Abstract: A method for determining respective thermal characteristics of a plurality of electrochemical cell assemblies in an energy storage system includes (1) sensing open circuit voltage of each electrochemical cell assembly of the plurality of electrochemical cell assemblies over a measurement time period, (2) controlling temperature control equipment of the energy storage system to change a temperature setpoint of a heat transfer fluid during the measurement time period, (3) generating a respective voltage profile for each electrochemical cell assembly, (4) determining a respective electrical time constant for each electrochemical cell assembly from the respective voltage profile for the electrochemical cell assembly, and (5) determining a respective thermal characteristic for each electrochemical cell assembly at least partially based on the respective electrical time constant for the electrochemical cell assembly.

Abstract: A method for determining a temperature characteristic of an electrochemical cell assembly includes (1) sensing a first voltage via one or more thermistors electrically coupled to the electrochemical cell assembly while loading circuitry electrically coupled to the thermistors is deactivated, (2) sensing a second voltage via the one or more thermistors while the loading circuitry is activated, and (3) determining the temperature characteristic of the electrochemical cell assembly at least partially from the first and second voltages.

Abstract: Described herein are methods and systems for detecting variation in minor total-impedance contributors in sets of electrochemical cells. For example, a method comprises maintaining a substantially constant current through the set of electrochemical cells and obtaining multiple voltage readings of the cells while the substantially constant current is maintained. The method then proceeds with determining multiple differential capacity values from the multiple voltage readings, characterizing one or more peaks in the multiple differential capacity values, and determining the variation in the minor total-impedance contributor based on one or more peaks. More specifically, partial capacitance values can be assigned to different impedance channels based on these peaks or, more specifically, based on the separation of adjacent peaks.

Abstract: A method for thermal management performed by a controller of an energy storage system, where the energy storage system includes at least a first battery module, a second battery module, a first battery management system (BMS) node, and a second BMS node. The first BMS node is configured to control operation of the first battery module, and the second BMS node is configured to control operation of the second battery module. The method includes (a) determining a first temperature profile difference representing a difference between an actual temperature profile of the first battery module and a desired temperature profile of the first battery module, (b) determining a first operation adjustment representing a desired change in operation of the first battery module for decreasing the first temperature profile difference, and (c) controlling the first BMS node to change operation of the first battery module according to the first operation adjustment.

Abstract: Described herein are methods and systems for detecting variation in minor total-impedance contributors in sets of electrochemical cells. For example, a method comprises maintaining a substantially constant current through the set of electrochemical cells and obtaining multiple voltage readings of the cells while the substantially constant current is maintained. The method then proceeds with determining multiple differential capacity values from the multiple voltage readings, characterizing one or more peaks in the multiple differential capacity values, and determining the variation in the minor total-impedance contributor based on one or more peaks. More specifically, partial capacitance values can be assigned to different impedance channels based on these peaks or, more specifically, based on the separation of adjacent peaks.

Abstract: Described methods and systems are used for in-situ impedance spectroscopy analysis of battery cells in multi-cell battery packs. Specifically, the cell impedances are determined while the pack continues to operate, such as being charged or discharged. For example, the pack voltage/power output remains unchanged while this analysis is initiated, performed, and ended. Cell impedance is determined based on the cell's response to the signal applied to the cell. For example, a current through the cell is charged while monitoring cells' voltage response. Although the power output of the changes during this testing, but the operation of the pack is not impacted due to the power compensation provided by one or more other cells in the pack thereby ensuring uninterrupted operation of the pack. This in situ testing is provided by the unique architecture of the pack, comprising multiple nodes and individual node controllers.

Abstract: A method for thermal management performed by a controller of an energy storage system, where the energy storage system includes at least a first battery module, a second battery module, a first battery management system (BMS) node, and a second BMS node. The first BMS node is configured to control operation of the first battery module, and the second BMS node is configured to control operation of the second battery module. The method includes (a) determining a first temperature profile difference representing a difference between an actual temperature profile of the first battery module and a desired temperature profile of the first battery module, (b) determining a first operation adjustment representing a desired change in operation of the first battery module for decreasing the first temperature profile difference, and (c) controlling the first BMS node to change operation of the first battery module according to the first operation adjustment.

