The present disclosure generally relates to electrochemical batteries. In particular, the present disclosure relates to batteries used in electric vehicles, such as hybrid-electric vehicles or plug-in hybrid vehicles (PHEV) that are collectively referred to as “HEVs”, that derive some or all of their motive power through the battery or battery system.
HEVs make up a significant portion of the automobile market mainly due to the ability to promote fuel economy and reduce vehicle emissions by using a combination of electric power and combustion. Many efforts have been put into increasing the efficiency of automobile (e.g., cars, trucks, etc.) batteries. An ongoing goal for the automobile battery is to retain high energy density, which means high voltage and light weight.
Conventional batteries for an HEV may use nickel metal hydride (Ni-MH) cells. However, Ni-MH battery cells are often heavier than lithium ion (Li-ion) battery cells and have a lower nominal voltage. A battery module in a Toyota® Prius®' has six Ni-MH battery cells and weighs more than 1 kilogram. The voltage of a Toyota® Prius® battery pack is 7.2V. A battery module with five Li-ion battery cells weighs about 1.2 kilograms but has 16V output. That is to say, a battery module with five Li-ion battery cells weighs less than two Toyota® Prius battery packs and has a higher voltage. Therefore, Li-ion battery cells have a high energy density.
While Ni-MH battery cells do not require a balancing circuit due to their characteristics, such a balancing circuit is needed for Li-ion battery cells within a Li-ion battery module to ensure even charging across the battery cells.
The temperature of the battery cells, especially during charging and discharging, affects their performance. Therefore, there remains a need to provide compact cooling structure for a Li-ion battery pack.
Therefore, there is room for improvement within the art.
In accordance with a first aspect of the present disclosure, a battery module for an electric motor vehicle includes a case, a plurality of rechargeable battery cells, and an overcharge protection circuit. The plurality of rechargeable battery cells is stored inside the case and connected in series. Each of the plurality of battery cells has a nominal voltage and a maximum voltage. The overcharge protection circuit has a voltage threshold for each of the plurality of rechargeable battery cells to prevent overcharging. The voltage threshold is larger than the nominal voltage and smaller than the maximum voltage.
In an embodiment of the first aspect, each of the plurality of rechargeable battery cells is lithium-based and selected from the group consisting of lithium titanate Li4Ti5O12, lithium iron phosphate LiFePO4, lithium cobalt oxide LiCoO2, lithium manganese oxide LiMn2O4, lithium nickel manganese cobalt oxide LiNiMnCoO2 (NMC), lithium nickel cobalt oxide LiNiCoO2 (NC), or lithium nickel cobalt aluminum oxide LiNiCoAlO2.
In another embodiment of the first aspect, the case further includes at least one air vent. A number of the plurality of rechargeable battery cells may be five.
In yet another embodiment of the first aspect, the nominal voltage may be the same for each of the plurality of rechargeable battery cells. The overcharge protection circuit prevents overcharging through dissipation via resistors.
In accordance with a second aspect of the present disclosure, a battery module for an electric motor vehicle includes a rectangular case and a plurality of rechargeable battery cells. The plurality of rechargeable battery cells is stored inside the case and connected in series. The case includes at least one air vent on at least one side of the case.
In an embodiment of the second aspect, each of the plurality of rechargeable battery cells is lithium-based and selected from the group consisting of lithium titanate Li4Ti5O12, lithium iron phosphate LiFePO4, lithium cobalt oxide LiCoO2, lithium manganese oxide LiMn2O4, lithium nickel manganese cobalt oxide LiNiMnCoO2 (NMC), lithium nickel cobalt oxide LiNiCoO2 (NC), or lithium nickel cobalt aluminum oxide LiNiCoAlO2.
In another embodiment of the second aspect, all of the plurality of rechargeable battery cells are comprised of lithium titanate Li4Ti5O12, and a number of the plurality of rechargeable battery cells is seven.
In yet another embodiment of the second aspect, all of the plurality of rechargeable battery cells are comprised of lithium iron phosphate LiFePO4, and a number of the plurality of rechargeable battery cells is five.
In another embodiment of the second aspect, a number of the plurality of rechargeable battery cells is four, and each of the plurality of rechargeable battery cells is selected from a group consisting of lithium cobalt oxide LiCoO2, lithium manganese oxide LiMn2O4, lithium nickel manganese cobalt oxide LiNiMnCoO2 (NMC), lithium nickel cobalt oxide LiNiCoO2 (NC), and lithium nickel cobalt aluminum oxide LiNiCoAlO2.
In yet another embodiment of the second aspect, the battery module includes an overcharge protection circuit that has a voltage threshold for each of the plurality of rechargeable battery cells to prevent overcharging. Each of the plurality of rechargeable battery cells has a nominal voltage and a maximum voltage. The voltage threshold is larger than the nominal voltage and smaller than the maximum voltage. The overcharge protection circuit prevents overcharging through dissipation via resistors.
In accordance with a third aspect of the present disclosure, a battery module for an electric motor vehicle includes a case and a plurality of rechargeable battery cells. The plurality of rechargeable battery cells is stored inside the case and connected in series. The plurality of rechargeable battery cells is stored in a parallel configuration inside the case in a plurality of rows. At least one of the plurality of rechargeable battery cells is stored in each of the plurality of rows.
In an embodiment of the third aspect, each of the plurality of rechargeable battery cells is lithium-based and selected from the group consisting of lithium titanate Li4Ti5O12, lithium iron phosphate LiFePO4, lithium cobalt oxide LiCoO2, lithium manganese oxide LiMn2O4, lithium nickel manganese cobalt oxide LiNiMnCoO2 (NMC), lithium nickel cobalt oxide LiNiCoO2 (NC), or lithium nickel cobalt aluminum oxide LiNiCoAlO2.
