Description:FIELD OF THE INVENTION
[001] The present invention relates to an energy storage unit. More particularly, the present invention relates to a system and method for charging a secondary energy storage unit.

BACKGROUND OF THE INVENTION
[002] Conventional vehicle design relies on a single high-voltage battery pack that plays a dual role of driving an electric motor for propulsion of a vehicle and supplying electrical energy to various auxiliary systems such as lights, control units, and onboard electronics. Recent advancements have led to development of vehicles incorporating two distinct battery types: a primary battery with a higher voltage for providing substantial electric power required for traction purposes of the vehicle and an auxiliary battery with a lower voltage for ancillary operations pertaining to auxiliary systems of the vehicles such as powering lighting units, an instrument cluster, or any other function not directly linked to propulsion of the vehicle. Further, the primary battery also charges the auxiliary battery. This approach allows for the efficient use of both battery types, ensuring that the primary battery is dedicated to propelling the vehicle and charging the auxiliary battery, while the auxiliary battery is allocated to power other auxiliary vehicle systems having critical function.
[003] However, in some known arts, the primary battery is directly connected to the auxiliary battery which leads to continuous power drainage from the primary battery. Additionally, there are chances of overvoltage or over heating being developed in the auxiliary battery. Further these conventional systems fail to address instance of charging the auxiliary battery when multiple primary battery packs are present. In vehicles employing multiple primary battery packs for propulsion, during discharge they do not discharge at the same rate resulting in an inherent charge imbalance. The reason for unequal discharge rates and unequal State of Charge (SOC) is due to, but not limited to, varying wire length, temperature at which each of the primary battery pack is operating at and internal resistance attributed to each primary battery pack. Additionally, when multiple primary battery packs of higher voltage are present in the vehicle, a designated primary battery pack charges the auxiliary battery pack leading to a higher deterioration rate of the designated primary battery pack. Further, this also leads to occurrences of charge imbalances among the multiple primary battery packs which is an undesirable outcome. Owing to occurrence of charge imbalance in the primary battery pack, the primary battery pack is damaged which negatively affects durability and reliability of the battery packs as well as increase the serviceability/maintainability costs associated with the battery pack. Moreover, this also leads to inefficient charging and degradation of the auxiliary battery pack. Consequently, the degradation of the primary battery packs adversely impacts vehicle performance in terms of traction characteristics as well as overheating of the ancillary components owing to mandated connection between the auxiliary battery pack and the designated primary battery pack.
[004] Thus, there is a need in the art for a system and method for charging a secondary energy storage unit which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[005] In one aspect, the present invention relates to a system for charging a secondary energy storage unit. The system has a plurality of primary energy storage units, the secondary energy storage unit and a control unit. The secondary energy storage unit is configured to be charged by at least one of the plurality of the primary energy storage units. The control unit is coupled to the plurality of primary energy storage units and the secondary energy storage unit. The control unit is configured to receive a first set of parameters for each of the plurality of primary energy storage units and a second set of parameters for the secondary storage unit. The control unit is further configured to determine whether the secondary energy storage unit is to be charged based on satisfaction of a first set of pre-defined conditions. Based on satisfaction of a second set of pre-defined conditions, the control unit is further configured to select at least one primary energy storage unit from the plurality of primary energy storage units to charge the secondary energy storage unit and instruct the selected at least one primary energy storage unit to charge the secondary energy storage unit.
[006] In an embodiment of the invention, the control unit is configured to compare, based on said determination, the first set of parameters of each of the plurality of primary energy storage units.
[007] In a further embodiment of the invention, the first set of parameters include at least one of: operating voltage, operating current, operating power, State of Charge (SoC), State of Health (SoH), temperature and rate of discharge.
[008] In a further embodiment of the invention, the second set of parameters include at least one of: State of Charge (SoC) and rate of change of temperature.
[009] In a further embodiment of the invention, the first set of pre-defined conditions comprises at least one of: the State of Charge of the secondary energy storage unit being less than a pre-defined State of Charge (SoC); and the rate of change of temperature of the secondary energy storage unit being less than a pre-defined rate of change of temperature.
