WO2011069729A1

WO2011069729A1 - Battery heater for motor vehicles with an electric drive motor

Info

Publication number: WO2011069729A1
Application number: PCT/EP2010/065627
Authority: WO
Inventors: Andreas Bosch; Alexander Reitzle; Holger Fink; Achim Schmidt
Original assignee: Sb Limotive Company Ltd.; Sb Limotive Germany Gmbh
Priority date: 2009-12-10
Filing date: 2010-10-18
Publication date: 2011-06-16
Also published as: DE102009054461A1

Abstract

A battery heater for heating a traction battery of a motor vehicle with an electric drive motor for driving the motor vehicle. The battery heater has a first connection for the traction battery and a second connection for the electric drive motor. The first connection and the second connection each have a first terminal and a second terminal. The battery heater is designed to electrically connect, in a first time period of a switching cycle, the first terminal of the first connection to the first terminal of the second connection and the second terminal of the first connection to the second terminal of the second connection and thus to allow a current with a first mathematical sign to flow. In addition, the battery heater is designed to electrically connect, in a second time period of the switching cycle which follows on from the first time period, the second terminal of the first connection to the first terminal of the second connection and the first terminal of the first connection to the second terminal of the second connection and thus to allow a resonant current with a second mathematical sign which is in opposition to the first mathematical sign to flow.

Description

description

title

Battery heater for motor vehicles with electric drive motor prior art

It is becoming apparent that in the future, more and more rechargeable battery systems will be used both in stationary applications (e.g., in wind turbines or emergency power systems) and in vehicles (e.g., in hybrid and electric vehicles). In order to actually provide the required power and energy data, the battery cells should be operated in a temperature window usually between about 0 ° C and 40 ° C. If the temperatures are too high, the cells should be cooled, and at low temperatures they should be heated accordingly. The setting of the temperature of the battery cells takes place here in the context of thermal management, which is connected to the air conditioning circuit of the vehicle or operated via a separate coolant circuit. Both the rapid cooling, for example, when the vehicle has been in the sun for a long time in the summer, as well as the rapid heating in winter present at the present time challenges, since this energy must be used from the battery itself, which is no longer to drive of the vehicle is available. Therefore, the highest possible efficiency for heating and cooling is desirable.

The invention is dedicated to the aspect of fast and energy-optimized heating of the battery cells.

In the prior art, it is known to supply a current-carrying resistor for generating heat from the drive battery itself, the resistor (eg an incandescent filament) placed in local proximity to the battery cells or the heat generated in the resistor via a suitable medium the battery cells is supplied (resistance heating). However, the efficiency for this process is not very high, so that the drive battery is taken more energy (and is no longer available for the drive), as would actually be necessary.

Another way to heat the battery cells is to use an inductor, which is used for resonance. Energy is taken from the drive battery via a current which, apart from losses due to the non-ideal components, can be stored in the magnetic field of the inductance and fed back into the drive battery from there. The drive battery heats up by the alternate charging and discharging, the efficiency compared to the resistance heating is significantly better, since the heat loss in the battery cells themselves is obtained and the efficiency only by ohmic losses in the inductance and due to electrochemical conversion losses under the Ideal sinks.

DISCLOSURE OF THE INVENTION The object of the invention is to introduce a particularly efficient possibility of heating the battery cells of a drive battery in a short time.

A first aspect of the invention therefore introduces a battery heater for heating a drive battery of a motor vehicle with an electric drive motor for driving the motor vehicle, which has a first connection for the drive battery and a second connection for the electric drive motor, wherein the first connection and the second connection each having a first pole and a second pole. According to the invention, the battery heater is designed to electrically connect the first pole of the first terminal to the first pole of the second terminal and the second pole of the first terminal to the second pole of the second terminal in a first time period of a switching cycle, thus flowing a current of a first sign allow. In a second period of the switching cycle following the first time period, the battery heater connects the second terminal of the first terminal to the first terminal of the second terminal and the first terminal of the second terminal first terminal electrically connected to the second pole of the second terminal and thus allows a resonant current of a second sign opposite to the first sign to flow. The sign of the current is to be understood in each case based on the drive battery.

