Scalable battery system and method

Abstract

Various control systems and methods are discussed, including a method of controlling a battery pack, the method optionally including: providing a plurality of battery strings each having the same configuration, each battery string including a plurality of battery cells connected in series, wherein each of the plurality of battery strings is connected to a respective pair of contactors; providing a sensor configured to measure at least one of a voltage and a current of each of the plurality of battery strings, where the respective sensor is electrically connected to the electronic controller; and selectively and individually controlling, with an electronic controller, a battery string of the plurality of battery strings to satisfy a requirement based on a measurement result from each sensor.

Description

Technical Field

[0001] This document relates to rechargeable battery technology, and in particular to technology for powering large mobile machinery using one or more identically constructed battery packs and battery strings. Background Technology

[0002] Powering large mobile machinery (such as industrial equipment like earthmoving machines) with electric motors requires a large mobile electrical energy source capable of delivering tens to hundreds of amperes (Amp). Multiple high-capacity battery cells connected in parallel as a battery string can provide the continuous energy power required by large electric mobile machinery. However, when multiple battery strings are connected in parallel, a complex system is formed, which must be carefully controlled for safety, reliability, and performance. For example, in a typical battery architecture, it is necessary to avoid connecting battery cells with excessively different states of charge. If this cannot be avoided, high currents will be generated, and potential damage to the batteries may occur as the charges of the multiple battery cells attempt to equalize across the battery string. Summary of the Invention

[0003] According to one example, a control system for a battery pack is disclosed, which optionally includes a plurality of battery strings, a plurality of contactors, a plurality of sensors, and an electronic controller, each of the plurality of battery strings having the same configuration. Each battery string includes a plurality of battery cells connected in series. The plurality of contactors each optionally have the same configuration. Each battery string has a corresponding pair of contactors from the plurality of contactors, one of the contactors in the corresponding pair being connected to the positive terminal of each battery string, and the second contactor in the corresponding pair being connected to the negative terminal of each battery string. Each of the plurality of battery strings has a corresponding sensor from the plurality of sensors, the corresponding sensor being configured to measure at least one of voltage and current. The electronic controller is connected to the plurality of sensors and the plurality of contactors. The electronic controller is configured to individually control each of the plurality of battery strings to meet system requirements based on the measurement results from the plurality of sensors.

[0004] According to another example, a method for controlling a battery pack is disclosed, the method optionally including: providing a plurality of battery strings, each having the same configuration, each battery string including a plurality of battery cells connected in series, wherein each of the plurality of battery strings is connected to a corresponding pair of contactors; providing a sensor configured to measure at least one of voltage and current of each of the plurality of battery strings, wherein each corresponding sensor is electrically connected to an electronic controller; and selectively controlling the battery strings of the plurality of battery strings individually using the electronic controller based on the measurement results from each sensor to meet a requirement.

[0005] According to another example, a method for flexibly expanding a battery system is disclosed. The method optionally includes: providing a reference battery pack comprising a plurality of battery strings, each of the plurality of battery strings having the same configuration; controlling each of the plurality of battery strings using an electronic controller to meet requirements; adding one or more additional battery strings having the same configuration to the reference battery pack to increase power output; wherein the same configuration includes the same architecture and the same components for each of the plurality of battery strings, including the one or more additional battery strings, thereby enabling the interchangeable addition of battery strings without reconfiguration of the electronic controller. Attached Figure Description

[0006] Figure 1 This is an elevation view depicting an exemplary operating machine according to this disclosure.

[0007] Figure 2 This is a schematic diagram of a modular battery system for operating machinery, according to an example of this application.

[0008] Figure 3 This is a schematic diagram of multiple battery strings in a battery pack according to an example of this application.

[0009] Figure 4 This is a schematic diagram of a battery string according to another example of this application.

[0010] Figure 5 This is an example of an extended battery pack method based on the present application. Detailed Implementation

[0011] Examples of this application relate to methods and systems for battery pack architecture, and systems and methods for controlling battery packs at the battery string level. A battery system may include one or more battery packs having multiple battery strings composed of individual battery cells. The construction (e.g., architecture and components) of the multiple battery strings may be identical (i.e., completely identical).

