DE102022211108A1 - Energy transfer between electric vehicles - Google Patents

Abstract

A method for planning a transmission of electrical energy from an electrical donor vehicle (105) to an electrical recipient vehicle (110) comprises steps of: detecting (305) a planned journey of the recipient vehicle (110); determining (305) an amount of electrical energy to be transmitted to the recipient vehicle (110); detecting (310) planned journeys and amounts of electrical energy carried by a plurality of other vehicles (105) in the area of the recipient vehicle (110); determining (340) a cost value for an adapted journey of each of the other vehicles (105), wherein the adapted journey comprises a rendezvous with the recipient vehicle (110) and the transmission (360) of electrical energy; and selecting (345) one of the vehicles with the lowest possible cost value as the donor vehicle (105).

Description

The present invention relates to the transfer of electrical energy between electric vehicles. In particular, the invention relates to scheduling a transfer of electrical energy from a donor vehicle to a recipient vehicle.

A motor vehicle is designed to be powered by electrical energy. For this purpose, the vehicle comprises an electric drive motor and an electrical energy storage device. The electrical energy storage device has a predetermined capacity and is usually charged at a stationary charging station. In general, attempts are made to plan vehicle journeys in such a way that the electrical energy storage device is only emptied to the extent that a charging station can still be reached. Nevertheless, situations can arise in which the energy remaining in the electrical energy storage device is too low to reach the vehicle to a location where the storage device can be recharged. For example, a desired charging station may be defective or occupied, a charge level of the energy storage device may have been determined inaccurately, or the energy required to drive may be higher than expected.

It has been proposed to enable a transfer of electrical energy between two such motor vehicles in order to be able to drive such a vehicle under its own power again. To do this, electrical energy can be diverted from the energy storage unit of a first vehicle to the energy storage unit of the second vehicle. This requires that both vehicles are in the same place at the same time. Since such charging is not usually planned, a driver of an electric motor vehicle that happens to be in the same area can be asked to use his vehicle as a donor vehicle and to transmit electrical energy to the other vehicle as the recipient vehicle.

US 2014 0188 699 A1 proposes determining a suitable location where a donor vehicle and a recipient vehicle can meet and exchange electrical energy. To do this, routes followed by the two vehicles are compared and the location is determined at a point where the routes are as close as possible to each other.

Known methods for planning energy transfer between electric motor vehicles have proven to be inflexible and often start from a one-dimensional problem, so that a solution provided is not always optimal. The present invention is based on the object of providing an improved technique for planning energy transfer between electric vehicles. The invention solves this problem by means of the subject matter of the independent claims. Subclaims give preferred embodiments.

A method according to the invention for planning a transmission of electrical energy from an electrical donor vehicle to an electrical recipient vehicle comprises steps of detecting a planned journey of the recipient vehicle; determining an amount of electrical energy to be transmitted to the recipient vehicle; detecting planned journeys and amounts of electrical energy carried by a plurality of other vehicles in the area of the recipient vehicle; determining a cost value for an adapted journey of each of the other vehicles, the adapted journey comprising a rendezvous with the recipient vehicle and the transmission of electrical energy; and selecting one of the vehicles with the lowest possible cost value as the donor vehicle.

Based on a large number of vehicles that are considered as potential donor vehicles for a recipient vehicle, one can be selected for which the additional cost of providing electrical energy to the recipient vehicle is minimized. The cost value can be determined using a cost function. The cost function can take into account not only the additional cost for the donor vehicle but also the additional cost for the recipient vehicle.

A rendezvous is understood here to mean that a donor vehicle and a recipient vehicle go to a predetermined location at the same time to exchange electrical energy. The exchange usually takes place by laying an electrical connection between the two electrical vehicles. This connection can comprise an electrical cable.

The cost value determined using the cost function represents a value with which the optimization problem of selecting the most suitable vehicle as a donor vehicle can be solved. A large number of parameters can be included in the cost function, each of which should be minimized. A parameter to be maximized can, for example, be considered as a reciprocal. The individual parameters can be weighted and a weighting can be changed by a person who is assigned to the recipient vehicle or the donor vehicle.

