FORM 2
THE PATENTS ACT 1970
[39 OF 1970]
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10; rule 13]
TITLE: SYSTEM, CONTROL UNIT AND METHOD FOR PRIORITIZING
CHARGING OF BATTERY PACKS IN ENERGY STORAGE DEVICES
Name and Address of the Applicant:
TATA MOTORS LIMITED, an Indian company having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001, Maharashtra, INDIA.
Nationality: Indian
The following specification particularly describes the invention and the manner in which it is to
be performed.
2
TECHNICAL FIELD
[001] The present disclosure generally relates to energy storage devices and more particularly, to
a system, a control unit and a method for prioritizing charging of battery packs in energy storage
devices.
5 BACKGROUND OF THE DISCLOSURE
[002] In the automotive and transportation marketplace, an energy storage device for an electric
vehicle comprises of a plurality of battery packs or modules connected in parallel for achieving
the desired performance and range of the vehicle. Typically, each of these battery packs have a
plurality of cells connected in series. Generally, in a new battery pack, the plurality of cells in a
10 battery pack are well balanced. However, as the plurality of cells in a battery pack are subjected to
multiple charge-discharge cycles, deviation in capacitance of the plurality of cells occurs which
generally is due to multiple factors such as a process for manufacturing of a cell, shelf-life, usage,
different electrochemical characteristics between the respective cell packs etc. This results in
imbalance issues in battery packs such that a specific cells in a battery pack may be overcharged
15 while the battery pack is charged, and a specific cell may also be over discharged while the energy
storage device is discharged. Such imbalance issues cause direct impact on performance of the
vehicle, for example, reduction in vehicle range, derated battery, vehicle performance, and sudden
vehicle stop in some of the cases.
20 [003] Conventionally, a passive cell balancing mechanism is provided for balancing charges in
the energy storage device of electric vehicles. During passive cell balancing, all the battery packs
in the energy storage device get a fixed short-duration window to balance themselves. More
specifically, a voltage-based cell balancing occurs between cells in a battery pack for a predefined
time duration during the charging process. However, all the battery packs in the energy storage
25 device may not be able to balance completely due to huge charge imbalance in some battery packs.
Due to this, the balancing magnitude is significantly less in one charge cycle, and thus in order to
balance a significant cell voltage difference between cells in some battery packs, the battery packs
undergo multiple charging cycles or predetermined balancing process. This is, however, an
expensive process for vehicle manufacturers.
30
3
[004] In view of the above discussion, there exists a need for an efficient charging and balancing
mechanism to improve life of the energy storage device.
[005] The information disclosed in this background of the disclosure section is only for
5 enhancement of understanding of the general background of the invention and should not be taken
as an acknowledgement or any form of suggestion that this information forms the prior art already
known to a person skilled in the art.
SUMMARY OF THE DISCLOSURE
10 [006] In an embodiment, a method for prioritizing charging of battery packs in an energy storage
device is disclosed. The method includes receiving, by a control unit, charge information of a
plurality of battery packs connected in parallel in an energy storage device. The method includes
determining, by the control unit, a charge imbalance value for each battery pack of the plurality of
battery packs based on the charge information of the corresponding battery pack. The method
15 includes determining, by the control unit, a charging priority value for each battery pack of the
plurality of battery packs based on the charge imbalance value associated with at least one other
battery pack of the plurality of battery packs. The method includes selectively controlling, by the
control unit, charging of one or more battery packs of the plurality of battery packs based on the
charging priority value associated with the one or more battery packs.
20
[007] In another embodiment, a control unit for prioritizing charging of battery packs in an
energy storage device is disclosed. The control unit includes a memory and a processor. The
memory is configured to store instructions and the processor configured to execute the instructions
stored in the memory and thereby cause the processor to receive charge information of a plurality
25 of battery packs connected in parallel in an energy storage device. The processor is configured to
determine a charge imbalance value for each battery pack of the plurality of battery packs based
on the charge information of the corresponding battery pack. The processor is configured to
determine a charging priority value for each battery pack of the plurality of battery packs based on
the charge imbalance value associated with at least one other battery pack of the plurality of battery
30 packs. The processor is configured to selectively control charging of one or more battery packs of
4
the plurality of battery packs based on the charging priority value associated with each battery
pack of the plurality of battery packs.
[008] In yet another embodiment, a system for prioritizing charging of battery packs in an energy
5 storage device is disclosed. The system includes a plurality of battery packs connected in parallel,
a plurality of switches, a plurality of current limiting circuits, and a control unit. Each switch of
the plurality of switches is connected in series with a corresponding battery pack of the plurality
of battery packs. Each current limiting circuit of the plurality of current limiting circuits is
connected in parallel to a corresponding switch. The control unit is electrically coupled to the
10 plurality of switches and the plurality of current limiting circuits. The control unit is configured to
receive charge information of the plurality of battery packs. The control unit is configured to
determine a charge imbalance value for each battery pack of the plurality of battery packs based
on the charge information of the corresponding battery pack. The control unit is configured to
determine a charging priority value for each battery pack of the plurality of battery packs based on
15 the charge imbalance value associated with at least one other battery pack of the plurality of battery
packs. The control unit is configured to selectively control charging of one or more battery packs
of the plurality of battery packs based on the charging priority value associated with each battery
pack of the plurality of battery packs using the corresponding one or more switches of the plurality
of switches.
20
[009] The foregoing summary is illustrative only and is not intended to be in any way limiting.
In addition to the illustrative aspects, embodiments, and features described above, further aspects,
embodiments, and features will become apparent by reference to the drawings and the following
detailed description.
25
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[010] The novel features and characteristics of the disclosure are set forth in the appended claims.
The disclosure itself, however, as well as a preferred mode of use, further objectives, and
30 advantages thereof, will best be understood by reference to the following detailed description of
an illustrative embodiments when read in conjunction with the accompanying figures. One or more
5
embodiments are now described, by way of example only, with reference to the accompanying
figures wherein like reference numerals represent like elements and in which:
[011] FIG. 1A shows a system level architecture illustrating a system for prioritizing charging
5 of battery packs in an energy storage device, in accordance with an embodiment of the present
disclosure;
[012] FIG. 1B illustrates a system for prioritizing charging of battery packs in an energy storage
device, in accordance with an embodiment of the present disclosure;
10
[013] FIG. 2 illustrates a control unit for prioritizing charging of battery packs in an energy
storage device, in accordance with an embodiment of the present disclosure; and
[014] FIG. 3 illustrates a method of operating the system for prioritizing charging of battery
15 packs in the energy storage device, in accordance with an embodiment of the present invention.
[015] It should be appreciated by those skilled in the art that any block diagrams herein represent
conceptual views of illustrative systems embodying the principles of the present subject matter.
Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams,
20 pseudo code, and the like represent various processes which may be substantially represented in
computer readable medium and executed by a computer or processor, whether or not such
computer or processor is explicitly shown.
DETAILED DESCRIPTION
25 [016] In the present document, the word “exemplary” is used herein to mean “serving as an
example, instance, or illustration”. Any embodiment or implementation of the present subject
matter described herein as “exemplary” is not necessarily to be construed as preferred or
advantageous over other embodiments.
30 [017] While the disclosure is susceptible to various modifications and alternative forms, specific
embodiment thereof has been shown by way of example in the drawings and will be described in
6
detail below. It should be understood, however that it is not intended to limit the disclosure to the
particular forms disclosed, but on the contrary, the disclosure is to cover all modifications,
equivalents, and alternative falling within the spirit and the scope of the disclosure.
