DE102009051268A1 - Motor vehicle e.g. passenger car, has storage modules charged by motor-/generator unit in symmetrical condition such that difference of charging states of storage modules is reduced - Google Patents

Abstract

The vehicle has a storage measuring unit (3) determining a difference between charge states of storage modules (7) e.g. capacitors, during a drive and generating a warning signal with excess of maximum threshold value for difference of the charge states. A hybrid drive (1) is transmitted in to a symmetrical condition during a driving time interruption of a vehicle driver automatically or manually based on the signal. The storage modules are charged by a motor-/generator unit (6) in a symmetrical condition such that the difference of the charging states of the storage modules is reduced. An independent claim is also included for a method for operating a motor vehicle.

Description

Technical area:

The invention relates to a motor vehicle with a hybrid drive, via an electrically operable motor / generator unit, via an internal combustion engine, which is coupled to generate electrical energy in a generator operation to the motor / generator unit, via at least two in series or parallel memory modules Energy storage in which the electrical energy generated by the motor / generator unit in the generator mode can be stored, via a memory measuring unit, through which a state of charge of the at least two memory modules can be detected and a hybrid management, with the loading of the memory modules in dependence of the memory measuring unit measured charge state is controllable, has.

State of the art:

The invention is in the field of hybrid vehicle technology. Hybrid vehicles are vehicles in each of which at least two energy converters and two energy storage systems are present to drive the vehicle. As a preferred energy converter electric, gasoline or diesel engines are used, while it is in the energy storage in particular batteries, capacitors and / or fuel tanks. Other hybrid drives, such as a Stirling engine with hydraulic output and pneumatic accumulator have already been implemented. Hybrid drives are basically suitable both for use in passenger cars and in commercial vehicles, especially in buses and trucks. Especially in recent times, the public discussion about increasing the energy efficiency of vehicles and minimizing the CO ₂ emissions caused by road traffic has significantly increased the importance of hybrid technology for the vehicle industry.

Hybrid vehicles usually have energy stores that are composed of a number of electrical storage cells. As an energy storage both batteries, such as lithium-ion batteries, as well as capacitors, preferably double-layer capacitors or so-called. Supercaps come into question. For the range and the life of the energy storage used type and extent of the charge of the individual memory cells are of particular importance.

Provided in modularly constructed energy storage double-layer capacitors offer in the provision and storage of electrical energy the advantage that they can provide short-term high performance available. Moreover, in order to be able to provide the supply voltage required in a motor vehicle, the individual memory cells, that is to say the capacitors which are preferably used, are connected in series or, preferably, cascaded.

The series-connected cells form a cell structure, wherein it is important when charging a so constructed energy storage that on the one hand the state of charge of the entire energy storage reaches a high level, and on the other hand, that between the individual memory cells no so-called asymmetries with respect. the operating voltage arise. Such asymmetries lead above all to a reduction in the storage capacity and to a shortening of the life of an energy store. For this reason, it is necessary to compensate for asymmetries occurring between the individual memory cells at regular intervals. For this balancing, it is necessary that the energy storage is kept at its maximum charge level for a certain time. Since this maintenance of the maximum charge level can not be assured reliably over a long period of time in normal vehicle operation, especially when the vehicle such as a bus is operated in city traffic, special balancing methods are used to standardize the charge level of the individual storage modules. In this case, special Symmetrierungsverfahren are needed because it is controlled via the conventional hybrid management of a vehicle with integrated memory management, in which operating state of a hybrid vehicle, the electrical energy storage is charged or discharged, asymmetries with respect to the state of charge of individual memory cells are not compensated.

In order to always achieve a comparatively high state of charge of the energy accumulator during operation of a hybrid vehicle, the German patent application describes DE 10 2007 021588 A1 a strategy with a so-called. Casual shop, in which the charging of the energy storage during vehicle operation in response to the operating state and the state of charge at the end of a Betriebszyklusses to the beginning should be substantially unchanged.

The DE 10 2007 013873 A1 describes a method and apparatus for charging an energy store which is coupleable to a generator driven by a hybrid engine. When the vehicle is stationary, either an off-vehicle or an in-vehicle charging device is used to recharge the energy store. For this purpose, the energy storage is connected to the generator, in addition to or as an alternative to the internal combustion engine of an auxiliary combustion engine is driven. The essential idea of the technical solution described is thus that, when the vehicle is at a standstill, in particular during breaks in operation, the energy store is recharged by the generator being driven by an auxiliary combustion engine, for example the auxiliary heater.