[010] In a further embodiment of the invention, the second set of pre-defined conditions comprises at least one of: the selected at least one of primary energy storage unit having maximum value of State of Charge (SoC) among the plurality of primary energy storage units, the selected at least one of primary energy storage unit having maximum value of State of Health (SoH) among the plurality of primary energy storage units, the selected at least one of primary energy storage unit having minimum value of temperature among the plurality of primary energy storage units, and the selected at least one of primary energy storage unit having minimum value of rate of discharge among the plurality of primary energy storage units.
[011] In a further embodiment of the invention, the plurality of primary energy storage units having higher voltage than the secondary energy storage unit being connected to each other via a converter configured to step-down the voltage of the plurality of primary energy storage unit to allow charging of the secondary energy storage unit.
[012] In a further embodiment of the invention, each of the primary energy storage units has a switch operative by the control unit, the switch configured to control the charging operation from the selected at least one primary energy storage unit to the secondary energy storage unit. Herein, the control of the charging operation comprises in an ON state of switch, the selected at least one primary energy storage unit charges the secondary energy storage unit and, in an OFF state of switch, the selected at least one primary energy storage unit stops charging of the secondary energy storage unit.
[013] In a further embodiment of the invention, the plurality of primary energy storage units selected to charge the secondary energy storage unit are connected in one of parallel configuration and series configuration. Herein, the configuration being determined by the control unit based on satisfaction of the second set of pre-defined conditions.
[014] In another aspect, the present invention relates to a method for charging a secondary energy storage unit by at least one of a plurality of the primary energy storage units in a vehicle. The method comprises a step of receiving, by a control unit, a first set of parameters for each of the plurality of primary energy storage units. The method further comprises a step of receiving, by the control unit, a second set of parameters for the secondary energy storage unit. Based on satisfaction of a first set of pre-defined conditions, the method further comprises determining, by the control unit, whether the secondary energy storage unit is to be charged. Based on satisfaction of a second set of pre-defined conditions, the method further comprises selecting, by the control unit, at least one primary energy storage unit from the plurality of primary energy storage units to charge the secondary energy storage unit and instructing, by the control unit, the selected at least one primary energy storage unit to charge the secondary energy storage unit.
[015] In an embodiment of the invention, the method further comprises the step of comparing, by the control unit, based on the step of determination, the first set of parameters of each of the plurality of primary energy storage units.
[016] In a further embodiment of the invention, the first set of parameters include at least one of: operating voltage, operating current, operating power, State of Charge (SoC), State of Health (SoH), temperature and rate of discharge.
[017] In a further embodiment of the invention, the second set of parameters include at least one of: State of Charge (SoC) and rate of change of temperature.
[018] In a further embodiment of the invention, the first set of pre-defined conditions includes at least one of: the State of Charge of the secondary energy storage unit being less than a pre-defined State of Charge (SoC); and the rate of change of temperature of the secondary energy storage unit being less than a pre-defined rate of change of temperature.
[019] In a further embodiment of the invention, the second set of pre-defined conditions includes at least one of: the selected at least one of primary energy storage unit having maximum value of State of Charge (SoC) among the plurality of primary energy storage units, the selected at least one of primary energy storage unit having maximum value of State of Health (SoH) among the plurality of primary energy storage units, the selected at least one primary energy storage unit having minimum value of temperature among the plurality of primary energy storage units, and the selected at least one of primary energy storage unit having minimum value of rate of discharge among the plurality of primary energy storage units.
[020] In a further embodiment of the invention, the plurality of primary energy storage units having higher voltage than the secondary energy storage unit being connected to each other via a converter configured to step-down the voltage of the plurality of primary energy storage unit to allow charging of the secondary energy storage unit.
[021] In a further embodiment of the invention, each of the primary energy storage units has a switch operated by the control unit, the switch configured to control the charging operation from the selected at least one primary energy storage unit to the secondary energy storage unit. Herein, the control of charging operation comprises in an ON state of switch, the selected at least one primary energy storage unit charges the secondary energy storage unit and, in an OFF state of switch, the selected at least one primary energy storage unit stops charging of the secondary energy storage unit.
[022] In a further embodiment of the invention, the plurality of primary energy storage units selected to charge the secondary energy storage unit are connected in one of parallel configuration and series configuration. The configuration is determined by the control unit based on satisfaction of the second set of pre-defined conditions.

