DE102009058893A1 - Method for monitoring charging condition of rechargeable battery in e.g. electric vehicle, involves determining charging condition value, and determining maximum value, minimum value or reference value from determined value - Google Patents

Abstract

The method involves determining a charging condition value correlated with a charging condition of a rechargeable battery in a vehicle by current integration. A maximum value, a minimum value or a reference value is determined from the determined charging condition value for delimitation of determined charging condition value in an upward manner, for limitation of determined charging condition in a downward manner and for backtracking the charging condition value by battery parameters respectively.

Description

The The present invention relates to a method of monitoring the state of charge of a rechargeable battery, in particular in one Vehicle.

The Knowledge of the current battery state of charge is especially at modern motor vehicles equipped with a variety of electrical components are of increased importance. This is true for both conventional motor vehicles equipped with an internal combustion engine, as well as for electric vehicles and for hybrid vehicles to.

Of the Battery state of charge can be determined, for example, by determining the acid density be determined what about corresponding reference electrodes can be realized on or in the respective battery. Such a thing However, the process is comparatively complicated. As well It is possible in principle, special electrical Pulse to energize the battery to generate, the reaction The battery then an explanation of their current Charge state allows. However, such can be Generate pulses within a vehicle with difficulty. Furthermore It is basically known, the current state of charge with the help of a current integration, in which the of the battery discharged power permanently integrated over time becomes. However, the current integration has the disadvantage that occurring Errors are accumulated. A reliable power integration can be realized with comparatively high effort, that the integration is initialized with the aid of a start value, himself determined by another suitable method first must become. Furthermore, results from the inaccuracy of the current measurement a drift over time, which are also compensated got to. However, to compensate for this drift in current integration redefined states of the battery required that For example, occur in a vehicle only comparatively rare.

From the DE 10 2008 036 159 A1 A method for determining the state of charge of the battery is known, wherein a current value of a battery voltage and a current value of a battery current are detected, wherein a current value of a dynamic internal resistance of the battery is determined, wherein a value of one for a predefined value of a Discharge current of the battery is determined at the dynamic internal resistance falling voltage as a function of at least the current value of the battery current, wherein a value of a polarization voltage of the battery is determined, wherein a value of a prediction voltage for the predefined value of the discharge current of the battery as a function of at least the current Value of the battery voltage, the value of the polarization voltage and the value of the voltage dropping across the dynamic internal resistance is calculated at which a value of a quasi-Ruhespan corresponding to a rest voltage of the battery in an electrically unloaded state tion as a function of at least the value of the prediction voltage is determined and in which the state of charge of the battery is determined as a function of the value of the quasi-rest voltage. The known method is comparatively complicated to implement.

From the DE 199 60 761 C1 is another method for monitoring the residual charge and the performance of a loaded battery in a battery network with a threshold voltage level and a minimum current known, performed at least at a first time at least a first current-voltage measurement at a first load state of the battery and at least one the first measuring point is determined, in which at least at a second time at least a second current-voltage measurement is performed at a second load state of the battery and at least a second measuring point is determined, wherein the measuring points each at a load state of the battery, which is greater than 30 % of the rated capacity per hour, can be determined, in which by the measuring points a compensation curve is laid and whose intersection with the threshold voltage level is determined and the associated limit current is determined and in which by difference between the limiting current and the M current limit reserve is determined as a measure of the remaining charge available in the battery. Also, this known method can be realized only in conjunction with a relatively high cost.

The The present invention addresses the problem of for a method of monitoring the battery state of charge an improved or at least another embodiment particular, by a comparatively simple Feasibility.

This Problem is inventively by the subject of the independent claim. advantageous Embodiments are the subject of the dependent Claims.

The invention is based on the general idea of determining the state of charge basically based on a current integration, wherein the state of charge value determined thereby is estimated upwards and / or downwards as a function of additional battery parameters. In other words, with the aid of additional battery parameters, extreme values, that is to say maximum values and / or minimum values, can be determined with the aid of which the determined state of charge value can be limited, namely by a maximum value upwards or by a minimum value downwards. Furthermore, the invention additionally or alternatively proposes to determine by means of additional battery parameters at least one reference value with the aid of which the charge state value can be reset or adjusted. The invention thus uses the relatively easy to handle and in particular inexpensive realizable integration method for determining an initial value or estimated value for the state of charge of the vehicle battery. The state of charge value correlated with the state of charge can then be limited by means of simple measures upwards and / or downwards, such that the state of charge value can not be greater than an estimated maximum value or can not be less than an estimated minimum value. Additionally or alternatively, further battery parameters are monitored, which allow the determination of a reference value, which allows for balancing, resetting or adjusting the charge state value determined with the current integration. In this way, during the operation of the vehicle, operating conditions enabling the determination of a (precise) reference value can be utilized for determining such a reference value in order to be able to reconcile the state of charge value determined with the aid of current integration (inaccurate or estimated) over and over again. In this way, a drift in the current integration or an accumulation of measurement errors can be significantly reduced or reset again and again.

Especially Advantageously, the maximum values or the minimum values or the reference values based on characteristic curves or with the help of maps determine the at least one battery parameter with the state of charge relate the battery. Such maps or characteristics can be set up relatively easily in field trials and allow a simple and rapid assignment of appropriate Output values dependent on the respective input values. Map-based facilities are widely used in vehicle construction and are characterized in practice by a simple feasibility and high reliability.

Corresponding a particularly advantageous embodiment, a dynamic internal resistance of the battery can be determined, with then the state of charge of the battery up through said Maximum value is limited if the determined dynamic internal resistance the battery is above a predetermined threshold. It can be provided in principle that the maximum value depends determined by the battery temperature. For example, a corresponding characteristic field for determining the maximum value a family of characteristics included for different battery temperatures. additionally or alternatively, it may be provided the limit value, the consideration of the maximum value, depending on the battery temperature to determine. In particular, here too the dependency the limit of the battery temperature map-based stored.

According to one another advantageous embodiment may during Charging resistance of the battery can be determined. The state of charge of the battery can be lowered by the minimum value be limited if the determined charging resistance above a predetermined limit. Again, optional be, the minimum value and / or the limit depending on the battery temperature to determine what by appropriate, temperature-dependent Characteristic sets or temperature-dependent characteristics can be realized is.

The Estimation of the state of charge value using the minimum value may additionally be linked to the condition that charging for a longer period of time is present. For example, a corresponding control can be the duration Charge and the appropriate estimate of the state of charge value using the minimum value only if the charging process at least for a predetermined period of time stops and if, in addition, the determined charging resistance above the said predetermined limit value.

According to one another advantageous embodiment can be provided during a constant discharge of the battery by means of a voltage drop to determine a quasi-open circuit voltage. With Help of this quasi-static voltage can now be particularly easy a reference value for the state of charge to which the state of charge value, which is calculated using the current integration, reset becomes. In this case, it can be provided in particular that the voltage drop depends is determined by the current battery temperature. You can do this maps are again provided which show the relationship between voltage drop and discharge current with a corresponding set of characteristics, the are assigned to different battery temperatures.

Further important features and advantages of the invention will become apparent from the Subclaims, from the drawings and from the associated Description of the figures with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained not only in the particular Kom but also in other combinations or alone, without departing from the scope of the present invention.

preferred Embodiments of the invention are in the drawings and will become more apparent in the following description explained, wherein the same reference numerals to the same or similar or functionally identical components relate.

It show, each schematically

1 a block diagram illustrating a method for monitoring a battery state of charge,

2 a diagram illustrating a map for determining a maximum value,

3 a diagram for illustrating a map for determining a minimum value,

4 3 is a diagram for illustrating a characteristic diagram for determining a voltage drop;

5 a diagram illustrating a characteristic for determining a reference value.

Corresponding 1 based on a method presented here for monitoring the state of charge of a rechargeable battery, which is located in particular in a vehicle, based on the principle of power integration, which in 1 is represented by an F within an integrator 1 is shown. The integrator 1 determined using the current integration Σ a correlated with the state of charge of the battery state of charge charge SOC (State of charge). The charge state value SOC, which is comparatively unreliable with the aid of current integration, is generated by means of intervention elements 2 . 3 and 4 estimated or reset or adjusted. For example, allows a first engaging member 2 the determination of a maximum value MAX with which the ascertained state of charge value SOC can be limited upwards. The maximum value MAX is determined by means of specific battery parameters. A second engaging member 3 determines a minimum value MIN on the basis of at least one battery parameter, wherein with the aid of the minimum value MIN, the determined state of charge value SOC can be limited downwards. A third intervention member 4 allows the determination of a reference value Reset, with the help of which the determined state of charge value SOC can be reset. The reference value Reset is also determined by means of at least one battery parameter.

According to the 2 to 5 the maximum value MAX, the minimum value MIN and the reference value Reset are determined on the basis of characteristic curves or with the aid of characteristic maps.

For example, shows 2 a map 5 with several characteristics 6 , where each characteristic 6 reflects the dependence of the state of charge value SOC on the internal dynamic resistance Rdi of the battery, the different characteristics 6 different temperatures T are assigned to the battery. Furthermore, each characteristic is 6 assigned a maximum value MAX, so that ultimately depends on the dynamic internal resistance of the battery Rdi and depending on the battery temperature T, a maximum value MAX from the map 5 can be determined.

In 2 is also a limit 12 registered by the first engaging member 2 is taken into account, such that the maximum value MAX is set only if the dynamic internal resistance Rdi above the said limit value 12 lies. Also this limit 12 may depend on the battery temperature T. In the map 5 of the 2 the limit runs 12 parallel to the abscissa.

