EP3275068A1

EP3275068A1 - Battery system and method for operating a battery system

Info

Publication number: EP3275068A1
Application number: EP16701294.7A
Authority: EP
Inventors: Ulrich Lange; Andre Boehm; Michael ERDEN; Thomas Dufaux
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-03-24
Filing date: 2016-01-21
Publication date: 2018-01-31
Also published as: US20180062215A1; CN107408830A; WO2016150584A1; DE102015205252A1

Abstract

The present invention relates to a method for operating a battery system, wherein the battery system comprises a battery which is operable using an operating parameter, wherein the method has the following method steps: a) defined operating of the battery using a predefined variable of the operating parameter in such a way that b) at least one of the duration of the operation of the battery using the predefined variable of the operating parameter and the variable of the operating parameter is selected based on a load criterion, wherein c) the load criterion is determined for maintaining a future predetermined aging progression of the battery, wherein the aging progression is based on a load of the battery by the operating parameter. A previously described method enables the operation of a battery with a particularly high performance, for example, with a particularly high capacity, in a simultaneously safe operating mode.

Description

Description title

Battery system and method for operating a battery system

The present invention relates to a battery system and a method for operating a battery system, in which an improved capacity is made possible with simultaneously high security of the battery.

State of the art

Various batteries, such as lithium-based energy storage

or lithium-ion batteries, are indispensable in today's life. Areas of application include fully electrically powered vehicles or hybrid vehicles, as well as electrical tools, electrical entertainment electronics, computers, mobile phones, and other applications.

It is often provided in a variety of batteries that they have limits with respect to various parameters in order to operate the batteries in a safe state. It is therefore known to monitor and control a battery system such that operation of the battery system in the safe operating condition can be ensured. From document JP 2014-011826 A, for example, a method is known for monitoring a charging process of a battery. It is described that a completed charging of the battery by a limit of a

Charging current is detected. In this case, a detection of the aging state of the battery to the limit value of the charging current according to the

Adapt aging state. From the document EP 0 508 720 AI a control circuit for controlling the charging of a battery is also known. The control circuit is used as input of the internal resistance of the battery, which is compared with a reference value to determine the state of charge.

Document EP 2 680 392 A1 describes a method for recharging a battery. The capacity of the battery should be increased without exceeding a charging threshold. This is to be achieved according to this document by repeated charging of the battery during a charging cycle.

From the document US 2011/0057623 AI a battery system is also known, in which the battery is monitored and appropriate information is transmitted to a charger to enable energy savings and also to increase the efficiency and functionality.

Disclosure of the invention

The subject of the present invention is a method for operating a battery system, wherein the battery system comprises a battery which can be operated with an operating parameter, the method having the method steps:

a) Defined operation of the battery with a predefined size of the operating parameter such that

b) at least one of the duration of the operation of the battery with the predefined size of the operating parameter and the size of the operating parameter is selected based on a

Load criterion, where

c) the load criterion for determining a future predetermined aging curve of the battery is determined, the aging curve is based on a load of the battery by the operating parameter. A method described above allows the operation of a battery with a particularly high performance, for example, with a particularly high capacity, while a safe operation at the same time. The method relates to operating a battery system, wherein the

Battery system includes a battery that is operable with an operating parameter.

Hereinafter, the operation of the battery with respect to a

Operational parameters described in which understands the skilled person

Way equally the operation of the battery or the

Performing the method with respect to a plurality of at least two operating parameters of the invention is included.

Furthermore, the invention will be described below with reference to a battery, wherein under a battery in a manner understandable to those skilled alike a battery cell, as well as a plurality of about to a battery module or battery pack combined battery cells are included in the invention.

The method is based on operating batteries in a conventional manner with respect to an operating parameter, such as with respect to the voltage provided by the battery, to the current flowing through the battery, and to the temperature of the battery, within values described above Operating limits are. Conventionally, a battery includes rigid operating limits. In particular, these operating limits include a safety threshold, from which on depending on the size and duration of the value of the respective operating parameter

Security measures should be taken, since when exceeding the safety threshold and thus when operating the battery in the critical operating condition may be a security impairment.

Furthermore, a standard operating threshold may be provided which is arranged at a distance from the safety threshold, the area below the standard operating threshold being the standard operating range, the range between Normal operating threshold and safety threshold is the safety operating range and the area above the safety threshold is the critical operating condition. In this case, the standard operating threshold can conventionally determine the magnitude of the value of the operating parameter, within which the battery can in principle be operated particularly advantageously with respect to the operating parameter, and can be preferred by the manufacturer of the battery

Operating limit be set. Within the standard operating threshold, the battery can be operated on the one hand without safety concerns, as this operating threshold is spaced from the safety threshold, and about below this example, with respect to the amount of the value of the operating parameter. In addition to a particularly high level of security through the provision of a safety buffer through the safety operating range, the provision of the standard operating threshold can fulfill the task that operating the battery in the frame of the standard operating threshold or in the normal operating range can also make it possible in the long term for the load on the battery to increase Operation is limited to a predefinable value. For example, the life of the battery can meet a predetermined optimal condition because the standard operating threshold may allow operation of the battery in a particularly gentle state.

