Battery health and control

Abstract

A system is disclosed for determining a measure of degradation of a battery unit comprising a plurality of battery cells and configured to be used as a power supply for a power consumer of a marine vessel. The system is configured to obtain state of health data and battery cell data. The state of health data relates to the state of health of a battery cell as determined by a battery management system and the battery cell data relates to a property of the battery cell. The system is configured to determine, based on the state of health data and the battery cell parameter data, a measure of degradation of the battery unit.

Description

[0001] BATTERY HEALTH AND CONTROL

[0002] The present disclosure relates to determining the health of batteries used in marine vessels and to controlling the batteries to deliver power in an optimised way.

[0003] BACKGROUND

[0004] Batteries may be used as an alternative (to internal combustion) power source for components of a marine vessel however various factors including age can affect their electrothermal behaviour, and therefore their performance over time.

[0005] SUMMARY OF THE INVENTION

[0006] The present disclosure relates to determining a measure of degradation of a cell in a battery unit and to the subsequent control of the battery unit such that its performance, operation and lifetime are optimised. Due to the nature of marine vessels and their components, battery units that provide power to marine vessel components may be used over long periods of time. The present disclosure is able to take into account and mitigate for the long-term operation of battery units, and their requirement for maintenance due to factors including the health of the battery unit (synonymously referred to as a “battery”), the control of the degradation of the battery unit, the long-term reliability of the battery unit, and safety and risk mitigation for the vessel using the battery unit to supply power to at least one component of the vessel. Real-time monitoring of the health of a battery system can allow a vessel (herein used synonymously with “ship”) operator to track the battery’s condition continuously. Examples herein relate to predictive maintenance strategies which can be used to minimise down time and ensure optimal battery performance based on real-time guidance and feedback from the battery itself.

[0007] A battery system to deliver power to a marine vessel component (e.g. of a power system) comprises a plurality of battery units, or “battery modules.” Each battery unit / module comprises a plurality of battery cells. A battery system comprises a plurality of battery modules connected in series to form “strings” which are connected together in parallel. In this disclosure, when monitoring etc. a cell of a battery unit is discussed it is meant a cell of a battery unit (or the battery unit as a whole) that is part of a battery string, e.g. part of a battery system to deliver power to a marine vessel component.

[0008] Some examples herein use an acquisition module, e.g. a high-speed acquisition module, to monitor for a condition, or to monitor a parameter of at least one cell in the battery unit, to determine a condition of a cell of the battery unit (which may be synonymous with a condition of the battery unit itself). Such an acquisition module may have both analog and digital input channels, but may additionally or alternatively comprise multiple synchronous channels connected via a high-speed internal bus. Such an acquisition module may comprise a current and / or a voltage sensor to sense the current and / or the voltage in at least one cell in a battery unit, or of the battery unit as a whole. Current and voltage data (“raw” data) from such sensors may be sent to a control system for storage, trending, and pre-processing as will be described herein. Such data is referred to herein as “battery cell data.”

[0009] In some examples, at least one battery cell may be randomly monitored. For example, at least one cell may be monitored in at least three battery units / modules in a battery string.

[0010] According to this disclosure, several battery parameters (or “health indicators”) may be monitored for, calculated, determined, and used to determine a measure of how much a cell in a battery unit, and / or the battery unit as a whole, has degraded, which can then be used as part of a control algorithm to control how the battery unit (and how a battery system) is used to supply power to marine vessel components.

[0011] Batteries degrade over time due to factors like cycling, temperature variations, and chemical reactions. By utilising examples of this disclosure a battery control scheme can be adjusted and dynamically operated by at least one of: dynamically adjusting the charging rates and depth of discharge of a battery unit cell or of a battery unit as a whole, controlling the temperature of a cell or of a battery unit as a whole to be within safe limits to prevent accelerated ageing, balancing at least one cell in a battery unit or of the battery unit as a whole (using comparisons of power-to-capacity ratio of each cell vs charging / discharging rate, by balancing the acceleration coefficient for each cell based on its voltage deviation during charging and discharging modes, and / or by arranging the bus setup (closed or open bus - for example if a bus section’s voltage exceeds an upper limit then the bus may be opened to prevent overcharging and vice-versa if the voltage drops too low to close the section to avoid excessive discharge), and by avoiding extreme operating conditions. Since battery cell degradations are often irreversible, examples of the disclosure that use the calculated measure of degradation to control the battery unit are able to minimize future battery unit degradation and are therefore able to maximize the remaining useful life of the battery.

[0012] According to this disclosure, several elements are taken in account to derive a “measure of degradation” or “combined state of health” or “total state of health” for at least one cell in a battery unit, or of the battery unit as a whole, which include: a parameter relating to the electrical health of a battery cell (for example a parameter indicating the voltage level or the voltage unbalance, since voltage distortions may provide insights into battery cell health) for example as determined by a high-speed input / output; a parameter relating to the air flow heat distribution external to the battery unit, e.g. the air flow heat distribution on a battery rack (monitoring air flow patterns may lead to optimized cooling and prevent overheating); a parameter obtained via a Rain-Flow counting method to analyze the battery power profile in real-time and to determine at least one of the number of charge / discharge cycles, the depth of discharge, and the number of half and full cycles; a parameter relating to a capacity loss, e.g. capacity loss data for example obtained from the manufacturer (e.g. annually); and a battery state of health (“SOH”) which may be obtained from a battery management system and may be verified by the battery supplier, e.g. annually, e.g. through site visits.

[0013] This disclosure therefore provides a measure of degradation that combines a state of health as determined by a “short-term estimator” (e.g. a measurement of voltage and / or current through a battery cell or a temperature variation as determined by a cooling system) with a “long-term estimator” (e.g. yearly capacity loss data from the manufacturer, Rain-flow counting method results and / or SOH feedback from a BMS), as mentioned above. Utilizing the information on battery degradation level, the control scheme for a battery may be autonomously adjusted to mitigate the degradation. This diversity of inputs and data on the basis of which the measure of degradation is determined increases the accuracy of the measure of degradation, and therefore the accuracy in the ability of a control scheme to prevent further degradation through improved and more efficient balancing. Further advantages include transparency in battery utilization thereby avoiding warranty claims, improved energy management enabling robust power systems with battery assistance, advanced battery health management, extended battery life, improved decision making, and improved operational efficiency.

[0014] According to an example of this disclosure there is provided a system for determining a measure of degradation of a battery unit comprising a plurality of battery cells and configured to be used as a power supply for a power consumer of a marine vessel, the system being configured to: obtain short-term state of health data relating to a short-term estimate of the health of a battery cell; obtain long-term state of health data relating to a long-term estimate of the health of a battery cell; and determine, based on the short-term and long-term state of health data, a measure of degradation of the battery unit.

[0015] As an example, and according to an example of this disclosure, there is provided a system for determining a measure of degradation of a battery unit comprising a plurality of battery cells and configured to be used as a power supply for a power consumer of a marine vessel, the system being configured to: obtain state of health data relating to the state of health of a battery cell as determined by a battery management system; obtain battery cell data relating to a property of the battery cell; and determine, based on the state of health data and the battery cell parameter data, a measure of degradation of the battery unit.

[0016] The property of the battery cell may comprise at least one of: voltage behaviour during charging the battery cell; voltage behaviour during discharging the battery cell; current behaviour during a constant voltage charging phase of the battery cell; and voltage behaviour upon cycling the battery cell. The property of the battery cell may comprise at least one of: the battery unit state of health upon charging; the constant current charging time; the constant voltage charge time; the ratio of the constant voltage charge time to the constant current charge time; the battery unit state of health upon discharging; the coulomb efficiency; the constant current discharge time; the constant voltage current profile; the integral of the voltage over the charge; the integral of the voltage over discharge; the open-circuit voltage; and the rate of voltage change over the charge.

[0017] The system may be configured to: obtain data relating to a battery power profile, wherein the measure of degradation of the battery unit is determined based on the data relating to the battery power profile.

[0018] The data relating to the battery power profile may comprise at least one of: a number of charge cycles of the cell; a number of discharge cycles of the cell; the depth of discharge of the cell; a number of half cycles of the cell; and a number of full cycles of the cell.

[0019] The data relating to the battery power profile may be determined using a Rain-Flow counting algorithm.

[0020] The system may be configured to: obtain air flow data relating to the air flow in a region exterior to the cell, wherein the measure of degradation of the battery unit is determined based on the air flow data.

[0021] The system may be configured to: obtain capacity data indicating a predicted yearly capacity loss of the cell, wherein the measure of degradation of the battery unit is determined based on the capacity data.

[0022] The battery cell data may be received from a high-speed input-output module connected to the battery unit.

[0023] The system may be configured to: obtain state of health data relating to the state of health of a plurality of battery cells as determined by a battery management system; obtain battery cell data relating to a property of the plurality of the battery cells; and determine, based on the state of health data and the battery cell parameter data, a measure of degradation of the battery unit.

