BATTERY

BACKGROUND

[0001] More and more energy systems are at least partially powered by batteries comprising one or more cells. For example, renewable power systems such as those using solar power may store accumulated charge in one or more batteries for subsequent use. An electric vehicle may also be primarily powered by batteries.

[0002] Rechargeable batteries degrade over time. For example, the more charge/discharge cycles to which a rechargeable battery has been subjected, the more degraded the battery becomes. For example, a battery which is new is capable of storing more electric charge than a battery which has been cycled 2000 times.

[0003] In some electrical systems, a battery may be taken offline and individual packs of the battery may be tested to determine a remaining usable life. However, such a process results in downtime as the battery is not usable while it is offline.

[0004] In other systems, a battery may be replaced after a set length of time. For example, in some systems, a battery may be replaced every three years. However, by replacing a battery at fixed intervals, certain inefficiencies may be encountered. For example, if a battery has been cycled heavily throughout the three-year period of time, the battery may be more degraded than a similar battery which has only been cycled lightly and/or which has been sparingly used, such as a rechargeable battery in an electric vehicle which has only been driven rarely as opposed to an electric vehicle which has been driven for several hours every day. Accordingly, by replacing a battery at fixed intervals, some batteries may be replaced which may potentially have several additional years of usable life. Other batteries, on the other hand, which have been used heavily, may have a usable life shorter than three years and waiting three years to replace such a battery may result in battery failure which leads to downtime, for example. Moreover, certain operating conditions may also affect battery life, such as ambient temperature in which the rechargeable battery is operated or stored. For example, battery life may degrade more quickly if the battery is utilized or stored in a relatively warm environment. SUMMARY

[0005] According to an aspect of an example embodiment, a method may include measuring current supplied to or withdrawn from a battery while a charge or discharge voltage of the battery is held constant at respective charge or discharge voltage limits. A baseline critical state of charge (SOC) of the battery during a first charge or discharge cycle of the battery may be determined, where the baseline critical SOC of the battery comprises an estimate of the SOC of the battery when a rate of change of the current supplied to or withdrawn from the battery at the constant voltage is approximately equal to a threshold value. A subsequent critical SOC estimate of the battery may be determined during a subsequent charge or discharge cycle of the battery, where the subsequent critical SOC estimate comprises an estimate of the SOC of the battery when a rate of change of the current supplied to or withdrawn from the battery at the constant voltage during the subsequent charge cycle is approximately equal to the threshold value. A state of health (SOH) of the battery may be determined based on a comparison between the baseline critical SOC and the subsequent critical SOC estimate. This process may be repeated until a target SOH has been met.

[0006] According to an aspect of another example embodiment, a system may include one or more sensors to measure current supplied to or withdrawn from a battery while a charge or discharge voltage of the battery is held constant at respective charge or discharge voltage limits. A memory may store a baseline critical SOC of the battery, where the baseline critical SOC of the battery comprises an estimate of the SOC of the battery when a rate of change of the current supplied to or withdrawn from the battery at the constant voltage is approximately equal to a threshold value. The processor may also determine a subsequent critical SOC estimate of the battery during a subsequent charge or discharge cycle of the battery, where the subsequent critical SOC estimate comprises an estimate of the SOC of the battery when a rate of change of the current supplied to or withdrawn from the battery at the constant voltage during the subsequent charge or discharge cycle is approximately equal to the threshold value. The processor may further determine an SOH of the battery based on a comparison between the baseline critical SOC and the subsequent critical SOC estimate. This process may be repeated until a target SOH has been met.

[0007] According to an aspect of another example embodiment, an article may comprise a non- transitory storage medium comprising machine-readable instructions executable by one or more processors to perform one or more operations. For example, the one or more processors may measure current supplied to or withdrawn from a battery while a charge or discharge voltage of the battery is held constant at respective charge or discharge voltage limits. The one or more processors may determine a baseline critical SOC of the battery during a first charge or discharge cycle of the battery, where the baseline critical SOC of the battery comprises an estimate of the SOC of the battery when a rate of change of the current supplied to or withdrawn from the battery at the constant voltage is approximately equal to a threshold value. The one or more processors may also determine a subsequent critical SOC estimate of the battery during a subsequent charge or discharge cycle of the battery, where the subsequent critical SOC estimate comprises an estimate of the SOC of the battery when a rate of change of the current supplied to or withdrawn from the battery at the constant voltage during the subsequent charge or discharge cycle is approximately equal to the threshold value. The one or more processors may further determine an SOH of the battery based on a comparison between the baseline critical SOC and the subsequent critical SOC estimate. This process may be repeated until a target SOH has been met.

