Control device and method for charging a rechargeable battery

Abstract

A control device for controlling charging of a rechargeable battery, the control device including a rechargeable dummy cell, a first circuit configured to charge the battery and the dummy cell, and a second circuit configured to measure the open circuit voltage of the dummy cell. The control device is configured to: determine the open circuit voltage of the dummy cell by using the second circuit, and determine the maximum capacity increment of the battery, which is to be charged until full charging, based on the determined open circuit voltage of the dummy cell. Also, a corresponding method of controlling charging of a rechargeable battery.

Claims

1. A control device for controlling charging of a rechargeable battery of a vehicle, comprising: a rechargeable dummy cell configured to only support controlling charging of the rechargeable battery of the vehicle, the rechargeable dummy cell being a component that is separate and apart from the rechargeable battery; a first circuit configured to charge the rechargeable battery and the dummy cell; and a second circuit configured to measure the open circuit voltage of the dummy cell, the control device being configured to: determine an open circuit voltage of the dummy cell by using the second circuit; determine a maximum capacity increment of the rechargeable battery based on the determined open circuit voltage of the dummy cell; charge the rechargeable battery and the dummy cell by using the first circuit; monitor a current capacity increment of the rechargeable battery which has been charged; and stop charging, when the current capacity increment of the rechargeable battery exceeds the determined maximum capacity increment, wherein the determined maximum capacity increment is an amount of capacity that still remains to be charged until the state of charge of the rechargeable battery reaches 100%.

2. The control device according to claim 1, wherein the control device is further configured to: determine, whether the rechargeable battery is discharged during charging, and, if yes, re-determine the open circuit voltage of the dummy cell and the maximum capacity increment of the rechargeable battery.

3. The control device according to claim 1, wherein the control device is further configured to: determine the current capacity increment of the rechargeable battery based on at least one of: (i) the charging current and the charging time of the rechargeable battery; and (ii) the open circuit voltage of the dummy cell.

4. The control device according to claim 1, wherein the control device is further configured to: determine the state of charge (SOC) of the dummy cell based on the determined open circuit voltage (OCV) of the dummy cell, the state of charge being determined from a predetermined SOC-OCV mapping, and determine the maximum capacity increment based on the determined state of charge of the dummy cell.

5. The control device according to claim 4, wherein the control device is further configured to: update the predetermined SOC-OCV mapping based on a determined degradation of the dummy cell.

6. The control device according to claim 5, wherein the control device is further configured to: determine the degradation of the dummy cell based on a temperature/frequency distribution of the dummy cell and a predetermined degradation rate of the dummy cell.

7. The control device according to claim 5, wherein the determination of the degradation of the dummy cell is based on the Arrhenius equation.

8. The control device according to claim 5, wherein the control device is further configured to: determine the temperature/frequency distribution of the dummy cell by recording for each temperature of the dummy cell how much time the dummy cell had this temperature during its lifetime.

9. The control device according to claim 4, wherein the control device is further configured to: determine the state of charge of the rechargeable battery based on a predetermined mapping between the state of charge of the rechargeable battery and the determined state of charge of the dummy cell, and determine the maximum capacity increment based on the state of charge of the rechargeable battery.

10. The control device according to claim 1, wherein the control device is further configured to: control charging of a battery of a specific battery type comprising a predetermined degradation rate, wherein the dummy cell has a degradation rate which correlates with the degradation rate of the rechargeable battery.

11. The control device according to claim 1, wherein the rechargeable battery of the specific battery type comprises a predetermined capacity, and wherein the dummy cell has a capacity which correlates with the capacity of the rechargeable battery.

12. The control device according to claim 1, further comprising: a voltage sensor for detecting the open circuit voltage of the dummy cell.

13. The control device according to claim 1, further comprising: a temperature sensor for detecting the temperature of at least one of: (i) the dummy cell; and (ii) the rechargeable battery.

14. A battery pack comprising: at least one battery, and a control device according to claim 1.

15. A vehicle comprising: an electric motor, and a battery pack according to claim 14.

16. A battery charging system comprising: at least one battery, a charging device for the at least one battery, and a control device according to claim 1.

17. A vehicle comprising: an electric motor, at least one battery, and a control device according to claim 1.

18. The control device according to claim 1, wherein the dummy cell and the rechargeable battery are a same type of battery.