3 on the other hand shows a map 7 with several characteristics 8th , where each characteristic 8th reflects a relationship between a charging resistance Rlad and the state of charge value SOC of the battery. The different characteristics 8th are assigned to different battery temperatures T. Likewise, these characteristics 8th each assigned a minimum value MIN. In that regard, can be with the help of the map 7 Depending on the battery temperature and depending on the charging resistor riad assign different minimum values MIN. In order to be able to determine a reliable charging resistance Riad, it may be expedient to additionally monitor the duration of the respective charging process. For example, the second engaging member 3 only consider the minimum value MIN if the charging process lasts for a predetermined minimum time.

The Limiting the state of charge value SOC using the maximum value MAX up means that for the state of charge value SOC an estimate is made such that the with the current state of charge correlated state of charge value SOC maximum the Maximum value MAX can take. In contrast, that means Limiting the state of charge value SOC using the minimum value MIN down that an estimate of the state of charge value SOC is performed to that with the current one Charge state correlated state of charge value SOC is at least as large like the minimum value MIN.

In 3 is also a limit 13 as surrendered by the second intervener 13 can be taken into account, in particular such that the minimum value MIN is set only when the charging resistor Riad above this limit 13 lies. It can also be provided here that the limit 13 from the battery temperature 13 depends. In 3 the limit runs 13 inclined to the abscissa.

4 shows another map 9 that has several characteristics 10 contains, each representing a dependency of a voltage drop .DELTA.U from the discharge current IBatt. It is the different characteristics 10 each associated with a different temperature T of the battery, so that also here the voltage drop .DELTA.U can be determined depending on the battery temperature T from the discharge current IBatt.

5 shows a characteristic 11 representing the relationship between a quasi-rest voltage U0 and the reference value for the state of charge REF-SOC. With the help of this characteristic 11 can be determined on the basis of the current battery voltage UBatt in conjunction with the voltage drop .DELTA.U the quasi-rest voltage U0 of the battery, which via the characteristic 11 to the reference value of the state of charge REF-SOC leading to the reference value Reset the 1 equivalent. With the aid of this reference value REF-SOC or reset, the state of charge value SOC determined by means of the current integration F and limited by the extreme values MAX and MIN can now be reset to a reliable initial value or initial value. As a result, fault accumulations occurring during the current integration F due to measurement errors, which in the course of time lead to a drift in the state of charge value, can be compensated for.

Preferably, the characteristic is 11 around a discharge characteristic. Discharge characteristics are more important for the determination of the SOC, since a discharge process is more critical for the further operation of the vehicle than a charging process. In order to exclude possible hysteresis effects between discharge characteristics and charging characteristics, it is therefore preferable to use discharge characteristics for this invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 102008036159 A1 [0004]
• - DE 19960761 C1 [0005]

Claims (5)

Procedure for monitoring the state of charge a rechargeable battery, especially in a vehicle, - at a state of charge value correlated with the state of charge (SOC) determined by means of current integration (Σ), - at by means of battery parameters (Rdi, Riad, ΔU and U0) Maximum value (MAX) for limiting the calculated state of charge value (SOC) upwards and / or a minimum value (MIN) to limit the determined Charge State Value (SOC) Down and / or Reference Value (Reset) to reset the state of charge value (SOC). A method according to claim 1, characterized in that - the maximum value (MAX) from a characteristic curve ( 6 ) or from a map ( 5 ), which relates a battery parameter (Rdi) to the state of charge (SOC), and / or - that the minimum value (MIN) is derived from a characteristic curve (S) 8th ) or from a map ( 7 ), which relates a battery parameter (Riad) to the state of charge (SOC), and / or - that the reference value (reset) is derived from a characteristic curve (S) 11 ) or from a map which relates a battery parameter (U0) to the state of charge (SOC). A method according to claim 1 or 2, characterized in that - as a battery parameter, a dynamic internal resistance (Rdi) of the battery is determined, - that the state of charge value (SOC) is limited upward by the maximum value (MAX) when the determined dynamic internal resistance (Rdi ) above a predetermined limit ( 12 ), it being possible in particular for the maximum value (MAX) and / or the limit value ( 12 ) is determined depending on the battery temperature (T). Method according to one of claims 1 to 3, characterized in that - as a battery parameter during a charging a charging resistance (Riad) is determined, - that the state of charge value (SOC) is limited downwards by the minimum value (MIN) when the determined charging resistance ( Riyadh) above a predetermined limit ( 13 ), it being possible in particular for the minimum value (MIN) and / or the limit value ( 13 ) is determined depending on the battery temperature (T). Method according to one of claims 1 to 4, characterized, - that as a battery parameter during a constant discharge by means of a Voltage drop (.DELTA.U) a quasi-open circuit voltage (U0) determined becomes, - That from the quasi-rest voltage (U0), the reference value (Reset) for the state of charge (REF-SOC) is detected on the charge state value (SOC) is reset, - in which In particular, it may be provided that the voltage drop (ΔU) is determined depending on the operating temperature (T).