[0024] The measure of degradation may comprise a weighted sum of first and second quantities, the first quantity being based on the state of health data, the second quantity being based on the battery cell data.

[0025] The system may be configured to: obtain data relating to an operational mode of the vessel, including at least one objective that the marine vessel is to achieve using the power consumer supplied by power from the battery unit; determine, based on the measure of degradation, a set of battery control parameters for controlling the battery unit in an operating mode in which the battery unit is controlled to supply power to the power consumer such that the marine vessel is able to achieve the objective and that degradation of the battery unit is minimised.

[0026] The system may be configured to determine the trade-off between the energy efficiency of the marine vessel and the safety of the marine vessel based on the marine vessel achieving the objective when the power consumer is powered by the battery unit, operating in the operating mode according to the battery control parameters.

[0027] Determining the trade-off may comprise: obtaining an energy efficiency index indicating a predicted energy efficiency for the marine vessel achieving the objective when the power consumer is powered by the battery unit, operating in the operating mode according to the battery control parameters; obtaining a safety index indicating a predicted safety level for the marine vessel achieving the objective when the power consumer is powered by the battery unit, operating in the operating mode according to the battery control parameters; and determining a combined index based on the energy efficiency index and the safety index.

[0028] If the combined index exceeds a predetermined threshold, the system may be configured to determine a new set of battery control parameters.

[0029] The battery control parameters may be to control at least one of: the charging rate of a cell in the battery unit; the depth of discharge of a cell in the battery unit; the battery temperature; and balancing cells of the battery unit.

[0030] The battery control parameters may be to control at least one of: the power-to-capacity ratio of a cell; the charge rate of a cell; the discharge rate of a cell; the acceleration coefficient of a cell; the voltage deviation of a cell during charging; the voltage deviation of a cell during discharging; and a property of a bus connected to the battery unit.

[0031] According to another example of this disclosure there is provided a system for determining an operating mode of a battery unit configured to supply power to a power consumer of a marine vessel, the system being configured to: obtain data relating to an operational mode of the vessel, including at least one objective that the marine vessel is to achieve using the power consumer supplied by power from the battery unit; obtain data relating to a measure of degradation of the battery unit; determine, based on the measure of degradation, a set of battery control parameters for controlling the battery unit in an operating mode in which the battery unit is controlled to supply power to the power consumer such that the marine vessel is able to achieve the objective and that degradation of the battery unit is minimised.

[0032] The system may be configured to determine the trade-off between the energy efficiency of the marine vessel and the safety of the marine vessel based on the marine vessel achieving the objective when the power consumer is powered by the battery unit, operating in the operating mode according to the battery control parameters. Determining the trade-off may comprise: obtaining an energy efficiency index indicating a predicted energy efficiency for the marine vessel achieving the objective when the power consumer is powered by the battery unit, operating in the operating mode according to the battery control parameters; obtaining a safety index indicating a predicted safety level for the marine vessel achieving the objective when the power consumer is powered by the battery unit, operating in the operating mode according to the battery control parameters; and determining a combined index based on the energy efficiency index and the safety index.

[0033] If the combined index exceeds a predetermined threshold, the system may be configured to determine a new set of battery control parameters.

[0034] The battery control parameters may be to control at least one of: the charging rate of a cell in the battery unit; the depth of discharge of a cell in the battery unit; the battery temperature; and balancing cells of the battery unit.

[0035] The battery control parameters may be to control at least one of: the power-to-capacity ratio of a cell; the charge rate of a cell; the discharge rate of a cell; the acceleration coefficient of a cell; the voltage deviation of a cell during charging; the voltage deviation of a cell during discharging; and a property of a bus connected to the battery unit.

[0036] The measure of degradation of the battery unit may be determined based on state of health data relating to the state of health of a battery cell as determined by a battery management system and battery cell data relating to a property of the battery cell.

[0037] The property of the battery cell may comprise at least one of: voltage behaviour during charging the battery cell; voltage behaviour during discharging the battery cell; current behaviour during a constant voltage charging phase of the battery cell; and voltage behaviour upon cycling the battery cell.

[0038] The property of the battery cell may comprise at least one of: the battery unit state of health upon charging; the constant current charging time; the constant voltage charge time; the ratio of the constant voltage charge time to the constant current charge time; the battery unit state of health upon discharging; the coulomb efficiency; the constant current discharge time; the constant voltage current profile; the integral of the voltage over the charge; the integral of the voltage over discharge; the open-circuit voltage; and the rate of voltage change over the charge.

[0039] The measure of degradation of the battery unit may be based on data relating to a battery power profile.

[0040] The data relating to the battery power profile may comprise at least one of: a number of charge cycles of the cell; a number of discharge cycles of the cell; the depth of discharge of the cell; a number of half cycles of the cell; and a number of full cycles of the cell.

[0041] The data relating to the battery power profile may be determined using a Rain-Flow counting algorithm. The measure of degradation of the battery unit may be based on air flow data relating to the air flow in a region exterior to the cell.

[0042] The measure of degradation of the battery unit may be based on capacity data indicating a predicted yearly capacity loss of the cell.

[0043] The measure of degradation of the battery unit may be based on state of health data relating to the state of health of a plurality of battery cells as determined by a battery management system and battery cell data relating to a property of the plurality of the battery cells.

[0044] The measure of degradation may comprise a weighted sum of first and second quantities, the first quantity being based on the state of health data, the second quantity being based on the battery cell data.

[0045] The system may be configured to determine the measure of degradation of the battery unit.

[0046] BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Examples of the present disclosure will be described in detail with reference to the accompanying drawings, which should not be construed as limiting, in which:

[0048] Figure 1 shows a schematic diagram of a system;

[0049] Figure 2 shows a schematic diagram of a system;

[0050] Figure 3 shows a flowchart of a process;

[0051] Figure 4 shows a flowchart of a process; and

[0052] Figure 5 shows a schematic diagram of a system;

[0053] DETAILED DESCRIPTION

[0054] These drawings should not be considered limiting, rather they are used for understanding and explaining the present disclosure.

[0055] Figure 1 shows a battery unit 102 comprising a plurality of battery cells. The battery unit 102 may also be referred to as a battery module. The cells are connected together and each convert chemical energy into electrical energy so that the battery unit 102 is configured to supply electrical energy. In this way, the battery unit 102 is configured to be used as a power supply. The battery unit 102 is configured to be used to supply power to a (not shown) marine vessel component. More specifically, a marine vessel comprises a number of power consumers, being those components of the marine vessel configured to draw power (e.g. electrical energy) to operate, such that a part of the marine vessel is to perform a task so that the marine vessel achieves an objective. A propulsor, or propulsion device, such as a thruster, a propeller, or a rudder are examples of power consumers. These components may be under the control of a control system (e.g. a dynamic positioning control system) which may control supply of electricity from a power supply. The power consumer / component may comprise at least one of a propulsor, e.g. a propulsion component, a mission load, a hotel load, and an auxiliary load. A “mission load” may comprise a consumer that is configured to perform a task relating to the vessel, such as a crane, a winch, a remotely operated vehicle, or a drill. The mission load may comprise these components themselves or a controller configured to control the operation of these components. Using power from a battery unit 102 (rather than for example using internal combustion) has the advantage of lower emissions, lower fuel consumption, and reduced engine maintenance.

[0056] As stated above, the battery unit 102 may be part of a battery power system, the battery power system comprising at least one (and in some examples a plurality of) battery strings, where each string comprises a plurality of battery units 102. The strings may comprise battery units connected in series and the strings may be connected in parallel in some examples. Each battery unit may comprise a plurality of cells. To operate the battery power system to supply power to the marine vessel, individual parameters of each battery unit, and / or of each string, may be controlled. During the marine vessel’s operation they may be adjusted. According to the present disclosure, control is afforded over the battery power system such that the degradation of individual battery units may be minimised and the useful life of the individual battery units may be maximised. A battery unit determined to have undergone more degradation that was predicted may therefore be managed to be operated less than another battery unit having less degradation, and / or another battery string may be relied on to supply more power to meet a power demand etc. or such a battery unit or string may not be used at all to power the vessel. By measuring the degradation of the battery unit, a measure of degradation of the battery string of which the battery unit is a part and of the battery power system as a whole may be obtained. A battery unit may also be referred to as a stack.