19. A method of controlling charging of a rechargeable battery of a vehicle, wherein a first circuit is used to charge the rechargeable battery and a rechargeable dummy cell, the rechargeable dummy cell being configured to only support controlling charging of the rechargeable battery of the vehicle, and being a component that is separate and apart from the rechargeable battery, and a second circuit is used to measure an open circuit voltage of the dummy cell, the method comprising: determining the open circuit voltage of the dummy cell by using the second circuit; determining a maximum capacity increment of the rechargeable battery based on the determined open circuit voltage of the dummy cell; charging the rechargeable battery and the dummy cell by using the first circuit; monitoring a current capacity increment of the rechargeable battery which has been charged; and stopping charging, when the current capacity increment of the rechargeable battery exceeds the determined maximum capacity increment, wherein the maximum capacity increment is an amount of capacity that still remains to be charged until the state of charge of the rechargeable battery reaches 100%.

20. The method according to claim 19, further comprising: determining, whether the rechargeable battery is discharged during charging, and, if yes, re-determining the open circuit voltage of the dummy cell and the maximum capacity increment.

21. The method according to claim 19, wherein the current capacity increment of the rechargeable battery is determined based on at least one of: (i) the charging current and the charging time of the rechargeable battery; and (ii) the open circuit voltage of the dummy cell.

22. The method according to claim 19, wherein the state of charge (SOC) of the dummy cell is determined based on the determined open circuit voltage (OCV) of the dummy cell, the state of charge being determined from a predetermined SOC-OCV mapping, and the maximum capacity increment is determined based on the determined state of charge of the dummy cell.

23. The method according to claim 22, wherein the predetermined SOC-OCV mapping is updated based on a determined degradation of the dummy cell.

24. The method according to claim 23, wherein the degradation of the rechargeable battery is determined based on a temperature/frequency distribution of the dummy cell and a predetermined degradation rate of the dummy cell.

25. The method according to claim 24, wherein the temperature/frequency distribution of the dummy cell is determined by recording for each temperature of the dummy cell how much time the dummy cell had this temperature during its lifetime.

26. The method according to claim 23, wherein the determination of the degradation of the dummy cell is based on the Arrhenius equation.

27. The method according to claim 22, wherein the state of charge of the rechargeable battery is determined based on a predetermined mapping between the state of charge of the rechargeable battery and the determined state of charge of the dummy cell, and the maximum capacity increment is determined based on the state of charge of the rechargeable battery.

28. The method according to claim 19, wherein the dummy cell and the rechargeable battery are a same type of battery.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic representation of a vehicle comprising a control device according to an embodiment of the present disclosure;

(2) FIG. 2 shows a schematic representation of the electric circuits of the control device according to an embodiment of the present disclosure;

(3) FIG. 3 shows a flow chart of the general charging control procedure according to an embodiment of the present disclosure;

(4) FIG. 4 shows a flow chart of the procedure for updating a SOC-OCV curve according to an embodiment of the present disclosure;

(5) FIG. 5 shows an exemplary and schematic diagram of a SOC-OCV curve;

(6) FIG. 6 shows an exemplary and schematic diagram of a predetermined degradation rate in relation to the temperature of a dummy cell;

(7) FIG. 7 shows an exemplary and schematic diagram of a determined temperature/frequency distribution of a dummy cell;

(8) FIG. 8 shows an exemplary and schematic voltage—SOC diagram of a battery, when a conventional charging control is applied;

(9) FIG. 9 shows an exemplary and schematic voltage—SOC diagram of a battery, when a charging control according to an embodiment of the present disclosure is applied.

DESCRIPTION OF THE EMBODIMENTS

(10) Reference will now be made in detail to exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

(11) FIG. 1 shows a schematic representation of a vehicle 1 comprising a control device 6 according to an embodiment of the present disclosure. The vehicle 1 may be a hybrid vehicle or an electric vehicle (i.e. a purely electrically driven vehicle). The vehicle 1 comprises at least one electric motor 4, which is powered by a battery or battery pack 2, preferably via an inverter 3. In case the vehicle is a hybrid vehicle, it further includes an internal combustion engine. The battery 2 may be a solid-state bipolar battery. However, it may also be another battery type, like a liquid type battery, as e.g. a Li-ion battery.

(12) The battery 2 is connected to a charging unit 5 which is configured to charge the battery 2. For this purpose the charging unit 5 may comprise an electric control circuit, as e.g. a power electronics circuit. The charging unit may further comprise or be connected to a connector for external charging by an external power source. The connector may be e.g. a plug or a wireless connector system. In case the vehicle is a hybrid vehicle, the charging unit may further be connected to the electrical generator of the internal combustion engine of the vehicle. Consequently, the battery 2 may be charged, when the internal combustion engine is operating and/or when the vehicle is connected to an external power source. Furthermore the battery 2 may be discharged, in order to operate the vehicle 1, in particular the electric motor 4. The battery 2 may further be discharged in a battery treatment and/or recovery procedure.