In an embodiment of the third aspect, the battery module further includes an overcharge protection circuit that has a voltage threshold for each of the plurality of rechargeable battery cells to prevent overcharging. Each of the plurality of rechargeable battery cells has a nominal voltage and a maximum voltage. The voltage threshold is larger than the nominal voltage and smaller than the maximum voltage.
In another embodiment of the third aspect, the case further includes at least one air vent.
In yet another embodiment of the third aspect, the plurality of rows includes a first row storing three of the plurality of rechargeable battery cells and a second row storing two of the plurality of rechargeable battery cells. A free battery cell space in the second row stores an overcharge protection circuit.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached figures.
It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better show details and features of the present disclosure.
Several definitions that apply throughout this disclosure will now be presented.
The term “comprising” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the equivalent.
An HEV has an internal combustion engine (e.g., operates on fuel such as gasoline, etc.) and an electric motor which are separated from one another. The HEV may utilize electric power stored in a Ni-MH battery instead of power from combustion whenever possible. The HEV may operate through the electric motor when driven at low speeds, may require energy from the internal combustion engine upon acceleration, and may use both the electric motor and the internal combustion engine to sufficiently power the vehicle during light acceleration.
In
The battery pack of an HEV may include a number of Ni-MH battery modules. For example, a Toyota® Prius® battery pack may include 28 Ni-MH battery modules. Each of these battery modules 200 (illustrated in
In
On the front side 402 and rear side 406 of the battery case 400, there are a plurality of ridges 415 to allow space between two adjacent battery modules. The space between two adjacent battery modules enables efficient cooling of the two adjacent battery modules. The plurality of ridges 415 may further allow interlocking of two adjacent battery modules. The ridges 415 may also prevent accidentally mixing the lithium battery cells with preexisting Ni-MH battery cells in a battery pack.
In one example embodiment, the battery case 400 may further include a plurality of perforations 416 on each of the top side 410 and the underside 411. The plurality of perforations 416 allow for the heat exchange of the plurality of battery cells 302 through enhanced air flow.
In yet another embodiment, the battery case 400 may further include dividers (not shown) such that the lithium battery cells (e.g., battery cells 302 in
As depicted in
The lithium battery cells (e.g., 302 in
In one embodiment of the present disclosure, the battery cells may include Li4Ti5O12 cells, and the number of battery cells within an example LiFePO4 battery cell structure 300 may be seven. For example, three Li4Ti5O12 battery cells may be layered in a first row, and four Li4Ti5O12battery cells may be layered on a second row parallel to the first row.
In one embodiment of the present disclosure, the battery cells may include LiFePO4 cells, and the number of battery cells within an example LiFePO4 battery cell structure 300 may be five. For example, three LiFePO4 battery cells may be layered in a first row, and two LiFePO4 battery cells may be layered in a second row parallel to the first row.
In another embodiment of the present disclosure, the battery cells may include LiCoO2 cells, and the number of battery cells within an example LiFePO4 battery cell structure 300 may be four. For example, two LiCoO2 battery cells may be layered in a first row, and two LiCoO2 battery cells may be layered in a second row parallel to the first row.
In one embodiment of the present disclosure, the battery cells may include LiMn2O4 cells, and the number of battery cells within an example LiFePO4 battery cell structure 300 may be four. For example, two LiMn2O4 battery cells may be layered in a first row, and two LiMn2O4 battery cells may be layered in a second row parallel to the first row.
In another embodiment of the present disclosure, the battery cells may include LiNiMnCoO2 cells, and the number of battery cells within an example LiFePO4 battery cell structure 300 may be four. For example, two LiNiMnCoO2 battery cells may be layered in a first row, and two LiNiMnCoO2 battery cells may be layered in a second row parallel to the first row.
In one embodiment of the present disclosure, the battery cells may include LiNiCoO2 cells, and the number of battery cells within an example LiFePO4 battery cell structure 300 may be four. For example, two LiNiCoO2 battery cells may be layered in a first row, and two LiNiCoO2 battery cells may be layered in a second row parallel to the first row.
In another embodiment of the present disclosure, the battery cells may include LiNiCoAlO2 cells, and a number of battery cells within an example LiFePO4 battery cell structure 300 may be four. For example, two LiNiCoAlO2 battery cells may be layered in a first row, and two LiNiCoAlO2 battery cells may be layered in a second row parallel to the first row.
Each of the plurality of battery cells 704 may have a nominal voltage. The plurality of battery cells 704 may have a combined nominal voltage. In one embodiment, the nominal voltage for a LiFePO4 battery cell may be 3.2V. The battery module 700 with five LiFePO4 battery cells 704 may have a combined nominal voltage of 16 V. The nominal voltage of a battery module in the related art (e.g., Ni-MH-based battery module 200 in
To preserve the longevity of the lithium battery cells of the present disclosure, a voltage threshold is set by the voltage balancing module (e.g., 510) that is lower than the maximum charging voltage for each lithium battery cell. To promote energy efficiency of the lithium battery cells of the present disclosure, it is preferred that the voltage threshold set by the voltage balancing module (e.g., 510) is higher than the nominal voltage of each lithium battery cell. When the voltage balancing module detects that the voltage threshold is reached for any individual battery cell, the excessive energy of the battery cell is dissipated. The prevention of overcharging or charging to saturation of each individual battery cells may maintain an overall balanced state.
In one embodiment, the nominal voltage may be set slightly higher than the designed nominal voltage such that a processor in an HEV may determine a presence of excessive battery power, which may promote electrical power usage over combustion power usage, thus contributing to an increase in fuel economy while providing faster acceleration.
Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, especially in matters of shape, size, and arrangement of the parts within the principles of the present disclosure, up to and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the claims.