5 [018] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover
a non-exclusive inclusion, such that a setup, device, or method that comprises a list of components
or steps does not include only those components or steps but may include other components or
steps not expressly listed or inherent to such setup or device or method. In other words, one or
more elements in a device or system or apparatus proceeded by “comprises… a” does not, without
10 more constraints, preclude the existence of other elements or additional elements in the device or
system or apparatus.
[019] In the following detailed description of the embodiments of the disclosure, reference is
made to the accompanying drawings that form a part hereof, and in which are shown by way of
15 illustration specific embodiments in which the disclosure may be practiced. These embodiments
are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it
is to be understood that other embodiments may be utilized and that changes may be made without
departing from the scope of the present disclosure. The following description is, therefore, not to
be taken in a limiting sense.
20
[020] Referring now to FIGS. 1A and 1B, a system 100 for prioritizing charging of battery packs
in an energy storage device 110 is illustrated in accordance with an embodiment of the present
disclosure. The system 100 includes an energy storage device 110 and a source 130. The energy
storage device 110 stores energy and then discharges it for powering any machine or component.
25 The source 130 may be any power source that may supply power to charge or recharge the energy
storage device 110. In an example, the source 130 may be a DC source.
[021] In an embodiment, the energy storage device 110 includes a plurality of battery packs 102-
1, 102-2, 102-3… 102-N that are connected in parallel. Each of the battery packs 102-1, 102-2,
30 102-3… 102-N includes a plurality of cells 104-1, 104-2, 104-3,….104-N. Further, each of the
battery packs 102-1, 102-2, 102-3… 102-N includes a positive terminal and a negative terminal.
7
The source 130 is connected to the positive terminals and the negative terminals of the cell packs
102-1, 102-2, 102-3… 102-N.
[022] Typically, all battery packs may not have equal charges. In an example, battery packs of
5 the same dimensions, shape and capacity may have different total capacities, different internal
resistances, different self-discharge rates, etc. In addition, the battery packs may also age
differently, adding another variable in life of the battery pack. As such, a battery pack is limited in
performance by a lowest capacity cell in the battery pack. In other words, once the lowest capacity
cell (i.e., weakest cell) is depleted, the entire battery pack may be effectively depleted.
10
[023] Various embodiments of the present disclosure disclose an efficient passive balancing
mechanism between cells in each battery pack of the energy storage device 110. In an embodiment,
the system 100 includes a control unit 150 configured to perform target battery pack balancing by
determining charge imbalance value of battery packs. More specifically, a charging priority value
15 is assigned to each battery pack in the energy storage device 110 based on the charge imbalance
value associated with corresponding battery pack. During said target based cell balancing, the
balancing time of the most imbalanced cell is substantially increased without any change in an
overall battery charging time. More specifically, the most imbalanced cell gets the most balancing
time, and the least imbalanced cell gets the least balancing time based on the charging priority
20 value. In general, the control unit 150 facilitates cell balancing for each battery pack in the energy
storage device 110 by charging the plurality of battery packs 102-1, 102-2, 102-3… 102-N such
that, the most imbalanced battery pack is prioritized for charging and balancing when compared
with a battery pack with less or no charge imbalance to avoid imbalance between cells in each
battery pack and the plurality of battery packs 102-1, 102-2, 102-3… 102-N connected in parallel.
25
[024] In an embodiment, the system 100 further includes current limiting circuits 108, and
switches 110 which facilitate cell balancing. More specifically, the switches 110 include a plurality
of switches 110-1, 110-2, …, 110-N. In an embodiment, each switch is connected in series with a
corresponding battery pack of the plurality of battery packs 102-1, 102-2, 102-3… 102-N and is
30 operated to control the charging of the corresponding battery pack. As can be seen in FIG. 1B,
each of the battery packs 102-1, 102-2, 102-3… 102-N have a switch connected in series. For
8
example, a switch 106-1 is connected in series with the battery pack 102-1, a switch 106-2 is
connected in series with the battery pack 102-2, and so on. The a plurality of switches 106-1, 106-
2, …, 106-N control charging of corresponding battery packs in the energy storage device 110.
The current limiting circuits 108 include a plurality of current limiting circuits 108-1, 108-2, …,
5 108-N. Each current limiting circuit is connected in parallel to a corresponding switch for limiting
current delivered to the corresponding battery pack. For example, the current limiting circuit 108-
1 is connected in parallel to the switch 106-1, the current limiting circuit 108-2 is connected in
parallel to the switch 106-2 and so on as shown in FIG. 1B. The current limiting circuits 106
impose a limit on current flowing to the plurality of battery packs 102-1, 102-2, 102-3… 102-N
10 from the source 130. In an example, each current limiting circuit of the plurality of current limiting
circuits 108-1, 108-2, …, 108-N include a variable resistor and a control switch. It shall be noted
that the resistance value of the variable resistor may be adapted to limit the current flowing through
the corresponding battery pack as desired. The control switch is operated by the control unit 150
to control operation of a corresponding current limiting circuit. Further, it shall be noted that the
15 plurality of current limiting circuits 108-1, 108-2, …, 108-N including the variable resistor is
described for exemplary purposes and each current limiting circuit may include one or more
components different from those described herein but limited to reducing the current flowing to a
corresponding battery pack. Determining charging priority value based on charge imbalance and
balancing of charge between cells in each of the plurality of battery packs based on the charging
20 priority value will be described next with reference to FIG. 2.
[025] FIG. 2 illustrates the control unit 150 for prioritizing charging of battery packs in the
energy storage device 108, in accordance with an embodiment of the present disclosure. In an
embodiment, the control unit 150 is a standalone processor embodied within a Battery
25 Management System (BMS) capable of controlling the operations of a machine such as, charging
of a vehicle.
[026] The term ‘charge imbalance’ as used herein refers to a capacity mismatch of individual
cells in a battery pack. This charge imbalance may cause some of the cells in the battery pack to
30 reach their full charging capacity or discharge faster than other cells in the battery packs. For
example, the battery pack 102-1 has 3 cells (i.e., 104-1, 104-2, 104-3) and each cell has a charge
9
of 2200mAh. If cell 104-1 discharges 100mAh, cell 104-2 discharges by 100mAh and cell 104-3
discharges by 200mAh from a fully charged state, the cells 104-1 and 104-2 will have a chemical
state of charge of 95.4%, but the cell 104-3 will be 91%. Hence, the charge imbalance in battery
pack 102-1 is 4.4%. It shall be noted that although the charge imbalance value is determined based
5 on SoC of individual cells in the battery pack, the charge imbalance value may be determined
based on voltage values as will be described later.
[027] The control unit 150 is depicted to include a processor 202, a memory 204, an Input/Output
module 206, and a communication interface 208. It shall be noted that, in some embodiments, the
10 control unit 150 may include more or fewer components than those depicted herein. The various
components of the control unit 150 may be implemented using hardware, software, firmware or
any combinations thereof. Further, the various components of the control unit 150 may be operably
coupled with each other. More specifically, various components of the control unit 150 may be
capable of communicating with each other using communication channel media (such as buses,
15 interconnects, etc.). It is also noted that one or more components of the control unit 150 may be
implemented in a single server or a plurality of servers, which are remotely placed from each other.
