Claims:We claim:

1. A battery pack having a plurality of battery cells as cell stack and equipped with a temperature control mechanism for maintaining said battery pack within a safe operational temperature range, wherein a plurality of thermal pads is disposed within said battery pack for providing cell to cell insulation between battery cells thereof.

2. Battery pack as claimed in claim 1, wherein said battery pack comprises at least two battery cells.

3. Battery pack as claimed in claim 2, wherein said battery cells are in a sealed cell configuration and/or comprise different form factors.

4. Battery pack as claimed in claim 1, wherein said mechanism is based on Peltier effect and configured to maintain said battery pack within an optimum temperature range, by removing excess heat therefrom or by heating said battery pack during extremely low temperature conditions.

5. Battery pack as claimed in claim 1, wherein said thermal pads are made of thermo-electric and/or phase change material, said thermal pads having good compression strength and high thermal conductivity.

6. Battery pack as claimed in claim 1, wherein said thermal pads are made as compression pads for ensuring the structural rigidity of said battery pack.

7. Battery pack as claimed in claim 6, wherein said compression pads comprise multiple thermoelectric materials localized therein to be selectively activated for heat removal to maintain a uniform temperature across said battery cells.

8. Battery pack as claimed in claim 7, wherein said compression pads are made of solid state or NP type dissimilar metals or semiconductors.

9. Battery pack as claimed in claim 1, wherein said thermal pads are operated in an active mode and/or in a passive mode.

10. Battery pack as claimed in claim 7, wherein in an active mode, each of said thermal pads is configured as a solid-state device having thermo-electric property, preferably a semiconductor to heat or cool said battery cells based on Peltier effect.

11. Battery pack as claimed in claim 7, wherein in a passive mode, each of said thermal pads is composed of a phase change material to absorb or release heat based on the need for cooling or heating said battery cells.

12. Battery pack as claimed in claim 9, wherein at least one of said thermal pads, is disposed at the respective end of the cell stack of said battery cells.

13. Battery pack as claimed in claim 9, wherein at least one battery cell is disposed between each pair of said thermal pads.

14. Battery pack as claimed in claim 9, wherein a predetermined number of battery cells are disposed between each pair of said thermal pads.

15. Battery pack as claimed in claim 10, wherein at least two battery cells are disposed between said thermal pad pairs are disposed enclosing a predetermined number of said cells.

16. Battery pack as claimed in claim 8, wherein said temperature control mechanism is configured as a temperature control circuit comprising:

• said battery cells in contact with said thermal pads;

• an external power supply;
• a temperature control module to measure temperature of said battery cells;

• a controller to activate said temperature control circuit;

• a first switch for powering said thermal pads by battery cell pack; and

• a second switch for powering said thermal pads by external power supply;

wherein the closing of either switch powers said thermal pads for heating or cooling the interface between each of said battery cells and thermal pads.

17. Battery pack as claimed in claim 7, wherein said thermal pads are operated in a dual temperature control mode.

18. Battery pack as claimed in claim 7, wherein said thermal pads are made of a material having both thermo-electric and phase change properties, wherein the passive temperature control mode is operational in the shut-down mode of said battery pack and the active temperature control mode is operational on powering up the battery pack, whereby the power requirement and temperature control is optimized.

19. Battery pack as claimed in claim 7, wherein a predetermined number of said thermal pads are configured with thermo-electric properties and/or phase change properties and the remaining thermal pads are configured as compression pads and/or to provide cell to cell insulation.

20. Battery pack as claimed in claim 1, wherein said thermal pads are configured for use with another thermal management system such as active/passive air cooling or liquid cooling for controlling the temperature of said battery pack.

Dated this 02nd day of March 2019. Digitally Signed.
(SAJAY KESHARWANI)
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention concerns a battery pack having multiple cells. In particular, the present invention relates to the cell to cell insulation in a battery pack. More particularly, the present invention relates to thermal pads used for providing cell to cell insulation in a battery pack.

BACKGROUND OF THE INVENTION

Lithium-ion batteries are the most widely used energy storage devices in electrical drivetrains of the automotive such as the hybrids, plug-in hybrids and the battery electric vehicles. These battery packs are often exposed to harsh usage patterns such as aggressive driving, fast/ultra-fast charging and extreme temperature conditions. Such usage patterns and such operating conditions induce significant thermal stress in the battery cells, which lead to substantially faster degradation of the battery performance and/or deterioration of the operational life thereof.

Therefore, it is crucial to maintain these battery packs within optimum temperature range for harnessing the maximum storage potential thereof to realize a longer operational life.