[0057] As stated above, over time, a battery unit 102 will degrade, for example due to use, chemical reactions, and temperature variations (both internal to and external to the battery unit) which will lower the battery unit’s ability to store and deliver energy, in the sense of the amount of energy the battery unit can store and the amount of energy the battery unit can deliver. According to this disclosure, a controller 100 is configured to determine a measure of degradation of at least one cell in the battery unit 102, and therefore a measure of degradation of the battery unit 102 as a whole. By measure of degradation, it may therefore be meant a measure of a decline of the cell’s ability, and therefore the battery unit’s ability, to store and / or deliver energy. The measure of degradation may comprise a metric of degradation. The measure of degradation may be a number. The measure of degradation may also be termed a “state of health” and may comprise an indication of the remaining useful life of the battery unit. The controller 100 is configured to obtain state of health data relating to the state of health of a battery cell as determined by a battery management system 104. A battery management system 104 is a module configured to monitor the performance of at least one cell in the battery unit 102, for example to monitor at least one parameter of the cell, for example the cell temperature and / or the ambient air and / or the air flow around the cell, to obtain a measure of the “state of health” (“SOH”) of the cell and therefore the battery unit. The battery management system (“BMS”) 104 may be configured to monitor at least one of: the voltage (e.g. the total voltage of the battery unit and / or the voltage of individual cells), the temperature (e.g. the average temperature of individual cells and / or the battery unit, and / or the actual temperature of individual cells and / or the battery unit), the current, individual cell health, the temperature of individual cells and / or of the battery unit, a parameter relating to the cooling of a cell and / or of the battery unit (e.g. cooling rate), and / or the state of balance of one or more cells, and to determine a measure of the health (or a SOH) of at least one cell in the battery unit, and / or of the battery unit itself, based on at least one of these parameters.

[0058] The BMS 104 may be installed onboard the vessel. The battery unit 102 may comprise the BMs 104 in some examples. The vessel may therefore comprise the BMS 104. The state of health data may comprise an indication of the remaining useful life of the battery unit which may be predicted and / or estimated. The state of health data may therefore be historic data and therefore may comprise a historic parameter, e.g. a parameter obtained in the past and therefore one not obtained in real time or near real time. Such a parameter may indicate by how much the battery was predicted to degrade over a period. In other words, the state of health data may comprise a predicted and / or estimated measure of how much the battery unit was predicted to degrade, or a predicted and / or estimated degradation amount, over a period. The state of health data, being a predicted quantity, may be based on predicted use data. As such, the state of health data may be based on predicted use data over a period of time. The use data may be provided by a user (e.g. the number of voyages the vessel comprising the battery power system is predicted to take etc.). The state of health data may be obtained on an annual basis. The state of health data may comprise a quality indicator since the remaining useful life of the battery unit may be considered synonymous with the quality of the battery unit. In this way the state of health is itself a measure of degradation of a cell or of the battery unit. The state of health data may be based on at least one the state of charge, a chemical reaction, a charging and / or discharging cycle, temperature variations, and any cell imbalances of at least one cell of the battery unit or the battery unit itself. The state of health may be computed as a ratio of the maximum battery charge to its capacity, but it may be computed some other way. The state of health data may be adjusted by the battery unit manufacturer, e.g. on an annual basis. The controller 100 is also configured to obtain battery cell data, the battery cell data relates to a property of the battery cell, or battery data relating to a property of the battery unit (the two shall be considered synonymous throughout this document). In Figure 1 the battery cell data is obtained from a high-speed input-output device 106. However, any other module may be used to obtain the battery cell data. According to this disclosure, the controller 100 is configured to determine the measure of degradation of the battery unit based on the state of health data and the battery cell parameter data. The battery parameter data may be considered real-time data or near-real-time data.

[0059] The dotted lines in Figure 1 illustrate connections between components and may be wired connections.

[0060] The SOH may be considered a “long term estimator” or “long term health indicator” meaning that the controller 100 is configured to obtain, from the BMS, a parameter indicating a long-term property of at least one cell and / or the battery unit. In contrast, the component 106, being configured to obtain real-time or near-real-time data, is configured to monitor a “short term estimator” or “short term health indicator,” a parameter indicating a short-term property of at least one cell and / or the battery unit. Therefore, in one example, the controller 100 is configured to obtain a short term estimator and a long term estimator and to determine a measure of degradation of at least one cell in the battery unit 102 and / or of the battery unit as a whole, based on the short term estimate and the long term estimator.

[0061] The battery cell data may comprise any one or more of the battery cell and / or unit internal temperature (including temperature variations), the voltage of at least one cell and / or of the battery unit as a whole, the current through at least one cell and / or through the battery unit as a whole, and a voltage unbalance and / or distortion in at least one cell and / or through the battery unit as a whole. In other words, short-term estimators are real time or near-real time parameters obtained, e.g. measured, directly from the battery unit 102. In this way, the module 106 may comprise a high-speed acquisition module to monitor at least one cell in the battery unit, or the battery unit as a whole, in real time or near real-time. T o monitor the battery unit 102, the module 106 may comprise an analogue channel input and a digital channel input and may be connected to the battery unit 102 via a high-speed data bus. The module 106 may comprise, or may be used in conjunction with, one or more sensors (e.g. a voltage sensor and a current sensor). In this way, the module 106 is configured to obtain raw battery cell data from the battery unit 102.

[0062] Long-term estimators may comprise any one or more of data concerning a predicted capacity loss (e.g. a predicted yearly capacity loss), data on a cell and / or battery unit cycle (e.g. as determined using a Rain Flow counting algorithm), and a SOH of a cell and / or of the battery unit as determined by a BMS 104 (as discussed above). Therefore, the receipt of SOH data from the BMS 104 should be considered as an example only. Indeed, 106 could alternately be considered a “short-term parameter” module to obtain short-term parameter data (such as the battery cell data mentioned above) and the module 104 could be considered a “long-term parameter” module to obtain long-term parameter data (such as SOH data from a BMS, capacity loss data, and / or battery cycle data etc.

[0063] In this way, the present disclosure provides a more accurate estimation of battery degradation since it uses at least one long-term estimator (state of health data from the BMS 104 in some examples) and at least one short-term estimator, which may be a current parameter received in real-time or near-real time. Put another way, rather than solely relying on a manufacturer’s estimate which may not be current and due for an update, the present disclosure seeks to supplement such an estimate with a current parameter of at least one cell in the battery unit. In this way, a more accurate and up to date estimation of the measure of how much the battery unit has degraded may be achieved. As will be expanded upon below, in some examples additional short-term and long-term parameters may be used in the calculation. By long-term estimate it may mean a quantity that has been sampled at a time that is in the past relative to the short-term estimate. Therefore, the long-term estimate constitutes a parameter obtained prior to or before the short-term estimate. In other words the short-term estimate may be obtained more recently than the long-term estimate. In some examples the short-term estimate may constitute a parameter sampled at a higher frequency than the long-term estimate. The short-term estimate may constitute a parameter measured at a high frequency. In this way the short-term parameter (e.g. the battery unit data) can be used to supplement the long-term parameter (e.g. the SOH prediction or estimate) to improve a measure of the degradation of the battery unit. For example, the SOH prediction may comprise a battery unit operational profile and the battery unit data may comprise a real time or near-real time measured electrical parameter. Together, they may allow an accurate parameter such as how often the battery unit discharges, its chemical and / or electrothermal properties. In this way, a more accurate measure of the battery unit degradation is obtained. By way of another example, the state of health data may comprise a curve relating to the battery unit, and by using a real time measurement may allow whether there have been any spikes that indicate something is wrong with the battery unit to be determined (e.g. if during a certain operation there is a voltage dip).

[0064] To illustrate the operation of the controller 100 reference is now made to Figure 2.

[0065] For the avoidance of doubt, “obtaining” data as used herein may comprise receiving data (e.g. from a sensor or from another component), measuring data (e.g. by a sensor or other measuring device), determining or calculating or estimating data (e.g. from data received from a sensor), or retrieving data (e.g. from an internal or external memory storing data), depending on the example. Therefore, for the avoidance of doubt, the state of health data and / or the battery cell data may be directly determined (e.g. by a sensor), received (e.g. from a BMS module and a high-speed input-output module) or may be stored in a memory and may be retrieved etc. Battery unit data may be retrieved in an identical way. Alternatively, battery cell data may be retrieved and the battery unit data may be based on the battery cell data (e.g. measurements may be made at the “cell-level” which can be used to obtain properties of the battery unit).

[0066] Figure 2 shows an example process 200. The controller 100 of Figure 1 may be configured to perform all or part of the process 200 to determine the metric of degradation for the battery unit 102.

[0067] At S202 the process 200 comprises obtaining battery state of health data, for example from the BMS 104. At S204 the process 200 comprises obtaining battery cell data, for example from the module 106. At S206 the process 200 comprises determining a measure of degradation of at least one cell in the battery unit, or of the battery unit as a whole.

[0068] The process 200 may comprise a number of optional steps which the controller 100 is configured to perform, as indicated by the dotted boxes in the flowchart. For instance, as indicated at S208 the measure of degradation may be determined based on additional parameters, e.g. those not received from the module 106, these may be long-term estimators as described above. Further, in one example the measure of degradation of the battery may be used (at S212) to determine a set of parameters for controlling the battery unit (e.g. controlling the battery unit to supply power to the power consumer of the marine vessel according to a set of parameters), based on data (S210) describing an objective that the marine vessel is to achieve. This will be expanded upon with reference to Figures 3 and 4.

[0069] As stated above, the state of health data, obtained at S202, may be an indication of the state of health of a cell or of the battery unit, or a measure of degradation of a cell or of the battery unit, obtained from a first source (e.g. the BMS 104). The battery cell data, obtained at S204, may similarly be an indication of the state of health of a cell or of the battery unit, or a measure of degradation of a cell or of the battery unit, e.g. obtained from a second source (the module 106, e.g. directly from the battery unit 102). As such, the state of health data obtained at S202 may be considered “first state of health data” or a “first measure of degradation” and similarly, the battery cell data obtained at S204 may be considered “second state of health data” or a “second measure of degradation.” Therefore, the measure of degradation determined at S206 may be considered a total, or a combined, state of health or measure of degradation, based on the first and second states of health, or first and second measures of degradation. As will be explained below, such a combined measure of degradation may be a weighted sum.

[0070] Any state of health, or measure of degradation, as used herein may be expressed numerically, e.g. as a percentage, such as a percentage degradation value or percentage of maximum battery capacity. As described above, the property of the battery described by the battery cell data may be relating to the voltage of at least one cell or of the battery unit as a whole and / or the current through at least one cell or of the battery unit as a whole. For example, the battery cell data may comprise data relating to at least one of: voltage behaviour during charging the battery cell; voltage behaviour during discharging the battery cell; current behaviour during a constant voltage charging phase of the battery cell; and voltage behaviour upon cycling the battery cell. These may be obtained directly or may be calculated from voltage and / or current data (e.g. received from the module 106).

[0071] For example, the controller 100 may obtain at least one battery behaviour curve. For example, the controller 100 may determine such a curve from data received, e.g. from the HSIO 106, or it may receive the curve, e.g. from the HSIO. In any case, the controller 100 may analyse the curve to determine the battery cell data.

[0072] The battery behaviour curve obtained by the controller 100 may be the voltage-time behaviour of at least one cell (or of the battery unit) upon charging. In these examples, the controller 100 may determine one or more of the following properties of the battery cell or of the battery unit from this curve: the SOH of the cell or the battery unit upon charging, the constant current charging time (“CCCT”) of the cell or the battery unit, the constant voltage charge time (“CVCT”) of a cell or the battery unit, and the ratio of the CVCT to the CCCT for a cell or for the battery unit. The SOH may be considered as the ratio of the remaining useful capacity of the cell or the battery unit over a nominal capacity of the cell or the battery unit. The CCCT may be considered as the time needed by the cell or the battery unit to reach its constant-voltage phase upon charging. The CVCT may be considered as the time spent by the cell or the battery unit in a constant-voltage phase upon charging.

[0073] Alternatively, or additionally, the battery behaviour curve may be the voltage-time behaviour of at least one cell or the battery unit upon discharging. In these examples, the controller 100 may determine one or more of the following properties of the battery cell or of the battery unit from this curve: the SOH of a cell or the battery unit upon discharging, the Couloumb efficiency (“CE”) of a cell or the battery unit, and the constant current discharge time (“CCDT”) of a cell or the battery unit. As above, the SOH may be considered as the ratio of the remaining useful capacity of the cell or the battery unit over a nominal capacity of the cell or the battery unit. The CE may be considered as the ratio of the charged capacity over the discharged capacity of a cell or the battery unit (e.g. a ratio of the charge inserted during battery charging, “CCHAR,” and the charge extracted during battery discharging, “CDIS.”) The CCDT may be considered the time spent by the cell or battery unit in the constant current phase upon discharging, or the time taken during discharge to reach the lower cut-off voltage The SOH may be derived based on an integral of current over time, multiplied by the inverse factor of the rated capacity of the battery cell. Given that the electrothermal behaviour of a battery cell can result in noticeable changes in the voltage-time curve for a battery cell, which represents how the voltage changes overtime during successive charge and discharge cycles and which expresses the relationship between voltage and the time during battery cycling, this curve can be analysed to determine any of the quantities mentioned above. From this curve, the upper and lower voltage limits of a cell may also be determined as well as the cycle time (a shorter discharge time compared to charge-time may indicate low coulombic efficiency so CE may also be determined).

[0074] Battery cell aging may also influence the voltage relaxation profile (VRP) which may be determined by the process to obtain the battery cell data, e.g. during the relaxation time after charging, since aged battery cells require more time to reach a relaxed voltage, which is lower compared to a fresh battery cell. The open circuit voltage (OCV) curve may also be affected by aging, leading to steeper curves and higher voltages. Hence, a VRP and / or the OCV may be analyzed to determine any of the quantities mentioned above.

[0075] Alternatively, or additionally, the battery behaviour curve may be the current-time behaviour of at least one cell (or the battery unit) during a constant-voltage charging phase. In these examples, the controller 100 may determine, from this curve, the constant voltage (“CV”) current profile of a cell or the battery unit. The constant voltage current profile (“CVCP”) may be determined based on the CV phase upon charging. In the CV phase, the current decreases exponentially.

[0076] Alternatively, or additionally, the battery behaviour curve may be the voltage-charge behaviour of at least one cell (or the battery unit) upon cycling. This behaviour may comprise a VRP. In these examples, the controller 100 may determine one or more of the following properties of the battery cell or of the battery unit from this curve: the integral of the voltage over the charge (“Area VdQ” charging) of a cell or the battery unit, the integral of the voltage over the discharge (“Area VdQ” discharging) of a cell or the battery unit, the open-circuit voltage (“OCV”) of a cell or the battery unit, and the rate of voltage change over the charge at different Amp-hours (the “OCV slope”).

[0077] Obtaining the battery cell data may comprise extracting a relaxed voltage and / or a voltage slope may be extracted from the VRP, which is the voltage trend during the waiting / idling period at the end of charging. The relaxed voltage, measured after the waiting period at the end of charging and the VRP slope, may represent the voltage trend between the two different time instants in the waiting period, and may be determined from a VRP.

[0078] The process may comprise determining the battery cell voltage at different SoC levels during charging and discharging cycles, e.g. from an OCV curve, which may be determined for charging and discharging, and based on these curves, an average line may be determined which may then be used to find the slopes of voltages. As mentioned above, the battery cell data may comprise a voltage and / or current measurement (e.g. obtained from the module 106) and these may be used to calculate a further parameter, which may be any one or more of the parameters mentioned above derived from the above-mentioned curves.

[0079] In one example the controller 100 is configured to obtain a voltage and current measurement for each cell (e.g. from 106) and store these in a buffer. The controller 100 may be comprise one buffer per measurement, each buffer storing the measurement. The controller 100 may be configured to control the storing in said buffer based on the state of the battery, e.g. whether the battery is charging, discharging, or idling. In one example the size of the buffers is based on the battery state and may be automatically adjusted based on the battery state.

[0080] In one example the controller 100 is configured to store at least one of: the voltage for at least one cell at intervals (e.g. regular periodic intervals) during a charging period for that cell, the voltage for at least one cell at intervals (e.g. regular periodic intervals) during a discharging period for that cell, the voltage for at least one cell at intervals (e.g. regular periodic intervals) during an idling period for that cell, the current for at least one cell at intervals (e.g. regular periodic intervals) during a charging period for that cell, the current for at least one cell at intervals (e.g. regular periodic intervals) during a discharging period for that cell, and the current during charging for at least one cell at intervals (e.g. regular periodic intervals) during idling for that cell. As stated above, each one of these quantities may be stored in a buffer.

[0081] By way of example, upon completion of one cycle for charging, discharging and idling, the controller 100 may be configured to use the values from the buffers (voltage during charging, discharging, and idling, and current during charging, discharging, and idling) to calculate the indicators as mentioned previously per cell, namely, SOH upon charging, SOH upon discharging, CCCT, CVCT, CVCT / CCCT, CCDT, CCHAR, CDIS, CE, Area VdQ charging, Area VdQ discharging, relaxation voltage, OCV, CV current profile, OCV slope, and CVCP. The controller may be configured to store these computed values in a separate buffer group per cell.

[0082] In one example the average and / or median of the abovementioned parameters are computed every 24 hours. The average and / or median of these indicators per cell may be compared with that of other cells and the cell with the greatest deviation from the baseline may be determined and this information is used to determine the measure of degradation of the cell or of the battery unit. In some examples, it is determined whether the average and / or median of each cell is above a predetermined threshold and, if so, this may constitute an indication of the degradation of the cell and / or the battery unit. Therefore, some examples determine the measure of degradation based on a deviation per cell from a predetermined threshold.

[0083] Alternatively, or additionally, the measure of degradation may be determined based on other data (S208).

