SAFETY SYSTEM FOR DETECTING A CRITICAL CONDITION IN A BATTERY PACK

Abstract

A safety system for detecting a critical condition in a battery pack. The safety system includes a control unit configured to obtain measurement data relating to a battery unit voltage and/or a battery unit temperature of at least some of the plurality of battery units, and to, based on the obtained measurement data, detect a critical condition of the battery pack, a stand-alone power supply configured to supply electric power to the safety system, a stand-alone communication interface configured to provide and/or communicate information relating to any critical condition of the battery pack detected by the control unit.

Claims

1. A safety system for detecting a critical condition in a battery pack comprising a plurality of battery units, the safety system comprising: a control unit configured to obtain measurement data relating to a battery unit voltage and/or a battery unit temperature of at least some of the plurality of battery units, and to, based on the obtained measurement data, detect a critical condition of the battery pack, a stand-alone power supply configured to supply electric power to the safety system, a stand-alone communication interface configured to provide and/or communicate information relating to any critical condition of the battery pack detected by the control unit.

2. The safety system according to claim 1, wherein the control unit is configured to obtain measurement data relating to the battery unit voltage of each one of the plurality of battery units.

3. The safety system according to claim 1, wherein the control unit is configured to obtain measurement data relating to the battery unit temperature of each one of the plurality of battery units.

4. The safety system according to claim 1, wherein the stand-alone communication interface is configured to, in response to the detection of a critical condition by the control unit, communicate and/or provide information relating to the critical condition from the safety system to a remotely located user.

5. The safety system according to claim 1, wherein the control unit is configured to detect a critical condition of the battery pack by determining whether a predetermined criterion is fulfilled for any one of the battery units in the battery pack.

6. The safety system according to claim 5, wherein said predetermined criterion is fulfilled if said battery unit voltage of any one of said battery units is of a magnitude below a predefinable voltage threshold magnitude and/or if said battery unit temperature of any one of said battery units is above a predefinable temperature threshold value.

7. The safety system according to claim 1, wherein the stand-alone communication interface is at least one of a visual communication means, an audible communication means, a controller area network interface and a personal area network interface.

8. The safety system according to claim 1, wherein the stand-alone power supply comprises a rechargeable battery.

9. The safety system according to claim 8, wherein the safety system further comprises at least one photo-voltaic module configured for charging of said at least one rechargeable battery.

10. A battery pack comprising: a plurality of battery units means for measuring the battery unit voltage, and/or the battery unit temperature of at least some of the plurality of battery units, the safety system according to claim 1.

11. The battery pack according to claim 10, wherein the battery pack comprises means for measuring the battery unit voltage of each one of the plurality of battery units.

12. The battery pack according to claim 10, wherein the battery pack comprises means for measuring the battery unit temperature of each one of the plurality of battery units.

13. The battery pack according to claim 10, wherein the stand-alone communication interface comprises at least a visual communication means visibly attached to an external surface of the battery pack.

14. An electric energy storage system of a vehicle comprising at least one battery pack according to claim 10.

15. A vehicle comprising an electric energy storage system according to claim 14.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

[0045] In the drawings:

[0046] FIG. 1 is a schematic drawing illustrating a vehicle,

[0047] FIG. 2 is a block diagram illustrating an electric energy storage system,

[0048] FIG. 3 is a block diagram illustrating a battery pack comprising a safety system according to an embodiment of the invention, and

[0049] FIG. 4 is a schematic drawing illustrating a battery pack and a safety system according to an embodiment of the invention.

[0050] The drawings are schematic and not necessarily drawn to scale.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0051] In the present detailed description, embodiments of the system according to the present invention are mainly described with reference to an all-electric bus, comprising a propulsion system in the form of battery powered electric motors. However, it should be noted that various embodiments of the described invention are equally applicable for a wide range of hybrid and electric vehicles and vessels, and also for stationary applications and/or during storage of the battery pack in a warehouse or similar.

[0052] FIG. 1 shows a simplified perspective view of an all-electric vehicle in the form of a bus 100, which is equipped with an electric energy storage system (ESS) 200. The energy from the electric energy storage system 200 is primarily used for propulsion of the bus 100 by means of at least one electric machine (not shown). Of course, the energy from the electric energy storage system 200 may also be used by other loads in addition to or instead of the electric machine used for propulsion of the bus 100, for example auxiliary systems requiring electric power, and/or an on-board charger, and/or a power take-off.

[0053] As may be gleaned from FIG. 2, the electric energy storage system 200 comprises a plurality of battery packs 300, 300′, 300″ that may be connected in series or in parallel. Each battery pack 300, 300′, 300″ comprises a plurality of interconnected battery units 310, 310′, 310″. It should be noted that the setup in FIG. 2, showing an electric energy storage system 200 comprising three battery packs 300, 300′, 300″, each battery pack 300, 300′, 300″ comprising three battery units 310, 310′, 310″, is purely intended for illustrational purposes and should in no way be construed as limiting for the invention. Although not illustrated in FIG. 2, each battery unit 310, 310′, 310″ may be an individual battery cell or a battery module comprising a plurality of battery cells, such as a battery string comprising at least two battery cells connected in series so as to provide an output DC voltage having a desired voltage level. Purely by way of example, each battery pack 300, 300′, 300″ may comprise a plurality of such battery modules connected in parallel.

[0054] Suitably, the battery cells are of lithium-ion type, but other types may also be used. The number of battery cells per battery pack 300, 300′, 300″ may be in the range of 50 to 500 cells, or up to many thousands of cells in the case of small format cells.

[0055] Each battery pack 300, 300′, 300″ may comprise a battery management unit (BMU) 340 configured for managing the battery pack. The BMU 340 receives and processes measurement data relating to current, voltage and temperature of the battery units 310, 310′, 310″ within associated battery pack 300 and may also estimate battery states of the battery pack 300, such as state-of-charge (SoC), state-of-health (SoH), state of power (SoP) and state of energy (SoE). An ESS control unit 210 may also be provided, which is configured for controlling the ESS 200 during operation of the bus 100. The ESS control unit 210 can also be configured for determining parameters indicating and controlling the condition or capacity of the ESS 200 and/or of battery packs 300, 300′, 300″ thereof, such as the battery states mentioned above, based on data received from the BMU of each battery pack, herein illustrated by the BMU 340 of the battery pack 300.

[0056] In FIG. 3, a battery pack 300 from the plurality of battery packs 300, 300′, 300″ is shown in greater detail. As already discussed, the battery pack 300 comprises a plurality of battery units 310, 310′, 310″. The battery pack 300 furthermore comprises a safety system 400 according to an embodiment of the invention, which safety system 400 is adapted to detect a critical condition in the battery pack 300 based on measurement data relating to battery unit temperature and/or voltage. The safety system 400 comprises a control unit 410, a stand-alone power supply 420 and a stand-alone communication interface 430.

[0057] In the embodiment illustrated in FIG. 3, the battery pack 300 comprises means 320, 320′, 320″; 330, 330′, 330″ for measuring the battery unit voltage and the battery unit temperature of each one of the plurality of battery units 310, 310′, 310″, i.e. voltage sensors 320, 320′, 320″ and temperature sensors 330, 330′, 330″, respectively. These sensors 320, 320′, 320″; 330, 330′, 330″ may advantageously be the same sensors that are used to collect measurement data used by the BMU 340 (not illustrated in FIG. 3). Alternatively, some or all of the sensors 320, 320′, 320″; 330, 330′, 330″ may be dedicated for use with the safety system 400. However, it may also be sufficient to have means for measuring the battery unit voltage and/or means for measuring the battery unit temperature of only some of the battery units 310, 310′, 310″.

[0058] The control unit 410 is configured to obtain measurement data relating to a battery unit voltage and/or a battery unit temperature of at least some of the plurality of battery units 310, 310′, 310″ from the sensors 320, 320′, 320″; 330, 330′, 330″, such as via a wired or a wireless connection. Based on the obtained measurement data, the control unit 410 is configured to detect a critical condition in the battery pack 300. The critical condition may e.g. be a short-circuit or a thermal runaway within the battery pack 300.

[0059] Purely by way of example, the control unit 410 may be configured to detect a critical condition of the battery pack 300 by determining whether a predetermined criterion is fulfilled for any one of the battery units 310, 310′, 310″ in the battery pack 300. The predetermined criterion may for example be considered to be fulfilled if the battery unit voltage of any one of the battery units 310, 310′, 310″ is of a magnitude below a predefinable voltage threshold magnitude. The predefined voltage threshold magnitude may be set to a value which is indicative of a risk for thermal runaway within the battery pack 300. The predetermined criterion may alternatively, or additionally, be set so that it is considered to be fulfilled if the battery unit temperature of any of the battery units 310, 310′, 310″ is above a predefinable temperature threshold value. This may also indicate a thermal runaway within the battery pack 300. The criterion may be set so that a critical condition is determined to be detected if at least one of the voltage related criterion and the temperature related criterion is considered fulfilled. The actual voltage threshold magnitude and temperature threshold value should be defined depending on battery cell type, such as by the battery cell manufacturer, since in particular the voltage may vary depending on cell chemistry.

[0060] The stand-alone power supply 420 may be a rechargeable battery which may be charged by means of at least one photo-voltaic module 440. However, other methods for charging, such as by using energy from the battery pack 300 or an external power source (not shown), are not excluded. The stand-alone power supply 420 supplies power to the safety system 400 and its components and preferably also to the means 320, 320′, 320″; 330, 330′, 330″ for measuring the battery unit voltage and/or the battery unit temperature, but not to any other consumers.

[0061] If the system comprises one or more photo-voltaic modules 440, these are preferably located on the outside of the battery pack 300, in a position where they are likely to be exposed to light. Optionally, the photo-voltaic modules 440 are configured to be movable, so that their positions can be altered depending on the current use of the battery pack 300 or other conditions, e.g., the light conditions in a warehouse. It is conceivable that the photo-voltaic modules 440 may be located in another position than on the outside of the battery pack 300, as long as the position is suitable for that purpose.

[0062] The stand-alone communication interface 430 may be configured to passively provide and/or to actively communicate information relating to any critical condition of the battery pack 300 detected by the control unit 410. Thus, information and data stored in the control unit 410 may be accessed by a user via the stand-alone communication interface 430. The stand-alone communication interface 430 is used only by the safety system 400, and thus it communicates and/or provides only information related to the safety system 400, and in particular information related to any critical condition detected by the control unit 410. The communication interface 430 may also be used to communicate any problem or malfunction of the safety system 400 itself, such as a low battery level of the stand-alone power supply 420 or malfunctioning sensors 320, 320′, 320″; 330, 330′, 330″.

[0063] The stand-alone communication interface 430 is configured to communicate and/or provide information to a remotely located user 500. For example, the stand-alone communication interface 430 may comprise a visual communication means, such as a warning lamp, which may be used to actively communicate that a critical condition has been detected to anyone within seeing distance. A visual signal communicated by the visual communication means may be adapted to help the remotely located user 500 to understand if any critical condition has been detected in the battery pack 300, or if there is any problem or malfunction of the safety system 400. The visual signal may further be adapted to reflect a degree of severity of the detected condition in the battery pack 300. Purely by way of example, the visual communication means may display a red, flashing signal when any critical condition has been detected in the battery pack 300, a yellow, steady signal when an energy level in the stand-alone power supply 420 is below a first threshold charge level, and a yellow, flashing signal when the energy level in the stand-alone power supply 420 is below a second threshold charge level. The stand-alone communication interface 430 may alternatively or additionally comprise an audible communication means, such as a loudspeaker, which may be used to actively communicate that a critical condition has been detected to anyone within hearing distance. An audible signal communicated by the audible communication means may, e.g., be in the form of a tone, a series of tones, or a spoken message. Preferably, the audible signal may be adapted in a manner analogous to that described above in connection with the visual signal to help the remotely located user 500 understand if any critical condition has been detected in the battery pack 300, or if there is a problem or malfunction of the safety system 400, and also the severity of the detected condition. The stand-alone communication interface 430 may additionally, or alternatively, comprise a remotely accessible controller area network interface or personal area network interface, which may be configured to actively communicate information by e.g. sending a message/signal that a critical condition has been detected, or that a problem or malfunction of the safety system 400 has been identified, such as a text message to a mobile phone and/or a message to a remotely located surveillance system. It may further be configured to provide information stored in the control unit 410 when accessed by a user. The stand-alone communication interface 430 may also send data to a remote server for storage. Thus, the remotely located user 500 may be a person that is located within seeing or hearing distance from the battery pack 300, or it may be a person that is located farther away.

[0064] The safety system 400 may also be connected to the BMU 340 and/or to the ESS control unit 210 so that it may be readily identified by the BMU or ESS control unit if, for some reason, the safety system 400 is not functional. Thus, the BMU 340 and/or the ESS control unit 210 may trigger a warning signal if it is detected that the safety system 400 is not functional.

[0065] As schematically illustrated in FIG. 4, the components of the safety system 400, such as the control unit 410, the power supply 420 and the communication interface 430 shown in FIG. 3, may be mounted together in a common housing 450 or similar on an external surface of the battery pack 300, such as on a battery pack housing 350. In the embodiment shown in FIG. 4, the communication interface comprises on one hand visual communication means in the form of a display 460 and a warning lamp 470, and on the other hand a remotely accessible controller area network interface (not illustrated in FIG. 4).

[0066] However, the components 410, 420, 430 may also be mounted separately with, for example, any visible communication means of the communication interface 430 visibly mounted on an external surface of the battery pack 300. The components 410, 420, 430, or preferably the common housing, may be adapted to be moveable. In particular, the common housing and/or the communication interface 430 may be adapted to be mounted in different positions on the external surface of the battery pack 300. Thus, the components 410, 420, 430 or the common housing can be positioned differently on the same battery pack in different applications or different situations as deemed suitable. Purely by way of example, when the battery pack 300 is stored in a warehouse, the components 410, 420, 430 may be positioned on an end of the battery pack 300 and when the battery pack 300 is used in a vehicle 100, the components 410, 420, 430 may be positioned on a top surface of the battery pack 300. Advantageously and regardless of if the components 410, 420, 430 or the common housing are adapted to be moveable or not, if the battery pack 300 is used in a vehicle 100, the components 410, 420, 430 or the common housing should be mounted in a position where the components 410, 420, 430 are least likely to be damaged if the vehicle 100 is involved in an accident.

[0067] In the embodiment illustrated above, the safety system 400 is applied in a battery pack 300, 300′, 300″ of a vehicle 100. However, the safety system 400 may advantageously be used also with battery packs outside a vehicle application, such as in a stationary energy storage system, or in a vessel, or during storage of the battery pack in e.g. a warehouse, or during transport of the battery pack.

[0068] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.