Patent Application
20190305386
The technical field of this disclosure concerns battery management systems and more particularly concerns battery management systems that are fault tolerant.
Lithium-ion (Li-ion) batteries are growing in popularity as energy storage reservoirs for industrial and automotive applications, high-voltage energy uses (smart grid), such as wind turbines, photo-voltaic cells, and hybrid electric vehicles. Large-scale lithium-ion battery systems for hybrid/electric vehicles (xEV) or large-capacity energy storage systems (ESS) consist of a multiplicity of battery cells which are assembled together to form battery modules or battery packs. A large scale battery system can comprise many of these battery modules or battery packs.
The growing popularity of large scale lithium-ion battery systems has spurred demand for safer, higher performing battery monitoring and protection systems. Battery stacks using Li-Ion technology can comprise a large number of individual cells totaling hundreds of cells at different voltages. Each cell must be properly monitored and balanced to ensure user safety, improve battery performance and extend battery life. Therefore, the battery management system (BMS) is one of critical components for small and large-scaled battery applications.
The BMS monitors the voltage, the current, impedance, and the temperature of each cell. Since a BMS has to monitor each and every Li-Ion battery cell, it had been a common practice to wire the BMS to every Li-Ion cell. When the number of Li-Ion cells increases to a few hundred, or up to thousands, which is often the case for electric vehicle (EV) or power plant applications, the wire harness becomes a serious problem. Thus, one of the issues of BMS implementation is wiring. To avoid such problem some BMS systems have used wireless transceivers to facilitate communications between a sensor level node mounted on each battery cell that is wirelessly connected to master-level battery management unit.
This document concerns a BMS which includes several different types of monitoring nodes which function cooperatively to facilitate high reliability redundant sensing. The BMS will include a plurality of master battery management units (M-BMU). Each M-BMU will includes at least one multi cell battery sensing device. The multi cell battery sensing device in each M-BMU is configured to directly sense at least one condition of each battery cell of a group of battery cells that are associated with one battery module. As is known, a large scale battery pack can be comprised of many such battery modules.
The BMS also includes a plurality of sensor battery management units (S-BMU) associated with each of the battery modules. Each of the S-BMU comprise a single-cell battery sensing device and is configured to directly sense one or more conditions associated with a particular battery cell (e.g., voltage, current and/or temperature). Each of the S-BMU associated with a particular battery module is configured to wirelessly communicate data acquired as a result of the direct sensing by the individual S-BMU, to one of the plurality of M-BMU associated with the particular battery module.
In a solution described herein, the S-BMU and the M-BMU are configured to directly sense one or more the same conditions. Consequently, the data acquired as a result of the direct sensing by the M-BMU is redundant as compared to the data acquired as a result of the direct sensing by the S-BMU. In some scenarios, the M-BMU may be configured to compare for each battery cell the data acquired as a result of the direct sensing by the M-BMU and the data acquired as a result of the direct sensing by the S-BMU for that cell.
The M-BMU can also be configured to use the data provided by the plurality of S-BMU and/or the data directly acquired by the M-BMU, to evaluate a status of each battery cell associated with a particular battery module. For example, such evaluation can involve determining a battery state such as a state of charge (SoC) and/or a state of health (SoH). In such scenarios, the M-BMU may be configured to wirelessly communicate the SoC and/or SoH of each battery cell in a particular battery module, to a top-level battery management unit (T-BMU).
According to one aspect of a solution described herein, the M-BMU can be configured to communicate with the plurality of S-BMU in accordance with a first wireless communication protocol, and to communicates with the T-BMU in accordance with a second wireless communication protocol. In such a scenario, the first wireless communication protocol can advantageously be chosen so that it is different from the second wireless communication protocol. Further, each of the M-BMU can include a first wireless transceiver to facilitate the wireless communications with the plurality of S-BMU associated with a battery module, and a second wireless transceiver to facilitate the wireless communications with the T-BMU. Consequently, communications with the S-BMU can occur concurrently with the communications involving the T-BMU.
The M-BMU can communicate to a top-level battery management unit (T-BMU) one or more data types such as (a) raw data acquired as a result of the direct sensing by the M-BMU, (b) raw data acquired as a result of the direct sensing by the S-BMU, (c) SoC data determined for each battery cell associated with the battery module, and/or (d) SoH data determined for each battery cell associated with the battery module. Consequently the T-BMU can compare the SoC data and/or the SoH data provided by the M-BMU to independently determined SoC and/or SoH data estimated by the T-BMU. Such SoC/SoH data determined by the T-BMU can be based on the raw data acquired as a result of the direct sensing by the M-BMU and/or the raw data acquired as a result of the direct sensing by the S-BMU.