[0008] Other features and aspects may be apparent from the following detailed description taken in conjunction with the drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Features and advantages of the example embodiments, and the manner in which the same are accomplished, will become more readily apparent with reference to the following detailed description taken in conjunction with the accompanying drawings.

[0010] FIGS. 1 A and IB illustrate charts of voltage and current profiles, respectively, during a charging phase for a battery according to an embodiment.

[0011] FIG. 2A illustrates a chart showing various charging profiles for a first battery which exhibits a relatively small amount of battery degradation over time according to an embodiment.

[0012] FIG. 2B illustrates a chart showing various charging profiles for a second battery which exhibits a relatively large amount of battery degradation over time according to an embodiment. [0013] FIG. 2C illustrates a chart showing various discharge profiles for a fresh battery and a discharge profile for an aged battery according to an embodiment.

[0014] FIG. 3 is an embodiment of a flowchart for determining a SOH during a charging operation of a battery system comprising one or more batteries according to an embodiment.

[0015] FIG. 4 is an embodiment of a flowchart for determining a SOH during a discharging operation of a battery system comprising one or more batteries according to an embodiment.

[0016] FIG. 5 illustrates an embodiment of a battery monitoring device to determine a SOH estimate for a battery system.

[0017] Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated or adjusted for clarity, illustration, and/or convenience.

DETAILED DESCRIPTION

[0018] In the following description, specific details are set forth in order to provide a thorough understanding of the various example embodiments. It should be appreciated that various modifications to the embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the disclosure. Moreover, in the following description, numerous details are set forth for the purpose of explanation. However, one of ordinary skill in the art should understand that embodiments may be practiced without the use of these specific details. In other instances, well-known structures and processes are not shown or described in order not to obscure the description with unnecessary detail. Thus, the present disclosure is not intended to be limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and features disclosed herein.

[0019] One or more example embodiments as discussed herein are directed to a method, system, and/or apparatus for determining a State of Health (SOH) of a battery comprising one or more cells. A“State of Health” or“SOH,” as used herein, refers to a condition of a battery, cell, or plurality of batteries, relative to a baseline comparison. Units of SOH of a battery may be expressed in terms of percentage points, such as where a SOH of 100% indicates that the battery’s health matches the battery’s baseline or initial health, for example. A battery’s SOH may initially be 100% of the baseline conditions during a first charge cycle and may decrease over time and use, for example.

[0020] A“state of charge” or“SOC,” as used herein refers to the battery charge status, such as in Ampere hours and may be expressed as a percentage of its rated capacity. A“true” SOC, as used herein, refers to an SOC value which indicates a reliable and/or accurate measurement of SOC for a battery. An ampere hour, abbreviated as“Ah,” comprises an amount of energy charge in a battery that will allow one ampere of current to flow for one hour, for example.

[0021] An estimate of a SOH of the battery may be determined based, at least partially, on how the true SOC for the battery changes after being repeatedly charged through various charge cycles. A“charge cycle” or“battery cycle,” as used herein, refers to a process of charging one or more rechargeable batteries and discharging stored charge into a load. A battery cycle may be utilized to estimate a battery’s expected life, as the number of battery cycles may potentially adversely affect the battery’s life more than the mere passage of time. Discharging a battery fully or down to very low true states-of-charge (true SOCs) before recharging may be referred to as “deep discharge,” whereas partially discharging (e.g., such as to 70-80% of true SOC) and then recharging the battery may be referred to as a“shallow discharge.”