A method with which not only the total charge state of an energy store but also of the individual memory cells can be detected is described in US Pat DE 10 2006 005334 A1 described. In the described technical solution, the voltage of at least one cell group of a cell group is detected and finally controlled as a function of the measured voltage. The individual cells and / or cell groups are each assigned a cell logic which regulates the operating behavior, in particular the charging and the charge retention of the individual cells. Furthermore, a central control unit is provided, which coordinates the loading and unloading of the individual cells and cell groups, so that a symmetrization of the individual memory cells should be optimally ensured during the operation of a vehicle.

In reference to that from the DE 10 2006 005334 A1 Known methods are known technologies with which a symmetrization with respect to the charge states of the various memory cells is performed during vehicle operation, as soon as a first limit for a maximum allowable asymmetry has been recognized by a memory management system. In such control method is attempted by means of the hybrid management, as long as possible to keep a maximum charge level of the energy storage in normal driving. In this charging strategy, in contrast to the hybrid drives commonly used, the internal combustion engine is not turned off during a traffic or operational stop, but continues to operate to maintain the charging level.

Starting from the already known technical solutions, there is always the problem that sufficient symmetrization of different memory cells of the energy storage device of a hybrid vehicle can not be ensured in many operating states of a hybrid vehicle. This is mainly due to the fact that the requirements for a hybrid vehicle, especially due to different applications or purposes, vary considerably. For example, the operating conditions of a vehicle in cross-country traffic are different than in city traffic, such as distribution or public transport.

For the aforementioned reasons, it can often not be reliably ensured over considerable operating periods of a vehicle that the memory cells of the energy store are adequately balanced. Strong differences in the symmetry of the state of charge of individual memory cells have, above all, a negative effect on the life of the energy store and require frequent visits to the workshop.

Based on the prior art described above and the resulting problems, the invention has for its object to provide a hybrid drive for a motor vehicle, are at least largely excluded with the occurring during operation of the motor vehicle asymmetries between the charge states of individual memory cells. In this context, in particular the life compared to known energy storage systems to be improved and the need for additional maintenance on the energy storage, especially if they are associated with workshop stays are reduced.

The above object is achieved with a motor vehicle with hybrid drive according to claim 1 and a method for operating a motor vehicle with hybrid drive according to claim 12. Advantageous embodiments of the invention are the subject of the dependent claims and are explained in more detail in the following description with partial reference to the figures.

The invention relates to a motor vehicle with a hybrid drive, via an electrically operable motor / generator unit, via an internal combustion engine, which is coupled to generate electrical energy in a generator operation to the motor / generator unit, via at least two in series or parallel memory modules Energy storage in which the electrical energy generated by the motor / generator unit in the generator mode can be stored, via a memory measuring unit, through which a state of charge of the at least two memory modules can be detected and a hybrid management, with the loading of the memory modules in dependence of the memory measuring unit measured charge state is controllable, has. According to the invention, the hybrid drive is distinguished by the fact that a difference between the charge states of the at least two storage modules can be determined by the storage measuring unit and if a maximum limit value for the difference of the charge states is exceeded, a warning signal can be generated on the basis of which the hybrid drive during a driving time interruption Vehicle driver automatically or manually by the driver in a Symmetrierungszustand can be transferred, in which the memory modules by the engine / generator unit driven by the engine so be charged, that reduces the difference of the charge states of the at least two memory modules.

It is essential to the technical solution according to the invention that symmetrization of the memory modules can be initiated automatically or by the driver when the driver makes a driving time interruption, that is to say a journey break. Here, the duration of the break is basically irrelevant. It is only important on the one hand that the vehicle does not actively participate in the road traffic at this time, but a break in operation is carried out in a parking lot, on a depot or at a holding or loading point, and on the other hand, that for the introduction neither specially trained Person still appropriate additional aids are needed. In principle, the symmetrization of the memory modules according to the invention during a driving time interruption of the driver may alternatively or in addition to a preferably automatic balancing of the memory modules during the driving operation of a motor vehicle with hybrid drive, in particular at traffic lights, at stops and / or other vehicle stops are made. Likewise, it is conceivable to initiate the symmetrization of the memory modules during a driving time interruption of the driver, either by the driver in response to a corresponding signal, in particular a display that appears while driving or actuation of deactivation of the hybrid drive by the driver, a corresponding switch before he deactivated the hybrid drive, or by being automatically initiated and the driver is informed accordingly that the hybrid drive is fully deactivated or deactivated only after completion of the balancing.

