Patent Application
20200259227
Most batteries, including lithium batteries, operate best in a relatively narrow temperature range. For example, within lithium batteries, as the battery temperature falls below 0° C. not only does the internal resistance increase, but other properties of the battery cause discharging to become difficult if not impossible. At the same time, charging the battery becomes nearly impossible without causing permanent damage to the battery. As temperature rises the ability of the battery to discharge stored energy is restored and yet a battery temperature above 40° C. has a detrimental effect on the life of the battery.
These temperature sensitivities are of special concern when lithium batteries are employed in vehicles which must work in a wide range of ambient conditions. For example, within Finland an electric vehicle could be exposed to temperatures below −40° C. and within a more arid desert region the temperature may exceed +65° C. Exposing batteries to such temperature extremes becomes of even greater concern when the battery is subjected to a high charge or discharge rate while also exposed to such extreme ambient conditions. These extreme ambient conditions can be exacerbated by the internal heat which is generated by a battery during charging and discharging due to the battery's internal resistance.
Additionally, while internal resistance varies based on battery type, it also varies due to the internal battery temperature. Depending on the temperature of the battery this internal resistance can cause as much as a 10% energy loss. In some cases, such as when there is a high current demand and the battery temperature is cold, losses may even exceed 10%. In certain cases, a further problem is experienced when the battery is so cold that the internal resistance is high enough to prevent discharging entirely. This can be caused, for example, by a battery management system (BMS) sensing a low voltage on the cell due to increased internal resistance and preventing discharge of the battery.
Given the issues with cold ambient conditions impacting battery performance it is often preferable to thermally isolate the battery. In cold conditions this allows the waste heat produced by the battery to maintain the temperature of the battery and due to the high specific thermal capacity of the battery, the battery cools quite slowly when sufficiently isolated. This allows for the battery to maintain a preferable temperature even when left unused for a period of time in a cold climate. In colder climates this thermal isolation means that the vehicle and battery do not need to be heated as often in order to maintain conditions for daily use. However, this same thermal isolation that provides better performance in colder conditions makes it much more difficult to cool the battery when needed.
Within vehicles employing lithium batteries liquid cooling is typically employed. In such cases heat is dissipated through the battery case via conduction to the liquid cooling system. In other cases convection is employed to cool the battery by supplying cool air to the battery case. Both of these systems suffer in that the transfer of heat from inside of the battery is very inefficient. As such the cooling systems need to be oversized for the amount of thermal transfer that is actually taking place. Additionally, the cooling systems presently employed can have a negative impact on the reliability of the battery, in extreme cases, liquid coolant may leak and destroy the battery.
In order to avoid damage to batteries employed in a wide range of ambient temperatures an increase the life and efficiency of batteries a new temperature management solution is needed.
Additionally, many solutions are developing which utilize a single cell battery, greatly simplified battery packs or capacitors in order to provide electric power. The benefits of such solutions are varied, but such solutions often provide a lower voltage as a source and thus must source a great deal of current in order to deliver the same energy as a higher voltage source. This higher output current necessitates larger contact terminals.
At the same time having a plurality of batteries within the same housing leads to many thermal management issues. For example, within standard battery packs having numerous cells connected in series, thermal management becomes increasingly difficult by any known means. In order to manage the thermal condition of each cell a heat exchanger would need to have access to each individual cell resulting in a complex and expensive thermal management system. Additionally, individual cell thermal management would require complex isolation for the thermal management system to avoid inadvertently shorting the cells and causing damage to the battery in addition to a rise of fire. Finally, differences in temperature of the individual cells would result in poor battery performance and thus necessitate a thermal system that can somehow insure even heat distribution, further complicating any management system.
As discussed above many batteries employ large terminals. Not only do these terminals provide a source of electrical energy but they also provide an excellent thermal pathway to the inside of the battery. The present invention provides for improved thermal management of electric energy sources by utilizing the terminals of the source to remove and add thermal energy.
The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.
According to a first aspect of the present invention, there is provided an electric power source equipped with a thermal control system comprising: an electric power source having at least two terminals for supplying electric current; and at least one heat exchanger affixed to a surface of at least one of at least one of the two terminals.
According to a second aspect of the present invention, there is provided a combination electric motor drive and thermal control system for an electrical energy source comprising: an electric motor drive configured to adapt energy sourced from an attached electrical energy source for use by an attached electric motor; and a thermal control system comprising at least one heat exchanger configured to be in thermal contact with at least one terminal of the attached electrical energy source.
According to a third aspect of the present invention, there is provided a multi-cell battery pack having an integrated thermal management system comprising: a plurality of battery cells, a negative conductor connecting the negative poles of the batteries, a positive conductor connecting the positive poles of the batteries, and a heat exchanging element affixed and thermally connected to at least one of the negative conductor and positive conductor.
Definitions
In this context, temperature management refers to the heating, cooling and temperature maintenance.
As discussed herein a battery or other energy source is used as a description for an electrical energy source. It should be understood that many items can be employed as an electrical energy source.
As discussed herein an electric drive is a component which regulates or transforms the electric energy in order to control or supply a motor or other attached load.
As discussed herein a heat exchanging element is a component which is designed to efficiently transfer thermal energy. Examples of such elements include but are not limited to: radiators, heat sinks and other types of heat exchangers.
According to the present invention, the heat transfer capacities of the terminals of a battery are employed in order to provide more efficient management of the internal battery temperature. A temperature management system according to the present invention may be coupled with a drive adapted for use with the attached battery.
Generally electric vehicles employ batteries consisting of tens or hundreds of cells connected in a variety of parallel and series orientations to form a battery pack. However, as discussed in Finnish Patent Application 20175422, it is possible to employ single cell batteries to power electric vehicles. In a similar vein it is possible to employ greatly simplified battery packs. Such battery packs generally have relatively large terminals in order to allow for the higher current loads associated with single cell and simplified battery packs.
As can be seen in
Within at least some rechargeable battery configurations there is a cylindrical casing formed of a conductor which acts as the negative pole of the battery, either for one large cell or as a common negative pole for a plurality of cells within the casing. Once again, this common pole allows for excellent thermal access to the cell or cells of the battery.
As can also be seen in
In at least some embodiments of the present invention the electrical energy source is a battery. Certain embodiments employ a single cell battery. Still other embodiments employ a single battery cell. Others, a multi-cell battery pack arranged in parallel.
Also illustrated within
In certain embodiments of the present invention there is a layer of electrically insulating material between the heat exchanger and the terminals or conductors. Wherein at least some embodiments utilize the heat exchanger itself as an electric conductor.
Within some embodiments of the present invention the heat exchangers are constructed from a material which is not electrically conductive, such as a plastic or composite material.
Within certain embodiments the heat exchangers comprise a heat exchanging element surrounding an electrically conducting element. For example the heat exchanger may be configured such that a conductive element is provided to connect to terminals of an electrical power source. This conductive element is then surrounded by a heat exchanging element such that installation of the heat exchanger on the electrical power source is much easier. A user would simply need to attach the combined heat exchanger and electrical conductor between the electrical power source and whatever they wished to power.
At least some electrical power sources according to the present invention further comprise a heating element configured to provide thermal energy to the heat exchangers. Certain power sources further comprise a pump for moving cooling fluid through the heat exchangers.
Also depicted within
Within certain embodiments of the present invention employing a controller, pumps and valves as illustrated in
Within at least some embodiments of the present invention employing a controller, pumps and valves as illustrated in
It at least some systems according to the present invention the thermal controller is an integral part of the electric drive.
Certain embodiments of the present invention contain a control system which monitors the temperature of the battery along with the temperature of the electric drive or connected power electronics. The control system then adjusts the thermal management system to optimize thermal flow between the components.
Within certain embodiments of the present invention involving a controller unit for the thermal control system the control unit comprises at least one memory and at least one processor. The controller unit is configured to store temperature sensor data indicative of the battery temperature along with corresponding vehicle performance data such as, for example, a vehicle speed or torque. This data can then be used for proactive control of the temperature management system. For example, within at least some embodiments of the present invention, if the battery is near the ideal operating temperature, the thermal management system may begin cooling operations when the vehicle's speed exceeds a certain threshold, even before the battery temperature has risen outside of the ideal range. For example, if the vehicle exceeds 80 km/h and the battery temperature is still below an upper temperature limit, the thermal system would already begin dissipating heat to ensure that the battery temperature does not exceed the upper temperature limit due to the increased load. Thus the thermal management system is able to compensate for the sudden increase in heat due to an increased draw of energy from the battery.
At least some embodiments of the present invention provide for a thermal management system which is configured to keep the battery at an ideal temperature for the present performance of the electric drive. For example, when employed within an electric vehicle in normal driving conditions, the thermal management system will ensure that the battery and electronics are at a temperature which minimizes resistive loses. Certain embodiments provide for supplying heat from electrical components, for example an electric drive, to cold battery in order to quickly raise the temperature of the battery and ensure efficient operation.
In at least some embodiments of the present invention the electric drive is programmed to operate at less than peak efficiency for a period of time in order to generate heat to warm the electric energy source. This may actually lead to greater efficiency overall as heating the energy source increases the efficiency of the source.
Within combined electric drive and thermal management systems according to the present invention the internal resistance of the battery and electrical components can be used to quickly raise the temperature of the battery. The fact that warm electronics experience higher internal resistance can also be used to more quickly increase the temperature of the battery by allowing the electronics to warm and thus provide their waste heat to the battery as described in the system below.
Within at least some embodiments the electric components or electric drive is allowed to operate at a higher than standard operating temperature in order to more quickly heat the battery, once the battery is at a desired operating temperature the electronics are cooled. In this matter total losses of the combined thermal and electric drive system can be minimized.
Heat exchangers according to the present invention which are configured to be affixed to primary conductors or terminals of a battery have the potential to be conductively connected to the battery. As such it is important to ensure that the heat exchangers are electrically isolated in some fashion. In certain embodiments this is accomplished through thermally conductive but electrically insulating material which is placed between the heat exchangers and the conductors or terminals. For example, KERATHERM® Softtherm® films are a group of high elastic ceramic filled foils. They are characterized by their extremely good compressibility, their optimum with good thermal conductivity and good electrical properties at the same time. In some embodiments the heat exchangers are energized and the thermal exchange means, for example tubes for cooling fluid, provide insulation, for example by constructing the tubes from a non-electrically conductive material.
Heat flow in
Within at least some embodiments of the present invention the negative terminal is employed for thermal management as a large variety of energy sources have better thermal access via the negative terminal for a variety of reasons. As discussed above, often the negative terminal for batteries is connected with the casing and thus in contact with more of the battery. This holds true for single cell batteries and battery packs wherein the individual cells having casings which are connected to the negative terminal. Further, within at least some sources, the negative terminal is copper and thus has a better thermal conductivity than an aluminum positive terminal.
While the other elements of the thermal management system such as cooling fluid pipes, radiators and a controller are not shown within
At least some embodiments of the present invention employing a multi-cell battery pack are constructed such that the case of the battery pack is in thermal contact with the negative terminals of the cells within the pack. For example the case may act as a common negative terminal for all of the individual batteries contained within the battery pack.
As seen contained within the optional housing 780 power electronics 750 comprising an electric drive are disposed on the heat exchanger via a circuit board 755. This circuit board provides connections to both the positive 712 and negative 714 terminals of the package 700. The package takes in electric energy from the terminals 712 and 714 and converts it via the power electronics 750 before outputting the electricity at the output terminals 752 and 754. This conversion could be, for example, raising the output voltage of a connected battery pack. The power electronics may also be employed to drive an electric motor.
As seen atop
The heat exchanger 721 illustrated within
In certain embodiments the heat exchangers are supplied directly on the contact terminals of the battery. In some embodiments the entire electric drive and thermal management system is incorporated so as to provide a single connected to the battery.
At least some embodiments of the present invention employ a heating element which can be used to supply thermal energy directly to the battery. In some embodiments the heating element warms cooling fluid which is supplied to the heat exchangers disposed on the terminals or primary conductors and thus raises the internal temperature of the battery. In certain embodiments the heating element is an external heater that receives outside energy such as an electrical connection that may also be used to charge a connected battery. In other embodiments the heating element may burn a fuel to provide heat.
At least some thermal management systems according to the present invention provide for heating of the battery when in a “parking mode”. For example when an electric vehicle is parked and connected to an outside energy source such as a charging outlined. In such situations the thermal management system using energy from this outside source to direct thermal energy to the battery. As discussed above this may be accomplished, for example, through the use of a heating element wherein an electrical heating element supplies thermal energy to the heat exchangers disposed on the battery terminals or primary conductors and thus warms the battery.
Certain embodiments of the present invention provide for a multi-cell battery pack having an integrated thermal management system. This system includes a plurality of battery cells, a negative conductor connecting the negative poles of the batteries, a positive conductor connecting the positive poles of the batteries, and a heat exchanging element affixed and thermally connected to at least one of the negative conductor and positive conductor. Within some embodiments the heat exchanging element acts as at least one of the negative conductor and positive conductor.
It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.
As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.
The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20175889 | Oct 2017 | FI | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FI2018/050729 | 10/10/2018 | WO | 00 |