The provision of the standard operating threshold or the provision of a distance of the standard operating threshold to the safety threshold can furthermore have the further advantage that an undesired triggering of

Safety measures can be omitted in the event that only a short-term exceeding of the standard operating threshold occurs. In such a case, usually a further operation without a security hazard may be possible, whereby security measures are not required. Thus, the defined provision of standard operating threshold and safety threshold basically allow a particularly gentle and reliable operation of the battery or the battery system.

In the above-described method for operating the battery system, it is now exploited that the set by a battery manufacturer standard operating threshold and thus, for example, a limitation of the voltage is valid for a variety of operations to the battery in as many as possible to be able to use different applications. As a result, however, it may be provided that a comparatively large safety operating range is provided in order to ensure safety, if necessary, in all cases

To be able to ensure operating conditions or areas of application. Thus, it has been found that between the standard operating threshold and the safety threshold, ie in the safety operating range, an operation of the battery can be made possible, in which although small adverse effects with respect to the load of the battery may be present, but safe work is still easily guaranteed. In this way, a higher voltage range can be used compared with a battery management system without the described methodology or without the use of the method described above, and thus more energy is available from the cell.

In detail, the method comprises the method steps:

Load criterion, where

c) the load criterion for determining a future predetermined aging curve of the battery is determined, the aging curve is based on a load of the battery by the operating parameter.

The method is thus based on the fact that in particular when the

Safety threshold is not exceeded, there are no security impairments but only the load of the battery can be controlled increases. As a result, in particular the impairment of the battery is increased, but this can often be accepted. In particular, a

Impairment of the battery may include future aging, so that the operating parameter or its size and the duration of the

Using the size of the operating parameter is selected based on a future aging of the battery or a load criterion associated therewith. Thus, the method can be designed in such a way or the battery system can be designed such that defined requirements for the life of the battery and thus for a future aging process can be fulfilled if the limits with respect to duration and strength of the

Using the parameter.

An aging of the battery, for example due to an increased battery voltage, can be caused, for example, by the occurrence of side reactions, which can in particular irreversibly consume active material. In the non-limiting case of a lithium battery, for example, lithium or a lithium species may be consumed.

To an aging of the battery and thus a loss of

To describe the charge carrier capacity or the charge storage capacity, a load criterion can be used. The

Stress criterion can be based in particular on a load of the battery by the operating parameters, which is used and regulated according to the invention. Thus, the method does not include adjusting the parameter based on, for example, during manufacture or start-up

predetermined value but rather based on a specific determined

Loading criterion, which during the life of the battery itself

is repeatedly determined so as to take into account the specific characteristics of the battery. This load criterion can be found in the software of a control unit of the

Battery system, such as in the battery management system, be deposited or be used and serve, for example, by increasing the load or by increasing the

To describe the performance of the battery caused aging and also to regulate the aging by controlling the operating parameter or to keep within defined limits.

An exemplary stress criterion S as a function of ampere-hours [Ah] may serve to promote aging at both very high and low voltages, and thus substantially throughout the voltage range describe the battery in which significant side reactions occur. The loading criterion S may be approximately as follows:

S describes the load criterion, which corresponds to the capacity loss of the battery due to side reactions occurring. The load criterion

S can be described, for example, as a current taking into account the sum of all side reactions l _Sr or their capacity loss after time. In other words, the capacity loss may be obtained as a temporal integral over the amount of function I _S R or side reactions, particularly in very high or low voltage regions, consuming active material, such as lithium.

For example, the sum of all secondary reactions l _Sr can be determined as follows:

In this case, the value I _S R is composed of the sum of all side reactions in a switched-off battery or during a suspension of the battery Λ · / ^ ^" ^ and the sum of all side reactions in a switched-on battery, which is thus charged or discharged

I - fi - s ⁰ ^ For the non-limiting case of performing the process in an electrically driven vehicle, the first factor can thus describe the side reactions during parking of the vehicle, whereas the second factor is about the side reactions during running of the vehicle, and thus charging or discharge of the battery can describe.

The side reactions show an exponential dependence of the voltage. In the first factor of the above equation, l _t correspond to the

Quiescent current, which is triggered by the side reaction and the the

Side reactions modeled when the battery is not operated and aging calendar kt the temperature dependence of the side reactions with a battery off, U the current battery voltage and U _t one

Threshold of the voltage at which the side reactions considered occur significantly. In particular, it is assumed that the side reactions investigated, for example, in a middle

Voltage range does not occur but only exist when a threshold voltage U _{t is} exceeded. In the second factor of the above equation, I correspond to the impressed current, Fi a

Proportionality factor, which can change, for example over the lifetime, k | describes the temperature dependence of the side reaction in a switched-on battery, U is the currently applied battery voltage and Ui the voltage threshold of the side reaction. Thus, the side reaction is proportional to Fi to the impressed current I, where Fi can change over the lifetime, for example.

