BATTERY SYSTEM INCLUDING A SELF-REGULATING COOLING SYSTEM

A battery system includes a power cell and a heat exchanger abutting the power cell. The heat exchanger includes a cooling medium reservoir, a heat exchange member, and a wicking structure disposed between the cooling medium reservoir and the heat exchange member. The wicking structure provides a fluid pathway from the cooling medium reservoir to the heat exchange member and from the heat exchange member to the cooling medium reservoir.

INTRODUCTION

The subject disclosure relates to battery systems and, more particularly, to a battery system including a self-regulating cooling system.

Power systems that include batteries generate heat when placed under load. Heat generation is related to battery power. That is, the more power provided by the battery, the greater the amount of heat created. Heat may have a detrimental effect on battery efficiency and/or battery life. Accordingly, removing the heat provides a benefit to battery operation. In some cases, fans are directed at the battery to create an air flow which acts as a heat exchange medium. While effective at certain temperatures, larger batteries, such as those used to power vehicles, generate more heat than can be efficiently carried away by the airflow.

Other cooling systems may employ a cooling fluid that is pumped, in a heat exchange relationship, through the battery. The cooling fluid typically passes through a heat exchanger that is arranged adjacent to battery cells. Such systems require a device, such as a pump, for motivating the cooling fluid through the heat exchanger. The pump is either run from the battery or is provided with a separate source of power. In either case, the need for the pump detracts from an overall efficiency of the battery. Accordingly, it is desirable to provide a system for removing heat from a battery that can accommodate larger heat demands without detracting from an overall efficiency of the power system.

SUMMARY

Disclosed is a battery system including a power cell and a heat exchanger abutting the power cell. The heat exchanger includes a cooling medium reservoir, a heat exchange member, and a wicking structure disposed between the cooling medium reservoir and the heat exchange member. The wicking structure provides a fluid pathway from the cooling medium reservoir to the heat exchange member and from the heat exchange member to the cooling medium reservoir.

In addition to one or more of the features described herein a support member extends between the cooling medium reservoir and the heat exchange member, the wicking structure being arranged on the support member.

In addition to one or more of the features described herein the support member is formed from aluminum.

In addition to one or more of the features described herein the wicking structure comprises a screen.

In addition to one or more of the features described herein the screen includes multiple screen segments extending between the cooling medium reservoir and the heat exchange member.

In addition to one or more of the features described herein a gap is defined between adjacent ones of the multiple screen segments.

In addition to one or more of the features described herein the gap defines a cooling medium return path.

In addition to one or more of the features described herein the wick structure is formed from sintered copper particles.

In addition to one or more of the features described herein another power cell is arranged adjacent the power cell, the heat exchange member being arranged between the power cell and the another power cell.

In addition to one or more of the features described herein the heat exchanger includes a first heat exchanger abutting the power cell and a second heat exchanger abutting the another power cell.

In addition to one or more of the features described herein an insulating member is arranged between the first heat exchanger and the second heat exchanger.

In addition to one or more of the features described herein a cooling medium is arranged in the cooling medium reservoir.

In addition to one or more of the features described herein the cooling medium comprises one of water and ammonia.

In addition to one or more of the features described herein the heat exchange member comprises one of a fin type heat exchange member and a cold plate heat exchange member.

Also disclosed is a method of removing heat from a battery system including placing a heat exchanger including a cooling medium reservoir against a power cell of a battery, flowing a cooling medium from the cooling medium reservoir toward a heat exchange member through a wicking structure, absorbing heat into the cooling medium, and removing the heat from the cooling medium in the heat exchange member.

In addition to one or more of the features described herein flowing the cooling medium includes urging the cooling medium through the wicking structure with a capillary force.

In addition to one or more of the features described herein placing the heat exchanger includes positioning a first heat exchanger against a first power cell and positioning a second heat exchanger against a second power cell, the first and second heat exchangers being disposed between the first and second power cells.

