Method for preheating a battery of an electrically operated motor vehicle, and charging device

Abstract

A method for preheating a battery of an electrically driven motor vehicle, in particular an electric vehicle or a hybrid vehicle, controls a charging process and a discharging process of the battery in such a way that a minimum temperature of the battery is attained at a departure time of the motor vehicle.

Claims

1. A method for preheating a battery of an electrically driven motor vehicle, the method comprising: controlling both a charging process and a discharging process of the battery such that a minimum temperature of the battery is reached at a departure time of the motor vehicle without applying heat from an external source, wherein during the charging process and during the discharging process of the battery, a temporal profile of a charging current and of a discharging current of the battery is controlled in order to heat the battery to the minimum temperature at the departure time by the charging current and by the discharging current, and wherein the temporal profile of the charging current and of the discharging current of the battery is controlled such that the battery is first fully charged in a first charging process and then alternately discharged and charged.

2. The method according to claim 1, wherein the departure time of the motor vehicle is set by a user, and the battery is preheated depending on the departure time.

3. The method according to claim 1, wherein the battery is preheated such that the minimum temperature of the battery is maintained continuously.

4. The method according to claim 1, wherein electrical energy is fed to an electricity grid during the discharging process from the battery, which battery is connected to the electricity grid by a charging device of the motor vehicle.

5. The method according to claim 1, wherein a temperature of the battery is measured, and the charging process and/or the discharging process is controlled or regulated depending on the measured temperature.

6. The method according to claim 1, wherein the vehicle is an electric vehicle or a hybrid vehicle.

7. A charging apparatus of an electrically driven motor vehicle, the charging apparatus comprising: a first interface to a temperature sensor for measuring a temperature of a battery of the vehicle, a second interface for receiving a set departure time, and a control unit for setting a charging process and a discharging process of the battery based on the detected temperature and the set departure time, wherein: the control unit controls both the charging process and the discharging process of the battery such that a minimum temperature of the battery is reached at the set departure time of the motor vehicle without applying heat from an external source, and during the charging process and during the discharging process of the battery, the control unit controls a temporal profile of a charging current and of a discharging current of the battery in order to heat the battery to the minimum temperature at the departure time by the charging current and by the discharging current, wherein the temporal profile of the charging current and of the discharging current of the battery is controlled such that the battery is first fully charged in a first charging process and then alternately discharged and charged.

8. The charging apparatus according to claim 7, further comprising: a third interface to a control device of the motor vehicle for operating an air-conditioning system during the discharging process.

9. The charging apparatus according to claim 7, further comprising: a fourth interface to a controller of an electricity grid.

10. The charging apparatus according to claim 7, wherein the vehicle is an electric vehicle or a hybrid vehicle.

11. A motor vehicle comprising a charging apparatus according to claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic side view of a motor vehicle having a battery and a charging apparatus.

(2) FIGS. 2 to 4 are temporal profiles of the temperature of a battery, wherein a minimum temperature of the battery is reached at a departure time.

(3) Parts that correspond to one another are provided with the same reference signs in all of the figures.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) FIG. 1 schematically illustrates an electrically driven motor vehicle 2 having a battery 4. The electrically driven motor vehicle 2 may be an electric vehicle or a hybrid vehicle having an electric drive. Furthermore, the motor vehicle 2 has a charging apparatus 6 having a connection 8, by which the charging apparatus 6 can be connected to an electricity grid 10. In addition, the charging apparatus 6 has a first interface 12 to a temperature sensor 14. A temperature T of the battery 4 is measured by way of the temperature sensor 14. A set departure time t.sub.A is received by a second interface 16 of the charging apparatus 6.

(5) In the exemplary embodiment of FIG. 1, the second interface 16 is embodied as a radio interface to a wireless network. By way of said interface, for example, the departure time t.sub.A can be set for a user conveniently by use of a smart phone.

(6) A control unit 18 of the charging apparatus 6 receives both the temperature T of the battery 4 measured by means of the temperature sensor 14 and the departure time t.sub.A set by the user. Alternatively, the departure time t.sub.A is also able to be ascertained from a user behavior stored in the control unit 18.

(7) A temporal profile of a charging process and of a discharging process of the battery 4 is set by the control unit 18 of the charging apparatus 6 depending on the set departure time t.sub.A and based on the measured temperature T. In this case, the charging process and the discharging process are controlled in such a way that the battery 4 is preheated at the departure time t.sub.A and a minimum temperature T.sub.min of the battery 4 is reached at the departure time t.sub.A. As a result, a reduction in the power and the capacity of the battery 4 is prevented even in the case of relatively low ambient temperatures.

(8) To preheat the battery 4 of the motor vehicle 2, the battery is heated owing to operation by way of a charging current and by way of a discharging current based on ohmic losses that arise and based on thermodynamic effects, in particular based on a change in the entropy of the battery 4 in the case of a thermochemical reaction during the charging and during the discharging process. In a suitable manner, the temporal profile of the charging current and of the discharging current during the charging process and during the discharging process is controlled in such a way that the minimum temperature T.sub.min of the battery 2 is reached at the departure time t.sub.A.

(9) The charging apparatus 6 furthermore has a third interface 20 to a control device 22 of the motor vehicle 2. As a result, the discharging process is able to be used more advantageously in order to operate a consumer of the motor vehicle 2, wherein the discharging process is controlled in such a way that the battery 4 is suitably preheated.