(13) The vehicle further comprises a dummy cell 11 which is configured to provide information, in particular measurements, based on which the charging of the battery 2 is controlled. This will be described in more detail below. The dummy cell 11 may be a further rechargeable battery, preferably of the same type as the battery 2. It may be integrated into the vehicle, e.g. it may be integrated with the control device 6. Alternatively it may be integrated with the battery 2. In the latter case the dummy cell 11 can be easily replaced together with the battery 2. For example, the battery may be realized as a battery pack comprising a plurality of cells, wherein the dummy cell is realized as a cell of the same type and may be included in the battery pack.

(14) In order to control charging and discharging the vehicle 2 is provided with the control device 6 and sensors 7. For this purpose the control device 6 monitors the battery 2 and/or the dummy cell 2 via the sensors 7 and controls the charging unit 5. The control device 6 and/or the sensors 7 may also be comprised by the battery 2. The control device may be an electronic control circuit (ECU). It may also comprise a data storage. It is also possible that the vehicle comprises a smart battery charging system with a smart battery and a smart charging device. In other words, both the battery and the vehicle may comprise each an ECU which operate together and form together the control device according to the disclosure. In the latter case the dummy cell 11 may be integrated in the smart battery. Furthermore the control device 6 may comprise or may be part of a battery management system.

(15) The control device 6 may comprise an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), a combinational logic circuit, a memory that executes one or more software programs, and/or other suitable components that provide the described functionality of the control device 6.

(16) As it will be explained in more detail in the following, the sensors 7 comprise in particular a voltage sensor 10 for measuring the open circuit voltage (OCV) of the dummy cell 11. Moreover the sensors 7 may comprise one or more temperature sensors 8 for measuring the temperature of the battery 2 and/or the dummy cell 11, at least one SOC (state of charge) sensor 9 for measuring the state of charge of the battery 2 and/or the dummy cell 11 and at least one further voltage sensor 10 for measuring the voltage of the battery 2 and/or the dummy cell 11. The SOC sensor 9 may also be a voltage sensor, wherein the measured voltage is used to determine the SOC of the battery. Of course, the SOC sensor 9 may also comprise other sensor types to determine the SOC of the battery, as it is well known in the art.

(17) FIG. 2 shows a schematic representation of the electric circuits of the control device according to an embodiment of the present disclosure. The dummy cell 11 and the battery 2 are connected to a first electrical circuit C1, for example in series. This circuit C1 is configured to charge both the dummy cell 2 and the battery 2. Preferably the circuit C1 is also configured to discharge both the dummy cell 2 and the battery 2. A second circuit C2 is configured to measure the open circuit voltage OCV.sub.d of the dummy cell. In order to switch between the circuits C1 and C2, there may be provided a switch, which can be controlled by the control device 6. It is noted that FIG. 2 is a simplified diagram of the electric circuits of the control device.

(18) FIG. 3 shows a flow chart of the general charging control procedure according to an embodiment of the present disclosure. The control device 6 is configured to carry out this procedure of FIG. 3.

(19) In step S11 the procedure is started. The start may be triggered by a determination of the control device that charging of the battery is necessary (e.g. due to a low SOC) and/or by the fact that charging becomes possible (e.g. due to operation of the internal combustion engine or due to a connection to an external electrical power source).

(20) In step S12 the dummy cell 11 is separated from the main charging circuit C1. In other words the control device will switch to circuit C2, in which the dummy cell 11 is separated from the circuit C1. Subsequently the open circuit voltage OCV.sub.d of the dummy cell is measured.

(21) In step S13 the current state of charge SOC.sub.d of the dummy cell is determined based on the measured open circuit voltage of the dummy cell 11. Since this determination of SOC.sub.d may not be exact, it may also be referred to as a speculated value. In addition, the state of charge SOC.sub.d of the dummy cell is determined based the determined degradation of the dummy cell, as it will be explained in detail in context of FIG. 4.

(22) In step S14 the maximum capacity increment ΔAh.sub.max of the battery is determined, basically based on the open circuit voltage OCV.sub.d of dummy cell and advantageously the determined degradation α.sub.x of the dummy cell. The determined degradation α.sub.x of the dummy cell preferably corresponds to that one of the battery or has a known relationship to that one of the battery.