PRIOR ART

US 6002240 A, titled- “Self-heating of batteries at low temperatures” discloses a rechargeable battery pack that includes a controller, a temperature monitoring circuit, a rechargeable battery, and a heating circuit. This rechargeable battery pack can sense when it is exposed to a harmfully low temperature and cause the heating circuit to heat the battery pack, particularly the battery pack's controller, so that it remains in a temperature regime compatible with normal operation. The rechargeable battery has a positive terminal and a negative terminal. The heater circuit is coupled to the rechargeable battery and the controller is coupled to the heater circuit. The temperature monitoring circuit is coupled to the controller. The temperature monitoring circuit is capable of measuring a temperature of the battery pack and providing a temperature indication, based on which the controller causes the heater circuit to heat the controller. This publication explains the use of a heater circuit (thermistor) that uses the power from the rechargeable battery pack for heating it to operational temperature level.

US 9509152 B2, titled- “Method and apparatus for self-heating of a battery from below an operating temperature” discloses a method and apparatus for a self-heating battery pack using battery cells of a first battery cell circuit to power a device. However, these battery cells become substantially inoperative below a very cold temperature, so a second battery cell circuit having a second type of battery cells which can operate at the cold temperature, is used to power a heating element to warm up the first battery cells to a temperature at which they can operate. The apparatus consists of a heating circuit with a secondary battery cell which heats the primary battery pack based on the input received by the temperature control unit. The heater circuit uses nichrome as the resistive heating element.

US 2008268333 A1, titled- “Integral battery thermal management” discloses an electrochemical battery having at least one self-contained thermoelectric cooling device such as a Peltier device, for cooling the battery to optimal operating conditions. The thermoelectric cooling device is contained within a housing of the battery and is in proximity to cells contained within the housing with the cooling device being electrically connected to the cells of the battery and an external electrical power source. A switching element is configured to selectively power the thermoelectric cooling device from the external electrical power source and on shutting down the external electrical power, the switching element redirects power from the battery to the thermoelectric cooling device to continuously cool the battery.
US 8936864 A1, titled- “Batteries with phase change materials” discloses a battery pack with phase change materials (PCM), which improve the heating and cooling capabilities under various vehicle operating conditions. It also describes the methods of controlling the temperature in battery packs and explains the usage of foam type compressible isolator sheets in addition to air/liquid cooling. These isolator sheets are made of phase change materials and can be placed either in direct contact with the cells or cooling fins.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide thermal pads used in battery packs for cell to cell insulation therein.

Another object of the present invention is to provide thermal pads used in battery packs for cell to cell insulation, which act as compression pads.

Still another object of the present invention is to provide thermal pads used in battery packs for cell to cell insulation for ensuring structural rigidity thereof.

Yet another object of the present invention is to provide thermal pads used in battery packs for cell to cell insulation, which can be effectively used for cooling or heating the battery cells by controlling the temperature thereof.

A further object of the present invention is to provide thermal pads used in battery packs for cell to cell insulation, which can function in different modes.

A still object of the present invention is to provide thermal pads used in battery packs for cell to cell insulation, which can help in thermal management of the battery cells without any additional devices.
A still object of the present invention is to provide thermal pads used in battery packs for cell to cell insulation, which are low-cost, accurate and easy to implement.

A yet further object of the present invention is to provide thermal pads used in battery packs for cell to cell insulation, which do not change the form factor of the battery pack.

These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of drawing, which are however not intended to limit the scope of the present invention in any way.

SUMMARY OF INVENTION

In accordance with the present invention, there is provided a battery pack having a plurality of battery cells as cell stack and equipped with a temperature control mechanism for maintaining said battery pack within a safe operational temperature range, wherein a plurality of thermal pads is disposed within said battery pack for providing cell to cell insulation between battery cells thereof.

Typically, the battery pack comprises at least two battery cells.

Typically, the battery cells are in a sealed cell configuration and/or comprise different form factors.

Typically, the mechanism is based on Peltier effect and configured to maintain said battery pack within an optimum temperature range, by removing excess heat therefrom or by heating said battery pack during extremely low temperature conditions.

Typically, the thermal pads are made of thermo-electric and/or phase change material, said thermal pads having good compression strength and high thermal conductivity.

Typically, the thermal pads are made as compression pads for ensuring the structural rigidity of said battery pack.

Typically, the compression pads comprise multiple thermoelectric materials localized therein to be selectively activated for heat removal to maintain a uniform temperature across the battery cells.

Typically, the compression pads are made of solid state or NP type dissimilar metals or semiconductors.

Typically, the thermal pads are operated in an active mode and/or in a passive mode.

Typically, in an active mode, each of said thermal pads is configured as a solid-state device having thermo-electric property.

Typically, in a passive mode, each of said thermal pads is composed of a phase change material to absorb or release heat based on the need for cooling or heating said battery cells.

Typically, at least one of said thermal pads, is disposed at the respective end of the cell stack of said battery cells.