[0084] For instance, the measure of degradation may also be determined based on a battery power profile, being a power profile of at least one cell. The battery power profile may be received by a component connected to the battery. The battery power profile may be determined using a Rain-Flow algorithm. The battery power profile may comprise at least one of: a number of charge cycles of a cell or the battery unit, a number of discharge cycles of a cell or the battery unit, the depth of discharge of a cell or the battery unit, a number of half cycles of a cell or the battery unit; and a number of full cycles of a cell or the battery unit. A Rain-Flow algorithm may comprise result in a smoothed curve with fewer points than the original. A Rain-Flow algorithm may comprise identifying cycles from local extrema in a battery state of charge profile. Specifically, a state of charge curve may be divided into consecutive ranges and if the absolute value of the difference between the range’s endpoints is less than or equal to the same for two adjacent ranges then the endpoints of the middle range are discarded and this part of the curve is approximated by connecting the lower point of the first range with the upper point of the last range, thereby eliminating the middle points. If not then this is repeated starting from the next range in the sequence. The period over which data is computed and the number of cycles is user-definable and adjustable.

[0085] Alternatively or additionally the measure of degradation may be determined based on (S208) a depth of discharge, which may be based on the ratio between the capacity discharged from a fully charged battery and its nominal capacity, and which may indicate the percentage of the battery that has been discharged relative to the overall capacity of the battery. A damage equivalent quantity (“DEQ”) may be determined from a state of charge to number of cycles curve, which may provide an indication of damage caused to the battery life and the measure of degradation may be determined based on the DEQ in some examples.

[0086] Alternatively or additionally the measure of degradation may be determined based on (S208) air flow data relating to the air flow in a region exterior to a cell or to the battery unit. The air flow data may be received from a thermal management system. Rising temperatures can effect both the charging and discharging processes in batteries. An uncontrolled heat generation can lead to safety issues and operational failure, as well a significant reduction in the battery operational expected lifetime. The battery manufacturer may provide a thermal management system which performs heat removal, promoting temperature uniformity between battery strings and which prevents any spot cooling on a single location. Air flow data may comprise temperature and air flow distribution measurements.

[0087] To determine the air flow data, in some examples the temperature of the battery unit at the top of the unit may be obtained and the temperature of the battery unit at the bottom may be obtained. A temperature gradient may then be obtained based on the two temperatures to determine whether the battery unit is being cooled uniformly and / or effectively. If this is not the case the controller may be configured to control airflow around the battery unit or it may determine that the cooling unit for the battery power system is broken. If it is determined that a battery unit is not being cooled effectively then, to control the battery power system, battery units may be used that are not next to, near, proximate to, or in the vicinity of the battery unit not being cooled effectively. In this way battery units (and battery strings) that are being cooled properly may be prioritized over those that aren’t in the use of the battery system.

[0088] In one example the external battery unit temperature and air flow distribution measurements may be received by the controller 100 from a cooling system (see 506 in Figure 5). As for the above measurements, the controller 100 may store these temperature measurements in a buffer, for example updated every predetermined time period, e.g. an hour.

[0089] The controller 100 may determine the maximum absolute temperature and the temperature rises, e . g . the maximum minus the minimum temperature. The computed maximum and temperature rise may then be stored in a separate buffer. The buffer may store one value per hour and after 24 hours the average and median may be calculated. The computed value may then be used by the controller to determine the capacity degradation using the battery manufacturer information on FEC (Full Equivalent Cycle) vs temperature. The capacity loss varies depending on the C-rate during the charging or discharging cycle.

[0090] Alternatively, or additionally, the measure of degradation may be determined based on (see S208) capacity data relating to a predicted yearly capacity loss of the cell. This may be computed annually based on the average SOC of at least one cell in the battery unit, and may be computed by the manufacturer and transmitted to the controller, which may therefore receive and / or store the capacity data.

[0091] Alternatively, or additionally, the measure of degradation may be based on (S208) a measure of degradation as determined by a machine learning model. In these examples, a machine learning model may be trained on historical battery cell parameter data of at least one battery cell to output a measure of degradation of a cell, receiving current battery cell data as input. In other examples the machine learning model may be trained on historical battery cell parameter data of at least one battery cell to output any one of the parameters described above, for example a battery power profile, receiving current battery cell data as input.

[0092] The machine learning model may comprise a neural network. In some examples, a physics-based simulation model of a battery installed onboard the vessel that provides output based on the real time operation of at least one cell in the battery unit is compared to the output from the model and a difference between the two is determined. If there is a difference between the machine learning model output and the physics-based simulation model output and if this difference is greater than a predetermined threshold then the neural network model may be retrained accordingly. The battery simulation model may be vessel specific and may interface with an onboard control system as a FMU (Functional Mock up) module. The trained neural network may be any regression model or models which uses battery measurements as inputs and SOH as output.

[0093] As indicated by the looping arrows in Figure 2 the measure of degradation may be determined periodically. For instance, the process may comprise obtaining updated state of health data and / or updated battery cell data and determining an updated measure of degradation based on the updated state of health data and / or the updated battery cell data. Some examples of the process may comprise obtaining updated state of health data and / or updated battery cell data after a predetermined period of time has elapsed. In other examples, block S206 may be repeated so that the process comprises calculating the measure of degradation after a predetermined period of time has elapsed (whether or not the data at S202 and S204 is different) so that the measure of degradation is periodically updated.

[0094] Given that the property of the battery cell described by the battery cell data is related to the health of the battery cell, and therefore of the battery unit, the property may also be termed a “battery cell health indicator”, “a battery unit health indicator,” or, a “health indicator.” The battery cell data may also be termed “battery health indicator data” indicating a property of the battery cell that is related to its health.

[0095] S206 therefore comprises receiving at least the state of health data and battery cell data as inputs, and in some examples comprises receiving other data (S208). In any case, the measure of degradation may be computed as a weighted sum. As stated above, in these examples, the data described above may represent a measure, or estimate, of the battery cell or battery unit’s degradation due to that parameter (see the discussion on the “first state of health” or “first measure of degradation” above) and similarly for the battery cell data (see the discussion on the “second state of health” or “second measure of degradation” above). In other words, the state of health data, battery cell data or other data may each represent an estimate of the battery degradation. Hereafter these will be referred to as “degradation estimates” and in some examples the measure of degradation may be calculated as a weight of sum of these estimates. The process 200 may therefore comprise determining a state of health degradation estimate from the state of health data from the BMS (referred to as “DegradeBMs”) and determining a battery cell degradation estimate from the battery cell data (referred to as “DegradeBcp”). Therefore, in examples where the measure of degradation is determined based on the state of health data and the battery cell data only, the measure of degradation may be expressed as:

[0096] Mdegradation = WBMs*DegradeBMs + WBCp*DegradeBcp where WBMS is the weight of the state of health degradation estimate and WBCP is the weight of the battery cell data degradation estimate.

[0097] The function DegradeBcp may itself be based on any one or more of the above- mentioned quantities (e.g. the behavioural curves or the properties derived from those curves). So, for instance, Degradescp may be a function of any one or more of the SOH upon charging, CCCT, CVCT, CVCT / CCCT, SOH upon discharging, CE, CCDT, CV current profile, Area VdQ charging, Area VdQ discharging, OCV, OCV slope, CCHAR, CDIS, relaxation voltage, and CVCP. DegradeBcp may be expressed as a weighted sum of these quantities.

[0098] As the quantities used to determine the measure of degradation are themselves estimates of degradation the measure determined by the controller 100 at S206 may be considered to be a “combined measure of degradation” or a “weighted measure of degradation.”

[0099] As stated above, other data (S208) may be used to determine the measure of degradation. Therefore, the measure of degradation may be expressed as follows:

[0100] Mdegradation=WBMs*DegradeBMs + WBCp*DegradeBcp + Wother*Degradeother

[0101] Here, Degradeother is a degradation estimate from any one (or more) of the other data and Wother is the weight of that other data degradation estimate, or of those data degradation estimates, e.g. a state of health or measure of degradation due to a battery power profile, ambient temperature, predicted yearly capacity loss etc.

[0102] Therefore, in one example, the measure of degradation may be expressed as follows:

[0103] Mdegradation = WBMs*DegradeBMs + WBcp*DegradeBcp + WTemp*DegradeTemp

[0104] + WRainFlow*DegradeRainFlow + VVyearlyloss*Degradeyearlyloss

[0105] Here, DegradeTemp, DegradeRainFiow, and Degradeyeadyioss are respectively estimates of degradation due to the ambient temperature, a battery power profile (as determined by a RainFlow counting algorithm), and the predicted yearly capacity loss data.

[0106] The weighted sum measure of degradation may be averaged.

[0107] Each weight may be between 0 and 1 .

[0108] Each weight may be adjustable.

[0109] In one example the weights of the short term estimators (e.g. Degradescp and DegradeTemp) may be higher than the long-term estimators (DegradeBMs, DegradeRainFiow, and Deg radOyearlyloss) ■

[0110] The weight may depend on the estimate, e.g. the strength or reliability or accuracy of the estimate.

[0111] In some examples, the weight may be 1 for the “short-term estimators,” e.g. the battery cell data and / or temperature data, or approximately 1 , or substantially 1 , or close to 1. Therefore, in some examples WBCP “ 1 and / or WTEMP « 1 . In this way, the short-term estimators, being that they are values in real-time or near-real-time, have a higher weighting (than longterm estimators) as they have a more immediate effect on the health of the battery cell and / or unit and / or vessel operation.

[0112] Alternatively or additionally, in some examples, the weights may be adjusted based on ongoing operation of the cell and / or battery unit, for example based on a measure of how critical the operation of the vessel is or based on how critical the state of the battery cells and / or battery unit is. For instance, for a parameter determined to be critical, the weight may be assigned 1 or close to 1 to reflect the impact of this parameter on the degradation.

[0113] Alternatively or additionally, in some examples the weights may be adjustable, e.g. automatically, based on the availability of a battery unit (and therefore a cell in the battery unit). In some examples the availability of a battery unit cell may be set by a user.

[0114] Alternatively or additionally, in some examples the weights may be based on the health of a battery unit cell or of the battery unit, as determined by any metric as above.

[0115] The weights may be based on an error in any parameter. For example, an error in any measurement or parameter may be determined, and if there is any error (e.g. a substantial error) in any measurement used to determine the degradation estimate then this weight may be set to 0 so as not to propagate the error. Therefore, the disclosure may comprise determining whether any error is present in any measurement and, if so, setting the weight to be 0 in the corresponding degradation function.

[0116] Alternatively or additionally, an impact of a measure of degradation may be determined and the weights may be based on a level in impact (a parameter corresponding to a higher impact having a higher weighting for its associated degradation function, a parameter corresponding to a lower impact having a lower weighting for its associated degradation function, a parameter corresponding to a low impact may have its weight set to 0).

[0117] Each degradation estimate may be expressed as a percentage.

[0118] By way of summary, in this way the controller 100 obtains a real-time or near-real time property of the battery unit 102 and supplements this with a SOH as determined by a BMS 104 to determine a measure of battery degradation with increased accuracy. The cell property described by the battery data may be at least one of the properties described above, and in some examples the measure of degradation may be based on other data (e.g. ambient temperature data, battery profile data, or capacity data).

[0119] In a further example the controller 100 is configured to cause visual and / or numerical information to be displayed on a display device, the visual and / or numerical information may comprise at least one of information on current cell and / or battery unit SOH (e.g. current vs planned), the hourly, daily, and / or weekly cell and / or battery unit (e.g. current vs planned), and accumulated utilization and / or forecast data for a cell and / or a battery unit. In this way, a user may view this information to inform their decisions. Alternatively or additionally any one of the parameters discussed herein, and any part of the process, may be caused to be displayed on a display. For instance, an interactive display may allow the user to adjust the weights or decide the parameters that any particular health estimation is to be based on etc. (e.g. which “other data” is taken into account or how many of the SOH charge / discharge, CCCT parameters etc. parameters that the battery health data is to be based on). In some examples the controller is configured to obtain an acceptable limit of the battery unit when it is charging and / or discharging and to determine if the battery unit breaches the acceptable limit. If this is the case the controller may be configured to disconnect the battery unit and / or the battery string (or cause the battery system to be operated such that the battery unit is used less in generating battery power) and / or to cause a new charge or discharge limit to be set for the battery unit, then if the battery unit is determined to exceed the new charge or discharge limit the controller may be configured to disconnect the battery unit and / or string (or cause the battery system to be operated such that the battery unit is used less in generating battery power).

[0120] In some examples the controller may be configured to determine the energy in and energy out of the battery unit and to determine whether there is any discrepancy between the energy in and energy out to determine whether there are any losses in energy through the battery unit. This may be done during idling of the battery unit. If there are losses then the controller may be configured to disconnect the battery unit and / or the battery string (or cause the battery system to be operated such that the battery unit is used less in generating battery power).

[0121] Figure 3 shows an example controller 301 according to this disclosure. The controller 301 may be the same controller as the controller 100 or may be different depending on the example. The controller 301 is to determine an operating mode of a battery unit 102 that is configured to supply power to a power consumer of a marine vessel. The controller 301 is configured to obtain data relating to an operational mode of the vessel, schematically depicted as being received from a vessel data module 303 in Figure 3, the vessel data including at least one objective that the marine vessel is to achieve using the power consumer supplied by power from the battery unit. The controller 301 is further configured to obtain data relating to a measure of degradation of the battery unit, schematically depicted as being received from a battery data module 305. The measure of degradation of the battery unit may be calculated by the controller 100, or may be calculated by the controller 301 , but in any case may be determined according to the process 200 as outlined above. The controller 301 is to determine, based on the measure of degradation, a set of battery control parameters for controlling the battery unit in an operating mode in which the battery unit is controlled to supply power to the power consumer such that the marine vessel is able to achieve the objective and that degradation of the battery unit is minimised.

[0122] To illustrate the operation of the controller 301 reference is now made to Figure 4.

[0123] Figure 4 shows an example process 400. The controller 301 of Figure 3 may be configured to perform all or part of the process 400 to determine the set of battery control parameters. At S402 the process comprises obtaining data relating to the operational mode of the vessel, as described above (termed “vessel data” in Figure 4). At S404 the process the process comprises obtaining battery degradation, as described above. At S406 the process comprises determining, based on the measure of degradation, a set of battery control parameters for controlling the battery unit in an operating mode in which the battery unit is controlled to supply power to the power consumer such that the marine vessel is able to achieve the objective and that degradation of the battery unit is minimised. Determining the battery control parameters, at S406, may comprise receiving the parameters (e.g. from another entity) or retrieving the parameters (e.g. from a database), or calculating the battery control parameters.

[0124] The power consumer of the marine vessel may be any component of the vessel that is configured to perform a task based on electrical power. As such, the battery unit may supply electrical power to the power consumer in full or in part (e.g. in combination with power from an internal combustor). The objective achieved by the marine vessel may be any task that any part of the vessel is to perform using the power consumer supplied with power from the battery. For instance, the marine vessel may be assigned the objective of heading to a waypoint for which various propulsors of the vessel may be operated to maintain a vessel’s heading, in which case a dynamic positioning (“DP”) algorithm may be used to control the vessel’s propulsors. In this example, the battery control parameters are to control the battery unit to supply power to at least one propulsor such that the marine vessel can complete its assigned objective under DP, but such that the degradation of the battery unit is minimised. In another example the marine vessel may be operated to dock at a particular port and the battery control parameters are to control the battery unit to supply power to at least one propulsor such that the vessel can complete it’s docking operation but such that the degradation of the battery unit is minimised. In some examples the process therefore comprises operating, or controlling, the battery unit according to the set of determined battery control parameters, as indicated at S416. It will be appreciated that when the measure of degradation calculated by the Figure 2 process is used in the Figure 4 process, the battery control parameters can accurately manage the operation of the battery such that its degradation is minimised.

[0125] As indicated by the dotted boxes, in some examples, further steps are performed before the battery control parameters are adopted, e.g. used to control the battery. In one example, the battery control parameters are used to determine a trade-off between the energy efficiency of the marine vessel, as a whole, and the safety of the marine vessel in achieving the objective when the battery control parameters are used to control the battery to supply power to the power consumer. One example way of achieving this is shown in Figure 4. At S408 the process comprises obtaining an energy efficiency index indicating a predicted energy efficiency for the marine vessel achieving the objective when the power consumer is powered by the battery unit, operating in the operating mode according to the battery control parameters. At S410 the process comprises obtaining a safety index indicating a predicted safety level for the marine vessel achieving the objective when the power consumer is powered by the battery unit, operating in the operating mode according to the battery control parameters. At S412 a combined index is determined representing the trade-off between energy efficiency and safety. The combined index may be a weighted sum:

[0126] Combined Index = WEE*EE + Ws*S with EE and S denoting the energy efficiency and safety indexes respectively and WEE and Ws, their weights.

[0127] This part of the process allows an operator to determine whether the calculated battery control parameters are going to control the marine vessel component acceptably, in view of the trade-off between energy efficiency and vessel safety. The weights in the combined index may be set, and adjusted, to reflect the desired trade-off of the user. For instance, it may be desired to prioritise safety in which case Ws may be greater than WEE.

[0128] Deciding whether the battery control parameters are suitable for implementation may be done therefore by a user however the process may permit this to be done automatically. At S414 the process compares the combined index to a predetermined threshold and, if the combined index is greater than the predetermined threshold, then the battery control parameters are considered acceptable and adopted, S416. Otherwise, the process returns to S406 and new battery control parameters are determined and a new combined index is created etc. This may be done immediately following S414 or new battery control parameters may be determined at regular predetermined time intervals until at S414 a set is deemed to be acceptable.

