Claims:We claim:
1. A method of fast charging at least one battery pack (108) in an electric vehicle, the method comprising:
receiving (202), by a charging control module (106), State of Charge (SOC) of the at least one battery pack (108);
modulating (206), by the charging control module (106), a C-rate for charging the at least one battery pack (108) based on the received SOC in a look up table stored in a battery management system (100); and
applying, by the charging control module (106), a charging current to the at least battery pack (108) based on the SOC in the look up table, if temperature of the at least one battery pack (108) is within a pre-determined temperature threshold and if charging voltage is below a pre-determined voltage threshold.
2. The method as claimed in claim 1, wherein the method comprises stopping, by the charging control module (106), the fast charging, if the temperature of the at least one battery pack (108) is above the pre-determined temperature threshold and if charging voltage is above the pre-determined voltage threshold.
3. The method as claimed in claim 1, wherein modulating the C-rate, comprises determining an input current, by the charging control module (106), for an entire SOC, by considering a minimum amount of degradation.
4. A battery management system (100) for fast charging at least one battery pack (108) in an electric vehicle, the battery management system (100) comprising:
a charging control module (106) configured to:
receive a State of Charge (SOC) of the at least one battery pack (108);
modulate a C-rate for charging the at least one battery pack (108) based on the received SOC in a look up table stored in a battery management system (100); and
apply charging current to the at least battery pack (108) based on the SOC in the look up table, if temperature of the at least one battery pack (108) is within a pre-determined temperature threshold and if charging voltage is below a pre-determined voltage threshold.
5. The battery management system (100) as claimed in claim 4, wherein the charging control module (106) is configured to stop the fast charging, if the temperature of the at least one battery pack (108) is above the pre-determined temperature threshold and if charging voltage is above the pre-determined voltage threshold.
6. The battery management system (100), as claimed in claim 4, wherein the charging control module (106) is configured to modulate the C-rate based on the SOC by determining the input current for an entire SOC, by considering a minimum amount of degradation.
, Description:TECHNICAL FIELD
[001] Embodiments disclosed herein relate to electric vehicles, and more particularly to management of fast charging energy storage systems present in electric vehicles.

BACKGROUND
[002] Lithium ion batteries are widely used in systems such as electric vehicles. Lithium ion batteries are characterized by high energy density, high power density, and a low self-discharge rate. However, the battery life of the Lithium ion batteries poses a challenge to the electric vehicle industry. The battery life is dependent on battery aging and degradation. Battery aging and degradation limit energy storage and power output in the battery, thereby affecting the performance of the electric vehicle.
[003] Current fast charging techniques involve charging with higher current which requires faster cooling of the battery and therefore is energy intensive. In existing fast charging techniques, capacity retention decreases rapidly as the number of charging/discharging cycles increase. Further, in existing fast charging methods, fast charging uses a constant 1C C-rate until 80% State of Charge (SOC). Currently, there are no techniques that provide fast charging of the battery and the extension of the battery life simultaneously, resulting in charging of the battery with minimum capacity fade.
OBJECTS
[004] The principal object of embodiments herein is to disclose methods and systems for modulating charging rates of at least one lithium-ion battery pack in an electric vehicle, wherein the at least one lithium-ion battery pack is currently undergoing fast charging.
[005] Another object of embodiments herein is to disclose techniques for improving battery health by reducing amount of degradation of the lithium-ion battery pack based on ambient temperatures, when at least one lithium-ion battery pack is currently undergoing fast charging.
[006] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating at least one embodiment and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF FIGURES
[007] Embodiments herein are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[008] FIG. 1 illustrates a battery management system (BMS), according to embodiments as disclosed herein;
[009] FIG. 2 illustrates method for fast charging with minimum capacity fade, according to embodiments as disclosed herein;
[0010] FIG. 3 illustrates a method for fast charging based on temperature of the battery pack, according to embodiments disclosed herein;
[0011] FIG. 4 illustrates a comparison between existing fast charging until 80% and fast charging according to embodiments as disclosed herein;
[0012] FIG. 5 illustrates a comparison between number of cycles with respect to temperature in existing fast charging until 80% and fast charging according to embodiments as disclosed herein; and
[0013] FIG. 6 illustrates a comparison between existing fast charging until 80% and fast charging according to the embodiments herein, with respect to C-rates modulation.