As voltage, the terminal voltage of the battery in operation,

be used. However, it can be much more accurate if, for example, a control unit, such as the battery management system, the

Can estimate or measure electrode voltages of the anode and the cathode, for example, when using a lithium battery against Li ⁺ , and the result is used as the basis for the voltage U. The parameters that are not directly measurable, such as the

Temperature dependences k _t , k |, the voltage limits Ui, U _t or the proportionality factor Fi are determined by appropriate measurements. This can be realized, for example, by Zyklisierungsversuche the battery, in which, for example, capacity losses at different

Voltages are determined.

Thus, K _t , U _t and l _{t describe} the sleep state of the battery, whereas K |, Ui and Fi describe the operation of the battery. The value I _S R determinable from the predetermined parameters is, as already described, the sum of all side reactions and is integrated as an absolute value over the drive cycle; it corresponds to the capacity loss due to the secondary reactions. From the above, it can be seen that the possibly occurring loads and the associated increased aging can be controlled or determined according to the invention by b) at least one of the duration of the operation of the battery with the

predefined size of the operating parameter and the size of the

Operating parameters is selected based on a load criterion, wherein according to method step c) the load criterion for maintaining a future predetermined aging curve of the battery is determined, the aging curve on a load of the battery by the

Operating parameters based. In other words, it is at a prescribed

Provided method to provide only a security threshold firmly, but a constant used standard threshold not to have at least temporarily present but to adjust the setting of the parameters dynamically based on a predetermined and desired future aging. This allows easy achievement of aging goals. In the event that a constant normal operating range is still present, this can be left in a predefined and desired manner with respect to the operating parameter, wherein preferably the size of the parameter in the safety operating range and the duration in which the parameter in the safety operating range a particular size, are controlled in a predefined way.

In particular, aging may be in an acceptable range and may also be predictable.

In the method described above, the usable operating range of the operating parameter can thus be increased, at least to a limited extent, in a defined and controlled manner, without having to fear unpredictable and unwanted influences on the battery and associated disadvantages.

In contrast to the prior art methods, where a predetermined constant normal operating threshold should always not be exceeded, the method described above takes an opposite route and uses the safety operating range beyond an imaginary constant Standard operating threshold to increase in a defined manner the performance of the battery. It thus finds a targeted setting the

Operating parameters instead of such that its size can also go into an original safety operating range, so as to be able to adjust the performance in the desired manner. It is a merit of the inventors to have found that in this way, without security concerns and calculable and predeterminable impairments, the performance of the battery can be significantly increased.

The above-described method therefore makes use of the fact that, by exceeding the standard operating threshold or by removing a constant standard operating threshold, the performance of the battery can be significantly increased compared to a permanent operation within the originally set standard operating threshold, without having to accept a loss of security or significant limitations.

No cumbersome implementation of the method in existing operating systems is necessary, but the above-described operation of the battery system can be done in a simple manner by the battery management system, for example. In this case, the method may further

Based on parameters that are often determined anyway, so that in

Essentially no further sensors or the like need to be used.

Thus, the above-described method can easily and surely increase the performance of the battery such as the capacity of the battery.

As part of an embodiment, it may be provided that the

Operating parameter is selected from the group consisting of voltage, current and temperature. In particular, the aforementioned operating parameters, ie the voltage provided by the battery, the current flowing through the battery and a temperature of the battery may allow a significant increase in the performance of the battery to be made possible by a corresponding increase in this operating parameter. This becomes apparent for example, using the voltage of the battery as

Operating parameters. Even with a comparatively small increase in the voltage of exemplary 0.25 V, for example from 4.15 V to 4.40 V, an increase in capacity by 15% can be made possible, with the abovementioned values being only an example. It may also be provided in the sense of this embodiment that only one of the aforementioned operating parameters is used, or that a plurality of at least two of the aforementioned

Operational parameters are used or the battery system with respect to these wanted and defined in the respective

Safety operating range is operated.

As part of a further embodiment, it may be provided that the method takes place during a charging of the battery. In other words, in this embodiment, for example, the voltage can be increased in a defined manner, so that, for example, the charging threshold or state of charge threshold can be increased in a defined manner on the basis of a desired future aging process. This configuration may be of particular advantage, since in a charging process with increasing state of charge even at a relatively small increase in the state of charge or the voltage of the battery, a comparatively large increase in the capacity of the battery can be made possible. Thus, especially when the method is at least partially, in particular completely, carried out during a charging process, a significant increase in the capacity and thus the performance of the battery can be generated.