In a particularly preferred embodiment, the symmetrization of the memory modules according to the invention is carried out until the difference in the charge states falls below a tolerable limit value stored in hybrid management. If such a limit value is exceeded, the balancing mode is terminated either automatically or in response to appropriate information manually by the driver. Only after completion of the balancing and finally the hybrid drive of the vehicle is manually or automatically deactivated. In any case, the hybrid drive is designed such that the aforementioned steps during a driving time interruption of the driver, so while the vehicle is not actively participating in road traffic, caused automatically or manually by the driver, are feasible.

The technical solution according to the invention ensures, in particular, that as soon as a central vehicle control unit, in particular the hybrid management, a signal is generated that the deactivation of the hybrid drive or decommissioning of the internal combustion engine is to effect, before decommissioning a symmetrization of at least two memory modules with respect to their charge states and / or voltages are effected so that the corresponding parameters are within an allowable tolerance value. If it is determined that there is an asymmetry of the charge states and / or voltages between at least two memory modules of the energy store and that this asymmetry is not within the permissible tolerance value, the internal combustion engine is initially not taken out of operation despite the presence of a corresponding command. Instead, the internal combustion engine continues to operate and the electrical energy generated by the generator coupled to the internal combustion engine is stored in the memory cells until the at least one asymmetry lies within the permissible tolerance value. In this context, it is basically irrelevant whether the request to put the vehicle out of service is generated automatically, or whether the driver wants to take the vehicle out of operation after completion of a journey by manual operation of an operating unit, in particular the ignition key. Essential to the invention is in each case that either automatically or manually to a corresponding information to the driver out, a symmetrization of the memory modules is made as soon as a longer break represents a suitable possibility for this purpose.

In a further preferred embodiment of the invention, an audible, visual and / or haptic signal perceptible in the area of the driver's workplace is generated on the basis of the generated warning signal. With an appropriate measure, the driver is made aware that there are certain asymmetries between the charge states of individual memory modules of the energy storage and he should put the hybrid drive in a Symmetrierungsmodus for prolonged interruption or termination of a ride, especially the engine should continue to operate until so long the asymmetries of the charge states have been largely compensated, ie lie within an allowable tolerance value. As soon as the charge states of the individual memory modules are approximately the same, the driver is signaled by a change in the signal in the area of the driver's workstation or another signal that the hybrid drive can now be deactivated, ie put out of operation.

In the case of asymmetries, the charge states of individual memory modules are preferred on a display located in the driver's workplace display unit, in particular the driver's display, a note is displayed, which makes the driver aware that the engine should initially be operated after completing a ride. As soon as, following the appearance of this indication in the display, the asymmetries of the charge states between the individual memory modules lie within the tolerance value stored in the control unit, the indication, which is preferably executed in the manner of a pictogram on the driver's display, disappears, so that the driver recognizes that the engine can now be issued.

A further alternative or additional embodiment of the invention provides that the driver receives a message in an automatic by a vehicle control unit or manually generated by the driver request for decommissioning of the vehicle drive, for example by means of an ignition key, preferably via a driver's display, by the Driver is informed that a balancing of the memory modules of the energy storage is required. In this way, on the one hand it is ensured that the driver acquires knowledge of the need for symmetrization and, on the other hand, that the driver can decide whether the required symmetrization of the memory modules should be carried out immediately or only at a later time. As soon as the memory measuring unit has detected a difference in the charge states of at least two memory modules of the energy store and it has been determined by the hybrid management that the detected difference is above a maximum permissible limit value, a corresponding warning signal is generated and the driver then receives a warning signal at the latest when a decommissioning request is made in hybrid management Message about the required balancing provided. If the symmetrization is subsequently carried out, the internal combustion engine continues to be operated for so long as electric energy is supplied by the generator for the energy store until the asymmetries lie below the permissible, tolerable limit value.

The memory modules used are preferably capacitors, in particular so-called ultracars, supercapacitors and / or double-layer capacitors. However, the inventive idea is not restricted to the use of special memory modules, but rather can be used in a preferred manner for all energy stores which have individual memory modules or memory cells connected in series or in parallel.

