Battery module and method having state of health determination - Patents.com

Abstract

The battery module includes a battery unit that receives input power from an external power source. In the absence of the input power, the battery unit provides power to a load. The battery module includes a control unit that executes a charging cycle, when the input power is present, including charging the battery unit with the input power to a first predetermined level. The charging cycle also includes disconnecting the battery unit from the input power when the first predetermined level is reached. The charging cycle also includes discharging the battery unit to a second predetermined level, determining a time to discharge the battery unit from the first predetermined level to the second predetermined level when the second predetermined level is reached, determining a state of health of the battery unit based on the determined discharge time, and reconnecting the battery unit to the input power to recharge the battery unit to the first predetermined level. The first and second predetermined levels define an interval that ensures backup functionality of the battery module throughout the charging cycle.

Description

[Technical field]

[0001] The present disclosure relates generally to the field of battery modules, and more particularly to monitoring the health of battery modules, especially battery modules including battery units that include lithium-ion based battery cells. [Background technology]

[0002] In many applications, batteries are used as a backup in case of power failure, for example in the form of an uninterruptible power supply. In areas with a stable power grid, such backup batteries may be used less than once a year. When the battery is not in use, its State of Health (SoH) and functionality are often unknown. Therefore, when a power outage occurs, the battery may not function as desired and the equipment it is powering may shut down. Furthermore, keeping lithium-ion battery cells at a constant high State of Charge (SoC) shortens the lifespan of the battery cells. Summary of the Invention

[0003] It is therefore an object of the present invention to overcome at least some of the above-mentioned drawbacks and to provide an improved battery module and an improved method for operating a battery unit.

[0004] This and other objects are achieved by the apparatus and method defined in the accompanying independent claims. Further embodiments are defined by the dependent claims.

[0005] According to a first aspect of the present disclosure, a battery module is provided, the battery module comprising a battery unit configured to receive input power from an external power source and to supply power to a load in the absence of the input power, the battery module further comprising a control unit configured to perform a charging cycle when the input power is available.

[0006] The charging cycle comprises charging the battery unit to a first predetermined level by using an external power source (drawing power from the external power source), i.e., by using an input power. The charging cycle further comprises disconnecting the battery unit from the input power upon reaching the first predetermined level. The charging cycle further comprises discharging the battery unit to a second predetermined level. Once the battery unit has discharged to the second predetermined level, the control unit is configured to determine a discharge time for the battery unit to reach the second predetermined level from the first predetermined level (i.e., a time to discharge from the first predetermined level to the second predetermined level). The control unit is further configured to determine a state of health (SoH) of the battery unit based on the determined discharge time. The charging cycle further comprises reconnecting the battery unit to the input power to recharge the battery unit to the first predetermined level. The first and second predetermined levels define an interval that ensures a backup function of the battery module throughout the charging cycle.

[0007] The battery module may be configured, for example, as part of an uninterruptible power supply for a load. In such a configuration, an external power source may be configured to provide input power to the battery module and to power the load. When the external power source is active, the load is powered and the battery units of the battery module may be charged in parallel. When the external power source cannot provide power, such as during a power outage, the battery unit loses input power and the load loses power. The battery module may then automatically supply power to the load so that the load continues to function.

[0008] Generally, it is desirable to extend the life of a battery module. In a battery module configured as a backup to power a load in the event of failure of a primary or external power source, it is also desirable for the battery module to have a high charge level (state of charge, SoC) when the primary power source fails. However, keeping lithium-ion based battery cells in a high state of charge can shorten the life of the battery cells.

[0009] In the present disclosure, a battery module is disclosed that can provide a high level of charging of the battery units in the event of a loss of input power, such as when an external power source fails, while simultaneously extending the life of the battery module. To this end, when input power is received by the battery module, the battery module is subjected to a charging cycle that includes periods during which the battery units of the battery module are discharged such that they are not constantly maintained at a maximum (or very high) charge level.

