Energy storage system and method using batteries for second-life electric vehicles

Abstract

An integrated battery energy storage system and method for integrating electric vehicle battery packs into an integrated battery energy storage system is disclosed, the integrated battery energy storage system includes a plurality of electric vehicle battery packs connected in a series / parallel arrangement, the series / parallel arrangement including a plurality of series strings of electric vehicle battery packs, each of the plurality of series strings of electric vehicle battery packs including at least two of the plurality of electric vehicle battery packs connected in series, and the plurality of series strings of electric vehicle battery packs connected in parallel.

Description

Technical Field

[0001] The present disclosure generally relates to energy storage systems and methods using second-life electric vehicle batteries, and more particularly to an integrated battery energy storage system including a plurality of electric vehicle battery packs connected in series / parallel configuration.

Background Art

[0002] Reducing the cost of an energy storage system (ESS) is an important goal for electricity ratepayers and policymakers. The main metric for measuring ESS cost is defined as the levelized cost of storage (LCOS), which includes the capital cost and operating cost of the system divided by the cumulative delivered electricity amount stored by the system, i.e., the total life cost of the ESS.

[0003] Reusing an electrochemical battery from an electric vehicle (EV) for second use or second-life stationary storage can significantly reduce the LCOS of an ESS compared to using a new battery. When an EV battery is no longer suitable for use in an EV, deploying the EV battery for stationary storage is the highest and best use of the battery. Larger-scale ESSs require a large number of batteries deployed in series and parallel electrical configurations to deliver energy at high voltage and current levels. The ESS must efficiently integrate and manage the batteries over time and effectively manage the charge / discharge cycles, whether electrically connected in front of or behind the customer's meter.

Summary of the Invention

Means for Solving the Problems

[0004] In second-life stationary storage utilization within an integrated energy storage system (ESS), it is desirable to have a system that utilizes a plurality of electric vehicle (EV) batteries.

[0005] In one aspect, Equipped with multiple electric vehicle battery packs connected in series / parallel, The aforementioned series / parallel arrangement includes multiple series strings of battery packs for electric vehicles, Each of the plurality of series strings of the electric vehicle battery pack includes at least two of the plurality of electric vehicle battery packs connected in series. An integrated battery energy storage system is disclosed, in which the multiple series strings of an electric vehicle battery pack are connected in parallel.

[0006] In another embodiment, Multiple battery packs for electric vehicles configured to store energy, An enclosure configured to enable outdoor deployment of an energy storage assembly, Multiple removable exterior enclosure panels configured to facilitate the installation and removal of the multiple electric vehicle battery packs from the enclosure, Multiple DC-DC converters configured to balance the voltage or energy storage capacity of electric vehicle battery packs connected in series, An environmental control unit within the enclosure, configured to extend the usable lifespan of the plurality of electric vehicle battery packs within the enclosure, A racking system for the plurality of electric vehicle battery packs, configured to provide electrical insulation and heat insulation between the plurality of electric vehicle battery packs, An electric vehicle battery pack control unit configured to use an electric vehicle battery pack management system without altering the manufacturer's design and intended function, An integrated battery energy storage system comprising the above is disclosed.

[0007] In one embodiment, A coupling step for connecting multiple electric vehicle battery packs in series / parallel arrangement, The step includes connecting the plurality of series strings of the electric vehicle battery pack in parallel, The aforementioned series / parallel arrangement includes multiple series strings of battery packs for electric vehicles, Each of the plurality of series strings of the electric vehicle battery pack includes at least two of the plurality of electric vehicle battery packs connected in series. A method for integrating an electric vehicle battery pack into an integrated battery energy storage system is disclosed. [Brief explanation of the drawing]

[0008] [Figure 1] A block diagram showing a utility as part of an energy storage system according to an exemplary embodiment of the present invention. [Figure 2] This is a modified electrical single-line diagram of an energy storage system according to an exemplary embodiment. [Figure 3] This figure shows a battery pack control unit (BPC) and a smart combiner according to one embodiment of the present invention. [Figure 4] This figure shows the mechanical arrangement of enclosure components according to an exemplary embodiment. [Modes for carrying out the invention]

[0009] For the sake of simplification and explanation, the principles of the embodiments will be explained primarily by reference to their examples. Numerous specific details are provided in the following description to give a deeper understanding of the embodiments. However, it will be apparent to those skilled in the art that the embodiments may be implemented without being limited to these specific details. In some examples, well-known methods and structures are not described in detail so as not to unnecessarily obscure the embodiments.

[0010] In one embodiment, an EV pack storage system (EPS) uses multiple EV battery packs as an integrated functional unit or component. In this case, the multiple EV battery packs are fairly easily aggregated and function as a larger battery within an ESS. The batteries may be racked in a special environmentally controlled enclosure within the original pack casing, installed in the EV. The special environmentally controlled enclosure functions as an integrated EV pack storage unit, and the EPS functions as a subsystem component within the overall ESS. The EV battery packs in the EPS may be electrically connected in series and parallel. Each series string is protected by an overcurrent device. The EPS enclosure is designed to facilitate the installation, removal, and replacement of EV battery packs. Each battery pack and string may be monitored by a dedicated battery pack control unit (BPC). The BPC helps ensure appropriate operating parameters and monitor the health of each EV battery pack. The battery pack control unit (BPC) can monitor the health of each EV battery pack by having the EV pack interface with an integrated battery management system (BMS). The BPC (Battery Processor) actively balances second-life batteries by managing smart combiners (SCs) to effectively utilize the charge-discharge cycles of individual packs while adjusting for capacity variations in each pack. The environment of the EPS enclosure is controlled to maintain appropriate operating temperatures and detect hazards. The EPS operates within a larger ESS (Energy Storage System), which also includes an inverter power conversion system (PCS) and supervisory control and data acquisition (SCADA). Multiple EPSs can operate integrally within the ESS. The ESS can be configured with DC or AC coupling to the inverter. The EPS can be charged with electricity supplied by on-site power generation such as solar or wind power, or by an AC power system. The EPS within the ESS can be deployed in front of (IFM) or behind (BTM) meters directly interconnected to the grid to supplement customer loads and demands.

[0011] In an exemplary embodiment, an integrated system for deploying multiple second-life electric vehicle (EV) battery packs within an energy storage system (ESS) is disclosed.

[0012] In this disclosure, what is referred to as an EV pack storage system (EPS) is an integrated functional component in which multiple EV battery packs are easily aggregated and function as a larger battery within a comprehensive ESS. The configuration and function of the EPS include (1) the EV battery packs being utilized mechanically and electrically, as in their original first-life vehicle applications, incorporating a battery management system (BMS) and similar digital serial data link formats and protocols for the battery packs, and (2) the EV battery packs being electrically configured in parallel and often in series. While EV battery packs may not have originally been designed for use in series connections, this limitation is overcome by specific designs for mounting, communication, and interconnection. This unique design includes (3) the integration of multiple EV battery packs into an environmentally controlled and monitored cabinet or enclosure (which is not considered an occupable space according to the definition of building codes or fire safety regulations, and a single enclosure or multiple enclosures may be integrated into the ESS); (4) the deployment of a battery pack control unit (BPS) as part of the EPS, integrating the necessary communications and controls for the batteries to function and operate in conjunction as a unified functional block; and (5) a smart circuit combiner providing electrical balance and overcurrent protection for all EV battery packs within the EPS.

[0013] Figure 1 is a block diagram illustrating the usefulness of the present disclosure in a preferred embodiment as part of a grid-tied energy storage system. In an exemplary embodiment, the EV pack storage system (EPS) 100 may be implemented as part of an integrated energy storage system (ESS). All thick lines 600 with arrows indicate power connections and possible power flow directions. All dashed lines 500 indicate bidirectional digital data bus connections.

