Charging a motor vehicle's energy storage system

Abstract

A method (300) for charging an energy storage device (110) of a motor vehicle comprises steps of detecting (210) a planned end of charging; detecting (205) a state of charge of the energy storage device (110); determining (215) a charging current such that the state of charge of the energy storage device (110) reaches a predetermined state of charge as close as possible to the planned end of charging; and charging (220) the energy storage device (110) with the determined charging current.

Description

[0001] The present invention relates to the charging of an energy storage device of a motor vehicle. In particular, the invention relates to the charging of the energy storage device as a function of a specified time.

[0002] A motor vehicle includes an electrical energy storage device that can provide energy, for example, for an electric drive motor of the motor vehicle. To charge the energy storage device, the motor vehicle can be connected to an external charging device and charged with a predetermined current. Such a charging device can be private or public, for example.

[0003] Typically, attempts are made to supply the electrical energy storage device with a maximum charging current or maximum electrical power in order to charge it as quickly as possible. The energy storage device or a charger can be subjected to considerable strain during this process. If the energy storage device is electrochemical, it can age or wear out more quickly if the charging current is high. A power supply network for the charging device can be subject to short and high loads, which can result in a load peak. To avoid keeping the vehicle unnecessarily connected to the charging device, it must be removed from it in good time after the charging process is completed. A person traveling in a vehicle may find it difficult to use a charging break for another useful activity if the charging process is carried out too quickly.

[0004] Some vehicles allow the charging current to be manually reduced or limited. This allows for more efficient use of the available charging time. However, it can be time-consuming for the vehicle user to correctly calculate an appropriate charging current for an upcoming charging time. Nonlinear relationships can occur during the calculation, which can complicate both calculation and estimation.

[0005] One object underlying the present invention is to provide an improved technology for charging an energy storage device of a motor vehicle within a predetermined charging time. The invention achieves this object by means of the subject matter of the independent claims. Subclaims specify preferred embodiments.

[0006] According to a first aspect of the present invention, a method for charging an energy storage device of a motor vehicle comprises steps of detecting a planned end of charging; detecting a state of charge of the energy storage device; determining a charging current such that the state of charge of the energy storage device reaches a predetermined state of charge as close as possible to the planned end of charging; and charging the energy storage device with the determined charging current.

[0007] The method can be initiated when the motor vehicle is connected to a charging device and a charging process is about to begin. A person responsible for the motor vehicle can then move away from the vehicle until the expected end of charging. At the end of charging, the energy storage device may have reached the predetermined charge level, and the person can disconnect the motor vehicle from the charging device and drive away, for example. The charging device can be immediately available to supply another motor vehicle.

[0008] Using the described method, the energy storage device can be charged precisely so that the charging time available between the start and end of charging is optimally utilized. During the charging time, the energy storage device can be charged relatively slowly, which can protect the energy storage device itself or a charging device. Heating caused by the charging process can be reduced. The efficiency of the charging process can be improved. It is preferred that a positive charging current flows throughout the entire process. A charging device connected to the motor vehicle can be used continuously over the entire charging time. The load on the energy storage device or a charging device caused by charging can be distributed more effectively over time.

[0009] The determined charging current is preferably, at least temporarily, lower than the maximum possible charging current. In other words, the charging current to the energy storage device can be artificially reduced to better utilize the available charging time. By automatically determining the charging current based on the planned end of charging, the charging process can be carried out more automatically.

[0010] In one embodiment, a constant charging current is controlled over the charging duration. The energy storage device can be charged essentially linearly over time, and the load on the energy storage device or a charging device can be distributed more effectively over time. The energy input per unit of time can be essentially constant.

[0011] In another embodiment, different charging currents are controlled successively over the charging duration. This approach is particularly advantageous if the charging current can only be controlled in discrete steps. The predetermined state of charge can be achieved more accurately by the planned end of charging. An attempt can be made to make as few changes to the charging current as possible. In various embodiments, a higher charging current can be used first, followed by a lower one, or vice versa.

[0012] The energy storage device can be charged from a charging network. Energy can be drawn from the charging network at at least two different power levels. The charging current can be determined based on the power levels. The charging current can be controlled using the different charging power levels even if a controllable reduction in the charging current is not provided. Charging can be performed at full power in each case, whereby the predetermined state of charge at the expected end of charging can be achieved by selecting a power level.