(23) In particular, the maximum capacity increment ΔAh.sub.max of the battery may be determined based on the determined state of charge SOC.sub.d of the dummy cell 11, which is determined in step S13 based on the open circuit voltage and the degradation of the dummy cell. In addition, the maximum capacity increment ΔAh.sub.max of the battery 2 may be determined based on a predetermined SOC-OCV mapping by identifying in the SOC.sub.d value which matches to the measured OCV.sub.d value. The SOC-OCV mapping may be regularly updated based on the determined degradation α.sub.x of the dummy cell, as it will be explained in detail in context of FIG. 4. The SOC-OCV mapping may be represented by a SOC-OCV curve, as shown in FIG. 5.

(24) More particularly, the maximum capacity increment ΔAh.sub.max of the battery may be determined based on the state of charge SOC.sub.b of the battery, which itself is determined based on the state of charge SOC.sub.d of the dummy cell 11. In order to do so, a predetermined mapping may be used which indicates the relationship between the SOC.sub.d of the dummy cell 11 (as determined in step S13) and the SOC.sub.b of the battery. For example, the maximum capacity increment ΔAh.sub.max of the battery may be calculated based on the difference between 100% SOC (determined based on the current degradation α.sub.x) and the determined current SOC.sub.b (determined based on the current degradation α.sub.x), i.e.
ΔAh.sub.max=SOC100%(α.sub.x)−SOC.sub.b(α.sub.x)

(25) The procedure of steps S13 to S14 preferably only takes a limited time, as e.g. 0.02 s, 0.05 s, 0.1 s, 0.2 s or 1 s.

(26) In step S15 the charging is started. This is done by switching to circuit C1.

(27) In step S16 it is determined, whether the current capacity increment ΔAh.sub.x of the battery exceeds the determined maximum capacity increment ΔAh.sub.max. The battery 2 is hence charged, as long as the current capacity increment ΔAh.sub.x of the battery does not exceed the determined maximum capacity increment ΔAh.sub.max. Otherwise the charging procedure is completed and finally stopped in step S18.

(28) For this purpose, the current capacity increment ΔAh.sub.x of the battery is monitored in step S16. Said current capacity increment ΔAh.sub.x of the battery may be determined based on the monitored charging current I.sub.x and the charging time of the battery, in particular based on the measured charging current I.sub.x integrated over the charging time. Additionally or alternatively the current capacity increment ΔAh.sub.x of the battery may be determined based on a previously measured open circuit voltage of the dummy cell.

(29) Moreover it is determined in step S17, whether the battery is at the same time discharged during charging. This might be due to a consumption of electrical power stored in the battery, e.g. due to a use of the electrical motor of the vehicle. Preferably the dummy cell is configured such that it is also discharged, when the battery is discharged. This may be realized by circuit C1. In this way, it is possible that the dummy cell has always a state of charge which corresponds to that one of the battery.

(30) The determination in step S17 is preferably done regularly, e.g. every 1 s, 5 s, 20 s or 1 min. In case the battery is not discharged the method returns to step S16. In other words, during charging the method runs a short loop between steps S16 and step S17.

(31) In case it is determined in step S17 that the battery is at the same time discharged during charging, the method returns to step S12. In other words, in this case of detected discharging the methods runs a long loop between steps S12 and step S17. In this way the method may again determine the maximum capacity increment ΔAh.sub.max in step S14, as described above. By doing so the method is advantageously able to determine how much amount of capacity has been discharged since the last time the maximum capacity increment ΔAh.sub.max has been determined in step S14. Moreover it is possible to consider any further degradation of the battery, which has occurred in the meantime. Hence, the maximum capacity increment ΔAh.sub.max may be determined again, thereby considering this further degradation.

(32) FIG. 4 shows a flow chart of the procedure for updating a SOC-OCV curve (i.e. a SOC-OCV mapping) according to an embodiment of the present disclosure. An exemplary and schematic diagram of a SOC-OCV curve is shown in FIG. 5.

(33) The procedure of FIG. 4 is preferably carried out in step S13 of the procedure of FIG. 3 so that the SOC-OCV curve and hence the maximum capacity increment ΔAh.sub.max is always determined based on a currently updated degradation α.sub.x. It is noted that the determined degradation α.sub.x rather represents an estimation of the actual degradation of the battery.

(34) In step S22 temperature data of the dummy cell are obtained. For this purpose the temperature sensor 8 may be used. However, these data may include not only the current temperature of the dummy cell, but also historic temperature data since the last time the procedure of FIG. 4 has been carried out, in particular since the last time the temperature frequency distribution T.sub.x has been updated (cf. step S23).