In a further advantageous embodiment, it is conceivable that the internal combustion engine is designed as a rotary machine, in particular as a microturbine or rotary piston machine. Also in this case, it should be noted that the inventive technical solution can be used in principle in connection with any internal combustion engine and different electric drives. It is equally irrelevant for the invention whether the hybrid drive of a motor vehicle is a series or a parallel hybrid drive. Likewise, it is conceivable in an advantageous development of the invention that, alternatively or in addition to the internal combustion engine, a further energy generating unit, such as a fuel cell unit, is used.

In a further particularly suitable embodiment of the hybrid drive according to the invention of a motor vehicle, at least one first and one second limit value for tolerable charge differences are stored in the hybrid management. First and second limit values can preferably be specified for special operating states of the vehicle and each represent maximum tolerable differences for the state of charge and / or the operating voltage of at least two memory modules or memory cells. When driving the hybrid vehicle, the first limit value for a maximum tolerable charge and / or voltage difference between two memory modules, so exceeded a tolerable asymmetry with respect to the state of charge, a symmetrization of the memory modules is always and as long as carried out, as the operating condition of the vehicle, in particular the load request, this allows. In this case, electrical energy is generated by means of the internal combustion engine and the generator driven by it, and the memory modules are charged until, in turn, energy is required for driving the vehicle.

If, during operation of the hybrid vehicle, the second limit stored in hybrid management for a maximum permissible difference of the charge or voltage states of individual memory modules or memory cells is exceeded, a warning signal is generated as a further measure on the basis of which during a driver's driving time interruption, So a driving break, automatically or manually initiated by the driver a symmetrization of the memory modules.

In a specific embodiment of the invention, a message in the area of the driver's workplace is generated on the basis of the warning signal generated after exceeding the second limit value. Preferably, in the area of the driver's display, a display appears, from which it appears that the hybrid drive, in particular the internal combustion engine, during a Driving time interruption should continue to operate until the asymmetries are balanced with respect to the charge differences of the memory cells in the electrical energy storage. A driving time interruption is characterized in this context mainly by the fact that no driving-related load requirements applied to the hybrid drive.

A special development of the invention provides that a successful completion of the symmetrization is indicated to the driver by another message or the original message disappears. If the driver wants to continue his driving time interruption following the successful balancing, the hybrid drive is deactivated manually in a preferred manner. In principle, however, it is also conceivable in this case that deactivation of the hybrid drive takes place automatically after completion of the balancing.

In the following the invention with reference to the figure without limiting the general inventive idea is explained in detail. It shows:

FIG. 1 shows a circuit diagram of the control of a vehicle hybrid drive with balancing circuit.

In the figure is schematically a hybrid drive 1 a motor vehicle shown with an energy storage 2 for storing electrical energy, with a memory measuring unit 3 as well as with a hybrid management system 4 is interconnected. The hybrid drive 1 here has an internal combustion engine 5 , which via a positive and / or positive connection to a combined motor / generator unit 6 can be coupled. The combined motor / generator unit 6 can optionally be used to generate electrical energy in the generator mode or as a supplied with electrical power drive unit in engine operation. In engine operation, the motor / generator unit 6 from the energy store 2 supplied with electrical energy. The switching between the generator and the engine operation of the motor / generator unit 6 is through the hybrid management system 4 controlled. Depending on the operating conditions of the vehicle, in particular the load requirements and / or the state of charge of the energy storage 2 , is using the hybrid management system 4 the vehicle optionally by the internal combustion engine 5 or the then working as an electric motor motor / generator unit 6 driven.

The energy storage 2 has individual capacitors, which are the memory modules 7 form and are connected in series. In the charging mode of the hybrid drive 1 becomes the energy store 2 , in particular the memory modules 7 , By means of operating in this operating case as a generator to the internal combustion engine 5 coupled motor / generator unit 6 supplied with electrical energy. The charge of the individual memory modules 7 , in particular with regard to charging time, charging voltage and / or charge history, is using the hybrid management 4 depending on the operating state of the hybrid drive 1 and / or the memory modules 7 regulated.