[028] In one embodiment, the processor 202 may be embodied as a multi-core processor, a single
core processor, or a combination of one or more multi-core processors and one or more single core
20 processors. For example, the processor 202 may be embodied as one or more of various processing
devices, such as a coprocessor, a microprocessor, a controller, a digital signal processor (DSP), a
processing circuitry with or without an accompanying DSP, or various other processing devices
including, a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip,
or the like.
25
[029] In one embodiment, the memory 204 is capable of storing machine executable instructions,
referred to herein as instructions 205. In an embodiment, the processor 202 is embodied as an
executor of software instructions. As such, the processor 202 is capable of executing the
instructions 205 stored in the memory 204 to perform one or more operations described herein.
30 The memory 204 can be any type of storage accessible to the processor 202 to perform respective
functionalities, as will be explained in detail with reference to FIGS. 4A-4B. For example, the
10
memory 204 may include one or more volatile or non-volatile memories, or a combination thereof.
For example, the memory 204 may be embodied as semiconductor memories, such as flash
memory, mask ROM, PROM (programmable ROM), EPROM (erasable PROM), RAM (random
access memory), etc. and the like.
5
[030] In an embodiment, the processor 202 is configured to execute the instructions 205 for: (1)
determining a charge imbalance value for each battery pack of the plurality of battery packs, (2)
comparing the charge imbalance value associated with each battery pack of the plurality of battery
packs with at least one threshold value, (3) classifying each battery pack of the plurality of battery
10 packs into one or more categories, (4) determining a battery pack with highest charge imbalance
in each category, (5) determining a charging priority value for each battery pack of the plurality of
battery packs, and (6) selectively controlling, by the control unit, charging of one or more battery
packs of the plurality of battery packs.
15 [031] In an embodiment, the I/O module 206 may include mechanisms configured to receive
inputs from and provide outputs to an operator of the control unit 150. The term ‘operator of the
control unit 150’ as used herein may refer to one or more individuals, whether directly or indirectly,
associated with charging the energy storage device 110. To enable reception of inputs and provide
outputs to the control unit 150, the I/O module 206 may include at least one input interface and/or
20 at least one output interface. The I/O module 206 may be used by the operator of the control unit
150 to provide at least one threshold value, charging priority assignment policies, control policies,
category policies, and the like. The at least one threshold value may indicate threshold values for
classifying battery packs in different categories. This optimizes the process of determining
charging priority value for each battery pack of the plurality of battery packs 102-1, 102-2, 102-
25 3… 102-N by reducing computational resources. More specifically, each charge imbalance value
associated with a battery pack will not be compared with all other charge imbalance values
associated with other battery packs in the energy storage device 110. Rather, the plurality of battery
packs 102-1, 102-2, 102-3… 102-N will be classified into categories based on the at least one
threshold value and then comparison will be performed with each category to determine the
30 charging priority value as will be described in detail later.
11
[032] Examples of the input interface may include, but are not limited to, a keyboard, a mouse,
a joystick, a keypad, a touch screen, soft keys, a microphone, and the like. Examples of the output
interface may include, but are not limited to, a display such as a light emitting diode display, a
thin-film transistor (TFT) display, a liquid crystal display, an active-matrix organic light-emitting
5 diode (AMOLED) display, a microphone, a speaker, a ringer, and the like. It shall be noted that,
the I/O module 206 is an optional component and some the control unit 150 may be implemented
without the I/O module 206. In an example, if the control unit 150 is implemented in the BMS of
an electric vehicle, then the control unit 150 may not include the I/O module 206. As such, the at
least one threshold value, charging priority assignment policies, control policies, category policies,
10 and the like may be programmed and stored in the memory 204 of the control unit 150.
[033] The communication interface 208 may include mechanisms configured to communicate
with external entities/peripheral devices, for example, one or more sensors 250 for receiving
charge information. In an embodiment, the charge information includes one of: a State of Charge
15 (SoC) of each cell of the plurality of cells 104-1, 104-2, 104-3,….104-N in each battery pack of
the plurality of battery packs 102-1, 102-2, 102-3… 102-N and a voltage value of each cell of a
plurality of cells 104-1, 104-2, 104-3,….104-N in each battery pack of the plurality of battery
packs 102-1, 102-2, 102-3… 102-N.
20 [034] In an embodiment, the one or more sensors 250 (shown in FIG. 2) may be used to detect
voltage values in each cell of the plurality of cells 104-1, 104-2, 104-3,….104-N in each battery
pack of the plurality of battery packs 102-1, 102-2, 102-3… 102-N. These voltage values from the
plurality of cells 104-1, 104-2, 104-3,….104-N in the plurality of battery packs 102-1, 102-2, 102-
3… 102-N are collated together as charge information and are received from the one or more
25 sensors 250. It shall be noted that embodiments of the present invention will hereinafter be
described with reference to voltage values of the plurality of cells 104-1, 104-2, 104-3,….104-N
in each of the plurality of battery packs 102-1, 102-2, 102-3… 102-N. However, as already
indicated SoCs of the plurality of cells 104-1, 104-2, 104-3,….104-N in each of the plurality of
battery packs 102-1, 102-2, 102-3… 102-N may also be collated as charge information and
30 received by the communication interface 208.
12
[035] The control unit 150 is depicted to be in operative communication with a database 220. In
one embodiment, the database 220 is configured to store charging priority assignment policies,
control policies, category policies, threshold values, one or more category information, historical
charge information, one or more parameters of the energy storage device 110, etc. In an example,
5 the charging priority assignment policies define a relationship between the threshold value and
category. This ensures battery packs within a specific category are prioritized for charging. As
such, charging priority assignment policies will include prioritization for categories also. In an
example, the charging priority assignment policies will be defined such that battery packs
classified in a category for having change imbalance greater than 150mV will have a higher
10 priority when compared with a category which has battery packs with charge imbalance between
greater than 100mV but less than 150mV. It shall be noted that the charging priority assignment
policy described above is for exemplary purposes and the charging priority assignment policy may
be varied based on operator defined rules which may be customized to suit different energy storage
devices.
15
[036] The database 220 may include multiple storage units such as hard disks and/or solid-state
disks in a redundant array of inexpensive disks (RAID) configuration. In some embodiments, the
database 220 may include a storage area network (SAN) and/or a network attached storage (NAS)
system. In one embodiment, the database 220 may correspond to a distributed storage system,
20 wherein individual databases are configured to store custom information, such as, battery pack
specifications, historical charge imbalance values, charging priority assignment policies, control
policies, category policies, etc. In some embodiments, the database 220 is integrated within the
control unit 150. For example, the control unit 150 may include one or more hard disk drives as
the database 220. In other embodiments, the database 220 is external to the control unit 150 and
25 may be accessed by the control unit 150 using a storage interface (not shown in FIG. 2). The
storage interface is any component capable of providing the processor 202 with access to the
database 220. The storage interface may include, for example, an Advanced Technology
Attachment (ATA) adapter, a Serial ATA (SATA) adapter, a Small Computer System Interface
(SCSI) adapter, a RAID controller, a SAN adapter, a network adapter, and/or any component
30 providing the processor 302 with access to the database 220.
