DESC:METHOD FOR DETERMINING CELL CAPACITY
CROSS REFERENCE TO RELATED APPLICTIONS
The present application claims priority from Indian Provisional Patent Application No. 202321051265 filed on 31/07/2023, the entirety of which is incorporated herein by a reference.
TECHNICAL FIELD
Generally, the present disclosure relates to a battery cell aging determination process. Particularly, the present disclosure relates to a method for determining capacity of a battery cell.
BACKGROUND
In modern age, a lot of devices operate on batteries. With increasing pollution, batteries have emerged as a solution for storing clean energy. Particularly, the battery packs may be used in high power applications such as automotive and energy storage systems. The battery pack is a combination of multiple battery cells combined together to deliver increased capacity and power.
For such high-power applications, the battery pack is designed meticulously using multiple battery cells of same capacity. It essential to use the battery cells of similar capacity with minimum capacity difference between the cells to achieve good operational and service life of the battery pack. It is pertinent to note that all the battery cells are connected with each other in a matrix of series and parallel combination, thus, the capacity of the whole battery pack depends on the least capacity battery cell.
Generally, the capacity of the battery cell is determined by fully charging and then fully discharging the battery cell. The amount of charge requires to then again fully charge the battery cell would be the capacity of the battery cell. However, such process is cumbersome, time taking, energy intense and costly. To overcome these issues, various estimation techniques are utilised. However, such estimation techniques are not accurate leading to inaccurate determination of the capacity of the battery cell.
Therefore, there exists a need for an improved method that accurately determine the capacity of the battery cell and overcomes the one or more problems associated as set forth above.
SUMMARY
An object of the present disclosure is to provide a method of determining capacity of a battery cell.
In accordance with an embodiment of the present disclosure, there is provided a method of determining capacity of a battery cell, wherein the method comprises identifying an initial voltage of the battery cell; altering the initial voltage to reach a first threshold voltage of the battery cell; altering the first threshold voltage to reach a second threshold voltage of the battery cell, or a third threshold voltage of the battery cell; altering the second threshold voltage or the third threshold voltage to reach at a fourth threshold voltage; measuring capacity of the battery cell at a plurality of intermediate voltages between the first threshold voltage, the second threshold voltage or the third threshold voltage, and the fourth threshold voltage; and determining a total capacity of the battery cell based on the measured capacity of the battery cell at the plurality of intermediate voltages.
The method as disclosed by the present disclosure is advantageous in terms of accurately determining the capacity of the battery cell. The method as disclosed by the present disclosure beneficially utilizes shorter charging and discharging cycles. Beneficially, the method of the present disclosure dramatically reduces the time required to determine the capacity of the battery cell. Beneficially, the method of the present disclosure dramatically reduces the energy required to determine the capacity of the battery cell. Beneficially, the method of the present disclosure is less cumbersome to execute and cost efficient.
Additional aspects, advantages, features and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.
It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
Figure 1 illustrate a flow chart of a method of determining capacity of a battery cell, in accordance with an embodiment of the present disclosure.
Figure 2 illustrate a flow chart of a method of determining capacity of a battery cell, in accordance with another embodiment of the present disclosure.
Figure 3 illustrates a flow chart of a method of determining capacity of a battery cell, in accordance with yet another embodiment of the present disclosure.
Figure 4 illustrates a graph representing an actual capacity vs a determined capacity of battery cells using the method of determining capacity of a battery cell, in accordance with an embodiment of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognise that other embodiments for carrying out or practising the present disclosure are also possible.
The description set forth below in connection with the appended drawings is intended as a description of certain embodiments of a method of determining capacity of a battery cell and is not intended to represent the only forms that may be developed or utilised. The description sets forth the various structures and/or functions in connection with the illustrated embodiments; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimised to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
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 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 alternatives falling within the scope of the disclosure.
The terms “comprise”, “comprises”, “comprising”, “include(s)”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, system 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 system. In other words, one or more elements in a system or apparatus preceded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings and which are shown by way of 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.
The present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.
As used herein, the term “battery cell” and “cell” are used interchangeably and refer to a basic unit of a battery that stores and converts chemical energy into electrical energy. It consists of one electrochemical cell, containing an anode (negative electrode), a cathode (positive electrode), and an electrolyte. When the cell is connected to an external circuit, a chemical reaction occurs at the electrodes, generating a flow of electrons through the circuit, which is the electrical current. Battery cells can vary in size, voltage, and chemistry, and are used in a wide range of applications from small electronic devices to large-scale energy storage systems. In a particular example, the battery cell may be lithium-ion cells.
As used herein, the term “cell capacity”, and “capacity of battery cell” are used interchangeably and refer to a measure of the amount of electrical charge a battery cell can store and deliver. It is typically expressed in ampere-hours (Ah) or milliampere-hours (mAh). The capacity indicates how much current a battery can provide over a specified period. For example, a battery with a capacity of 1 Ah can theoretically provide a current of 1 ampere for 1 hour, or 2 amperes for 30 minutes, and so on.
Figure 1, describes a flow chart of a method 100 of determining capacity of a battery cell, in accordance with an embodiment of the present disclosure. The method 100 starts at step 102 and finishes at step 112. At step 102, the method 100 comprises identifying an initial voltage of the battery cell. At step 104, the method 100 comprises altering the initial voltage to reach a first threshold voltage of the battery cell. At step 106, the method 100 comprises altering the first threshold voltage to reach a second threshold voltage of the battery cell, or a third threshold voltage of the battery cell. At step 108, the method 100 comprises altering the second threshold voltage or the third threshold voltage to reach at a fourth threshold voltage. At step 110, the method 100 comprises measuring capacity of the battery cell at a plurality of intermediate voltages between the first threshold voltage, the second threshold voltage or the third threshold voltage, and the fourth threshold voltage. At step 112, the method 100 comprises determining a total capacity of the battery cell based on the measured capacity of the battery cell at the plurality of intermediate voltages.
The method 100 as disclosed by the present disclosure is advantageous in terms of accurately determining the capacity of the battery cell. The method 100 as disclosed by the present disclosure beneficially utilizes shorter charging and discharging cycles. Beneficially, the method 100 of the present disclosure dramatically reduces the time required to determine the capacity of the battery cell. Beneficially, the method 100 of the present disclosure dramatically reduces the energy required to determine the capacity of the battery cell. Beneficially, the method 100 of the present disclosure is less cumbersome to execute and cost efficient.
In an embodiment, the initial voltage, the first threshold voltage, the second threshold voltage, the third threshold voltage, and the fourth threshold voltage of the battery cell are open circuit voltages. It is to be understood that the open circuit voltage (OCV) of the battery cell is the voltage measured across the terminals of the battery cell when it is not connected to any external circuit or load, meaning no current is flowing. It represents the difference in electric potential between the positive and negative electrodes of the battery cell. The OCV is an important parameter as it provides information about the state of charge (SoC) of the battery and can also indicate the health of the battery.
In an embodiment, the total capacity of the battery cell is determined using regression analysis of the capacity of the battery cell at the plurality of intermediate voltages. Beneficially, the total capacity of the battery cell may be determined accurately using the regression analysis.
In an embodiment, altering the initial voltage to reach the first threshold voltage of the battery cell comprises charging the battery cell with a first predefined current. In an embodiment, the initial voltage of the cell may be in a range of 3.4V to 3.6V. In another embodiment, the initial voltage of the battery cell may be in any suitable voltage range according to type of the battery cell. It is to be understood that the cell is received for capacity determination within the initial voltage range. In an embodiment, the first threshold voltage of the battery cell is 3.7V. In another embodiment, the first threshold voltage of the battery cell may be in any suitable voltage range according to type of the battery cell. In an embodiment, the first predefined current is 2.5A. In another embodiment, the first predefined current may be in any suitable current range according to type of the battery cell.
In an embodiment, altering the first threshold voltage to reach the second threshold voltage of the battery cell comprises discharging the battery cell with a second predefined current. In an embodiment, the second threshold voltage of the battery cell is 2.5V. In another embodiment, the second threshold voltage of the battery cell may be in any suitable voltage range according to type of the battery cell. In an embodiment, the second predefined current is 5A. In another embodiment, the second predefined current may be in any suitable current range according to type of the battery cell.
In an embodiment, the battery cell is charged with a third predefined current at the first threshold voltage and rested for a predefined time period at the first threshold voltage before discharging the battery cell with the second predefined current to reach the second threshold voltage. In an embodiment, the third predefined current is 0.15A. In another embodiment, the third predefined current may be in any suitable current range according to type of the battery cell. In an embodiment, the predefined time period is 10 minutes. In another embodiment, the predefined time period may be in any suitable duration according to type of the battery cell.
In an embodiment, altering the second threshold voltage to reach the fourth threshold voltage of the battery cell comprises charging the battery cell with the first predefined current. In an embodiment, the fourth threshold voltage of the battery cell is 3.6V. In another embodiment, the fourth threshold voltage of the battery cell may be in any suitable voltage range according to type of the battery cell.
In an embodiment, altering the first threshold voltage to reach the third threshold voltage of the battery cell comprises charging the battery cell with the first predefined current. In an embodiment, the third threshold voltage of the battery cell is 4.2V. In another embodiment, the fourth threshold voltage of the battery cell may be in any suitable voltage range according to type of the battery cell.
In an embodiment, the battery cell is rested at the third threshold voltage for the predefined time period and charged with the third predefined current at the third threshold voltage.
In an embodiment, altering the third threshold voltage to reach the fourth threshold voltage of the battery cell comprises discharging the battery cell with the second predefined current.
In an embodiment, the battery cell is rested at the third threshold voltage for the predefined time period before discharging with the second predefined current to reach the fourth threshold voltage.
In an embodiment, the method 100 comprises identifying the initial voltage of the battery cell, altering the initial voltage to reach the first threshold voltage of the battery cell, altering the first threshold voltage to reach the second threshold voltage of the battery cell or the third threshold voltage of the battery cell, altering the second threshold voltage or the third threshold voltage to reach at the fourth threshold voltage, measuring capacity of the battery cell at the plurality of intermediate voltages between the first threshold voltage, the second threshold voltage or the third threshold voltage, and the fourth threshold voltage, and determining the total capacity of the battery cell based on the measured capacity of the battery cell at the plurality of intermediate voltages. Furthermore, the method 100 comprises charging the battery cell with the first predefined current for altering the initial voltage to reach the first threshold voltage of the battery cell. Furthermore, the method 100 comprises discharging the battery cell with the second predefined current for altering the first threshold voltage to reach the second threshold voltage of the battery cell. Furthermore, the method 100 comprises charging the battery cell with the third predefined current at the first threshold voltage and resting the battery cell for the predefined time period at the first threshold voltage before discharging the battery cell with the second predefined current to reach the second threshold voltage. Furthermore, the method 100 comprises charging the battery cell with the first predefined current for altering the second threshold voltage to reach the fourth threshold voltage of the battery cell. Furthermore, the method 100 comprises charging the battery cell with the first predefined current for altering the first threshold voltage to reach the third threshold voltage of the battery cell. Furthermore, the method 100 comprises resting the battery cell at the third threshold voltage for the predefined time period and charging with the third predefined current at the third threshold voltage. Furthermore, the method 100 comprises discharging the battery cell with the second predefined current for altering the third threshold voltage to reach the fourth threshold voltage of the battery cell. Furthermore, the method 100 comprises resting the battery cell at the third threshold voltage for the predefined time period before discharging with the second predefined current to reach the fourth threshold voltage.
Figure 2, describes a flow chart of a method 200 of determining capacity of a battery cell, in accordance with another embodiment of the present disclosure. The method 200 starts at step 202 and finishes at step 212. At step 202, the method 200 comprises identifying an initial voltage of the battery cell. At step 204, the method 200 comprises altering the initial voltage to reach a first threshold voltage of the battery cell. At step 206, the method 200 comprises altering the first threshold voltage to reach a second threshold voltage of the battery cell. At step 208, the method 200 comprises altering the second threshold voltage to reach at a fourth threshold voltage. At step 210, the method 200 comprises measuring capacity of the battery cell at a plurality of intermediate voltages between the first threshold voltage, the second threshold voltage, and the fourth threshold voltage. At step 212, the method 200 comprises determining a total capacity of the battery cell based on the measured capacity of the battery cell at the plurality of intermediate voltages.
In an embodiment, the initial voltage, the first threshold voltage, the second threshold voltage, and the fourth threshold voltage of the battery cell are open circuit voltages.
In an embodiment, altering the initial voltage to reach the first threshold voltage of the battery cell comprises charging the battery cell with a first predefined current.
In an embodiment, altering the first threshold voltage to reach the second threshold voltage of the battery cell comprises discharging the battery cell with a second predefined current.
In an embodiment, the battery cell is charged with a third predefined current at the first threshold voltage and rested for a predefined time period at the first threshold voltage before discharging the battery cell with the second predefined current to reach the second threshold voltage.
In an embodiment, altering the second threshold voltage to reach the fourth threshold voltage of the battery cell comprises charging the battery cell with the first predefined current.
In an exemplary embodiment, the battery cell is at an initial voltage of 3.4V. The battery cell is charged from 3.4V to 3.7V using constant current of 2.5A. The battery cell is then charged at constant voltage of 3.7V with cutoff current of 0.15A. The battery cell is then rested to 10 minutes. Then the battery cell is discharged with constant current of 5A till it reaches the 2.5V. After the battery cell is at 2.5V, the battery cell is charged to 3.6V using constant current of 2.5A. The capacity is the battery cell is measured at various intermediate voltages during the above cycle. Then the regression analysis is performed on the capacity measured at various intermediate voltages during the cycle to determine the total capacity of the battery cell.
Figure 3, describes a flow chart of a method 300 of determining capacity of a battery cell, in accordance with yet another embodiment of the present disclosure. The method 300 starts at step 302 and finishes at step 312. At step 302, the method 300 comprises identifying an initial voltage of the battery cell. At step 304, the method 300 comprises altering the initial voltage to reach a first threshold voltage of the battery cell. At step 306, the method 200 comprises altering the first threshold voltage to reach a third threshold voltage of the battery cell. At step 308, the method 300 comprises altering the third threshold voltage to reach at a fourth threshold voltage. At step 310, the method 300 comprises measuring capacity of the battery cell at a plurality of intermediate voltages between the first threshold voltage, the second threshold voltage, and the fourth threshold voltage. At step 312, the method 300 comprises determining a total capacity of the battery cell based on the measured capacity of the battery cell at the plurality of intermediate voltages.
In an embodiment, altering the first threshold voltage to reach the third threshold voltage of the battery cell comprises charging the battery cell with the first predefined current.
In an embodiment, the battery cell is rested at the third threshold voltage for the predefined time period and charged with the third predefined current at the third threshold voltage.
In an embodiment, altering the third threshold voltage to reach the fourth threshold voltage of the battery cell comprises discharging the battery cell with the second predefined current.
In an embodiment, the battery cell is rested at the third threshold voltage for the predefined time period before discharging with the second predefined current to reach the fourth threshold voltage.
In an exemplary embodiment, the battery cell is at an initial voltage of 3.4V. The battery cell is charged from 3.4V to 3.7V using constant current of 2.5A. The battery cell is then charged to 4.2V using constant current of 2.5A. The battery cell is then rested for 10 minutes. Then the battery cell is charged at constant voltage of 4.2V with cutoff current of 0.15A. The battery cell is then rested to 10 minutes. Then the battery cell is discharged with constant current of 5A till it reaches the 3.6V. The capacity is the battery cell is measured at various intermediate voltages during the above cycle. Then the regression analysis is performed on the capacity measured at various intermediate voltages during the cycle to determine the total capacity of the battery cell.
Figure 4 illustrates a graph 400 representing an actual capacity vs a determined capacity of battery cells using the method of determining capacity of a battery cell. The x-axis of the graph 400 represents actual capacity of the battery cell determined using the conventional full charge cycle method. The y-axis of the graph 400 represents estimated capacity of the of the battery cell determined using the method 100, method 200 and/or method 300. The dotted line on the graph 400 represents values for the actual capacity of the battery cell determined using the conventional full charge cycle method. The straight lines represent a tolerance range of deviation from the actual capacity of the battery cell determined using the conventional full charge cycle method. The black dots on the graph represent the values for the estimated capacity of the battery cell determined using the method 100, method 200 and/or method 300. As shown in the graph, the values for the estimated capacity of the battery cell determined using the method 100, method 200 and/or method 300 is within the tolerance range of deviation from the actual capacity of the battery cell determined using the conventional full charge cycle method. The graph signifies the accuracy of the determination of the estimated capacity of the battery cell determined using the method 100, method 200 and/or method 300.
It would be appreciated that all the explanations of the method 100 also applies mutatis-mutandis to the method 200 and the method 300.
In the description of the present invention, it is also to be noted that, unless otherwise explicitly specified or limited, the terms “disposed,” “mounted,” and “connected” are to be construed broadly, and may for example be fixedly connected, detachably connected, or integrally connected, either mechanically or electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Modifications to embodiments and combination of different embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as “including”, “comprising”, “incorporating”, “have”, “is” used to describe and claim the present disclosure are intended to be construed in a non- exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural where appropriate.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the present disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.
,CLAIMS:WE CLAIM:
1. A method (100) of determining capacity of a battery cell, wherein the method (100) comprises:
- identifying an initial voltage of the battery cell;
- altering the initial voltage to reach a first threshold voltage of the battery cell;
- altering the first threshold voltage to reach:
- a second threshold voltage of the battery cell; or
- a third threshold voltage of the battery cell;
- altering the second threshold voltage or the third threshold voltage to reach at a fourth threshold voltage;
- measuring capacity of the battery cell at a plurality of intermediate voltages between the first threshold voltage, the second threshold voltage or the third threshold voltage, and the fourth threshold voltage; and
- determining a total capacity of the battery cell based on the measured capacity of the battery cell at the plurality of intermediate voltages.
2. The method (100) as claimed in claim 1, wherein the initial voltage, the first threshold voltage, the second threshold voltage, the third threshold voltage, and the fourth threshold voltage of the battery cell are open circuit voltages.
3. The method (100) as claimed in claim 1, wherein altering the initial voltage to reach the first threshold voltage of the battery cell comprises charging the battery cell with a first predefined current.
4. The method (100) as claimed in claim 1, wherein altering the first threshold voltage to reach the second threshold voltage of the battery cell comprises discharging the battery cell with a second predefined current.
5. The method (100) as claimed in claim 4, wherein the battery cell is charged with a third predefined current at the first threshold voltage and rested for a predefined time period at the first threshold voltage before discharging the battery cell with the second predefined current to reach the second threshold voltage.
6. The method (100) as claimed in claim 1, wherein altering the second threshold voltage to reach the fourth threshold voltage of the battery cell comprises charging the battery cell with the first predefined current.
7. The method (100) as claimed in claim 1, wherein altering the first threshold voltage to reach the third threshold voltage of the battery cell comprises charging the battery cell with the first predefined current.
8. The method (100) as claimed in claim 7, wherein the battery cell is rested at the third threshold voltage for the predefined time period and charged with the third predefined current at the third threshold voltage.
9. The method (100) as claimed in claim 1, wherein altering the third threshold voltage to reach the fourth threshold voltage of the battery cell comprises discharging the battery cell with the second predefined current.
10. The method (100) as claimed in claim 9, wherein the battery cell is rested at the third threshold voltage for the predefined time period before discharging with the second predefined current to reach the fourth threshold voltage.