is controlled by a switch controller, such as the OBCM 180, the DCFC 160, or any similar controller.

[0040] During operation, the low-voltage loads 150 can be connected to the first battery pack 120-A by closing the corresponding switches 232-A, 234-A and keeping switches 232-B and 234-B corresponding to the second battery pack 120-B open. Conversely, the low-voltage loads 150 can be connected to the second battery pack 120-B by closing the corresponding switches 232-B and 234-B and keeping switches 232-A and 234-A open. In series mode, the low-voltage loads 150 must switch between 120-A or 120-B to maintain a voltage / SOC balance in the battery packs. In parallel mode, the low-voltage loads 150 are connected in parallel to both battery packs, and the battery packs balance each other.

[0041] When the battery packs 120 are operated in the low power, high efficiency mode in which they are arranged in parallel with the motors 130, it is possible that the battery pack 120-A or 120-B to which the low voltage loads 150 are connected will be discharged more than the other battery pack 120-A or 120B. The flexible mode, which in the embodiment of the Fig. 4, connecting the loads 150 to the battery pack 120-A or 120-B having a higher state of charge allows a controller to actively balance the state of charge of each battery pack 120-A or 120B.

[0042] Furthermore, during some vehicle operations (e.g., during braking, cruising speed), charging power may become available from one or more other sources within the vehicle 110. During such modes, the DCFC 160 may charge the first battery pack 120-A while the low-voltage loads 150 and the motors 130 are connected to the second battery pack 120-B. Once the first battery pack 120-A is sufficiently charged, the connections are switched, the second battery pack 120-B is charged, and the motors 130 and the loads 150 are connected to the first battery pack 120-A. Once a sufficient charge is achieved, the battery packs 120-A and 120-B may be reconnected in series, and standard operation may resume.

[0043] The terms "a" and "an" do not imply a limitation of number, but rather denote the presence of at least one of the referenced elements. The term "or" means "and / or" unless clearly indicated otherwise by context. A reference throughout the application text to "an aspect" means that a particular element (e.g., a feature, structure, step, or property) described in connection with the aspect is included in at least one aspect described herein and may or may not be present in further aspects. In addition, it is to be understood that the described elements in the various aspects may be combined in any suitable manner.

[0044] When an element, such as a layer, film, region, or substrate, is referred to as "on" another element, it may be directly adjacent to the other element or may also have intervening elements present. In contrast, when an element is referred to as "directly adjacent" to another element, no intervening elements are present.

[0045] Unless otherwise specified herein, all examination standards shall be the most recent standard in force as of the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the examination standard appears.

[0046] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0047] While the above disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements without departing from the scope thereof. Additionally, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within its scope.

Claims

[1] System in a vehicle, comprising: two or more battery packs configured to power one or more motors of the vehicle to move the vehicle; a controller configured to dynamically activate an operating mode of a multi-level voltage system of the vehicle during vehicle operation, wherein the operating mode is one of a plurality of possible operating modes, wherein the plurality of possible operating modes include a first operating mode defining a series connection between the two or more battery packs and a second operating mode defining a parallel connection between the two or more battery packs, wherein the connection between the two or more battery packs is controlled by a plurality of first switches; a plurality of low-voltage loads connected to a subset of the battery packs of the two or more battery packs such that a power output of the subset of the battery packs of the two or more battery packs provides power to the plurality of low-voltage loads; and wherein the plurality of low-voltage loads are connected only to the subset of battery packs in both the first operating mode and the second operating mode. [2] The system of claim 1, wherein a high-voltage terminal of the subset of low-voltage loads is connected to a high-voltage terminal of the subset of batteries, regardless of the modes of the plurality of first switches, and a low-voltage terminal of the subset of batteries is connected to a low-voltage terminal of the multi-level voltage system, wherein a connection between the high-voltage terminal of the subset of low-voltage loads and the high-voltage terminal of the subset of batteries is selectively a direct, non-switched connection. [3] The system of claim 1, wherein a low voltage terminal of the subset of low voltage loads is connected to a low voltage terminal of the subset of batteries regardless of the states of the plurality of first switches, and a high voltage terminal of the subset of batteries is connected to a high voltage terminal of the multi-level voltage system, wherein the connection between the low voltage terminal of the subset of low voltage loads and the low voltage terminal of the subset of batteries is optionally a direct, non-switched connection. [4] The system of claim 1, further comprising a configurable low-voltage load connection including a first interconnection line connecting a high-voltage terminal of the subset of low-voltage loads to a high-voltage terminal of a first subset of batteries of the two or more battery packs, a second interconnection line connecting a high-voltage terminal of the subset of low-voltage loads to a high-voltage terminal of a second subset of batteries of the two or more battery packs, a third interconnection line connecting a low-voltage terminal of the low-voltage loads to a low-voltage terminal of the first subset of batteries of the two or more battery packs, and a fourth interconnection line connecting the low-voltage terminal of the low-voltage loads to a low-voltage terminal of the second subset of batteries of the two or more battery packs. [5] The system of claim 4, wherein the first interconnection line includes a first configurable low-voltage load switch, the second interconnection line includes a second configurable low-voltage load switch, the third interconnection line includes a third configurable low-voltage load switch, and the fourth interconnection line includes a fourth low-voltage load switch. [6] The system of claim 5, wherein the subset of low-voltage loads is connected to the first subset of batteries of the two or more battery packs while the first and third configurable low-voltage load switches are closed and the second and fourth configurable low-voltage load switches are open. [7] The system of claim 6, wherein the subset of low-voltage loads is connected to the second subset of batteries of the two or more battery packs while the second and fourth configurable low-voltage load switches are closed and the first and third configurable low-voltage load switches are open. [8] The system of claim 5, further comprising a controller configured to control a state of the first, second, third, and fourth configurable low-voltage load switches, wherein the controller is further configured to change a state of the first, second, third, and fourth configurable low-voltage load switches, thereby changing which subset of the batteries of the two or more battery packs is connected to the low-voltage loads, and wherein the controller is selectively configured to change the state of the first, second, third, and fourth configurable low-voltage load switches in response to a state of charge of the first subset of the batteries of the two or more battery packs and the second subset of the batteries of the two or more battery packs. [9] A method for creating a system in a vehicle, the method comprising: Arranging two or more battery packs to power one or more motors of the vehicle to move the vehicle; Configuring a controller to dynamically activate an operating mode of a multi-level voltage system of the vehicle during vehicle operation, wherein the operating mode is one of a plurality of possible operating modes, the plurality of possible operating modes comprising a first operating mode defining a series connection between the two or more battery packs and a second operating mode defining a parallel connection between the two or more battery packs; and Arranging a group of low-voltage loads to receive power from a subset of the two or more battery packs, regardless of which operating mode is enabled. [10] The method of claim 9, wherein the system is one of the systems of claims 1-8.

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