(35) In step S23 the temperature frequency distribution T.sub.x is established or, in case a temperature frequency distribution T.sub.x already exists, it is updated. For this purpose the collected temperature data obtained in step S22 are accumulated, wherein the accumulated time for each measured temperature is expressed as its inverse, i.e. as frequency. The temperature frequency distribution T.sub.x is described in more detail below in context of FIG. 7.

(36) In step S24 the degradation α.sub.x of the dummy cell is determined based on the temperature frequency distribution T.sub.x and the predetermined dummy cell specific degradation rate β, which preferably corresponds, in particular is equal, to the battery-type specific degradation rate β. This determination, i.e. calculation, is described in the following with reference to FIGS. 6 and 7.

(37) Basically the calculation of the degradation α.sub.x is based on the Arrhenius equation, as generally known in the art. The degradation α.sub.x is calculated by

(38) $\alpha x=c\times \exp \left(\frac{b}{T}\right)\times t$
wherein: t=time c=ln(A) b=−(E/R) T=Temperature
The current degradation α.sub.x is thereby an accumulated value, i.e. the currently calculated degradation and the sum of all formerly calculated degradations, as e.g.
αx1=α.sub.1+α.sub.2+α.sub.3 . . .
with:

(39) ${\alpha }_1=c\times \exp \left(\frac{b}{T_1}\right)\times t_1$

(40) The values for the temperature T and for the time t can thereby be derived from the temperature frequency distribution T.sub.x as shown in FIG. 7. The further parameters c and b are predetermined in context of the determination of the degradation rate β.

(41) The degradation rate β is calculated based on the equation:

(42) $k=A\exp \left(-\frac{E_a}{\mathrm{RT}}\right)$
wherein: k=predetermined reaction rate constant (or rate constant) A=constant E.sub.a=activation energy R=gas constant T=Temperature
The parameters k, A, Ea and R are known by pre-experiment of the specific type of the used dummy cell, which preferably corresponds to the type of the battery, or are generally known parameters.
When k.Math.β:

(43) $\ln \left(\beta \right)=\ln \left(A\right)-\left(\frac{E}{R}\right)\times \frac{1}{T}$
Accordingly, the parameters b and c for the calculation of degradation α.sub.x can be determined by: b=−(E/R) c=ln(A)
The resulting diagram of the degradation rate β is shown in FIG. 6. The degradation rate β is predetermined and specific for the type of the used dummy cell, which preferably corresponds to the type of the battery. The degradation rate β is preferably determined in pre-experiment and is known by the battery (in case of a smart battery) and/or by the control device.

(44) The SOC.sub.b of the battery may be mapped to the SOC.sub.d of the dummy cell, which itself is mapped (e.g. by way of the SOC-OCV mapping) to the determined degradation α.sub.x in a look-up map, i.e.:
α.sub.x1.Math.SOC.sub.d1.Math.SOC.sub.b1
α.sub.x2.Math.SOC.sub.d2.Math.SOC.sub.b2
α.sub.x3.Math.SOC.sub.d3.Math.SOC.sub.b3
α.sub.x4.Math.SOC.sub.d4.Math.SOC.sub.b4

(45) etc.

(46) This relation between SOC.sub.d and αx and/or between SOC.sub.b and SOC.sub.d is preferably determined in a pre-experiment and is specific for the battery-type of the used dummy cell, which preferably corresponds to the battery-type of the battery 2. The look-up map may be stored in a data storage of the control-device or of the battery (in case of a smart battery).

(47) FIG. 5 shows an exemplary and schematic diagram of a SOC-OCV curve. As it can be seen, the OCV values are successively increasing with increasing SOC, in particular in the region of SOC>30%. Hence, at least in said region for each OCV value a unique SOC value can be determined from the SOC-OCV curve. The SOC-OCV curve is preferably predetermined in experiments before the battery is used. During the lifetime of the battery the battery SOC-OCV curve is continuously updated, at least once per charging procedure described in context of FIG. 3.

(48) FIG. 6 shows an exemplary and schematic diagram of a predetermined degradation rate in relation to the temperature of a dummy cell. As it can be seen the values of the parameters b and c can be directly derived from this diagram, as b is the slope of the linear function and c is the intercept of the (elongated) linear function with the Y-axis.