It may also be preferred if the loading criterion is determined during the operation of the battery. Determining the load criterion during the operation of the battery may mean that the

Loading criterion is determined during charging or discharging the battery. In this embodiment, the load criterion can be determined online, ie immediately during operation. As a result, this can always be based on current values, which can make determining the load criterion particularly exact. As a result, compliance with a desired course of aging, for example, can be made particularly safe and precise. In this embodiment, therefore, be determined Quantities, such as current or voltage, determined immediately during operation of the battery.

It may also be preferred if the load criterion based on a stored history of the operating parameter, in particular at a

Resting phase of the battery, is determined. In this embodiment, during operation of the battery, only the corresponding operating parameter or operating parameters, such as current and / or voltage, may be recorded. Characterized in that a determination during a rest phase of the battery, so when no charging or discharging takes place, can take place, for example during parking a vehicle, the computing power of the battery management system can be chosen particularly low during operation of the battery. As a result, no increased demands on the equipment of the battery system or on the design of the battery management system need to be adhered to. An implementation in existing systems is thus possible by a simple software adaptation without further conversion measures.

In addition, the load criterion can be determined under

exclusive consideration of values above a predefined threshold. This threshold may be, for example, the limit Ui or U _t , from which a side reaction begins significantly. Basically, the threshold can be chosen such that only from this threshold an increased aging occurs. Such a value may be, for example, 4.1 to 4.2V. Up to this threshold, the battery can be operated easily and still meet their aging goals. Thus, considering only the values above the threshold may be sufficient, since the corresponding values below the threshold in determining the aging are only of minor relevance and thus their inclusion does not or not significantly affect the result. By concentrating on the aforementioned relevant values, however, can to a great extent

Computing capacity can be saved, for example, the battery management system, so that a determination of the load criterion online, so while operating the battery, can be easily possible. With reference to determining the predetermined aging curve on the basis of a load criterion, which is determined on the basis of a stored history of the operating parameter, these operating parameters can be stored, for example, in a two-dimensional histogram. This may be particularly advantageous if, as explained above, two approximately contiguous operating parameters, such as the current and the voltage, are equally stored. For a two-dimensional histogram having a plot of the current vs. voltage, a determination of the stress criterion may be made as follows:

U I

Again, j ^" | lsR | <t corresponds to the load criterion as already stated above, Σ ΣΝ - dt corresponds to the sum of all found ones

U I

Measurands of the respective operating variable, ie here the current and the

Voltage over time, where N is the number of values found, and

I l _B ins | corresponds to the resolution of the determined measuring points, for example of current and voltage, in the histogram. By referring to the

Time integral and the sum of the measuring points of the histogram is the form of the load criterion:

'U I

The aforementioned preferred examples relate in particular to determining the load criterion and thus, for example, the aging curve on the basis of the voltage as the operating parameter.

Further possibilities for determining the load criterion or other suitable operating parameters include, for example, the temperature, the current intensity or jumps or strokes of the state of charge (SOC strokes) during operation of the battery, such as in a drive cycle of an electrically driven vehicle. Also, such parameters can adversely affect the electrode material, such as by phase transitions. For example, an increased current strength leads to an increased temperature, SOC strokes lead to a swelling and swelling of the electrodes and thus to material wear.

An exemplary stress criterion for the temperature could be determined according to the above conditions or assumptions as follows:

In this case, I _{T is} again the no-load current, k _{t is} the temperature dependence of the side reaction or the aging effects, and T _{t is} the threshold value of the temperature at which the secondary reactions or the

Aging effects occur.

Combinations of load criteria of different operating parameters can also be determined in a manner understandable to a person skilled in the art.

The above-described method can include a large part of the factors that cause aging of the battery. However, the quality of the control may still allow reliable operation of the battery, even if the unobserved parameters, such as calendar aging or other neglected factors, account for up to 70% of the total aging.

It may also be advantageous that the predefined size of the

Operating parameters is selected depending on a control period. For example, the size can be selected for a short-term control that applies, for example, for some charging cycles, such as five charging cycles, and also for a long-term control that applies, for example, to more than ten charging cycles. In this embodiment, therefore, on the one hand a long-term control can be made possible, which regulates a permanent operation of the battery and also a

Short-term control, by which the performance can be increased even more briefly. For example, the long-term control one

Include charge throughput of, for example 5000Ah and about in the area apply for a few months. Furthermore, a short-term control can apply, for example, for an exemplary charge throughput of 100 Ah or one or a few weeks.

With regard to further technical features and advantages of the method, reference is hereby explicitly made to the statements concerning the battery system, to the figures and to the description of the figures, and vice versa.

The subject matter of the present invention is furthermore a battery system, comprising at least one battery and a control unit for regulating the battery. The battery system is characterized in that the control unit is designed to carry out a method as described in detail above.

In detail, the battery system may include a battery or a plurality of batteries, such as a plurality of battery cells. The batteries

or battery cells can be connected to a battery module, for example, in order to enable the desired specification. By way of example and in no way limiting, the battery or batteries may be lithium batteries, such as lithium-ion batteries. Furthermore, it can be provided that the battery system is arranged in an at least partially electrically driven vehicle.