[0022] Knowing an accurate estimate of a SOH of a battery may be of critical importance to overall performance of an electrical system utilizing the battery. For example, if a battery has a relatively low estimated SOH, an alert or some other type of notification may be generated to indicate that the battery has a relatively low estimated SOH and may need to be replaced with a new or different battery. For example, if a battery with a low estimated SOH is utilized in an electric vehicle, a message may be displayed on a dashboard of the electric vehicle to alert a driver of the electric vehicle so that the driver knows that the battery needs to be replaced. In an embodiment, an electronic message, such as an email or text message may be generated and transmitted to notify a user of a low estimated SOH, for example. Another example of an alert may relate to batteries in remote or hard-to-access areas, such as remote wind turbines or solar farms, where an advance alert may significantly improve planning and/or reduce cost of maintenance. [0023] If a reliable estimate of a SOH is unknown, a battery may continue to be utilized even though the battery may be at or near the end of its useful life. In some systems, a battery may be proactively replaced at fixed time intervals even if a reliable SOH is unknown for the battery. Such a process, however, may result in replacement of a battery which may still have a relatively long useful life remaining. Such a process may also result in use of a battery which is at or near expiration of its useful life. If a battery is still in use when it reaches the end of its useful life, an entire electrical system may be adversely affected, which may result in a power outage and/or down time for the electrical system. For example, if a rechargeable battery in an electric vehicle fails because the SOH of the battery was unknown and the battery was still in use, the electric vehicle may be disabled and a driver of the electric vehicle may be inconvenienced by having to wait in a potentially unfamiliar or dangerous location, such as on the shoulder of a busy highway, until a tow truck comes to tow the electric vehicle to a repair shop where a replacement battery may be installed into the electric vehicle. Such downtime to an electrical system may result in potentially large expenses to the owner of the electric vehicle, for example. Moreover, if a rechargeable battery provides power for a building or one or more pieces of machinery, for example, battery failure may result in inconveniences and/or loss of use of the building or machinery until a replacement battery is installed.

[0024] A true SOC of a battery may be periodically or continuously determined or measured, for example to maintain an ongoing measurement of charge of a battery during charging,

discharging, and while a battery remains idle, where the battery is neither charging nor discharging. There are numerous ways to determine a true SOC of a battery, such as via a Coulomb-counting method, for example.

[0025] Various profiles of charging characteristics may be predefined or otherwise known for different battery chemistries. For example, if a battery is charging at a constant voltage, the battery may exhibit certain characteristics. For example, if the battery is charging at a constant voltage, the amount of current flowing into the battery to charge the battery may decrease at a particular rate, as discussed in more detail with respect to FIGS. 1 A-B and 2A-B below. For example, there may be a predefined current charging profile for a particular battery which shows a relationship such as a mapping between the value of the rate of change of the charging current and a true SOC for the battery. In one particular embodiment, the current charging profile may be stored as a plot of points on a graph and/or as a lookup table such that if the value of the rate of change of the charging current which at a constant charging voltage is measured, a value of a true SOC for the battery may be determined.

[0026] A charging profile for a battery may shift or drift over time as the battery loses some of its ability to stored electric power. For example, a brand-new battery may be able to store 100% of electric energy according to a baseline comparison, such as the battery’s manufacturing specifications, but over time the battery may degrade. Accordingly, after 300 charge cycles and/or several months of use, the battery may only be able to achieve storage of 90% of the electric energy according to its baseline conditions. In other words, if a new battery has a SOH of 100%, the same battery after 300 cycles and/or several months of use may only have a SOH of 90% in this example.

[0027] It should be appreciated that the SOH of a battery is beneficial to determine because a battery is an item of capital-intensive equipment. Therefore, it is beneficial to optimize or otherwise extend the life of a battery so as to minimize the levelized cost of electricity (LCOE) of an electrical system. For example, in a rural electrification program with a solar, diesel generator, and a battery hybrid, it would be beneficial to monitor the health of the assets to optimally operate the system. An embodiment as discussed herein provides a mechanism for tracking the health of a battery in real-time based on continuous current and terminal voltage measurements, for example. An embodiment may provide real-time tracking of the SOH of the battery with just 2 sensors, e.g., sensors for terminal voltage and current.

[0028] Filtering techniques, such as application of a Kalman filter, and/or measurement averaging, such as across a selected range of charge cycles, may be applied to reduce sensor and/or process-related noise from measurements of rate of change of current. For example, in order to get an improved signal-to-noise ration of a sensor measurement of charging current, such as in order to estimate or determine a value of a rate of change of charging current, such as discussed below with respect to FIG. 2A, for example, filtering techniques may be applied. Use of such filtering techniques may therefore reduce and/or eliminate issues with data noise and/or disturbances which may adversely impact an accuracy of a method for determining a health of a battery.