[0010] A charge cycle typically includes a period during which the battery unit is discharged from a high charge level to a low charge level, and a period during which the battery unit is charged (or recharged) from the low charge level to a high charge level. These periods may be repeated sequentially (i.e., discharge, charge, discharge, charge).

[0011] Additionally, the battery module may provide information regarding the health of the battery module when it is not being used to power a load.

[0012] The state of charge, i.e. the charge level, can be determined in different ways. For example, the state of charge can be determined by measuring the voltage of the battery unit and using a known curve (preferably a known discharge curve) that relates the voltage of the battery unit to its state of charge. In other words, the voltage measured at the battery unit is indicative of the state of charge of the battery unit.

[0013] In general, to determine the health of the battery unit, the state of charge of the battery unit may be measured before and after a known amount of energy needs to be delivered by the battery unit. The expected state of charge of the battery unit may then be compared to the measured state of charge of the battery unit after the known amount of energy has been delivered by the battery unit. For example, assuming the state of charge of the battery unit initially changes from 80% to 70% to deliver a constant amount of energy, if the state of charge of the battery unit later changes from 80% to 65%, the health of the battery unit will have decreased.

[0014] To measure the state of health of a battery unit, the battery unit may be discharged for a known time using a known load (thereby determining a known amount of energy delivered), after which the voltage (i.e., state of charge) of the battery unit is measured and compared to the expected voltage (i.e., anticipated state of charge) of the battery unit.

[0015] As a battery unit ages, a larger portion of the total stored energy is required to operate for a known period of time, and as a result, the voltage at the end of a (known) discharge period becomes lower and lower as the battery unit ages.

[0016] In an embodiment according to the first aspect, the same general principle applies in that the discharge time for the battery unit to reach a first predefined level to a second predefined level is determined. The first and second predefined levels are obtained by measuring the voltage level of the battery unit. If the discharge time from the first predefined level to the second predefined level is reduced between two measurements, this means that the health of the battery unit is deteriorating.

[0017] The battery unit may be discharged between a first predetermined level and a second predetermined level with a known load. The discharge time may be compared to a previous measurement to obtain the same discharge of the battery unit. A state of health may then be determined based on a comparison of the measured discharge time to an expected discharge time.

[0018] The state of charge is defined relative to the current state of health of the battery unit.

[0019] In other words, 100% SoC means that the battery unit is fully charged at its current capacity. For example, consider an (ideal) battery unit with an initial (beginning of life, BOL) capacity of 100Ah. At the beginning of life (tBOL), the battery unit is discharged from its full state of charge (SoC 100%) at a constant current of 1A for 10 hours, resulting in a remaining capacity of 90Ah (SoC 90%).

[0020] However, the SoH of a battery unit may degrade over time due to environmental conditions, power surges, general aging, etc. The SoH is a measure of the condition of a battery (e.g., a battery unit) compared to an ideal condition. The SoH may be related, at least in part, to the actual capacity of the battery unit compared to its initial (ideal) capacity.

[0021] Therefore, the SoH and the battery capacity are reduced at the time (t AGE ) repeating the same discharge procedure may yield different results.

[0022] If the total capacity of the aged battery units is 90 Ah, then due to aging, the fully charged state (100% SoC) corresponds to a capacity of 90 Ah.

[0023] When the battery unit is discharged at a constant current of 1A for 10 hours, the remaining capacity is 80Ah, which corresponds to 88% SoC. AGE So, 90% SoC corresponds to a remaining capacity of 81Ah. Therefore, t AGENow, using a constant current of 1A, a shorter discharge time, i.e. 9 hours, is required for the battery unit to reach a level of 90% SoC (i.e. 81Ah). The determined discharge time t d By comparing with an initial or previous value, the current capacity of the battery unit can be estimated.

[0024] Various methods of determining the state of health are available. The SoH may be calculated, for example, using aging data provided by the cell manufacturer. Alternatively, the actual capacity may be determined and compared to the initial capacity of the battery cell. Using both a value determined using aging data and a value determined based on a capacity comparison, a more accurate value may be arrived at.