Abstract: A method for adaptive electrochemical cell management in an energy storage system including a plurality of battery management system (BMS) nodes, the method including (1) obtaining a first signal identifying one or more degradation mechanisms of a first cell assembly of a first BMS node of the plurality of BMS nodes, the first cell assembly including one or more first electrochemical cells, and (2) controlling a first BMS node controller of the first BMS node in response to the first signal, to change a state of operation of the first cell assembly to mitigate the one or more degradation mechanisms of the first cell assembly, independently of operation of a second BMS node of the plurality of BMS nodes.

Abstract: Described herein are methods and systems for updating SOC estimates of individual cells in battery packs. Specifically, SOC estimates are updated in-situ, e.g., while the battery packs remain operational. For example, a cell is charged or discharged, independently from other cells, until the cell OCV is at a set value, corresponding to one of target zones. The target zones have more prominent correlations between the OCV and SOC than other parts of the OCV profile. A new SOC value, corresponding to the cell OCV, is used to update the SOC estimate. In some examples, a set of voltages is obtained while the cell is charged or discharged at a constant current/power, e.g., outside of the target zones. One or more differential capacities are determined from this voltage set, and a new SOC value is obtained based on these differential capacities.

Abstract: Described methods and systems provide in-situ leakage current testing of battery cells in battery packs even while these packs operate. Specifically, an external electrical current is discontinued through a tested battery cell using a node controller, to which the tested battery cell is independently connected. Changes in the open circuit voltage (OCV) are then detected by the node controller for a set period time. Any voltage change, associated with taking the tested cell offline, is compensated by one or more other cells in the battery pack. The overall pack current and voltage remains substantially unchanged (based on the application demands), while the in-situ leakage current testing is initiated, performed, and/or completed. The OCV changes are then used to determine the leakage current of the tested cell and, in some examples, to determine the state of health of this cell and/or adjust the operating parameters of this cell.

Abstract: A method for managing a plurality of stacks of electrochemical cells, where the plurality of stacks are electrically coupled in parallel in a battery. The method includes (a) operating the plurality of stacks to execute a global operating strategy, (b) controlling one or more first power converters to change operation of one or more first stacks of the plurality of stacks to execute a first local operating strategy of operating the one or more first stacks at one of a constant power and a constant current, and (c) controlling one or more second power converters to change operation of one or more second stacks of the plurality of stacks to compensate for change in operation of the one or more first stacks caused by executing the first local operating strategy, and thereby maintain the global operating strategy of the battery while executing the first local operating strategy.

Abstract: A method for adaptive electrochemical cell management in an energy storage system including a plurality of battery management system (BMS) nodes, the method including (1) obtaining a first signal identifying one or more degradation mechanisms of a first cell assembly of a first BMS node of the plurality of BMS nodes, the first cell assembly including one or more first electrochemical cells, and (2) controlling a first BMS node controller of the first BMS node in response to the first signal, to change a state of operation of the first cell assembly to mitigate the one or more degradation mechanisms of the first cell assembly, independently of operation of a second BMS node of the plurality of BMS nodes.

Abstract: A method for managing a plurality of stacks of electrochemical cells, where the plurality of stacks are electrically coupled in parallel in a battery. The method includes (a) operating the plurality of stacks to execute a global operating strategy, (b) controlling one or more first power converters to change operation of one or more first stacks of the plurality of stacks to execute a first local operating strategy of operating the one or more first stacks at one of a constant power and a constant current, and (c) controlling one or more second power converters to change operation of one or more second stacks of the plurality of stacks to compensate for change in operation of the one or more first stacks caused by executing the first local operating strategy, and thereby maintain the global operating strategy of the battery while executing the first local operating strategy.

Abstract: A method for adaptive electrochemical cell management in an energy storage system including a plurality of battery management system (BMS) nodes, the method including (1) obtaining a first signal identifying one or more degradation mechanisms of a first cell assembly of a first BMS node of the plurality of BMS nodes, the first cell assembly including one or more first electrochemical cells, and (2) controlling a first BMS node controller of the first BMS node in response to the first signal, to change a state of operation of the first cell assembly to mitigate the one or more degradation mechanisms of the first cell assembly, independently of operation of a second BMS node of the plurality of BMS nodes.