[0029] In accordance with an embodiment, during a charge cycle or phase of a battery, a battery may be charged with electric power at an initial current level until an estimated true SOC of the battery reaches a particular threshold value. FIGS. 1 A and IB illustrate embodiments 100 and 105 of charts of voltage and current profiles, respectively, during a charging phase for a battery according to an embodiment. Embodiments 100 and 105 illustrate charts which show that a charging operation for a battery is initiated at around 5.0 hours and continues until around 16.0 hours. During the charging operation, values of the charging voltage and charging current supplied to the battery being charged are shown in the charts of embodiments 100 and 105. For example, as illustrated in the chart of embodiment 100, when charging is initiated, the charging voltage supplied during the charging operation is between 2.20 and 2.25 Volts and increases approximately linearly until the voltage reaches a value of approximately 2.30 Volts at approximately 10.25 hours. As time elapses between 10.25 hours and 16.0 hours, the charging voltage applied to the battery is held constant at about 2.30 Volts.

[0030] During the charging operation, a charging current supplied to a battery is initially approximately 50.0 Amps and remains approximately constant at about 50.0 Amps until the time elapsed reaches approximately 10.25 hours, as shown in the chart of embodiment 105. As the charging process continues between 10.25 hours through 16.0 hours, the value of the charging current supplied to the battery decreases from 50 Amps to approximately 9.0 Amps at 16.0 hours as is illustrated in the chart of embodiment 105. As shown, the value of the charging current supplied to the battery during the charging operation may decrease at an exponential rate, although the rate of change of the charging current supplied to the battery may decrease by a different rate in certain embodiments, for example.

[0031] As shown in charts of embodiments 100 and 105 of FIGS 1A and IB, respectively, during a charging process a charging current supplied is initially approximately constant while a charging voltage supplied increases. However, once the charging voltage supplied reaches a particular threshold value, the amount of charging current supplied begins to decrease, such as at 10.25 hours as is illustrated.

[0032] The charging voltage and charging current profiles shown in charts of embodiments 100 and 105 may remain approximately constant for batteries of the same chemistry, for example. In other words, two different lithium ion batteries, for example may be associated with the same baseline charging voltage and baseline charging current profiles. Information shown in these profiles may be utilized in accordance with an embodiment as discussed herein to approximate a SOH of a battery. For example, a baseline charging profile is determined for a battery during an initial charge cycle, subsequent charging profiles may be determined for the same battery during subsequent charge cycles and a SOH of the battery may be determined based, in part, on a comparison between the baseline charge cycle and the subsequent charge cycle. For example, the shape of the charge cycle for subsequent charge cycles may shift relative to the baseline charge cycle, indicating that the battery’s SOH has degraded.

[0033] A true SOC may be measured or otherwise determined for a battery during a portion of a charge cycle. For example, as shown in the chart of embodiment 105, a rate of change of the charging current may continually decay during a portion of the charging current profile while the voltage is at an approximately constant value between about 10.25 hours and 16.0 hours. For example, a reason why the rate of charging current changes while the voltage remains at a constant charging voltage value during a charging process is because a cell or charge resistance increases fairly significantly with a true SOC during a constant voltage charging phase, which may typically occur at the higher end of the true SOC scale, such as above a true SOC of about 70%.

[0034] A charging current profile may be determined for a type of battery, such as a lithium ion or lead acid battery, to name just two types of batteries among many. The charging current profile may indicate a relationship between a true SOC of the battery and a rate of change of the charging current flowing into a battery during a charging operation. For example, the slope of the plot of the charging current as shown in FIG. IB where the plot exhibits an exponential decay may have a slope which continually changes while at constant voltage until the charging operation ends. In an embodiment as shown in FIG. IB, the slope or rate of change of the charging current may continually decrease between a time at which a battery initially provides charging current at constant voltage as the battery is charged until the charging operation ends.

A relationship between a value of a rate of change of the charging current supplied during the charging operation and a true SOC for the battery may be determined. In one embodiment, a Coulomb-counting method may be utilized to determine a value of a true SOC for a battery and measurements of the rate of change of current relative to a true SOC while a constant voltage level or value is provided to the battery may be recorded or stored and thereafter utilized to determine a charging current profile for a battery. An accuracy of an SOH estimate may be dependent upon an accuracy of the true SOC estimate. [0035] In one particular implementation, a charging profile comprising a plot of a rate of change of a charging current relative to a true SOC may be determined for a battery during an initial, such as the first, charge cycle for the battery. The charging profile for the initial charge cycle of the battery may be referred to herein as a“baseline charge cycle profile.” Subsequent charging profiles may be determined for the battery during subsequent charge cycles for the battery. As a battery degrades over time, the charging profile for a battery may shift, for example, which may indicate that the SOH of the battery has decreased.