The invention makes use of the fact that the electric drive motor itself represents an inductance, which can be used for an inductive battery heating due to the motor windings contained in it. The battery itself also acts as a capacitor, which is coupled to the inductance to a resonant circuit. Since the current flowing for the heating current can be chosen so small that the mechanical inertia of the engine is not overcome, the battery heater can be operated even when the vehicle is stationary. The invention makes use of the property of an inductance to maintain a current flowing in it as much as possible. If the current in an inductance is reduced, the inductance feeds the degree of reduction of the inductance

Current corresponding differential current from its magnetic field. Thus, it becomes possible to supply an excitation current into the motor inductance from the drive battery to build up a magnetic field and then inversely connect the motor inductance to the drive battery, whereby the motor inductance returns a corresponding resonance current to the drive battery

Magnetic field of the motor inductance is reduced.

The battery heater is also preferably configured to electrically connect the second pole of the first terminal to the first pole of the second terminal and the first pole of the first terminal to the second pole of the second terminal in a third time period of the switching cycle following the second time period, and so on Flowing current of the first sign, and electrically connecting the first pole of the first terminal to the first pole of the second terminal and the second pole of the first terminal to the second pole of the second terminal in a fourth time period of the switching cycle following the third time period and thus to let a resonance current of the second sign flow. Once the magnetic field of the motor inductance is reduced as described above, again a current from the drive battery begins to flow into the (inversely connected) motor inductance and again build up a magnetic field of opposite sign (third

Time period). Once the magnetic field has been established, the motor inductance can be restored to the original, non-inverted manner are connected to the drive battery, which in turn fed a resonance current from the magnetic field of the motor inductance and is fed back into the drive battery. By appropriate choice of the time periods of the Schaltzyklusses, it is possible to perform two discharges and recharges with only two switching operations.

The battery heater is preferably formed periodically alternating the first pole of the first terminal with the first pole of the second terminal and the second pole of the first terminal with the second pole of the second terminal and the second pole of the first terminal with the first pole of the second terminal and electrically connecting the first pole of the first terminal to the second pole of the second terminal. These switching operations can be carried out until the temperature of the battery cells has risen to the desired value.

Particularly preferred is an embodiment suitable for a drive battery with an electrolyte, in which a reciprocal of a Debye-Falkenhagen limit frequency of the electrolyte is longer than the switching cycle. The Debye-Falkenhagen effect is an electrochemical effect that solves the behavior

Describes ions in a solvent when applying a high-frequency alternating field. Due to the applied high-frequency alternating field, the ions are vibrated along the electric field lines according to the excitation frequency. From a certain, depending on the respective electrolyte limit frequency, the Debye-Falkenhagen cutoff frequency, there is a significant increase in the conductivity, because the movement of the individual ions in the high-frequency alternating field is so fast that the otherwise surrounded by a respective ion Cloud of counterions caused relaxation effect no longer occurs. Below the cut-off frequency, the counter-charge of the counterions slows down the movement of an ion. A side effect of the Debye

Falkenhagen effect is a heating of the electrolyte as a function of the radiated energy, since heat at the quantum mechanical level is nothing other than the oscillation of particles or ions. Therefore, if the switching cycle is chosen to be shorter than the reciprocal of the Debye-Falkenhagen cutoff frequency for a given electrolyte (ie, if the frequency of the switching operations is above the Debye-Falkenhagen cutoff frequency), a particularly fast recovery can be achieved. heating of the electrolyte can be effected. This means at the same time that correspondingly fewer switching cycles are needed to bring the electrolyte and thus the battery cells to the desired temperature. However, it also follows that the losses due to line resistance outside the drive battery are minimized, which improves the efficiency of the battery heater accordingly. In addition, the movement of the ions above the Debene-Falkenhagen cut-off frequency is so fast that no or at least no appreciable electrochemical transformations take place on the battery electrodes, which would correspond to a series resistance in an electrical equivalent circuit of the arrangement and an undesirable degradation of efficiency and an additional Would mean load on the battery.

The battery heater may include a first switch having a first electrode connected to the first pole of the first terminal and a second electrode connected to the first pole of the second terminal, a second switch having a first electrode connected to the second pole of the first terminal, and a second electrode connected to the second pole of the second terminal, a third switch having a first electrode connected to the first pole of the first terminal and a second electrode connected to the second pole of the second terminal, and a fourth switch having a second electrode having a first electrode connected to the second pole of the first terminal and having a second electrode connected to the first pole of the second terminal. The first to fourth switches also each have a control electrode connected to a controller.

