Patent Description:
Energy-storage devices may include battery packs, such as lithium-ion (or "Li-Ion") battery packs and lead-acid battery packs. A Li-Ion battery pack may include an array of Li-Ion cells, or a "cell assembly," and a battery management system (BMS) to monitor, control, and protect the cell assembly to meet functional and safety requirements. The BMS may need to be functional (partly or fully) during the entire life of the battery pack including shipment, storage, and shelf conditions, and consumes power from the battery pack. <CIT> discloses a low-voltage threshold adjusting method comprising: detecting whether the current voltage is lower than a low-voltage threshold value; when the current voltage is lower than the low-voltage threshold value, detecting whether the current exceeds a preset current threshold value; when the current exceeds the preset current threshold value, detecting whether the current temperature exceeds a preset temperature; if the current temperature does not exceed the preset temperature, checking whether a current charge value is higher than a preset charge value; and when the current charge value is higher than the preset charge value, reducing the low-voltage threshold value. <CIT> discloses a power management circuit for a battery cell that is coupled to a load through an output terminal. The power management circuit includes: a current detection circuit, a loading determination circuit, and a voltage determination circuit. The current detection circuit detects a discharge current of the battery cell when the battery cell is discharged through the load to generate a discharge-current signal. The loading determination circuit determines a loading value of the load according to the discharge-current signal to generate a loading signal. When the battery voltage of the battery cell drops to the cut-off voltage, the power management circuit terminates the discharge of the battery call through the load.

According to aspects of the present disclosure, there are provided a method, a battery system, a computer program and a computer-readable medium according to the appended claims.

Examples of the methods and systems discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The methods and systems are capable of implementation in other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. In particular, acts, components, elements and features discussed in connection with any one or more examples are not intended to be excluded from a similar role in any other examples.

Any references to examples, embodiments, components, elements or acts of the systems and methods herein referred to in the singular may also embrace embodiments including a plurality, and any references in plural to any embodiment, component, element or act herein may also embrace embodiments including only a singularity. References in the singular or plural form are not intended to limit the presently disclosed systems or methods, their components, acts, or elements. The use herein of "including," "comprising," "having," "containing," "involving," and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

References to "or" may be construed as inclusive so that any terms described using "or" may indicate any of a single, more than one, and all of the described terms. In addition, in the event of inconsistent usages of terms between this document and documents incorporated herein by reference, the term usage in the incorporated features is supplementary to that of this document; for irreconcilable differences, the term usage in this document controls.

A Li-Ion battery pack may include one or more battery cells and a battery management system (BMS). The battery pack may be coupled to, and provide power to, a load. The battery pack discharges power to the load. For example, a battery pack may be coupled to an uninterruptible power supply (UPS) to provide continuous, uninterrupted power to a load connected to the UPS. The battery pack may also be coupled to a power source. The power source provides power to the battery pack to recharge the battery pack. For example, the battery pack may be coupled to a utility-grid power supply either directly or via the UPS.

Although the Li-Ion battery pack may be configured to be coupled to provide power to a load, the battery pack is typically not coupled to a load immediately after manufacture. For example, the Li-Ion battery pack may be placed in storage and/or may be shipped to a user before being coupled to a load. This duration of time may be referred to as a storage life. As used herein, a "storage life" includes the time between manufacturing and installation of a battery in an application. This duration includes the transportation, storage at a warehouse, and so forth. In some examples, the storage life may include such transportation and storage at a warehouse after installation as well, such as if the battery pack is removed from a first application, stored, and/or transported to a second application. The state of charge during shipment and/or storage may be stipulated by regulatory authorities. During this period, the state of charge of the battery pack may be maintained within a stipulated range at a warehouse such that a life of the battery pack is not significantly affected.

Once a battery pack is in use, it may be considered to have begun its active life. As used herein, an "active life" includes a time duration for which a battery pack is installed and used in an intended application. During this period, the battery pack may be subjected to continuous charge and discharge cycles. Often the application requires the batteries to cycle between full charge to complete discharge. During the active life, the battery pack may be in one of several modes of operation, including an active mode.

As used herein, in an "active mode" a BMS is fully functional and the power consumed by the BMS is maximized. The BMS operates in this mode during the normal usage of the battery pack. This may have multiple sub-modes of operation. Two sub-modes include a charge mode and a discharge mode. As the power consumed by the BMS is high in the active mode, the active mode may not be used during shipment, storage, and/or shelf conditions.

As used herein, in a "charge mode" the battery pack receives energy from a power source, such as a source of utility power, to recharge the battery cells. The BMS operates in the charge mode if the utility power is within the acceptable range (for example, an acceptable range of voltage values). The battery pack can be considered to reach its full stored capacity if the battery voltage reaches a first pre-determined threshold level (TL-<NUM>), which may be a voltage level. After reaching this voltage level the BMS may sustain the battery voltage level around this value.

As used herein, in a "discharge mode" the battery pack provides power to a load. The BMS may operate in the discharge mode if, during the active mode, the utility power is outside the acceptable range. During the discharge mode, the voltage level of the battery cells may decrease as the battery cells discharge energy to the load. If the battery voltage level reaches (or falls below) a second predetermined threshold level (TL-<NUM>), which may be a voltage level, then the BMS would move to "shelf mode <NUM>," or a "first shelf mode.