(10) In the exemplary embodiment of FIG. 1, the consumer is embodied as an air-conditioning system 24. This can be used to air-treat an interior of the motor vehicle 2 in such a way that a temperature perceived to be comfortable by the user is set there at the departure time t.sub.A. Alternatively or additionally, the consumer can increase the safety of the motor vehicle 2, for example by virtue of iced windscreens being de-iced by way of a heating apparatus. The battery 2 is preheated depending on the departure time t.sub.A during operation of the consumer.

(11) A fourth interface 26 of the charging apparatus 6 is embodied as a radio interface. The fourth interface 26 serves to couple the charging apparatus 6 of the motor vehicle 2 to a controller 28 of the electricity grid 10.

(12) The battery 4 of the motor vehicle 2 is connected to the electricity grid 10 by means of the charging apparatus 6. In this case, the coupling of the charging apparatus 6 to the electricity grid 10 makes it possible for the control of the charging process and of the discharging process to function in a cost-optimized manner and for the battery 4 to be preheated at the departure time t.sub.A. For example, a low-priced off-peak electricity tariff can preferably be used to charge the battery. During the discharging process, the battery 4 feeds electrical energy to the electricity grid 10, as an alternative to operating a consumer in the motor vehicle 2. The temporal profile of the discharging process is controlled here in such a way that the battery 4 is suitably heated depending on the departure time t.sub.A, and that the battery 4 feeds energy to the electricity grid 10 according to a consumer profile of said electricity grid. The battery 4 can thus be used as an additional energy store for the electricity grid 10.

(13) FIGS. 2 to 4 outline temporal profiles of the temperature T of the battery 4. The charging process and the discharging process of the battery 4 are controlled here in such a way that the battery 4 reaches the minimum temperature at the departure time t.sub.A.

(14) In addition, the temperature T of the battery 4 is measured by means of the temperature sensor 14. The charging process and the discharging process are controlled or regulated according to the measured temperature T and the departure time t.sub.A. In this case, the measured temperature T is compared with the minimum temperature T.sub.min. If the measured temperature T is lower than the minimum temperature T.sub.min, the battery 4 is discharged and charged so that the battery 4 reaches the minimum temperature T.sub.min at the departure time t.sub.A. This regulation of the temperature T by the minimum temperature T.sub.min is outlined in FIGS. 2 and 3 as undulated profiles of the temperature T.

(15) FIGS. 2 to 4 furthermore show a temperature T of the battery 4 that increases over time t after the departure time t.sub.A. The reason for this is that, owing to operation, a power demand on the battery 4 during driving operation is increased, with the result that the temperature T of the battery 4 increases.

(16) In a first mode of operation, the departure time t.sub.A is set by the user or the departure time t.sub.A is ascertained from the user behavior. Based on this, the charging process and the discharging process are regulated or controlled in such a way that the battery 4 is used in a manner that protects the battery as much as possible and/or that saves costs as much as possible, for example as an energy store of the electricity grid 10. In this case, the temperature T of the battery 4 is intended to reach the minimum temperature T.sub.min substantially only at the departure time t.sub.A.

(17) In a second mode of operation, the battery 4 is preheated in such a way that the minimum temperature T.sub.min is reached and then maintained continuously. As a result, the battery 4 is advantageously preheated practically at any time t even in the case of an undefined departure time t.sub.A.

(18) To this end, FIG. 3 shows by way of example a temporal profile of the temperature T of the battery 4, in which the temperature T reaches the minimum temperature T.sub.min relatively quickly. The temperature T of the battery 4 is subsequently maintained at the minimum temperature T.sub.min by suitable control or regulation of the charging process and of the discharging process.

(19) FIG. 4 outlines a temporal profile of the temperature T of the battery 4, in which the temperature T is initially greater than the minimum temperature T.sub.min. For example, in this case, the motor vehicle 2 was parked a relatively short time ago. The temperature T of the battery 4 matches the ambient temperature and is reduced based on this.

(20) In the second mode of operation, cooling of the battery 4 below the minimum temperature T.sub.min by corresponding control or regulation of the charging process and of the discharging process is prevented, which is illustrated in FIG. 4 as a punctiform regulation profile of the temperature 4.

(21) In the first mode of operation, cooling of the battery 4 below the minimum temperature T.sub.min is effected here first. The control or regulation of the charging process and/or of the discharging process takes place depending on the departure time t.sub.A so that the minimum temperature T.sub.min has to be achieved only at the departure time t.sub.A.

(22) The charging process and the discharging process are controlled in both modes of operation in such a way that the minimum temperature T.sub.min is reached at the departure time t.sub.A and that a maximum temperature T.sub.max of the battery 4 is not exceeded by the charging process and the discharging process. The battery 4 is used here, for example, in the manner of a buffer or energy store of the electricity grid 10 and/or feeds energy to consumers, such as the air-conditioning system 24 of the motor vehicle 2, for example.

(23) The invention is not restricted to the exemplary embodiments described above. Rather, other variants of the invention may also be derived therefrom by a person skilled in the art without departing from the subject matter of the invention. In particular, it is furthermore the case that all individual features described in conjunction with the exemplary embodiments may also be combined with one another in some other way without departing from the subject matter of the invention.

LIST OF REFERENCE SIGNS

(24) 2 Motor vehicle 4 Battery 6 Charging apparatus 8 Connection 10 Electricity grid 12 First interface 14 Temperature sensor 16 Second interface 18 Control unit of the charging apparatus 20 Third interface 22 Control device of the motor vehicle 24 Air-conditioning system 26 Fourth interface 28 Controller of the electricity grid t.sub.A Departure time T Temperature T.sub.min Minimum temperature

(25) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.