The battery system has, in addition to the battery, a control unit which can regulate the operation of the battery and thus has at least one control circuit. For this purpose, appropriate sensors may be provided to detect, for example, the temperature of the battery, the voltage provided by the battery or the current flowing through the battery. Furthermore, a

Arithmetic unit be provided which determines based on the detected operating parameters, whether a control intervention is necessary or how the

Operating parameters should be set to realize a desired specification, such as a desired aging process.

Particularly preferably, it may be provided that the control unit has at least a first control loop and a second control loop nested with the first control loop. In this embodiment, a particularly effective regulation of the battery is made in particular with reference to a method as described in detail above.

It may be particularly preferred if the first control loop is formed to at least one controlled variable to achieve a predetermined

Aging history issue and that the second control loop is designed to at least one controlled variable to achieve a predetermined

Issue load criterion. In order to realize this, it may be preferred that a desired value of the first control loop is selectable and / or that a desired value of the second control loop is based on a controlled variable output by the first control loop.

A prescribed control structure can enable the battery to be controlled in a particularly effective and secure manner, in which case the battery can be safely controlled or carried out, for example

Regarding a maximum load can be regulated. In this case, a rule with respect to a load can be nested with a control with regard to a desired aging process. In detail, in particular by providing two nested

Control circuits, as explained above, it is possible that by entering a desired aging curve in the first control loop this outputs a controlled variable, which serves as an input of the second control loop. Based on this input, the second control loop can regulate the battery to a desired load, in particular if a load criterion can be determined based, inter alia, on the controlled variable of the first control loop. Thus, the control unit can operate by a simple input of a target aging, the battery with a defined load in order to meet the desired aging can.

With regard to further technical features and advantages of the battery system, reference is hereby explicitly made to the statements concerning the method, to the figures and to the description of the figures, and vice versa. Further advantages and advantageous embodiments of the objects according to the invention are illustrated by the drawings and explained in the following description, wherein the features described individually or in any combination may be an object of the present invention, as far as the context does not clearly indicate the opposite. It should be noted that the drawings only

descriptive and are not intended to limit the invention in any way. Show it

Fig. 1 is a schematic view of different operating conditions of a

Battery;

FIG. 2 is a schematic view of a voltage waveform of a battery over time; FIG.

Fig. 3 is a schematic view of another voltage waveform of a

Battery over time;

Fig. 4 is a schematic view of another voltage waveform of a

Battery over time;

Fig. 5 is a diagram showing, by way of example, the regulation of a battery;

Fig. 6 is a schematic view of a control structure;

FIG. 7 shows, by way of example, determining a load criterion based on a

histogram; and

Fig. 8 is a schematic example of the regulation of a battery over a plurality of charging cycles.

In FIG. 1, with reference to the temperature and the voltage of a battery, different operating states are shown schematically and purely by way of example, within which the battery may be intended or unintentionally in operation. In detail, the temperature T on the X axis is against the

Battery voltage U shown on the Y-axis. The include

Operating conditions a standard operating range 10, a

Safety Operating Area 12 and a critical operating area 14. It is further shown that a standard operating threshold 16 separates the standard operating area 10 and the safety operating area 12 and that a safety threshold 18 separates the safety operating area 12 and the critical operating area 14. The standard operating range 10 is such an operating range in which the battery is operated such that both a particularly high level of security is given and other predetermined requirements can be met, such as cell capacity, energy content, charge / discharge power, and

End-of-life or end-of-life criteria (EOL criteria). Such a standard operating range 10 can for example be defined or limited by the manufacturer of the battery or the battery system by an operating threshold.

The critical operating range 14 is still one in which

Safety impairing effects are to be expected. Thus, it may be provided in a critical operating range in particular that

Countermeasures are taken, so at least one measure is initiated to counteract an incoming error case.

The safety operating area 12 is also one in which further ensures safe operation of the battery is such that no

Serious error cases or irreversible damage to the battery are to be feared, which entail a repair. Certain requirements, such as the capacity, life or the like, but can be changed or influenced in this operating range. It is preferred if a sufficient distance between the standard operating threshold 16 and the safety threshold 18 is provided. In this way, a slight crossing of the

Normal operating threshold 16 can be accepted without the immediate

Countermeasures must be initiated, which may not be necessary during a desired operation. This may occur, for example, unintentionally during an operating operation of the battery for a short time, or this may for a predetermined duration and in a

take predetermined measure, as will be described below.

FIG. 2 schematically shows the time t on the x-axis and the voltage U on the y-axis. Furthermore, the curve 20 shows the voltage applied to the battery

Tension. Furthermore, a predetermined charging limit 22 is shown, as well the standard operating threshold 16, which limits the standard operating range 10, and may for example lie slightly above the charging limit 22, for example within a range of 5 mV, and the safety threshold 18, from which approximately the critical operating range 14 can be present and below which approximately the safety operating range 12 is present can.

