Description:FIELD OF INVENTION
The present embodiment relates to the field of Lithium ion batteries of electrical vehicles, and more particularly relates to a system for reducing thermal run-away events of battery packs during a cell short circuit scenario
BACKGROUND OF THE INVENTION
Thermal run-away in Li-ion cells in a well-known phenomenon. A major reason for thermal run-away is short circuit of one or more cells. The short circuit causes a massive amount of current to be fed into the cell that has undergone short circuit from other cells in parallel.
The existing and most widely used cell arrangement in EV battery is as follows:
a. Several cells are connected in parallel (P)– This is referred to as a string
b. Several such strings are connected in series (S)
This configuration has the following drawbacks
a) As the cells are connected in parallel first, short circuit of any one cell pulls the string voltage to zero. The resultant short circuit current is only limited by internal resistance of this string which due to the parallel connection is R/N, where R is the internal resistance of one cell. N is the number of cells in parallel.
b) There is a bus bar connection (Ni strips) welded at both terminals of each and every cell. This increases the bus bar weight and cost. Bus bars carry current from cells, out of the pack.
There are usually 4-6 spots on the cell terminal that has to be fused with the busbar. So even if the weld is proper, the entire surface area of cell terminal is not used. In many cases, all the six spots are not fused with the cell terminal properly, resulting in poor weld quality. The proposed invention aims to address the above-mentioned drawback by (a) Reduce the short circuit current during cell level short circuit by > 80% (b) Reduce the weight of the bus bars by atleast 80% (c) Reduce the weld points by atleast 80%
SUMMARY OF THE INVENTION
In an aspect, a system for reducing thermal run-away of plurality of battery cells is provided. The system includes the plurality of battery cells, plurality of springs, a first busbar and a second busbar.
The cells are connected in series to form a string and the strings are then connected with each other in parallel. This configuration of cells helps in reducing heat generation inside battery pack. Except for the cells in battery negative and battery positive, all other cells are connected to each other directly. The Cells in the battery positive and negative are all connected by bus bar. The rest of the cells are held together using spring pressure.
The preceding is a simplified summary to provide an understanding of some aspects of embodiments of the present invention. This summary is neither an extensive nor exhaustive overview of the present invention and its various embodiments. The summary presents selected concepts of the embodiments of the present invention in a simplified form as an introduction to the more detailed description presented below. As will be appreciated, other embodiments of the present invention are possible utilizing, alone or in combination, one or more of the features set forth above or described in detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and still further features and advantages of embodiments of the present invention will become apparent upon consideration of the following detailed description of embodiments thereof, especially when taken in conjunction with the accompanying drawings, and wherein:
Figure 1 illustrates a system (100) for reducing thermal run-away of plurality of battery cells (102), according to an embodiment herein; and
Figure 2 illustrates an arrangement of the plurality of battery cells (102), according to an embodiment herein.
To facilitate understanding, like reference numerals have been used, where possible, to designate like elements common to the figures.
DETAILED DESCRPTION
As used throughout this application, the word "may" is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include”, “including”, and “includes” mean including but not limited to.
The phrases “at least one”, “one or more”, and “and/or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B, or C” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.
The term “a” or “an” entity refers to one or more of that entity. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. It is also to be noted that the terms “comprising”, “including”, and “having” can be used interchangeably.
As previously mentioned there is a need of the system (100) for reducing thermal run-away of the plurality of battery cells. In a preferred embodiment, the battery is a Lithium Ion battery. The present system (100) helps in reducing the heat generated in the battery pack. The present system (100) helps in reducing the short circuit current during cell level short circuit by 80%.
In an embodiment, the system (100) is the battery pack (shown in Fig. 1). The system (100) includes the plurality of cells (102), plurality of springs (104), a first busbar (106) and a second busbar (108).
The plurality of cells (102) is connected in series to form a string (103). In an embodiment, each string may have any number of cells depending upon the requirement of the battery pack. In a preferred embodiment, each string (103) has 14 cells. In an embodiment, the strings (103) are further connected in parallel configuration (shown in Fig. 2). In an embodiment, the number of strings may vary in number depending upon the requirement of the battery pack. In a preferred embodiment, the number of strings (103) is 14. In the present embodiment, the system (100) has 196 cells (14*14).