[0036] FIG. 2A illustrates a chart 200 showing various charging profiles for a first battery which exhibits a relatively small amount of battery degradation over time according to an embodiment. In this embodiment, for example, two different charging profiles are shown, e.g., a first charging profile 205 for an initial charge cycle of the first battery and a second charging profile 210 for the a later charge cycle of the first battery after a certain length of time, such as after nine months of use. Each of these charging profiles indicates a relationship between a rate of change of charging current while at a constant charging voltage relative to a true SOC to indicate how fully charged the first battery is, with a measurement of the true SOC of 100% indicating that the battery is fully charged relative to the battery’s specifications. A rate of change of charging current is denoted as“iDof’ in terms of Amperes per second, or A/s, in FIG. 2A, for example. FIG. 2A illustrates iDot between 0.00 and -0.045 A/s and corresponding true SOC values between 60% and 100%. Chart 200 illustrates charging profiles which may be determined from actual measurements of iDot and of true SOC for the first battery.

[0037] A SOH of the first battery may be estimated or otherwise determined over time based on a comparison between first charging profile 205 and subsequently determined charging profiles, such as second charging profile 210. As the first battery degrades over time, such as after being subjected to numerous charge cycles during a subsequent period of time, for example, subsequent charging profiles for the first profile may shift to the left in chart 200, for example.

In the embodiment shown in chart 200, there has been relatively little battery degradation in the first battery between the first charging profile 205 and the subsequent charging profile after nine months of use, as illustrated by the relatively small differences between first charging profile 205 and second charging profile 210. For example, the first charging profile 205 and second charging profile 210 are relatively similar between true SOC values of between 60% and 90% and primarily diverge at true SOC values above the low 90% values, as shown in chart 200. [0038] FIG. 2B illustrates a chart 250 showing various charging profiles for a second battery which exhibits a relatively large amount of battery degradation over time according to an embodiment. As shown by a comparison of chart 200 in FIG. 2A versus chart 250 of FIG. 2B, the second battery exhibits more degradation over nine months of time than does the first battery. In this embodiment, for example, a first charging profile 255 is shown for the second battery during its initial charge cycle along with a charging profile 260 for a charge cycle of the second battery after a certain length of time as elapsed, such as nine months of usage. Each of the charging profiles indicates a relationship between a measurement of iDot while at a constant charging voltage relative to a true SOC to indicate how fully charged the battery is, with a measurement of the true SOC of 100% indicating that the battery is fully charged relative to the battery’s specifications. As shown, during the initial charge cycle of the second battery, the true SOC reaches a value of about 106%, indicating an overcharged condition where the second battery is charged beyond the battery’s specifications as shown in first charging profile 255. However, in this example, the second battery has degraded substantially between the initial charge cycle and a subsequent charge cycle measured after nine months of usage. For example, as illustrated, the first charging profile 255 and the subsequent charging profile 260 for the aged battery after nine months of usage start to diverge at around 76% of the measurement of true SOC as shown in chart 250. The profiles shown in chart 250 of FIG. 2B therefore differ from the profiles shown in chart 200 of FIG. 2 A. For example, as shown in chart 200 of FIG. 2 A, a first charging profile 205 and the subsequent charging profile 210 start to diverge at a higher value of the true SOC, such as at about 93% of the true SOC in chart 200, unlike the profiles shown in chart 250 of FIG. 2B.

[0039] For example, second battery of FIG. 2B may have been subjected to harsher operating conditions than first battery of FIG. 2 A and may therefore have degraded more quickly than the first battery. Accordingly, a SOH of second battery after a certain length of time, such as nine months of usage, may be lower than an SOH of the first battery would be after the same nine months of usage, for example.

[0040] A value of a true SOC at a particular threshold iDot may be utilized to determine a value of a critical SOC for a particular charge cycle. In FIG. 2B, an iDot of about -0.002 may correspond to a true SOC of approximately 91% during the initial charge cycle as shown in first charging profile 255. However, an SOH of the second battery may degrade relatively quickly such that the true SOC drops to approximately 81% during the a charge cycle performed after nine months at the same iDot value of about -0.002.