In the solution disclosed herein, the M-BMU is configured to facilitate the direct sensing of each battery cell of a particular battery module using a plurality of M-BMU wired connections which couple the M-BMU to the battery cell terminals of each battery cell. Further, each of the S-BMU is configured to facilitate the direct sensing of each battery cell using an S-BMU wired connection. The S-BMU wired connection is physically distinct from the M-BMU wired connection to facilitate an increase in a degree of redundant sensing.
From the foregoing it will be appreciated that an M-BMU in a BMS described herein will serve at least a dual purpose. The dual purpose will include a first purpose in which it functions as a multi cell battery sensing device to facilitate redundant sensing, and a second purpose in which the M-BMU functions as an intermediate level data collection node for a plurality a single-cell battery sensing devices. In some scenarios, the M-BMU can also be configured to serve a third purpose involving a battery cell balancing function.
Further reliability and battery system safety can be facilitated by configuring each M-BMU to comprise a plurality of the multi-cell sensing devices. In such a scenario, the plurality of multi-cell sensing devices are each configured to facilitate within the M-BMU an additional level of redundant direct sensing of the at least one condition. In other scenarios, an additional level of reliability and safety can be added by configuring the M-BMU to include a fault-tolerant multi-cell sensing system on a chip.
The solution also includes a method for redundantly sensing a plurality of batteries in a battery pack. The method involves using at least one multi cell battery sensing device in each of a plurality of M-BMU. The one or more multi cell battery sensing device(s) will directly sense at least one condition of each battery cell within a particular battery module of a battery pack. A plurality of S-BMU respectively individually sense directly at least one condition associated with each of a plurality of battery cells associated with each of the battery modules. The method further involves wirelessly communicating from each of the plurality of S-BMU of a particular battery module, to an M-BMU associated with the particular battery module, data acquired as a result of the individual direct sensing of each battery cell in the particular battery module.
This disclosure is facilitated by reference to the following drawing figures, in which like numerals represent like items throughout the figures, and in which:
It will be readily understood that the solution described herein and illustrated in the appended figures could involve a wide variety of different configurations. Thus, the following more detailed description, as represented in the figures, is not intended to limit the scope of the present disclosure, but is merely representative of certain implementations in various different scenarios. While the various aspects are presented in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
Two known international industrial safety standards include: (1) IEC 61508—entitled “Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems”, and (2) ISO 26262, entitled “Road vehicles—Functional safety”. IEC 61508 is published by the International Electrotechnical Commission (IEC) and is set forth as a basic functional safety standard to ensure the safety of any type of electronic or electrical system. ISO 26262 is an adaptation of IEC 61508 for Automotive Electric/Electronic Systems as set forth by the International Organization for Standardization (ISO). As such, ISO 26262 is intended for ensuring the functional safety of electrical and/or electronic systems in production automobiles.
Functional safety is defined in ISO 26262 as freedom from unacceptable risks, due to hazards caused by malfunctions of an electric/electronic system. Pursuant to the guidelines set forth in ISO 26262, it is mandatory that a component or a system is transferred to a safe state should a failure occur. Several additional criteria emphasized in ISO 26262 are that (1) a system must guard against any single point failure creating a hazard, (2) hazards must be detectable even in the event the primary monitor fails, (3) it is preferable that any redundant circuit is of a less complex design than the primary (4) the redundant components should be independent, and (5) the extent of diagnostic coverage of the components should match the hazard level.
A battery management system (BMS) fundamentally constitutes a safety component of a large-scale battery system. Properly handling such a complex battery system during its entire life cycle can be effectively achieved by utilizing the proper quality and safety management apparatus. In a solution presented herein, the broad safety goals outlined in IEC 61508 and ISO 26263 are effectively and economically achieved in a BMS.
One of the useful solutions disclosed herein involves introducing a degree of redundancy to sensing functionality in a BMS. Such redundancy can reduce the probability that one electronic failure will leave the battery and charging system in a state that allows, or even engenders, a significantly destructive cell mishap. More particularly, a BMS that can continue full, safe operation after any single unrepaired fault (and after most 2nd and third unrepaired faults) can be solved by a system with dually redundant battery sensing and management functional circuitry arranged in independent, fault isolated modules.
