Patent Application
20170054128
The present disclosure relates to traction battery assemblies for hybrid and fully electric vehicles, and specifically to battery assemblies having cells with a thermocouple disposed on an outer surface of the cell.
The need to reduce fuel consumption and emissions in automobiles and other vehicles is well known. Vehicles are being developed that reduce reliance or completely eliminate reliance on internal-combustion engines. Electrified vehicles are one type of vehicle currently being developed for this purpose.
Electrified vehicles contain a traction battery assembly to act as an energy source for the vehicle. The traction battery may include components and systems to assist in managing vehicle performance and operations. The traction battery may also include high-voltage components, and may include an air or liquid thermal management system to control the temperature of the battery.
According to one embodiment, a traction battery includes a plurality of cells arranged in an array and each having a pouch with an outer surface. The traction battery also includes a circuit board having terminal receptacles. A thermal couple is disposed on the outer surface of one of the cells, and includes first and second legs each formed of a metal film. Each of the legs has a terminal extending away from the pouch and inserted into one of the terminal receptacles.
According to another embodiment, a traction battery includes a cell array with at least one cell having a pouch defining a tab extending therefrom. A thermal couple is disposed on the pouch, and includes first and second legs formed of a metal film. A terminal portion of the first leg is disposed on the tab.
According to yet another embodiment, a method of applying a thermal couple to a cell having a pouch, the method includes applying a first ink, having a first metal powder, to an outer surface of the pouch. The method also includes applying a second ink, having a second metal powder, to the outer surface such that the first and second inks connect at a junction. The first and second metal powders are dissimilar metals configured to produce a thermoelectric (or Seebeck) effect.
Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized 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. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.
A fraction battery or battery pack 24 stores energy that can be used by the electric machines 14. The fraction battery 24 typically provides a high voltage direct current (DC) output from one or more battery cell arrays, sometimes referred to as battery cell stacks, within the traction battery 24. The battery cell arrays may include one or more battery cells.
The battery cells (such as a prismatic, pouch, cylindrical, or any other type of cell), convert stored chemical energy to electrical energy. The cells may include a housing, a positive electrode (cathode) and a negative electrode (anode). An electrolyte may allow ions to move between the anode and cathode during discharge, and then return during recharge. Terminals may allow current to flow out of the cell for use by the vehicle.
Different battery pack configurations are available to address individual vehicle variables including packaging constraints and power requirements. The battery cells may be thermally regulated with a thermal management system. Examples of thermal management systems include air cooling systems, liquid cooling systems, and a combination of air and liquid systems.
The traction battery 24 may be electrically connected to one or more power electronics modules 26 through one or more contactors (not shown). The one or more contactors isolate the traction battery 24 from other components when opened, and connect the traction battery 24 to other components when closed. The power electronics module 26 may be electrically connected to the electric machines 14 and may provide the ability to bi-directionally transfer electrical energy between the traction battery 24 and the electric machines 14. For example, a typical traction battery 24 may provide a DC voltage while the electric machines 14 may require a three-phase alternating current (AC) voltage to function. The power electronics module 26 may convert the DC voltage to a three-phase AC voltage as required by the electric machines 14. In a regenerative mode, the power electronics module 26 may convert the three-phase AC voltage from the electric machines 14 acting as generators to the DC voltage required by the traction battery 24.
In addition to providing energy for propulsion, the traction battery 24 may provide energy for other vehicle electrical systems. A typical system includes a DC/DC converter module 28 that converts the high voltage DC output of the traction battery 24 to a low voltage DC supply that is compatible with other vehicle components. Other high-voltage loads, such as air conditioning compressors and electric heaters, may be connected directly to the high-voltage supply without the use of a DC/DC converter module 28. In a typical vehicle, the low-voltage systems may be electrically connected to the DC/DC converter or an auxiliary battery 30 (e.g., a 12 volt battery).
A battery energy control module (BECM) 33 may be in communication with the traction battery 24. The BECM 33 may act as a controller for the traction battery 24 and may also include an electronic monitoring system that manages temperature and charge state of each of the battery cells. The traction battery 24 may have a temperature sensor 31 such as a thermistor or other temperature gauge. The temperature sensor 31 may be in communication with the BECM 33 to provide temperature data regarding the traction battery 24.
The vehicle 12 may be recharged by an external power source 36. The external power source 36 may be the power grid or may be a local power source (e.g. solar power). The external power source 36 is electrically connected to a vehicle charging station 38. The charger 38 may provide circuitry and controls to regulate and manage the transfer of electrical energy between the power source 36 and the vehicle 12. The external power source 36 may provide DC or AC electric power to the charger 38. The charger 38 may have a connector 40 for plugging into a charge port 34 of the vehicle 12. The charge port 34 may be any type of port configured to receive power from the charger 38. The charge port 34 may be electrically connected to an on-board power conversion module 32. The power conversion module 32 may condition the power supplied from the charger 38 to provide the proper voltage and current levels to the fraction battery 24. The power conversion module 32 may interface with the charger 38 to coordinate the delivery of power to the vehicle 12. The connector 40 may have pins that mate with corresponding recesses of the charge port 34. In other embodiments, the charging station may be an induction charging station. Here, the vehicle may include a receiver that communicates with a transmitter of the charging station to wirelessly receive electric current.
The various components discussed may have one or more controllers to control and monitor the operation of the components. The controllers may communicate via a serial bus (e.g., Controller Area Network (CAN)) or via dedicated electrical conduits. The controller generally includes any number of microprocessors, ASICs, ICs, memory (e.g., FLASH, ROM, RAM, EPROM and/or EEPROM) and software code to co-act with one another to perform a series of operations. The controller also includes predetermined data, or “look up tables” that are based on calculations and test data, and are stored within the memory. The controller may communicate with other vehicle systems and controllers over one or more wired or wireless vehicle connections using common bus protocols (e.g., CAN and LIN). Used herein, a reference to “a controller” refers to one or more controllers.
Referring to
The cells 50 generate heat during charging and discharging of the battery 24. In order to properly control the battery 24, one or more vehicle controllers receive a signal indicating the temperature of the battery 24. Many prior art solutions determine an average temperature for the battery pack and use the average temperature as an input for the controller. These systems, at most, have a handful of sensors (typically thermistors) disposed in select areas. The problem with using an average battery temperature is that each of the cells may heat unequally and may have drastically different temperatures than other cells in the array. The various portions of individual cells 50 also heat unevenly. Typically, the cells 50 generate more heat towards the terminal side 62 than in other areas of the cell. To optimize battery operation and insure extended battery life, it is advantageous to have an accurate picture of the temperature the battery pack 24 and of each cell 50.
A thermocouple 64 may be used as a temperature sensor for the cells 50. In some embodiments, each cell within the array includes a thermocouple 64. In other embodiments, only some of the cells include a thermocouple 64. Thermocouples are inexpensive and have a small footprint compared to other temperature sensors currently being used. Because of this, a greater number of thermocouples may be included in the battery pack 24 as compared to other types of temperature sensors. The thermocouple 64 may be disposed on the outer skin 54 of one of the major sides 56. The thermocouple 64 includes a first leg 66 and a second leg 68 that are connected at a junction 70. The legs are also known as traces. The first and second legs are formed of dissimilar metals suitable to produce a thermoelectric effect (also known as the Seebeck effect). Suitable metal pairs include nickel-copper, chromel-constantan, chromel-alumel, iron-constantan, platinum-rhodium, copper-constantan and many others. The thermocouple 64 also includes a first terminal 72 connected to the first leg 66 and a second terminal 74 connected to the second leg 68. The first and second terminals 72, 74 are electrically connected to the controller either directly or indirectly.
The legs of the thermocouple 64 may be metal strips or wires, or may be a metallic film formed of dried ink or paint. The metallic film is electrically conductive and flexible. In one embodiment, each of the legs is formed of a metallic film that is painted, printed, or drawn onto the outer skin 54 of the pouch 52. The metallic ink or paint may be applied onto the pouch 52 via inkjet printing, screen printing, or applied by hand using a pen or paintbrush. The pouch 52 is a flexible, non-metallic, and non-conductive material such as aluminum-polymer laminate. The film must also be flexible and capable of binding to the outer skin of the pouch 52. A film thermocouple is extremely thin (orders of magnitude thinner than traditional thermocouples) and does not have a significant thickness footprint. As such, a larger number of film thermocouples can be used, as compared to other temperature sensors and wire or metal strip based thermocouples.
Each of the metallic inks or paints may be comprised of metal powder, a binder, and a solvent. The metal powder may be finely divided granules or may be thin flakes. The metal powder and the binder make up the dry ingredients of the ink and the solvent makes up the wet ingredient. The dry ingredients may be 79 to 99 percent metal powder and 1 to 21 percent binder, respectively, by dry weight.
The binder may be any film forming polymer. Potential binders include polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polyacrylonitrile (PAN), Polyvinyl acid (PVA), polyacrylic acid (PAA), and styrene butadiene rubber (SBR). The solvents may be volatile or nonvolatile. Potential solvents include n-methylpyrrolidone (NMP), water, alcohol, and acetone. The solvent may be a mixture of different solvents, such as a water-acetone mixture.
The ink or paint is manufactured by mixing together the dry ingredients and adding an effective amount of solvent to form a liquid phase that is capable of being printed or painted onto the pouch 52. The ink or paint is then dried to form a film. The ink or paint may be dried at room temperature or at an elevated temperature. The pouches are heat sealed; therefore any elevated-temperate drying must be performed at less than 200 degrees Celsius to prevent damaging the seams.
The first and second terminals 72, 74 may also be formed of a metallic film or may be a strip of metal. In one embodiment, illustrated in
In another embodiment, illustrated in
In one embodiment, the tab is a sacrificial substrate used to support the ink until it dries. Once the ink dries, the sacrificial tab is removed leaving a terminal formed of the film (i.e. dried ink). Additional coatings of ink maybe applied in the terminal portion of the legs to incrcase the strength of the film terminal. The sacrificial tab may be made of wax, Teflon®, or any other structure that is removable without damaging the film terminal.
The thermocouple 64 is disposed on the outer skin 54 in an area where a temperature reading is desirable. The cells 50 typically produce the maximum amount of heat near the terminal side 62. Therefore, it may be desirable to place the thermocouple junction there as shown in
One or more of the cells 50 includes a thermocouple, such as thermocouple 64. The traction-battery assembly 24 may include one or more lead wires (not shown) that connects with the terminals of the thermocouple to electrically connect the thermocouples to one or more of the vehicle controllers. In order to provide more efficient packaging, the lead wires may be replaced with a printed circuit board that electrically connect with each of the thermocouples and one or more of the vehicle controllers.
The printed circuit board may be a separate component or may be integrated with the control board 106.
The control board 116 includes cell-terminal receptacles 128 that are each configured to receive one of the cell terminals 120. The control board 116 also includes thermocouple receptacles 130 that are each configured to receive one of the first or second terminals 124, 126 of thermocouple 122. The receptacles 130 include one or more electrical contacts for electrically connecting with the terminals 124, 126.
In another example, the thermocouple is applied to the pouch after the electrochemical components of the cell are completely manufactured. Here, the pouch may be roughened at a location where the thermocouple is being installed. Next, the first and second inks are applied as described above.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.