In addition to one or more of the features described herein insulating an interface between the first heat exchanger and the second heat exchanger.

In addition to one or more of the features described herein applying a compressive force to the first and second heat exchangers through the first and second power cells.

DETAILED DESCRIPTION

A battery system, in accordance with a non-limiting example, is indicated generally at10inFIG.1. Battery system10includes a first power cell14and a second power cell16. Each power cell14,16is designed to produce electrical energy. Power cells14and16may take on a variety of forms including lead-acid cells, lithium-ion cells, and the like. A heat exchange system20is disposed between first power cell14and second power cell16. As will be detailed more fully herein, heat exchange system20operates to remove heat produced by first power cell14and second power cell16.

Heat exchange system20includes a first heat exchanger24associated with first power cell14and a second heat exchanger26associated with second power cell16. First and second heat exchangers24and26are separated by a layer of thermal insulation30and thermally coupled to a heat exchange member38positioned on first and second power cells14and16. Heat exchange member38may take on various forms such as a fin-type, a fin and tube-type, a cold plate, and the like. Thermal insulation30is sandwiched between first and second heat exchangers24and26. Thermal insulation30reduces thermal transfer between first and second heat exchangers24and26.

Reference will now follow toFIGS.2and3in describing first heat exchanger24with an understanding that second heat exchanger26includes similar structure. First heat exchanger24includes a support member45having a first or upper end47and a second or lower end49. First end47is thermally connected to heat exchange member38. Support member45includes a first substantially planar surface52and an opposing second substantially planar surface54. Second substantially planar surface54abuts an outer surface (not separately labeled) of first power cell14. Support member45may be formed from a wide array of thermally conductive materials such as aluminum, copper, steel, or the like.

In a non-limiting example, first heat exchanger24includes a cooling medium reservoir60located at second end49and a wicking structure67disposed on first planar surface52. Cooling medium reservoir60contains a cooling medium such as water, ammonia, and the like. Wicking structure67is fluidically exposed to the cooling medium and thermally connected to heat exchange member38. Wicking structure67may take on a variety of forms such as, in the non-limiting example shown, a screen70or a layer of sintered copper. However other thermally conductive materials may also be employed. Further, wicking structure67may include a hydrophilic layer that promotes a wicking of the cooling medium from cooling medium reservoir60toward heat exchange member38.

In a non-limiting example, screen70is formed from multiple screen segments74a-74iextending across first substantially planar surface52. Screen segments74a-74iare separated by gaps78a-78hthat extend between heat exchange member38and cooling medium reservoir60. In a non-limiting example, when under load, (e.g., being used to produce power) heat generated by first and second power cells14and16flows into corresponding ones of first heat exchanger24and second heat exchanger26. The heat causes the cooling medium in cooling medium reservoir60to flow through wicking structure67toward heat exchange member38. More specifically, the heat from, for example, first power cell14may cause the cooling medium to evaporate and flow upwardly. Upon reaching heat exchange member38, the cooling medium may lose heat, liquify, and return to cooling medium reservoir60via gaps78a-78hunder force of gravity.

The amount and rate of flow of the cooling medium is proportional to the amount of heat produced by each power cell14. If, for example, one of the first and second power cells14,16undergoes a thermal runaway, any thermal energy released would cause all the fluid inside the wicking structure67and cooling medium reservoir to evaporate or undergo a “dry-out” condition. In such a case, heat exchange system20would effectively turn into an insulation layer that disrupts heat transfer to the other of first and second power cells14and16to stem a propagation of the thermal runaway into additional and/or neighboring power cells. As such, heat exchange system20is self-regulating. Further the use of a wicking medium and a return flow path negates the need for powered pumps or other structure that may reduce an overall efficiency of the battery system. Further, the particular design of the heat exchange system allows power cells to be compressed together, such as shown inFIG.3so as to increase heat exchange efficacy and reduce an overall footprint of the battery system.

While the above disclosure has been described with reference to non-limiting examples, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from its scope. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within the scope thereof.