[0012] Figure 1 An exemplary machine 100 according to this disclosure is depicted. Figure 1In this embodiment, machinery 100 includes a frame 102, wheels 104, implements 106, and a speed control system implemented in one or more onboard electronic devices (e.g., electronic control units or ECUs). An exemplary machine 100 is a wheel loader. However, in other examples, the machine can be other types of machinery associated with various heavy industries, including, for example, construction, agriculture, earthmoving, forestry, mining, transportation, material handling, waste management, etc. Therefore, although many examples are described with reference to wheel loader machinery, the examples according to this disclosure are also applicable to other types of machinery, including graders, scrapers, bulldozers, excavators, compactors, material handling vehicles (such as dump trucks), and other exemplary machine types.

[0013] Mechanism 100 includes a frame 102 mounted on four wheels 104, although in other examples the mechanism may have more than four wheels. The frame 102 is configured to support and / or mount one or more components of the mechanism 100. For example, the mechanism 100 includes a housing 108 coupled to the frame 102. Among other components, the housing 108 may also house an electric motor for propelling the mechanism across various terrains via the wheels 104. In some examples, multiple electric motors are included in multiple housings at multiple locations within the mechanism 100.

[0014] Machinery 100 includes an implement 106 connected to a frame 102 via a linkage assembly 110 configured to be actuated to articulate the bucket 112 of the implement 106. The bucket 112 of the implement 106 may be configured to transfer material, such as soil or debris, from one location to another. The linkage assembly 110 may include one or more cylinders 114 configured to be hydraulically or pneumatically actuated to articulate the bucket 112. For example, the linkage assembly 110 may be actuated by cylinders 114 to raise and lower relative to the frame 102 of machinery 100 and / or rotate the bucket 112.

[0015] Platform 116 is connected to frame 102 and provides access to various locations on machinery 100 for operational and / or maintenance purposes. Machinery 100 also includes an operator's cabin 118, which may be open or closed and is accessible via platform 114. Operator's cabin 118 may include one or more control devices (not shown), such as joysticks, steering wheels, pedals, levers, buttons, switches, etc. The control devices are configured to enable the operator to control machinery 100 and / or implements 106. Operator's cabin 118 may also include an operator interface, such as a display device, sound source, light source, or a combination thereof.

[0016] Machinery 100 can be used in a variety of industrial, construction, commercial, or other applications. Machinery 100 can be operated by an operator in operator cabin 118. The operator can, for example, drive machinery 100 to different locations on the work site and can also use the bucket 112 of implement 106 to pick up and store material loads. As an example, machinery 100 can be used to excavate a portion of the work site by actuating cylinder 114 to articulate the bucket 112 via linkage 110, to dig and remove dirt, rocks, sand, etc. from one part of the work site and store the load at another location.

[0017] The mechanism 100 may include a battery compartment connected to the frame 102 and including a modular battery system 120. The battery system 120 is electrically connected to one or more electric motors of the mechanism 100.

[0018] Figure 2 This is a block diagram of an example modular battery system 120. Battery system 120 can be used to provide power to machinery 100. Battery system 120 includes a battery pack 121 and optionally one or more additional battery packs 122 (e.g., two to eight battery packs). These battery packs 121, 122 can be electrically connected together in parallel or in series via a bus 124. Advantageously, the additional battery packs 122 may have the same construction as battery pack 121 (e.g., the same architecture, the same components, the same dimensions, and the same shape), allowing for a relatively straightforward modular mechanical connection to the bus 124. In particular, the bus 124 and other mechanical components do not need to be designed to accommodate battery packs with different sizes, shapes, architectures, components, etc. Because battery system 120 is modular and battery packs 121, 122 are interchangeable on bus 124, fewer battery packs can be connected in parallel for smaller battery systems and more battery packs can be connected in parallel for larger battery systems. Each of the battery packs 121 and 122 includes multiple battery strings 126A, 126B, 126C, and 126D (e.g., two to six battery strings). Although in Figure 2 The illustration for battery pack 121 shows four battery strings 126A, 126B, 126C, and 126D, but this is for illustrative purposes only. Each of the battery strings 126A, 126B, 126C, and 126D may have the same construction (e.g., the same architecture and the same components). For simplicity, Figure 2 The battery pack 121 is illustrated with battery strings 126A, 126B, 126C and 126D. It should be understood that the battery pack 122 may have battery strings with the same construction sharing battery strings 126A, 126B, 126C and 126D.

[0019] Battery string 121 can be connected in series or in parallel with battery pack 122. As discussed above, battery pack 122 may have a second plurality of strings having the same construction as the plurality of battery strings 126A, 126B, 126C, and 126D of battery pack 121. This construction allows for modular expansion of battery power output at the pack or system (module level) by adding one or more additional battery strings with the same construction. Additionally, as discussed below, the identical construction of the battery strings enables the interchangeable addition of battery strings without reconfiguring the controller to accommodate various different components and architectures at the string level or pack level.