The solution disclosed herein is intended to counter the drawbacks of large-capacity battery systems and to satisfy well-known safety requirements. The solution satisfies safety standards without adding significant cost. The redundant sensing solution is: (1) able to issue an alarm for over-voltage (OV), under-voltage (UV) and over-temperature (OT) conditions (separate alarms for each condition are facilitated), (2) operate completely independently of the primary monitor (i.e., separate inputs, supplies, and references) to mitigate single point failures, and (3) provides diagnostics that can validate circuit and alarm operation. In addition to the foregoing, the redundant sensing solution is advantageously configured to comprise (4) a hardware only solution (to mitigate the dependence on software), and (5) the redundant system will work with most Li-ion chemistries available for mass production. A final key aspect of the solution is that it is (6) cost-effective. In this regard, the added cost of the redundant sensing solution will be only a fraction of the cost of the primary sensing system.
A drawback of the configuration in
The FTBS 200 includes a plurality of redundant cell monitoring or sensing components and a built-in multiple-step sensing validation test. More particularly, the FTBS system 200 is comprised of an N-cell battery sensor (where N is an integer value greater than 1). The N-cell battery sensor is comprised of a plurality of identical sensing channels SC1, SC2 . . . SCT. Each sensing channel is responsible for voltage measurements of M battery cells 201 (where M is an integer value greater than 1). As such, each sensing channel includes a switching array 204, analog signal processing (ASP) circuitry 206, a main ADC 208 and a redundant ADC 210. The FTBS system further includes an isolated power management unit 202 with dual reference voltage generators, dual analog-to-digital converters, and a ‘SUM of M-cell in a sensing channel’ measurement circuitry (not shown in
One or more of the sensing channels SC1 SC2 . . . SCT is/are designated as backup or auxiliary sensing channels. These backup or auxiliary sensing channels are provided so that they can, if necessary, can take on the role of a sensing channel that develops a fault and therefore does not operate properly. Accordingly, a backup or auxiliary sensing channel can be understood to be one of the sensing channels SC1, SC2 . . . SCT that is in excess of those that are needed by the FTBS system to perform battery sensing of the N cells.
A digital core 218 controls the measurement operations. The digital core 218 receives sensing data from a main ADC 208 and a redundant ADC 210 of each sensing channel. This sensing data is communicated to the digital core 218 through capacitive couplings 214, 216 and confirms the validation of sensory data. The capacitive couplings provide galvanic isolation between each sensing channel and the digital core unit. The galvanic isolation involves using differential high-voltage capacitors that capacitive couple digital-type AC signals from the digital core to the sensing channel, or vice versa while effectively sustaining high common-mode voltages.
In
The solution shown in
Shown in
As explained below in greater detail, the WiBaAN in
In the system shown in
A second 1:S wireless communication network is formed between each M-BMU and a plurality (S) of S-BMUs in the lower level. A large-capacity battery pack for an electric vehicle is composed of a plurality of battery modules. One M-BMU and one of the second wireless networks can be provided for each battery module. Accordingly, in some scenarios the number of M-BMUs and the number of second wireless networks associated therewith can be determined by the number of battery modules in a large-capacity battery pack. From the foregoing it may be understood that a relatively large number of the second wireless networks may be present in a BMS which manages are large-capacity battery pack. Consequently, the second wireless networks can in some scenarios require the implementation of a WiBaAN protocol that minimizes communication interference between multiple second wireless networks. In addition, the wireless protocol used for such network is advantageously designed to minimize communication collisions and data loss between the first and second wireless networks. The higher node of the network architecture usually operates with a longer interval of control and execution time than its immediately lower layer.
According to one aspect of a solution disclosed herein, each S-BMU 306 is advantageously a single-cell sensing device. In some scenarios, individual S-BMUs may be mounted in or directly on a corresponding battery cell. As such, each S-BMU can be arranged to directly sense the environment and one or more conditions associated with a particular battery cell 402. Of course, the solution is not limited in this regard and in other scenarios a single S-BMU can be configured to acquire data from two or more individual battery cells. As used herein, the term “directly sense” or “directly sensing” as applied to the function of the S-BMU shall mean that the actual sensing or measurement function of a battery related condition is performed by the S-BMU.