[0025] The procedure for determining the state of health of the battery module is introduced as part of the charging cycle in that the state of health is determined based on the discharge time between a first predetermined level and a second predetermined level. Including the health determination as part of the charging cycle is beneficial in that it is less invasive than other methods that may require the battery module to perform a separate procedure and, in some cases, may require the battery module to be disconnected from the load, thereby losing its function as a backup during the procedure for determining the state of health of the battery module.

[0026] When the battery module receives input power, the control unit may be configured to continuously (or repeatedly) perform a charging cycle.

[0027] In the charging cycle, the battery unit is first charged to a first predetermined level of state of charge (SoC). The first predetermined level may be a high level that approaches 100%. Once the battery unit reaches the first level, the battery unit is disconnected from the input power. Once the battery unit is disconnected from the input power, the battery unit may begin to discharge.

[0028] The discharge of the battery unit may occur, for example, due to standby power consumption from the control unit (or controller, also called battery management system, BMS) of the battery module. In other words, the discharge of the battery unit may be due to power consumption from the units or internal components of the battery module.

[0029] As another alternative, a dedicated load or resistor may be provided to discharge the battery unit.

[0030] Once the battery unit has been discharged to a second predetermined lower level, the input power is reconnected and the battery unit is recharged to the first predetermined level.

[0031] The determination of the discharge time, and therefore the health, may be performed while the battery unit is being recharged. The use of charge / discharge cycles may extend the life of the battery unit since the battery is not maintained at maximum capacity for long periods of time.

[0032] Additionally, allowing the battery unit to self-discharge and / or discharging using an internal unit (component / equipment) may result in the battery unit discharging at a slow, steady and / or controlled rate.

[0033] Such a discharge rate allows for reliable measurement of the discharge time and leads to improved SoH estimates.

[0034] As mentioned above, combining the charging cycle with the SoH estimation is beneficial. In particular, it may provide that the SoH estimation can be performed repeatedly without interrupting the power supply to the load. If necessary, in principle the SoH can be determined every charging cycle. The frequency at which the SOH is estimated can naturally be set (i.e. every charging cycle or with a certain number of charging cycles between two estimations). When the SoH is determined continuously or iteratively, the evolution of the SoH can be monitored and maintenance planning can be facilitated. Thus, the risk of the battery unit not functioning when needed can be reduced.

[0035] According to some embodiments, the first predetermined level may be 95% or greater.

[0036] The battery unit may be initially allowed to be charged to a high level or to full capacity before discharging, so that discharging may begin from a high level. Thus, even if the battery unit is discharged during a charging cycle, it may still retain sufficient charge to power a load. As a result, the battery module may be in a suitable state to power a load at all times during a charging cycle. For example, the first predetermined level may correspond to the battery being fully charged, such as having a state of charge (SoC) of 100%.

[0037] According to some embodiments, the second predetermined level may be 70% or greater.

[0038] The second predetermined level may be selected to correspond to a shallow discharge of the battery unit, so that if the external power source fails when the battery unit discharges to the second predetermined level during a charging cycle, there will still be enough battery power remaining to power the load for some time. Thus, the second predetermined level may be selected based on the desired (or required) operating time of the battery module as a backup during a power failure of the external power source.

[0039] The second predetermined level may also be selected to be sufficiently low such that a reliable determination of the SoH of the battery unit, ie a reliable voltage measurement of the capacity of the battery unit, is achieved.

[0040] In other examples, the second predetermined level may be 80% or more, such as 90% or more.

[0041] According to some embodiments, the control unit is powered by a battery unit, and discharging the battery unit between the first and second predetermined levels may include discharging power from the battery unit to the control unit.

[0042] The power consumption of the control unit (or BMS) may be known, and the control unit drawing power from the battery unit may make the discharge of the battery unit more controlled and / or more predictable. Thus, state of health estimates may be improved.