[0014] The EPS100 includes multiple EV battery packs designated as Block 1, N-1, and N in Figure 1, where N represents any number of identical EV battery packs. EV battery pack 1 includes battery 1.1 and a battery management system (BMS) 1.2. EV battery packs 1.1 to N.1 are connected in series with nominal voltages that are multiples of the nominal voltage of a single pack. N EV battery packs are connected in series / parallel configurations or aggregated within a smart combiner 130 to electrically function as a larger battery within an integrated energy storage system. The smart combiner 130 is connected to a bidirectional DC-DC converter 603. The DC-DC converter 603 can provide optimal voltage matching between the aggregated EV battery packs and the inverter power conversion system (PCS) 605, so that the peak power point of the photovoltaic unit 606 changes according to temperature and load. The Smart Combiner (SC) 130 can be used to actively balance second-life batteries by effectively utilizing the charge-discharge cycles of individual packs to adjust for differences in the capacity of each pack.

[0015] When the integrated system delivers energy stored in the EV battery pack to, for example, the power grid 610, DC power flows from the EV battery pack through the smart combiner 130 and then through the DC-DC converter 603. The DC power is then converted to AC power by the PCS 605 and supplied to the power grid 610. Power from the photovoltaic unit 606 can also flow through the PCS 605, which functions as a DC / AC power converter, if available, and discharge power to the power grid 610. In this configuration, the total power supplied to the power grid 610 can be, for example, a combination of power supplied from the battery and power supplied from the photovoltaic unit.

[0016] In an exemplary embodiment, when the integrated system is delivering energy to charge EV battery packs 1 - N, the PCS 605 procures AC power from the power grid 610 and functions as an AC / DC power converter by converting the AC power to DC power. This DC power flows through the DC - DC converter 603 and through the smart combiner 130 to all of the EV battery packs 1 - N. The power from the solar power generation unit 606 can be used, if available, to reduce the required power from the power grid 610 to charge the EV battery packs 1 - N, or, when the power from the available solar power generation unit 606 is greater than the power required to charge these EV battery packs, surplus power can be fed to the power grid 610. Some system variations do not include an on - site solar power generation unit 606 and, thus, the DC - DC converter 603 may not be required.

[0017] In an exemplary embodiment, the battery management system (BMS) 1.2 monitors all the cells within the EV battery pack 1, mainly to check for mismatched cells, under - charged cells or over - charged cells in a series string. By monitoring mismatched cells and re - balancing, the usable life of the EV battery pack can be improved, and the safe operating parameters of the battery cells and the battery pack can be ensured to avoid dangerous situations. The battery pack control unit (BPC) 140 communicates with the individual EV battery packs 1 - N through a digital data bus. The supervisory control and data acquisition (SCADA) 501 communicates with the BPC 140 to confirm the charge state, health state and overall availability of the aggregated EV battery packs. In an exemplary embodiment, the SCADA 501 receives top - level commands from the power system management unit 503 through the Internet 502 to control the operation of the overall energy storage system.

[0018] SCADA501 can also communicate with the cabinet control system 150. Within the EPS100, the cabinet control system 150 can communicate with the temperature control block 151 and the hazard protection block 152. The temperature control block 151 provides air conditioning, dehumidification, ventilation, and air circulation as needed to maintain an optimal environment for the EV battery packs 1-N. The hazard detection block 152 monitors the environment within the EPS100 enclosure for smoke and over-temperature / under-temperature conditions.

[0019] Figure 2 is a modified single-line electrical circuit diagram of an energy storage system according to an exemplary embodiment, showing power flow. However, the scope of this disclosure and description is not limited to systems having the number of elements and / or components described herein.

