Method and apparatus for short circuit prevention in a battery storage system

Abstract

Apparatus for short circuit prevention in a battery storage system comprising a thermally activated disconnect device or material positioned in a conductive path between a sensing printed circuit board trace and a battery storage cell terminal, where the thermally activated disconnect device or material opens the conductive path when an ambient temperature rises above a threshold level. A method of operation of the apparatus is also disclosed.

Description

METHOD AND APPARATUS FOR SHORT CIRCUIT PREVENTION IN A BATTERY STORAGE SYSTEMBACKGROUNDField

[0001] Embodiments of the present invention generally relate to battery storage systems and, in particular, to a method and apparatus for preventing short circuits in battery storage systems.Description of the Related Art

[0002] A battery storage system typically comprises a battery for storing electrical energy coupled to a battery management unit (BMU) for controlling charging and discharging of the battery. The battery comprises a plurality of storage cells arranged in an array. To operate properly, the BMU relies on information supplied from a storage cell sensing printed circuit board (PCB). The sensing PCB is coupled to the storage cells to monitor the state of charge (SOC) of the storage cells.

[0003] To create a compact battery storage system and to improve the accuracy of sensing information, the sensing PCB is typically mounted close to the battery. In fact, in many systems, the sense PCB is mounted in close proximity to the battery (e.g., directly on top of the battery). The sense PCB comprises circuit traces that connect sensing circuitry (i.e. , integrated circuits) to the storage cell terminals.

[0004] Upon thermal runaway, a storage cell may outgas flammable gasses at a temperature of about 500 degrees Celsius. A PCB made of FR4 material has a melting point of only 120 degrees Celsius. Consequently, a battery mounted PCB is subject to melting when a storage cell experiences thermal runaway. When the PCB melts, the traces on the PCB may short circuit causing additional storage cells to enter thermal runaway. Additionally, such short circuits may emit sparks that may ignite the flammable gasses that are emitted from a storage cell during thermal runaway.

[0005] Therefore, there is a need for a method and apparatus for short circuit prevention in a battery storage system.SUMMARY

[0006] A method and apparatus for short circuit prevention in a battery storage system is provided substantially as shown in and / or described in connection with at least one of the figures, as set forth more completely in the claims.

[0007] Various features and advantages of the present disclosure may be appreciated from a review of the following detailed description of the present disclosure, along with the accompanying figures in which like reference numerals refer to like parts throughout.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] So that the manner in which the above recited features of the present invention can be understood in detail, a particular description of the invention, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0009] FIG. 1 depicts a perspective view of a battery storage system having thermal fuses in the sense traces of the sensing PCB in accordance with at least one embodiment of the invention; and

[0010] FIG. 2 depicts a perspective view of a battery storage system having thermal disconnects between the sense traces of the sensing PCB and the battery cell terminal connections in accordance with at least one embodiment of the invention.DETAILED DESCRIPTION

[0011] Embodiments of the present invention comprise apparatus and methods for short circuit prevention in a battery storage system. Embodiments of the invention comprise a battery storage system having a plurality of storage cells coupled to abattery management unit (BMU). A portion of the BMU is a sensing printed circuit board (PCB) for monitoring the state of charge (SoC) of the plurality of storage cells. The sensing PCB is mounted in close proximity to the storage cells (e.g., mounted on top of the battery). The sensing PCB comprises various integrated circuits that are coupled to the storage cell terminals via conductive circuit traces (i.e., conductive paths). Embodiments of the invention comprise thermally activated disconnect devices or materials that disconnect the sensing PCB circuit traces from the storage cell terminals when the ambient temperature proximate the sensing PCB exceeds a threshold level that indicates a storage cell has begun thermal runaway. Such thermally activated disconnect devices or materials include, but are not limited to, thermal fuses, thermal epoxy, and the like.

[0012] FIG. 1 depicts a perspective view of a battery storage system 100 having thermal fuses 102 in the sense traces 104 of the sensing PCB 106 in accordance with at least one embodiment of the invention. The battery storage system 100 comprises a battery 1 18 and a sensing PCB 106. The battery 118 comprises a plurality of individual storage cells 114. Each storage cell 114 has a pair of terminals 116 (only a top terminal is shown) and a conductive strip 112 interconnects adjacent pairs of storage cell terminals 116.

[0013] The sensing PCB 106 comprises integrated circuits 108 and other circuit elements that are interconnected via conductive traces 104. The traces 104 generally terminate at the edges of the sensing PCB 106 and are coupled to the storage cell terminals via a conductive strip 110. Through this connection to the storage cell terminals, the circuitry of the sensing PCB 106 monitors the state of charge of each of the cells 114. In accordance with an embodiment of the invention, each trace 104 that is connected to the cell terminals 116 comprise a device or material that is thermally activated to disconnect the trace 104 from the battery cell 114 (e.g., open the conductive path) when the ambient temperature is high enough to indicate that a storage cell 114 is in a state of runaway. In one exemplary embodiment, the thermally activated disconnect device is a thermal fuse 102 that is placed in the conductive path of trace 104 or at the terminal end of the trace 104 between the trace 104 and a' " strip 1 10 connecting the fuse 102 to the battery terminal 116. The fuse 102is normally conductive until the ambient temperature causes the fuse 102 to open and disconnect the trace 104 from the storage cell 1 14. A fuse 102 is included in each sense trace 104 such that when a storage cell 114 runs away and heats the ambient environment, the fuses 102 disconnect the sensing PCB 106 from the battery 118. Consequently, if the ambient temperature rises to a point where the PCB 106 melts, the traces 104 are no longer connected to the battery 118 and cannot cause a short circuit across any of the storage cells 114. Also, with the traces disconnected, a short circuit will not produce sparks to ignite the flammable gasses from the runaway cell.

[0014] FIG. 2 depicts a perspective view of a battery storage system 200 having thermal disconnects 202 between the sense traces 104 of the sensing PCB 106 and the battery cell terminal connections 1 16 in accordance with at least one alternative embodiment of the invention. The battery storage system 200 is similar to the battery storage system 100 in FIG. 1 except, rather than thermal fuses as thermal disconnects, the embodiment in FIG. 2 uses a material (e.g., thermally activated epoxy) 202 to couple the terminal end of the sensing traces 104 to the conductive strip 110. The epoxy 202 is a thermally activated material that has a low melting point (e.g., lower than the melting point of the sensing PCB 106). When the ambient temperature rises above the melting point of the epoxy, the epoxy 202 melts and disconnects (opens) the conductive path to the storage cell terminal 116. As such, when thermal runaway occurs, the sensing PCB 106 becomes disconnected from the battery 118 before the PCB 106 reaches its melting point ensuring that the traces 104 do not short circuit any of the storage cells or cause sparks that may ignite flammable gasses.

[0015] An exemplary adhesive material is an electrically conductive epoxy such as, for example, but not limited to, a silver-filled epoxy. One such epoxy is epoxy model 8331 , manufactured by MG Chemicals of Ontario, Canada.

[0016] Here multiple examples have been given to illustrate various features and are not intended to be so limiting. Any one or more of the features may not be limited to the particular examples presented herein, regardless of any order, combination, or connections described. In fact, it should be understood that any combination of the features and / or elements described by way of example above are contemplated,including any variation or modification which is not enumerated, but capable of achieving the same. Unless otherwise stated, any one or more of the features may be combined in any order.

[0017] As above, figures are presented herein for illustrative purposes and are not meant to impose any structural limitations, unless otherwise specified. Various modifications to any of the structures shown in the figures are contemplated to be within the scope of the invention presented herein. The invention is not intended to be limited to any scope of claim language.

[0018] Where “coupling” or “connection” is used, unless otherwise specified, no limitation is implied that the coupling or connection be restricted to a physical coupling or connection and, instead, should be read to include communicative couplings, including wireless transmissions and protocols.

[0019] Where conditional language is used, including, but not limited to, “can,” “could,” “may” or “might,” it should be understood that the associated features or elements are not required. As such, where conditional language is used, the elements and / or features should be understood as being optionally present in at least some examples, and not necessarily conditioned upon anything, unless otherwise specified.

[0020] Where lists are enumerated in the alternative or conjunctive (e.g., one or more of A, B, and / or C), unless stated otherwise, it is understood to include one or more of each element, including any one or more combinations of any number of the enumerated elements (e.g., A, AB, AC, ABC, ABB, etc.). When “and / or” is used, it should be understood that the elements may be joined in the alternative or conjunctive.

[0021] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

Claims:1 . Apparatus for short circuit prevention in a battery storage system comprising: a thermally activated disconnect device or material positioned in a conductive path between a sensing printed circuit board trace and a battery storage cell terminal, where the thermally activated disconnect device or material opens the conductive path when an ambient temperature rises above a threshold level.

2. The apparatus of claim 1 where the thermally activated disconnect device or material is a thermally activated fuse that opens at the threshold level.

3. The apparatus of claim 1 where the thermally activated disconnect device or material is a thermally activated epoxy that melts at the threshold level.

4. The apparatus of claim 1 further comprising a sensing printed circuit board, supporting the sensing printed circuit board trace, for sensing a voltage of at least one battery storage cell.

5. The apparatus of claim 4 wherein the threshold level is less than the melting point of the sensing printed circuit board.

6. The apparatus of claim 1 wherein the threshold level is about 120 degrees Celsius.

7. Apparatus for short circuit prevention in a battery storage system comprising: a thermally activated disconnect device or material positioned in a conductive path between a sensing printed circuit board trace and a battery storage cell terminal, where the thermally activated disconnect device or material opens the conductive path before an ambient temperature within the battery storage system reaches a melting point of the sensing printed circuit board.

8. The apparatus of claim 7 where the thermally activated disconnect device or material is a thermally activated fuse that opens at the threshold level.

9. The apparatus of claim 7 where the thermally activated disconnect device or material is a thermally activated epoxy that melts at the threshold level.

10. A method of preventing a short circuit in a battery storage system, where the battery storage system comprises a plurality of storage cells conductively coupled to a sensing printed circuit board via at least one conductive path comprising: upon an ambient temperature rising above a threshold level, opening the at least one conductive path to disconnect the sensing printed circuit board from the plurality of storage cells.11 . The method of claim 10 where the at least one conductive path is opened by a thermally activated fuse that opens at the threshold level.

12. The method of claim 10 where the at least one conductive path is opened by a thermally activated epoxy that melts at the threshold level.

13. The method of claim 10 where the sensing printed circuit board, supporting the sensing printed circuit board trace, senses a voltage of at least one battery storage cell.

14. The method of claim 10 wherein the threshold level is less than the melting point of the sensing printed circuit board.

15. The method of claim 10 wherein the threshold level is about 120 degrees Celsius.

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