DESC:TECHNICAL FIELD
[0001] The present subject matter relates generally to a power source pack. More particularly but not exclusively the present subject matter relates to a cell imbalance in the power source pack.
BACKGROUND
[0002] Nowadays, with the advancement in the technology, an electric or hybrid electric vehicle make use of one or more power source pack to drive the vehicle. The one or more powers source is a battery to provide power to run a motor which in turn runs one or more wheels of the vehicle. The battery pack includes one or more cells and are connected through one or more interconnectors to provide an electrical connection. The one or more cells are arranged in a module consisting of a top casing and a bottom casing. The one or more cells are welded to a metal strip known as the interconnector, forming a battery pack. The one or more interconnector is connected to a BMS (Battery management system). The BMS obtains the individual parameters of the one or more cells to monitor the SoC (state of charge) and SoH (state of health) of the battery pack.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The details are described with reference to an embodiment of a power source pack along with the accompanying diagrams. The same numbers are used throughout the drawings to reference similar features and components.
[0004] Figure 1(a) exemplarily illustrates a side view of the conventional power source pack and a side exploded view of a power source management system connected to the power source pack.
[0005] Figure 1(b) exemplarily illustrates a conventional dual signal interconnector.
[0006] Figure 2 exemplarily illustrates a side view of the of the power source pack and a single interconnector shown separately as per an embodiment of the present invention.
[0007] Figure 3 exemplarily illustrates a side view of the of the power source pack and a single interconnector shown separately as per another embodiment of the present invention.
[0008] Figure 4 exemplarily illustrates a graph showing the comparison of results in the cell imbalance in the proposed design with the existing design, as per an embodiment of the present invention.

DETAILED DESCRIPTION

[0001] Generally, the connection between one or more cell and a battery management system (BMS) is very crucial for efficient working of the battery pack. An interconnector plate made up of metal is used to form the connection between the one or more cells and the BMS. The interconnector plate is welded on the one or more cells and is connected to the BMS through wiring harness. The BMS plays a vital role in monitoring the health of the battery pack. The BMS monitors the voltage, charging current, temperature, state of charge, and the like of the one or more cell for ensuring effective working and long life of the battery pack. In most of the battery pack, the one or more cells are connected to the BMS through the wiring harness to ensure the connection between them. However, if a number of rows of cells is increased, it results in increase in number of interconnectors to be connected between the one or more cells and the BMS, thus resulting in increase of number of wires. So, this leads to complex configuration, wire entanglement and also results in increased assembly time.
[0002] The battery pack is made in a configuration of typically one or more cells arranged in series and parallel to increase the capacity of the battery pack. To ensure that, all the rows containing one or more cells are providing equal charge for driving the various load conditions, the voltage across each row is measured, as measuring the voltage of each cell is difficult. In the existing battery pack, the problem of cell imbalance is a very recurring problem which is to be solved. During the charging and discharging process of the battery pack, if any cell reaches its maximum limit or working threshold (below absolute threshold), the capacity of the battery pack is limited by the imbalance in the cells of the pack, as there are chances that other cells may not have reached to its maximum limit. This reduces the energy usage efficiencies and shortens the lifetime of the battery pack. To avoid this, the charging and discharging process needs to be stopped as soon as any cell reaches its maximum limit. If one or more lithium cells are overheated or overcharged, they are prone to accelerated cell degradation. They can catch fire or even explode as a thermal runaway condition can occur if the one or more lithium ion cell voltage exceeds by even a few hundred millivolts as compared to its predetermined threshold voltage. Thus, battery cell balancing is a basic, but essential function of a BMS and is necessary for the battery packs.
[0003] In order to overcome the above mentioned- problem, two ways of balancing the cell is employed by many battery manufacturers: Active balancing and passive balancing. The conventional passive balancing method prevents the bleeding of excess energy from the one or more cells into heat, while in active balancing there is a transfer of the excess energy into energy-depleted cells. But both the active balancing and passive balancing are relatively more expensive and needs a lot more complex hardware and firmware for its application.
[0004] In an existing interconnector design of the battery pack shows higher row to row voltage difference when current flows through the interconnector. This is because of the resistance of the interconnector is not distributed equally between the one or more rows in the battery pack. However, the row-to-row voltage observed as normal instantly when current flow is stopped in the battery pack. This temporary measurement error occurs when current flows through the interconnector in the existing design. This means that whenever, one or more load is connected to the battery pack or whenever a vehicle having the battery pack accelerates or moves an uphill, the imbalance in the one or more cells occurs, due to change in load in the battery pack. This cell imbalance leads to premature battery aging, also affecting the efficiency and performance of the battery pack. Thus, there is a need to overcome the above-mentioned problems and other problems of known art.