A person associated with the donor vehicle may receive compensation for the energy transfer, which may be determined on the basis of the cost value. Typically, such compensation is determined in money and may be borne by a person associated with the recipient vehicle. Additional costs incurred in carrying out the procedure, such as rent for infrastructure for the transfer, may also be borne by this person.

Selecting one or more vehicles that are suitable as donor vehicles can be done using a mathematical optimization process. This can be done using a Monte Carlo method, a heuristic or optimization using graph theory.

In a particularly preferred embodiment, mixed integer linear optimization (Mixed Integer Linear Processing, MILP) is carried out. Using MILP or a variant, optimization can be carried out until either an optimal solution is found or the quality of a solution found no longer increases. For a solution found, it can be known how close it is to a theoretically achievable optimal solution.

A well-known software package can be used for optimization using MILP, for example CPLEX, COIN-OR, SCIP, Gurobi or GLPK. Boundary conditions and optimization criteria can be easily formulated. MILP optimization has proven itself in other practical applications when dealing with medium and large optimization problems.

Preferably, the optimization is carried out in such a way that cost values for the other vehicles are determined depending on a heuristically selected order. A vehicle for which a cost value is likely to be low can be checked before a vehicle whose cost value is likely to be higher. In this way, a high-quality solution associated with a low cost value can be found quickly. Such a heuristic can, for example, include a distance between the recipient vehicle and another vehicle and check vehicles located close to the recipient vehicle first. In addition, donor vehicles that cannot meet the energy requirements of the recipient vehicle can be removed early on from the set of vehicles suitable as donor vehicles.

In one embodiment, the cost value increases depending on the distance extended by the additional vehicle due to the change. The length of a route of the planned journey can be used as a reference. It can be taken into account that the additional vehicle can be driven from a current position to a predetermined target position on different routes.

A vehicle's route is generally based on a road network that is used as the basis for the determination. The route of the other vehicle adapted for the rendezvous can differ from an originally planned route, but can be of a similar length. The ability to adapt a route of another vehicle to carry out a rendezvous with the receiving vehicle can greatly reduce the burden on the other vehicle for the task of serving as a donor vehicle. Furthermore, the number of possible donor vehicles among the other vehicles can be significantly increased. Particularly when driving in urban areas, changing a planned route of the receiving vehicle or another vehicle can lead to the discovery of a donor vehicle whose additional route-related effort is small compared to its planned route.

In a further embodiment, the cost value increases depending on the arrival time of the additional vehicle at a destination of the planned journey being delayed due to the change. It can be taken into account that the process of transferring electrical energy between the vehicles takes a certain amount of time. This time can depend on the amount of electrical energy to be transferred and a minimum of electrical power that the donor vehicle can provide and an electrical power that the receiving vehicle can absorb. A transfer can take just a few minutes or take a longer time in the range of an hour or more.

A trip planned with the additional vehicle can also be brought forward in time to enable the energy transfer. In a further embodiment, the cost value increases depending on an earlier departure time of the additional vehicle from a starting point of the planned trip due to the change.

This variant can also be used if a trip with the other vehicle is not planned in the foreseeable future. For optimization purposes, this can be modulated as a trip along a route of zero length. A time of the trip can be assumed to be a predetermined point in time in the future. This point in time can always be a predetermined time, for example 30 minutes. so that an extraordinary journey to the rendezvous location is reflected in the cost function by an earlier departure time of 30 minutes and a detour of the distance that has to be covered from the current position of the additional vehicle to the rendezvous location. This distance can be counted twice if the additional vehicle is to be driven back to the original location after the rendezvous.

The cost value can be determined on the basis of supply and demand. This can better motivate a person who is responsible for another vehicle to use the additional vehicle as a donor vehicle. Optionally, a professional donor vehicle can be used, the purpose of which is to supply energy-intensive recipient vehicles with electrical energy. This variant enables commercial use of a conventional electric motor vehicle. Optionally, the vehicle can be equipped with an enlarged electrical energy storage unit in order to be able to better fulfill its role as a donor vehicle. The vehicle can also include a generator for providing electrical energy, for example from a fuel cell or an internal combustion engine.