Further, the areas ti may indicate a charging operation, t _{2 may be} a discharging operation, such as during operation of an electrically driven vehicle, and 3 may be a recuperation operation. It can be seen that it is often impossible to prevent the voltage, for instance during charging or during a charging process

Recuperation, unintentionally on the charging limit 22 and over the standard operating limit 16 increases. However, this can be accepted because the standard operating threshold 16 is a sufficiently large distance from the

Safety threshold 18, so that the voltage is always in the

Safety operating area 12 is located.

In this case, an assessment can be made of the extent to which operation of the battery in the safety operating area 12 can be accepted, in particular assessing the strength of the operating parameter, such as the voltage, and the corresponding duration of the operation in the safety operating area 12 Figure 3 shown.

In detail, FIG. 3, as well as FIG. 2, shows the time t on the x-axis and the voltage U on the y-axis. Furthermore, the curve 20 again shows the voltage applied to the battery. Furthermore, a predetermined charging limit 22 is shown, which in this embodiment corresponds to the standard operating threshold 16, which limits the standard operating range 10, and the safety threshold 18, from which approximately the critical operating range 14 can be present and below which approximately the safety operating range 12 can be present.

The ranges and I4 t ₅ show a relatively small period of time of exceeding the normal operation threshold 16, such as in a period of 300ms (I4), and 500ms (t _5). Furthermore, with respect to the time duration, the time periods t ₆ correspond to the period I ₄ and the time period t _{7 to} the time period t ₅ . With respect to magnitude of the voltage in the period of operating the battery in the Safety operating range 12 can be seen that during the periods t ₆ and t _{7 is} a significantly greater voltage than at 1 ^ and tj.

In this case, a mere consideration of the duration of the operation of the battery in the safety operating area 12 as well as the mere consideration of the strength of the operating parameter during the operation of the battery in the

Safety area 12 be sufficient. However, this may lead to results of a comparatively low quality, since a time concentration t ₅ and t ₇ would be regarded as critical, whereas a pure consideration of the strength would be considered critical

Periods t ₆ and t ₇ would be considered critical.

Considering both the time periods and the strength of the respective operating parameter, which is approximately based on the basis of the area under the curve 20 above the standard operating threshold 16, ie the hatched area in

3, this can lead to a changed and possibly improved result. Mathematically, this can be described as follows:

Xerr = i (U meas ulimit) dt,

where X _{err is} an error integral and U _mea s the measured or occurred voltage and υ _Μ the voltage threshold corresponding to the standard operating threshold 16. This can lead to the following values for the respective periods and voltages purely by way of example: X _err for t ₄ is 3mVs, Xerr for t ₅ is 5mVs, X _err for t ₆ is 15mVs and X _err for t ₇ is 25mVs. Based on this data, an accurate and reliable estimation of, for example, the negative influence of the battery can be made possible.

Alternatively, a quadratic weighting can be done:

Xerr = i (U meas ulimit dt

This can lead to values at the corresponding time periods and stresses purely by way of example and in comparison to the above assumption: Xerr for t ₄ is 30μ \ / ² 8, X _err for t ₅ is 50μ \ / ² 8, X _err for t ₆ is 750μ \ / ² 8 and Xerr for t ₇ is 1250μν ² 8. On the basis of this data an even more accurate and thus even more reliable estimation of, for example, the negative influence of the battery can be made possible. The square weighting of the voltages has the advantage that a particularly defined operation of the battery can be made possible.

It can thus be seen that, with respect to one or more operating parameters, by evaluating both the duration of operating the battery in the safety operating area 12 or with a defined size and the size of the operating parameter during the operation of the

Operating parameters in the safety operating area 12 or with the relevant size in an advantageous manner, a defined operation of the battery in the safety operating area 12 and the respective size can be made possible.

Coming back to Figure 1, with respect to the location of the

Operating thresholds 16, 18, for example, fall back to a classification of EUCAR, which is a classification into different levels of danger in certain electrical system (EEES) fault situations. According to this classification, different effects are attributed different effects. these can

For example, from the lowest level of danger, in which no negative effect is to be expected, to a strongest danger level, in which, for example, an explosion of the battery must be expected to run. The

Standard operating threshold 16 with respect to the one or more

Operating parameters can be arranged below the danger level 0 according to EUCAR and the safety threshold 18 can also correspond approximately to the limit of the danger level 0 according to EUCAR. These thresholds are often determined by the manufacturer and are in a tax or

Control unit, such as deposited in the battery management system. As a rule, these thresholds are generally valid and thus predetermined equally for all driving states or applications, in order to enable a safe and generally balanced operation of the battery in relation to all operating states.

According to the invention, it is now provided that the operation of the battery is no longer basically to all operating conditions or

Applications in advance, but rather the burden of To control battery selectively and so to improve the performance of the battery.

In the figure 4 the inventive method is shown schematically.