(49) FIG. 7 shows an exemplary and schematic diagram of a determined temperature/frequency distribution of a dummy cell. In the diagram the x-axis represents the temperature T of the dummy cell and the y-axis represents the frequency, i.e. the inverse of the time. The diagram contains the accumulated temperature data of the dummy cell over its whole life time, i.e. over the whole time the dummy cell has been used and the rest times between the usages. In order to establish the diagram, i.e. the illustrated curve, it is determined for each temperature the dummy cell had during its life time, e.g. from −40° C. to +60° C. in (quantized) steps of 1° C., how much time the dummy cell had each of these temperatures. The accumulated time is thereby expressed by its inverse, i.e. by a frequency. Preferably, the life time of the dummy cell corresponds to that one of the battery 2. The temperature of the dummy cell should approximately correspond to that one of the battery, so that their degradation is the same. Accordingly, the dummy cell may be positioned close to the battery. Also both the dummy cell and the battery may be positioned in a case of a battery pack. This case may be equipped with a cooling fan and/or means for stabilizing the temperature of the dummy cell and the battery. Thereby, the temperature of the dummy cell and the battery can become equal.

(50) FIG. 8 shows an exemplary and schematic voltage—SOC diagram of a battery, when a conventional charging control is applied. As it can be seen the voltage V of the battery increases during charging, i.e. it increases with an increasing SOC of the battery.

(51) The continuous line thereby represents a battery without any degradation, e.g. a new battery. The measured voltage V of such a battery reaches during charging the upper voltage limit V.sub.max, when the SOC reaches 100%. As an effect, it is correctly determined that charging is completed and charging is stopped.

(52) The dashed line represents a battery with lamination degradation, e.g. a used battery. The measured voltage V of such a battery increases more strongly during charging due to the higher resistance caused by the lamination degradation. The voltage V therefore reaches already the upper voltage limit V.sub.max, when the SOC is about 80%. As an effect, it is erroneously determined that charging is completed and charging is stopped. This can be avoided by the present disclosure as described in context of FIG. 9.

(53) FIG. 9 shows an exemplary and schematic voltage—SOC diagram of a battery, when a charging control according to an embodiment of the present disclosure is applied. FIG. 9 illustrates the same case as FIG. 8, i.e. a (new) battery without any degradation and a (used) battery having a lamination degradation. Both curves increase until they reach the initial upper voltage limit V.sub.max. The dashed line representing a battery with lamination degradation thereby reaches the initial upper voltage limit V.sub.max, when the SOC is about 80%.

(54) However, according to the disclosure, charging is controlled based on the capacity of the battery and not based on the voltage V of the battery. Hence, charging is not stopped, when the voltage of the battery exceeds V.sub.max. Instead, charging is continued until current capacity increment ΔAh.sub.x exceeds the determined maximum capacity increment ΔAh.sub.max and is only stopped at this time.

(55) For this purpose the maximum capacity increment ΔAh.sub.max is determined, before charging is started, and during charging the current capacity increment ΔAh.sub.x is continuously monitored. In the present example charging is started at a SOC.sub.b of 40%. Hence, the determined maximum capacity increment ΔAh.sub.max corresponds to the remaining 60% SOC. When charging is started and the voltage of the battery exceeds V.sub.max at 80% SOC, the current capacity increment ΔAh.sub.x does not yet exceed the determined maximum capacity increment ΔAh.sub.max. Hence, charging is continued.

(56) In case it is detected during the charging process that the battery is discharged at the same time, the maximum capacity increment ΔAh.sub.max is re-determined. Accordingly, in the example of FIG. 9, if the battery is discharged e.g. by 5%, the maximum capacity increment ΔAh.sub.max may be re-determined, in order to add these lost 5%. At the same time, any further degradation may be anticipated, when re-determining ΔAh.sub.max.

(57) Throughout the disclosure, including the claims, the term “comprising a” should be understood as being synonymous with “comprising at least one” unless otherwise stated. In addition, any range set forth in the description, including the claims should be understood as including its end value(s) unless otherwise stated. Specific values for described elements should be understood to be within accepted manufacturing or industry tolerances known to one of skill in the art, and any use of the terms “substantially” and/or “approximately” and/or “generally” should be understood to mean falling within such accepted tolerances.

(58) Where any standards of national, international, or other standards body are referenced (e.g., ISO, etc.), such references are intended to refer to the standard as defined by the national or international standards body as of the priority date of the present specification. Any subsequent substantive changes to such standards are not intended to modify the scope and/or definitions of the present disclosure and/or claims.

(59) Although the present disclosure herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure.

(60) It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims.