Systems for improving safety and reliability of lithium-ion (Li-ion) battery packs

Abstract

A battery pack (12) includes: one or more battery cells (18); a battery management system (20) including at least one electronic processor (24) configured to monitor a parameter of the battery pack; at least one fault detection sensor including at least one of at least one gas sensor (36) configured to measure gas escaping from the plurality of battery cells and an impact sensor (30) configured to measure an impact to the battery pack; and a housing (16) surrounding the plurality of battery cells, the battery management system, and the at least one fault detection sensor. The battery management system is configured to perform a remedial action in response to the at least one fault detection sensor detecting a fault.

Description

Technical Field

[0001] The following relates generally to battery cell technology, and more particularly to battery cell monitoring technology, battery cell safety technology, battery cell remediation technology, and related technologies. Background Art

[0002] Many Class II and Class III medical devices (e.g., patient monitors, mechanical ventilators, and cardiac defibrillators) rely on battery power when in operation and not connected to an AC power source. The battery packs in these devices are typically made from rechargeable lithium-ion (Li-ion) photovoltaic cells and are monitored by an onboard battery management system (BMS) that continuously communicates with the host device about the battery status during operation.

[0003] While Li-ion batteries excel in terms of capacity, high energy density, and long life cycles, they are susceptible to damage from electrical, thermal, and / or mechanical abuse. Deviations from the recommended charge / discharge guidelines or improper battery handling can lead to cell damage and ultimately to a phenomenon known as "thermal runaway" (TRA). In general, TRA is a combination of chemical and electrical events within a cell in response to electrical, mechanical, or thermal abuse, and can cause the cell to increase in temperature, overheat, and ultimately end in the release of toxic gases, fire, or explosion.

[0004] Such medical devices are often deployed outside of clinics and hospitals, for example in ambulances, helicopters or other medical transports, and are particularly susceptible to vibration and mechanical shock during operation in such environments. In addition, batteries may encounter temperature and mechanical extremes during transportation.

[0005] The battery pack may also be connected to a non-original equipment manufacturer (OEM) external charger (eg, outside the host medical device) when not in use, which may not operate in full compliance with the battery manufacturer's charging guidelines.

[0006] Commercial Li-ion batteries sometimes include safety features such as internal pressure, temperature and current (PTC) switches, tear-off labels, shut-off separators, insulators, connectors and vents on battery packs, and manufacturers publish guidelines on charge / discharge conditions that must be followed by medical instrument designers and users of battery packs. BMS controllers add another layer of safety by managing the charge / discharge of cells, monitoring key electrical operating parameters of cells, and shutting down the battery if electrical operating conditions are violated.

[0007] New and improved systems and methods are disclosed below. Summary of the invention

[0008] In one disclosed aspect, a battery pack includes: one or more battery cells; a battery management system including at least one electronic processor configured to monitor parameters of the battery pack; at least one fault detection sensor including at least an impact sensor and an accelerometer, the impact sensor configured to measure an impact on the battery pack; the accelerometer operatively connected to the impact sensor, the impact sensor configured to activate the accelerometer to measure the magnitude of the impact on the multiple battery packs; and a housing enclosing the multiple battery cells, the battery management system, and the at least one fault detection sensor. The battery management system is configured to perform remedial action in response to the at least one fault detection sensor detecting a fault, wherein the remedial action performed by the battery management system in response to the impact sensor detecting an impact includes at least two of the following: shutting down the multiple battery cells when the impact on the one or more battery cells exceeds a predetermined impact threshold; storing the occurrence of the impact in a memory when the impact on the multiple battery cells is below the predetermined impact threshold; generating a visual or audio message indicating that the multiple battery cells need to be replaced; and generating a visual or audio message indicating that the medical device powered by the battery pack should be replaced with a new medical device.

[0009] In another disclosed aspect, an apparatus comprises: a medical device; and the above-mentioned battery pack, which is connected to the medical device to power the medical device; wherein the medical device is configured to read the data stored in the memory when the battery pack is connected to the medical device.

