Patent Application
20200335831
The technical field of this disclosure concerns battery management systems, and more particularly concerns methods and systems which facilitate management of large scale battery systems.
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. This growing popularity 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, conventional 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.
The automobile industry is a key market with respect to battery management systems. Within this market, safety considerations and the need to protect expensive battery cells are causing manufacturers to demand faster data update times with respect to the state of charge (SOC) of each battery cell. For example, rather than being satisfied with updates every 50 milliseconds, as was acceptable in older systems, manufacturers are beginning to demand data updates on each battery cell at least every 10 milliseconds. The technical challenge with older two-layer BMS network hierarchies is that a master-level node cannot cycle through communications with all of the sensor-level nodes, and report same, at a rate that is high enough to satisfy the faster data update time requirement specification. There are simply too many batteries.
This document concerns a battery management system for collecting data concerning battery cells in a battery pack, where the battery pack comprises a multiplicity of battery cells. The battery management system (BMS) includes a plurality of sensor nodes (S-BMU). Each of the sensor nodes is configured to be connected to at least one corresponding battery cell of a battery pack. Each sensor node will include at least one sensor which is configured to facilitate measurement of a battery cell characteristic. The BMS also includes one or more master nodes (M-BMU), each configured to communicate with the plurality of sensor nodes. The master nodes communicate with the sensor nodes in a at least a first communication session which involves requesting from the plurality of sensor nodes battery cell data representative of the battery cell characteristics. During such session, the master node will also receive the battery cell data from the plurality of sensor nodes. The BMS also includes at least one top level node (T-BMU). The top level node is configured to communicate with the one or more master nodes in at least a second communication session. In this second communication session, the top level node receives the battery cell data from the one or more master nodes. To facilitate improved data acquisition times, the one or more master nodes are each configured to conduct the first communication session concurrent with the second communications session.
To facilitate these concurrent communications, the master nodes will comprise a first data transceiver configured to facilitate the first communication sessions with the plurality of sensor nodes, and a second data transceiver different from the first data transceiver, that is configured to concurrently facilitate the second communication sessions. According to one aspect, the first data transceiver is a wireless transceiver. The second data transceiver can be either a wired transceiver and a wireless transceiver. In some scenarios, the at least one master node and the top level node share a common electrical ground, and under these conditions the second data transceiver is advantageously selected to be a wired transceiver.
Each of the sensor nodes can be configured to redundantly communicate the battery cell data. For example, this can involve resending identical battery cell data respectively to a plurality of the master nodes during a plurality of predetermined time periods. According to one aspect of the solution, a timing offset can be assigned to one or more of the sensor nodes. The timing offset can be selected so as to cause the first communication session of each said sensor node with a particular one of the master nodes to be offset in time relative to the first communications sessions of others of the sensor nodes with the particular master node. As such, the timing offset can be selected to have a duration that is equal to at least one of the predetermined time period or time slot, and an integer multiple of the predetermined time period or time slot.
In some scenarios, more than one of the master nodes can be configured receive the battery cell data from each of the sensor nodes contained in the battery pack during a battery management session. In such instances, each of the plurality of master nodes can be configured to communicate the battery cell data received from each of the sensor nodes in the battery pack to the at least one top level node. Consequently, the top level node receives redundant battery cell data from the plurality of master nodes.
The master nodes can be configured to determine at least one of a state-of-charge (SoC) and a state-of-health (SoH) of the battery cells associated with each of the sensor nodes from which it receives battery cell data. Each of the master nodes in such a scenario then can be further configured to communicate the battery cell data, the SoC and/or SoH to the at least one top level node. In other scenarios, each of the sensor nodes is configured to determine the SoC and SoH of a battery cell to which it is connected. Such SoC and SoH data can then be communicated to a master node, and ultimately to a top level node.
According to one aspect, the top level node is advantageously configured to use the battery cell data received from at least one of the master nodes to calculate one or both of the SoC and the SoH of each battery cell. Note that this can be a redundant calculation in those scenarios where the SoC or SoH has already been calculated in a sensor cell or a master cell. In such a scenario, the top level node can be advantageously configured to compare at least one of the SoC and the SoH that has been calculated at the top level node, to at least one of an SoC or SoH calculated in a master node or a sensor level node for a corresponding battery cell. This process, whereby a comparison of SoC or SoH values calculated for a particular battery cell at two different nodes, can facilitate system reliability by providing a means to verify the accuracy of the SoC and/or SoH at the top level node.
The solution can also involve a method of acquiring battery cell data from a multiplicity of battery cells in a battery pack. Such a method can involve using a plurality of sensor nodes, which are respectively connected to a plurality of battery cells of the battery pack to periodically determine battery cell data for each battery cell. Thereafter, a first communication session can be established between each sensor node and each of one or more master nodes to receive in each of the one or more master nodes the battery cell data for each of the plurality of battery cells. Further, a second communication session can be established between at least one top level node and each of the one or more master nodes to obtain the battery cell data for each battery cell which has been received by the one or more master nodes. Advantageously, a data acquisition time for the battery pack can be minimized by configuring each of the one or more master nodes to perform the second communication sessions concurrent with the first communication sessions.
In the foregoing method, a first data transceiver of each master node can be used to facilitate each of the first communication sessions, and a second data transceiver of each master node can be used to concurrently facilitate each of the second communication sessions. A wireless communication mode is advantageously used to facilitate each of the first communication sessions. A communication mode for the second communication sessions can be either a wired or a wireless communication mode. However, where the one or more master nodes and the top level node share a common electrical ground, a wired communication mode is advantageously used to facilitate each of the second communication sessions.
The method can further involve redundantly communicating identical battery cell data from each of the plurality of sensor nodes, to each of a plurality of master nodes during a plurality of predetermined time periods. In some scenarios this can involve applying a timing offset to one or more of the sensor nodes to cause the first communication session of each said sensor node with a particular one of the master nodes during the predetermined time period to be offset in time relative to corresponding first communications sessions of others of the sensor nodes with the particular master node.
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.
One step toward satisfying the faster update times needed in a BMS can involve the utilization of a three-level or three-tier hierarchical network structure as disclosed in U.S. Pat. No. 9,293,935, the disclosure of which is incorporated herein by reference. Within such hierarchical network systems there are sensor-level nodes which acquire battery data directly from the battery cells, master-level nodes which receive and collect data from the sensor-level nodes, and top-level nodes which collect data from the master-level nodes and report same to a monitoring system, such as a system computer. The three-layer hierarchy divides the communication load with sensor-level nodes among many master-level nodes, and then consolidates this information in the top-level node. The various nodes within the hierarchical network can communicate using wireless or wired communications protocols.
An example of a hierarchical star network topology used in a conventional wireless battery area network (WiBaAN) is shown in
Notably, each S-BMU can be configured to repeatedly transmit the same data several times during a particular time slot in order to increase communication reliability. This is illustrated in
Each wireless battery module network 1021 . . . 102X operates concurrently with other battery module networks 1021 . . . 102X. An S-BMU reporting cycle includes reporting to a corresponding M-BMU by all of the S-BMU in a particular wireless battery module network 1021 . . . 102X.
T
DAT
=n*r*X*T+t(MT)
where
n=the total number of S-BMUs in a battery module network,
r=the number of repeated data transmission between a S-BMU and a M-BMU,
X=the number of M-BMUs in a particular WiBaAN,
T=unit data packet length (unit time slot length), and
t(MT)=a data packet length between a M-BMU and a T-BMU.
From the foregoing it may be understood that a three-tier battery management system has certain advantages for improving the rate at which data is acquired with respect to each battery cell in a battery pack. But the use of three-tier battery management systems by itself can in some scenarios be insufficient to facilitate the faster update times that are needed for monitoring each cell in a battery pack comprising hundreds or thousands of cells. The need for redundant transmissions to prevent data loss in a noisy communications environment, and inefficient use of sensor-level node communications capabilities can limit data throughput. Consequently, the desired rate at which updates can be provided with respect to each battery cell may not be achieved.
The solution involves a battery management system in which master-level nodes have dual data transceivers to facilitate concurrent communications with sensor-level nodes and top-level nodes. This arrangement, when combined with other techniques described herein, that facilitate more efficient use of the sensor-level nodes, can provide improved rates of battery data updates. Shown in
The WiBaAN in
It should be noted that the exact communication protocols which are employed by the wireless and/or wired communications transceivers in
The dual transceiver configurations shown in
In accordance with the timing diagram of
Similarly, battery cell data is communicated from each S-BMU 302X1 . . . 302Xn to an M-BMU 404X during a reporting cycle 506 of a battery module network 402X. This battery data is then communicated by the M-BMU 404X to the T-BMU 406 during the next reporting cycle 508 associated with the battery module network, during a time slot 516. Since the M-BMU uses separate transceivers to communicate with the S-BMU and the M-BMU, the communications of the M-BMU with the S-BMU and the T-BMU can occur concurrently. In some scenarios, the transmissions between the T-BMU 406 and each of the M-BMU can be coordinated so that the reports from different M-BMU to the T-BMU do not overlap in time.
With the foregoing arrangement, communications between each M-BMU to the T-BMU can occur concurrently with M-BMU communications with the plurality S-BMU. For each battery module network, the data transmission from the M-BMUs to the T-BMU can occur during an S-BMU reporting cycle following the reporting cycle during which the M-BMU has acquired the battery cell data. As a result, the total data acquisition time is reduced to:
T
DAT
=n*r*X*T.
where
n=the total number of S-BMUs in a battery module network,
r=the number of repeated data transmission between a S-BMU and a M-BMU,
X=the number of M-BMUs in a particular WiBaAN, and
T=unit data packet length (unit time slot length).
The data acquisition time of a WiBaAN can be further improved by combining the dual transceiver arrangement described in
Accordingly,
In order to appreciate the advantage of the generalized configuration shown in
In the scenario described with respect to
Turning now to
The reporting cycle of each S-BMU will comprise a predetermined time period, and this reporting cycle of the S-BMU will repeat after the S-BMU has communicated its battery data to each of the M-BMUs. For example, a reporting cycle 902 of an S-BMU S1 is shown in
Notably, with the timing configuration in
From the foregoing it will be understood that one or more the M-BMU M1-M3 can be configured receive (during a battery management session) the battery cell data from each of the S-BMU S1-S4 in a battery pack. Each of the M-BMU can be configured to communicate the battery cell data received from each of the S-BMU S1-S4 in the battery pack to the one or more T-BMU. Consequently, the T-BMU will receive redundant battery cell data from the plurality of master nodes. According to one aspect, each of the M-BMU M1-M3 can be configured to determine at least one of a state-of-charge (SoC) and a state-of-health (SoH) of the battery cells associated with each of the S-BMU. Each of the M-BMU M1-M3 in such a scenario then can be further configured to communicate with the battery cell data, the SoC and/or SoH to the T-BMU. In other scenarios, each of the S-BMU S1-S4 may be configured to determine the SoC and SoH of a battery cell to which it is connected. Such SoC and SoH data can then be communicated to an M-BMU, and ultimately to a T-BMU.
According to one aspect, a T-BMU is configured to use the battery cell data received from at least one of the M-BMUs M1-M3 to calculate one or both of the SoC and the SoH of each battery cell. Note that this will be a redundant calculation in those scenarios where the SoC or SoH has already been calculated in an S-BMU or an M-BMU M1-M3. In such a scenario, the T-BMU can be advantageously configured to compare at least one of the SoC and the SoH that has been calculated at the T-BMU, to an SoC or SoH which has been previously calculated in an M-BMU or an S-BMU for a corresponding battery cell. This process, whereby a comparison is performed with respect to the SoC or SoH values calculated for a particular battery cell at two different nodes, can facilitate system reliability. In particular, it provides a means to ensure that an SoC and/or SoH which has been calculated at the T-BMU is consistent with corresponding values calculated at the lower level nodes.
The WiBaAN described herein is flexible in terms of the number of components constituting each network and the link between constituent elements, so that it is easy to apply to any physical structure of the battery packs. A further advantage of the arrangement is that it is easily scalable. Further, it is relatively easy to configure network scheduling, network ID management and control of frequency hopping. From the foregoing it will be understood that the system is advantageous to use in a WiBaAN application that requires a very fast sensory data acquisition time.
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.