[0041] A value of a critical SOC may be determined for a battery. A“critical SOC” as used herein, comprises a true SOC value corresponding to a threshold iDot for a particular charging profile. In an embodiment as shown in FIG. 2B, a critical SOC may be determined for each different charging profile, where the value of the critical SOC for a particular charging profile comprises a value of a true SOC for a charging profile at a threshold iDot. If a threshold iDot such as -.002 is considered, in an embodiment in accordance with FIG. 2B, a first charging profile 255 may have a critical SOC of about 91%, and a second charging profile 260 during the second battery during the 270th charge cycle may have a critical SOC of about 81%, for example. A difference between a critical SOC of a baseline charging profile and a critical SOC for subsequent charge cycles may be utilized to determine a SOH of the battery. In the example shown in FIG. 2B, the first charging profile 255 may be considered a baseline charging profile.

In some embodiments, a baseline charging profile may comprise a charging profile determined for a battery during an initial charge cycle. Alternatively, a charging profile for a different charge cycle, such a charge cycle measured after six months of use, may be utilized as a baseline charging profile, for example. In one particular implementation, a difference between the critical SOC of a baseline charging profile and a critical SOC for subsequent charge cycles may be utilized to determine a SOH for a battery. For example, a value of a critical SOC for a particular charge cycle may be divided by the value of the critical SOC for the baseline profile. In an embodiment, the value of the critical SOC may continually decrease as the battery degrades. Accordingly, dividing a value of a critical SOC for a particular charge cycle by the value of the critical SOC for the baseline profile may result in a value of SOH which is 100% or lower, for example. In another embodiment, a value of a critical SOC may be subtracted from a value of the critical SOC for the baseline profile to determine a SOH for the battery. For example, a change or reduction in a true SOC during a charge cycle relative to the true SOC of first or baseline charge cycle may directly indicate an amount of lost battery capacity and, therefore, a SOH of the battery.

[0042] Table A as shown below indicates examples of measurements of critical SOC from various charge cycles relative to a critical SOC for a baseline charge cycle for a particular battery, for example. In this embodiment, a battery may be replaced if its SOH drops below 90%, such as for charge cycle 700, for example, as illustrated in Table A.

Table A - iDot vs. True SOC Lookup Table for a Batery

[0043] Embodiments as discussed above relate to determination of an SOH of a battery during a charge cycle at constant charge voltage at relatively high values of true SOC, such as within a range of approximately 60-100%. However, it should be appreciated that such teachings may also be applicable to determine an SOH of a battery during a discharge cycle at a constant discharge voltage at relatively low values of true SOC, such as within a range of approximately 0-30%, for example. A relatively rapid change in charge resistance at a relatively high value of true SOC during a charge cycle may result in a relatively large changes in iDot as true SOC increases, for example. In an analogous scenario, a relatively rapid change in a discharge resistance at a relatively low value of true SOC during a discharge cycle, may result in relatively large changes in iDot as true SOC decreases.

[0044] FIG. 2C illustrates a chart 270 showing a discharge profile 275 for a fresh battery and a discharge profile 280 for an aged battery according to an embodiment. As shown, discharge profile 275 indicates that the fresh battery is capable of being approximately fully discharged. Discharge profile 280 for the aged battery, on the other hand, indicates that the aged battery is not capable of being fully discharged and may only be discharged to a true SOC of

approximately 12%, for example.

[0045] FIG. 3 is an embodiment 300 of a flowchart for determining a SOH during a charging operation of a battery system comprising one or more batteries according to an embodiment. Embodiments in accordance with claimed subject matter may include all of, less than, or more than blocks 305 through 340. Also, the order of blocks 305 through 340 is merely an example order. A method in accordance with embodiment 300 may be performed in a manner which is in-situ, continuous, nonintrusive and/or online, for example. Accordingly, such a method may be performed while a battery performs a typical charging operation, for example.

[0046] First, at operation 305, a process to estimate a SOH of a battery system may be initiated. At operation 310, current supplied to the battery system while a voltage supplied to the battery system remains constant may be measured. At operation 315, a baseline critical SOC of the battery system may be determined during a first charge cycle of the battery system. For example, the baseline critical SOC of the battery system may comprise an estimate of the true SOC of the battery system when a rate of change of the current supplied to the battery system at the constant voltage is approximately equal to a threshold value. At operation 320, a subsequent critical SOC estimate of the battery system may be determined during a subsequent charge cycle of the battery system. For example, the subsequent critical SOC estimate may comprise an estimate of the true SOC of the battery system when a rate of change of the current supplied to the battery system at the constant voltage during the subsequent charge cycle is approximately equal to the threshold value. At operation 325, a SOH of the battery system may be determined based on a comparison between the baseline critical SOH and the subsequent critical SOC estimate. At operation 330, a determination may be made as to whether the SOH during the subsequent charge cycle equals a threshold SOH value. If“yes” at operation 330, processing may return to operation 320. If“no” at operation 330, processing may proceed to operation 335 where an alert may be generated to indicate that the SOH of the battery is below the threshold SOH value. At operation 340, the process may end, for example, and the current battery system may be removed and replaced with a different battery system having a better SOH value and the process 300 may be repeated.