[0010] One advantage resides in providing a battery management system for detecting gas generated by battery cells.

[0011] Another advantage resides in providing a battery management system for detecting an impact to a battery pack.

[0012] Another advantage resides in providing a battery management system for generating remedial actions when gas and / or an impact to a battery pack is detected.

[0013] A given embodiment may provide none, one, two, more, or all of the aforementioned advantages, and / or may provide other advantages as will become apparent to one of ordinary skill in the art upon reading and understanding the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present disclosure may take form in various components and arrangements of components, and in various steps and arrangements of steps.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the present disclosure.

[0015] Figure 1 schematically illustrates a battery pack according to one aspect; and

[0016] Figure 2 Shows Figure 1 An exemplary flow chart of the operation of a battery pack. DETAILED DESCRIPTION

[0017] Existing Li-ion cells used in battery packs for powering medical devices have safety features, including internal pressure, temperature and current (PTC) switches, tear-off labels, shut-off separators, vents, etc. However, despite these measures, fire and explosion incidents associated with medical devices powered by Li-ion batteries still occur from time to time. In some cases, the failure sequence leading to such events can be so fast that existing safety devices cannot react quickly enough to prevent catastrophic failure.

[0018] The following discloses adding an impact sensor and / or a gas sensor to detect the root cause of a failure (e.g., an impact shock or an incipient gas release, respectively) before a catastrophic event occurs in conjunction with an onboard battery management system (BMS) programmed to take remedial action. In the event of an emergency (e.g., a detected gas leak is likely to quickly lead to a fire or explosion), the BMS will respond directly, for example: by operating a fuse to disable the battery pack and prevent failure. The sensor data can also be stored in an onboard memory and read when the battery is next connected to a medical device capable of reading and processing the stored sensor data. In the event of a low-energy impact event being detected (in which case the likelihood of imminent catastrophic damage is low), this can be an appropriate remedial measure. If the battery is currently installed in such a medical device, the sensor data transmission and processing can be performed immediately. In another (not necessarily mutually exclusive) variant, the Li-ion battery pack includes a wireless transceiver (e.g., Bluetooth and / or Wi-Fi), and the Li-ion battery transmits the sensor data to a battery management center at a hospital via the wireless transceiver together with the battery pack serial number or other unique identifier.

[0019] In some embodiments, the shock sensor is completely passive and therefore does not draw power from the battery unless an impact event is detected. Some contemplated shock sensors include an open circuit element with a spring contact that vibrates to form electrical contact when subjected to sufficient impact. In one embodiment, several such passive shock sensors are provided with different spring stiffness levels, and the magnitude of the impact is determined by which one or more of the shock sensors are triggered. In another embodiment, a single spring-based shock sensor is operatively connected to a "wake-up" pin of an active accelerometer such that the shock sensor operates to wake up the accelerometer, which quickly measures the magnitude of the impact. Likewise, because the active accelerometer is in a sleep state or other low-power state unless / until activated by the spring-based shock sensor, electrical power consumption is minimized.

[0020] Gas sensors are designed to measure gases that typically escape from damaged Li-ion battery cells. Suitable detection gases include hydrogen, benzene, methane, or some other flammable gas. To save power and enhance sensitivity, the placement of (one or more) gas sensors is selected to provide effective gas detection. Each Li-ion battery cell typically has a vent near the positive terminal, so a gas sensor can be placed to sniff the vent of each battery cell, thereby fully detecting gas leaks from any of these cells. To reduce the number of gas sensors, a single gas sensor can be placed at the vent of the battery pack housing.

[0021] Depending on the nature and magnitude of the sensor data and the type of medical device, the remedial action can take a variety of forms. For a Class II medical device that is capable of safe shutdown, if the detected shock and / or gas leak magnitude is above a threshold, the battery pack's onboard battery management system can shut down the battery. On the other hand, if the shock value is lower, the shock value can simply be recorded and a recommendation can be displayed on the medical device display indicating that the battery should be replaced. If a sufficient number of small shocks are detected, the battery may be shut down, or alternatively a recommendation may be displayed indicating that the battery should be replaced. In the event of a gas leak detected in a battery powering a Class II medical device, shutting down the battery may be an appropriate remedial action.

[0022] For Class III medical devices that perform life-critical functions, abrupt battery shutdown may not be an option because the device must continue to operate. In this case, a critical alarm (visual alarm and possibly audible alarm) will be appropriately presented to notify medical personnel of impending battery failure so that immediate action can be taken (such as replacing the medical device).

[0023] Typically, a battery pack includes multiple battery cells, for example, multiple battery cells electrically interconnected in series to provide a higher voltage, or multiple battery cells electrically interconnected in parallel to provide a higher current / capacitance. However, battery packs with as few as a single battery cell are also contemplated. While Li-ion battery packs employing Li-ion battery cells are the current standard in the medical field, it is contemplated that the disclosed concepts will be used with other types of batteries, for example, lithium polymer (LiPo) battery cells or nickel-metal hydride (NiMH) battery cells. The gas sensor(s) should be selected to detect gases escaping during a failure of the particular type(s) of battery cells in use.

[0024] refer to Figure 1 , the apparatus 10 shows a battery pack 12 connected to a medical device 14 to power the medical device, for example, by being inserted into a battery receptacle 15 of the medical device 14. The battery pack 12 includes a housing 16 that surrounds the various components of the battery pack. A plurality of battery cells 18 are connected to a battery management system 20. The battery management system 20 includes at least one electronic processor 24 that is configured to monitor parameters of the battery cells 18. The at least one electronic processor (e.g., Figure 1 A microprocessor or microcontroller and supporting circuitry (not shown) implement a set of programmable voltage, current, capacitance, and temperature registers whose values ​​are programmed according to the recommendations of the cell manufacturer to ensure safe and reliable charging / discharging cycles of the battery pack. In use, the battery pack 12 is inserted into the battery receptacle 15 of the medical device 14. In a typical arrangement, the housing 16 of the battery pack 12 is shaped and sized to fit snugly into the battery receptacle 15, wherein the contacts 23 of the battery pack 12 contact the mating contacts 23' of the battery receptacle 15 to conduct power (e.g., voltage at a designed current) from the battery pack 12 (and more specifically from the battery cells 18) to power the medical device 14. Typically, the paired contacts 23, 23' are used to transfer power from the battery pack 12 to the medical device 14, and optionally also include paired contacts for transferring data (e.g., using the industry standard System Management Bus (SMBus) protocol). Although in Figure 1 14, but it is understood that the battery cells 18 are electrically interconnected in electrical series, in electrical parallel, or in some parallel-series interconnection configuration to deliver power. (In limited cases, there may be a single battery cell 18, in which case such interconnection of multiple cells is not employed). The battery receptacle 15 may optionally be designed with a hinged cover, a sliding cover, or the like to limit accidental contact with an installed battery pack; alternatively, a portion of the housing 16 of the battery pack 12 may be flush with the housing of the medical device 14, or a portion of the housing 16 of the battery pack 12 may extend beyond the battery compartment 15.

[0025] At least one electronic processor 24 is configured to communicate with a microprocessor 26 of the medical device 14 through a pair of data contacts of a set of contacts 23, 23', which transmit information between the two processors 24, 26 via the SMBus protocol when the battery pack 12 is installed in the battery compartment 15. If a serious deviation from the parameters stored in the registers of the electronic processor 24 is detected and the battery pack 12 is not connected to the medical device 14, the electronic processor 24 sends a signal to the fuse 28 to disable the battery pack 12 and prevent malfunction.

[0026] The battery pack 12 also includes at least one fault detection sensor. In one embodiment, the at least one fault detection sensor includes an impact sensor 30 that is configured to measure or detect a fault including an impact to the battery pack 12. The impact sensor 30 can be any suitable sensor (e.g., an SQ-ASx sensor available from SignalQuest of Lebanon, New Hampshire). The impact sensor can be designed to detect impacts in one direction or in multiple directions. In the case of a unidirectional impact sensor, it is contemplated that two or three unidirectional impact sensors are provided that are arranged to detect impacts in different directions, thereby enabling the electronic processor 24 to determine the orientation of the impact based on which impact sensor(s) are triggered. As shown in FIG. Figure 1 As shown, the (illustrative single) impact sensor 30 is a passive normally open impact sensor, which includes at least one spring contact 32, which is configured to vibrate so that the electrical contact generates one or more current pulses when the battery pack 12 is impacted (and therefore the multiple battery cells 18 contained in the battery pack 12 are indirectly impacted). More specifically, the impact sensor 30 includes a plurality of spring contacts 32, each of which has a different stiffness level. Each spring contact 32 is normally open, that is, it will not contact and conduct current in the absence of an impact. The spring contact 32 is activated by an impact that is large enough to cause the spring to vibrate and make contact, thereby conducting current. Optionally, the normally open impact sensor 30 includes debouncing (e.g., using frequency filtering, Schmitt triggers, SR triggers, etc.) to prevent rapid current oscillations generated in response to impact vibrations. The electronic processor 24 is programmed to determine the magnitude of the impact based on which (which) spring contacts 30 are triggered. The stiffness level can be selected according to any suitable standard (e.g., UN / DOT38.3, IEC62133-2, and / or MIL-STD-810E). The normally open shock sensor 30 does not conduct current (and therefore does not consume any power) unless an impact is detected that exceeds the stiffness of the spring contact 32. Thus, the use of a normally open shock sensor can prevent additional current from being drawn from the battery cell 18 during transportation and storage.

[0027] In some embodiments, the impact sensor 30 is operatively connected to an accelerometer 34 that is configured to measure movement of the battery pack 12. In this arrangement, the normally open spring contact(s) 32 are connected to a "wake-up" pin (or interrupt pin or other similarly named input) of the accelerometer 34 to activate the accelerometer 34 to measure the magnitude of an impact to the plurality of battery cells 16. The accelerometer 34 is in a sleep mode or some other low power mode unless / until the spring contact(s) 32 triggers the wake-up pin (or interrupt pin, etc.) to activate the accelerometer measurement, again ensuring that minimal power is consumed by the battery cell(s) 18 during shipping and storage. The accelerometer 34 can be any suitable accelerometer (e.g., a 3-axis ADXL345 accelerometer available from Analog Devices of Norwood, Massachusetts).

[0028] In other embodiments, the at least one fault detection sensor can additionally or alternatively include at least one gas sensor 36 configured to measure or detect a fault including gas escaping from the plurality of battery cells 18. Figure 1 As shown, at least one gas sensor 36 is disposed near at least one exhaust port 38 of the housing 16. In some examples, the at least one gas sensor 36 includes a first gas sensor 36′ and a second gas sensor 36′.

[0029] ', the first gas sensor 36' is configured to measure hydrogen and the second gas sensor 36" is configured to measure at least one of benzene, methane, and propylene (e.g., escaping from degraded polypropylene). In other examples, a single gas sensor 36 can be implemented to measure each of these gases. The first gas sensor 36' can be, for example, an SR-H04-SC device available from Honeywell of Morris Plains, New Jersey, and the second gas sensor 36" can be, for example, an MP7217 device available from SGX Sensortech of High Wycombe, England.

[0030] The battery management system 20 optionally includes various other components and / or alternative components. For example, the battery management system 20 may include at least one wireless transmitter or transceiver 44 (in addition to or in place of a set of data contacts of contacts 23, 23') to allow the battery management system to wirelessly transmit data measured by at least one gas sensor 36 and / or impact sensor 30 and an identification of the battery pack (e.g., a serial number). In other examples, the battery management system 20 also includes a temperature sensor 46, which is operatively connected to at least one electronic processor 24 and is configured to measure the temperature of a plurality of battery cells 18. The memory 48 is configured to store data measured by the temperature sensor 46, at least one gas sensor 36, and / or the impact sensor 30. The memory 48 may be integrated with at least one electronic processor 24, or may be an auxiliary component (e.g., a separate non-volatile memory chip connected to the processor 24 via a printed circuit). The medical device 14 is configured to read the data stored in the memory 48 when the battery pack 12 is connected to the medical device. Housing 16 encloses battery cells 18 and components of battery management system 20 (e.g., at least one electronic processor 24, shock sensor 30, accelerometer 34, and gas sensor(s) 36). Battery pack 12 can also include a display for displaying visual messages and a speaker for outputting audio messages related to the operation of the battery pack.

[0031] The battery management system 20 is configured to perform remedial actions in response to the impact sensor 30 and / or the (one or more) gas sensor 36 detecting a fault. In some embodiments, when the fault detection sensor includes the impact sensor 30, the remedial actions performed by the battery management system 20 in response to the impact sensor 30 detecting the impact can include, for example: (i) shutting down the plurality of battery cells 18 when the impact to the plurality of battery cells 18 exceeds a predetermined impact threshold (e.g., via triggering the fuse 28); (ii) storing the occurrence of the impact in the memory 48 when the impact to the plurality of battery cells is below the predetermined impact threshold; and / or (iii) generating a visual or audio message indicating that the plurality of battery cells need to be replaced; and generating (via a corresponding one of the display or speaker) a visual or audio message indicating that the medical device 14 should be replaced with a new medical device, etc. In other embodiments, when the fault detection sensor includes the (one or more) gas sensor 36, the remedial actions performed by the battery management system 20 in response to the (one or more) gas sensor 36 detecting gas escaping from the plurality of battery cells 16 include triggering the fuse 28 or otherwise immediately shutting down the battery pack when hydrogen or other gas is detected. In such cases, it is generally best to shut down immediately, as the detection of gas may indicate incipient TRA, which is an emergency situation that is best remedied by battery shutdown. In the case of Class III medical devices providing life-critical services to patients, the response to the detection of gas may also include generating a visual or audio message on the medical device (e.g., powered by an emergency storage capacitor, etc.) indicating that the battery pack needs to be replaced immediately.

[0032] The appropriate remedy for a given fault magnitude or fault detection sequence is properly calibrated empirically in the laboratory. For example, various test battery packs can be subjected to various magnitudes of impact and then accelerated aging applied to the battery pack failure modes resulting from such impacts. Likewise, various test battery packs can be subjected to various impact sequences to evaluate the resulting failure modes.

[0033] To calibrate the gas sensor(s) 36, background sensor signals in the environment inside the housing 16 are appropriately measured to determine a sufficiently high fault detection threshold to avoid false fault detections; and likewise, the gas sensor signals when gas is being evolved due to an incipient failure of a battery cell are empirically determined by subjecting the test battery pack to various failure modes. In some contemplated embodiments, the gas sensor(s) 36 are combined with appropriate signal processing performed by the microprocessor 24 to detect failures based on the rate of change of the gas sensor signals, since incipient battery cell failures are expected to produce rapidly increasing concentrations of evolved gas.

[0034] refer to Figure 2, an illustrative embodiment of a fault detection and remediation method 100 is illustrated in a flowchart. At 102, a fault is detected. At 104, a remedial action is determined. At 106, a remedial action is performed. The remedial action can include at least one of the following: shutting down the plurality of battery cells (18) when an impact to the plurality of battery cells exceeds a predetermined impact threshold; storing the occurrence of the impact in a memory (48) when the impact to the plurality of battery cells is below a predetermined impact threshold; generating a visual or audio message indicating that the plurality of battery cells need to be replaced; and generating a visual or audio message indicating that a medical device (14) powered by the battery pack should be replaced with a new medical device.

[0035] The present disclosure has been described with reference to preferred embodiments. Others may think of modifications and substitutions upon reading and understanding the above detailed description. It is intended that the present disclosure be interpreted as including all such modifications and substitutions as long as they fall within the scope of the claims and their equivalents.

Claims

1. A battery pack (12), comprising: one or more battery cells (18); A battery management system (20) comprising at least one electronic processor (24) configured to monitor a parameter of the battery pack; At least one fault detection sensor comprising at least an impact sensor (30) configured to measure an impact to the battery pack; as well as an accelerometer (34) operatively connected to the impact sensor (30), the impact sensor (30) being configured to activate the accelerometer to measure a magnitude of the impact to the plurality of battery cells; as well as a housing (16) enclosing the plurality of battery cells, the battery management system and the at least one fault detection sensor; wherein the battery management system is configured to perform remedial action in response to the at least one fault detection sensor detecting a fault, The remedial action performed by the battery management system (20) in response to the impact sensor (30) detecting the impact includes at least two of the following: shutting down the plurality of battery cells when the impact on the one or more battery cells (18) exceeds a predetermined impact threshold; storing the occurrence of the impact in a memory (48) when the impact on the plurality of battery cells is below the predetermined impact threshold; generating a visual or audio message indicating that the plurality of battery cells need to be replaced; and A visual or audio message is generated indicating that a medical device (14) powered by the battery pack should be replaced with a new medical device.

2. The battery pack (12) according to claim 1, wherein: The impact sensor (30) is a passive impact sensor including at least one spring contact (32) configured to vibrate in response to an impact on the one or more battery cells (18) to generate one or more current pulses.

3. The battery pack (12) according to claim 2, wherein: The passive impact sensor (30) includes a plurality of spring contacts (32) having different stiffness levels, and The at least one electronic processor (24) is programmed to determine a magnitude of the impact to the one or more battery cells (18) based on which spring contact or contacts are triggered.

4. The battery pack (12) according to claim 1, wherein: The at least one fault detection sensor also includes at least one gas sensor (36) configured to detect a fault including gas escaping from the one or more battery cells (18).

5. The battery pack (12) according to claim 4, wherein: The at least one gas sensor (36) comprises: a first gas sensor (36') configured to measure hydrogen gas; and A second gas sensor (36") is configured to measure at least one of hydrogen, benzene, methane, and propylene.

6. The battery pack (12) according to claim 4, wherein: The remedial action performed by the battery management system (20) in response to the at least one gas sensor (36) detecting gas escaping from the one or more battery cells (18) includes shutting down the one or more battery cells.

7. The battery pack (12) according to claim 4, wherein: The housing (16) includes at least one exhaust port (38), and the at least one gas sensor (36) is disposed adjacent to the at least one exhaust port.

8. The battery pack (12) according to any one of claims 1 and 4, wherein: The battery management system (20) includes at least one wireless transmitter or transceiver (44), and the battery management system is programmed to wirelessly transmit: data measured by the at least one fault detection sensor (30, 36); and An identification of the battery pack.

9. The battery pack (12) according to claim 1, wherein: The battery management system (20) further comprises: a temperature sensor (46) operatively connected to the battery management system (20) and configured to measure the temperature of the one or more battery cells, the housing (16) also enclosing the temperature sensor; and A memory (48) is configured to store data measured by at least one of the temperature sensor and the at least one fault detection sensor (30, 36).

10. A device (10), comprising: Medical equipment (14); as well as The battery pack (12) according to claim 9, connected to the medical device to supply power to the medical device; The medical device is configured to read the data stored in the memory (48) when the battery pack is connected to the medical device.

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