[0043] According to some embodiments, the battery module may further comprise an adjustable load resistor, and the control unit may be further configured to discharge the battery module to the second determined level using the adjustable load resistor.

[0044] The adjustable load resistor may be adjusted to maintain the discharge rate to a predefined or desired interval, which may improve the SoH estimation. Alternatively or additionally, the battery module may further comprise a (non-adjustable) load resistor for use in discharging the battery unit to the second determined level.

[0045] According to some embodiments, the control unit may be further configured to communicate information regarding the health condition to an external recipient.

[0046] For example, the control unit may be configured to communicate this information to an operator of the battery module and / or the load. Often, battery modules are used as backup power source for critical infrastructure in remote locations. Access to the site can be difficult. Site visits for purposes such as maintenance or inspection are rare. Providing information about the SoH of the battery module / unit allows the remote operator to plan maintenance or replacement in a timely manner.

[0047] According to some embodiments, the information regarding the health condition may comprise a warning message if the determined health condition falls below a predefined threshold.

[0048] According to some embodiments, the load may be telecommunications equipment. Battery modules used as backup power sources may be used, for example, to ensure that critical infrastructure continues to function in the event of a power outage. Telecommunications equipment, such as communication base stations, is one example of a critical part of the infrastructure. In a crisis, such as after an earthquake, storm, or other natural disaster that may result in a power outage, telecommunications equipment is particularly important to coordinate rescue and recovery efforts. Furthermore, telecommunications equipment may be installed in remote locations, as communication is needed even in inaccessible areas.

[0049] According to a second aspect of the disclosure, a method of operating a battery unit is provided. The battery unit is configured to receive input power from an external power source and to provide power to a load in the absence of the input power. The method includes performing a charging cycle when the input power is available. The charging cycle includes charging the battery unit to a first predetermined level using the input power (i.e., drawing power from the external power source). The charging cycle further includes disconnecting the battery unit from the input power upon reaching the first predetermined level. The charging cycle further includes discharging the battery unit to a second predetermined level. Upon reaching the second predetermined level, the charging cycle further includes determining a discharge time of the battery unit from the first predetermined level to the second predetermined level, and determining a state of health of the battery unit based on the determined discharge time. The charging cycle further includes reconnecting the battery unit to the input power to recharge the battery unit to the first predetermined level. The first and second predetermined levels define an interval that ensures backup functionality of the battery module throughout the entire charging cycle.

[0050] As explained above with reference to embodiments of the first aspect of the present disclosure, according to some embodiments the first predetermined level may be 95% or higher.

[0051] According to some embodiments, the second predetermined level may be 70% or greater.

[0052] In general, it will be understood that the descriptions and advantages discussed with reference to the first aspect of the present disclosure apply mutatis mutandis to the second aspect of the present disclosure.

[0053] According to some embodiments, discharging may include providing power to a control unit of a battery module in which the battery unit is located.

[0054] The method may, for example, be implemented in and / or executed by a control unit.

[0055] According to some embodiments, the method may further comprise discharging the battery unit to a second predetermined level using an adjustable resistive load.

[0056] The method may further include an adjustable load resistor, which may be adjusted, for example, to achieve a desired discharge rate.

[0057] According to some embodiments, the method may further comprise communicating information regarding the health condition to the recipient.

[0058] Any embodiment described herein with respect to the first aspect of the disclosure may also be combined with any other embodiment described herein, for example with respect to the second aspect of the disclosure, and vice versa, the disclosure relates to all combinations of features.

[0059] Exemplary embodiments will now be described in more detail with reference to the accompanying drawings. [Brief description of the drawings]

[0060] [Figure 1] FIG. 1 is a schematic diagram of a power arrangement for a load including a battery module according to some embodiments. [Diagram 2] FIG. 2 is a schematic diagram of a battery module according to some embodiments. [Diagram 3] FIG. 3 is a graph illustrating a charging cycle according to some embodiments. [Figure 4] FIG. 4 is a flow chart illustrating a charging cycle of a method of operating a battery unit according to some embodiments.