Once during operation of a hybrid vehicle in the energy storage 2 a first limit value for the asymmetry between the charge states of at least two memory modules 7 is detected, generates the hybrid management 4 a warning signal, based on which a symmetrization of the memory modules 7 is requested. On the basis of the warning signal generated after exceeding the first limit value for the charge difference, the hybrid drive is activated during the normal driving operation of the vehicle 1 regulated such that over a longest possible period a maximum charge level of the energy storage 2 is held. In this control strategy, in particular vehicle stops at traffic lights and / or stops for charging the energy storage 2 used by the internal combustion engine 5 with the standing in operative connection generator of the hybrid drive 1 unlike other known hybrid control strategies, is not decommissioned but continues to operate. In this way, in many cases, a symmetrization of the memory modules 7 of the energy store 2 ensured in terms of their state of charge during normal driving without this maintenance or workshop visits are necessary.

Depending on the intended use of a hybrid vehicle, however, it may happen that a symmetrization of the energy storage 2 during normal driving can not be done sufficiently, for example, because the vehicle does not stop often enough and / or for too short periods.

In cases where sufficient balancing can not be done during normal driving, is in hybrid management 4 a second limit with respect to asymmetry of at least two memory modules 7 of the energy store 2 deposited. As soon as the second limit value for the asymmetry of the charge states of at least two memory modules 7 in the energy store 2 is reached and / or exceeded, a further warning signal is generated on the basis of a diagnostic message on the driver's display 8th is shown. In addition, in hybrid management 4 at the same time already after Exceeding the first limit request was made to carry out a balancing maintained.

Through the diagnostic message on the driver's display 8th the driver is informed that the hybrid drive unit 1 of the vehicle at a suitable time, namely during a driving time interruption, in particular during a break or at the end of a trip, should be placed in an operating state in which a symmetrization of the memory modules 7 of the energy store 2 in terms of their charge states is feasible. The message thus gives the driver the opportunity to decide which driving time interruption, ie, for example, the next shorter break or after parking the vehicle on the depot after the end of shift to be used for balancing. After the driver has learned of the Symmetrierungsbedarf, he puts the hybrid drive in a selected by him driving time interruption, which should not be too long after the appearance of the diagnostic message in the driver's display, in a balancing mode. Once the balancing is completed successfully, resulting from a measurement of the storage measurement unit 3 as well as data processing based on this in hybrid management 4 is detected, the display disappears in the driver's display, so that the driver is now informed that he can take the vehicle out of service or disable the hybrid drive.

During execution of the described method, the vehicle is during a driving time interruption of the driver of a drive over a period of time for a sufficient symmetrization of the memory modules 7 is required, with active hybrid drive 1 , which corresponds to a running engine in conventional combustion drive parked. Through the hybrid management 4 becomes the hybrid drive 1 operated in balancing mode until all memory modules 7 of the energy store 2 are balanced at a maximum charge level with respect to the state of charge.

After completion of the balancing becomes symmetrization requirement in the hybrid management 4 and the output of a diagnostic message on the driver's display 8th withdrawn. Thus, the driver is informed in each case, so both while driving and / or after completion of a ride on whether the memory modules 7 of the energy store 2 are sufficiently balanced in terms of their state of charge or should be initiated at the next opportunity during a driving time interruption symmetrization. If the symmetrization is performed after completion of a trip, the final deactivation of the hybrid drive 1 after Symmetrierungsende done both automatically or manually by the driver or another operator.

With the described system for balancing memory modules 7 of the energy store 2 a hybrid drive 1 can thus be reliably ensured even with different load requirements to a vehicle that a balancing without additional tools and especially without additional workshop stays is feasible.

LIST OF REFERENCE NUMBERS

1

hybrid drive

2

energy storage

3

Memory measurement unit

4

hybrid management

5

Internal combustion engine

6

Motor / generator unit

7

memory module

8th

driver's display

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102007021588 A1 [0006]
• DE 102007013873 A1 [0007]
• DE 102006005334 A1 [0008, 0009]

Claims (15)