[0013] In this case, a power can be assigned to a provided current type. A first current type can comprise a single-phase alternating current. The assigned power can be low, and the charging current can also be low. A second current type can comprise a three-phase alternating current, which can be provided with a medium power or a medium charging current. Furthermore, charging can be possible using direct current, whereby a high power or a high charging current can be realized.

[0014] In a further embodiment, a change in the planned end of charging is detected during charging. The charging current can be re-determined and controlled with respect to the changed end of charging. The change in the end of charging can be transmitted, in particular by means of wireless technology, from a person responsible for the motor vehicle to a control device for controlling the charging process. In this way, the end of charging can be postponed, in particular, if the person's expected arrival time at the motor vehicle changes. If a longer charging time is available, the charging current can be reduced accordingly. If, on the other hand, the charging time is shorter than initially assumed, the charging current can be increased. In both cases, the predetermined state of charge can be achieved more effectively at the new end of charging.

[0015] In a corresponding manner, a change in the predetermined state of charge can also be detected during charging, and the charging current can be redetermined and controlled with respect to the changed state of charge.

[0016] It is generally preferred that the predetermined state of charge includes the complete discharge of the energy storage device. This maximizes the range of the motor vehicle at the end of charging. In particular, if the motor vehicle is being charged at a public facility while a person assigned to the vehicle is engaged in another activity, the motor vehicle can be at its maximum operational capacity upon the person's return.

[0017] In a further embodiment, the predetermined charge level can be selectable. For example, the person assigned to the motor vehicle can select the desired target charge level themselves, for example, depending on the energy price for the charging current.

[0018] According to a further aspect of the present invention, a control device for charging an energy storage device of a motor vehicle comprises an input device for detecting a planned end of charging; a detection device for detecting a state of charge of the energy storage device; a control device for charging the energy storage device with a predetermined charging current; and a processing device. The processing device is configured to determine a charging current such that the state of charge of the energy storage device reaches a predetermined state of charge as close as possible to the planned end of charging; and to control the determined charging current.

[0019] The processing device is preferably configured to partially or completely execute a method described herein. For this purpose, the processing device can be implemented electronically and, for example, comprise an integrated circuit, a programmable logic module, or a programmable microcomputer. The method can be implemented in the form of a configuration or as a computer program product with program code means for the processing device. The configuration or the computer program product can be stored on a computer-readable data carrier. Features or advantages of the method can be transferred to the device, or vice versa.

[0020] In a first embodiment, the control device is configured for use on board a motor vehicle. A motor vehicle may comprise the described control device. The motor vehicle preferably comprises an electric drive motor configured to be operated with energy from the electrical energy storage device in order to drive the motor vehicle. The motor vehicle may, in particular, comprise a motorcycle, a passenger car, a truck, or a bus.

[0021] In another embodiment, the control device is designed to be used outside a motor vehicle. A charging device for use with an electric charging network comprises the control device described herein. The charging device is preferably stationary and can be designed, for example, as a charging station or a wallbox.

[0022] According to yet another embodiment, the control device is designed as a standalone device that can be inserted between a charging device and a motor vehicle. For this purpose, the control device can be inserted, in particular, into a charging line between the charging device and the motor vehicle.

[0023] The invention will now be described in more detail with reference to the accompanying drawings, in which: Fig. 1 a system; Fig. 2 a flow diagram of a method; and Fig. 3 exemplary curves on an energy storage device of a motor vehicle illustrated.

[0024] Fig. 1 shows a system 100 with a motor vehicle 105. The motor vehicle 105 includes an electrical energy storage device 110, which is preferably configured to provide electrical energy for operating an electric drive motor. The electrical energy storage device 110 can be charged at a charging device 115, which is typically connected to a charging network 120. The charging network 120 can provide electrical energy in one or more current types. Different charging voltages can be implemented.

[0025] A control device 125 is mounted between the charging device 115 and the energy storage device 110 of the motor vehicle 105, which, in the present case, is mounted on board the motor vehicle 105. It should be noted that in other embodiments, the control device 125 can also be designed, for example, as a standalone device or as part of the charging device 115. The control device 125 preferably comprises an input device 130 and a charging controller 135. Optionally, a wireless interface 140 can also be provided.

[0026] The charging controller 135 is configured to control a charging current from the charging device 115 into the energy storage device 110. The charging current can be limited by the charging device 115. Different charging currents can apply for different current types or charging powers. The charging controller 135 is preferably configured to reduce the charging current below this limit. A continuous or discrete reduction in the charging current can be controlled. Furthermore, the charging controller 135 can be configured to determine a state of charge of the energy storage device 110. The state of charge can indicate how much energy is stored in the energy storage device 110. This information can be related to a maximum capacity of the energy storage device 110 and can be expressed, for example, as a percentage.

[0027] The input device 130 is preferably configured to be operated by a person 145 associated with the motor vehicle 105, for example, a driver of the motor vehicle 105. A mobile device 150, which may be associated with the person 145, may also be used to input or output information. The mobile device 150 may communicate with the control device 125 via the wireless interface 140.

[0028] It is proposed that the control device 125 controls a charging process of the electrical energy storage device 110 at the charging device 115 such that the energy storage device 110 reaches a predetermined state of charge as precisely as possible when a planned end of charging is reached. The end of charging can be indicated, for example, by the person 145 using the input device 130 or the mobile device 150. The mobile device 150 preferably comprises a smartphone; in other embodiments, another device that can communicate wirelessly with the interface 140 of the control device 125 can also be used.

[0029] Fig. 2 shows a flowchart of a method 200 for controlling a charging process of the energy storage device 110 of the motor vehicle 105. In a step 205, a current state of charge of the energy storage device 110 can be determined. The state of charge can be provided by the charging controller 135. To determine the state of charge, for example, an open-circuit voltage of the energy storage device 110 can be determined. Alternatively, a balance of energy withdrawn and absorbed in the energy storage device 110 can be maintained.

[0030] In a step 210, a planned end of charging can be determined. A charging time can elapse between the start of charging and the end of charging. In an alternative embodiment, the charging time can therefore be determined instead of the end of charging. A typical charging time is specified in hours and / or minutes, with approximately two to four hours being considered a typical charging time, for example.

[0031] Furthermore, in step 210, a desired charge level of the energy storage device 110 at the end of charging can be determined. The desired charge level can, for example, correspond to approximately 80% or approximately 50% of the maximum possible capacity of the energy storage device 110. If the charge level cannot be selected, a predetermined charge level can be assumed. The predetermined charge level can, in particular, be 100%.

[0032] In a step 215, a charging current into the energy storage device 110 can be determined based on the current state of charge, the desired state of charge, and the available charging time. The charging current is preferably determined such that the energy storage device 110 is continuously charged over the entire charging time, with the desired state of charge occurring as precisely as possible only when the end of charging is reached.

[0033] In a step 220, the charging current can be controlled. In particular, depending on the controllability of the charging controller 135, the charging current can be maintained at a predetermined value throughout the entire charging period, so that the energy storage device 110 is charged linearly. Alternatively, if only predetermined, discrete charging currents can be achieved by the charging controller 135, a sectionally constant charging current can be controlled.

[0034] Step 210 and following steps can also be executed multiple times, for example if during charging in step 220 a message arrives about a changed specification regarding the preferred charging state or the expected end of charging.

[0035] Fig.3 shows exemplary curves on an energy storage device 110 of a motor vehicle 105. A first representation 305 and a second representation 310 each show a time in the horizontal direction and a filling level of the energy storage device 110 in the vertical direction. Time and energy scales are transferable between the representations 305, 310.

[0036] Referring to the first illustration 305, it is assumed that the energy storage device 110 assumes a state of charge between 0% and 100% at a time t0. An exemplary state of charge is shown. A planned end of charging occurs at a time t4.

[0037] If the energy storage device 110 is charged with a maximum charging current, a first charging curve 315 results. The energy storage device 110 may already be 100% charged at a time t2. Therefore, no further charging of the energy storage device 110 can occur between times t2 and t4.

[0038] If only a low charging current is controlled, a second charging curve 320 may result. In this case, the energy storage device 110 may not yet be fully charged at time t4. The energy storage device 110 may only reach a 100% charge level at a later time.

[0039] A third charging curve 325 can be considered ideal. Here, a charging current is used that is just large enough to flow constantly throughout the entire charging period, and the energy storage device 110 is charged to 100% at the expected end of charging t4.

[0040] The charging current cannot always be controlled to a value that enables charging in the manner of the third charging curve 325. For example, only different, predetermined charging currents may be controllable. The second representation 310 shows various possibilities for continuously charging the energy storage device 110 to the predetermined state of charge. A fourth charging curve 330 comprises a first section between times t0 and t1 and a second section between times t1 and t4. In the first section, a charging current is assumed as used in the first charging curve 315. Viewed graphically, the gradients of the first section and the first charging curve 315 are the same. Between times t1 and t4, charging continues with a lower charging current, which corresponds to the charging current of the second charging curve 320.The time t1 is chosen so that the energy storage device 110 is fully charged as precisely as possible at the end of charging t4.

[0041] Time t1 can be determined graphically, for example, by plotting the second section of the fourth charging curve 330 backward in time from the desired target point (100% at t4) with a gradient determined by the lower current. Similarly, the second section can be plotted to the right from the starting point (existing state of charge at t0), with its gradient determined by the larger of the two currents. Time t1 is determined where the two lines intersect.

[0042] The two sections can also be reversed in their order, resulting in a fifth charging curve 335. Initially, charging occurs with a lower current from time t0 to t3, and then with a higher current until time t4.

[0043] Of course, additional charging curves can also be created from parts of the charging curves 330 and 335 by joining corresponding segments. Any number of changes to the current used can be made. Reference symbol 100 systems 105 Motor vehicle 110 electrical energy storage 115 Charging device 120 charging network 125 Control device 130 Input device 135 Charging control 140 wireless interface 145 people 150 mobile devices 200 procedures 205 Determine charge level 210 Determine planned end of charging 215 Determine charging current 220 control charging current 305 first representation 310 second representation 315 first charging curve 320 second charging curve 325 third charging curve 330 fourth charging curve 335 fifth charging curve

Claims

[1] Method (300) for charging an energy storage device (110) of a motor vehicle (105), the method (300) comprising the following steps: - detecting (210) a planned end of loading; - detecting (205) a state of charge of the energy storage device (110); - determining (215) a charging current such that the charging state of the energy storage device (110) reaches a predetermined charging state as far as possible at the planned end of charging; and - Charging (220) the energy storage device (110) with the determined charging current. [2] The method (300) of claim 1, wherein a positive charging current flows throughout the process. [3] Method (300) according to claim 1 or 2, wherein the determined charging current is at least temporarily lower than a maximum possible charging current. [4] Method (300) according to one of the preceding claims, wherein a constant charging current is controlled over the charging period. [5] Method (300) according to one of claims 1 to 3, wherein different charging currents are controlled (220) one after the other over the charging period. [6] Method (300) according to one of the preceding claims, wherein the energy storage device (110) is charged from a charging network (120); wherein energy can be drawn from the charging network (120) with at least two different power levels; and the charging current is determined (215) as a function of the power levels. [7] The method (300) of claim 6, wherein a power is associated with a provided current type. [8] Method (300) according to one of the preceding claims, wherein a change in the planned charging end is detected (210) during charging; and the charging current is redetermined and controlled with respect to the changed charging end. [9] Method (300) according to one of the preceding claims, wherein the predetermined state of charge comprises the full charge of the energy storage device (110). [10] Control device (125) for charging an energy storage device (110) of a motor vehicle (105), the control device (125) comprising: - an input device (130, 150) for detecting a planned end of loading; - a detection device (135) for detecting a state of charge of the energy storage device (110); - a charging controller (135) for charging the energy storage device (110) with a predetermined charging current; and - a processing device configured to determine a charging current such that the charging state of the energy storage device (110) reaches a predetermined charging state as close as possible to the planned end of charging; and to control the determined charging current. [11] Motor vehicle (105) comprising a control device (125) according to claim 10. [12] Charging device (115) for connection to an electrical charging network (120), wherein the charging device (115) comprises a control device (125) according to claim 10.

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