[0020] As shown in Figure 2, the energy storage system has, for example, four EV pack storage assemblies (EPS) 100, 200, 300, and 400. Each EPS 100, 200, 300, and 400 may be identical. However, each EPS does not have to be identical, and one or more EPS 100, 200, 300, and 400 may be modified. In an exemplary embodiment, EPS 100 contains 24 EV battery packs (EVBPs) indicated as 1 to 24. Within each EVBP there are numerous series- or series-parallel connected battery modules, indicated as 1.1 of EVBP1 to 24.1 of EVBP24. There are also open contactors, which can typically be configured as one or more series-connected contactors, specified as 1.3 of EVBP1 to 24.3 of EVBP24. EVBP1 to 24 may also include other power circuits, such as pre-charge resistors and contactors, but are not limited to these. In this exemplary system, EVBP1-24 are connected in a 2S12P circuit configuration, where EVBP pairs are connected in series, and 12 of these series strings are connected in parallel. The series string pairs are 1 / 2, 3 / 4, 5 / 6, 7 / 8, 9 / 10, 11 / 12, 13 / 14, 15 / 16, 17 / 18, 19 / 20, 21 / 22, and 23 / 24. Each of the 12 series strings 1 / 2-23 / 24 is connected in the smart combiner 130 through fuses 101-112. Fuses 101-112 provide second-stage overcurrent protection to protect EV batteries 1.1-24.1 from overcurrent under abnormal conditions. Fuses 101-112 can also prevent contactors 1.3-24.3 from interrupting currents exceeding the safety contactor limits. Contactors 1.3–24.3 can provide first-stage overcurrent protection for currents below the ratings of fuses 101–112 and for other circuit isolation and connection control functions. The output of the smart combiner (SC) 130 is connected to a switch 161 that connects or isolates the power circuit of the EPS 100 from other energy storage system components. Fuse 162 protects the current capacity of the conductors and the tripping function of switch 161. In exemplary embodiments, circuit breakers or other overcurrent devices and systems may be used instead of the fuses in Figure 2.

[0021] In this system embodiment, EPS100 and 200 are connected to DCDC converter 603. EP300 and 400 are connected to DCDC converter 604. DCDC converter 603 provides optimal voltage matching between the parallel-connected EPS100 and EPS200 and inverter power conversion system (PCS) 605, and can provide optimal voltage adaptation so that the maximum power point of the solar power generation unit 606 changes with temperature and irradiance. Both DCDC converters 603 and 604 are capable of bidirectional power transmission to charge or discharge the EV battery pack. PCS605 is also bidirectional with respect to power flow.

[0022] For example, when an integrated system delivers the energy stored in the batteries of EPS100, 200, 300, and 400 to the power grid 610 and / or the local load section 607, DC power flows in parallel from EPS100 and 200 through DCDC converter 603, and from EPS300 and 400 through DCDC power converter 604. Then, the DC power can be converted to an AC power source by PCS605. Then, the AC power passes through the distribution transformer 608 (in this case, the voltage can be increased to a more efficient distribution voltage level) and through the revenue meter 609 before being connected to the power grid 610. If the power from the solar power generation unit 606 is available and utilized, it flows through PCS605 and PCS605, functions as a DC-AC power converter, and supplies power to the power grid 610 and / or the local load section 607. The total power to the power grid 610 can be obtained by subtracting the power used by the local load section 607 from the sum of the battery-supplied power and the solar power generation unit-supplied power. Also, the local load section may be supported without being connected to the power grid 610. In this case, PCS605 operates in an "off-grid" AC voltage regulation mode.

[0023] In EPS100, 200, 300, and 400, when the overall energy storage system supplies energy to charge the EV battery packs, PCS605 functions as an AC / DC power converter by supplying AC power from the power grid 610 and converting the AC power to DC power. In an exemplary embodiment, the DC power flows through DC / DC converters 603 and 604 to charge the EV battery packs in EPS100, 200, 300, and 400. Power from the photovoltaic unit 606 can be used, if available, to reduce the power required from the power grid 610 to charge the EV battery packs, or, if the power available from the photovoltaic unit 606 is greater than the power required to charge these EV battery packs and power the local load unit 607 of the "behind the meter", the surplus power can be delivered to the power grid 610.

[0024] According to an alternative embodiment shown in Figure 2, the energy storage system may include one or more of the PCS605, DCDC converter603, transformer608, and power meter609 as part of the integrated EPS100.

[0025] Figure 3 is a detailed view of the battery pack control unit 140 and smart combiner 130 as shown in Figure 1. Reference numeral 1 indicates a plurality of EV battery packs (EVBPs) with EVBP1 at the top. Reference numeral 2 indicates a plurality of EVBPs with EVBP2 at the top. In this embodiment of the EPS, EVBP1 and EVBP2 are electrically connected in series as a first series pair. Each series pair in the EPS communicates with one EV BMS interface board (EVIB) in the BPC. First, at the top level, BMS1.2 and BMS2.2 communicate with EVIB141 via digital data buses 504 and 505, respectively. The communication protocol is the Controller Area Network Bus (CAN bus), as used in the manufacturer's electric vehicle applications. All other EVBP series pairs in the EPS communicate in a similar manner. The control circuit 142 aggregates data from all EVIBs within the BPC 140, provides a Modbus® digital communication link 507 to an external system control unit of the EPS, and provides a Modbus link 506 to the smart combiner 130. In an exemplary embodiment, the Modbus digital communication line 507 communicates with the Integrated Energy System (SCADA) (element 501 in Figure 1) to report the health, availability, and charge status of the "composite" battery, which consists of a series / parallel connection of all EV battery packs. The Modbus data link 506 connects the control circuit 142 to the control circuit 138 to actively control the balance of each EV battery pack in the series string.

[0026] In an exemplary embodiment, balancing of each EV battery pack in a series string can be performed, for example, by monitoring the voltage, current, and temperature of each EV battery pack, and then transferring energy from the higher-voltage pack to the lower-voltage pack of the two packs in the series string. For example, if EVBP1 has a higher voltage than EVBP2, the semiconductor switch 132 is closed, current flows from battery 1.1 through inductor 137, the semiconductor switch 132 is opened, and the current through inductor 137 flows through diode 135 to battery 2.1, completing one energy transfer cycle. This energy transfer cycle is repeated at a high frequency for a time proportional to the desired energy transfer. If EVBP2 has a higher voltage than EVBP1, the semiconductor switch 134 is closed, current flows from battery 2.1 through inductor 137, the semiconductor switch 134 is opened, and the current through inductor 137 flows through diode 133 to battery 1.1, completing one energy transfer cycle.

[0027] Figure 3 illustrates a method for balancing batteries in a series battery string, but this disclosure is not limited to a method for balancing any one battery or the number of EVBPs in a series string. In exemplary embodiments, the energy storage system includes interconnection and interaction of the battery pack control unit 140, the EV battery pack battery management system (1.2 and 2.2 in this embodiment), the smart combiner 130, and the entire system control unit via the data link 507. Fuses 131 and 136 may be used to provide fault isolation between the series string of EVBPs 1 and 2 and the parallel circuits of the + bus 601 and - bus 602 of all series strings. In exemplary embodiments, for example, all other series strings can be protected in a similar manner.

[0028] In exemplary embodiments, the energy storage system may include, in addition to each of the elements shown in Figure 1, a weatherproof enclosure and a racking system for EV battery packs within an EV pack storage system (EPS) box 100. Figure 4 shows an embodiment of the enclosure which may include a fixed and removable external insulation panel 60. The enclosure 50 may be designed such that, for example, the battery system and system control unit are accessible from outside the enclosure, and the enclosure or cabinet may be designed as a cabinet that is not an occupied space as defined by building or fire codes. In exemplary embodiments, the enclosure 50 is an outdoor-rated enclosure that enables outdoor deployment of the energy storage assembly.

[0029] In exemplary embodiments, the racking system 40 can be manufactured from structural steel and configured to hold EV battery packs 1-24. For example, each pack in the main structure of the EV Pack Storage System (EPS) may weigh more than 600 pounds (272 kilograms). The side panels 60 of the enclosure 50 can be removed, for example, to allow the EV battery packs 1-24 to be attached and detached fairly easily with a forklift. In addition, the racking system 40 is designed to allow air to flow between the multiple EV battery packs. For example, each EV battery pack can be electrically isolated from the racking system 40 by standoffs 30. The EV battery packs can be cooled and heated by a temperature control system 151, for example, under the direction of a cabinet control system 150. The temperature control system 151 may include cooling, dehumidification and other environmental controls as means to extend the service life of the electric vehicle battery packs. A hazard detection system 152 can provide an alarm to the cabinet control system 150 when smoke, gas, or temperature conditions outside the operating range are detected.

[0030] The functions of the smart combiner 130 and the battery pack control unit 140 are described in relation to the contents of Figure 1. The smart combiner 130, the battery pack control unit 140, the cabinet control system 150, the temperature control system 151, and the hazard detection system 152 are not shown to scale or to have specific physical characteristics. One or more of the smart combiner 130, the battery pack control unit 140, the cabinet control system 150, the temperature control system 151, and the hazard detection system 152 can be mounted on an EPS enclosure. In exemplary embodiments, the fixed and removable exterior panels 60 of the enclosure 50 may be insulated.

[0031] The technologies consistent with this disclosure provide, in particular, energy storage systems and methods using batteries for second-life electric vehicles. While various exemplary embodiments of the disclosed systems and methods have been described above, it should be understood that they are disclosed for illustrative purposes only, and not limiting purposes. The exemplary embodiments described above are not exhaustive, and this disclosure is not limited to the exact forms disclosed. Various modifications and variations are possible in light of the above teachings, or can be obtained from the practice of this disclosure without departing from the breadth or scope of this disclosure.

Claims

1. Equipped with multiple electric vehicle battery packs connected in series / parallel configuration, The aforementioned series / parallel arrangement includes multiple series strings of battery packs for electric vehicles, Each of the plurality of series strings of the electric vehicle battery pack includes at least two of the plurality of electric vehicle battery packs connected in series. The aforementioned series strings of the electric vehicle battery pack are connected in parallel. The aforementioned multiple battery packs for electric vehicles are battery packs for second-life electric vehicles, The aforementioned second-life electric vehicle battery pack is a battery that is used for a purpose other than its first-life use in an electric vehicle. The aforementioned multiple electric vehicle battery packs, connected in series / parallel configurations, are an integrated battery energy storage system that was not originally designed to be connected in series.

2. The integrated battery energy storage system according to claim 1, wherein the plurality of electric vehicle battery packs are used without reconfiguring or modifying the manufacturer's pack casing or enclosure.

3. The integrated battery energy storage system according to claim 1, wherein the plurality of electric vehicle battery packs are used together with a manufacturer's battery management system that is originally integrated into each of the plurality of electric vehicle battery packs.

4. The integrated battery energy storage system according to claim 1, wherein each of the plurality of series strings is protected by a circuit combiner having an overcurrent device connected in series with each of the plurality of series strings.

5. Each of the aforementioned series strings is protected by a smart combiner equipped with multiple DC-DC converters. The integrated battery energy storage system according to claim 1, wherein the smart combiner is configured to balance two or more electric vehicle battery packs in a series string by transferring energy from one electric vehicle battery pack in a series string to another, or by transferring energy from one electric vehicle battery pack in a series string to another.

6. A racking system for the aforementioned multiple electric vehicle battery packs, An enclosure having internal environmental control and including a removable panel configured to facilitate the installation or replacement of the aforementioned multiple electric vehicle battery packs, The integrated battery energy storage system according to claim 1, further comprising:

7. The integrated battery energy storage system according to claim 1, further comprising a battery pack control unit configured to communicate with and control the battery management systems located inside each of the plurality of electric vehicle battery packs.

8. Multiple electric vehicle battery packs connected in series / parallel configurations, configured to store energy, An enclosure configured to enable outdoor deployment of an energy storage assembly, Multiple removable exterior enclosure panels configured to facilitate the installation and removal of the multiple electric vehicle battery packs from the enclosure, Multiple DC-DC converters configured to balance the voltage or energy storage capacity of electric vehicle battery packs connected in series, An environmental control unit within the enclosure is configured to extend the usable life of the multiple electric vehicle battery packs within the enclosure, A racking system for the plurality of electric vehicle battery packs, configured to provide electrical insulation and heat insulation between the plurality of electric vehicle battery packs, An electric vehicle battery pack control unit configured to use an electric vehicle battery pack management system without altering the manufacturer's design and intended function, Equipped with, The aforementioned multiple battery packs for electric vehicles are battery packs for second-life electric vehicles, The aforementioned second-life electric vehicle battery pack is used for purposes other than its first-life use in electric vehicles. The aforementioned multiple electric vehicle battery packs, connected in series / parallel configurations, are an integrated battery energy storage system that was not originally designed to be connected in series.

9. Converts DC electric vehicle battery pack power to AC electric grid power. The integrated battery energy storage system according to claim 8, further comprising a bidirectional power converter configured to convert AC electric grid power to charge a DC electric vehicle battery pack.

10. The integrated battery energy storage system according to claim 8, wherein the plurality of electric vehicle battery packs are used without reconfiguring or modifying the manufacturer's pack casing or enclosure.

11. The integrated battery energy storage system according to claim 8, wherein the plurality of electric vehicle battery packs are used together with a manufacturer's battery management system that is originally integrated into each of the plurality of electric vehicle battery packs.

12. The integrated battery energy storage system according to claim 8, wherein the series string of the plurality of electric vehicle battery packs is protected by a circuit combiner equipped with an overcurrent device.

13. The series string of the aforementioned multiple electric vehicle battery packs is protected by a smart combiner equipped with multiple DC-DC converters. The integrated battery energy storage system according to claim 8, wherein the smart combiner is configured to balance two or more electric vehicle battery packs in a series string by transferring energy from one electric vehicle battery pack in the series string to another, or by transferring energy from one electric vehicle battery pack in the series string to another.

14. A coupling step for connecting multiple electric vehicle battery packs in series / parallel arrangement, The connection step includes connecting multiple series strings of electric vehicle battery packs in parallel, The series / parallel arrangement includes the plurality of series strings of the electric vehicle battery pack, Each of the plurality of series strings of the electric vehicle battery pack includes at least two of the plurality of electric vehicle battery packs connected in series. The aforementioned multiple battery packs for electric vehicles are second-life battery packs for electric vehicles, and these second-life battery packs are used for purposes other than their first-life use in electric vehicles. A method for integrating electric vehicle battery packs, which are connected in series / parallel arrangements and are not originally designed to be connected in series, into an integrated battery energy storage system.

15. A first usage step involves using the aforementioned multiple electric vehicle battery packs without reconfiguring or modifying the manufacturer's pack casing or enclosure, The method according to claim 14, further comprising a second use step of using the plurality of electric vehicle battery packs, which are used together with a manufacturer's battery management system that is originally integrated into each of the plurality of electric vehicle battery packs.

16. The method according to claim 14, further comprising a protection step of protecting each of the plurality of series strings with a circuit combiner having an overcurrent device connected in series with each of the plurality of series strings.

17. The method further includes a protection step of protecting each of the aforementioned series strings by a smart combiner, The method according to claim 14, wherein the smart combiner comprises a plurality of DC-DC converters configured to balance two or more electric vehicle battery packs in a series string by transferring energy from one electric vehicle battery pack in a series string to another, or by transferring energy from one electric vehicle battery pack in a series string to another.

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