BRIEF DESCRIPTION OF THE DRAWINGS
[023] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 illustrates a system for charging a secondary energy storage unit, in accordance with an embodiment of the present invention.
Figure 2 illustrates a flowchart of a method for charging a secondary energy storage unit, in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[024] The present invention relates to an energy storage unit. More particularly, the present invention relates to a system and method for charging a secondary energy storage unit. The system and method of the present invention are typically used in a vehicle such as a two wheeled vehicle, or a three wheeled vehicle including trikes, or a four wheeled vehicle or any multi-axle vehicle as required. The vehicle is an electric vehicle, or a hybrid vehicle as required. As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered prime mover.
[025] Figure 1 illustrates a system 100 for charging a secondary energy storage unit 140 in a vehicle. The secondary energy storage unit 140 is also known as an auxiliary battery. In an embodiment, the system 100 is a part of the vehicle and is integral to the vehicle. As illustrated, the system 100 comprises a plurality of primary energy storage units 110, 112, 114. The plurality of primary energy storage units 110, 112, 114 are configured to propel the vehicle and charge the secondary energy storage unit 140. In one instance, the plurality of primary energy storage units 110 are high capacity 48V battery packs such as lithium-ion battery. In another instance, the plurality of primary energy storage units 110 is a combination of battery packs and fuel-powered engines configured to propel a vehicle. The secondary energy storage unit 140 is configured to be charged by at least one of the plurality of the primary energy storage units 110, 112, 114. In an embodiment, the secondary energy storage unit 140 is configured to provide power for ancillary vehicle operations such as, but not limited to, lighting units, controllers and an instrument cluster. In one instance, the secondary energy storage units 140 are low capacity 12V battery pack. In an embodiment, the secondary energy storage unit 140 is a lead-acid battery pack. In another embodiment, the secondary energy storage unit 140 is a lithium-ion cell-based battery pack. The system 100 further comprises a converter 130 disposed between the plurality of primary energy storage units 110, 112, 114 and the secondary energy storage unit 140. In an embodiment, the converter 130 is a DC-DC converter of the vehicle, which is configured to step-down voltage of at least one of the plurality of the primary energy storage units 110, 112, 114 to allow supply of charge to the secondary energy storage unit 140. In one instance, the converter 130 is configured to step-down the voltage of the primary energy storage unit from 48 volt to 12 volt to allow supply of charge to the secondary energy storage unit 140.
[026] As illustrated in Figure 1, the system 100 further comprises a control unit 120. In an embodiment, the control unit 120 is a Battery Management System (BMS). The BMS is an electronic system which is configured to manage the charging of the secondary energy storage unit 140 and control the secondary energy storage unit 140 to operate in safe operating temperature, monitoring the operating state in terms of state of health, State of charge, voltage, current and power, calculating temperature data, reporting the calculated temperature data, controlling environment, and/ or charge balancing the secondary energy storage unit 140. In a preferred embodiment, the control unit 120 is an EMS-ECU or a vehicle control unit. The control unit 120 is coupled to the plurality of primary energy storage units 110, 112, 114 and the secondary energy storage unit 140. Each of the primary energy storage units 110, 112, 114 comprises a switch 150, 152, 154 respectively operative by the control unit 120. The switch is configured to control the charging operation from the selected at least one primary energy storage unit to the secondary energy storage unit 140. For example, the switch 150, 152, 154 is an electronic switch, a relay switch, or an electro-mechanical switch or a power switch. Further, in an ON state of switch 150, 152, 154, the selected at least one primary energy storage unit charges the secondary energy storage unit 140. In an OFF state of switch 150, 152, 154, the selected at least one primary energy storage unit stops charging of the secondary energy storage unit 140. For example, when the primary energy storage unit 110 has 40% charge, the primary energy storage unit 112 has 60% charge and the primary energy storage unit 114 has 30% charge, the control unit switches ON switch 152 and the primary energy storage unit 112 selected to charge the secondary energy storage unit 140 is connected in series configuration. In another example, when the primary energy storage unit 112 reaches 45% charge or 40% charge (a tolerance value of +/- 5% is acceptable), the primary energy storage unit 110 has 40% charge and the primary energy storage unit 114 has 30% charge, the control unit switches ON switch 152 and switch 150 and the primary energy storage unit 112 and the primary energy storage unit 110 selected to charge the secondary energy storage unit 140 are connected in parallel configuration.