13
[037] As already explained, the communication interface 208 is configured to receive the charge
information of the plurality of battery packs 102-1, 102-2, 102-3… 102-N connected in parallel in
an energy storage device 108 and forwards the charge information to the processor 202. The
processor 202 in conjunction with the instructions in the memory 204 are configured to process
5 the charge information to selectively control charging of one or more battery packs of the plurality
of battery packs 102-1, 102-2, 102-3… 102-N and ensure balancing of the plurality of battery
packs 102-1, 102-2, 102-3… 102-N. As already explained, the charge information may include
one of: SoC of each cell of the plurality of cells 104-1, 104-2, 104-3,….104-N in each battery pack
of the plurality of battery packs 102-1, 102-2, 102-3… 102-N and a voltage value of each cell of
10 a plurality of cells 104-1, 104-2, 104-3,….104-N in each battery pack of the plurality of battery
packs 102-1, 102-2, 102-3… 102-N.
[038] The processor 202 in conjunction with the instructions 205 is configured to determine a
charge imbalance value for each battery pack of the plurality of battery packs 102-1, 102-2, 102-
15 3… 102-N based on the charge information of the corresponding battery pack. In an embodiment,
a maximum voltage value and a minimum voltage value are determined from voltage values
associated with the plurality of cells 104-1, 104-2, 104-3,….104-N in a corresponding battery
pack. In an example, if the battery pack 102-1 has cells 104-1, 104-2, 104-3, and 104-4 with voltage
values, 3.55V, 3.45V, 3.4 V, 3.5V, respectively, the maximum voltage value Vmax_102-1 in the
20 battery pack 102-1 is 3.55V of cell 104-1 and the minimum voltage value Vmin_102-1 in the battery
pack 102-1 is 3.4V of cell 104-3. In an embodiment, the charge imbalance value VCimb_102-1 is
determined for the corresponding battery pack based on the maximum voltage value and the
minimum voltage value. For example, the charge imbalance value of the battery pack 102-1 is
150mV (i.e., VCimb_102-1 = Vmax_102-1 - Vmin_102-1). As can be seen in the example above, the voltage
25 values of cells in the corresponding battery pack (i.e., battery pack 102-1) are only used to
determine charge imbalance in the battery pack 102-1. Similarly, if the SoCs of the plurality of
cells 104-1, 104-2, 104-3,….104-N are used to determine the charge imbalance value in a battery
pack, then a maximum SoC and a minimum SoC from SoCs associated with the plurality of cells
104-1, 104-2, 104-3,….104-N in a corresponding battery pack are determined. Thereafter, the
30 charge imbalance value for the battery pack is determined based on the maximum SoC and the
minimum SoC. In general, if SoCs of the plurality of cells 104-1, 104-2, 104-3,….104-N in the
14
battery pack 102-1 are used to determine charge imbalance value of the battery pack 102-1, then
the charge imbalance value SoCimb_102-1 in the battery pack 102-1 is determined based on maximum
SoC (SoCmax_102-1) and minimum SoC (SoCmin_102-1) of cells in the battery pack 102-1 i.e.,
SoCimb_102-1 = SoCmax_102-1 - SoCmin_102-1.
5
[039] In an embodiment, the processor 202 in conjunction with the instructions 205 in the
memory 204 is configured to determine a charging priority value for each battery pack of the
plurality of battery packs 102-1, 102-2, 102-3… 102-N based on the charge imbalance value
associated with at least one other battery pack of the plurality of battery packs 102-1, 102-2, 102-
10 3… 102-N. For example, the processor 202 compares the charge imbalance value of two or more
battery packs to determine the charging priority value for each of those battery packs. In an
embodiment, a battery pack with highest charge imbalance value is determined based on
comparing the charge imbalance value associated with each battery pack of the plurality of battery
packs 102-1, 102-2, 102-3… 102-N with at least one other battery pack of the plurality of battery
15 packs 102-1, 102-2, 102-3… 102-N. More specifically, the charge imbalance value associated with
each battery pack (e.g., 102-1) of the plurality of battery packs 102-1, 102-2, 102-3… 102-N is
compared with charge imbalance values associated with the other battery packs 102-1, 102-2, 102-
3… 102-N to determine highest priority. In an example, the charge imbalance value VCimb_102-1 of
battery pack 102-1 is compared with the charge imbalance value VCimb_102-2 of battery pack 102-2
20 to determine the battery pack with the highest priority. Thereafter, the charging priority value is
assigned to each battery pack based on the comparison. Assignment of such charging priority value
based on charge imbalance value of each of the plurality of battery packs 102-1, 102-2, 102-3…
102-N ensure a battery pack with higher charge imbalance is prioritized for charging which results
in more time for balancing the charges between the cells of the corresponding battery pack.
25
[040] In an example, charging priority value assigned to the plurality of battery packs 102-1, 102-
2, 102-3, 102-4 are 2, 4, 3, 1, respectively. More specifically, the battery pack 102-4 is assigned
the highest charging priority value, as the battery pack 102-4 has the highest charge imbalance
value of 165mV and the battery pack 102-2 is assigned the lowest charging priority value of 4 due
30 to a lower charge imbalance i.e., 65mV. It shall be noted that the charging priority value described
15
in the above example is for exemplary purposes and the charging priority values assigned may be
different from those described herein as long as they indicate the priority to the control unit 150.
[041] In another embodiment, the processor 202 is configured to compare the charge imbalance
5 value associated with each battery pack of the plurality of battery packs 102-1, 102-2, 102-3…
102-N with at least one threshold value. More specifically, each battery pack is compared with
only a select set of battery packs to determine charging priority value. As such, the processor 202
is configured to classify each battery pack of the plurality of battery packs 102-1, 102-2, 102-3…
102-N into one or more categories based on the comparing of the charge imbalance values of the
10 plurality of battery packs 102-1, 102-2, 102-3… 102-N with the threshold value. In an example, if
there are two threshold values, for example, T1>100 mV and 150mV>T2>100 mV, then the
plurality of battery packs are classified into two different categories (e.g., C1, C2) based on the
threshold values T1 and T2. For example, battery packs with charge imbalance values less than
100mV are classified into category C1 and battery packs with charge imbalance value between
15 100mV and 150 mV are classified into category C2. For example, if battery packs 102-1, 102-2,
102-3, 102-4 have charge imbalance values of 160mV, 75mV, 92mV and 165mV, respectively.
When the battery packs 102-1, 102-2, 102-3, 102-4 are compared with threshold values T1 and T2,
then battery packs 102-1, 102-4 are classified in category C2 and battery packs 102-2, 102-3 are
classified in category C1. Thereafter, the processor 202 is configured to determine a battery pack
20 with highest charge imbalance in each category of the one or more categories based on comparing
the charge imbalance value of each battery pack with the at least one other battery pack. More
specifically, charge imbalance value of a battery pack in a category (e.g., category C1) is compared
with charge imbalance value of one other battery pack in the same category C1 to determine the
battery pack with highest charge imbalance value. For example, charge imbalance values
25 associated with the battery packs 102-1, 102-4 may be 160mV and 165mV. The charge imbalance
value of the battery pack 102-1 is compared with the charge imbalance value of the battery pack
102-2 (i.e., the at least one other battery pack) in the same category to determine the battery pack
with highest charge imbalance, for example, battery pack 102-4 has highest charge imbalance
when compared with the battery pack 102-1. In a similar manner, the battery packs 102-1, 102-4
30 in a category (e.g., C1) may be compared with other battery packs in the same category to determine
the charging priority value for the battery packs 102-1, 102-4 in that category C1.
16
[042] Further, based on comparison, the charging priority value is assigned to each battery pack.
For example, battery pack 102-4 is assigned charging priority value of 1 and battery pack 102-1 is
assigned a charging priority value of 2. Further, the charging priority assignment policies define
5 priorities for different categories also and as such, battery packs in one category may be prioritized
over the battery packs in the other category such that battery packs with high charge imbalance are
prioritized over battery packs with lower charge imbalance. For example, battery packs 102-1,
102-4 in category C1 are prioritized over battery packs 102-2, 102-3 in category C2. Such
categorization optimizes determining of the charging priority value for each battery pack by
10 reducing the number of computations (i.e., comparisons) as charge imbalance values of battery
packs within a category alone are compared. Moreover, this ensures battery packs with high charge
imbalance are prioritized to provide more time to perform cell balancing.
[043] In an example, the charging priority value assigned to the battery packs 102-1, 102-4 in
15 category C1 are 2a, 1a, respectively, and the charging priority value assigned to the battery packs
102-2, 102-3 in category C2 are 2b, 1b, respectively. More specifically, the battery pack 102-4 is
assigned the highest charging priority value in the category C1 and the battery pack 102-3 is
assigned the highest priority in category C2.
20 [044] It shall be noted that techniques described herein for determining the charging priority
values for the plurality of battery packs 102-1, 102-2, 102-3… 102-N are for exemplary purposes
and the charging priority value for each of the battery packs may use any method to sort the
plurality of battery packs 102-1, 102-2, 102-3… 102-N based on the charge imbalance value. More
specifically, the battery packs with higher charge imbalance value are prioritized over battery
25 packs with lower charge imbalance value. In general, the charging priority value is determined
such that the most unbalanced battery pack of the plurality of battery packs 102-1, 102-2, 102-3…
102-N is provided a maximum balancing time and hence is prioritized by assigning a higher
priority value as the charging priority value.
30 [045] In an embodiment, the processor 202 is configured to selectively control charging of one
or more battery packs of the plurality of battery packs 102-1, 102-2, 102-3, 102-4 based on the
17
charging priority value associated with the one or more battery packs. In an example, the category
C1 has a higher priority over category C2, hence the battery packs in the category C1 are prioritized
for charging. For example, the battery packs are charged in order: 102-4, 102-1, 102-3, and 102-
2. In another example, battery packs 102-1 and 102-4 may be prioritized and charged at the same
5 time and then the battery packs 102-3 and 102-2 may be charged. It shall be noted that the selective
charging of battery packs based on the charging priority values described in the above examples
are for exemplary purposes and the selective charging may be performed in any different way
based on the charging priority as defined in the charging policies.
10 [046] In an embodiment, the processor 202 is configured to generate a first control signal for
operating one or more switches associated with corresponding one or more battery packs of the
plurality of battery packs 102-1, 102-2, 102-3, 102-4. In an example, if the battery pack 102-4 is
assigned the highest charging priority value, then the first control signal SC1 operates the switch
106-4 associated with the battery pack to initiate charging of the battery pack 102-4. More
15 specifically, the first control signal SC1 powers ON the switch 106-4 such that the source 130 is
connected to the battery pack 102-4 for charging on priority. In general, the first control signal SC1
isolates the charging of the most unbalanced battery pack 102-4 from the rest of the battery packs
102-1, 102-2, 102-3… 102-N by operating the switch 110-1 which initiates charging of the battery
pack 102-4 by the source 130 for a predefined time duration. In another example, if the battery
20 packs 102-4, 102-1 are assigned the highest charging priority value, for example, two most
imbalanced battery packs, then the first control signal SC1 operates the switches 106-4, 106-1
associated with the battery packs 102-4, 102-1, respectively, to initiate charging of the battery
packs 102-4, 102-1. More specifically, the first control signal SC1 powers ON the switches 106-4,
and 106-1 such that the source 130 is connected to the battery packs 102-4, 102-1 for charging on
25 priority.
[047] In an embodiment, simultaneously or subsequently, the processor 202 is configured to
generate a first charge control signal SCC1 for controlling the source 130 which is adapted to charge
the one or more battery packs at a first rate R1. More specifically, the one or more battery packs
30 are charged at a high C-rate, for a predefined time duration TC till a predefined balancing window
Tb. The term ‘predefined balancing window’ as used herein refers to a time period provided to a
18
battery pack such as, the battery pack 102-4 (charged with higher priority compared to other battery
packs 102-1, 102-2, 102-3) to perform passive balancing. More specifically, the time period in
which a relatively low current from a current limiting circuit corresponding to the battery pack is
used to drain a small amount of energy from cells with high voltage values (or high SoC cells) so
5 that the plurality of cells in the battery pack charge to their maximum voltage values (or SoC) is
referred to as the predefined balancing window Tb. It shall be noted that the predefined balancing
window is different for each of the plurality of battery packs 102-1, 102-2, 102-3, 102-4 and this
is determined based on the charging priority value. In general, the battery pack with highest
charging priority value will have highest predefined balancing window Tb for balancing charges
10 between the plurality of cells in the battery pack as it has the highest charge imbalance value. In
an example, the battery pack 102-4 has the highest charge imbalance value and hence is assigned
the highest charge priority value of ‘1’, hence, the plurality of cells 104-1, 104-2, 104-3, …, 104-
N in the battery pack 102-4 are charged initially for the predefined time period of TC and then
provided a maximum predefined balancing window Tb which continues till charging of the battery
15 pack with least charge priority value is completed. The passive balancing between the plurality of
cells in the battery pack may be accomplished by using a switch and a bleed resistor (not shown
in FIGS) in parallel with each cell of the plurality of cells in the battery pack. This limits the
charging current for the battery pack and provides maximum balancing time (i.e., the predefined
balancing window) for the most imbalanced battery pack. It shall be noted that components used
20 for passive balancing i.e., the switch and the bleed resistor with the battery pack, are not depicted
herein and techniques/architectures known in the art to achieve passive balancing may be
employed.
[048] In an example, when the switch 106-4 is operated to charge the battery pack 102-4, the
25 source 130 is controlled to charge the battery pack 102-4 for the predefined time duration Tc. In an
embodiment, after the predetermined time duration Tc, a second control signal SC2 is generated for
operating the switch 106-4 to an open position and a current limiting circuit 108-4 associated with
the one or more battery packs (e.g., battery pack 102-4) after the predefined time duration Tc. The
current limiting circuit is powered ON for the predefined balancing window Tb. More specifically,
30 the second control signal Sc2 opens the switch 106-4 to disconnect the battery pack 102-4 from the
source 130. In an example, the current limiting circuit 108-4 is powered ON and limits charging
19
current for the battery pack 102-4. In other words, the current limiting circuit (e.g., 108-4)
corresponding to the battery pack (e.g., 102-4) that was charged for the predefined time period Tc
is powered ON by the second control signal Sc2 for a predefined balancing window Tb. The plurality
of cells 104-1, 104-2, 104-3, …., 104-N perform passive balancing by bleeding off (i.e., dissipate
5 power in the bleeder resistor) so that charging of the battery pack can continue until the plurality
of cells 104-1, 104-2, 104-3, …., 104-N in the battery pack are fully charged. More specifically,
during the predefined balancing window Tb, balancing between cells 104-1, 104-2, 104-3, ….,
104-N is performed to provide maximum balancing duration for the battery pack with the highest
charge imbalance on priority. The remaining charging current goes to the next or second most
10 imbalanced cell corresponding to the imbalance, and similar logic is implemented for remaining
battery packs (i.e., battery packs 102-1, 102-2, 102-3) based on their charging priority value. The
charging is completed when the battery pack with least charging priority value is fully charged.
[049] In general, the processor 202 is configured to selectively charge remaining battery packs
15 of the energy storage device 110 based on the charging priority value i.e., starting from next battery
pack with most charge imbalance value after 102-4. The charging of the energy storage device 110
is completed when the least imbalanced battery pack (i.e, the battery pack with the least charge
imbalance between the cells 104-1, 104-2, …, 104-N), for example, battery pack 102-2, as per the
charging priority value is completely charged and thus, the balancing of the plurality of the battery
20 packs 102-1, 102-2, 102-3… 102-N stops when either the cell voltage difference is reduced to
about a predefined equal level of a minimum cell voltage or when the charging cycle for the energy
storage device 110 completes. An example of a method for balancing battery packs 102-1, 102-2,
102-3… 102-N in an energy storage device 110 is described next with reference to FIG. 3.
25 [050] FIG. 3 is a flowchart illustrating a method 300 for balancing battery packs in an energy
storage device 110, in accordance with an embodiment of the present disclosure. The
method 300 depicted in the flow diagram may be executed by, for example, the control unit 150
shown in FIG. 3. Operations of the flow diagram, and combination of operations in the flow
diagram, may be implemented by, for example, hardware, firmware, a processor, circuitry and/or
30 a different device associated with the execution of software that includes one or more computer
program instructions. The operations of the method 300 are described herein with help of the
20
processor 202 of the control unit 150. It is noted that the operations of the method 300 can be
described and/or practiced by using one or more processors of a system/device other than the
processor 202. The method 300 starts at operation 302.
5 [051] At operation 302 of the method 300, charge information of the plurality of battery packs
102-1, 102-2, 102-3, 102-4 connected in parallel in the energy storage device 110 is received by a
control unit, such as, the control unit 150 shown and explained with reference to FIG. 2. As already
explained, the control unit 150 may be embodied within a control system such as, a relay, capable
of controlling the operations of an industrial process in which the energy storage device 110 is
10 used. In another embodiment, the control unit 150 is embodied with the Battery Management
System (BMS) controlling the energy storage device 110 or maybe configured as a standalone
processor configured to perform one or more of the operations described herein. In an embodiment,
the charge information includes one of: a State of Charge (SoC) of each cell of the plurality of
cells 104-1, 104-2, 104-3,….104-N in each battery pack of the plurality of battery packs 102-1,
15 102-2, 102-3… 102-N and a voltage value of each cell of a plurality of cells 104-1, 104-2, 104-
3,….104-N in each battery pack of the plurality of battery packs 102-1, 102-2, 102-3… 102-N.
[052] At operation 304 of the method 300, a charge imbalance value for each battery pack of the
plurality of battery packs 102-1, 102-2, 102-3, 102-4 is determined based on the charge
20 information of the corresponding battery pack. In an embodiment, a maximum voltage value Vmax
and a minimum voltage value Vmin are determined from voltage values associated with the plurality
of cells 104-1, 104-2, 104-3,….104-N in a corresponding battery pack. In an embodiment, the
charge imbalance value VCimb is determined for the corresponding battery pack based on the
maximum voltage value and the minimum voltage value i.e., VCimb = Vmax - Vmin. Determining the
25 charge imbalance value for each battery pack in the energy storage device 110 is explained in
detail with examples with reference to FIG. 2 and is not explained herein for the sake of brevity.
[053] At operation 306 of the method 300, a charging priority value for each battery pack of the
plurality of battery packs 102-1, 102-2, 102-3, 102-4 is determined based on the charge imbalance
30 value associated with at least one other battery pack of the plurality of battery packs 102-1, 102-
2, 102-3, 102-4. In an embodiment, charge imbalance value of each battery pack may be compared
21
with charge imbalance values of all other battery packs in the energy storage device 110 to
determine the charging priority value. In another embodiment, the plurality of battery packs 102-
1, 102-2, 102-3… 102-N may be classified into one or more categories based on at least one
threshold value and charging priority value may be determined for the one or more battery packs
5 in each of these categories.
[054] At operation 308 of the method 300, charging of one or more battery packs of the plurality
of battery packs 102-1, 102-2, 102-3, 102-4 is selectively controlled based on the charging priority
value associated with the one or more battery packs. Selectively controlling the charging of the
10 one or more battery packs based on the charging priority value is explained with reference to FIG.
2 and is not explained herein for the sake if brevity.
[055] The sequence of operations of the methods 300 need not be necessarily executed in the
same order as they are presented. Further, one or more operations may be grouped together and
15 performed in form of a single step, or one operation may have several sub-steps that may be
performed in parallel or in sequential manner.
[056] The disclosed method with reference to FIG. 3, or one or more operations of the flow
diagram 300 may be implemented using software including computer-executable instructions
20 stored on one or more computer-readable media (e.g., non-transitory computer-readable media,
such as one or more optical media discs, volatile memory components (e.g., DRAM or SRAM),
or non-volatile memory or storage components (e.g., hard drives or solid-state non-volatile
memory components, such as Flash memory components) and executed on a computer (e.g., any
suitable computer, such as a laptop computer, net book, Web book, tablet computing device, smart
25 phone, or other mobile computing device). Such software may be executed, for example, on a
single local computer.
[057] Various embodiments of the present disclosure provide numerous advantages.
Embodiments of the present disclosure provide a system, a control unit and a method for
30 prioritizing charging of battery packs in an energy storage device. More specifically, charge
imbalance value determined for each battery pack of the plurality of battery packs may be used to
22
prioritize the plurality of battery packs for charging and balancing. Such prioritization of battery
packs for charging based on the charge imbalance value ensure target battery pack based balancing
between the plurality of cells in the battery pack. During said target battery pack based cell
balancing, the balancing time of the battery pack with most imbalanced cell is substantially
5 increased without any change in the overall battery charging time. In general, the most imbalanced
cell gets the most balancing time, and the least imbalanced cell gets the least balancing time. Such
improved passive balancing mechanism employed in each battery pack of the energy storage
device 110 prevent deviation in charging the plurality of cells that may occur due to the
overcharging or the over discharging of a specific cell or a specific battery pack. And hence, this
10 enhances the performance of the energy storage device 110, and increases the lifespan of the
energy storage device 110.
[058] It will be understood by those within the art that, in general, terms used herein, and are
generally intended as “open” terms (e.g., the term “including” should be interpreted as “including
15 but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes”
should be interpreted as “includes but is not limited to,” etc.). For example, as an aid to
understanding, the detail description may contain usage of the introductory phrases “at least one”
and “one or more” to introduce recitations. However, the use of such phrases should not be
construed to imply that the introduction of a recitation by the indefinite articles “a” or “an” limits
20 any particular part of description containing such introduced recitation to inventions containing
only one such recitation, even when the introductory phrases “one or more” or “at least one” and
indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean
“at least one” or “one or more”) are included in the recitations; the same holds true for the use of
definite articles used to introduce such recitations. In addition, even if a specific part of the
25 introduced description recitation is explicitly recited, those skilled in the art will recognize that
such recitation should typically be interpreted to mean at least the recited number (e.g., the bare
recitation of “two recitations,” without other modifiers, typically means at least two recitations or
two or more recitations).