DETAILED DESCRIPTION
[0014] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0015] The embodiments herein achieve fast charging of batteries as well as battery life extension by fast charging with minimum capacity fade. Referring now to the drawings, and more particularly to FIGS. 1 through 6, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0016] Battery degradation in Lithium ion batteries comprises capacity fade and power fade. Capacity fade is quantified as a decrease in the amount of energy a battery can store. The rate at which a battery capacity is lost depends on charging/discharging conditions such as temperature, maximum voltage, depth of discharge (DoD), and current and load profiles. Power fade is quantified as a decrease in the amount of power a battery can provide, which can be caused due to an increase in the battery's internal impedance. The power and the capacity of the batteries are controlled and monitored by a Battery management system (BMS). Embodiments herein consider batteries with Lithium iron phosphate (LiFePO4) as an example material used for the cathode, however it may be obvious to a person of ordinary skill in the art that the embodiments herein are not limited to the Lithium iron phosphate based batteries.
[0017] FIG. 1 illustrates a battery management system (BMS) 100, according to embodiments described herein. The battery management system 100 and/or any other relevant devices or components according to embodiments described herein may be implemented by utilizing any suitable hardware, firmware, for e.g., an application-specific integrated circuit, software, or a suitable combination of software, firmware, and hardware. For example, the various components of the battery management system may be formed on one integrated circuit (IC) chip or on separate IC chips. Further, the various components of the battery management system may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or formed on a same substrate as the battery management system. Further, the various components of the battery management system may be a process or thread, or modules, running on one or more processors, in one or more computing devices, executing computer program instructions and interacting with other system components for performing the various functionalities described herein. The computer program instructions are stored in a memory which may be implemented in a computing device using a standard memory device, such as a random access memory (RAM). The computer program instructions may also be stored in other non-transitory computer readable media such as a CD-ROM, flash drive, or the like. Also, a person of skill in the art should recognize that the functionality of various computing devices may be combined or integrated into a single computing device, or the functionality of a particular computing device may be distributed across one or more other computing devices without departing from the scope of the embodiments of the present invention. The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the network elements. The network elements shown in Fig. 1 include blocks which can be at least one of a hardware device, or a combination of hardware device and software module.
[0018] The BMS 100 comprises a processor 102 and a memory 104 storing a charging control module 106 which is executed by the processor 102. The BMS 100 manages and controls at least one battery pack 108 by protecting the at least one battery pack from operating outside the at least one battery pack’s optimal voltage, temperature and current values. Further, the BMS 100 can monitor and control the state of the at least battery pack 108, collect and report data from the at least one battery pack 108 , and control the at least one battery pack. The at least battery pack, can be, for example, but not limited to a Lithium ion battery pack. Each battery pack comprises a plurality of cells or batteries. The at least one battery pack 108 communicates with the BMS 100 through an external communication data bus thereby forming a smart battery pack which is charged by a charger. According to the embodiments herein, the charging control module 106 can regulate C-rate depending on the State of Charge (SOC) of at least one battery pack 108. The SOC of the battery is the present battery capacity as a percentage of the maximum capacity. The charging control module 106 acts as an interface between the charger and the at least one battery pack 108. The at least one battery pack 108 is considered to be fully charged when the charging of the at least one battery pack reaches 100 % State of Charge (SOC). The quantity of the charge or the quantity of electrons pumped to the at least one battery pack 108 is a direct function of the SOC. The amount of charge per given time is the C-rate.
[0019] . The charging control module 106 can modulate C-rates depending on the SOC. For example, the aging impact of a particular charging current or the C-rate for a 70% SOC battery pack is different from the same C-rate for a 50% SOC battery pack. Depending on the SOC of the at least one battery pack 108, the charging current rate or the C-rate needs to be regulated through the BMS 100. The choice of the C-rate is taken from the lookup table, such as, a table shown in Table 1, for a particular temperature of operation. The look up table can be stored in a database associated with the BMS 100 by enabling a pre-written algorithm. The database (not shown in FIG. 1) can be present internally in the BMS 100, or can be external to the BMS 100. In another example, the charging control module 106 can use a C-rate of 0.12C for a 70% SOC. The C-rate is a measure of the rate at which a battery is charged or discharged relative to its maximum capacity. A 1C rate means that the discharge current will discharge the entire battery in 1 hour. The charging control module 106 can determine the C-rate for the entire SOC by considering that the amount of degradation to be minimum. The amount of degradation is determined by the capacity loss in the at least one battery pack 108. The amount of degradation depends on factors, such as temperature, C-rate, Depth of Discharge (DoD), and the like, thereby resulting in an increase in internal resistance in the at least one battery pack 108. Therefore, the internal resistance in the at least one battery pack 108 is to be minimized. The degradation that occurs due to charging is determined as a function of the activation and diffusion polarization leading to the increase in internal resistance. The BMS 100 which is equipped with State of Health (SOH) feature, captures the change in internal resistance as the number of the charging/discharging cycles increases. The internal resistance varies with SOC at a particular SOH. According to the embodiments herein, the C-rate is modulated with SOC in such a way that the modulation does not increase the temperature of the at least one battery due to the charging as compared to the charging with a constant C-rate. When the charging is performed by regulating the C-rate based on the SOC ranges, the electrode level temperature rise and degradation are kept under check, thereby leading to an increase in cycle life.
SOC range Ich
Range 1 C-rate step 1
Range 2 C-rate step 2
Range 3 C-rate step 3
Range 4 C-rate step 4
Range 5 C-rate step 5
Range 6 C-rate step 6
TABLE 1
[0020] The charging control module 106 detects if temperature of the at least one battery pack 108 is within a pre-determined temperature threshold. On detecting that the temperature of the at least one battery pack 108 is within the pre-determined temperature threshold, the charging control module 106 detects if a charging voltage is below a pre-determined voltage threshold. If the temperature of the at least one battery pack 108 is not within the pre-determined temperature threshold, the charging control module 106 stops the charging process. If the charging voltage is above the pre-determined voltage threshold, the charging control module 106 stops the charging process. If the charging voltage is below the pre-determined voltage threshold, the charging control module 106 applies charging current based on the SOC range in the look-up table (Table 1).
[0021] According to embodiments herein, the crucial SOC ranges at which that particular cell chemistry tends to experience temperature rise and thereby capacity fade, are determined. Based on the electrochemistry, the crucial SOC ranges which are sensitive to high currents are selected and the C-rates are modulated. According to the embodiments herein, low C-rates are selected for crucial SOC ranges and high C-rates are selected for non-problematic SOC ranges, thereby enhancing the cycle life of the batteries without compromising the charging time. The internal resistance values are high in the crucial SOC ranges. As mentioned earlier, the internal resistance is the function of activation and diffusion polarization losses.
[0022] The non-problematic SOC range is the SOC range which inhibits less temperature rise due to internal resistance, even with a relatively high C-rate being applied. In literature, they impose low C-rates at 0 to 10% SOC and they gradually increase the C-rates until it reaches 70 to 80% SOC. Once it reaches the 80%, they gradually decrease the C-rate until it reaches 100%. %. In literature for example, it would be 0.3 until 10% SOC, 0.5 C until 20 % SOC and 0.7 C until 30 % SOC, and so on. However, embodiments herein disclose a method in which the C-rate profile is designed based on the Internal resistance profile, much specific to the chemistry. With this, it enables application of 1.5 C C-rate for the SOC range 5 to 40% without any rise in temperature and the consequential aging. This is what is referred to herein as non-problematic SOC range.
[0023] FIG. 2 illustrates method for fast charging with minimum capacity fade, according to embodiments described herein. At step 202, the charging control module 106 receives State of Charge (SOC) value in terms of a percentage (%). The BMS 100 can determine the SOC of the battery which can be transmitted to the charging control module 106. At step 204, the charging control module 106 regulates C-rate based on the received SOC, based on the look table shown in Table 1. For example, a battery with 70% SOC requires a charging current different from that of the battery with 30% SOC. The charging control module 106 can use a C-rate of 1.2C for 30% SOC battery whereas the charging control module 106 can use a C-rate of 0.12C for an 80% SOC battery.
[0024] The various actions in method 200 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some actions listed in FIG. 2 may be omitted.
[0025] FIG. 3 illustrates a method for fast charging with respect to temperature of the battery pack 108, according to embodiments herein. At step 302, the charging control module 106 detects if temperature of the at least one battery pack 108 is within a pre-determined temperature threshold. At step 304, if the temperature of the at least one battery pack 108 is not within the pre-determined temperature threshold, the charging control module 106 stops the charging process. At step 306, on detecting that the temperature of the at least one battery pack 108 is within the pre-determined temperature threshold, the charging control module 106 detects if a charging voltage is below a pre-determined voltage threshold. At step 308, if the charging voltage is above the pre-determined voltage threshold, the charging control module 106 stops the charging process. At step 310, if the charging voltage is below the pre-determined voltage threshold, the charging control module 106 applies charging current based on the SOC range in the look-up table (Table 1).
[0026] The various actions in method 300 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some actions listed in FIG. 3 may be omitted.
RESULTS:
[0027] FIG. 4 illustrates a comparison between existing fast charging until 80% and fast charging according to the embodiments herein. The fast charging technique according to the embodiments herein is also referred to as intelligent fast charging 404. In the existing fast charging techniques 402, capacity retention decreases rapidly as the number of cycles increases. Fast charging according to the embodiments 404 show a gradual decrease in the capacity retention percentage as the number of charging/discharging cycles increase. For example, after 2100 cycles, the capacity retention in the case of existing fast charging methods is about 83% whereas in the case of intelligent fast charging technique according to the embodiments herein, is 86%.
[0028] FIG. 5 illustrates a comparison between number of cycles with respect to temperature in existing fast charging until 80% and fast charging according to the embodiments herein. The shaded portion 502 indicates difference in cycle life between the existing until 80% and fast charging according to the embodiments herein. For example, at temperature 25°C, the cycle life in case of the existing fast charging methods is about 3300 whereas, the number of cycles, in the case of intelligent fast charging techniques according to the embodiments herein, is about 2800.
[0029] FIG. 6 illustrates a comparison between existing fast charging until 80% and fast charging according to the embodiments herein, with respect to C-rates modulation. The fast charging according to the embodiments herein 602 differentiates from the existing fast charging 604 in that the fast charging according to the embodiments herein modulates the C-rates depending on the SOC. In the existing fast charging, the C-rate is kept constant as 1C. Table 2 shows comparison of SOC range, C-rate, and time taken for charging between existing fast charging methods and the fast charging technique in accordance with the embodiments described herein. According to the existing fast charging methods, at all the ranges of SOC, the C-rate is kept constant. Whereas, according to the embodiments herein, the C-rate is varied according to the range of SOC. For example, charge step 1 can correspond to a current pulse applied for a certain period of time and range 1 of SOC can correspond to a range of SOC between 0% to 15%. C-rate is determined by the range of SOC. The C-rate can vary according to the range of the SOC.
[0030] Table 3 shows experimental values of the SOC range, C-rate, and the time taken for the fast charging, according to the embodiments herein.

Charge profile Typical fast charging until 80% Fast charging according to embodiments herein
SOC range C-rate Time in minutes SOC range C-rate Time in minutes
Charge step 1 Range 1 1

48 Range 1 Step1

47.6
Charge step 2 Range 2 1 Range 2 Step2
Charge step 3 Range 3 1 Range 3 Step3
Charge step 4 Range 4 1 Range 4 Step4
Charge step 5 Range 5 1 Range 5 Step5
Charge step 6 Range 6 1 Range 6 Step6

TABLE 2

Charge profile SOC range C-rate Time in minutes
Charge step 1 0 0.05 0.8 3.75
Charge step 2 0.05 0.4 1.5 14
Charge step 3 0.4 0.5 0.9 6.66
Charge step 4 0.5 0.6 0.8 7.5
Charge step 5 0.6 0.7 0.7 8.57
Charge step 6 0.7 0.8 0.8 7.5
Total time 47.604

TABLE 3
[0031] The embodiment disclosed herein describes methods and system for fast charging with minimum capacity fade. Further, the embodiments herein provide a fast charging technique with improved battery life. The embodiments herein eliminate the necessity of using extra energy for cooling down the battery while fast charging which provides overall cooling efficiency and efficient thermal management. Therefore, it is understood that the scope of the protection is extended to such a program and in addition to a computer readable means having a message therein, such computer readable storage means contain program code means for implementation of one or more steps of the method, when the program runs on a server or mobile device or any suitable programmable device. The method is implemented in at least one embodiment through or together with a software program written in e.g. Very high speed integrated circuit Hardware Description Language (VHDL) another programming language, or implemented by one or more VHDL or several software modules being executed on at least one hardware device. The hardware device can be any kind of portable device that can be programmed. The device may also include means which could be e.g. hardware means like e.g. an ASIC, or a combination of hardware and software means, e.g. an ASIC and an FPGA, or at least one microprocessor and at least one memory with software modules located therein. The method embodiments described herein could be implemented partly in hardware and partly in software. Alternatively, the invention may be implemented on different hardware devices, e.g. using a plurality of CPUs.
[0032] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments and examples, those skilled in the art will recognize that the embodiments and examples disclosed herein can be practiced with modification within the scope of the embodiments as described herein.