Motor vehicle with a hybrid drive ( 1 ), which via an electrically operable motor / generator unit ( 6 ), via an internal combustion engine ( 5 ) used to generate electrical energy in a generator operation to the motor / generator unit ( 6 ) can be coupled via at least two memory modules connected in series or in parallel ( 7 ) of an energy store ( 2 ), in which by the motor / generator unit ( 6 ) electrical energy generated in the generator mode can be stored, via a memory measuring unit ( 3 ), by which a state of charge of the at least two memory modules ( 7 ) and via a hybrid management ( 4 ), with which the loading of the memory modules ( 7 ) depending on the memory measuring unit ( 3 ) is controlled, characterized in that by the memory measuring unit ( 3 ) during a journey a difference between the charge states of the at least two memory modules ( 7 ) can be determined and when a maximum limit value for the difference of the charge states is exceeded, a warning signal can be generated on the basis of which the hybrid drive ( 1 ) during a driving time interruption of a driver automatically or manually by the driver in a Symmetrierungszustand can be transferred, in which the memory modules ( 7 ) by the of the internal combustion engine ( 5 ) driven motor / generator unit ( 6 ) are charged such that the difference in the charge states of the at least two memory modules ( 7 ) decreased. Motor vehicle according to claim 1, characterized in that the Symmetrierungszustand is maintained until the difference in the charge states of the at least two memory modules ( 7 ) is below an allowable tolerance value for the difference in charge states. Motor vehicle according to claim 1 or 2, characterized in that the warning signal from the memory measuring unit ( 3 ) or hybrid management ( 4 ) can be generated. Motor vehicle according to one of claims 1 to 3, characterized in that the warning signal is at least partially executed as an acoustically, optically and / or haptically perceptible signal in the area of the driver's workplace. Motor vehicle according to one of claims 1 to 4, characterized in that on the basis of the warning signal driver information on a provided in the driver's workplace display ( 8th ) can be displayed. Motor vehicle according to one of claims 1 to 5, characterized in that the hybrid drive ( 1 ) is converted into the Symmetrierungszustand despite an automatically or manually generated by the driver decommissioning request even before its decommissioning. Motor vehicle according to one of claims 1 to 6, characterized in that when exceeding a lower limit value lying below the maximum limit value for the difference of the charge states of the memory modules ( 7 ) is automatically converted into the Symmetrierungszustand within the driving time of the driver of the hybrid drive when a load request to the hybrid drive ( 1 ) one in hybrid management ( 4 ) does not exceed the stored load requirement limit value. Motor vehicle according to one of claims 1 to 7, characterized in that the memory modules ( 7 ) are designed as capacitors. Motor vehicle according to one of claims 1 to 8, characterized in that the internal combustion engine and the electrically operable motor / generator unit ( 6 ) are connected in parallel with respect to a vehicle drive train. Motor vehicle according to one of claims 1 to 9, characterized in that the internal combustion engine ( 5 ) is designed as a rotary engine, in particular as a microturbine. Motor vehicle according to one of claims 1 to 10, characterized in that at least one fuel cell unit is provided for generating electrical energy. Method for operating a motor vehicle with hybrid drive ( 1 ), in which a motor / generator unit ( 6 ) for generating electrical energy from an internal combustion engine ( 5 ), the generated electrical energy at least temporarily in at least two in series or parallel memory modules ( 7 ) of an energy store ( 2 ) is stored, at least temporarily, electrical energy from at least one of the memory modules ( 7 ) to the motor / generator unit ( 6 ) and in which by means of a memory measuring unit ( 3 ) a state of charge of the at least two memory modules ( 7 ) and loading the memory modules ( 7 ) by a hybrid management ( 4 ) is controlled in dependence on the state of charge, characterized in that by the memory measuring unit ( 3 ) during a journey a difference between the charge states of the at least two memory modules ( 7 ) is determined and when a maximum limit value for the difference of the charge states is exceeded, a warning signal is generated on the basis of which the hybrid drive is automatically or during a driving time interruption of a vehicle driver is manually transferred by the driver in a Symmetrierungszustand in which the memory modules by the of the internal combustion engine ( 7 ) driven motor / generator unit ( 6 ) are charged such that the difference in the charge states of the at least two memory modules ( 7 ) decreased. Method according to claim 12, that the symmetrization state is ended as soon as the difference of the charge states of the at least two memory modules ( 7 ) is below an allowable tolerance value for the difference in state of charge. A method according to claim 12 or 13, characterized in that the warning signal is executed as a perceptible to the driver signal, with which the driver of the transfer of the hybrid drive ( 1 ) is requested in the Symmetrierungszustand. Method according to one of claims 12 to 14, characterized in that in hybrid management ( 4 ) the maximum and a lower limit for each one difference of the charge state of the memory modules ( 7 ), wherein the lower limit value represents a smaller charge difference than the maximum limit value and that when the lower limit value is exceeded, the hybrid drive ( 7 ) is converted into the Symmetrierungszustand within the driving time of the driver as soon as and as long as a load request to the hybrid drive falls below a stored in hybrid management load request limit.

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