How to charge the battery via a charging station

Abstract

The invention relates to a method for charging a battery (12) installed in a motor vehicle (10), the motor vehicle being electrically connected to a charging station (20), the method comprising the following steps: - receiving data relating to the variation over time of the electric power available at the charging station and the variation over time of the electricity cost; and - selecting a time period when the electricity cost is the lowest. According to the invention, the charging method further comprises the following steps: - estimating the temperature that the battery will have during the time period and the state of charge that the battery will have before the time period, - determining the temperature of the battery at the charging station during the time period (δt i ) during a period of time, deriving a new state of charge of the battery at the end of the time period, comparing the new state of charge with a target state of charge, and charging the battery accordingly.

Description

Technical Field

[0001] The present invention generally relates to charging batteries for electric vehicles.

[0002] More specifically, the invention relates to a method for charging a battery equipped with a motor vehicle by means of a charging station.

[0003] The invention also relates to a motor vehicle designed to implement the charging method.

[0004] More particularly, the present invention is applicable to electric vehicles. Background Art

[0005] Electric vehicles typically include a large capacity battery that allows current to be supplied to an electric motor provided for propelling the vehicle.

[0006] Such batteries must be charged regularly. One solution to this is to connect the car electrically to a public charging station.

[0007] Therefore, the ISO 15118 standard has been developed to define a standard communication protocol between a charging station and any car capable of connecting to the charging station.

[0008] In order to optimize the energy management in the grid, the vehicle must use the possibilities offered by the standard in a way that complies with three main constraints. The first constraint is to ensure that the user's battery is sufficiently charged when the user wants to set off. The second constraint is not to overestimate the user's needs so as not to monopolize the power available at the charging station unnecessarily. The third constraint is to impose a fairly short time frame on the car after it has been connected to the charging station, at the end of which the car must communicate to the charging station when and with what electrical power the charging station must charge the car's battery.

[0009] The protocol used provides that the charging station transmits, when connected to a motor vehicle, information about the temporal variation of the electric power available at the charging station and of the electricity price level (typically off-peak / peak time information items).

[0010] Therefore, one known method for selecting a time period during which a charging station is required to charge the battery is to select the nearest off-peak time period.

[0011] Unfortunately, this approach does not ensure that the user's vehicle will be ready to depart at the desired time.

[0012] One solution to overcome this drawback could be to ask the user what time they would like to depart, and to choose a time period so that the charging costs are as low as possible and the vehicle is fully charged at the departure time.

[0013] However, this solution would require that the vehicle be able to predict the progression of the battery's state of charge based on the selected time periods and the electrical power available during each of those time periods.

[0014] To this end, a method for calculating the progress of the charge state of a battery is known from document CN 103020445, but this method requires the use of a computer with high computing power in order to be able to determine which time periods are to be obtained and how much electrical power is to be reserved during the time allotted by the ISO 15118 standard. This solution is therefore very costly to implement. Summary of the invention

[0015] In order to overcome the above-mentioned disadvantages of the prior art, the present invention proposes a simpler method for calculating the change of charging power over time.

[0016] More specifically, according to the present invention, a charging method is proposed, the method comprising the following steps:

[0017] a) receiving data relating to changes over time in the electrical power available at the charging station and changes over time in the cost of electricity,

[0018] b) Selecting a time period when the available electric power is not zero and the electricity fee is the lowest,

[0019] c) estimating the temperature that the battery will have during the time period and the state of charge of the battery at the beginning of the time period,

[0020] d) determining the electrical power that the charging station will be able to transfer to the battery during the time period based on the temperature and the state of charge estimated in step c),

[0021] e) deriving a new state of charge of the battery at the end of the time period based on the electrical power determined in step d),

[0022] f) comparing the new state of charge to a target state of charge, and then, if the new state of charge is higher than or equal to the target state of charge,

[0023] g) charging the battery with the electrical power by means of the charging station during the time period.

[0024] The invention thus proposes a method that is easy to implement, requires little computing power and makes it possible to assess with the required accuracy which time slots should be booked at a charging station to ensure that charging is as cheap as possible given the planned departure time of the vehicle and the electrical power available from the charging station.

[0025] Other advantageous and non-limiting features of the charging method according to the invention are as follows:

[0026] - if the new state of charge is lower than the target state of charge, repeating steps b) to e) for an additional period of time and in step f) comparing the target state of charge with the state of charge that the battery will have after these two periods of time;

[0027] - in step a), obtaining a departure time at which the motor vehicle is scheduled to disconnect from the charging station, and in step b), the selected time period is before the departure time;

[0028] - during the repetition of steps b) to e), determining the electrical power that the charging station will be able to transmit to the battery during each of these time periods and then deriving therefrom the change in the state of charge of the battery until the departure time;

[0029] - In step b), if the electricity rate is the lowest in several time periods, the time period selected from these time periods is the earliest time period;

[0030] - before step a), determining an instantaneous state of charge of the battery, comparing the instantaneous state of charge with a state of charge threshold, and if the instantaneous state of charge is lower than the state of charge threshold, charging the battery during a first time period when the available electrical power is not zero;

[0031] - in step c), estimating the temperature of the battery based on a predetermined mathematical model or a predetermined map;

[0032] - in step d), to determine the electric power, the lowest electric power is selected from the electric power available at the charging station during the selected time period and the maximum electric power allowed for the motor vehicle, the maximum allowed electric power being determined on the basis of the temperature and the state of charge estimated in step c);

[0033] - In step e), the energy that will have been stored in the battery at the end of the time period is calculated and then the new state of charge is derived therefrom.

[0034] The invention also relates to a motor vehicle comprising at least one electric drive motor, a battery designed to supply electric current to each electric motor, and a computer programmed to implement a charging method as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The following description, made with reference to the accompanying drawings, given by way of non-limiting examples, will provide a better understanding of what the invention is and how it can be implemented.

[0036] In the attached picture:

[0037] - Figure 1is a schematic view of a charging station and a motor vehicle according to the invention;

[0038] - Figure 2A is a graph illustrating an example of the variation of available electrical power at a charging station over time;

[0039] - Figure 2B and Figure 2C is with Figure 2A , and illustrates how to select a time period with respect to a charging station;

[0040] - Figure 3A is a graph showing an example of the change in the electricity rate provided at a charging station over time;

[0041] - Figure 3B and Figure 3C is with Figure 3A , and illustrates how to select a time period with respect to a charging station;

[0042] - FIG. 4A to FIG. 4D is a graph showing four time periods of successive bookings to a charging station;

[0043] - Figure 5 It is shown Figure 1 A graph showing the maximum power that a battery of a vehicle can receive as a function of the state of charge of the battery, the graph also showing the maximum power that a charging station can deliver and the maximum power that a charger of a motor vehicle can receive;

[0044] - Fig. 6A , Figure 6B and Figure 6C are graphs showing changes in the electricity cost provided by the charging station, the state of charge of the battery of the motor vehicle, and the electric power consumed from the charging station over time; and

[0045] - Figure 7 is a flow chart showing a charging method according to the present invention. DETAILED DESCRIPTION

[0046] Figure 1 An electric vehicle is shown.

[0047] In this case, it is a car, but it could also be another type of motor vehicle (motorcycle, truck, boat, etc.).

[0048] Here the car is described as being electric in the sense that it does not include an internal combustion engine. As a variant, the car may be a plug-in hybrid vehicle.

[0049] The electric vehicle 10 generally includes a chassis and wheels. More specifically, in this case, it includes:

[0050] at least one electric motor 11 which allows the electric vehicle 10 to move,

[0051] a battery (hereinafter referred to as traction battery 12 ) connected to each electric motor 11 in order to supply electric current to the electric motor,

[0052] - auxiliary equipment 13, which consumes current (air conditioning, multimedia console, etc.),

[0053] - a charger 14, and

[0054] -Computer 15.

[0055] The charger 14 comprises a power socket to which a power plug of the charging station 20 can be connected.

[0056] The charger is connected to the traction battery 12 in order to charge the traction battery. In the present case, the charger is also connected to the auxiliary equipment 13 in order to be able to supply current to the auxiliary equipment when the electric vehicle 10 is connected to the charging station 20.

[0057] The computer 15 further includes a processor (CPU), a memory, and various input and output interfaces.

[0058] By means of the computer's input and output interfaces, the computer is designed to receive input signals from sensors or other devices. In particular, the computer is designed to receive the instantaneous state of charge SOC0 of the traction battery 12 .

[0059] The computer is also designed to communicate with the charging station 20 via the charger 14 in order to receive the electrical power P available at the charging station 20. 20 Changes over time and electricity costs C 20 Data about changes over time.

[0060] The computer is also designed to communicate with this same charging station 20 in order to reserve a time period for charging the vehicle by selecting a charging power.

[0061] By means of the memory of the computer 15 , the computer stores the data used during the method described below.

[0062] In particular, the memory stores computing applications consisting of computer programs comprising instructions that are executed by the processor to allow the computer 15 to implement Figure 7 The charging method shown in and described below.

[0063] If the Figure 7As shown in , the charging method includes eleven main steps that can be repeated cyclically.

[0064] The method is specifically designed to allow the charging station 20 to charge the traction battery 12 during certain time periods that ensure the traction battery 12 of the user's electric vehicle 10 will be fully charged when the user needs it and minimize the cost of the charging operation.

[0065] The method is automatically initiated when the electric car 10 is connected to the charging station 20 .

[0066] The first step EA0 of the method is to check that the traction battery 12 is not over-discharged, which could lead to premature discharge of the battery.

[0067] To this end, during this first step EA0, the computer 15 records the instantaneous state of charge SOC0 of the traction battery 12. In the present case, this instantaneous state of charge SOC0 is transmitted to the computer 15 by a third party processor in charge of calculating this state of charge. As a variant, this instantaneous state of charge can be calculated by the computer 15 based on the voltage across the terminals of the traction battery 12.

[0068] Then, the computer 15 compares the instantaneous state of charge SOC0 with a predetermined state of charge threshold SOC min For comparison, the predetermined state of charge threshold is fixed and recorded in the read-only memory of the computer. min Preferably, it is between 10% and 30%. In this case, the charge state threshold is equal to 20%.

[0069] If the instantaneous state of charge SOC0 is higher than or equal to the state of charge threshold SOC min , which means that there is no risk of premature discharge of the traction battery 12 , the method then continues with step EA1 , as described below.

[0070] Otherwise, the computer 15 sends a request to the charging station 20 to charge the traction battery 12 during the first available time period until the instantaneous state of charge SOC0 reaches the state of charge threshold SOC min Once the threshold is reached, the method continues with step EA1.

[0071] During a second step EA1 , the computer 15 determines the departure time of the electric vehicle 10 , ie the time at which the electric vehicle is to be disconnected from the charging station 20 .

[0072] In this case, the computer 15 not only obtains the departure time, but also obtains the target state of charge SOC that the traction battery 12 must reach by then. N .

[0073] To this end, the computer 15 may ask the user, for example via a dedicated human-machine interface, when they would like to depart and what their desired destination is.

[0074] By taking the desired destination into account, the computer 15 will be able to determine the target state of charge SOC that the traction battery 12 must reach. N , to allow the user to reach that destination.

[0075] As a variant, the computer 15 may automatically determine the time and destination at which the vehicle will depart, for example by detecting that the user always uses their electric car 10 to go to work every weekday.

[0076] During step EA1 , the computer 15 also receives from the charging station 20 the electrical power P available at the charging station 20 . 20 Changes over time and electricity costs C 20 Data about changes over time.

[0077] For example, the computer receives a signal indicating the available electrical power P at the charging station 20. 20 A graph of changes over time. Figure 3A Displayed graphically in .

[0078] The computer also receives a graph showing the change in the price level of electricity provided by the charging station 20 over time. Such a graph is Figure 2A In this case, it can be observed that the price level varies between four different values. It goes without saying that the number of price levels may vary from one electricity supplier to another.

[0079] In the present case, the graphs received by the computer 15 show the price level changes within 24 hours. As a variant, these graphs can show the price level changes within different periods (for example, until the departure time of the vehicle).

[0080] Once received by the computer 15, these graphs are discretized here in 15-minute steps. To this end, the electricity cost C in each 15-minute step is 20 The highest value is used as the electricity cost C during this 15-minute step period 20 In addition, the available electric power P in each 15-minute step is 20 The lowest value is used as the available electrical power P during this 15-minute step 20 The unique value of .

[0081] Then, if the departure time is more than 24 hours from now, the method continues with step EB1, as described below.

[0082] Otherwise, the map is redefined to prevent a time period after the departure time from being selected for charging the electric vehicle 10 .

[0083] Therefore, the electricity cost C in each time period after the departure time is 20 is fixed to a very high value, such as 10 10 Euro (see Figure 2B ). Additionally or as a variant, the electrical power P available to the charging station 20 in each time period after the departure time 20 is fixed to zero (see Figure 3B ).

[0084] As a variant, the diagram may be redefined by taking into account a safety margin of, for example, one hour, to ensure that the vehicle is charged one hour before the planned departure time.

[0085] Once the graph has been redefined, the method continues with step EB1.

[0086] The third step EB1 is to select the latest time period δt for which it is recommended to charge the traction battery 12 i .

[0087] To this end, the computer 15 selects the available electrical power P 20 Not zero, and the electricity cost C 20 The lowest most recent time period δt i .

[0088] Then, during a fourth step EB2, the computer 15 updates the diagram in order to avoid a subsequent reselection of the same time period δt i .

[0089] To this end, during this time period δt i Electricity charges during the period C 20 is fixed to a very high value, such as 10 10 Euro (see Figure 2C ). Additionally or as a variant, during the time period δt i The electric power P available from the charging station 20 during 20 is fixed to zero (see Figure 3C ).

[0090] The next step would then be to estimate the traction battery 12 over the selected time period δt i The power state SOC that should be presented at the end i+1 , so that the check is performed only during the time period δt i During this time, the traction battery 12 is charged, and whether the user will be able to reach the desired destination.

[0091] To this end, during a fifth step EC1 , the computer 15 estimates the current flow of the traction battery 12 during the selected time period δt iThe temperature T that will be present at the time (the moment considered may be the beginning of the time period or any other moment during the time period, such as the middle of the time period) i .

[0092] This temperature T can be estimated based on a predetermined mathematical model or a predetermined diagram made on a test bench. i .

[0093] In this case, the computer 15 uses the following mathematical model to calculate the temperature T i :

[0094]

[0095] in:

[0096] MCp, R, Rthext and Rth(Qm) are thermal constants that depend on the chemistry of the traction battery 12,

[0097] -Text is the ambient temperature,

[0098] - Tair is the temperature to which the system will heat / cool the traction battery 12 (if the system is activated), and

[0099] I is the current intensity of the traction battery 12 .

[0100] The computer 15 then estimates that the traction battery 12 is i The power state SOC that will be presented at the beginning i .

[0101] In this case, the state of charge SOC i is equal to the instantaneous state of charge SOC0. As a variant, this may be different from the above case if the traction battery 12 is intended to be used to supply auxiliary devices 13 consuming current.

[0102] During a sixth step ED1 , the computer 15 calculates the i The electric power P allowed by the traction battery 12 during max12 .

[0103] The permissible electrical power P max12 Based on the previously estimated temperature T i and state of charge SOC i to be sure.

[0104] like Figure 5 As shown by the curve C1 in FIG. 1 , the power actually varies with the state of charge SOC of the traction battery 12 , and the higher the state of charge SOC, the lower the power.

[0105] Permissible electrical power P max12It also varies with the temperature of the traction battery 12 , the higher the temperature T the lower the electrical power.

[0106] In order to determine the permissible electrical power P max12 The computer 15 has stored in its memory value tables which allow the temperature T to be estimated based on previous estimates. i and state of charge SOC i To determine the permissible electrical power P max12 .

[0107] During a seventh step ED2 , the computer 15 reads from its memory the maximum electrical power P permitted by the charger 12 . max14 , the maximum electrical power is given by Figure 5 The straight line C2 in FIG. 1 represents a predetermined constant.

[0108] The computer also reads the selected time period δt i The electric power P available at the internal charging station 20 20 , the electric power is given by Figure 5 The straight line C3 in is represented.

[0109] The computer then calculates the power from these three max12 , P max14 , P 20 An electric power is selected from the above, the selected electric power being the lowest and thus constituting a factor limiting the power that can charge the traction battery 12 .

[0110] like Figure 5 As shown in , this limiting factor will differ depending on the state of charge SOC of the traction battery 12 (and on the temperature of the battery).

[0111] Then, the selected electric power P i With time period δt i In association, the power required by the charging station 20 for charging the traction battery 12 (and possibly also for powering the auxiliary devices 13 ).

[0112] Then, the computer 15 determines the battery 12 in the time period δt i The new state of charge SOC that will be presented at the end i+1 .

[0113] The state of charge SOC i+1 The value is obtained from the charging station 20 in the time period δt i The electric power P transmitted during i The charge state is also derived from the electrical power consumed by the auxiliary device 13 (for simplicity, this power will be considered as zero in the following).

[0114] More precisely, in the present case, during an eighth step EE1, the computer 15 determines the time interval δt i The electrical energy E previously stored in the traction battery 12 i Let's get started.

[0115] In this case, the electric energy E i The value of will be derived from the instantaneous state of charge SOC0 with the help of the following mathematical formula:

[0116] E i =SOC0.E max .SOH / 100

[0117] in:

[0118] -E max is a predetermined constant which is recorded in the memory of the computer 15 and corresponds to the maximum electrical energy that the traction battery 12 can store, and

[0119] The SOH is the state of health of the traction battery 12 , which is transmitted to the computer 15 by a third-party computer.

[0120] The computer 15 then determines the time period δt in the selected period by means of the following mathematical formula: i At the end, the electric energy E stored in the traction battery 12 i+1 :

[0121] E i+1 =E i +P i .Δt,

[0122] In this case, Δt is equal to 15 minutes.

[0123] During a ninth step EE2 , the computer 15 derives from the above electrical energy the energy consumed by the traction battery 12 during the selected time period δt i The new state of charge SOC that will be presented at the end i+1 :

[0124] SOC i+1 =100.E i+1 / (E max .SOH)

[0125] During a tenth step EF1 , the computer 15 converts the new state of charge SOC i+1 and target state of charge SOC N Make a comparison.

[0126] If the new state of charge SOC i+1 Higher than or equal to the target state of charge SOC N, the method then proceeds to an eleventh step EG1 during which the computer 15 sends to the charging station a signal received during the selected time period δt i Power reserved during the period P i Request.

[0127] Otherwise, that is, if only this time period δt i The target state of charge SOC will not be reached N , the method is repeated starting from the third step EB1 to check whether the traction battery 12 can be sufficiently charged by selecting not just a single time period but two time periods.

[0128] like FIG. 4A to FIG. 4D As shown in , this method can be repeated as many times as needed, wherein the target state of charge SOC is selected. N The required number of additional time periods.

[0129] Therefore, the manner in which the method is repeated can be described briefly.

[0130] When the third step EB1 is repeated for the first time, the computer 15 selects the available electric power P 20 Not zero, and the electricity cost C 20 The lowest most recent time period δt j Since the chart has been updated, the time period δt will not be reselected. i .

[0131] Then, during a fourth step EB2 , the computer 15 updates the diagram in order to avoid the subsequent reselection of this new time period δt j .

[0132] The next step would then be to estimate the traction battery 12 during these two selected time periods δt i ,δt j The battery status that should be displayed at the end.

[0133] To do this, the computer first considers the two selected time periods δt i ,δt j The time period closest to the current time.

[0134] For example, suppose it is the time period δt j (so that we can say j <i)。

[0135] Then, during a fifth step EC1 , the computer 15 uses the aforementioned mathematical model to estimate the current of the traction battery 12 during the time period δt j The temperature T j .

[0136] The computer 15 also estimates that the traction battery 12 isj The power state SOC that will be presented at the beginning i In this case, the state of charge SOC j Equal to the instantaneous state of charge SOC0.

[0137] During a sixth step ED1 , the computer 15 calculates, in the same manner as has been explained previously, the time period δt j The electric power P allowed by the traction battery 12 during max12 .

[0138] During a seventh step ED2, the computer 15 derives from the above-mentioned electrical power the value of the current in the time period δt j The electric power P that can be used to charge the traction battery 12 during j .

[0139] During the eighth step EE1 and the ninth step EE2, the computer 15 determines that the battery 12 is in the time period δt j The new state of charge SOC that will be presented at the end j+1 .

[0140] Then, this time, the computer calculates the i Repeat steps EC1 to EE2.

[0141] To this end, during a fifth step EC1 , the computer 15 uses the aforementioned mathematical model to estimate the current of the traction battery 12 during the time period δt i The temperature T i .

[0142] The computer 15 will then estimate the time period δt of the traction battery 12. i The power state SOC that will be presented at the beginning i In this case, the state of charge SOC i Equal to the state of charge SOC j+1 .

[0143] During a sixth step ED1 , the computer 15 calculates, in the same manner as has been explained previously, the time period δt i The electric power P allowed by the traction battery 12 during max12 .

[0144] During a seventh step ED2, the computer 15 derives from the above-mentioned electrical power the value of the current in the time period δt i The electric power P that can be used to charge the traction battery 12 during i .

[0145] During the eighth step EE1 and the ninth step EE2, the computer 15 determines that the battery 12 is in the time period δti The new state of charge SOC that will be presented at the end i+1 .

[0146] Finally, during a tenth step EF1 , the computer 15 converts the new state of charge SOC i+1 and target state of charge SOC N Make a comparison.

[0147] If the new state of charge SOC i+1 Higher than or equal to the target state of charge SOC N , the computer 15 sends a request to the charging station to reserve a time slot δt between the two selected time slots δt i ,δt j The selected electric power P i , P j .

[0148] Otherwise, the method is repeated again starting from the third step EB1, this time selecting three time periods (including these two time periods δt i ,δt j (included).

[0149] Fig. 6A The electricity cost C provided by the charging station 20 is shown. 20 Example of changes over time.

[0150] Figure 6B (Concomitantly) the predicted change in the state of charge SOC of the traction battery 12 until the departure time is shown.

[0151] Figure 6C (Incidentally) the change over time of the electric power P reserved for the charging station 20 in each time period is shown.

[0152] exist Figure 6B It can be observed that at the beginning of the method, the traction battery 12 is charged until a state of charge threshold is reached, above which there is no longer any risk of premature discharge of the traction battery 12 .

[0153] The battery is then charged during periods of low electricity rates. Finally, it can be observed that at departure time, the state of charge of the traction battery 12 has reached the target state of charge (60% in this case).

[0154] Thus, by means of the described method, the computer 15 is able to quickly send a request to the charging station 20 containing the reserved time periods and the electrical power required in each time period.

[0155] The method is based on a simplified estimation of the variation of the state of charge SOC of the traction battery 12 in order to reduce the computing power required to implement the method.

[0156] Therefore, this estimate may be slightly in error.

[0157] In order to avoid any charging problems, once charging has started, an operation of monitoring the changes in the state of charge SOC of the traction battery 12 is preferably implemented.

[0158] To this end, the computer records at each instant the instantaneous value of the state of charge SOC of the traction battery 12 and then compares this value with the expected value.

[0159] As long as the difference between these two values ​​remains below a predetermined threshold, no correction is performed.

[0160] However, if the difference exceeds a threshold, the computer will reinitialize the method described above, in particular by sending a request to the charging station to find out a new graph for the electricity rates and the power offered by the charging station.

[0161] However, during implementation of the method, a correction factor is applied in the present case to the permitted electrical power P of the traction battery 12. max12 Calculation.

[0162] Preferably, the value of the correction factor is adjusted according to the speed at which the instantaneous value of the state of charge deviates from the expected value of the state of charge.

[0163] Once the method is completed, the computer 15 sends a new request to the charging station 20 to reserve a new time slot: this is called "renegotiation".

Claims

1. A method for charging a battery (12) equipped with a motor vehicle (10), the motor vehicle being electrically connected to a charging station (20), the method The following steps are involved: a) receiving electric power (P) available at the charging station (20); 20 ) changes over time and the electricity cost (C 20 ) over time, and b) Select the available electrical power (P 20 ) is not zero and the time period with the lowest electricity fee (δt i ), Characterized in that the method further comprises the following steps: c) estimating the battery (12) during the time period (δt i ) will appear when the temperature (T i ) and the storage battery (12) in the time period (δt i ) will be presented at the beginning of the state of charge (SOC i ), d) based on the temperature (T i ) and the state of charge (SOC i ) to determine the charging station (20) in this time period (δt i ) during which the electric power (P i ), e) based on the electric power (P) determined in step d) i ) to deduce that in this time period (δt i ) ends, the new state of charge (SOC) of the battery (12) i+1 ), f) Compare the new state of charge (SOC i+1 ) and target state of charge (SOC N ), and then, if the new state of charge (SOC i+1 ) is higher than or equal to the target state of charge (SOC N ),but g) In this time period (δt i ) during which the charging station (20) is used to charge the battery with the electrical power (P i ) is used to charge the storage battery (12).

2. The method according to claim 1, in, If the new state of charge (SOC i+1 ) is lower than the target state of charge (SOC N ): - For an additional time period (δt j ), repeat steps b) to e), and - In step f), the target state of charge (SOC N ) and the battery (12) in these two time periods (δt i ,δt j ) and then compare the presented state of charge (SOC).

3. The method according to claim 2, in, In step a), a departure time at which the motor vehicle (10) is scheduled to be disconnected from the charging station (20) is obtained, and in step b), the selected time period is before the departure time.

4. The method according to claim 3, in, During the repetition of steps b) to e), it is determined that the charging station (20) is within these time periods (δt i ,δt j ) during each time period in the vehicle, and then derive therefrom the change in the state of charge (SOC) of the battery (12) until the departure time.

5. The method according to any one of claims 1 to 4, in, In step b), if the electricity rate is the lowest in several time periods, the time period (δt i ) is the earliest time period.

6. The method according to any one of claims 1 to 4, in, Before step a), perform the following operations: - Determine the instantaneous state of charge (SOC) of the battery (12) 0 ), -The instantaneous state of charge (SOC 0 ) and the state of charge threshold (SOC min ) is compared, and if the instantaneous state of charge (SOC 0 ) is lower than the state of charge threshold (SOC min ),but - At this available electrical power (P 20 ) is not zero during the first time period for charging the storage battery (12).

7. The method according to any one of claims 1 to 4, in, In step c), the temperature (T i ).

8. The method according to any one of claims 1 to 4, in, In step d), in order to determine the electrical power (P i ), select the lowest electrical power from the following: - In the selected time period (δt i ) the available electrical power (P 20 ),as well as - a maximum electrical power allowed for the motor vehicle (10), the maximum allowed electrical power being based on the temperature (T i ) and the state of charge (SOC i ) to determine.

9. The method according to any one of claims 1 to 4, in, In step e), calculate the time period (δt i ) at the end of the process, the energy (E) already stored in the storage battery (12) i+1 ), and then derive the new state of charge (SOC i+1 ).

10. A motor vehicle (10) comprising at least one electric drive motor (11) and a battery (12) designed to supply electric current to each electric motor (11), It is characterized in that The motor vehicle comprises a computer (15) which is programmed to implement a method according to one of the preceding claims.

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