[0061] As shown in the figures, the sizes of elements and regions may be exaggerated for illustrative purposes and are provided to illustrate the general structure of the embodiments.

[0062] Like numbers refer to like elements throughout. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] Exemplary embodiments will now be described in more detail with reference to the accompanying drawings, in which a currently preferred embodiment is shown. However, the present invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein, but rather these embodiments are provided for thoroughness and completeness and to fully convey the scope of the invention to those skilled in the art.

[0064] Referring to FIG. 1, a power plant including a battery module will be described according to some embodiments.

[0065] 1 is a schematic diagram of a power plant 110 (or power system) for supplying power to a load 130. In this example, the load 130 is a piece of telecommunications equipment, such as a base station. The power plant 110 receives power 121 from an external power source, such as the mains, a power grid, a generator, or an external battery.

[0066] The received power 121 may be converted by an (optional) power supply unit 120 or converter. For example, the power supply unit 120 may receive an AC voltage of 90-440V, 50-60Hz, or a DC voltage of 100-500V. The power supply unit 120 may convert the received power to, for example, DC 24V or DC 48V, or any power suitable for powering the load 130.

[0067] During normal operation, the load 130 is powered by the (potentially converted) received power 123. However, when power 121 is not received or is insufficient, the load 130 is powered by the battery module 100.

[0068] The battery module 100 may be configured such that if the input power 122 (to the battery module 100) is lost, the battery module 100 automatically begins supplying power 124 to the load 130.

[0069] 2-4, the battery module 100 and a method of operating the battery unit according to some embodiments will be described.

[0070] 2 is a schematic diagram of a battery module 100. The battery module 100 receives input power 122 from an external power source, which may be used to charge the battery units 204 of the battery module. If the input power 122 is unavailable, e.g., due to a failure of the external power source, the battery units 204 may provide output power 124 to the load 130. When the input power 122 is present, i.e., when the external power source provides power to the battery, the controller 202 of the battery module is configured to execute a charging cycle 4000, as shown in the flowchart of FIG. 4 and the graph of FIG. 3.

[0071] During the charging cycle 4000, the battery unit 204 is charged at 4010 to a first level or state of charge (SoC) l1.

[0072] At 4020, when it is detected (at time t1) that a first level l1 has been reached, for example by a voltage measurement of the battery unit 204, the battery unit 204 is disconnected from the input power 122 at 4030 and allowed to discharge at 4040.

[0073] The discharge at 4040 may be due to self-discharge, that is, the battery unit 204 discharging without connection between the electrodes or an external circuit, and is often due to an internal chemical reaction.

[0074] Additionally, the controller 202 may be powered by the battery unit 204. Thus, the discharge may be due at least in part to self-discharge of the battery unit and power consumption by the controller, which may increase the discharge rate.

[0075] Alternatively, the battery module 100 may further comprise an adjustable load resistor 206 that may be used to improve control of the discharge rate. For example, the adjustable load resistor 206 may comprise a network of resistors, which may be switched in and out to adapt the resistance of the network. Alternatively, the adjustable load resistor 206 may be part of a cell balance resistor network used to balance the charge among the individual cells of the battery unit 204. The controller 202 may further be adapted to control the adjustable load resistor 206. As a further option, the battery module may comprise a (non-adjustable) load resistor (not shown) used to discharge the battery unit from a first level to a second level.

[0076] Once the battery unit 204 is discharged to the second level l2 (at time t2, step 4050), the battery unit 204 is reconnected to the input power 122 (step 4060) and allowed to (re)charge again to the first level l1 at 4010. The first level l1 and the second level l2 define the charge / discharge interval during which a charging cycle is performed.

[0077] In step 4052, the discharge time t d is determined. Discharge time t d is the time required for the battery unit 204 to discharge from the first level l1 to the second level l2.