[0005] An objective of the present subject matter is to increase life expectancy of the battery pack while reducing the cell imbalance in battery pack and maintaining the efficiency and capacity of the battery pack. The present subject matter further aims to provide a compact, simple, safe to operate, easy to manufacture, assemble, and service, and also reducing the part count of the battery pack. The present subject matter is described using an exemplary battery pack which is used in the vehicle, whereas the claimed subject matter can be used in any other type of application employing above-mentioned battery pack, with required changes and without deviating from the scope of invention. The embodiments of the present invention will now be described in detail with reference to a power source pack along with the accompanying drawings. However, the present invention is not limited to the present embodiments. The present subject matter is further described with reference to accompanying figures. It should be noted that the description and figures merely illustrate principles of the present subject matter. Various arrangements may be devised that, although not explicitly described or shown herein, encompass the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.
[0006] Fig.1(a) exemplarily illustrates a side view of the conventional power source pack and a side exploded view of a power source management system 110 connected to the power source pack 100. Fig.1(b) exemplarily illustrates a conventional dual signal interconnector 106. Fig.1(a) and Fig.1(b) shall be discussed together. One or more power source casing (not shown) protects the power source pack 100 from outside environment and prevents it’s from getting damage. The power source 100 includes one or more cells (not shown) disposed in one or more cell holder 104 to hold it still in its required position, during the operation of the vehicle (not shown) and also to maintain the required cell arrangement and cell spacing. The power source pack 100 includes the one or more cells (not shown), one or more cell holder 104, and one or more interconnectors 106. The one or more cells provides the electric energy to drive a vehicle (not shown). Typically, the power source casing includes a first casing, a second casing, and a top casing. The first casing supports a front portion (not shown) of the one or more cells. The second casing supports a back portion of the one or more cells. The top casing covers the power source pack 100 from a top portion of the power source pack 100. The one or more casing can be one of the aluminum casing. The one or more cell holder 104 includes provisions (not shown) for one or more interconnector 106 to be housed. The one or more interconnectors 106 are used to make electrical connection between the one or more cells. The one or more cells are welded to the interconnector 106 to form a power source pack 100. The one or more interconnectors 106 are placed above the power source pack 100 and provisions are provided on the power source pack 100 to hold the one or more interconnectors 106 in place.
[0007] In the existing design as shown in fig.1(a) and 1(b), the signal or voltage from one or more cells are collected from every alternate row. In the existing design, two rows are connected through a single interconnector 106, which means one row is of positive polarity and the other row is of negative polarity. So, ideally the voltage for both the positive polarity row and the negative polarity row should be same. But because of the added material to the interconnector 106 and an offset position of one or more voltage sensing tap 108, there is difference between potential of the two positive polarity row and the negative polarity row. The interconnector used as shown in fig.1(a) is a dual sandwiched type of interconnector 106. The dual sandwiched type of interconnector includes a copper sheet and a nickel sheet sandwiched together to reduce the overall resistance of the interconnector 106 and to increase the distribution of current parameter. But the overall thickness of the interconnector 106 increases, as the thickness of copper sheet is 0.6mm and thickness of nickel sheet is 0.2mm, which makes the overall thickness of 0.8mm. This added material also aids in creating a difference between the potential of the two positive polarity and negative polarity rows. This dual sandwiched structure also increases the weight and the cost of the power source pack 100. Apart from this, the one or more voltage sensing tap 108 is used by the power source management system 102 to sense and monitor the row to row voltage difference and health, SOC, SOH of the power source pack 100. In the existing design, the one or more voltage sensing tap 108 is placed at one side edge of the interconnector 106, in line with a row as shown in fig.1(b), which was not able to measure the cell imbalance in both the rows accurately without any error.
[0008] Fig.2 exemplarily illustrates a side view of the of the power source pack 100 and a single interconnector 106 shown separately as per an embodiment of the present invention. The power source pack 100 includes the one or more cells (not shown), one or more cell holder 104, and one or more interconnectors 106. The one or more interconnectors 106 are used to make electrical connection between the one or more cells. The one or more cells are welded to the interconnector 106 to form a power source pack 100. The one or more interconnectors 106 are placed above the power source pack 100 and provisions are provided on the power source pack 100 to hold the one or more interconnectors 106 in place. The present shown power source pack 100 is made up of series and parallel configuration. In an embodiment, 7 columns of cells are connected in parallel and 14 rows of cells are connected in a series. Each two rows having 14 cells are connected by one single interconnector 106. In the present embodiment, R1 (1st row) and R14 (14th row) are connected separately by a single interconnector 106. R1 and R14 interconnectors are power interconnectors 106b, through which power is drawn out of the power source pack 100 to supply to different loads in a vehicle and for traction purposes.
[0009] In the present invention, to ensure the correct measurement of the cell balance and to reduce the cell imbalance, the one or more voltage sensing tap 108 is placed at a centre portion of the edge of an interconnector 106, that is the one or more voltage sensing tap 108 is placed at centre edge between the two row. The one or more voltage sensing tap 108 is placed at an equidistant position on the edge of the interconnector 106. This makes the resistance between all the rows of the cells equal. This reduces the overall resistance of the interconnector 106 and increases the distribution of current parameter, which further reduces the cell imbalance. In the present embodiment, the one or more voltage sensing tap 108 is a L-shaped structure placed at the edge of the interconnectors 106. The one or more voltage sensing tap 108 from all the rows is then connected to the power source management system 102 to provides the various parameters of the power source pack 100 so that the power source management system 102 can monitor and control the voltage differences, SOC, SOH, and the like parameters of the power source pack 100. In the present embodiment, the sandwiched type interconnector 106 is replaced by non-sandwiched type interconnector. In this type, only one nickel sheet of about 0.2mm thickness is used for the interconnector 106. The one or more voltage sensing tap 108 is also made up of the same material as that of the one or more interconnectors, that is nickel sheet. The L-shape of the one or more voltage sensing tap 108 facilitates easy and safer connection with the power source management system 102. The present embodiment reduces the weight, part count, cost of the power source pack 100 and also facilitates ease in assembly with less assembly time.