Preferably, the control electrode of the first switch with the control electrode of the second switch and the control electrode of the third switch are connected to the control electrode of the fourth switch.

A second aspect of the invention introduces a drive battery with a battery heater according to the first aspect of the invention. If the battery heater is integrated into the drive battery, in particular the duration of the switching cycle can be fixedly adjusted to the electrolyte used in the battery cells. A third aspect of the invention relates to a motor vehicle having an electric drive motor for driving the motor vehicle and a drive battery connected to the electric drive motor according to the second aspect of the invention.

drawings

Brief description of the pictures

The invention will be explained in more detail below with reference to some figures. Show it:

Fig. 1 shows a first embodiment of the invention;

Fig. 2 shows a second embodiment of the invention based on four partial images; and

3 shows a diagram with time profiles for illustrating the method according to the invention.

Detailed description of the pictures

Fig. 1 shows a first embodiment of the invention. A drive battery

10 with a plurality of battery cells connected in series is connected to a battery heater 12, which in turn is in turn connected to the electric drive motor 1 1. The battery heater can be advantageously integrated in the drive battery 10 or in a (not shown) inverter. The invention is based on the recognition that the electric drive motor

1 1 itself represents an inductance which can be used for inductive battery heating.

Fig. 2 shows a second embodiment of the invention based on four partial images. The battery heater of the second embodiment has four switches 14-1 to 14-4, which are connected between the drive battery 10 and the inductance 13 of the electric drive motor 1 1. The four switches 14-1 to 14-4 are arranged so that the inductance 13 can be connected to the drive battery 10 in two different orientations. In the first partial illustration, the switches 14-1 and 14-2 are closed and the switches 14-3 and 14-4 are opened, so that a slowly rising current flows from the drive battery 10 into the inductance 13, which forms a magnetic field in the Inductor 13 builds.

Subsequently, the switches 14-1 and 14-2 are opened and the switches 14-3 and 14-4 are closed (Fig. 2B). As the inductance 13 counteracts a change in the current flowing through it, it maintains the last current flowing by feeding a corresponding resonance current from its magnetic field. Since the inductor 13 is now connected in antiparallel to the first orientation with the drive battery 10 due to the changed switch states in the second orientation, the resonant current flows back into the drive battery 10, so that the previously removed electrical energy is supplied again except for line losses. Once the magnetic field of the inductance 13 has dissipated, again a current flows from the drive battery 10 through the inductance 13 (FIG. 2C) connected to the drive battery 10 in the second orientation, which builds up a magnetic field of opposite sign. After a certain time, the inductance 13 is in turn connected to the drive battery 10 in the first orientation, so that the energy stored in the magnetic field is stored in the resonant current as resonance current

Drive battery 10 is fed back (Fig. 2D). In this way, it is possible to alternately discharge and recharge the traction battery 10 without significant loss of electrical energy outside of the traction battery 10. The battery heater of the invention dispenses with additional inductance by using the inductance 13 of the drive motor 1 1 for the battery heater 12.

In the sub-figures Fig. 2A to 2D stream arrows are entered, indicate the direction of the sign of the current flowing in the respective conductor section current. The sign is also explicitly as part of the name of the

Electricity indicated.

3 shows a diagram with time profiles for illustrating the method according to the invention. On the abscissa four modes are indicated as M1, M2, M3 and M4. In each case a partial diagram S1 to S4, the switching states of the first to fourth switches 14-1 to 14-4 of FIG. 2 are shown, wherein a positive value should mean a closed switch and a value equal to zero an open switch. In each case a partial diagram current waveforms for the battery current I _B ATT and the current through the inductance, L _L , are shown.

In switching state M1, the first switch 14-1 and the second switch 14-2 are closed and the third switch 14-3 and the fourth switch 14-4 are open. A positive current from the drive battery 10 begins to flow through the inductor 13. In the following second switching state M2, the third and fourth switches 14-3, 14-4 are now closed and the first and second switches 14-1, 14-2 are opened so that the inductance 13 is connected in anti-parallel with the drive battery 10. The inductor 13 acts as an inertial element of a change in the current flowing through it, so that it decreases only slowly, the inductor 13 feeds the resonance current from its magnetic field. Due to the antiparallel connection of the inductance 13 with the drive battery 10, the sign of the flowing current is reversed from the viewpoint of the drive battery 10, so that the resonant current now flows into the drive battery 10 and this again supplies the previously removed electrical energy. After the magnetic field has been reduced, a current now begins to flow from the drive battery 10 into the inductance 13, wherein the current strength steadily increases and a magnetic field of opposite sign to the switching state M1 is established (switching state M3). In this case, the switching states of the first to fourth switches 14-1 to 14-4 remain unchanged relative to the second switching state M2. After a while, the inductor 13 is again connected to the drive battery in the first orientation by re-closing the first and second switches 14-1 and 14-2 and re-opening the third and fourth switches 14-3 and 14-4 (Switching state M4). The resonant current fed by the inductance 13 from the magnetic field now flows from the point of view of the drive battery, again with the opposite sign and thus into the drive battery 10, so that the electrical energy removed in the switching state M3 is supplied again. After the fourth switching state M4, the method continues periodically with the switching state M1.

Claims

claims

1 . A battery heater (12) for heating a drive battery (10) of a motor vehicle with an electric drive motor (1 1) for driving the motor vehicle, with a first connection for the drive battery (10) and a second connection for the electric drive motor (1 1), wherein the first terminal and the second terminal each having a first pole and a second pole, characterized in that the battery heater (12) is formed, in a first time period (M1) of a switching cycle, the first pole of the first terminal with the first Pol of the second terminal and the second pole of the first terminal to be electrically connected to the second pole of the second terminal and thus to flow a current of a first sign, and in a subsequent to the first time period (M1) second time period (M2) of the switching cycle the second pole of the first terminal with the first pole of the second terminal and the first pole of the first terminal to be electrically connected to the second pole of the second terminal and thus to flow a resonant current of a second sign opposite to the first sign.

The battery heater (12) of claim 1, further comprising, in a third time period of the switching cycle following the second time period (M2), connecting the second terminal of the first terminal to the first terminal of the second terminal and the first terminal of the first terminal second pole of the second terminal electrically connected and so flow a current of the first sign, and in one on the third

Period of time (M3) following the fourth period of time (M4) of the switching cycle to electrically connect the first terminal of the first terminal to the first terminal of the second terminal and the second terminal of the first terminal to the second terminal of the second terminal, and so a resonance of the second Sign to flow. The battery heater (12) of claim 1 or 2, configured to periodically alternately connect the first pole of the first terminal to the first pole of the second terminal and the second pole of the first terminal to the second pole of the second terminal and the second pole of the first Terminal with the first pole of the second terminal and the first pole of the first terminal to electrically connect to the second pole of the second terminal.

The battery heater (12) of any one of the preceding claims, for a drive battery (10) having an electrolyte in which a reciprocal of a Debye-Falkenhagen cut-off frequency of the electrolyte is longer than the switching cycle.

The battery heater (12) of one of the preceding claims, comprising a first switch (14-1) having a first electrode connected to the first pole of the first terminal and a second electrode connected to the first pole of the second terminal, a second switch (14-2) having a first electrode connected to the second pole of the first terminal and a second electrode connected to the second pole of the second terminal, a third switch (14-3) connected to the first pole of the first terminal a first electrode connected to the second pole of the second terminal, and a fourth switch (14-4) having a first electrode connected to the second pole of the first terminal and a second electrode connected to the second pole of the second terminal In addition, the first to fourth switches (14-1, 14-2, 14-3, 14-4) each have a control connected to a controller have ll electrode.

The battery heater (12) of claim 5, wherein the control electrode of the first switch (14-1) is connected to the control electrode of the second switch (14-2) and the control electrode of the third switch (14-3) is connected to the control electrode of the fourth Switch (14-4) are connected.

A drive battery (10) with a battery heater (12) according to one of the preceding claims. A motor vehicle having an electric drive motor (1 1) for driving the motor vehicle and a drive battery (10) connected to the electric drive motor (1 1) according to claim 7.