In particular, in a comparison to Figure 2 it can be seen that the

desired charging voltage threshold 22 in a defined manner in the

Safety operating area 12 is shifted. It will be apparent to those skilled in the art that a standard operating threshold 16 may still be present, but need not necessarily be present, that is, can be regarded as an imaginary threshold in the following. This can be increased by achieving an increased voltage despite a safe operation of the battery

Capacity can be achieved, in particular by a long-term control, the voltage is in a defined manner in the safety operating range and not mainly, as shown in Figure 2, in the

Standard operating range 10. This may be particularly advantageous because at comparatively small increases in voltage, a comparatively large improvement in capacity is possible.

In this case, it can be realized by a suitable control or regulation, for example, that the performance of the battery increases as desired, but the load on the battery, in particular its aging, does not rise above a predefined value. This is shown in FIG.

Figure 5 shows in detail in the upper diagram schematically a mission of the life of the battery on the axis Xi and on the axis Yi a load on the battery. In the lower diagram is schematically an order of

Life of the battery on the axis X ₂ and on the axis Y _2, a threshold value of an operating parameter, such as the voltage shown. The curve 24 shows a concrete load on the battery, the curve 26 shows a desired limit of the load of the battery, the curve 28 shows a concrete operational parameter, such as the voltage, and the line 30 shows a desired threshold of the operating parameter, such as about the standard operating threshold 16. Furthermore, the sections I to VI should specify different time intervals. By comparing the upper graph and the lower graph, it can be shown that it is possible to respond to different and, if appropriate, unforeseen influences by means of a corresponding control, that is to say by raising or lowering the size of the operating parameter, such as the voltage and so to keep the stress always within desired limits. As a result, for example, the aging of the battery can also be maintained as desired.

For example, at the beginning of section II, if the actual

Stress below the desired or allowed value is the voltage raised. On the other hand, if the actual load is above a prescribed value, the operating parameter can be lowered, as shown in section III, so that in a simple manner always a predetermined load can be maintained. A preferred but purely exemplary control structure 32 for performing regulation based on, for example, a battery load is further shown in FIG. The control structure 32 is in particular part of a control unit of a battery system. The control structure 32 in FIG. 6 is in particular part of a

Battery system and can be part of a control unit in detail

or control unit, such as the battery management system. The control structure 32 according to FIG. 6 or the control relationship or control unit can be connected to the battery via connections, not shown, in order thus to effect a control intervention based on the principles described in US Pat

Rule structure 32 ejected controlled variables to perform.

In detail, the control structure 32 comprises a first control loop 35 and a second control loop 37 interleaved with the first control loop 35, as will be seen below. In this case, the first control loop 35 is designed to be at least one controlled variable to achieve a predetermined

Aging history output and the second control circuit 37 is further formed to at least one controlled variable to achieve a

to spend given load criterion. In detail, a desired value of the first control loop 35 is selectable and based on a target value of the second Control circuit 37 on one of the first control loop 35 output controlled variable.

The operation of the control structure 32 or the interleaving of the control circuits 35, 37 will be described below.

First, in an input unit 34, in particular as the only external input into the control structure 32, a target value of a desired

Aging or aging history with respect to the capacity (SOHc) entered. This can, for example, a capacity of

80% within 10 years or within a mileage of 300,000 km in relation to the original value and thus, for example, refer to a desired value at a certain time in the future, whereby a linear decrease can be assumed. Thus, in the function block 36, there is the target SOHc which should be present based on a desired aging history. This is routed to a function block 40, which is likewise supplied with a currently present SOHc. The currently present SOHc can be determined by the function block 38 and routed to the function block 40. The currently present SOHc can be determined in a manner understandable to a person skilled in the art on the basis of measured voltage values during a charging cycle, for example.

By comparing the desired SOHc with the currently present SOHc, a corresponding difference can be determined in the function block 40.

This is passed into a transformation block 42, such as a PID controller, which can output a control variable as output 44 by defining a desired controlled system in a manner known per se and easily implementable in the control technology. As such a controlled variable, for example, a target load for the battery can be output to thereby adjust the aging by adjusting the stress.

The desired stress is in turn directed to a function block 46, in which the target stress with a currently existing stress is compared. The present stress can be found in the

Function block 48 are determined and routed to the function block 46. Figure 7 shows an example of determining a stress criterion during operation of the battery. In detail, a two-dimensional histogram is shown in the upper diagram of Figure 7, in which the

Voltage is indicated in particular as the upper voltage limit on the X-axis and wherein the current flowing through the battery is indicated on the Y-axis. The scale N also shows the number of occurrences of the corresponding ones

Values. Such a history of operating parameters may occur during operation of the battery, for example. By way of example, this can be realized during a travel time of an electrically driven vehicle of about 10 hours.

A change of the voltage value leads to a shift of the histogram, since the current is multiplied by the factor e ^{(U "U (l))} .