[00010] Fig.3 exemplarily illustrates a side view of the of the power source pack 100 and a single interconnector 106 shown separately as per another embodiment of the present invention. In the present invention, to ensure the correct measurement of the cell balance and to reduce the cell imbalance, the one or more voltage sensing tap 108 is placed at the centre portion of the edge of the interconnector 106, that is the one or more voltage sensing tap 108 is placed at centre edge between the two row. In the present embodiment, the one or more voltage sensing tap 108 is a S-shaped structure placed at the edge of the interconnectors 106. The one or more voltage sensing tap 108 from all the rows is then connected to the power source management system 102 to provides the various parameters of the power source pack 100 so that the power source management system 102 can monitor and control the voltage differences, SOC, SOH, and the like parameters of the power source pack 100. In the present embodiment, the sandwiched type interconnector 106 is replaced by non-sandwiched type interconnector. In this type, only one nickel sheet of about 0.2mm thickness is used for the interconnector 106. The one or more voltage sensing tap 108 is also made up of the same material as that of the one or more interconnectors, that is nickel sheet. The S-shape of the one or more voltage sensing tap 108 facilitates easy and safer connection with the power source management system 102.
[00011] Fig.4 exemplarily illustrates a graph showing the comparison of results in the cell imbalance in the proposed design with the existing design, as per an embodiment of the present invention. Each two rows having 14 cells are connected by one single interconnector 106. In the present embodiment, R1 (1st row) and R14 (14th row) are connected separately by a single interconnector 106. R1 and R14 interconnectors are power interconnectors 106b, through which power is drawn out of the power source 100 to supply to different loads in a vehicle and for traction purposes. So, if R2 and R3 are taken up for comparison, then the cell imbalance measured in the R2 has increased and in R3, it has decrease, and so on. This shows that the present invention reduces the cell imbalance by using a single layer interconnector 106 of reduced thickness and the is able to measure the cell imbalance correctly. In an alternate embodiment, each row of the cells can be connected with the separate interconnector 106 and separate voltage sensing tap 108.
[00012] The above-mentioned configuration helps in prevention of cell imbalance measurement error and reduces cell imbalance. The elimination of sandwiched type and using a single layer for interconnector plates 106 reduces the no of part count, thickness of the interconnector 106, weight, and cost of the power source pack 100. It further facilitates ease in assembly, decrease in assembly time and simplify manufacturing of the power source pack 100. The change in the interconnector 106 design and change in the positioning of the voltage sensing tap 108 has equalized the resistance in a current flow path, which helps in reducing cell imbalance. The present invention improves the performance, life, and durability of the power source pack 100 and also helps in increasing the mileage of the vehicle. Many other improvements and modifications may be incorporated herein without deviating from the scope of the invention.
List of Reference numerals

100: Power source pack
102: One or more power source management system
104: One or more cell holder
106: One or more interconnectors
106(a): Signal interconnector
106(b): Power interconnector
108: One or more voltage sensing tap

,CLAIMS:We claim:
1.A power source (100) comprising:
one or more cells, the one or more cells are configured to be connected to form the power source (100);
one or more interconnectors (106), the one or more interconnectors 5 (106)are configured to connect the one or more cells, the one or moreinterconnectors (106) having a voltage sensing tap (108);
wherein, the voltage sensing tap (108) is placed in a centre portion of an edge of the one or more interconnectors (106). 10
2.The power source (100) as claimed in claim 1, wherein the voltage sensingtap (108) is placed at an equidistant position on the edge of the one or moreinterconnectors (106).
3.The power source (100) as claimed in claim 1, wherein the voltage sensingtap (108) is a L-shaped.15
4.The power source (100) as claimed in claim 1, wherein the one or moreinterconnectors (106) is a non-sandwich single material.
5.The power source (100) as claimed in claim 4, wherein the one or moreinterconnectors (106) is made of nickel material.
6.The power source (100) as claimed in claim 4, wherein the one or more20 interconnectors (106) is 0.2 mm in width.
7.The power source (100) as claimed in claim 1, wherein a first row (106b)and a last row (106c) of the one or more cells is a single row interconnector(106)and other rows are dual row interconnectors (106).
8.The power source (100) as claimed in claim 1, wherein the voltage sensing25 tap (108) is a S-shaped.
9.The power source (100) as claimed in claim 1, wherein each row of the oneor more cells are connected with individual one or more interconnectors(106)having the voltage sensing tap (108).