[0020] Battery strings 126A, 126B, 126C, and 126D can be electrically connected together in parallel. Each battery string 126A, 126B, 126C, and 126D includes multiple cells 128 electrically connected in series. Each of the multiple cells can have a potential of approximately 3 volts to 4 volts. The multiple cells 128 are linked together in series to form a battery string that reaches the nominal voltage of the battery pack 121. Battery strings 126A, 126B, 126C, and 126D can be linked together in parallel to combine the output power of the battery pack 121, thereby increasing the discharge current of the battery pack 121. As an example, the battery pack 121, or a combination of the battery pack 121 with one or more additional battery packs 122, can be rated as: 350 volts to 800 volts, 1000 amperes to 1500 amperes, and / or 30 kWh to 60 kWh. Each of the battery strings 126A, 126B, 126C, and 126D may include components 129A, 129B, 129C, and 129D, which include power control components, which will be discussed later. Figure 3 and Figure 4 Further detailed discussion is needed.

[0021] At the system level, battery pack 121 may include controller 130 and pre-charge circuit 132. Controller 130 may be electrically connected to pre-charge circuit 132, battery strings 126A, 126B, 126C, and 126D, and components 129A, 129B, 129C, and 129D (including power control components). Controller 130 may be configured to control the battery pack at the battery string level. This control may be individual control of battery strings 126A, 126B, 126C, and 126D to meet system requirements (e.g., desired amperes, ampere-hours, kilowatts, kilowatt-hours, etc.). In other words, battery system 120 of the present invention has a single battery pack-level controller (controller 130) for all control functions, including control of power control components. Battery system 120 of the present invention does not consider sub-controllers or subroutines for each of battery strings 126A, 126B, 126C, and 126D. Conversely, at the system level, controller 130 can be configured to manage the functions of battery strings 126A, 126B, 126C, and 126D, as well as components 129A, 129B, 129C, and 129D. This contrasts with most power control circuits, which are multi-layered and complex, designed to control the operation of the battery system at the packing and string levels, and which must handle various battery string, component configurations, and architectures at the system or string levels.

[0022] Controller 130 may be, for example, a package controller circuit, such as an energy control module or ECM. Controller 130 can control various functions and may include processing circuitry comprising logic for performing the functions described herein. The processing circuitry may include a microprocessor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other types of processors for interpreting or executing instructions in software or firmware. In some examples, controller 130 includes logic sequencer circuitry. A logic sequencer is a state machine or other circuitry that performs a fixed series of steps in a step-by-step sequence to perform the described function. Logic sequencer circuitry may be implemented using hardware, firmware, or software.

[0023] The pre-charge circuit 132 may be a single pre-charge circuit at the pack level, but it may include a separate pre-charge contactor (not shown) for each of the battery strings 126A, 126B, 126C, and 126D to select any one of the battery strings 126A, 126B, 126C, and 126D within the battery pack 121 for pre-charging. The pre-charge circuit 132 can be used to pre-charge the load when the battery system 120 is online to power a load. Each pre-charge contactor includes a contact resistor to limit current when the battery system 120 is online. Any one of the battery strings 126A, 126B, 126C, and 126D can be selected as the first battery string connected to the load.

[0024] Figure 3 This is a schematic diagram illustrating another example of a battery system 220 for a battery pack. Battery system 220 may have a similar construction to the previously discussed battery system 120, but includes further details regarding the construction of the battery strings and other components. Battery system 220 may include multiple battery strings 226A, 226B, and 226C, and battery contactors 234A, 234A', 234B, 234B', and 234C, 234C'. Although... Figure 3 The image shows three battery strings 226A, 226B, and 226C, but this number is purely exemplary. Each of the battery strings 226A, 226B, and 226C may include a cell 128, a fuse 236, a disconnector 238, a current sensor 240, and a voltage sensor 242. Figure 3 Additional examples are shown in the previous Figure 2 The pre-charge contactor discussed in the article.