[0078] discharge time t d is related to the state of health (SoH) of the battery unit 204. Thus, the discharge interval (between l1 and l2) used to determine the state of health of the battery unit 204 is the same as the charge / discharge interval used in the charging cycle to maintain the backup capability of the battery unit for the system to which it is connected.

[0079] The beginning of life capacity (BOL) of the battery unit is known. As the battery ages, the capacity of the battery unit decreases, so the discharge time from a first level l1 (e.g., fully charged) to a second level l2 for a given load / discharge rate becomes shorter. The actual (current / present) capacity of the battery unit is determined by the determined discharge time t d may be estimated by comparing with an initial value or a previous value.

[0080] From the actual capacity, the SoH of the battery unit can be determined. Determined discharge time t d Based on the SoH, a state of health of the battery unit 204 is determined 4054. Information related to the SoH may (optionally) be communicated 4056 to a recipient.

[0081] The method and battery module described with reference to Figures 1-4 may provide that the state of health of the battery unit 204 may be repeatedly determined. Thus, changes in the SoH may be monitored and maintenance planning may be facilitated. Furthermore, the risk of the battery unit not functioning when needed may be reduced.

[0082] Those skilled in the art will understand that the present invention is in no way limited to the preferred embodiments described above, but on the contrary, many modifications and variations are possible within the scope of the appended claims.

[0083] Although features or elements are described above in particular combinations, each feature or element can be used alone without the other features or elements, or in various combinations with or without the other features or elements.

[0084] Moreover, from a study of the drawings, the disclosure, and the appended claims, those skilled in the art can understand and effect variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements, and the indefinite articles "a" or "an" do not exclude a plurality. The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.

[0085] LIST OF EMBODIMENTS 1. A battery unit (204) configured to receive input power from an external power source and to provide power to a load in the absence of said input power; a control unit (202) configured to perform a charging cycle when the input power is present, the charging cycle comprising: Charging (4010) the battery unit to a first predetermined level (l1) using input power; disconnecting (4030) the battery unit from the input power once the first predetermined level is reached; Upon reaching a second predetermined level, discharging (4040) the battery unit to the second predetermined level (l2); The discharge time (t d ) (4052), determining a state of health of the battery unit based on the determined discharge time (4054); and reconnecting (4060) the battery unit to the input power and recharging the battery unit to the first predetermined level.

[0086] 2. The battery module of embodiment 1, wherein the first predetermined level is 95% or greater.

[0087] 3. The battery module of any of the preceding embodiments, wherein the second predetermined level is 70% or greater.

[0088] 4. The battery module of any of the preceding embodiments, wherein the control unit is powered by the battery unit, and discharging the battery unit between the first level and the second level includes discharging power from the battery unit to the control unit.

[0089] 5. The battery module of any of the preceding embodiments, further comprising an adjustable load resistor (206), and wherein the control unit is further configured to discharge the battery unit to a second predetermined level using the adjustable load resistor.

[0090] 6. The battery module of any of the preceding embodiments, wherein the control unit is further configured to communicate (4056) information regarding the health condition to an external recipient.

[0091] 7. The battery module of embodiment 6, wherein the information regarding the health state includes a warning message if the determined health state falls below a predetermined threshold.

[0092] 8. The battery module of any of the preceding embodiments, wherein the load (130) is a communication device.

[0093] 9. A method for operating a battery unit configured to receive input power from an external power source and power a load, comprising: If the input power is present, Charging (4010) the battery unit to a first predetermined level (l1) using the input power; disconnecting (4030) the battery unit from the input power once the first predetermined level is reached; Discharging (4040) the battery unit to a second predetermined level (l2), and upon reaching the second predetermined level: The discharge time (t d ) (4052), determining a state of health of the battery unit based on the determined discharge time (4054); and Upon reaching a second predetermined level, discharging (4040) the battery unit to the second predetermined level (l2); The discharge time (t d ) (4052), determining a state of health of the battery unit based on the determined discharge time (4054); and reconnecting (4060) the battery unit to the input power and recharging the battery unit to the first predetermined level; wherein the first predetermined level and the second predetermined level define an interval that ensures backup functionality of the battery module throughout a charging cycle. method.