In one embodiment, the cost value decreases with an increasing number of vehicles whose cost values are similar to the lowest cost value. In such a case, the supply can be considered high. If there is a strong demand in which several receiving vehicles in a predetermined area are interested in electrical energy, the supply can decrease again and the cost value increase accordingly.

It is also preferred that the cost value increases with the amount of energy requested. The requested energy is the amount of energy that is to be transferred to the base vehicle. In this way, a small-scale energy transfer can be promoted according to the method. Such a transfer can occur, for example, due to a defective charging station, an inaccurate consumption forecast or unfavorable traffic conditions, even with careful planning.

It is possible to create or adjust the cost value using a bidding process that evaluates the existing supply and demand. People assigned to the vehicles can participate and negotiate a price for an energy transfer. The price can be part of the cost factor or vice versa.

A journey runs from a starting point to a destination. A point in time of the journey can refer to the departure from the starting point or a desired arrival at the destination. A route that is to be taken on the planned journey from the starting point to the destination can be taken into account for determining the location of the rendezvous. However, it is preferred that the choice of a route is considered free so that the route can be determined as part of the solution of the optimization problem described.

In general, it is preferred that only those additional vehicles are considered as candidates for donor vehicles that can still reach a destination of the respective planned journey after they have carried out a rendezvous with the recipient vehicle and have transferred a predetermined amount of electrical energy to the recipient vehicle.

The electrical energy transmitted can correspond to the amount of energy that is to be transmitted to the receiving vehicle. Conversely, the amount of energy transmitted can also be determined in such a way that the other vehicle can still reach the predetermined destination after it has been delivered.

For example, if this amount does not reach the amount of electrical energy to be transferred to the recipient vehicle, multiple energy transfers to the recipient vehicle can also be planned. In one embodiment, a first energy transfer from a first donor vehicle to the recipient vehicle and a second energy transfer from a second donor vehicle to the recipient vehicle are planned. In this way, the predetermined amount of electrical energy can be provided for the recipient vehicle, even if no donor vehicle can provide this amount of energy in just one transfer. In a corresponding manner, more than two energy transfers from different donor vehicles can also be planned.

Several energy transfers can take place at one location or at different locations. If two energy transfers take place at the same location, they can take place one after the other in a first variant and simultaneously or overlapping in a second variant. This can prevent the receiving vehicle, which already needs energy, from using additional electrical energy to travel to different locations for rendezvous. If energy transfers are carried out at different locations, energy that is needed to drive the receiving vehicle from one location to the other of the rendezvous can be used. vous required must be taken into account when determining a requested amount of energy.

In a further embodiment, a location for the rendezvous can be determined depending on a requirement or preference of a person on board the receiving vehicle or the donor vehicle. For example, one of the people may be interested in carrying out the transfer in a busy or well-lit location. Other possible requirements may include the presence of a restaurant, a toilet or an entertainment outlet such as a cinema. A shopping facility or a kiosk may also be required as existing infrastructure. This can ensure that the energy transfer takes place under circumstances that are perceived as risky or unpleasant for the person. Furthermore, the person can advantageously combine an activity that they would carry out during a normal break in the journey with the energy transfer.

Conversely, the receiving vehicle can enable particularly convenient charging of the energy storage device by stopping at a location considered convenient while simultaneously transferring energy from a donor vehicle. The energy transfer can, for example, be deliberately planned for a location where the receiving vehicle is to be stopped anyway, such as a restaurant or public place. A service for charging the energy storage device can be booked for the predetermined location, so to speak.

A location for the rendezvous is preferably determined in such a way that the transfer of electrical energy is physically and/or legally possible. For this purpose, it can be determined that a technical infrastructure required for the exchange is available, for example an electricity meter, a converter or an adapter. For example, both vehicles can head for a public or private parking lot or stop at the side of the road. The vehicles can also visit a predetermined infrastructure that supports the exchange of electrical energy. Such infrastructure can, for example, include a charging station or a similar device that enables, facilitates or participates in the energy transfer. A place where stopping or getting off is not permitted, for example a motorway, cannot be determined for a rendezvous. Likewise, when choosing the location, it can be taken into account that the energy transfer across a predetermined facility, for example a property boundary or between two lanes in different directions, is not permitted.

In a further embodiment, a first energy transfer from a first donor vehicle to the recipient vehicle and a second energy transfer from a second donor vehicle to the first donor vehicle are planned. As part of the second energy transfer, the first donor vehicle can act as a further recipient vehicle.

This can prevent the first donor vehicle from being unable to reach its planned destination because it has provided too much energy to the recipient vehicle. The second energy transfer preferably takes place at a location that is between the location of the first energy transfer and the destination of the first donor vehicle. In a similar way, the first donor vehicle can also draw energy from several other donor vehicles at different locations one after the other. This can ensure that none of the vehicles involved in the process cannot reach a predetermined destination or even becomes immobile.

A central location for planning a transmission of electrical energy from an electrical donor vehicle to an electrical recipient vehicle comprises a communication device for communicating with a recipient vehicle and a plurality of other vehicles, as well as a processing device. The processing device is designed to receive a planned journey of the recipient vehicle, to determine an amount of electrical energy to be transmitted to the recipient vehicle; to receive planned journeys and amounts of electrical energy carried by a plurality of other vehicles in the area of the recipient vehicle; to determine cost values for adapted journeys of the other vehicles, wherein the adapted journeys each comprise a rendezvous with the recipient vehicle and the transmission of electrical energy; and to select one of the other vehicles with the lowest possible cost value as the donor vehicle.

The processing device can be set up to carry out a method described herein in whole or in part. For this purpose, the processing device can be implemented electronically and comprise a programmable microcomputer or microcontroller. The method can be in the form of a computer program product with program code means. The computer program product can also be stored on a computer-readable data carrier. Features or advantages of the method can be transferred to the central location or vice versa.

The central location can be provided in particular as a server or service in a cloud. Vehicles that participate in the described method can be part of a predetermined vehicle fleet.

According to yet another aspect of the present invention, a system comprises a central location as described herein and a plurality of electric vehicles that communicate with the central location and can each participate in a transfer of electrical energy between two electric vehicles as a donor vehicle or as a recipient vehicle.

• 1 ein System mit einem ersten Fahrzeug, einem zweiten Fahrzeug und einer zentralen Stelle;
• 2 beispielhafte Routen zweier Fahrzeuge und mögliche Orte für ein Rendezvous; und
• 3 ein Ablaufdiagramm eines Verfahrens darstellt.

The invention will now be described in more detail with reference to the accompanying figures, in which:

• 1 a system comprising a first vehicle, a second vehicle and a central location;
• 2 exemplary routes of two vehicles and possible locations for a rendezvous; and
• 3 represents a flow chart of a procedure.

1 shows a system 100 with a first vehicle 105, another vehicle 110 and a central location 115. The two vehicles 105, 110 are electric vehicles, of which the first vehicle 105 is shown as a donor vehicle and the second vehicle 110 as a recipient vehicle in a transmission of electrical energy.

The receiving vehicle 110 comprises an electric drive machine 120, which can be operated using energy taken from an electrical energy storage device 125 carried along. An interface 130 is provided for transmitting electrical energy between the energy storage device 125 and a device outside the receiving vehicle 110. In the illustration of 1 the interface 130 is connected to the donor vehicle 105 by an electrical transmission cable 135.

Furthermore, a processing device 140 is preferably provided on board the receiving vehicle 110, which is designed to determine an amount of energy stored in the energy storage device 125. The processing device 140 can be used to plan a journey of the receiving vehicle 110 by offsetting an expected consumption of electrical energy on a predetermined route between a starting point and a destination with the energy stored in the energy storage device 125. Conversely, a route or a destination can also be determined depending on an available amount of electrical energy in the energy storage device 125. Communication with the donor vehicle 105 or the central location 115 can be carried out by means of a communication device 145.

The donor vehicle 105 is preferably constructed essentially in the same way as the recipient vehicle 110. It can also comprise the same components and these can be connected to one another in the same way. However, while the recipient vehicle 110 can usually only be moved by means of the electric drive motor 120, the donor vehicle 105 can also comprise a further drive motor, which can in particular be designed as an internal combustion engine. In this case, the electric drive motor 120 can also be omitted, although the electrical energy storage device 125 is retained.

The central location 115 comprises a processing device 150, a communication device 155 and an optional data memory 160. It is proposed that the central location 115 is configured to communicate with a plurality of vehicles 105, 110 and to receive charging levels and planned journeys of the vehicles 105, 110.

If the receiving vehicle 110 requires electrical energy that it cannot obtain from a fixed infrastructure, the central location 115 can determine a donor vehicle 105 that can provide electrical energy to the receiving vehicle 110 on the basis of the received data and optionally further data. For this purpose, a transmission process for electrical energy can be planned that includes a rendezvous of the vehicles 105, 110 at a predetermined location.

2 shows exemplary routes of two vehicles 105, 110 in an exemplary representation. A planned trip of the first vehicle 105 leads from a first starting point 205 to a first destination 210, for which a first route 215 is determined. In a corresponding manner, a trip is planned for the second vehicle 110, which leads from a second starting point 225 to a second destination 230, for which a second route 235 is determined.

To illustrate a procedure proposed here, the two routes 215, 220 run approximately antiparallel, with a predetermined obstacle 240 being avoided in each case. The obstacle 240 can, for example, comprise a residential area, an old town or a traffic-calmed area. The routes 215, 235 run on opposite sides of the obstacle 240.

In order to enable a transfer of electrical energy between the vehicles 105 and 110, a rendezvous must be carried out, at which both vehicles 105, 110 are at the same place at the same time. In a naive approach, such a location can be provided where the routes 215, 235 are at a minimal distance from one another. In the present example, this condition is met, among other things, by a first location 245 in the area of the first starting location 205 and a second location 250 in the area of the second starting location 225. In order to meet at the first location 245, the donor vehicle 105 would have to wait until the recipient vehicle 110 has completely covered the route there. Similarly, the recipient vehicle 110 would have to wait at the second location 250 until the donor vehicle 105 has completely covered the route there in order to be able to carry out the energy transfer there.

However, one of the routes 215, 235 can be changed to determine a more advantageous location for a rendezvous. For example, the donor vehicle 105 can go around the obstacle 240 to the left rather than to the right as planned, so that a third location 255 comes into consideration for a rendezvous. The third location 255 can be approximately the same distance away from both vehicles 105, 110 or can be reached in approximately the same time. When the third location 255 is selected, a waiting time for one of the vehicles 105, 110 for the other vehicle 105, 110 can be minimized.

In a corresponding manner, the receiving vehicle 110 can alternatively change its route 235 and pass the obstacle 240 not on the right but on the left, so that a rendezvous can take place at a fourth location 260 in a corresponding manner.

In the idealized configuration shown, none of the vehicles 105, 110 may have to take an additional route to carry out the rendezvous, and the waiting time until the other vehicle 105, 110 arrives may be zero. In practice, such small additional burdens for carrying out a rendezvous are usually not achievable. Nevertheless, changing one or both routes 215, 235 of the vehicles 105, 110 can contribute substantially to minimizing the time or route required for carrying out a rendezvous between the vehicles 105, 110.

3 shows a flow chart of a method 300 for planning an energy transfer between two vehicles 105, 110. The method 300 can select a donor vehicle 105 from a plurality of other vehicles for an energy requirement of a recipient vehicle 110.

Through the process of selection, a general vehicle can become a donor vehicle 105. The recipient vehicle 110 is usually defined by providing a request to accept electrical energy from a donor vehicle 105. This request is usually transmitted from the recipient vehicle 110 to the central location 115 and processed there.

Steps of the method 300 that can be assigned to the recipient vehicle 110 are shown as examples in a left-hand area; those that can be assigned to a vehicle that can become the donor vehicle 105 are shown in a right-hand area.

In a step 305, a planned trip and a required amount of energy of the receiving vehicle 110 can be determined. The planned trip includes at least the second starting location 225 and the second destination 230. Optionally, the second route 235 can also be specified. This information can be transmitted to the central location 115.

Similarly, in a step 310, information about a planned trip and an available amount of energy on board another vehicle 105 can be determined and transmitted to the central location 115. The planned trip includes at least the first starting location 205 and the first destination 210. Optionally, the first route 215 can also be included. The available energy can relate to the electrical energy available on board the first vehicle 105 or the electrical energy that can be delivered from the first vehicle 105 to the receiving vehicle 110.

In a step 315, a rendezvous can be determined on the basis of the information received. The rendezvous is assigned a location 245 - 260, which can also be determined. Determining a location 245 - 260 can include changing or advantageously creating a route 215, 235 of the first vehicle 105 and/or the second vehicle 110 with respect to a predetermined road network. The location 245 - 260 is preferably determined in such a way that the time, energy or route expenditure for carrying out the rendezvous for the first vehicle 105 and/or the second vehicle 110 is minimized compared to the respective planned journey. A successful minimization in this regard is described herein with reference to 2 described as an example.

In a step 320, a modified route can be determined for the modified journey of the second vehicle 110. Time and/or a changed energy for reaching the associated destination 230 can be determined. In a corresponding manner, a changed time and/or a changed energy for reaching the first destination 210 can be determined for the first vehicle 105 in a step 325 with respect to the changed journey.

In a step 330, a demand of the receiving vehicle 110 can be determined. The demand can include an urgency with which the second vehicle 110 is interested in transmitting the requested electrical energy. Conversely, in a step 335, an offer for the first vehicle 105 to participate in a rendezvous with energy transmission can be determined. The offer can express a willingness to participate in the rendezvous. The willingness can be determined, for example, by personal reasons, an offered compensation or with respect to a predetermined condition.

On the basis of the determined information, a cost value can be determined in a step 340. The cost value can, on the one hand, take into account the expenditure of the first vehicle 105 and/or the second vehicle 110 for carrying out the rendezvous and, on the other hand, take into account supply and demand. A large number of parameters associated with carrying out a rendezvous, the transmission of energy or with the resulting expenditure can flow into the cost value. On the basis of the determined cost value, compensation can be determined, which can usually be paid out in the form of money to a person who is assigned to the donor vehicle 105. These costs can be borne by a person who is assigned to the recipient vehicle 110.

However, these costs may differ from the specific cost value with respect to which a selection of one of the first vehicles 105 may be made in a step 345. During the selection, one or more first vehicles 105 with the lowest possible associated cost values may be identified.

A rendezvous proposed with respect to a first vehicle 105 can be confirmed in a step 350 by the second vehicle 110 and in a step 355 by the first vehicle 105. The confirmation can be obtained in particular from an assigned person. If confirmation cannot be obtained, another vehicle can be sought that is suitable as a donor vehicle 105.

In a step 360, the energy transfer between the vehicles 105, 110 can be carried out. For this purpose, parameters for carrying out the specific rendezvous can be transmitted to the vehicles 105, 110. The parameters can be evaluated automatically or by a driver in order to carry out the planned rendezvous.

For this purpose, the vehicles 105, 110 can each be controlled to the specific location of the rendezvous, optionally taking into account a time assigned to the rendezvous. Furthermore, the vehicles 105, 110 can be connected to one another in a suitable manner and electrical energy can be transmitted from the donor vehicle 105 to the recipient vehicle 110. After the transmission has been completed, the vehicles 105, 110 can be separated from one another again and leave the location of the rendezvous.

Reference symbols

100

system

105

first electric vehicle, donor vehicle

110

second electric vehicle, receiving vehicle

115

central location

120

electric drive machine

125

electrical energy storage

130

interface

135

electrical transmission cable

140

Processing facility

145

Communication facility

150

Processing facility

155

Communication facility

160

Data storage

205

first starting point

210

first destination

215

first route

225

second starting point

230

second destination

235

second route

240

obstacle

245

first place

250

second place

255

third place

260

fourth place

300

Proceedings

305

planned journey, determine the amount of energy required by the receiving vehicle

310

planned journey, determine available amount of energy of the donor vehicle

315

Determine a location for a rendezvous

320

Determine changed journey, changed time, changed energy for the recipient vehicle

325

Determine changed journey, changed time, changed energy for the donor vehicle

330

Determine demand

335

Determine offer

340

Determine cost value

345

Make selection

350

Obtain consent from the recipient vehicle

355

Obtain consent from the donor vehicle

360

Carry out energy transfer

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was 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 accepts no liability for any errors or omissions.

Cited patent literature

• US 20140188699 A1 [0004]

Claims (16)

Method (300) for planning a transmission of electrical energy from an electrical donor vehicle (105) to an electrical recipient vehicle (110), the method (300) comprising the following steps: detecting (305) a planned journey of the recipient vehicle (110); determining (305) an amount of electrical energy to be transmitted to the recipient vehicle (110); detecting (310) planned journeys and amounts of electrical energy carried by a plurality of further vehicles (105) in the area of the recipient vehicle (110); for each of the further vehicles (105): determining (340) a cost value for an adapted journey of the further vehicle (105), which includes a rendezvous with the recipient vehicle (110) and the transmission (360) of electrical energy; and selecting (345) one of the vehicles (105) with the lowest possible cost value as the donor vehicle (105). Procedure (300) according to Claim 1 , wherein the selection (345) is carried out by means of a mathematical optimization method. Procedure (300) according to Claim 1 or 2 , whereby the cost value increases depending on the distance extended for the additional vehicle due to the change. Method (300) according to one of the preceding claims, wherein the cost value increases as a function of a delayed arrival time of the further vehicle at a destination (210) of the planned journey due to the change. Method (300) according to one of the preceding claims, wherein the cost value increases as a function of an earlier departure time of the further vehicle (105) at a starting location (205) of the planned journey due to the change. Method (300) according to one of the preceding claims, wherein the cost value decreases with an increasing number of vehicles whose cost values are similar to the lowest cost value. Method (300) according to one of the preceding claims, wherein the cost value increases with the amount of energy requested. Method (300) according to one of the preceding claims, wherein a journey comprises a starting location (205, 225) and a destination (210, 230), between which a route (215, 235) is determined with respect to a predetermined route network. Method (300) according to one of the preceding claims, wherein only those further vehicles are taken into account which can still reach a destination of the respectively planned journey after they have carried out a rendezvous with the receiving vehicle (110) and have transmitted electrical energy to the receiving vehicle (110). Method (300) according to one of the preceding claims, wherein a first energy transfer (360) from a first donor vehicle (105) to the recipient vehicle (110) and a second energy transfer (360) from a second donor vehicle (105) to the recipient vehicle (110) are planned. Method (300) according to one of the preceding claims, wherein a first energy transfer from a first donor vehicle (105) to the recipient vehicle (110) and a second energy transfer from a second donor vehicle (105) to the first donor vehicle (105) are scheduled. Method (300) according to one of the preceding claims, wherein two energy transfers (360) are planned at the same location. Method (300) according to one of the preceding claims, wherein a location for the rendezvous is determined in dependence on a request of a person on board the receiving vehicle (110) or the donor vehicle (105). Method (300) according to one of the preceding claims, wherein a location for the rendezvous is determined depending on an infrastructure required for the exchange. Central location (115) for planning a transmission of electrical energy from an electrical donor vehicle (105) to an electrical recipient vehicle (110), the location comprising a communication device (155) for communicating with a recipient vehicle (110) and a plurality of other vehicles (105); and a processing device (150), the processing device (150) being configured to receive a planned journey of the recipient vehicle (110); to determine an amount of electrical energy to be transmitted to the recipient vehicle (110); to receive planned journeys and amounts of electrical energy carried by a plurality of other vehicles in the area of the recipient vehicle (110); to determine cost values for adapted journeys of the other vehicles, the adapted journeys each comprising a rendezvous with the recipient vehicle (110) and the transmission of electrical energy; and to select one of the other vehicles with the lowest possible cost value as the donor vehicle (105). System (100) comprising a central location (115) according to Claim 15 and a plurality of electric vehicles (105, 110) which communicate with the central location (115) and can each participate in a transfer of electrical energy between two electric vehicles (105, 110) as a donor vehicle (105) or as a recipient vehicle (110).

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