The battery data relating to one or more conditions associated with a particular battery cell 402 are collected by an S-BMU 306 and then wirelessly communicated to an M-BMU 304 at the next higher level of the network hierarchy. According to one aspect, each M-BMU 304 will collect battery cell data communicated from the plurality of S-BMU 306 that are associated with a particular battery module 404. As shown in
In addition to its role as a data collection node, each M-BMU 304 is also a multi-cell sensing device that is independently wired to the battery module 404. As explained below in further detail, each M-BMU 304 is configured to directly sense the individual status of a plurality of battery cells 402 associated with a battery module 404. As used herein, the term “directly sense” or “directly sensing” as applied to the operations of the M-BMU shall mean that the actual sensing or measurement function of a battery related condition is performed by the M-BMU. In this regard M-BMU 304 will independently directly acquire measurement data for one or more conditions associated with each of the individual battery cells 402 that together make up a particular battery module 404. Because this data is acquired directly by the M-BMU separately from the data that is directly acquired by each S-BMU, the two data sets are independent.
In some scenarios, the M-BMU can compare the data it collects directly from the battery module 404 with the data collected by each of the S-BMUs. For example, such a comparison may be useful in some scenarios to evaluate whether each battery cell is operating safely. Further, the M-BMU can in some scenarios calculate for each battery cell a State of Charge (SoC) and/or a State of Health (SoH) of the battery. The SoH is a figure of merit of the condition of a cell compared to its ideal condition. SoC is sometimes defined as the available capacity (in Amp-hours) expressed as a percentage of the rated capacity of the cell.
One or more of the SoH, the SoC, and the battery data acquired by the S-BMU and/or the M-BMU can be transmitted wirelessly to the T-BMU. In some scenarios, the T-BMU can perform calculations based on the raw data from the S-BMU and/or M-BMU to independently determine SoC and SoH metrics for each cell 402. Further, the T-BMU can compare the SoC and/or SoH values that it calculates to the SoC and/or SoH values which are calculated at the M-BMU nodes. Consequently, the T-BMU can independently evaluate the condition of each battery cell, and cross-check its results with the results obtained at the M-BMU level. If significant differences are determined between the values calculated by the M-BMU and the T-BMU then a fault condition signal can be generated by the T-BMU.
In the BMS solution described herein the sensing device of the M-BMUs operates completely independent of the sensing device of the S-BMU—separate input terminals, supplies, and reference voltage generations. Consequently, the likelihood of a single point failure is greatly reduced. The WiBaAN provides a BMS with high flexibility, highly reliability and secure wireless network communications facilitated by the first wireless network and the second wireless network. Accordingly, success of the redundant sensing is ensured.
Single battery cell sensing circuits are well-known in the art and therefore SC sensor 502 will not be described here in detail. However, it will be appreciated that the SC sensor 502 can be configured to measure various conditions associate with an individual battery cell such as the cell's voltage, current and temperature. As such, the SC sensor 402 can comprise power management circuits, analog switching circuitry, measurement signal conditioning circuitry coupled to the analog switching circuitry, and at least one analog to digital converter (ADC). The SC sensor 402 can also include a processing element to control the operation of the S-BMU. For example, the processing element can be comprised of a microcontroller, an application specific circuit, a programmable logic device, other type of electronic circuit programmed to perform the functions described herein. These components are omitted in
The sensing data acquired by the SC sensor 502 can be transmitted to the upper-level M-BMU via wire harness, but in order to enhance flexibility and convenience of a BMS disclosed herein, the measurement data is advantageously communicated wirelessly to the M-BMU using the wireless radio transceiver 506. In some scenarios, the S-BMU 306 can be used to facilitate a passive cell balancing function. However, so as to minimize any potential thermal issues, it can be advantageous to exclude such passive cell balancing functions from the S-BMU.
Shown in
According to one aspect, each M-BMU 304 can compare its own sensing data to the data transmitted from the S-BMUs for a particular battery module 404. This data can be used to determine whether the battery cells 402 and/or the S-BMU 306 are experiencing a fault condition. In
All the power taps of the cells in one battery module 404 are wired to the M-BMU 304 associated with that battery module. These direct wired connections can facilitate direct measurement of cell voltage, temperature and current. An added advantage of this arrangement is that the M-BMU can perform charge balancing for the cells associated with a particular battery module 404. Cell balancing ensures that each cell in a battery module maintained at a healthy battery state of charge (SoC), thereby preventing damage due to excessive discharging or overcharging. Passive balancing simply dissipates excess charge in a bleed resistor, whereas active cell balancing redistributes charge between battery cells during the charge and discharge cycles. Cell balancing techniques are well-known in the art and therefore will not be described here in detail. Charge balancing performed at the M-BMU avoids excess heat buildup which might otherwise occur if the charge balancing was performed by the S-BMU at each cell.
In the M-BMU 304 the inputs from the battery cells are processed in a charge balancing and low-pass filtering block 702. The inputs are then measured in a multi-cell sensing device 704. These measurements can include voltage, current and/or temperature. This data is then transmitted to a T-BMU using wireless transceiver 706 under the control of a master control unit 708. The wireless RF transceiver 706 communicates the data to a higher-level T-BMU node. In order to increase the degree of redundant sensing, an additional multi-cell sensing device 710 can be added to the M-BMU circuit board as shown in
The M-BMU 804 shown in
The M-BMUs in
The frequency band and channel to be used and the modulation type for the wireless communication described herein are determined in advance, or dynamically changed based on the communication circumstances. The second wireless networks between each M-BMU and the S-BMU associated with a particular battery module) feature a relatively short transmission distance. Accordingly, these second wireless networks can take utilize a relatively simple network architecture, short in data length and may be somewhat isolated electrically by the battery module jackets. A simple and low-power communication scheme, such as Amplitude Shift Keying (ASK), can be used in such scenarios. Of course, ASK is merely one possible keying technique and the solution is not intended to be limited in this regard. On the other hand, for purposes of implementing the first wireless network between the M-BMU and the T-BMU, various additional factors must be considered. These factors can include the communication distance, the amount of data to be communicated, the complexity of the internal structure of the battery pack, and the avoidance of external interference. Taking these factors into consideration, it can be advantageous to use a more complex and reliable wireless communication scheme for the first wireless network.
To ensure greater reliability, separate radio hardware can be used to implement the first and second wireless networks. For example, an M-BMU 814 shown in
In the various BMS implementations described herein, a complete failure of a wireless transceiver (e.g., RF transceiver 706) in an M-BMU could potentially cause an interruption in the monitoring and balancing operations for a particular battery module. This is due to the fact that the M-BMU serves as a central data collection and data forwarding node for each S-BMU within a particular battery module. To facilitate a further level of safety and protection, such potential interruptions can be avoided by causing the S-BMU in each module to communicate directly with the T-BMU under certain conditions. For example, consider a scenario involving a failure in an M-BMU 304 which prevents the M-BMU for a particular battery module from communicating with the T-BMU 302. Under such conditions, each S-BMU within such battery module can revert to a safety mode in which such S-BMUs will wirelessly communicate directly with a T-BMU.
To facilitate such capability, the RF transceiver 414 in the T-BMU can be configured to periodically communicate with the S-BMU in accordance with a wireless protocol that is normally used by the S-BMU to communicate with the M-BMU. Alternatively, the S-BMU can be configured to communicate with the T-BMU in accordance with the wireless protocol that is normally used by the T-BMU to communicate with the M-BMU. This would represent a failsafe mode to ensure that data for cells 402 in a particular battery module 404 are reported to the T-BMU 302 in the absence of an operational M-BMU for that battery module. The failsafe communication mode could be initiated by the T-BMU when it detects a problem with the S-BMU and/or the S-BMU detects a communication problem with the M-BMU. As a further alternative, an M-BMU that detects a failure could alert that T-BMU and/or M-BMU that they need to communicate in accordance with the failsafe mode described herein.
The described features, advantages and characteristics disclosed herein may be combined in any suitable manner. One skilled in the relevant art will recognize, in light of the description herein, that the disclosed systems and/or methods can be practiced without one or more of the specific features. In other instances, additional features and advantages may be recognized in certain scenarios that may not be present in all instances.
As used in this document, the singular form “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. As used in this document, the term “comprising” means “including, but not limited to”.
Although the systems and methods have been illustrated and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Thus, the breadth and scope of the disclosure herein should not be limited by any of the above descriptions. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents.
This application claims the benefit of U.S. Provisional Application No. 62/649,481 filed on Mar. 28, 2018 which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62649481 | Mar 2018 | US |