In an embodiment, the cells (102) are configured/arranged in such a way so as to reduce the current flowing through the battery cells during cell level short circuit. In an embodiment, the current in each cell will be 17 Amp. The heat generated in the system (100) will be 17*17= 389. In an embodiment, the heat generated in the present system (100) is much lesser than the heat generation in the available systems. In an embodiment, the reconfiguration of the plurality of battery cells (102) improves the thermal performance of the system (100) by 1260 times. This means it is 1260 times less likely to have short circuit of the entire battery pack.
In an embodiment, the configuration of the plurality of battery cells (102) reduces thermal run-away during single cell short circuit. In an embodiment, the string voltage is reduced by a value of nominal voltage of the cell to limit the short circuit current. In an embodiment, the present system (100) reduces the short circuit of the entire battery pack.
The plurality of springs (104) are used for connecting the connecting the plurality of cells (102) through spring pressure. In an embodiment, the spring pressure helps in connecting the plurality of cells to each other. In an embodiment, the plurality of cells that lie between the cells at the battery positive and the battery negative are connected to each other through spring pressure. In an embodiment, the springs (104) are pressed against the first busbar (106) and the second busbar (108). The spring pressure also helps in keeping the negatives and positives of the cells intact.
The busbar is a thin metal strip for connecting the plurality of cells. The first busbar (106) is used for connecting negatives of the battery cell together. The second busbar (108) is used for connecting positives of the battery cell together. In an embodiment, the present system (100) does not require busbar at each and every cell connection. This reduces the cost and weight of the battery pack. In an embodiment, the weight of the system is reduced by 80% due to the first busbar and the second busbar. In an embodiment, the reliability of the system enhances due to one string level fuse rather than multiple cell level fuses. Therefore, the weld points are also reduced by 80% in the present system.
In an embodiment, the plurality of cells (102) is placed inside a battery holder (110). In an embodiment, the battery holder (110) reduces sideways sways of electric current.
In an embodiment, the present battery pack may be installed in any type of electrical vehicles such as, but not limited to, two-wheeler, three-wheeler, four-wheeler and other modes of transportation.
The foregoing discussion of the present invention has been presented for purposes of illustration and description. It is not intended to limit the present invention to the form or forms disclosed herein. In the foregoing Detailed Description, for example, various features of the present invention are grouped together in one or more embodiments, configurations, or aspects for the purpose of streamlining the disclosure. The features of the embodiments, configurations, or aspects may be combined in alternate embodiments, configurations, or aspects other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention the present invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment, configuration, or aspect. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the present invention.
Moreover, though the description of the present invention has included description of one or more embodiments, configurations, or aspects and certain variations and modifications, other variations, combinations, and modifications are within the scope of the present invention, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments, configurations, or aspects to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.

, Claims:WE CLAIM:
1. A system (100) for reducing thermal run-away in plurality of battery cells (102), the system (100) comprises:
- the plurality of cells (102) connected in series to form a string (103) and the plurality of strings (103) connected to each other in parallel for reducing heat generation in the system (100);
- plurality of springs (104) for connecting the plurality of cells through spring pressure, wherein the spring pressure allows the plurality of battery cells (102) that lie between battery negative and battery positive to be connected to each other;
- a first busbar (106) for connecting the cells in battery negative together; and
- a second busbar (108) for connecting the cells in battery positive together.
2. The system (100) as claimed in claim 1, wherein the plurality of cells (102) is placed inside a cell holder (110) for reducing sideways sways.
3. The system (100) as claimed in claim 1, wherein the reconfiguration of the plurality of battery cells (102) reduces thermal run-away during single cell short circuit.
4. The system (100) as claimed in claim 1, wherein the reconfiguration of the plurality of battery cells (102) reduces the heat generation inside the battery pack.
5. The system (100) as claimed in claim 1, wherein the string voltage is reduced by a value of nominal voltage of the cell, thereby limiting the short circuit current.
6. The system (100) as claimed in claim 1, wherein the reconfiguration of the plurality of battery cells (102) improves the thermal performance of the system (100) by 1260 times.
7. The system (100) as claimed in claim 1, wherein the spring (104) is pressed against the first busbar (106) and the second busbar (108).
8. The system (100) as claimed in claim 1, wherein the system (100) does not require busbar at every cell connection, thereby reducing cost and weight.