In this mode, the battery pack may cease discharging power to a load. Accordingly, if the voltage level of the battery pack reaches the predetermined level TL-<NUM>, then the battery is said to have reached "end of discharge. " As used herein, a "runtime (Tr)" includes the time taken by the battery pack to transition from a fully charged condition (voltage threshold level TL-<NUM>) to the end of discharge (voltage threshold level TL-<NUM>) as the battery pack discharges. In various examples, an estimated runtime may be specified or predicted based on a specified load and other predetermined conditions, such as temperature, humidity, and so forth. Similarly, as used herein, a "recharge time (Tchg)" includes the time taken by the battery pack to charge from the end of discharge condition to a fully charged condition. In various examples, an estimated recharge time may be specified or predicted based on specified input AC parameters (for example, power, current, and so forth) and other predetermined conditions, such as temperature, humidity, and so forth.

The BMS may remain substantially functional and the battery pack may return to active mode as soon as a source of power, such as the utility power, is available to the battery pack. However, some functionality of the BMS may be disabled during the first shelf mode as compared to the discharge mode, such that power consumption is reduced. The power consumed by the BMS in this mode is significantly lower than the discharge mode, but may be higher than a second shelf mode, described below. The shelf life duration in the first shelf mode may be designated as T1.

A voltage of the battery cells may continue to decrease even if power is not being discharged to a load. For example, a voltage of the battery cells may decrease due to a leakage current discharged by the battery cells and/or due to maintaining some functionality of the BMS. If the battery voltage reaches (or falls below) a third predetermined threshold level (TL-<NUM>) then the BMS may move to "shelf mode <NUM>," or a "second shelf mode. " In this mode, all functionalities of the BMS may be disabled such that the BMS is considered to be in an off mode. The battery pack may return to active mode with significant delay after an AC source is applied to it. The power consumed by the BMS in this mode is minimal and hence most suited for shipping, storage, and/or shelf conditions. The shelf life duration in this mode may be designated as T2.

Accordingly, the first and second shelf modes may increase a life of the battery pack by disabling functionality of the battery pack when the battery pack is discharged to corresponding discharge levels, which may be voltage levels. This may advantageously increase a lifetime of the battery pack by avoiding over-discharge, which may adversely affect a health of the battery pack. As used herein, the "shelf life (Ts)" refers to a total time spent by the battery pack in the shelf moves (that is, a cumulative time in the first and second shelf moves). Hence, Ts = T1 + T2.

The battery pack may eventually reach an end-of-life state in which the battery pack is irrecoverable and should be replaced. As used herein, in an "irrecoverable mode" the battery pack is rendered irrecoverably unusable. The battery pack may enter the irrecoverable mode if, in the second shelf mode, the battery voltage level reaches (or falls below) a fourth predetermined threshold level (TL-<NUM>), which may be a voltage level.

In an intended application, often there are conditions or times during which a battery pack is not connected to a power source to recharge the battery pack. For example, the battery pack may be disconnected from the power source (such as a utility grid) or a charger may not be active for a period of time. Examples of conditions may include the equipment being unplugged from mains for an extended period, long power outages followed by a complete discharge of the battery, and an AC voltage being out of acceptable range for an extended period. If the battery pack does not receive any replenishment charge during this period, the battery pack may be adversely affected. As discussed above, the time spent in such states may refer to the shelf life of the battery pack. In various examples, the shelf life may be less than the storage life. Accordingly, it may be beneficial to increase a battery shelf life such that a burden on a customer to maintain a state of charge of the battery is reduced.

In various examples, a voltage level of a battery pack may be determined. The battery pack may be controlled to be in a certain mode of operation depending on whether the voltage level is within certain discharge thresholds or ranges. Each mode of operation may correspond to a respective discharge threshold or range. As the battery pack is discharged, the voltage level may decrease and a mode of operation of the battery pack may be altered as the voltage level falls within different discharge thresholds or ranges.

Examples of the disclosure include modifying discharge thresholds demarcating different modes of operation such that a battery shelf life is maximized. Lower voltage thresholds may correspond to modes of operation exhibiting lower power consumption. Modifying the discharge thresholds may include increasing the discharge thresholds. Accordingly, the battery pack may be controlled to enter the modes of operation exhibiting lower power consumption more quickly, because the discharge thresholds are increased.

The discharge thresholds may be modified based on one or more operational parameters. The operational parameters may indicate whether the battery pack is being used in a normal application. The discharge thresholds may be increased if the battery pack is not being used in a normal application, such as in abnormal applications that degrade a health of the battery pack more quickly. It may be advantageous to minimize an amount of time that the battery pack is used in these applications to maximize the lifetime of the battery pack, which can be achieved by increasing the discharge thresholds.

In one example, the one or more operational parameters indicate a current state of charge (SOC) of the battery pack. The discharge thresholds may be increased responsive to determining that the SOC of the battery pack is below a threshold SOC. For example, the discharge thresholds may be increased responsive to determining that a current SOC of the battery pack is less than <NUM>% of an initial full SOC of the battery pack.

In another example, the one or more operational parameters indicate a present load of the battery pack. The discharge thresholds may be increased responsive to determining that the load on the battery pack is below a threshold load. For example, the discharge thresholds may be increased responsive to determining that a current load on the battery pack is less than <NUM>% of a rated load of the battery pack.

Accordingly, a lifetime of the battery pack may be increased by increasing discharge thresholds demarcating different modes of operation. The discharge thresholds may be increased where the battery pack is not being used in a normal application. Current battery systems, such as battery packs in UPSs, may implement static discharge thresholds for determining a mode of operation of the battery pack. Such battery systems may operate inefficiently, because the battery pack may be operated in non-normal applications, which may rapidly degrade a health of the battery pack, for a significant amount of time. This is a technical problem.

An exemplary embodiment of a battery system is provided comprising an output configured to provide output power to a load, one or more battery cells configured to store electrical energy to provide to the load, and a battery management system configured to receive one or more operational parameters of the battery system, determine whether the one or more operational parameters are less than at least one operational-parameter threshold, modify a discharge threshold of the one or more battery cells responsive to determining that the one or more operational parameters are less than the at least one operational-parameter threshold, and control the battery system to be in a battery-optimization mode responsive to determining that a discharge level of the one or more battery cells is below the discharge threshold.

At least this foregoing combination of features comprises a battery system that serves as a technical solution to the foregoing technical problem. This technical solution is not routine and is unconventional. This technical solution is a practical application of the battery-system design that solves the foregoing technical problem and constitutes an improvement in the technical field of battery-pack systems at least by increasing a lifetime of the battery pack to maximize an amount of use that users may receive from battery packs.

<FIG> illustrates a block diagram of a battery system <NUM> according to an example. The battery system <NUM> may be configured to provide stored power to a load. For example, the battery system <NUM> may be implemented in, or in connection with, a UPS configured to provide continuous, uninterrupted power to a load. In other examples, the battery system <NUM> may provide power to one or more loads other than in connection with a UPS. The battery system <NUM> includes an input <NUM>, an output <NUM>, a battery management system (BMS) <NUM>, one or more battery cells <NUM> ("battery cell <NUM>"), and a load-detection circuit <NUM>.

It is to be appreciated that aspects of the battery system <NUM> are illustrated for purposes of explanation, and that certain aspects may be combined, replaced, or added. For example, in some implementations the load-detection circuit <NUM> may be a component of the BMS <NUM>. In another example, the input <NUM> and the output <NUM> may be a single physical connection, and are illustrated separately for purposes of explanation only.

The input <NUM> is coupled to the battery cell <NUM>, and is configured to be coupled to a source of input power, such as a utility mains. In some examples, the input <NUM> may be communicatively coupled to the BMS <NUM>. The output <NUM> is coupled to the load-detection circuit <NUM>, and is configured to be coupled to a load. In some examples, the output <NUM> may be communicatively coupled to the BMS <NUM>. The BMS <NUM> is communicatively coupled to the input <NUM>, the output <NUM>, the battery cell <NUM>, and the load-detection circuit <NUM>. The battery cell <NUM> is coupled to the input <NUM> and the load-detection circuit <NUM>, and is communicatively coupled to the BMS <NUM>. The load-detection circuit <NUM> is coupled to the battery cell <NUM> and the output <NUM>, and is communicatively coupled to the BMS <NUM>.

The battery cell <NUM> is configured to store electrical energy and discharge stored electrical energy to the output <NUM>. For example, where the battery system <NUM> is implemented in connection with a UPS, the battery cell <NUM> may be configured to discharge stored power to the output <NUM> when acceptable power (for example, utility mains power) is otherwise unavailable to a load coupled to the output <NUM>. The battery cell <NUM> may therefore provide uninterrupted power to a load when the load is otherwise unable to receive adequate power from a main power source, such as during a blackout.

Energy stored in the battery cell <NUM> decreases as power is discharged. The input <NUM> is configured to receive input power from a power source and provide the input power to the battery cell <NUM>. The input power recharges the battery cell <NUM> and replenishes discharged power. In some examples, the battery system <NUM> may include a charger implemented between the input <NUM> and the battery cell <NUM> to recharge the battery cell <NUM>.

The load-detection circuit <NUM> is configured to determine a load on the battery cell <NUM>. For example, the load may include an amount of power supplied by the battery cell <NUM> to a device (also called a load) coupled to the output <NUM>. The load-detection circuit <NUM> may include one or more current- and/or voltage-sensing components, such as one or more current transformers (CTs). In various examples, the load-detection circuit <NUM> may be implemented in series with the battery cell <NUM> such that power discharged by the battery cell <NUM> is measured by the load-detection circuit <NUM>. In other examples, other implementations of a load-detection component may be utilized to determine a load of the battery cell <NUM>.

The BMS <NUM> controls operation of the battery system <NUM>. For example, the BMS <NUM> may control a discharge of the battery cell <NUM>. In some examples, the battery cell <NUM> is switchably coupled to the output <NUM> and the load-detection circuit <NUM>, and the BMS <NUM> switchably couples or decouples the battery cell <NUM> from the output <NUM> and the load-detection circuit <NUM>. For example, the BMS <NUM> may couple the battery cell <NUM> to the load-detection circuit <NUM> and the output <NUM> when the battery cell <NUM> is to discharge stored power to a load coupled to the output <NUM>, and otherwise decouple the battery cell <NUM> from the output <NUM> and the load-detection circuit <NUM>. The BMS <NUM> may send and/or receive information and/or data to and/or from the input <NUM>, output <NUM>, battery cell <NUM>, and load-detection circuit <NUM>.

The battery system <NUM> may operate in one of several modes of operation, including a charge mode of operation and a discharge mode of operation. In the charge mode of operation, power is received at the input <NUM> from a power source (not illustrated) and provided to the battery cell <NUM> to charge the battery cell <NUM>. In the discharge mode of operation, the battery cell <NUM> discharges stored power to the output <NUM>. The BMS <NUM> controls the components of the battery system <NUM> in the charge mode and discharge mode of operation to perform these functions. The BMS <NUM> may control the battery system <NUM> to be in the discharge mode of operation responsive to determining that a load coupled to the output <NUM> otherwise lacks adequate power, such as because a utility mains power source is unavailable or insufficient.

It may be advantageous to stop discharging power from the battery cell <NUM> before the battery cell <NUM> is fully depleted, at least because fully depleting the battery cell <NUM> may adversely affect a health of the battery cell <NUM>. In various examples, the battery cell <NUM> may be controlled to stop discharging power when the battery cell <NUM> reaches a certain discharge threshold. For example, a voltage level of the battery cell <NUM> may decrease as the battery cell <NUM> is discharged, and the discharge threshold may be a voltage threshold. If the voltage level of the battery cell <NUM> drops below the discharge threshold, the BMS <NUM> may control the battery cell <NUM> to stop discharging power to the output <NUM>. As discussed below, there may be several voltage thresholds each corresponding to a respective mode of operation of the battery system <NUM>.

<FIG> illustrates a graph <NUM> of a cell voltage of the battery cell <NUM> over time according to an example. A y-axis of the graph <NUM> indicates a cell voltage of the battery cell <NUM>. An x-axis of the graph <NUM> indicates time. Aspects of the graph <NUM> are discussed in connection with <FIG>.

<FIG> illustrates a process <NUM> of controlling the battery system <NUM> in the discharge mode of operation according to an example. The process <NUM> may be executed at least in part by the BMS <NUM> when the BMS <NUM> determines that the battery system <NUM> should be in the discharge mode of operation. As discussed above, the BMS <NUM> may control the battery system <NUM> to be in the discharge mode of operation responsive to determining that a load coupled to the output <NUM> otherwise lacks adequate power. Aspects of the process <NUM> are discussed in connection with <FIG>.

At act <NUM>, the battery cell <NUM> is fully charged. At a full charge, a voltage of the battery cell <NUM> may be at a maximum level. A fully charged voltage level <NUM> in <FIG> indicates a voltage level of the battery cell <NUM> at a full charge according to an example. It is to be appreciated that act <NUM> is illustrated for purposes of explanation of the fully charged voltage level <NUM>. In some examples, act <NUM> may be optionally omitted. For example, the battery system <NUM> may be in the discharge mode of operation without beginning at the fully charged voltage level <NUM>. In examples in which act <NUM> is omitted, the process <NUM> may proceed to act <NUM> from act <NUM>.

At act <NUM>, the battery cell <NUM> begins discharging stored power. For example, the BMS <NUM> may control the battery cell <NUM> to discharge stored power to a load coupled to the output <NUM>. As the battery cell <NUM> discharges stored power, a voltage level of the battery cell <NUM> decreases from the fully charged voltage level <NUM>, as illustrated by a first voltage-level trace <NUM> in the graph <NUM>.

At act <NUM>, a determination is made as to whether a voltage level of the battery cell <NUM> is below a first discharge threshold <NUM>. The first discharge threshold <NUM> may indicate a discharge threshold below which the battery system <NUM> will enter a lower-power-consumption mode of operation, which may be referred to as a first shelf mode or a battery-optimization mode. As illustrated in the graph <NUM>, the first discharge threshold <NUM> is less than the fully charged voltage level <NUM>. A time that elapses between beginning to discharge the battery cell <NUM> at the fully charged voltage level <NUM> and reaching the first discharge threshold <NUM> may be referred to as a total runtime (Tr) <NUM>.

If the voltage level of the battery cell <NUM> is not below the first discharge threshold <NUM> (<NUM> NO), the process <NUM> returns to act <NUM>. Acts <NUM> and <NUM> are repeatedly executed and the voltage level of the battery cell <NUM> continues to decrease, as illustrated by the first voltage-level trace <NUM>. If a determination is made at act <NUM> that the voltage level of the battery cell <NUM> is below the first discharge threshold <NUM> (<NUM> YES), then the process <NUM> continues to act <NUM>.

At act <NUM>, the BMS <NUM> controls the battery system <NUM> to be in the first shelf mode of operation. In the first shelf mode of operation, the BMS <NUM> controls the battery cell <NUM> to discontinue discharging power to the output <NUM>. Additionally, functionality of the BMS <NUM> may be disabled. For example, communication functionality of the BMS <NUM> may be disabled, such as wireless-communication functionality. In another example, housekeeping functionality of the BMS <NUM> may be disabled in addition to, or in lieu of, communication functionality.

Disabling functionality of the BMS <NUM> advantageously reduces a power consumption of the battery system <NUM>. Accordingly, the first shelf mode of operational may be referred to herein as an example of a battery-optimization mode of operation. However, if a main power source becomes available to the battery system <NUM> at the input <NUM>, as discussed below, the BMS <NUM> may be able to re-enable the disabled functionality quickly. Performance of the battery system <NUM> is therefore not significantly adversely impacted by the first shelf mode, which may improve a user experience by eliminating perceived slowness of a response of the battery system <NUM> when or if power is again available at the input <NUM>. A battery voltage of the battery system <NUM> may continue to decrease in the first shelf mode. The BMS <NUM> may control the battery system <NUM> to remain in the first shelf mode until a main power source is available, as discussed below, or until the battery voltage drops below a second discharge threshold.

At act <NUM>, the BMS <NUM> determines whether the voltage level of the battery cell <NUM> is below a second discharge threshold <NUM>. The second discharge threshold <NUM> may indicate a discharge threshold below which the battery system <NUM> will enter a mode of operation having a power consumption that is even lower than the first shelf mode, and may be referred to as a second shelf mode. As illustrated in the graph <NUM>, the second discharge threshold <NUM> is less than the first discharge threshold <NUM>. A time duration between entering the first shelf mode at the first discharge threshold <NUM> and entering the second shelf mode at the second discharge threshold <NUM> is referred to as a first shelf-mode duration <NUM>.

If the voltage level of the battery cell <NUM> is not below the second discharge threshold <NUM> (<NUM> NO), the process <NUM> returns to act <NUM>. Acts <NUM> and <NUM> are repeatedly executed and the voltage level of the battery cell <NUM> continues to decrease, as illustrated by the first voltage-level trace <NUM>. If a determination is made that the voltage level is below the second discharge threshold <NUM> (<NUM> YES), the process <NUM> continues to act <NUM>.

At act <NUM>, the BMS <NUM> controls the battery system <NUM> to be in a second shelf mode of operation. In the second shelf mode of operation, substantially all of the functionality of the BMS <NUM> may be disabled. The functionality of the BMS <NUM> that is disabled in the first shelf mode of operation may be disabled as well as additional functionality. For example, such additional functionality may include certain user-interface elements, such as a user-interface element used to power on the battery system <NUM>. Additional functionality may also include functionality to perform a cold boot of the battery system <NUM>, that is, starting up the battery system <NUM> from a fully powered-off state. Disabling additional functionality of the BMS <NUM> may further reduce a power consumption of the battery system <NUM> relative to the first shelf mode. Accordingly, the second shelf mode may also be referred to as a battery-optimization mode, such that "battery-optimization mode" may refer to either the first or second shelf mode. If a main power source becomes available to the battery system <NUM> at the input <NUM>, as discussed below, the BMS <NUM> may be able to re-enable the disabled functionality after a re-initiation period. A battery voltage of the battery system <NUM> may continue to decrease in the second shelf mode. The BMS <NUM> may control the battery system <NUM> to remain in the second shelf mode until a main power source is available, as discussed below, or until the battery voltage drops below a third discharge threshold.

At act <NUM>, the BMS <NUM> determines whether the voltage level of the battery cell <NUM> is below a third discharge threshold <NUM>. The third discharge threshold <NUM> may indicate a discharge threshold below which the battery system <NUM> is considered irrecoverable, and to have reached an end-of-life of the battery system <NUM>. As illustrated in the graph <NUM>, the third discharge threshold <NUM> is less than the second discharge threshold <NUM>. If the voltage level of the battery cell <NUM> is not below the third discharge threshold <NUM> (<NUM> NO), then the process <NUM> returns to act <NUM>. Acts <NUM> and <NUM> are repeatedly executed, and a voltage level of the battery cell <NUM> continues to decrease. If the voltage level of the battery cell <NUM> is below the third discharge threshold <NUM> (<NUM> YES), then the process <NUM> continues to act <NUM> and the battery system enters an irrecoverable state. A time between entering the second shelf mode at the second discharge threshold <NUM> and entering the irrecoverable state at the third discharge threshold <NUM> is referred to as a second shelf-mode duration <NUM>. A total time spent in the first shelf mode and the second shelf mode is a sum of the first shelf-mode duration <NUM> and the second shelf-mode duration <NUM>, and is referred to as a total shelf-mode duration <NUM>.

At act <NUM>, the battery system <NUM> is in an irrecoverable state. In the irrecoverable state, the battery system <NUM> may be considered inoperable and may no longer discharge power to a load. The battery system <NUM> may retain some functionality in the irrecoverable state, such as to output a notification to a user that the battery system <NUM> should be replaced. In other examples, the battery system <NUM> may disable all functionality indefinitely. The process <NUM> then ends at act <NUM>.

Although not illustrated in the process <NUM> for purposes of clarity, the BMS <NUM> may repeatedly (for example, periodically, aperiodically, or continuously) determine whether a load coupled to the output <NUM> regains access to an adequate main power source, such as utility power, throughout execution of the process <NUM>. The process <NUM> may terminate if the load regains access to the main power source, and the battery system <NUM> may transition from a discharge mode of operation to a charge mode of operation. The BMS <NUM> may control the battery system <NUM> to discontinue discharging power, and to recharge the battery cell <NUM> with power provided at the input <NUM> from the main power source that also powers the load coupled to the output <NUM>.

For example, if the BMS <NUM> is repeatedly executing acts <NUM> and <NUM> and thereby discharging the battery cell <NUM>, the BMS <NUM> may simultaneously be repeatedly determining whether access to mains power has been restored. If mains power is again available, the process <NUM> may be terminated. Similarly, if the BMS <NUM> is repeatedly executing acts <NUM> and <NUM> and thereby controlling the battery system <NUM> to be in the first shelf mode, the BMS <NUM> may simultaneously be repeatedly determining whether access to mains power has been restored. If mains power is again available, the process <NUM> may be terminated. Similarly, if the BMS <NUM> is repeatedly executing acts <NUM> and <NUM> and thereby controlling the battery system <NUM> to be in the second shelf mode, the BMS <NUM> may simultaneously be repeatedly determining whether access to mains power has been restored. If mains power is again available, the process <NUM> may be terminated.

Accordingly, while in the discharge mode of operation, the battery system <NUM> may enter various sub-modes of operation based on a voltage level of the battery cell <NUM>. These various sub-modes, such as the shelf modes, may extend a lifetime of the battery system <NUM> by consuming less power and thereby avoiding or mitigating harmful over-discharge conditions. The first discharge threshold <NUM> may be selected to balance a user's interest in increasing the total runtime <NUM>, which can be accomplished by decreasing the first discharge threshold <NUM>, with the user's interest in maximizing the total lifetime of the battery system <NUM>, which may be accomplished by increasing the first discharge threshold <NUM>.

In some conditions, it may be advantageous to selectively increase the first discharge threshold <NUM>. In various examples, the first discharge threshold <NUM> may be increased in certain abnormal operating conditions, such as operating conditions that substantially adversely impact a health of the battery system <NUM>. For example, abnormal operating conditions may include light-load conditions or low-state-of-charge conditions. In various examples, therefore, the battery system <NUM> may modify the first discharge threshold <NUM> based on one or more operational parameters.

<FIG> illustrates a process <NUM> of selecting a value of the first discharge threshold <NUM> according to an example. The process <NUM> may be executed at least in part by the BMS <NUM>. The process <NUM> is described with reference to <FIG>.

At act <NUM>, the BMS <NUM> receives one or more operational parameters. The one or more operational parameters may be indicative or descriptive of one or more operating conditions of the battery system <NUM>. For example, the one or more operational parameters may include current information, voltage information, charge information, and so forth, descriptive of the battery cell <NUM>, a load coupled to the output <NUM>, or other aspects of the battery system <NUM>. In some examples, the BMS <NUM> may receive charge information indicative of a current SOC of the battery cell <NUM> from the battery cell <NUM>, and/or from one or more sensing components in the battery system <NUM>. In various examples, the BMS <NUM> may additionally or alternatively receive load information indicative of an amount of power drawn by a load coupled to the output <NUM>. For example, the BMS <NUM> may receive load information from the load-detection circuit <NUM>. In some examples, the one or more operational parameters may include additional and/or different parameters.

At act <NUM>, the BMS <NUM> determines whether the one or more operational parameters are less than at least one operational-parameter threshold. For example, if the one or more operational parameters include charge information, the BMS <NUM> may determine whether a current SOC of the battery cell <NUM> is below a threshold SOC. The threshold SOC may be, for example, a certain proportion (for example, <NUM>%, <NUM>%, <NUM>%, and so forth) of an initial SOC of the battery cell <NUM>. The initial SOC may be an SOC of the battery cell <NUM> when the battery system <NUM> is first fully charged, or may be a rated initial SOC of the battery cell <NUM>, for example.

In another example, if the one or more operational parameters include load information, the BMS <NUM> may determine whether a current amount of power drawn by a load is below a threshold load. The threshold load may be, for example, a certain proportion (for example, <NUM>%, <NUM>%, <NUM>%, and so forth) of a rated load of the battery system <NUM>. The rated load may be a rated amount of power that the battery system <NUM> is configured to provide.

In some examples, the one or more operational parameters may include both charge information and load information, and the at least one operational-parameter threshold may include several operational-parameter thresholds, including a threshold SOC and a load threshold. In still other examples, the one or more operational parameters and/or at least one operational-parameter threshold may include or be based on other parameters in addition to, or in lieu of, a charge and/or load of the battery system <NUM>. Act <NUM> may include determining whether at least one of the one or more operational parameters are below the at least one operational-parameter threshold, or may include determining whether a different number (including, for example, all of the one or more operational parameters) of the one or more operational parameters are below the at least one operational-parameter threshold.

If the one or more operational parameters are not below the at least one operational-parameter threshold (<NUM> NO), then the process <NUM> returns to act <NUM>. Acts <NUM> and <NUM> may be repeated until a determination is made that at least one of the one or more operational parameters are below the at least one operational-parameter threshold (<NUM> YES). The process <NUM> then continues to act <NUM>.

At act <NUM>, the BMS <NUM> modifies the first discharge threshold <NUM>. For example, the BMS <NUM> may increase the first discharge threshold <NUM>. In some examples, the BMS <NUM> increases the first discharge threshold <NUM> by a specified amount (for example, <NUM>. 25V, <NUM>. 45V, and so forth). In other examples, the BMS <NUM> increases the first discharge threshold <NUM> by a variable amount which varies based on the one or more operational parameters. For example, the first discharge threshold <NUM> may be changed by an amount that varies (for example, increases) depending on the magnitude of a difference between the one or more operational parameters and the at least one operational-parameter threshold, such that the first discharge threshold <NUM> is increased more as the one or more operational parameters decrease.

As illustrated in <FIG>, a modified first discharge threshold <NUM> is implemented and is greater than the first discharge threshold <NUM>. The processes <NUM>, <NUM> may be executed in parallel such that the first discharge threshold <NUM> may be modified to the modified first discharge threshold <NUM> while the process <NUM> is being executed. Accordingly, if the first discharge threshold <NUM> is modified to the modified first discharge threshold <NUM>, act <NUM> may instead include determining whether a cell voltage is below the modified first discharge threshold <NUM>. By increasing the first discharge threshold <NUM> to the modified first discharge threshold <NUM>, the total runtime <NUM> may be reduced to a modified total runtime <NUM>, which refers to a duration of time between beginning to discharge the battery cell <NUM> from the fully charged voltage level <NUM> to reaching the modified first discharge threshold <NUM>.

Accordingly, the process <NUM> may be executed (for example, in parallel with the process <NUM>) to determine whether the first discharge threshold <NUM> should be modified to the modified first discharge threshold <NUM>. A second voltage-level trace <NUM> indicates a cell voltage of the battery system <NUM> over time where the modified first discharge threshold <NUM> is implemented. The second voltage-level trace <NUM> is similar to (for example, has a similar slope in corresponding modes of operation as) the first voltage-level trace <NUM>, but indicates a longer total lifetime at least in part because the modified first discharge threshold <NUM> is higher than the first discharge threshold <NUM>.

As indicated by the second voltage-level trace <NUM>, a change in cell voltage may vary based on a mode of operation of the battery system <NUM>. In some examples, the second discharge threshold <NUM> may be modified to yield a modified second discharge threshold <NUM>, and/or the third discharge threshold <NUM> may be modified to yield a modified third discharge threshold <NUM>. In various examples, however, the modified second discharge threshold <NUM> has an identical value as the second discharge threshold <NUM>, and/or the modified third discharge threshold <NUM> has an identical value as the third discharge threshold <NUM>. Accordingly, the thresholds <NUM>, <NUM> may be referred to as "modified" thresholds for purposes of explanation of the second voltage-level trace <NUM> in some examples.

A duration of time between the cell voltage dropping below the modified first discharge threshold <NUM> (which may be higher than the first discharge threshold <NUM>) and dropping below the modified second discharge threshold <NUM> (which may be identical to the second discharge threshold <NUM>) is referred to as a modified first shelf-mode duration <NUM>. A duration of time between the cell voltage dropping below the modified second discharge threshold <NUM> (which may be identical to the second discharge threshold <NUM>) and dropping below the modified third discharge threshold <NUM> (which may be identical to the third discharge threshold <NUM>) is referred to as a modified second shelf-mode duration <NUM>. A total time spent in the first shelf mode and the second shelf mode with the modified thresholds is a sum of the modified first shelf-mode duration <NUM> and the modified second shelf-mode duration <NUM>, and is referred to as a modified total shelf-mode duration <NUM>.

As indicated by the second voltage-level trace <NUM>, a total lifetime of the battery system <NUM> implementing at least the modified first discharge threshold <NUM> may be greater than a total lifetime of the battery system <NUM> implementing the first discharge threshold <NUM>, at least because the battery system <NUM> does not discharge power in abnormal conditions (for example, light load or low-state-of-charge conditions) for as long a duration because the threshold at which the battery system <NUM> enters a battery-optimization mode (for example, the first shelf mode) is increased.

Examples of modifying the first discharge threshold <NUM> are provided with respect to <FIG> and <FIG>. <FIG> illustrates a process <NUM> of determining whether to modify the first discharge threshold <NUM> according to one example. The process <NUM> may provide an example of the process <NUM>. The process <NUM> may be executed at least in part by the BMS <NUM>.

At act <NUM>, the BMS <NUM> receives operational parameters. The operational parameters may include, or may include information indicative of, a current SOC of the battery cell <NUM> and a current load on the battery system <NUM>.

At act <NUM>, the BMS <NUM> determines whether the battery cell <NUM> is sufficiently charged. Act <NUM> may include determining whether a current SOC of the battery cell <NUM> is below a threshold SOC, such as approximately <NUM>% of an initial SOC of the battery cell <NUM>. As used herein, "approximately <NUM>%" may include any of various examples including between <NUM>% and <NUM>%, between <NUM>% and <NUM>%, between <NUM>% and <NUM>%, between <NUM>% and <NUM>%, or other non-limiting examples. If the current SOC of the battery cell <NUM> is below the threshold SOC (for example, less than <NUM>% of the initial SOC), the battery cell <NUM> may be considered not sufficiently charged. If the battery cell <NUM> is not sufficiently charged (<NUM> NO), then the process <NUM> continues to act <NUM>.

At act <NUM>, the BMS <NUM> implements the modified first discharge threshold <NUM>. Implementing the modified first discharge threshold <NUM> may include modifying the first discharge threshold <NUM> or, if the modified first discharge threshold <NUM> was already in effect, maintaining the modified first discharge threshold <NUM>. The BMS <NUM> may implement the modified first discharge threshold <NUM> because the battery system <NUM> is not considered to be in normal use. The battery system <NUM> may be considered to not be in normal use because the SOC of the battery system <NUM> is low, and operating the battery system <NUM> in low SOC conditions may adversely impact a health of the battery system <NUM>. The process <NUM> returns to act <NUM>.

If the BMS <NUM> determines that the battery system <NUM> is sufficiently charged (<NUM> YES), such as if the current SOC of the battery cell <NUM> is above <NUM>% of the initial SOC of the battery cell <NUM>, then the process <NUM> continues to act <NUM>.

At act <NUM>, the BMS <NUM> implements the first discharge threshold <NUM>. Implementing the first discharge threshold <NUM> may include reverting the modified first discharge threshold <NUM> to the first discharge threshold <NUM> or, if the first discharge threshold <NUM> was already in effect, maintaining the first discharge threshold <NUM>. The BMS <NUM> may implement the first discharge threshold <NUM> because the battery system <NUM> is considered to be in normal use. The battery system <NUM> may be considered to be in normal use because the SOC of the battery system <NUM> is sufficiently high to be considered normal, and operating the battery system <NUM> in normal SOC conditions may not substantially impact a health of the battery system <NUM> compared to lower SOCs. The process <NUM> then continues to act <NUM>.

At act <NUM>, the BMS <NUM> determines whether the battery system <NUM> is lightly loaded. Act <NUM> may include determining whether a current load on the battery system <NUM> is below a threshold load, such as approximately <NUM>% of a rated load of the battery system <NUM>. As used herein, "approximately <NUM>%" may include any of various examples including between <NUM>% and <NUM>%, between <NUM>% and <NUM>%, between <NUM>% and <NUM>%, between <NUM>% and <NUM>%, or other non-limiting examples. If the current load on the battery system <NUM> is below the threshold load (for example, less than <NUM>% of the rated load), the battery system <NUM> may be considered lightly loaded. If the battery system <NUM> is lightly loaded (<NUM> YES), then the process <NUM> may proceed to act <NUM>. In other examples, the process <NUM> may return to act <NUM>. If the battery system <NUM> is not lightly loaded (<NUM> NO), then the process <NUM> may return to act <NUM>.

<FIG> illustrates a process <NUM> of determining whether to modify the first discharge threshold <NUM> according to another example. The process <NUM> may provide an example of the process <NUM>. The process <NUM> may be executed at least in part by the BMS <NUM>. The process <NUM> may be similar to the process <NUM>, and similar acts are labeled accordingly.

Acts <NUM>-<NUM> are substantially similar or identical in the processes <NUM>, <NUM>. However, in the process <NUM>, act <NUM> proceeds to act <NUM> rather than returning to act <NUM>. At act <NUM>, the process <NUM> ends.

Act <NUM> is substantially similar or identical in the processes <NUM>, <NUM>. However, in the process <NUM>, if the battery system <NUM> is not sufficiently charged (<NUM> NO), the process <NUM> continues to act <NUM> rather than <NUM>.

Act <NUM> is substantially similar or identical in the processes <NUM>, <NUM>. If the battery system <NUM> is not lightly loaded (<NUM> NO), the process <NUM> still continues to act <NUM>. However, if the battery system <NUM> is lightly loaded (<NUM> YES), the process <NUM> continues to act <NUM> rather than act <NUM>.

At act <NUM>, the BMS <NUM> implements the modified first discharge threshold <NUM>. Act <NUM> may be substantially similar or identical to act <NUM>. The process <NUM> then continues to act <NUM>.

Still other modifications are within the scope of the disclosure. As discussed above with respect to the process <NUM>, the first discharge threshold <NUM> may be changed based on one or more operational parameters. In some examples, as discussed above with respect to act <NUM>, the first discharge threshold <NUM> may be increased responsive to determining that the one or more operational parameters are less than the at least one operational-parameter threshold.

In other examples, the first discharge threshold <NUM> may be changed (for example, increased or decreased) responsive to determining that the one or more operational parameters are greater than at least one operational-parameter threshold. For example, act <NUM> may include determining whether an operational parameter (for example, an ambient temperature) is greater than an operational-parameter threshold (for example, a threshold temperature) and, if so, the first discharge threshold <NUM> may be modified.

In some examples, multiple operational-parameter thresholds may be implemented, and a determination may be made as to whether a first group of operational parameters are greater than a first group of operational-parameter thresholds, and whether a second group of operational parameters are less than a second group of operational-parameter thresholds. Accordingly, examples of the disclosure are not limited to determining whether one or more operational parameters are less than at least one operational-parameter threshold.

Although certain examples of operational parameters and operational-parameter thresholds are provided, other examples are within the scope of the disclosure. The one or more operational parameters may include any number of operational parameters, and the operational-parameter thresholds may include any number of operational-parameter thresholds. The operational parameters and corresponding thresholds are not limited to charge and load information. Accordingly, various modifications are within the scope of the disclosure.

Claim 1:
A method (<NUM>, <NUM>), in a battery system (<NUM>), the battery system comprising:
an output (<NUM>) configured to provide output power to a load;
one or more battery cells (<NUM>);
an input (<NUM>) configured to receive input power and to provide the input power to the one or more battery cells and to the output, wherein the one or more battery cells (<NUM>) are configured to store electrical energy to provide, via the output, output power to the load when acceptable input power is unavailable at the input; and
a battery management system (<NUM>);
the method comprising the steps of:
controlling the battery system to be in an active discharge mode responsive to determining that acceptable input power is unavailable at the input and a discharge level of the one or more battery cells is above a discharge threshold, wherein in the active discharge mode the one or more battery cells provide the output power to the load and the battery management system is fully functional;
receiving (<NUM>) one or more operational parameters of the battery system while the battery system is in the active discharge mode, the one or more operational parameters including a state of charge of the one or more battery cells and an amount of power drawn by the load from the one or more battery cells; and
while a cell voltage of the one or more battery cells is decreasing due to the provision of the output power to the load:
determining (<NUM>) whether the state of charge is less or greater than a threshold state of charge,
responsive to determining that the state of charge is greater than the threshold state of charge, determining (<NUM>) whether the amount of power drawn by the load is less than a threshold load,
increasing (<NUM>, <NUM>) the discharge threshold of the one or more battery cells responsive to determining that the state of charge is less than the threshold state of charge or the amount of power drawn by the load is less than the threshold load, and
controlling the battery system to move to a battery-optimization mode responsive to determining that the discharge level of the one or more battery cells falls below the discharge threshold, wherein in the battery-optimization mode the one or more battery cells cease to provide the output power to the load and the battery management system is partially functional by maintaining at least a boot functionality to start up the battery system when acceptable input power returns to being available at the input.