Abstract:
An application for a battery pack that includes walls made of sturdy material, power interface terminals and battery cells/electronics held within the walls. A protective layer contains the battery cells. The protective layer reduces external harm from heat, out-gassing and/or explosion of one or more of the battery cells.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is related to patent application titled “BATTERY CUSHION AND INSULATOR,” Ser. No. 12/786,473, attorney docket 3037.0, inventor Steven Tartaglia, filed May 25, 2010 and patent application titled “BATTERY PACK THERMAL PROTECTION FROM HEAT STERILIZATION,” Ser. No. 12/789,597, attorney docket 3044.0. 
     
    
     FIELD 
       [0002]    This invention relates to the field of batteries and more particularly to a system for reducing damage from battery cells that burst, ignite and/or explode. 
       BACKGROUND 
       [0003]    Battery cells such as flooded lead-acid, absorbed-glass-matt (AGM), lead-acid, Nickel Cadmium (NiCd), Nickel Metal Hydride (NiMh) and the like perform best at certain temperature ranges and are easily damaged when shorted or exposed to very high temperatures. When such battery cells are exposed to certain high temperatures or are quickly discharged, various physical changes occur internal to the battery cells such as boiling of the electrolyte, etc. In an extreme case, such as boiling of the electrolyte, high pressure results within the sealed cell, leading to possible deformation of the outer case, deformation of the anode/cathode arrangements and, possible out-gassing or leakage of electrolyte, and possibly bursting or explosion. 
         [0004]    Newer, ecology minded technologies such as lithium ion (Li-ion) and Lithium Ion (Li Fe) normally provide enhanced use/charge cycles over prior technologies such as nickel cadmium, but are even more susceptible to issues related to high temperatures and fast discharge. In, for example, Lithium Ion battery cells, the thin Solid Electrolyte Interface (SEI) layer on the anode breaks down due to overheating caused by excessive currents, overcharging or high temperatures. The breakdown of the SEI layer starts to occur at the relatively low temperature of 80° C. Once the SEI layer is breached, the electrolyte reacts with the carbon anode at a higher, uncontrolled, temperature, creating an exothermal reaction which drives the temperature up still further. Therefore, it is important to assure that the core temperature of Lithium Ion cells remains well under 80° C., preferably under 75° C. and that the cells are not subject to over discharge rates such as shorting the anode to the cathode. 
         [0005]    There have been several instances in which it is possible or suspected that certain battery chemistries being shorted during transit ignited fires that resulted in extensive damage to, for example, a cargo plane. It has been speculated that Lithium Ion Personal Computer Batteries led to a fire on United Parcel Services Flight 1307, in Philadelphia, September of 2006. 
         [0006]    As one example, Lithium Ion batteries have very high energy densities. When Lithium Ion batteries are overheated or overcharged, the potential exists for thermal runaway and cell rupture, in extreme cases leading to combustion. A deep discharge of the cells often creates a short-circuit within the cell, after which, recharging would be unsafe. To reduce these risks, Lithium-ion battery packs some times contain circuitry that controls charge and discharge of the battery cells but such circuitry itself is subject to failure. In addition, when Lithium-ion battery packs are stored for long periods of time, the power drain of this circuitry will drains the battery cells below the minimum specified voltage for the cells. When a battery pack is inadvertently subject to high current draw, such as when the battery pack terminals are shorted during transportation, excessive current is capable of damaging the protection circuit, thereby enabling the battery pack to begin an exothermal reaction, possibly causing a fire within the carrier (e.g. airplane) that is further fed by other near-by battery packs. 
         [0007]    The individual cells are often required to have shut-down separators for over-temperature, tear-away tabs for internal pressures, pressure relief vents and thermal interrupt to prevent excessive current draw and to prevent overcharging. These circuits along with improved electrode designs reduce the risk of fire or explosion, but there still exists the potential of fire and/or explosion when such battery cells/packs are misused or exposed to unexpected events such as excessive heat, puncture, etc. 
         [0008]    The United Nations Department of Transportation (U.N.D.O.T.) Manual of Tests and Criteria, section 38.3 specifies various tests required to be passed in order to obtain U.N.D.O.T approval for transportation of Lithium based batteries. 
         [0009]    What is needed is a battery pack that reduces or eliminates the impact of a failure of one or more battery cells in a battery pack. 
       SUMMARY 
       [0010]    A battery pack is disclosed including a set of walls made of sturdy material, power interface terminals and battery cells/electronics held within the walls and within a protective layer. The protective layer reduces external harm from heat, out-gassing and/or explosion of one or more of the battery cells. 
         [0011]    In one embodiment, a battery pack is disclosed including an enclosure with one or more battery cells held within the enclosure. A protective layer is situated within the enclosure and encapsulates the battery cells. Connection terminals mounted on the enclosure are electrically accessible from outside of the enclosure and conduct electricity through the enclosure. Two or more conductors electrically connect a contact of the connection terminal with a terminal of one or more of the battery cells. The protective layer contains excess heat and forces created when one or more of the battery cells overheat, vent or explode. 
         [0012]    In another embodiment, a method of reducing damage resulting from battery cell failure is disclosed including providing one or more battery cells. The battery cells are surrounded in surrounding the battery cells in a protective layer and are electrically interfaced to connection terminals by a plurality of interconnecting conductive paths that pass through the protective layer. The battery cells and the protective layer are capsulated in an enclosure, the connection terminals pass through the enclosure, thereby providing power accessible from outside of the enclosure. The protective layer reduces external harm from heat, out-gassing and/or explosion of one or more of the battery cells. 
         [0013]    In another embodiment, a battery pack is disclosed including an enclosure that holds two or more battery cells. Conductive paths interconnect battery terminals of the battery cells in series, parallel or series-parallel configurations. A protective layer is disposed within the enclosure and encapsulates the battery cells. Connection terminals that are electrically accessible from outside of the enclosure conduct electricity from the battery cells within the enclosure. Two or more conductors conduct electricity between contacts of the connection terminal with terminals of one or more of the battery cells or connect the terminals of one or more of the battery cells with other terminals of one or more of the battery cells. A dampening layer is disposed between the protective layer and the enclosure. The protective layer contains excess heat and forces created when one or more of the battery cells overheat, vent or explode and the dampening layer reduces vibration and rattle of the battery cells within the enclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: 
           [0015]      FIG. 1  illustrates a perspective view of a typical battery pack of the prior art. 
           [0016]      FIG. 2  illustrates a perspective view of a battery pack with a protective layer surrounding battery cells. 
           [0017]      FIG. 3  illustrates a plan view of battery cells with the protective layer. 
           [0018]      FIG. 4  illustrates a cross-sectional view of a battery pack with the protective layer. 
           [0019]      FIG. 5  illustrates a cross-sectional view of a battery pack with the protective layer and a foam vibration dampening layer. 
           [0020]      FIG. 6  illustrates a cross-sectional view of another battery pack with the protective layer, a vibration dampening layer and electrical insulation layer. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures. 
         [0022]    Referring to  FIG. 1 , a perspective view of a typical battery pack  10  of the prior art will be described. Typical battery packs  10  have a plastic enclosure  20 , usually made of Acrylonitrile butadiene styrene otherwise known as ABS. Within the plastic enclosure  20  are one or more battery cells  22  connected in series, parallel or series/parallel by interconnecting conductive paths  18 , typically flat metal sheets that are tack-welded to battery terminals. One or more battery terminals  23  are connected to a power connection terminal  12  by wires  14 / 16  or other conductive paths for the delivery of power to a device and for the charging of the battery cells  22 . 
         [0023]    Although not shown, for completeness, often such battery packs  10  include other devices such as electronic circuits that prevent over current, over voltage, under voltage, control charging, prevent over-temperature situations during charging, etc. All such devices are known and present in some battery packs, but have been left out for clarity reasons. 
         [0024]    Although the size of the plastic enclosure  20  is shown exaggeratedly larger than needed, it is known that inside surfaces of such cases  20  often directly touch the battery cells  22  to support the battery cells  22 . It is also known that an air gap  24  separates the battery cells  22  from the inside surface of the plastic enclosure  20  in places where no contact is made. 
         [0025]    When such a battery pack  10  subjected to adverse conditions due to excess heat, internal failure, shorted contacts, etc., one or more individual cells  22  potentially will react. In some situations, the cells  22  will heat, potentially deforming the case  20 . In more severe situations, pressure will build up within the battery cells  22  and the battery cells  22  will heat, deform and, in some situations, out-gas. Out-gassing occurs when the electrolyte boils and changes state from a liquid to a gas, in which increases in pressure force open a safety valve, allowing the gas to escape. In still more severe situations, the pressure and heat build-up within the battery cells  22  causes the battery cells  22  to burst and/or explode. 
         [0026]    Being encapsulated in a plastic case  20  provides little resistance to any heat, pressure or explosion of the individual battery cells  22 . The typical ABS material quickly weakens under heat and pressure and provides little or no containment of any heat, excess gas pressure or explosion from one or more of the individual battery cells  22 . 
         [0027]    Referring to  FIG. 2 , a view of a battery pack  10  with a protective layer  30  surrounding the battery cells  22  will be described. The battery pack  50  has an enclosure  52 , made of any sturdy material such as ABS, preferably a heat resistant material such as Ultem from GE plastics. Within the enclosure  52  are one or more battery cells  22  connected in series, parallel or series/parallel by interconnecting conductive paths  18 , typically flat metal sheets that are tack-welded to battery terminals. Any known or future battery chemistry is anticipated including, but not limited to, alkaline, lead acid, nickel cadmium, nickel metal hydride, lithium, lithium ion, mercury, lithium iron, etc. 
         [0028]    One or more battery terminals  23  are connected to a power connection terminal  12  by wires  14 / 16  or other conductive paths for the delivery of power to a device and for the charging of the battery cells  22 . 
         [0029]    The battery cells  22  are enclosed in protective layer  30  made from a woven, thermally protective material. The protective layer  30  substantially or entirely surrounds the battery cells  22 , containing some or all excess heat or explosive force while permitting gases to escape. 
         [0030]    The protective material  30  is preferably a fabric substrate with a polymer coating. Various coatings are known such as Silicone, PTFE, Urethane, Neoprene, Fluroelastomers and many others. One example is Flouroelastomer Coated Glass Fabric that operates in temperature extremes of up to 500 degrees F. and has excellent chemical and water resistance. Such materials are known for use in welding and other uses, but not for use in battery packs  50 . 
         [0031]    Another exemplary material for use as the protective layer  30  is a high performance textile that is comprised of high purity, high strength amorphous silica fibers. Such Silica Textiles are designed for use where severe temperature conditions exist. The amorphous silica fibers are unaffected by most chemicals. Such materials are known for use in thermal insulation systems designed for severe temperatures, such as turbine covers, exhaust silencer covers, etc, but not for use in battery packs  50 . These materials are rated for temperatures as high as 1800 degrees F. 
         [0032]    In some embodiments, there is an air gap  24  between the protective layer  30  and the enclosure  52 , although in some embodiments, the air gap  24  is displaced by a dampening material  32  (see  FIG. 5 ). 
         [0033]    Although not shown, for completeness, often such battery packs  50  include other devices such as electronic circuits that prevent over current, over voltage, under voltage, control charging, prevent over-temperature situations during charging, etc. All such devices are known and present in some battery packs, but have been left out for clarity reasons. 
         [0034]    Referring to  FIG. 3 , a plan view of battery cells  22  with the protective layer  30  will be described. The one or more battery cells  22  connected in series, parallel or series/parallel by interconnecting conductive paths  18 , typically flat metal sheets that are tack-welded to battery terminals. Any known or future battery chemistry is anticipated including, but not limited to, alkaline, lead acid, nickel cadmium, nickel metal hydride, lithium, lithium ion, mercury, lithium iron, etc. 
         [0035]    Two or more of the batteries are connected to wires  14 / 16  or other conductive paths for the delivery of power to a device (external to the battery pack  52 ) and for the charging of the battery cells  22  (e.g. from an external charger). 
         [0036]    The battery cells  22  are enclosed in protective layer  30  made from a woven, thermally protective material. The protective layer  30  substantially or entirely surrounds the battery cells  22 , containing some or all excess heat or explosive force while permitting gases to escape. In some embodiments, the protective layer  30  is provided as a fabric pouch into which the battery cells  22  are inserted and the pouch is closed, allowing the wires  14 / 16  to extend beyond the protective layer  30  for connection to, for example, a connector  12  (see  FIG. 1 ). 
         [0037]    The protective material  30  is preferably a fabric substrate with a polymer coating. Various coatings are known such as Silicone, PTFE, Urethane, Neoprene, Fluroelastomers and many others. One example is Flouroelastomer Coated Glass Fabric that operates in temperature extremes of up to 500 degrees F. and has excellent chemical and water resistance. Such materials are known for use in welding and other uses, but not for use in battery packs  50 . 
         [0038]    Another exemplary material for use as the protective layer  30  is a high performance textile that is comprised of high purity, high strength amorphous silica fibers. Such Silica Textiles are designed for use where severe temperature conditions exist. The amorphous silica fibers are unaffected by most chemicals. Such materials are known for use in thermal insulation systems designed for severe temperatures, such as turbine covers, exhaust silencer covers, etc, but not for use in battery packs  50 . These materials are rated for temperatures as high as 1800 degrees F. 
         [0039]    Although not shown, for completeness, often such battery packs  50  include other devices such as electronic circuits that prevent over current, over voltage, under voltage, control charging, prevent over-temperature situations during charging, etc. All such devices are known and present in some battery packs, but have been left out for clarity reasons. 
         [0040]    When present, such other devices are preferably located within the protective layer  30 , although it is anticipated that these devices are alternately located between the enclosure  52  and the protective layer  30 . 
         [0041]    Referring to  FIG. 4 , a simplified cross-sectional view of a battery pack  50  with the protective layer  30  will be described. The one or more battery cells  22  connected in series, parallel or series/parallel by interconnecting conductive paths  18 , typically flat metal sheets that are tack-welded to battery terminals. Again, any known or future battery chemistry is anticipated including, but not limited to, alkaline, lead acid, nickel cadmium, nickel metal hydride, lithium, lithium ion, mercury, lithium iron, etc. The connecting wires  14 / 16  are not shown for clarity purposes. 
         [0042]    The battery cells  22  are enclosed in protective layer  30  made from a woven, thermally protective material. The protective layer  30  substantially or entirely surrounds the battery cells  22 , containing some or all excess heat or explosive force while permitting gases to escape. The battery cells  22  and protective layer  30  are encapsulated by a rigid enclosure  20  as known in the industry. 
         [0043]    The protective material  30  is preferably a fabric substrate with a polymer coating. Various coatings are known such as Silicone, PTFE, Urethane, Neoprene, Fluroelastomers and many others. One example is Flouroelastomer Coated Glass Fabric that operates in temperature extremes of up to 500 degrees F. and has excellent chemical and water resistance. Such materials are known for use in welding and other uses, but not for use in battery packs  50 . 
         [0044]    Another exemplary material for use as the protective layer  30  is a high performance textile that is comprised of high purity, high strength amorphous silica fibers. Such Silica Textiles are designed for use where severe temperature conditions exist. The amorphous silica fibers are unaffected by most chemicals. Such materials are known for use in thermal insulation systems designed for severe temperatures, such as turbine covers, exhaust silencer covers, etc, but not for use in battery packs  50 . These materials are rated for temperatures as high as 1800 degrees F. 
         [0045]    Although not shown, for completeness, often such battery packs  50  include other devices such as electronic circuits that prevent over current, over voltage, under voltage, control charging, prevent over-temperature situations during charging, etc. All such devices are known and present in some battery packs, but have been left out for clarity reasons. When present, such other devices are preferably located within the protective layer  30 , although it is anticipated that these devices are alternately located between the enclosure  52  and the protective layer  30 . 
         [0046]    In this embodiment, an air gap is present between the protective layer  30  and the enclosure  52 . In such embodiments, the size of the air gap is minimized to reduce vibration and rattle from the battery cells  22 . 
         [0047]    Referring to  FIG. 5 , a cross-sectional view of a battery pack  50  with the protective layer  30  and a vibration dampening layer  32  will be described. As previously described, the one or more battery cells  22  connected in series, parallel or series/parallel by interconnecting conductive paths  18 , typically flat metal sheets that are tack-welded to battery terminals. Again, any known or future battery chemistry is anticipated including, but not limited to, alkaline, lead acid, nickel cadmium, nickel metal hydride, lithium, lithium ion, mercury, lithium iron, etc. The connecting wires  14 / 16  are not shown for clarity purposes. 
         [0048]    The battery cells  22  are enclosed in protective layer  30  made from a woven, thermally protective material. The protective layer  30  substantially or entirely surrounds the battery cells  22 , containing some or all excess heat or explosive force while permitting gases to escape. The battery cells  22  and protective layer  30  are encapsulated by a rigid enclosure  20  as known in the industry. 
         [0049]    The protective material  30  is preferably a fabric substrate with a polymer coating. Various coatings are known such as Silicone, PTFE, Urethane, Neoprene, Fluroelastomers and many others. One example is Flouroelastomer Coated Glass Fabric that operates in temperature extremes of up to 500 degrees F. and has excellent chemical and water resistance. Such materials are known for use in welding and other uses, but not for use in battery packs  50 . 
         [0050]    Another exemplary material for use as the protective layer  30  is a high performance textile that is comprised of high purity, high strength amorphous silica fibers. Such Silica Textiles are designed for use where severe temperature conditions exist. The amorphous silica fibers are unaffected by most chemicals. Such materials are known for use in thermal insulation systems designed for severe temperatures, such as turbine covers, exhaust silencer covers, etc, but not for use in battery packs  50 . These materials are rated for temperatures as high as 1800 degrees F. 
         [0051]    Although not shown, for completeness, often such battery packs  50  include other devices such as electronic circuits that prevent over current, over voltage, under voltage, control charging, prevent over-temperature situations during charging, etc. All such devices are known and present in some battery packs, but have been left out for clarity reasons. When present, such other devices are preferably located within the protective layer  30 , although it is anticipated that these devices are alternately located between the enclosure  52  and the protective layer  30 . 
         [0052]    In this embodiment, a vibration dampening layer  32  is provided between the enclosure and the protective layer  30 . In such embodiments, the vibration dampening layer  32  reduces vibration and rattles from the battery cells  22 . The vibration dampening layer  32  is made from any suitable material such as polyurethane foam, etc. 
         [0053]    Referring to  FIG. 6 , a cross-sectional view of another battery pack  60  with the protective layer  30 , a vibration dampening layer  32  and electrical insulation layer  62 / 64 / 68  will be described. As previously described, the one or more battery cells  22  connected in series, parallel or series/parallel by interconnecting conductive paths  18 , typically flat metal sheets that are tack-welded to battery terminals. Again, any known or future battery chemistry is anticipated including, but not limited to, alkaline, lead acid, nickel cadmium, nickel metal hydride, lithium, lithium ion, mercury, lithium iron, etc. The connecting wires  14 / 16  are not shown for clarity purposes. 
         [0054]    In this embodiment, the an insulative layer  64  made of, for example, a fire resistant paper or cardboard covers most or all of the battery terminals and interconnecting conductive paths  18  and the battery cells  22  are enclosed in a shrink-wrap film  62  such as polyolefin and then the entire assembly  22 / 18 / 62 / 64  is enclosed in a protective layer  30  made from a woven, thermally protective material. The protective layer  30  substantially or entirely surrounds the battery cells  22 , containing some or all excess heat or explosive force while permitting gases to escape. The insulative layer  64  and/or the shrink-wrap film  62  electrically isolates the battery cells  22 . In this embodiment, the enclosure  66  is made from stronger materials that, in some embodiments, conduct electricity which has the potential to conduct electricity from the battery cells  22 , creating a potential for reduced battery life or overheating due to excessive current flowing. In this embodiment, although the enclosure  66  is anticipated to be made from any suitable, sturdy material (polyethylene, polypropylene, etc), the enclosure  66  is preferably made from a material that has improved strength, even though these materials often conduct electricity. One such material is a plastic with carbon fibers. These materials are known for improved structural strength. 
         [0055]    In some embodiments, the enclosure is lined with a coating of an electrically insulative material  68  such as fiberglass to improve strength and provide additional insulation between the 
         [0056]    As in the previous embodiments, the protective material  30  is preferably a fabric substrate with a polymer coating. Various coatings are known such as Silicone, PTFE, Urethane, Neoprene, Fluroelastomers and many others. One example is Flouroelastomer Coated Glass Fabric that operates in temperature extremes of up to 500 degrees F. and has excellent chemical and water resistance. Such materials are known for use in welding and other uses, but not for use in battery packs  50 . Another exemplary material for use as the protective layer  30  is a high performance textile that is comprised of high purity, high strength amorphous silica fibers. Such Silica Textiles are designed for use where severe temperature conditions exist. The amorphous silica fibers are unaffected by most chemicals. Such materials are known for use in thermal insulation systems designed for severe temperatures, such as turbine covers, exhaust silencer covers, etc, but not for use in battery packs  50 . These materials are rated for temperatures as high as 1800 degrees F. 
         [0057]    Although not shown, for completeness, often such battery packs  50  include other devices such as electronic circuits that prevent over current, over voltage, under voltage, control charging, prevent over-temperature situations during charging, etc. All such devices are known and present in some battery packs, but have been left out for clarity reasons. 
         [0058]    When present, such other devices are preferably located within the protective layer  30 , although it is anticipated that these devices are alternately located between the enclosure  52  and the protective layer  30 . 
         [0059]    In this embodiment, a vibration dampening layer  32  is provided between the enclosure and the protective layer  30 , although it is not required. In such embodiments, the vibration dampening layer  32  reduces vibration and rattles from the battery cells  22 . The vibration dampening layer  32  is made from any suitable material such as polyurethane foam, etc. 
         [0060]    Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result. 
         [0061]    It is believed that the system and method as described and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.