Typically, at least one battery cell is disposed between each pair of said thermal pads.

Typically, a predetermined number of battery cells are disposed between each pair of said thermal pads.
Typically, at least two battery cells are disposed between said thermal pad pairs are disposed enclosing a predetermined number of said cells.

Typically, the temperature control mechanism is configured as a temperature control circuit comprising:
• said battery cells in contact with said thermal pads;

• an external power supply;

• a temperature control module to measure temperature of said battery cells;

• a controller to activate said temperature control circuit;

• a first switch for powering said thermal pads by battery cell pack; and

• a second switch for powering said thermal pads by external power supply;
wherein the closing of either switch powers said thermal pads for heating or cooling the interface between each of said battery cells and thermal pads.

Typically, the thermal pads are operated in a dual temperature control mode.

Typically, the thermal pads are made of a material having both thermo-electric and phase change properties, wherein the passive temperature control mode is operational in the shut-down mode of said battery pack and the active temperature control mode is operational on powering up the battery pack, whereby the power requirement and temperature control is optimized.

Typically, a predetermined number of said thermal pads are configured with thermo-electric properties and/or phase change properties and the remaining thermal pads are configured as compression pads and/or to provide cell to cell insulation.

Typically, the thermal pads are configured for use with another thermal management system such as active/passive air cooling or liquid cooling for controlling the temperature of said battery pack.
Although the present invention mostly concerns the use of thermal pads for prismatic lithium-ion battery cells, the invention can also be implemented for batteries using a wide range of chemistry with sealed cell design and cells with different form factors.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described in the following with reference to the accompanying drawings.

Figure 1a shows thermal pads placed either at the end of the cell stack having a plurality of cells therein.

Figure 1b shows thermal pads alternatively placed on either side of the adjoining cells of the cell stack.

Figure 1c shows thermal pads placed at a predefined interval between the cells of the cell stack.

Figure 2 shows a schematic arrangement of an active temperature control based on Peltier effect.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, the thermal pads configured in accordance with the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention.

The thermal pads in accordance with the present invention can be arranged as shown in Figures 1a-c, which primarily illustrate a passive mode of temperature control, in which the thermal pads are composed of phase change material. Here, the thermal pads can be placed at different locations within the cell stack depending on the requirement of compression and thermal load management.
These thermal pads / Phase Change Material / barrier could also be configured as localized dynamic thermal pads, for example, having multiple thermo-electric materials localized within the compression pad and only those being activated, which effectively remove the heat and maintain a uniform temperature across the battery cell. It is preferred that thermal pads are of solid state or NP type dissimilar metals or semiconductors.

Figure 1a shows thermal pads 102 placed either at the end of cell stack 100 having a plurality of cells 1001, 1002, 1003, 1004, 1005 etc. for implementing a passive mode of temperature control.

Figure 1b shows thermal pads 102 alternatively placed on either side of the adjoining cells 1011, 1012, 1013 of the cell-stack 100 for implementing a passive mode of temperature control.

Figure 1c shows thermal pads placed at a predefined interval between the group 1020 of cells 1021, 1021, 1023 and 1031, 1031, 1033 and group 1030 of cells 1031, 1032, 1033 of the cell-stack 100 for implementing a passive mode of temperature control. However, the packaging architectures shown in Figures 1a-c can also be used in active temperature control mode, discussed below with respect to Figure 2.

Figure 2 shows a schematic arrangement of an active temperature control based on Peltier effect. Here, the temperature control is based on thermo-electric property of the thermal pad 102. The battery cell 101 is kept in contact of the thermal pad 102. The temperature control module 106 measures the cell temperature and feeds it to the controller 107. The controller 107 can either be an additional functionality of the battery management system or a standalone system. If the cell temperature rises above or falls below the recommended operational temperature range, the controller 107 activates the temperature control circuit by either closing the switch 104 or switch 105. On closing the switch 104 the thermal pad 102 is powered by the battery cell 101, whereas on closing the switch 105 the thermal pad 102 is powered by the external power supply 103. On closing the circuit, current flows through the thermal pad 102 thereby heating or cooling the battery cell – thermal pad interface 108 based on Peltier effect.

WORKING MODES OF THE INVENTION

The packaging options are however not limited to the ones disclosed herein and several other options both in terms of arrangement of the thermal pads within the cell stack as well as orientation are possible based on the requirement and feasibility. Therefore, the thermal pads according to the present invention can be configured in several architectures for facilitating thermal management of the battery cells as discussed below:

Active temperature control mode involves thermal pads composed of thermo-electric material to regulate the battery temperature based on the Peltier effect. Here, depending on the cell temperature input supplied to the controller by the temperature sensing module, the temperature control circuit is activated when the cell temperature is above or below the optimum temperature range. The voltage is applied across the thermal pad for cooling or heating up its interface with the battery cell and the thermal pad thus heats up or cools the battery cell, as required. In this operational mode, the thermal pad is powered either by the battery cell itself or an external power source as decided by the controller based on the state of charge (SOC) of the battery pack and depending on the availability of an external power supply connected thereto.