Abstract: Described herein are methods and systems for updating SOC estimates of individual cells in battery packs. Specifically, SOC estimates are updated in-situ, e.g., while the battery packs remain operational. For example, a cell is charged or discharged, independently from other cells, until the cell OCV is at a set value, corresponding to one of target zones. The target zones have more prominent correlations between the OCV and SOC than other parts of the OCV profile. A new SOC value, corresponding to the cell OCV, is used to update the SOC estimate. In some examples, a set of voltages is obtained while the cell is charged or discharged at a constant current/power, e.g., outside of the target zones. One or more differential capacities are determined from this voltage set, and a new SOC value is obtained based on these differential capacities.

Abstract: Described methods and systems are used for in-situ impedance spectroscopy analysis of battery cells in multi-cell battery packs. Specifically, the cell impedances are determined while the pack continues to operate, such as being charged or discharged. For example, the pack voltage/power output remains unchanged while this analysis is initiated, performed, and ended. Cell impedance is determined based on the cell's response to the signal applied to the cell. For example, a current through the cell is charged while monitoring cells' voltage response. Although the power output of the changes during this testing, but the operation of the pack is not impacted due to the power compensation provided by one or more other cells in the pack thereby ensuring uninterrupted operation of the pack. This in situ testing is provided by the unique architecture of the pack, comprising multiple nodes and individual node controllers.

Abstract: Described methods and systems provide in-situ leakage current testing of battery cells in battery packs even while these packs operate. Specifically, an external electrical current is discontinued through a tested battery cell using a node controller, to which the tested battery cell is independently connected. Changes in the open circuit voltage (OCV) are then detected by the node controller for a set period time. Any voltage change, associated with taking the tested cell offline, is compensated by one or more other cells in the battery pack. The overall pack current and voltage remains substantially unchanged (based on the application demands), while the in-situ leakage current testing is initiated, performed, and/or completed. The OCV changes are then used to determine the leakage current of the tested cell and, in some examples, to determine the state of health of this cell and/or adjust the operating parameters of this cell.

Abstract: Described methods and systems provide in-situ leakage current testing of battery cells in battery packs even while these packs operate. Specifically, an external electrical current is discontinued through a tested battery cell using a node controller, to which the tested battery cell is independently connected. Changes in the open circuit voltage (OCV) are then detected by the node controller for a set period time. Any voltage change, associated with taking the tested cell offline, is compensated by one or more other cells in the battery pack. The overall pack current and voltage remains substantially unchanged (based on the application demands), while the in-situ leakage current testing is initiated, performed, and/or completed. The OCV changes are then used to determine the leakage current of the tested cell and, in some examples, to determine the state of health of this cell and/or adjust the operating parameters of this cell.

Abstract: Described methods and systems are used for in-situ impedance spectroscopy analysis of battery cells in multi-cell battery packs. Specifically, the cell impedances are determined while the pack continues to operate, such as being charged or discharged. For example, the pack voltage/power output remains unchanged while this analysis is initiated, performed, and ended. Cell impedance is determined based on the cell's response to the signal applied to the cell. For example, a current through the cell is charged while monitoring cells' voltage response. Although the power output of the changes during this testing, but the operation of the pack is not impacted due to the power compensation provided by one or more other cells in the pack thereby ensuring uninterrupted operation of the pack. This in situ testing is provided by the unique architecture of the pack, comprising multiple nodes and individual node controllers.

Abstract: Described herein are methods and systems for detecting variation in minor total-impedance contributors in sets of electrochemical cells. For example, a method comprises maintaining a substantially constant current through the set of electrochemical cells and obtaining multiple voltage readings of the cells while the substantially constant current is maintained. The method then proceeds with determining multiple differential capacity values from the multiple voltage readings, characterizing one or more peaks in the multiple differential capacity values, and determining the variation in the minor total-impedance contributor based on one or more peaks. More specifically, partial capacitance values can be assigned to different impedance channels based on these peaks or, more specifically, based on the separation of adjacent peaks.