[0025] For each battery string 226A, 226B, and 226C, multiple battery cells 128 are electrically connected in series. Battery strings 226A, 226B, and 226C each have the same construction, including the same architecture and components (e.g., the same parts are used for cell 128, fuse 236, disconnector 238, current sensor 240, and voltage sensor 242, and the same series connections are used). This identical architecture and components allow battery strings 226A, 226B, and 226C to be added or removed interchangeably without reconfiguring the electronic controller. Similarly, battery contactors 234A, 234A', 234B, 234B' and 234C, 234C' may each have the same construction. Each battery string 226A, 226B, and 226C has a corresponding pair of battery contacts from battery contacts 234A, 234A', 234B, 234B' and 234C, 234C', wherein one battery contact (234A, 234B, and 234C) of the corresponding pair is connected to the positive terminal of each battery string 226A, 226B, and 226C, and the second battery contact (234A', 234B', and 234C') of the corresponding pair is connected to the negative terminal of each battery string. Due to the identical construction and parallel connection of battery strings 226A, 226B, and 226C, battery contacts 234A, 234A', 234B, 234B' and 234C, 234C' can each be rated to deliver a current less than the maximum current that the battery pack can provide. In some examples, battery contactors 234A, 234A', 234B, 234B' and 234C, 234C' are rated to withstand 100 amps or less. The battery strings 226A, 226B, and 226C connected in parallel have an output power exceeding the rated power output of any one of contactors 234A, 234A', 234B, 234B' or 234C, 234C'. Battery contactors 234A, 234A', 234B, 234B' and 234C, 234C' control the connection of battery strings 226A, 226B, and 226C to an electrical load, located on both the positive and negative branches, between the battery strings and the battery pack bus.

[0026] Cell 128, fuse 236, disconnector 238, and current sensor 240 can be connected in series, wherein at least one of the cells 128 is located on one side of fuse 236 and disconnector 238 from one or more other cells 128. Voltage sensor 242 can be configured to measure the voltage across the respective battery string 226A, 226B, or 226C. Although Figure 3Both current sensor 240 and voltage sensor 242 are shown, but according to some examples, it is not necessary to use both sensors simultaneously. As an example, voltage sensor 242 may be an analog-to-digital converter (ADC) that monitors the string voltage and produces a digital value representing the highest offline string voltage.

[0027] Controller (e.g.) Figure 2 The controller 130 can be electrically connected to battery contactors 234A, 234A', 234B, 234B' and 234C, 234C', current sensor 240 and voltage sensor 242. Figure 2 (Example of power control components referenced herein). The controller can be configured to communicate with and receive data (measurement results) from current sensor 240 and voltage sensor 242. Therefore, the controller can receive measurements such as online voltage (state of discharge), offline voltage, pre-charge, etc., from current sensor 240 and voltage sensor 242. As an example, the maximum voltage may be of interest, and the controller determines the maximum voltage of one or at most all battery strings 226A, 226B, or 226C. The controller (e.g., Figure 2 The controller 130 can be configured to switch on and off (close and open) the battery contactors 234A, 234A', 234B, 234B' and 234C, 234C'. In other words, the controller can be configured to selectively connect or disconnect each of the battery strings 226A, 226B or 226C based on measurements from corresponding sensors (e.g., current sensor 240 and / or voltage sensor 242). Therefore, the controller is a single battery pack-level controller for all battery contactors 234A, 234A', 234B, 234B' and 234C, 234C'. In short, the controller can be configured to individually (and collectively) control each of the battery strings 226A, 226B, or 226C based on measurements from sensors (e.g., voltage sensor 242 or current sensor 240) to meet system requirements (e.g., desired amperes, ampere-hours, kilowatts, kilowatt-hours, etc.). The controller can be configured to increase the power output of the battery pack by selectively commanding applicable contactors among contactors 234A, 234A', 234B, 234B' and / or 234C, 234C' to connect additional battery strings among the multiple battery strings 226A, 226B, and / or 226C. The controller can be configured to selectively decrease the power output of the battery pack by selectively commanding applicable contactors among contactors 234A, 234A', 234B, 234B' and / or 234C, 234C' to disconnect one or more battery strings among the battery strings 226A, 226B, and / or 226C.

[0028] As an example, the controller checks current sensor 240 and / or voltage sensor 242 based on system requirements and determines whether offline battery strings 226A, 226B, or 226C should be brought online. If the criteria are met, the controller connects one or more battery strings 226A, 226B, or 226C to the battery bus and connects the battery bus to the load bus. Battery strings already online can be taken offline in a similar manner (e.g., by sorting from lowest to highest voltage to determine the required current based on system requirements). Each battery string can be controlled independently of the others.