In the lower diagram, the cell voltage U _ce ii is plotted against the factor e ^Uce ", whereby it can be seen that a significant change occurs, especially at high voltages, and it becomes particularly clear that inclusion of values which are above a limit value Ui, may be sufficient, since values below this limit may not cause significant changes.

Coming back to functional block 46, the difference in the setpoint and the present value of the stress is formed therein and passed to transformation block 50, such as a PI D controller. This can be optionally applied with additional limits as upper and lower limits of the values to be controlled. In this is output 52 again a

Control variable output, which is about an operating parameter, such as

In particular, current, voltage or temperature can be to thereby adjust the stress on the setpoint, as is possible in the control technology in a known and easily implementable way by defining a desired controlled system. The controlled variable can be from the output 52 are directed approximately in a memory 54. Regardless of the provision of the memory 54, the controlled variable can be passed into the function blocks 38, 48. Thus, in the function block 38, in turn, the currently present SOHc can be determined, and in the function block 48, the currently existing stress can be determined.

The operating principle is thus based on setting a target load or setpoint load for the battery, by means of which a defined aging process of the battery can be made possible. A prerequisite for this is the definition of a suitable, measurable stress value, which accumulates over time and which, according to this embodiment, is based on the desired aging process.

The above regulation serves in particular a long-term regulation. It may further be provided that the outputs 44, 52 with respect to a

Short-term control can be varied, the thresholds are thus increased briefly. For this purpose, further setpoints 43, 53 are processed.

FIG. 8 shows an example of a regulation of a battery according to the invention. On the axes Χ-ι, X ₂ , X3 and X ₄ respectively the number of charging cycles are plotted, whereas on the axis Y1 the SOHc is plotted, on the axis Y ₂ a voltage threshold in volts is given, which is based on the control according to the invention , and wherein on the axes Y ₃ and Y _4, the aging or the SOH loss per charge cycle is plotted.

In the upper diagram, the line 58 shows the setpoint value of the aging and the curve 60 shows the determined value of the aging. It can be seen in the upper diagram that at approximately 400 charge cycles one

unforeseen increase in aging occurs.

In the second diagram, the voltage set by the control can be recognized by the curve 62. It is shown that the controller settles in the first cycles on a regulated cell voltage as the upper limit. In particular, with reference to the second diagram, the height of the baseline shows a long-term control, whereas the peaks show a short-term control. Due to the short-time control, a higher voltage level can be reached for a short time, which can be increased by 100mV, for example. Furthermore, it can be seen that the set voltage in the loss of SOHc

or is reduced in the event of unforeseen aging by the voltage is reduced by the regulation by about 70mV. As a result, as can be seen in the upper diagram, the actual value of the SOHc equalises again to the desired value.

In the third diagram, the curve 64 shows the aging, whereas in the fourth diagram, the curve 66, the target load or the

SOHc loss, and curve 68 shows the actual stress or actual SOHc loss. Again, the effectiveness of the scheme can be seen, as even with an unforeseen change in aging by adjusting the stress acting on the battery aging can be constant again, so that the desired values of future aging can be easily met, since the SOHc Loss matches the target value.

Claims

claims

1 . A method of operating a battery system, the battery system comprising a battery operable with an operating parameter, characterized in that the method comprises the method steps:

Load criterion, where

2. The method according to claim 1, characterized in that the

Operating parameter is selected from the group consisting of

Voltage, current and temperature.

3. The method according to any one of claims 1 or 2, characterized in that the method is at least partially carried out during a charging of the battery.

4. The method according to any one of claims 1 to 3, characterized in that the load criterion is determined during operation of the battery.

5. The method according to any one of claims 1 to 4, characterized in that the load criterion based on a stored history of the

Operating parameters is determined.

6. The method according to any one of claims 1 to 5, characterized in that the load criterion is determined by considering only values that are above a predefined threshold.

7. The method according to any one of claims 1 to 6, characterized in that the predefined size of the operating parameter is selected in

Dependence of a control period.

8. The method according to any one of claims 1 to 7, characterized in that the method is carried out using at least two

Operating parameters.

9. Battery system, comprising at least one battery and a control unit for regulating the battery, characterized in that the control unit is formed, a method according to one of claims 1 to 8

perform.

10. Battery system according to claim 9, characterized in that the

Control unit has at least a first control loop (35) and a second control loop (37) interleaved with the first control loop (35).

1 1. Battery system according to claim 10, characterized in that the first control loop (35) is designed to output at least one controlled variable to achieve a predetermined aging curve and that the second control loop (37) is designed to at least one controlled variable for

Achieve achievement of a predetermined load criterion.

12. Battery system according to claim 1 1, characterized in that a

Setpoint of the first control loop (35) is selectable.

13. Battery system according to claim 1 1 or 12, characterized in that a desired value of the second control loop (37) is based on one of the first control loop (35) output controlled variable.

14. Battery system according to one of claims 10 to 13, characterized

in that the battery system is arranged in an electrically drivable vehicle.