30 [059] While various aspects and embodiments have been disclosed herein, other aspects and
embodiments will be apparent to those skilled in the art. The various aspects and embodiments
23
disclosed herein are for purposes of illustration and are not intended to be limiting, with the true
scope and spirit being indicated by the following detailed description
5
24
We claim:
1. A method of for prioritizing charging of battery packs (102-1, 102-2, 102-3, …102-N) in
an energy storage device (110), comprising:
receiving, by a control unit (150), charge information of a plurality of battery packs
5 (102-1, 102-2, 102-3, …102-N) connected in parallel in an energy storage device (110);
determining, by the control unit (150), a charge imbalance value for each battery
pack of the plurality of battery packs (102-1, 102-2, 102-3, …102-N) based on the charge
information of the corresponding battery pack;
determining, by the control unit (150), a charging priority value for each battery
10 pack of the plurality of battery packs (102-1, 102-2, 102-3, …102-N) based on the charge
imbalance value associated with at least one other battery pack of the plurality of battery
packs (102-1, 102-2, 102-3, …102-N); and
selectively controlling, by the control unit (150), charging of one or more battery
packs of the plurality of battery packs (102-1, 102-2, 102-3, …102-N) based on the charging
15 priority value associated with the one or more battery packs.

2. The method as claimed in claim 1, wherein determining the charging priority value
comprises:
comparing the charge imbalance value associated with each battery pack of the
20 plurality of battery packs (102-1, 102-2, 102-3, …102-N) with at least one threshold value;
and
classifying each battery pack of the plurality of battery packs (102-1, 102-2, 102-3,
…102-N) into one or more categories based on the comparing;
determining a battery pack with highest charge imbalance in each category of the
25 one or more categories based on comparing the charge imbalance value of each battery
pack with the at least one other battery pack; and
assigning the charging priority value based on the determining.
3. The method as claimed in claim 1, further comprising:
30 determining a battery pack with highest charge imbalance based on comparing the
charge imbalance value associated with each battery pack of the plurality of battery packs
25
(102-1, 102-2, 102-3, …102-N) with at least one other battery pack of the plurality of
battery packs (102-1, 102-2, 102-3, …102-N); and
assigning the charging priority value based on the determining.

5 4. The method as claimed in claim 1, wherein selectively controlling charging of the one or
more battery packs comprises:
generating a first control signal for operating one or more switches associated with
corresponding one or more battery packs of the plurality of battery packs (102-1, 102-2,
102-3, …102-N); and
10 generating a first charge control signal for controlling an source (130) adapted to
charge the one or more battery packs at a first rate for a predefined time duration.
5. The method as claimed in claim 4, wherein selectively controlling charging of the one or
more battery packs further comprises:
15 generating a second control signal for operating the switch (106) and a current
limiting circuit (108) associated with the one or more battery packs after the predefined
time duration, wherein the current limiting circuit is powered ON for a predefined
balancing window.
20 6. The method as claimed in claim 4, further comprising:
generating a second charge control signal after the predefined time duration for
controlling the source (130) to charge the one or more battery packs at a second rate for a
predefined balancing window.
25 7. The method as claimed in claim 1, wherein the charge information comprises one of: a State
of Charge (SoC) of each cell of a plurality of cells (104-1, 104-2, 104-3, …, 104-N) in each
battery pack of the plurality of battery packs (102-1, 102-2, 102-3, …102-N) and a voltage
value of each cell of the plurality of cells (104-1, 104-2, 104-3, …, 104-N) in each battery
pack of the plurality of battery packs (102-1, 102-2, 102-3, …102-N).
30
26
8. The method as claimed in claim 1, wherein determining the charge imbalance value for each
battery pack comprises:
determining a maximum voltage value and a minimum voltage value from voltage
values associated with a plurality of cells (104-1, 104-2, 104-3, …, 104-N) in a
5 corresponding battery pack; and
determining the charge imbalance value for the corresponding battery pack based
on the maximum voltage value and the minimum voltage value.

9. The method as claimed in claim 1, wherein determining the charge imbalance value for each
10 battery pack comprises:
determining a maximum State of Charge (SoC) and a minimum SoC from SOCs
associated with a plurality of cells (104-1, 104-2, 104-3, …, 104-N) in a corresponding
battery pack; and
determining the charge imbalance value for each battery pack based on the
15 maximum SoC and the minimum SoC.
10. A control (150) unit for prioritizing charging of battery packs (102-1, 102-2, 102-3, …102-
N) in an energy storage device (110), comprising:
a memory (204) configured to store instructions (205); and
20 a processor (202) configured to execute the instructions (205) stored in the memory
(204) and thereby cause the processor (202) to:
receive charge information of a plurality of battery packs (102-1, 102-2, 102-3,
…102-N) connected in parallel in an energy storage device (110);
determine a charge imbalance value for each battery pack of the plurality of
25 battery packs (102-1, 102-2, 102-3, …102-N) based on the charge information of the
corresponding battery pack;
determine a charging priority value for each battery pack of the plurality of
battery packs (102-1, 102-2, 102-3, …102-N) based on the charge imbalance value
associated with at least one other battery pack of the plurality of battery packs (102-1,
30 102-2, 102-3, …102-N); and
27
selectively control charging of one or more battery packs of the plurality of battery
packs (102-1, 102-2, 102-3, …102-N) based on the charging priority value associated
with each battery pack of the plurality of battery packs (102-1, 102-2, 102-3, …102-N).
5 11. The control unit (150) as claimed in claim 10, wherein for determining the charging priority
value, the processor (202) is configured to:
compare the charge imbalance value associated with each battery pack of the
plurality of battery packs (102-1, 102-2, 102-3, …102-N) with at least one threshold value;
and
10 classify each battery pack of the plurality of battery packs (102-1, 102-2, 102-3,
…102-N) into one or more categories based on the comparing;
determine a battery pack with highest charge imbalance in each category of the one
or more categories based on comparing the charge imbalance value of each battery pack
with the at least one other battery pack; and
15 assign the charging priority value based on the determining.
12. The control unit (150) as claimed in claim 10, wherein the processor (202) is configured to:
determine a battery pack with highest charge imbalance based on comparing the
charge imbalance value associated with each battery pack of the plurality of battery packs
20 (102-1, 102-2, 102-3, …102-N) with at least one other battery pack of the plurality of
battery packs (102-1, 102-2, 102-3, …102-N); and
assign the charging priority value based on the determining.

13. The control unit (150) as claimed in claim 10, wherein for selectively controlling charging
25 of the one or more battery packs, the processor (202) is configured to:
generate a first control signal for operating a switch (106) associated with the one
or more battery packs of the plurality of battery packs (102-1, 102-2, 102-3, …102-N); and
generate a first charge control signal for controlling an source (130) adapted to
charge the one or more battery packs at a first rate for a predefined time duration.
30
28
14. The control unit (150) as claimed in claim 13, wherein the processor (202) is further
configured to:
generate a second control signal for operating the switch (106) and a current
limiting circuit (108) associated with the one or more battery packs after the predefined
5 time duration, wherein the current limiting circuit (108) is powered ON for a predefined
balancing window.
15. The control unit (150) as claimed in claim 13, wherein for selectively controlling charging
of the one or more battery packs, the processor (202) is further configured to:
10 generate a second charge control signal after the predefined time duration for
controlling the source to charge the one or more battery packs at a second rate for a
predefined balancing window.