[0129] In one example determining the battery control parameters, S406, comprises retrieving the battery control parameters from a database. In one example, battery control parameters are stored with metadata assigning them a category. The battery control parameters may be categorised, via the metadata, in at least one of the following categories: optimal, best, good, from the point of view of minimising battery degradation if the battery were to be controlled according to these parameters. In other words, each set of parameters may correspond to a measure as to the future degradation of the battery cell or unit, e.g. a predicted degradation, and the category reflects that. “Optimal” may mean according to a recommendation of the manufacturer, “best” may mean deviating from the recommendation by a predetermined margin (e.g. a small margin), and “good” may mean deviating from the recommendation by an amount outside of a predetermined margin (e.g. by a large margin) (which may have a minor effect on the battery cell and / or unit heath over time).

[0130] In one example determining the battery control parameter at S406 may comprise determining the battery control parameters that are stored with metadata indicating that they are optimal. Then, if at S414, the process determines that the battery control parameters are not acceptable the method may comprise determining the next category of battery control parameters (e.g. if the ‘optimal’ parameters are not acceptable then the process may select the ‘best’ parameters) and the process continues. If the ‘best’ parameters are not accepted then the process may return to S406 and select the ‘good’ parameters. In other words, the process may comprise determining, or retrieving, a set of battery control parameters that have the highest ranking based on predicted degradation and determining the combined index for those parameters. If the combined index does not meet the predetermined threshold then the process repeats by determining, or retrieving, a set of battery control parameters that have the next-highest ranking based on predicted degradation and determining the combined index for those new set of parameters.

[0131] In one example S406 may comprise determining battery control parameters and determining a predicted degradation if the battery cell and / or unit were controlled according to these parameters. The method may further comprise assigning a category to the battery control parameters that depends on the determined predicted degradation (e.g. “optimal,” “best,” “good,” as described above).

[0132] Any one or more of S408-S412 may be performed by a balance engine, balance module, or balance profile, since it computes a trade-off (e.g. a balance) between the abovementioned two quantities. Such an engine, module, or profile etc. may be part of the controller 301. By way of one example, if the user is to prioritize safety then they may assign Ws = 0.85 and WEE = 0.15 and may set the predetermined threshold to be 0.6. In this example, when the set of battery control parameters are determined and the energy and safety indices are determined for the component controlled by the battery operating according to those parameters, if it is determined that the combined index is greater than 0.6 then the battery control parameters may be automatically adopted, e.g. used to control the battery and therefore this part of the process is automated. If the user’s preference changes they may change the weights.

[0133] As indicated by the looping arrows, vessel data and battery degradation data may be obtained at regular predetermined time intervals, so that battery control parameters are determined at regular intervals. In this way, use of the battery unit may be continually optimised.

[0134] It will be appreciated that greater may mean “greater than or equal to.” Some examples may also adopt the battery control parameters if the combined index is less than, or less than or equal to, depending on the example.

[0135] In order to control the battery to minimise its degradation and maximise its battery life, the battery control parameters determined at S406 may be to control the charging rate of at least one cell in the battery unit, the depth of discharge of at least one cell in the battery unit, the temperature of at least one cell in the battery unit, and / or how the cells of the battery unit are balanced. Alternatively or additionally, the battery control parameters are to control at least one of: the power-to-capacity ratio of at least one cell; the charge rate of at least one cell, the discharge rate of at least one cell, the acceleration coefficient of at least one cell, the voltage deviation of at least one cell during charging, the voltage deviation of at least one cell during discharging, and a property of a bus connected to the battery unit.

[0136] For the avoidance of doubt the two processes 200 and 400 may be performed separately but the same controller 100, 301 or by separate controllers 100, 301 but they may also be performed together by the same controller (e.g. 100 or 301). For instance, any method of determining battery control parameters may be used at S212 of the process 200 but in one example these are determined using the process 400 (and therefore may comprise determining the two indexes, and the combined index etc.) On the other hand, any measure of degradation may be obtained at block S404 but in one example S404 comprises blocks S202-S206, e.g. the measure of degradation may be determined according to the process 200.

[0137] Figure 5 shows a large-scale system 500 which is at least in part on-board a marine vessel. Figure 5 shows a battery unit 502 connected to a BMS 504 and a HSIO 508 as described above with reference to Figure 1. A cooling module 506 which is configured to determine temperature inside or external to at least one cell of the battery unit 502 is connected to the battery unit 502 and to the BMS 504 which may determine the state of health data based on temperature data received from the cooling module 506. The BMS 504, HSIO 508, and cooling module 506 are connected to a battery health calculator 512 which is connected to an energy management system (“EMS”) 514. The EMS 514 is connected to a mission management module 516 which is connected to a remote operations centre 518. The battery unit 502 may be as described above and comprise a plurality of battery cells. The battery unit 502 may also be a battery system and may therefore comprise a plurality of battery units, or modules, connected in series to form “strings” which are connected together in parallel. In any case, the battery unit 512 may be connected to the ship power system via a converter configured to regulate the output voltage or may be connected to the ship power system directly without a converter.

[0138] The battery health calculator 512 may be configured to determine a status of at least one cell of the battery unit, or a status of the battery unit as a whole, for example a load, charge, discharge, SoC, or temperature. The battery health calculator 512 may receive battery cell data from 508, temperature data from 506, and state of health data from 504. The battery health calculator 512 may be configured to determine the battery power profile (e.g. using RainFlow counting). In one example, the battery health calculator may be configured to determine a battery power profile using a machine learning algorithm trained on historical battery parameter and performance data and configured to output a battery power profile, and for example may be the machine learning model as described above with reference to the neural network. In some examples the battery health calculator 512 may be configured to determine the measure of degradation of a cell of the battery unit 502 (and therefore may comprise the controller 100 as described above and / or may be configured to perform the process 200 as described above).

[0139] The EMS 514 may, at least in part, determine how to manage the power suppliers of the marine vessel, including the battery unit 102. The EMS 514 may therefore determine the battery control parameters (and may therefore comprise the controller 300 as described above and / or may be configured to perform the process 400 as described above). The EMS 514 may in some examples be configured to determine the measure of degradation of a cell in the battery unit 502 (and therefore may comprise the controller 100 as described above and / or may be configured to perform the process 200 as described above).

[0140] The mission management module 516 may communicate with the EMS 514 and may receive mission data from the remote operations centre 518. The remote operations centre 518 may determine vessel data relating to an operational mode of the vessel, including at least one objective that the marine vessel is to achieve, for example using the power consumer supplied by power from the battery unit. Alternatively, the remote operations centre 518 may transmit a signal to the mission management module 516 that causes the mission management module 516 to determine the vessel data. It will be appreciated that any one or more of the EMS 514, the mission management module 516, and the remote operations centre 518 may comprise the controller 300 and may be configured to perform the process 400.

[0141] In fact, it will be appreciated that, although the claims recite a system, such a system may comprise any one or more of the controller 100, the controller 300 or any one or more of the components of Figures 1 , 3, and 5 (e.g. the individual modules described above). The controller 100 and / or the controller 300 may be part of an energy management system (“EMS”) for the vessel.

[0142] The controller 100 or 300 may comprise processing circuitry configured to cause the controller 100 or 300 to operate according to a process, or to perform a process - for example the processes 200 or 400 as described above. The processing circuitry may be implemented according to any suitable hardware and / or software combination sufficient to cause such a process to be executed. For instance the processing circuitry may be implemented on, or on any suitable combination of, a digital signal processor, field programmable gate array, and / or application specific integrated circuit (ASIC). The processing circuitry may be configured to execute instructions, such as processor control code, that, cause the controller 100 or 300 to operate according to the process. Such instructions may be stored on a non-transitory machine-readable medium. Such instructions may be stored in a memory. Such instructions may be stored on any suitable memory medium, e.g. on a volatile or non-volatile medium, programmed memory (e.g. read-only memory such as firmware), or a data carrier. The processing circuitry may comprise such a memory storing the instructions. In other words, a non-transitory machine-readable medium may store instructions that, when executed by processing circuitry, cause the process 200 or 400 to be performed. The instructions may comprise code or microcode. The instructions, when executed, may be in any suitable programming language to allow the controller 100 or 300 to be dynamically configured and / or reconfigured. The controller and / or processing circuitry may equally comprise, and may therefore be referred to as, a processor, microcontroller or microprocessor. The person skilled in the art realizes that the present disclosure by no means is limited to what is explicitly described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. Additionally, variations can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

Claims

CLAIMS1. A system for determining a measure of degradation of a battery unit of a battery system, the battery system comprising at least one battery string, the battery string comprising a plurality of battery units, the battery system being configured to be used as a power supply for a power consumer of a marine vessel, the system being configured to: obtain state of health data comprising a predicted or estimated indication of the remaining useful life of the battery unit; obtain battery data comprising a property of the battery unit obtained in real time or near-real time; and determine, based on the state of health data and the battery data, a measure of degradation of the battery unit.

2. The system of claim 1 , wherein the property of the battery unit comprises at least one of: voltage behaviour during charging of the battery unit; voltage behaviour during discharging of the battery unit; current behaviour during a constant voltage charging phase of the battery unit; and voltage behaviour upon cycling the battery unit.

3. The system of claim 1 or 2 wherein the property of the battery unit comprises at least one of: the battery unit state of health upon charging; the constant current charging time; the constant voltage charge time; the ratio of the constant voltage charge time to the constant current charge time; the battery unit state of health upon discharging; the coulomb efficiency; the constant current discharge time; the constant voltage current profile; the integral of the voltage over the charge; the integral of the voltage over discharge; the open-circuit voltage; and the rate of voltage change over the charge.

4. The system of any preceding claim, the system being configured to:obtain data relating to a battery power profile, wherein the measure of degradation of the battery unit is determined based on the data relating to the battery power profile.

5. The system of claim 4, wherein the data relating to the battery power profile comprises at least one of: a number of charge cycles of the unit; a number of discharge cycles of the unit; the depth of discharge of the unit; a number of half cycles of the unit; and a number of full cycles of the unit.

6. The system of claim 4 or 5 wherein the data relating to the battery power profile is determined using a Rain-Flow counting algorithm.

7. The system of any preceding claim, the system being configured to: obtain air flow data relating to the air flow in a region exterior to the battery unit, wherein the measure of degradation of the battery unit is determined based on the air flow data.

8. The system of any preceding claim, the system being configured to: obtain capacity data indicating a predicted yearly capacity loss of the battery unit, wherein the measure of degradation of the battery unit is determined based on the capacity data.

9. The system of any preceding claim, wherein the battery data is received from a highspeed input-output module configured to obtain the battery parameter in real time or near- real time, the high-speed input-output module being connected to the battery unit.

10. The system of any preceding claim, wherein the measure of degradation comprises a weighted sum of first and second quantities, the first quantity being based on the state of health data, the second quantity being based on the battery data.

11. The system of any preceding claim, the system being configured to: obtain data relating to an operational mode of the vessel, including at least one objective that the marine vessel is to achieve using the power consumer supplied by power from the battery system;determine, based on the measure of degradation, a set of battery control parameters for controlling the battery system in an operating mode in which the battery system is controlled to supply power to the power consumer such that the marine vessel is able to achieve the objective and that degradation of the battery unit is minimised.

12. The system of claim 11 , the system being configured to determine the trade-off between the energy efficiency of the marine vessel and the safety of the marine vessel based on the marine vessel achieving the objective when the power consumer is powered by the battery system, operating in the operating mode according to the battery control parameters.

13. The system of claim 11 or 12, wherein determining the trade-off comprises: obtaining an energy efficiency index indicating a predicted energy efficiency for the marine vessel achieving the objective when the power consumer is powered by the battery system, operating in the operating mode according to the battery control parameters; obtaining a safety index indicating a predicted safety level for the marine vessel achieving the objective when the power consumer is powered by the battery system, operating in the operating mode according to the battery control parameters; and determining a combined index based on the energy efficiency index and the safety index.

14. The system of claim 13, wherein, if the combined index exceeds a predetermined threshold, the system is configured to determine a new set of battery control parameters.

15. The system of any of claims 11-14 wherein the battery control parameters are to control at least one of: the charging rate of the battery unit; the depth of discharge of the battery unit; the battery temperature; and balancing cells of the battery unit.

16. The system of any of claims 11-15, wherein the battery control parameters are to control at least one of: the power-to-capacity ratio of the battery unit; the charge rate of the battery unit; the discharge rate of the battery unit; the acceleration coefficient of the battery unit;the voltage deviation of a battery unit during charging; the voltage deviation of a battery unit during discharging; and a property of a bus connected to the battery unit.

17. A system for determining an operating mode of a battery system configured to supply power to a power consumer of a marine vessel, the battery system comprising at least one battery string, the battery string comprising a plurality of battery units, the system being configured to: obtain data relating to an operational mode of the vessel, including at least one objective that the marine vessel is to achieve using the power consumer supplied by power from the battery system; obtain data relating to a measure of degradation of a battery unit of the battery system; determine, based on the measure of degradation, a set of battery control parameters for controlling the battery system in an operating mode in which the battery system is controlled to supply power to the power consumer such that the marine vessel is able to achieve the objective and that degradation of the battery unit is minimised.

18. The system of claim 17, the system being configured to determine the trade-off between the energy efficiency of the marine vessel and the safety of the marine vessel based on the marine vessel achieving the objective when the power consumer is powered by the battery system, operating in the operating mode according to the battery control parameters.

19. The system of claim 18, wherein determining the trade-off comprises: obtaining an energy efficiency index indicating a predicted energy efficiency for the marine vessel achieving the objective when the power consumer is powered by the battery system, operating in the operating mode according to the battery control parameters; obtaining a safety index indicating a predicted safety level for the marine vessel achieving the objective when the power consumer is powered by the battery system, operating in the operating mode according to the battery control parameters; and determining a combined index based on the energy efficiency index and the safety index.

20. The system of claim 19, wherein, if the combined index exceeds a predetermined threshold, the system is configured to determine a new set of battery control parameters.

21. The system of any of claims 18-20 wherein the battery control parameters are to control at least one of: the charging rate of the battery unit; the depth of discharge of the battery unit; the battery temperature; and balancing cells of the battery unit.

22. The system of any of claims 18-21, wherein the battery control parameters are to control at least one of: the power-to-capacity ratio of the battery unit; the charge rate of the battery unit; the discharge rate of the battery unit; the acceleration coefficient of the battery unit; the voltage deviation of the battery unit during charging; the voltage deviation of the battery unit during discharging; and a property of a bus connected to the battery unit.

23. The system of any of claims 18-22, wherein the measure of degradation of the battery unit is determined based on state of health data comprising a predicted or estimated indication of the remaining useful life of a battery unit, and battery data comprising a property of the battery unit obtained in real time or near-real time.

24. The system of claim 23, wherein the property of the battery unit comprises at least one of: voltage behaviour during charging the battery unit; voltage behaviour during discharging the battery unit; current behaviour during a constant voltage charging phase of the battery unit; and voltage behaviour upon cycling the battery unit.

25. The system of claim 23 or 24 wherein the property of the battery unit comprises at least one of: the battery unit state of health upon charging; the constant current charging time; the constant voltage charge time; the ratio of the constant voltage charge time to the constant current charge time; the battery unit state of health upon discharging;the coulomb efficiency; the constant current discharge time; the constant voltage current profile; the integral of the voltage over the charge; the integral of the voltage over discharge; the open-circuit voltage; and the rate of voltage change over the charge.

26. The system of any of claims 23-25, wherein the measure of degradation of the battery unit is based on data relating to a battery power profile.

27. The system of claim 26, wherein the data relating to the battery power profile comprises at least one of: a number of charge cycles of the unit; a number of discharge cycles of the unit; the depth of discharge of the unit; a number of half cycles of the unit; and a number of full cycles of the unit.

28. The system of claim 26 or 27 wherein the data relating to the battery power profile is determined using a Rain-Flow counting algorithm.

29. The system of any of claims 23-28, wherein the measure of degradation of the battery unit is based on air flow data relating to the air flow in a region exterior to the battery unit.

30. The system of any of claims 23-29, wherein the measure of degradation of the battery unit is based on capacity data indicating a predicted yearly capacity loss of the battery unit.

31. The system of any of claims 23-30, wherein the measure of degradation of the battery unit is based on state of health data relating to the respective state of health of a plurality of battery units as determined by a battery management system, the state of health data for a respective battery unit comprising a predicted or estimated indication of the remaining useful life of the battery unit, and battery data for the plurality of battery units comprising a property of each battery unit obtained in real time or near-real time.

32. The system of any of claims 23-31 , wherein the measure of degradation comprises a weighted sum of first and second quantities, the first quantity being based on the state of health data, the second quantity being based on the battery data.

33. The system of any of claims 23-32, the system being configured to determine the measure of degradation of the battery unit.

34. A system for determining a measure of degradation of a battery unit comprising a plurality of battery cells and configured to be used as a power supply for a power consumer of a marine vessel, the system being configured to: obtain short-term state of health data relating to a short-term estimate of the health of a battery cell; obtain long-term state of health data relating to a long-term estimate of the health of a battery cell; the short-term estimate being obtained more recently than the long-term estimate and determine, based on the short-term and long-term state of health data, a measure of degradation of the battery unit.

35. The system of claim 34 wherein the short-term state of health data is obtained in real time or near real time.

Images