[0047] FIG. 4 is an embodiment 400 of a flowchart for determining a SOH during a discharging operation of a battery system comprising one or more batteries according to an embodiment. Embodiments in accordance with claimed subject matter may include all of, less than, or more than blocks 405 through 440. Also, the order of blocks 405 through 440 is merely an example order. A method in accordance with embodiment 400 may be performed in a manner which is in situ, continuous, nonintrusive and/or online, for example. Accordingly, such a method may be performed while a battery performs a typical discharging operation, for example. [0048] First, at operation 405, a process to estimate a SOH of a battery system may be initiated. At operation 410, current withdrawn from the battery system, while a voltage supplied by the battery system remains constant, may be measured. At operation 415, a baseline critical SOC of the battery system may be determined during a first discharge cycle of the battery system. For example, the baseline critical SOC of the battery system may comprise an estimate of the true SOC of the battery system when a rate of change of the current withdrawn from the battery system at the constant voltage is approximately equal to a threshold value. At operation 420, a subsequent critical SOC estimate of the battery system may be determined during a subsequent discharge cycle of the battery system. For example, the subsequent critical SOC estimate may comprise an estimate of the true SOC of the battery system when a rate of discharge of the current withdrawn from the battery system at the constant voltage during the subsequent discharge cycle is approximately equal to the threshold value. At operation 425, a SOH of the battery system may be determined based on a comparison between the baseline critical SOH and the subsequent critical SOC estimate. At operation 430, a determination may be made as to whether the SOH during the subsequent discharge cycle equals a threshold SOH value. If“yes” at operation 430, processing may return to operation 420. If“no” at operation 430, processing may proceed to operation 435 where an alert may be generated to indicate that the SOH of the battery is below the threshold SOH value. At operation 440, the process may end, for example, and the current battery system may be removed and replaced with a different battery system having a better SOH value and the process 400 may be repeated.

[0049] FIG. 5 illustrates an embodiment 500 of a battery monitoring device 505 to determine a SOH estimate for a battery system 510. Battery system 510 may comprise one or more batteries, where each of the one or more batteries comprises one or more cells, for example. Battery monitoring device 505 may include various components, for example, such as one or more sensor(s) 515, a processor 520, a memory 525, a communication device 530, and an Input/Output (I/O) interface 535. Sensor(s) 515 may comprise one or more sensors in communication with battery system 510 to monitor and/or measure an amount of current flowing into and/or out of battery system 510 over a period of time, for example. Processor 520 may obtain a measurement of current flowing into and/or out of battery system 510 and may determine a rate of change of the current, for example. Memory 525 may store a baseline critical SOC for an initial charge cycle of battery system 510 and one or more subsequently determined values of a critical SOC for subsequent charge cycles of battery system 510, such as discussed above with respect to FIGS. 2A-B and 3, for example. Processor 520 may determine a SOH for battery system 510 based on a comparison of the baseline critical SOC and subsequently determined values of a critical SOH for subsequent charge cycles, for example. Communication device 530 may transmit a message such as via a network, for example, to indicate a SOH for the battery system 510, such as by transmitting the message via I/O interface 535.

[0050] As will be appreciated based on the foregoing specification, one or more aspects of the above-described examples of the disclosure may be implemented using computer programming or engineering techniques including computer software, firmware, hardware or any combination or subset thereof. Any such resulting program, having computer-readable code, may be embodied or provided within one or more non-transitory computer readable media, thereby making a computer program product, i.e., an article of manufacture, according to the discussed examples of the disclosure. For example, the non-transitory computer-readable media may be, but is not limited to, a fixed drive, diskette, optical disk, magnetic tape, flash memory, semiconductor memory such as read-only memory (ROM), and/or any transmitting/receiving medium such as the Internet, cloud storage, the internet of things, or other communication network or link. The article of manufacture containing the computer code may be made and/or used by executing the code directly from one medium, by copying the code from one medium to another medium, or by transmitting the code over a network.