16. The control unit a(150) s claimed in claim 10, wherein the charge information comprises
15 one of: a State of Charge (SoC) of each cell of a plurality of cells (104-1, 104-2, 104-3,
…104-N) in each battery pack of the plurality of battery packs (102-1, 102-2, 102-3, …102-
N) and a voltage value of each cell of the plurality of cells (104-1, 104-2, 104-3, …104-N)
in each battery pack of the plurality of battery packs (102-1, 102-2, 102-3, …102-N).
20 17. The control unit (150) as claimed in claim 10, wherein for determining the charge imbalance
value for each battery pack, the processor (202) is configured to:
determine a maximum voltage value and a minimum voltage value from voltage
values associated with a plurality of cells (104-1, 104-2, 104-3, …104-N) in a
corresponding battery pack; and
25 determine the charge imbalance value for the corresponding battery pack based on
the maximum voltage value and the minimum voltage value.

18. The control unit (150) as claimed in claim 10, wherein for determining the charge imbalance
value for each battery pack, the processor (202) is configured to:
29
determine a maximum State of Charge (SoC) and a minimum SoC from SOCs
associated with a plurality of cells (104-1, 104-2, 104-3, …104-N) in a corresponding
battery pack; and
determine the charge imbalance value for each battery pack based on the maximum
5 SoC and the minimum SoC.

19. A system (100) for prioritizing charging of battery packs (102-1, 102-2, 102-3, …102-N)
in an energy storage device (110), comprising:
a plurality of battery packs (102-1, 102-2, …102-N) connected in parallel;
10 a plurality of switches (106-1, 106-2, …106-N), wherein each switch of the
plurality of switches is connected in series with a corresponding battery pack of the
plurality of battery packs (102-1, 102-2, 102-3, …102-N);
a plurality of current limiting circuits (108-1, 108-2 …108-N), wherein each current
limiting circuit of the plurality of current limiting circuits (108-1, 108-2 …108-N) is
15 connected in parallel to a corresponding switch; and
a control unit (150) electrically coupled to the plurality of switches (106-1, 106-2,
…106-N) and the plurality of current limiting circuits (108-1, 108-2 …108-N), wherein
the control unit (150) is configured to:
receive charge information of the plurality of battery packs (102-1, 102-2,
20 …102-N);
determine a charge imbalance value for each battery pack of the plurality of
battery packs (102-1, 102-2, …102-N) based on the charge information of the
corresponding battery pack;
determine a charging priority value for each battery pack of the plurality of
25 battery packs (102-1, 102-2, …102-N) based on the charge imbalance value
associated with at least one other battery pack of the plurality of battery packs (102-
1, 102-2, …102-N); and
selectively control charging of one or more battery packs of the plurality of
battery packs (102-1, 102-2, …102-N) based on the charging priority value
30 associated with each battery pack of the plurality of battery packs (102-1, 102-2,
30
…102-N) using the corresponding one or more switches of the plurality of switches
(106-1, 106-2, …106-N).
20. The system (100) as claimed in claim 19, wherein for determining the charging priority
5 value, the control unit (150) is configured to:
compare the charge imbalance value associated with each battery pack of the
plurality of battery packs (102-1, 102-2, …102-N) with at least one threshold value; and
classify each battery pack of the plurality of battery packs (102-1, 102-2, …102-N)
into one or more categories based on the comparing;
10 determine a battery pack with highest charge imbalance in each category of the one
or more categories based on comparing the charge imbalance value of each battery pack
with the at least one other battery pack; and
assign the charging priority value based on the determining.
15 21. The system (100) as claimed in claim 19, wherein the control unit (150) is configured to:
determine a battery pack with highest charge imbalance based on comparing the
charge imbalance value associated with each battery pack of the plurality of battery packs
(102-1, 102-2, …102-N) with at least one other battery pack of the plurality of battery
packs (102-1, 102-2, …102-N); and
20 assign the charging priority value based on the determining.

22. The system (100) as claimed in claim 19, wherein for selectively controlling charging of
the one or more battery packs, the control unit (150) is configured to:
generate a first control signal for operating one or more switches associated with
25 corresponding one or more battery packs of the plurality of battery packs (102-1, 102-2,
…102-N); and
generate a first charge control signal for controlling an source (130) adapted to
charge the one or more battery packs at a first rate for a predefined time duration.
30 23. The system (100) as claimed in claim 22, wherein for selectively controlling charging of
the one or more battery packs, the control unit (150) is configured to:
31
generate a second control signal for operating the one or more switches and
corresponding one or more current limiting circuits associated with the one or more battery
packs after the predefined time duration, wherein the one or more current limiting circuits
are powered ON for a predefined balancing window.
5
24. The system (100) as claimed in claim 22, wherein the control unit (105) is further configured
to:
generate a second charge control signal after the predefined time duration for
controlling the source (130) to charge the one or more battery packs at a second rate for a
10 predefined balancing window.
25. The system (100) as claimed in claim 19, wherein the charge information comprises one of:
a State of Charge (SoC) of each cell of a plurality of cells (104-1, 104-2, …104-N) in each
battery pack of the plurality of battery packs (102-1, 102-2, …102-N) and a voltage value
15 of each cell of the plurality of cells (104-1, 104-2, …104-N) in each battery pack of the
plurality of battery packs (102-1, 102-2, …102-N).
26. The system (100) as claimed in claim 19, wherein for determining the charge imbalance
value for each battery pack, the control unit (150) is configured to:
20 determine a maximum voltage value and a minimum voltage value from voltage
values associated with a plurality of cells (104-1, 104-2, …104-N) in a corresponding
battery pack; and
determine the charge imbalance value for the corresponding battery pack based on
the maximum voltage value and the minimum voltage value.
25
27. The system (100) as claimed in claim 19, wherein for determining the charge imbalance
value for each battery pack, the control unit (150) is configured to:
determine a maximum State of Charge (SoC) and a minimum SoC from SOCs
associated with a plurality of cells (104-1, 104-2, …104-N) in a corresponding battery
30 pack; and
32
determine the charge imbalance value for each battery pack based on the maximum
SoC and the minimum SoC.
Dated this 28th day of March, 2023
5
R. Ramya Rao
OF K&S PARTNERS
AGENT FOR THE APPLICANT(S)
IN/PA-1607
10 Digitally signed and filed through e-filing
15

33
SYSTEM, CONTROL UNIT AND METHOD FOR PRIORITIZING CHARGING OF
BATTERY PACKS IN ENERGY STORAGE DEVICES
ABSTRACT
5
Embodiment of the present disclosure disclose a system (100), a control unit and an operating
method thereof. The method includes receiving, by a control unit (150), charge information of a
plurality of battery packs (102-1, 102-2, …102-N) connected in parallel in an energy storage
device (110). The method includes determining a charge imbalance value for each battery pack of
10 the plurality of battery packs (102-1, 102-2, …102-N) based on the charge information of the
corresponding battery pack. The method includes determining a charging priority value for each
battery pack of the plurality of battery packs (102-1, 102-2, …102-N) based on the charge
imbalance value associated with at least one other battery pack. The method includes selectively
controlling charging of one or more battery packs of the plurality of battery packs (102-1, 102-2,
15 …102-N) based on the charging priority value associated with the one or more battery packs.
To be published with abstract : FIG. 1A