[0094] 10. The method of embodiment 9, wherein said first predetermined level is greater than 95%.

[0095] 11. The battery module of any of the preceding embodiments 9-10, wherein the second predetermined level is greater than 70%.

[0096] 12. The battery module of any of the preceding embodiments 9-11, wherein discharging to a second predetermined level includes supplying power to a control unit of the battery module in which the battery unit is disposed.

[0097] 13. The method of any of the preceding embodiments 9-12, further comprising discharging the battery unit to the second predetermined level using an adjustable load resistor.

[0098] 14. The method of any of embodiments 9-14, further comprising communicating (4056) the health condition information to a recipient.

[0099] 15. The method of embodiment 14, wherein the information regarding the health condition includes a warning message if the determined health condition falls below a predetermined threshold.

Claims

1. a battery unit (204) configured to receive input power from an external power source and to supply power to a load in the absence of said input power; a control unit (202) configured to perform a charging cycle when the input power is present; The charging cycle comprises: The input power is used to power the battery unit at a first predetermined level ( １ ) (4010); disconnecting the battery unit from the input power once the first predetermined level is reached (4030); The battery unit is charged to a second predetermined level ( ２ ) (4040), and upon reaching the second predetermined level: The discharge time (t ｄ ) (4052); determining a state of health of the battery unit based on the determined discharge time (4054); and and reconnecting (4060) the battery unit to the input power to recharge the battery unit to the first predetermined level; wherein the first predetermined level and the second predetermined level define an interval that ensures backup functionality of the battery module throughout the entire charging cycle. A battery module (100).

2. The battery module of claim 1 , wherein the first predetermined level is greater than or equal to 95%.

3. The battery module of any one of claims 1-2, wherein the second predetermined level is 70% or more.

4. the control unit is powered by the battery unit; and The battery module of any one of claims 1-3, wherein the discharging of the battery units between the first level and the second level includes discharging power from the battery units to the control unit.

5. Further comprising an adjustable load resistor (206); The battery module of any one of claims 1-4, wherein the control unit is further configured to discharge the battery units to the second predetermined level using the adjustable load resistance.

6. The battery module of any of claims 1-5, wherein the control unit is further configured to communicate (4056) the health status information to an external recipient.

7. The battery module of claim 6 , wherein the health status information comprises a warning message if the determined health status falls below a predetermined threshold.

8. The battery module of any one of claims 1 to 7, wherein the load (130) is a telecommunications device.

9. 1. A method for operating a battery unit configured to receive input power from an external power source and to power a load, the method comprising: performing a charge cycle when the input power is present; The charging cycle comprises: Charging the battery unit to a first predetermined level using the input power (4010); disconnecting the battery unit from the input power once the first predetermined level is reached (4030); discharging the battery unit to a second predetermined level (4040); and upon reaching the second predetermined level, determining a discharge time for the battery unit to reach the second predetermined level from the first predetermined level (4052); determining a state of health of the battery unit based on the determined discharge time (4054); and reconnecting the battery unit to the input power to recharge the battery unit to the first predetermined level (4060); It is equipped with wherein the first predetermined level and the second predetermined level define an interval that ensures backup functionality of the battery module throughout the entire charging cycle. method.

10. The method of claim 9 , wherein the first predetermined level is greater than 95%.

11. The method of any of claims 9-10, wherein the second predetermined level is greater than 70%.

12. The method of any of claims 9-11, wherein said discharging to said second predetermined level comprises providing power to a control unit of a battery module in which the battery unit is located.

13. The method of any of claims 9-12, further comprising discharging the battery unit to the second predetermined level using an adjustable resistive load.

14. The method of any of claims 9-14, further comprising communicating (4056) said health condition information to an external recipient.

15. 15. The method of claim 14, wherein the health condition information comprises a warning message if the determined health condition falls below a predetermined threshold.

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