[0029] Figure 4 A schematic diagram of a single battery string 326 of system 320 is shown. It should be understood that system 320 will include additional battery strings having the same construction as battery string 326. Additionally, system 320 may include battery contactors 334A, 334A' having a construction similar to that previously discussed. Battery string 326 may include individual AA cells (particularly individual cells 328A, 328B, 328C, 328D, 328E, 328F, 328G, 328H, 328I, 328J, and 328K), fuse 236, disconnector 238, current sensor 240, and voltage sensor 242. Therefore, the construction of battery string 326 is similar to that of battery string 226 previously discussed (…). Figure 3 (Including fuse 236, disconnector 238, current sensor 240 and voltage sensor 242, but including more individual units 328A, 328B, 328C, 328D, 328E, 328F, 328G, 328H, 328I, 328J, 328K and 328L connected in series together.)

[0030] Figure 5 This is a flowchart of method 400 for expanding a battery system. Method 400 may include: providing a reference battery pack 402, which includes a plurality of battery strings, each of the plurality of battery strings having the same construction. Method 400 may include: individually controlling 404 the battery strings of the plurality of battery strings using an electronic controller to meet requirements. Method 400 may query (e.g., query system requirements) regarding adding 406 (or replacing or removing) one or more additional battery strings of the same construction to the reference battery pack to increase power output. As used in method 400, the same construction includes: the same architecture and the same components for each of the plurality of battery strings, including one or more additional battery strings, enabling the interchangeable addition of battery strings without reconfiguration of the electronic controller.

[0031] Optionally, method 400 may include adding one or more additional battery strings, including adding one or more battery packs with the same configuration as a reference battery pack. Method 400 may include modularly expanding the power output of the battery pack by adding one or more additional battery strings with the same configuration. Multiple battery strings and one or more additional battery strings may be connected in parallel to combine the output power of the battery pack. Method 400 may include adding one or more of the multiple battery strings in parallel to increase the output current capacity of the battery pack.

[0032] The output power of multiple battery strings connected in parallel and one or more additional battery strings can exceed the rated power output of one or more of the same components. For example, the output power of multiple battery strings connected in parallel can exceed the rated power output of any one of the contactors in the corresponding pair of contactors for a single battery string. Each contactor in the corresponding pair of contactors may be rated 100 amps or less, while the output power of the multiple battery strings may be, for example, 350 amps or more.

[0033] Industrial applicability

[0034] This application discloses one or more battery packs (e.g., battery packs 121 and / or 122) with a modular design, which includes battery strings (e.g., battery strings 126A, 126B, 126C, and 126D, or 226A, 226B, 226C, or 326) sharing the same common construction. The identical construction of each of the multiple battery strings includes the same architecture and the same components. This identical architecture and components allow multiple battery strings to be added or removed (connected or disconnected) interchangeably to provide the desired power output or desired output current capacity of the battery pack. This allows any number of battery strings to be used and to be combined with battery strings from other battery packs sharing the same construction. In this way, the battery packs in question can be combined to obtain a system for achieving a desired total energy capacity. The control architecture utilized does not require modification from battery string to battery string or from battery pack to battery pack because the same control logic / method / algorithm can be used due to the identical construction of the battery strings. Overall system control can be based on a single, similar circuit control. As an example, if it is necessary to add battery strings to the overall system to increase the output current capacity, two to four (or more) identical systems can be added in parallel. These systems can all be controlled by the same battery pack-level controller using the same control logic / method / algorithm.

[0035] The common construction of multiple battery strings offers additional benefits. For example, verifying the performance and reliability of the battery pack is easier because this can be done at a smaller level (e.g., at the battery string or individual battery pack level) and extrapolated to higher levels where the same construction is shared (e.g., it is not more complex or different). Additionally, the disclosed system can use components with current ratings lower than the overall current rating of the battery pack. Since each battery string is added (or removed) in parallel, and the control of the battery pack is performed at the battery string level, components such as battery string contactors (e.g., battery contactors 234A, 234A', 234B, 234B' and 234C, 234C' or battery contactors 334A, 334A') only need to be rated to the output current of the applicable individual battery string. Therefore, the output of the battery pack can be two to four times (or more) the string current output, but components rated only for the string output current of a single string can still be utilized. This reduces component costs because the system does not need to utilize components with higher load ratings rated for extreme power applications. Additionally, since higher load-rated components are not required, system components can be sourced from a wider variety of suppliers, whose supply is not as limited as that of components rated for extreme power applications.

[0036] From a mechanical assembly perspective, it is advantageous to have scalable parts (such as battery strings, battery contacts, etc.) and battery packs using the same components. A single busbar can be used to span battery pack modules of the same size, shape, and other construction. The box containing the battery pack can be swapped in or out as needed without modifying the connection layout. The modular design of the present invention is easier from a mechanical layout perspective because the overall design does not require adapting one battery pack with one physical size, shape, and / or construction to another battery pack with a different physical size, shape, and / or construction. Instead, the system of the present invention has easily expandable size, shape, parts, and architecture, and can be expanded (or reduced) relatively easily.

[0037] The detailed description above is intended to be illustrative and not restrictive. Therefore, the scope of this disclosure should be determined by reference to the appended claims and the full scope of their authorized equivalents.

Claims

1. A control system for a battery pack, the control system comprising: Multiple battery strings, each having the same construction, each battery string comprising multiple battery cells connected in series; Multiple contactors, each having the same construction, wherein each battery string has a corresponding pair of contactors, one of the corresponding pair of contactors is connected to the positive terminal of each battery string, and the second of the corresponding pair of contactors is connected to the negative terminal of each battery string; Multiple sensors, wherein each of the multiple battery strings has a corresponding sensor among the multiple sensors, the corresponding sensor being configured to measure at least one of voltage and current; and A controller connected to the plurality of sensors and the plurality of contactors, wherein the controller is configured to individually control each of the plurality of battery strings to meet system requirements based on measurement results from the plurality of sensors.

2. The control system of claim 1, wherein the controller is configured to: selectively connect or disconnect each battery string by controlling a corresponding pair of contactors for each of the plurality of battery strings based on the measurement result of a corresponding one of the plurality of sensors.

3. The control system according to any one of claims 1 to 2, wherein the plurality of battery strings are connected in parallel to combine the output power of the battery pack, wherein the output power of the plurality of battery strings connected in parallel exceeds the rated power output of any one of the plurality of contactors.

4. The control system according to any one of claims 1 to 3, wherein the identical construction of each of the plurality of battery strings includes the same architecture and the same components, and the control system further includes at least a second battery pack connected in series or in parallel with the battery pack, wherein the second battery pack has a second plurality of strings having the same construction as the plurality of battery strings of the battery pack.

5. The control system according to any one of claims 1 to 4, wherein the controller is configured to increase the power output of the battery pack by selectively commanding an appropriate contactor of the plurality of contactors to connect an additional battery string of the plurality of battery strings, and the controller is configured to selectively decrease the power output of the battery pack by selectively commanding an appropriate contactor of the plurality of contactors to disconnect one or more battery strings of the plurality of battery strings, wherein the identical configuration of the plurality of battery strings allows one or more battery strings to be interchangeably added or removed without reconfiguring the controller.

6. A method for controlling a battery pack, the method comprising: Provide multiple battery strings, each having the same construction, each battery string comprising multiple battery cells connected in series, wherein each of the multiple battery strings is connected to a corresponding pair of contactors; A sensor is provided, the sensor being configured to measure at least one of the voltage and current of each of the plurality of battery strings, wherein each respective sensor is electrically connected to an electronic controller; as well as Based on the measurement results from each sensor, the electronic controller selectively and individually controls each of the plurality of battery strings to meet the requirements.

7. The method of claim 6, wherein selective control comprises: By controlling the corresponding pair of contactors for each of the plurality of battery strings based on the measurement results of each sensor, each battery string is selectively connected or disconnected, wherein the plurality of battery strings are connected in parallel to combine the output power of the battery pack, wherein the output power of the plurality of battery strings connected in parallel exceeds the rated power output of any one of the corresponding pair of contactors.

8. The method of claim 7, wherein each of the respective pair of contactors is rated for 100 amperes or less.

9. The method according to any one of claims 6 to 8, wherein the identical construction of each of the plurality of battery strings comprises the same architecture and the same components, and wherein the identical architecture and the same components enable the plurality of battery strings to be added or removed interchangeably without reconfiguring the electronic controller.

10. The method according to any one of claims 6 to 9, further comprising: The power output of the battery pack can be modularly expanded by adding one or more additional battery strings with the same configuration.

11. The method according to any one of claims 6 to 10, further comprising: Provide at least a second battery pack connected in series or in parallel with the battery pack, wherein the second battery pack has a second plurality of battery strings having the same configuration as the plurality of battery strings of the battery pack.

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