[027] The control unit 120 is configured to receive a first set of parameters for each of the plurality of primary energy storage units 110, 112, 114. The first set of parameters comprise at least one of operating voltage, operating current, operating power, State of Charge (SoC), State of Health (SoH), temperature and rate of discharge. The control unit 120 is further configured to receive a second set of parameters for the secondary energy storage unit 140. The second set of parameters comprise at least one of State of Charge (SoC) and rate of change of temperature.
[028] Subsequently, the control unit 120 is configured to determine whether the secondary energy storage unit 140 is to be charged based on satisfaction of a first set of pre-defined conditions. The first set of pre-defined conditions comprises at least one of the State of Charge (SoC) of the secondary energy storage unit 140 being less than a pre-defined State of Charge (SoC) and the rate of change of temperature of the secondary energy storage unit 140 being less than a pre-defined rate of change of temperature. In an embodiment, the control unit 120 is configured to determine the pre-defined State of Charge (SoC) based on transient current/ voltage requirements of safety critical functions over a fixed duration of time. For example, the pre-defined State of Charge (SoC) value will update dynamically over say 10 mins based on the rate of discharge of the secondary energy storage unit 140 in the past 10 mins. The control unit 120 will also check if the pre-defined State of Charge (SoC) is overshot or not every 2 mins. The dynamic updation of the pre-defined State of Charge (Soc) provides an accurate and real-time estimation of the State of Charge (SoC) of the primary energy storage units thereby ensuring reduction in charge imbalance among the plurality of primary energy storage units 110, 112, 114 and efficient charging of the secondary energy storage unit 140. In one instance, when the State of Charge (SoC) of the secondary energy storage unit 140 is below the pre-defined State of Charge (SoC), the control unit 120 subsequently determines that the secondary energy storge unit 140 is to be charged. In another instance, the control unit 120 is configured to disengage the connection to the secondary energy storage unit 140 to prevent thermal runway when the rate of change of temperature in the secondary energy storage unit 140 is greater than the pre-defined rate of change of temperature.
[029] The control unit 120 is configured to compare the first set of parameters of each of the plurality of primary energy storage units 110, 112, 114 based on the determination that the secondary energy storage unit 140 is to be charged. In an instance, the control unit compares the operating voltage, operating current, operating power, State of Charge (SoC), State of Health (SoH), temperature and rate of discharge of each of the plurality of primary energy storage units 110, 112,114. The control unit 120 is further configured to select at least one primary energy storage unit from the plurality of primary energy storage units 110, 112, 114 to charge the secondary energy storage unit 140 based on satisfaction of a second set of pre-defined conditions. The second set of pre-defined conditions comprises at least one of the selected at least one of primary energy storage unit comprising maximum value of State of Charge (SoC) among the plurality of primary energy storage units 110, 112, 114, the selected at least one of primary energy storage unit comprising maximum value of State of Health (SoH) among the plurality of primary energy storage units 110, 112, 114, the selected at least one of primary energy storage unit comprising minimum value of temperature among the plurality of primary energy storage units 110, 112, 114 and the selected at least one of primary energy storage unit comprising minimum value of rate of discharge among the plurality of primary energy storage units 110, 112, 114. The control unit 120 is configured to instruct the selected at least one primary energy storage unit to charge the secondary energy storage unit 140.
[030] In an exemplary embodiment, the control unit 120 is configured to consider each of the second set of pre-defined conditions concerning the plurality of primary energy storage units 110, 112, 114 and attribute a relative value with respect to state of charge, state of health, temperature, rate of discharge for each of the plurality of primary energy storage units 110, 112, 114. The control unit 120 processes the cumulative of the attributed relative value to determine the primary energy storage unit best suited to partake charging operation of the secondary energy storage unit 140. The disclosed configuration ensures that in the event there is grave disparity between the first set of parameters concerning the plurality of primary energy storage units 110, 112, 114, the control unit 120 can determine an optimum primary energy storage unit which is to be selected to maintain an optimal operating system 100 in the vehicle. In the next step, same processing configuration determines whether parallel charging is suitable or not. For parallel charging, the state of charge of the plurality of primary energy storage units 110, 112, 114 is critical. As already stated in preceding paragraphs, the primary energy storage units 110, 112, 114 having substantially same state of charge or same state of charge will be connected in parallel to charge the secondary energy storage unit 140. A pre-defined tolerance value of SOC may be considered for selection of the primary energy storage units during parallel charging. In one non-limiting example, the pre-defined tolerance value is +/- 5%.
[031] In an embodiment, the plurality of primary energy storage units selected to charge the secondary energy storage unit 140 are connected in one of parallel configuration or series configuration. The configuration is determined by the control unit 120 based on satisfaction of the second set of pre-defined conditions. For example, when the primary energy storage unit 110 has 40% charge, the primary energy storage unit 112 has 60% charge and the primary energy storage unit 114 has 30% charge, the primary energy storage unit 112 selected to charge the secondary energy storage unit 140 is connected in series. In another example, when the primary energy storage unit 112 reaches 45% charge or 40% charge (a tolerance value of +/- 5% is acceptable), the primary energy storage unit 110 has 40% charge and the primary energy storage unit 114 has 30% charge, the primary energy storage unit 112 and the primary energy storage unit 110 selected to charge the secondary energy storage unit 140 are connected in parallel. In another example, when the primary energy storage unit 112 reaches 30% charge, the primary energy storage unit 110 also reaches 30% charge and the primary energy storage unit 114 is at 30% charge then the primary energy storage units 110, 112, 114 selected to charge the secondary energy storage unit 140 are connected in parallel. In an embodiment, the control unit 120 is configured to switch between an Internal Combustion (IC) engine and the plurality of primary energy storage units 110, 112, 114 based on the above factors including fuel availability in the case of the hybrid vehicle. In an embodiment, when the state of charge (SoC) of the primary energy storage unit is at a minimum value, the primary energy storage unit will prioritize propulsion of the vehicle.
[032] In another aspect, the present invention provides a method 200 for charging a secondary energy storage unit 140. Figure 2 illustrates the method steps involved in the method 200 for charging the secondary energy storage unit 140 by at least one of a plurality of the primary energy storage units 110, 112, 114 in a vehicle. At step 202, the control unit 120 receives a first set of parameters for each of the plurality of primary energy storage units 110,112,114. The first set of parameters comprise at least one of operating voltage, operating current, operating power, State of Charge (SoC), State of Health (SoH), temperature and rate of discharge. At step 204, the control unit 120 receives a second set of parameters from the secondary energy storage unit 140. The second set of parameters comprise at least one of State of Charge (SoC) and rate of change of temperature.
[033] At step 206, the control unit 120 determines, based on satisfaction of a first set of pre-defined conditions, whether the secondary energy unit 140 is to be charged. The first set of pre-defined conditions comprises at least one of the State of Charge (SoC) of the secondary energy storage unit 140 being less than a pre-defined State of Charge (SoC) and the rate of change of temperature of the secondary energy storage unit 140 being less than a pre-defined rate of change of temperature. If at step 206, it is determined that the secondary energy unit 140 is to be charged, the method 200 moves to step 208, otherwise the method moves to step 204. At step 208, the control unit 120 compares, based on said determination, the first set of parameters of each of the plurality of primary energy storage units 110, 112,114. In an instance, the control unit compares the operating voltage, operating current, operating power, State of Charge (SoC), State of Health (SoH), temperature and rate of discharge of each of the plurality of primary energy storage units 110, 112,114. At step 210, the control unit 120 selects, based on satisfaction of a second set of pre-defined conditions, at least one primary energy storage unit from the plurality of primary energy storage units 110, 112, 114 to charge the secondary energy storage unit 140. The second set of pre-defined conditions comprises at least one of the selected at least one primary energy storage unit comprising maximum value of State of Charge (SoC) among the plurality of primary energy storage units 110, 112, 114, the selected at least one primary energy storage unit comprising maximum value of State of Health (SoH) among the plurality of primary energy storage units 110, 112, 114, the selected at least one primary energy storage unit comprising minimum value of temperature among the plurality of primary energy storage units 110, 112, 114 and the selected at least one primary energy storage unit comprising minimum value of rate of discharge among the plurality of primary energy storage units 110, 112, 114. At step 212, the control unit 120 instructs, the selected at least one primary energy storage unit to charge the secondary energy storage unit 140.
[034] In an exemplary embodiment, the control unit 120 is configured to consider each of the second set of pre-defined conditions concerning the plurality of primary energy storage units 110, 112, 114 and attribute a relative value with respect to state of charge, state of health, temperature, rate of discharge for each of the plurality of primary energy storage units 110, 112, 114. The control unit 120 processes the cumulative of the attributed relative value to determine the primary energy storage unit best suited to partake charging operation of the secondary energy storage unit 140. The disclosed configuration ensures that in the event there is grave disparity between the first set of parameters concerning the plurality of primary energy storage units 110, 112, 114, the control unit 120 can determine an optimum primary energy storage unit which is to be selected to maintain an optimal operating system 100 in the vehicle. In the next step, same processing configuration determines whether parallel charging is suitable or not. For parallel charging, the state of charge of the plurality of primary energy storage units 110, 112, 114 is critical. As already stated in preceding paragraphs, the primary energy storage units 110, 112, 114 having substantially same state of charge or same state of charge will be connected in parallel to charge the secondary energy storage unit 140. A pre-defined tolerance value of SOC may be considered for selection of the primary energy storage units during parallel charging. In one non-limiting example, the pre-defined tolerance value is +/- 5%.
[035] The claimed features of the present invention as discussed above are not routine, conventional, or well understood in the art, as the claimed features enable the following solutions to the existing problems in conventional technologies. Specifically, the problem of charging an auxiliary battery when multiple primary battery packs are present is solved by the present invention.
[036] The present invention provides an efficient system for charging the secondary energy storage unit using multiple primary energy storage units and reduces the charge imbalances in the multiple primary energy storage units. Further, the present invention enhances the durability and extends cycle life of both the primary and the secondary energy storage units resulting in a longer lasting and reliable energy storage system. Thus, cost associated with serviceability of the battery pack and exterior body parts in close proximity of the battery pack is also decreased.
[037] In addition, the present invention also prevents overheating of the energy storage units thereby preventing thermal runway and ensuring user safety. The present invention enhances mileage, ergonomics and utilization of the primary and secondary energy storage units. Furthermore, the system of the present invention is simple to manufacture and enables effective means to maintain cell imbalances, ensuring consistent and reliable energy distribution in the multiple primary energy storage units. The present invention ensures lower degradation of the secondary energy storage unit while efficiently charging the secondary energy storage unit.
[038] In light of the abovementioned advantages and the technical advancements provided by the disclosed system and method, the claimed steps as discussed above are not routine, conventional, or well understood in the art, as the claimed steps enable the aforementioned solutions to the existing problems in conventional technologies. Further, the claimed steps clearly bring an improvement in the functioning of the system itself as the claimed steps provide a technical solution to a technical problem.
[039] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.

List of Reference Numerals
100: System for Charging a Secondary Energy Storage Unit

110, 112, 114: Primary Energy Storage Unit

120: Control Unit

130: Converter
140: Secondary Energy Storage Unit
150, 152, 154: Switch
200: Method for Charging a Secondary Energy Storage Unit
, Claims:1. A system (100) for charging a secondary energy storage unit (140) in a vehicle, the system (100) comprising:
a plurality of primary energy storage units (110, 112, 114);
the secondary energy storage unit (140), the secondary energy storage unit (140) configured to be charged by at least one of the plurality of the primary energy storage units (110, 112, 114); and
a control unit (120), the control unit (120) coupled to the plurality of primary energy storage units (110, 112, 114) and the secondary energy storage unit (140), the control unit (120) configured to:
receive a first set of parameters for each of the plurality of primary energy storage units (110, 112, 114);
receive a second set of parameters for the secondary energy storage unit (140);
determine, based on satisfaction of a first set of pre-defined conditions, whether the secondary energy storage unit (140) is to be charged;
select, based on satisfaction of a second set of pre-defined conditions, at least one primary energy storage unit from the plurality of primary energy storage units (110, 112, 114) to charge the secondary energy storage unit (140); and
instruct the selected at least one primary energy storage unit to charge the secondary energy storage unit (140).

2. The system (100) as claimed in claim 1, wherein the control unit (120) is configured to compare, based on said determination, the first set of parameters of each of the plurality of primary energy storage units (110, 112, 114).

3. The system (100) as claimed in claim 1, wherein the first set of parameters comprise at least one of: operating voltage, operating current, operating power, State of Charge (SoC), State of Health (SoH), temperature and rate of discharge.

4. The system (100) as claimed in claim 1, wherein the second set of parameters comprise at least one of: State of Charge (SoC) and rate of change of temperature.

5. The system (100) as claimed in claim 4, wherein the first set of pre-defined conditions comprises at least one of:
the State of Charge (SoC) of the secondary energy storage unit (140) being less than a pre-defined State of Charge (SoC); and
the rate of change of temperature of the secondary energy storage unit (140) being less than a pre-defined rate of change of temperature.

6. The system (100) as claimed in claim 3, wherein the second set of pre-defined conditions comprises at least one of:
- the selected at least one of primary energy storage unit comprising maximum value of State of Charge (SoC) among the plurality of primary energy storage units (110, 112, 114);
- the selected at least one of primary energy storage unit comprising maximum value of State of Health (SoH) among the plurality of primary energy storage units (110, 112, 114);
- the selected at least one of primary energy storage unit comprising minimum value of temperature among the plurality of primary energy storage units (110, 112, 114); and
- the selected at least one of primary energy storage unit comprising minimum value of rate of discharge among the plurality of primary energy storage units (110, 112, 114).

7. The system (100) as claimed in claim 1, wherein the plurality of primary energy storage units (110, 112, 114) having higher voltage than the secondary energy storage (140) unit being connected to each other via a converter (130) configured to step-down the voltage of the plurality of primary energy storage unit (110, 112, 114) to allow charging of the secondary energy storage unit (140).

8. The system (100) as claimed in claim 1, wherein each of the primary energy storage units (110, 112,114) comprises a switch (150, 152, 154) operative by the control unit (120), the switch (150, 152, 154) configured to control the charging operation from the selected at least one primary energy storage unit to the secondary energy storage unit (140), wherein the control of the charging operation comprises in an ON state of switch (150, 152, 154), the selected at least one primary energy storage unit charges the secondary energy storage unit (140) and, in an OFF state of switch (150, 152, 154), the selected at least one primary energy storage unit stops charging of the secondary energy storage unit (140).

9. The system (100) as claimed in claim 1, wherein the plurality of primary energy storage units (110, 112, 114) selected to charge the secondary energy storage unit (140) are connected in one of parallel configuration and series configuration, wherein the configuration being determined by the control unit (120) based on satisfaction of the second set of pre-defined conditions.

10. A method (200) for charging a secondary energy storage unit (140) by at least one of a plurality of the primary energy storage units (110, 112, 114) in a vehicle, the method comprising the steps of:
receiving (202), by a control unit (120), a first set of parameters for each of the plurality of primary energy storage units (110, 112, 114);
receiving (204), by the control unit (120), a second set of parameters for the secondary energy storage unit (140);
determining (206), by the control unit (120), based on satisfaction of a first set of pre-defined conditions, whether the secondary energy storage unit (140) is to be charged;
selecting (210), by the control unit (120), based on satisfaction of a second set of pre-defined conditions, at least one primary energy storage unit from the plurality of primary energy storage units (110, 112, 114) to charge the secondary energy storage unit (140); and
instructing (212), by the control unit (120), the selected at least one primary energy storage unit to charge the secondary energy storage unit (140).

11. The method (200) as claimed in claim 10, wherein the method comprising the steps of comparing (208), by the control unit (120), based on said determination, the first set of parameters of each of the plurality of primary energy storage units (110, 112, 114).

12. The method (200) as claimed in claim 10, wherein the first set of parameters comprise at least one of: operating voltage, operating current, operating power, State of Charge (SoC), State of Health (SoH), temperature and rate of discharge.

13. The method (200) as claimed in claim 10, wherein the second set of parameters comprise at least one of: State of Charge (SoC) and rate of change of temperature.

14. The method (200) as claimed in claim 13, wherein the first set of pre-defined conditions comprises at least one of:
the State of Charge (SoC) of the secondary energy storage unit (140) being less than a pre-defined State of Charge (SoC); and
the rate of change of temperature of the secondary energy storage unit (140) being less than a pre-defined rate of change of temperature.

15. The method (200) as claimed in claim 12, wherein second set of pre-defined conditions comprises at least one of:
- the selected at least one primary energy storage unit comprising maximum value of State of Charge (SoC) among the plurality of primary energy storage units (110, 112, 114);
- the selected at least one primary energy storage unit comprising maximum value of State of Health (SoH) among the plurality of primary energy storage units (110, 112, 114);
- the selected at least one primary energy storage unit comprising minimum value of temperature among the plurality of primary energy storage units (110, 112, 114); and
- the selected at least one primary energy storage unit comprising minimum value of rate of discharge among the plurality of primary energy storage units (110, 112, 114).

16. The method (200) as claimed in claim 10, wherein the plurality of primary energy storage units (110, 112, 114) having higher voltage than the secondary energy storage unit (140) being connected to each other via a converter (130) configured to step-down the voltage of the plurality of primary energy storage unit (110, 112, 114) to allow charging of the secondary energy storage unit (140).

17. The method (200) as claimed in claim 10, wherein each of the primary energy storage units (110, 112, 114) comprises a switch (150, 152, 154) operated by the control unit (120), the switch (150, 152, 154) configured to control the charging operation from the selected at least one primary energy storage unit to the secondary energy storage unit (140), wherein the control of charging operation comprises in an ON state of switch (150, 152, 154), the selected at least one primary energy storage unit charges the secondary energy storage unit (140) and, in an OFF state of switch (150, 152, 154), the selected at least one primary energy storage unit stops charging of the secondary energy storage unit (140).

18. The method (200) as claimed in claim 10, wherein the plurality of primary energy storage units (110, 112, 114) selected to charge the secondary energy storage unit (140) are connected in one of parallel configuration and series configuration, wherein the configuration being determined by the control unit (120) based on satisfaction of the second set of pre-defined conditions.