[0051] The computer programs (also referred to as programs, software, software applications, “apps”, or code) may include machine instructions for a programmable processor and may be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the terms“machine-readable medium” and “computer-readable medium” refer to any computer program product, apparatus, cloud storage, internet of things, and/or device ( e.g ., magnetic discs, optical disks, memory, programmable logic devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The“machine-readable medium” and“computer-readable medium,” however, do not include transitory signals. The term“machine-readable signal” refers to any signal that may be used to provide machine instructions and/or any other kind of data to a programmable processor. [0052] The above descriptions and illustrations of processes herein should not be considered to imply a fixed order for performing the process steps. Rather, the process steps may be performed in any order that is practicable, including simultaneous performance of at least some steps. Although the disclosure has been described in connection with specific examples, it should be understood that various changes, substitutions, and alterations apparent to those skilled in the art can be made to the disclosed embodiments without departing from the spirit and scope of the disclosure as set forth in the appended claims.

[0053] Some portions of the detailed description are presented herein in terms of algorithms or symbolic representations of operations on binary digital signals stored within a memory of a specific apparatus or special purpose computing device or platform. In the context of this particular specification, the term specific apparatus or the like includes a general-purpose computer once it is programmed to perform particular functions pursuant to instructions from program software. Algorithmic descriptions or symbolic representations are examples of techniques used by those of ordinary skill in the signal processing or related arts to convey the substance of their work to others skilled in the art. An algorithm is here, and generally, considered to be a self-consistent sequence of operations or similar signal processing leading to a desired result. In this context, operations or processing involve physical manipulation of physical quantities. Typically, although not necessarily, such quantities may take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared or otherwise manipulated.

[0054] It has proven convenient at times, principally for reasons of common usage, to refer to such signals as bits, data, values, elements, symbols, characters, terms, numbers, numerals or the like. It should be understood, however, that all of these or similar terms are to be associated with appropriate physical quantities and are merely convenient labels. Unless specifically stated otherwise, as apparent from the following discussion, it is appreciated that throughout this specification discussions utilizing terms such as "processing," "computing," "calculating," "determining" or the like refer to actions or processes of a specific apparatus, such as a special purpose computer or a similar special purpose electronic computing device. In the context of this specification, therefore, a special purpose computer or a similar special purpose electronic computing device is capable of manipulating or transforming signals, typically represented as physical electronic or magnetic quantities within memories, registers, or other information storage devices, transmission devices, or display devices of the special purpose computer or similar special purpose electronic computing device.

[0055] It should be understood that for ease of description, a network device (also referred to as a networking device) may be embodied and/or described in terms of a computing device.

However, it should further be understood that this description should in no way be construed that claimed subject matter is limited to one embodiment, such as a computing device and/or a network device, and, instead, may be embodied as a variety of devices or combinations thereof, including, for example, one or more illustrative examples.

[0056] The terms,“and”,“or”,“and/or” and/or similar terms, as used herein, include a variety of meanings that also are expected to depend at least in part upon the particular context in which such terms are used. Typically,“or” if used to associate a list, such as A, B or C, is intended to mean A, B, and C, here used in the inclusive sense, as well as A, B or C, here used in the exclusive sense. In addition, the term“one or more” and/or similar terms is used to describe any feature, structure, and/or characteristic in the singular and/or is also used to describe a plurality and/or some other combination of features, structures and/or characteristics. Likewise, the term “based on” and/or similar terms are understood as not necessarily intending to convey an exclusive set of factors, but to allow for existence of additional factors not necessarily expressly described. Of course, for all of the foregoing, particular context of description and/or usage provides helpful guidance regarding inferences to be drawn. It should be noted that the following description merely provides one or more illustrative examples and claimed subject matter is not limited to these one or more illustrative examples; however, again, particular context of description and/or usage provides helpful guidance regarding inferences to be drawn.

[0057] While certain exemplary techniques have been described and shown herein using various methods and systems, it should be understood by those skilled in the art that various other modifications may be made, and equivalents may be substituted, without departing from claimed subject matter. Additionally, many modifications may be made to adapt a particular situation to the teachings of claimed subject matter without departing from the central concept described herein. Therefore, it is intended that claimed subject matter not be limited to the particular examples disclosed, but that such claimed subject matter may also include all implementations falling within the scope of the appended claims, and equivalents thereof.