Passive temperature control mode involves thermal pads composed of a phase change material to absorb the additional heat generated by the battery cells during high temperature operation or under other aggressive usage conditions. The phase change materials are very effective in storing large amounts of heat and release this stored energy for heating up battery cells in low temperature conditions, when the ambient drops below a predetermined temperature. This mode of thermal management is much easier and more economical to be implemented, since it depends only on the property of the thermal pad material and doesn’t require any additional circuitry. Moreover, it does not consume any power. Therefore, this mode is particularly effective in low voltage systems, in which predominantly passive air cooling is used.

Dual temperature control mode involves the possibility of implementing both above modes, i.e. active as well as passive temperature control mode in the same battery pack.

Hybrid temperature control mode alternatively provides the thermal pads to be constructed of a material having both thermo-electric and phase change properties. In this configuration, the passive temperature control mode is operational when the battery pack is in shut-down mode and the active temperature control mode becomes operational on powering up the battery pack. This configuration can optimize the power requirement and temperature regulation.

Selective temperature control mode offers different packaging options of the thermal pads depending upon the heat load and compression requirement as discussed with reference to Figures 1a-c. It is also possible to configure only a selected number of thermal pads with thermo-electric and/or phase change properties and the remaining thermal pads are configured only for compression and/or insulation purpose.

Primary or Supplementary temperature control mode makes it possible to use the thermal pads either as the only means of temperature regulation of the battery pack or to use the thermal pads in addition to another thermal management system such as the active/passive air cooling or liquid cooling.
Since maintaining the lithium-ion battery packs within a safe operational temperature range is very crucial for optimum performance and operational life thereof. The cost and complexity of the thermal management strategy varies greatly depending on the thermal load to be removed. The most widely used thermal management techniques are either passive air cooling or active cooling by using air, liquid coolant or refrigerant. However, thermal management can also be done at cell level by using thermo-electric or phase change materials.

The thermal pads configured according to the present invention can perform multifold functionalities by providing cell to cell insulation barrier, required compression for maintaining the structural rigidity as well as thermal management of the battery pack.

The thermal pad architecture is devised such that depending upon the heating or cooling requirements, several different architectures can be offered. The inventive thermal pad can be used both in active and passive modes.

In active mode, the thermal pad is primarily a solid-state device having thermo-electric property, preferably a semiconductor that heats or cools the battery cell based on Peltier effect. Based on the voltage applied to the thermal pad a current flows therethrough for heating or cooling the thermal pad - battery cell interface connected thereto. The thermal pad can draw power either from the battery cell which is heating or cooling the same; or it can draw power from an external power source.

In passive mode, the thermal pad is composed of phase change material which can absorb, or release heat based on whether the cells are required to be heated or cooled. The passive mode is completely an autonomous event, without requiring any additional circuitry. In both active and passive modes, the thermal pads need to have good compression strength and high thermal conductivity.
The thermal pad configured in accordance with the present invention are easily configured for controlling the cell temperature. The thermal pads can be made with different architectures depending on the thermal load to be managed thereby. It uses solid state devices having high system reliability by eliminating leakage of cooling fluids (no working fluids used). This new configuration of battery packs having thermal pads does not increase the size and form factor of the battery pack as the same unit acts as insulation barrier and compression pad as well as helps in heating/cooling of the thermal pads.

This arrangement does not require any moving parts, so is noise-free. It has a modular arrangement which is easy to service. It is low-cost and consumes less power as compared to any other active battery cell cooling method. Different cell chemistries with sealed cell design and different form factors can be used.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The thermal pad architecture configured in accordance with the present invention offers the following advantages:

- Easy to implement and control temperature.

- Made with different architectures based on the thermal load to be managed.

- Uses solid state devices having high system reliability.

- Leakage of cooling fluids eliminated as no working fluids are used.

- No increase in size and form factor of battery pack module.

- Involves no moving parts, thus does not generate any noise.

- Involves a modular arrangement and thus easy to service.

- Low-cost and low-power consumption.

- Different cell chemistries with sealed cell design and form factors possible.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

It is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention.

Although, the embodiments presented in this disclosure have been described in terms of its preferred embodiments, the skilled person in the art would readily recognize that these embodiments can be applied with modifications possible within the spirit and scope of the present invention as described in this specification by making innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies and assemblies, in terms of their size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.

The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.
Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to imply including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention.