DE102021211418A1 - Battery heater, method of heating a battery - Google Patents

Abstract

The invention relates to a battery heating device (60) for heating a battery (5), which has an internal voltage source (Vi), an internal resistance (Ri), an internal inductance (Li), a positive pole (22) and a negative pole (21 ), wherein the battery heating device (60) comprises a capacitor (CA) which has a positive terminal (CA+) and a negative terminal (CA-), a first switching element (61) and a second switching element (62), wherein a first Connection of the first switching element (61) is electrically connected to a node (25) which can be electrically connected to one of the poles (21, 22) of the battery (5), a second connection of the first switching element (61) is electrically connected to one of the terminals (CA+, CA-) of the capacitor (CA), a first terminal of the second switching element (62) is electrically connected to the other of the terminals (CA+, CA-) of the capacitor (CA) and electrically to the other of the poles ( 21, 22) of the battery (5) can be connected, and a second connection of the second switching element (62) is electrically connected to the node (25), and wherein the battery heating device (60) is set up so that by its activation an alternating current (I) is generated which flows through the battery (5) during heating of the battery (5) when the node (25) is electrically connected to one of the poles (21, 22) of the battery (5) and the first terminal of the second switching element (62) is electrically connected to the other of the poles (21, 22) of the battery (5).

Description

The invention relates to a battery heating device for heating a battery, which has an internal voltage source, an internal resistance, an internal inductance, a positive pole and a negative pole. The invention also relates to a method for heating a battery.

State of the art

It is becoming apparent that more and more electrically powered vehicles will be used in the future. Such electrically powered vehicles, such as hybrid vehicles and electric vehicles, each include a battery system, such as a 48V battery system, for powering or traction of the vehicle.

The battery cells of the battery system are lithium-ion battery cells, for example. At low operating temperatures of lithium-ion battery cells of less than 0° C., for example, they have a relatively high internal resistance. A high internal resistance results in severe limitations when operating the battery system at low temperatures, especially when the motor vehicle is started cold in winter. As the operating temperature increases, the internal resistance of the lithium-ion battery cells drops significantly.

The document US 2014/0268959 A1 describes a bi-directional power converter that can be used in an electric vehicle to perform AC-DC power conversion to charge the battery of the electric vehicle and DC-AC power conversion to output power to operate external electrical loads.

Disclosure of Invention

According to the invention, a battery heating device for heating a battery is proposed. In this case, the battery has an internal voltage source, an internal resistance, an internal inductance, a positive pole and a negative pole.

The battery comprises one or more battery cells, which can be connected to one another both in series and in parallel within the battery module. The battery cells are preferably designed as lithium ion battery cells. The battery cells simulate electrical voltage sources with temperature-dependent internal resistances. Electrical lines within the battery also have electrical resistance and inductance. The electrical voltage sources of the battery cells form the internal voltage source of the battery. The internal resistance of the battery cells and the resistance of the electrical lines form the internal resistance of the battery. The inductance of the electrical lines forms the internal inductance of the battery. Optionally, the battery can also have a coil with an additional inductance.

Here, the battery heater includes a capacitor having a positive terminal and a negative terminal, a first switching element, and a second switching element. The switching elements each have three connections, with a switching path being formed between a first connection and a second connection, which can be controlled by means of a third connection.

A first connection of the first switching element is electrically connected to a node that can be electrically connected to one of the poles of the battery, and a second connection of the first switching element is electrically connected to one of the terminals of the capacitor. A first terminal of the second switching element is electrically connected to the other of the terminals of the capacitor and electrically connectable to the other of the poles of the battery, and a second terminal of the second switching element is electrically connected to the node.

For example, the node electrically connected to the first terminal of the first switching element may be connected to the positive terminal of the battery and the second terminal of the first switching element is connected to the positive terminal of the capacitor. The first connection of the second switching element is then connected to the negative pole of the battery and to the negative terminal of the capacitor. The negative pole of the battery is electrically connected to the negative terminal of the capacitor.

The battery heating device is set up to generate an alternating current that flows through the battery during heating of the battery when the node point is electrically connected to one of the poles of the battery and the first connection of the second switching element is electrically connected to the other connected to the battery poles. When heating the battery, current, voltage and temperature are measured and monitored.

The interconnection of the switching elements of the arrangement enables several switching states of the battery when the arrangement is electrically connected to the battery, ie the node is elec electrically connected to one of the poles of the battery, while the first terminal of the second switching element is electrically connected to the other of the poles of the battery. For example, in a first switching state, when the first switching element is open and the second switching element is closed, a current can flow through the internal resistance and the internal inductance of the battery, but not to the capacitor and to. In a second switching state, when the first switching element is closed and the second switching element is open, a current can flow through the internal resistance and the internal inductance of the battery and through the capacitor. In a third switching state, when the first switching element is open and the second switching element is open, no current can flow through the battery module.

The first and second switching elements are preferably in the form of semiconductor switches. For example, the first switching element and the second switching element can be in the form of field effect transistors and each have a SOURCE connection, a DRAIN connection and a GATE connection. The switching elements are interconnected in such a way that the first connection is the SOURCE connection, the second connection is the DRAIN connection and the third connection is the GATE connection. For example, the switching elements are MOSFETs, in particular n-channel MOSFETs of the enhancement type.

The battery heating device according to the invention preferably also includes a precharging circuit, a first connection of the precharging circuit being electrically connected to the node or to the first connection of the first switching element and a second connection of the precharging circuit being electrically connectable to one of the poles. In this case, the other pole of the battery can be electrically connected to the first connection of the second switching element. With the pre-charge circuit, a capacitor with a larger capacity can be selected. The pre-charging circuit can advantageously be in the form of a MOSFET. The MOSFET is used in linear mode, which switches on after the capacitor has been precharged. Linear operation means that the MOSFET is operated in the saturation range. If the second switching element breaks down, this MOSFET can also be used as a redundant disconnector, in order to prevent a permanent short circuit in the battery or the battery cells in the event of a fault. Alternatively, a switchable resistor or a constant current source is also conceivable, which is completely short-circuited by a further switch of the pre-charging block after the pre-charging has been completed.

Preferably, the battery heating device according to the invention also includes an additional inductor. In this case, a first connection of the additional inductance is electrically connected to the node or, if present, electrically connected to the second connection of the precharging circuit. A second connection of the additional inductance can be electrically connected to one of the poles of the battery. In this case, the other pole of the battery can be electrically connected to the first connection of the second switching element.

A further aspect of the invention is the provision of a method for heating a battery using the battery heating device according to the invention. Correspondingly, features described in the context of the battery heating device apply to the method and vice versa, features described in the context of the method apply to the battery heating device.

With the method according to the invention, after the electrical connection of the junction point to one of the poles of the battery (5) and the first connection of the second switching element, the battery heating device is electrically controlled to the other pole of the battery in such a way that an alternating current flows through the battery during heating the battery flows.

Said alternating current thus flows in particular through the internal resistance of the battery. The alternating current causes a voltage drop across the internal resistance of the battery and thus across the internal resistance of the battery cells. As a result, electrical energy is converted into heat in the internal resistance of the battery and thus in the internal resistance of the battery cells. This causes the battery, in particular the battery cells of the battery, to heat up. As a result, the internal resistance of the battery cells decreases as the operating temperature rises.

The battery heating device is preferably activated in a plurality of successive phases. The battery heating device is controlled in such a way that during a first phase electrical energy is transferred from the internal voltage source of the battery to the internal inductance of the battery, during a second phase electrical energy is transferred from the internal inductance of the battery to the capacitor, and during in a third phase, electrical energy is transferred from the capacitor to the battery's internal voltage source.

The battery heating device is preferably controlled in such a way that during a first phase the first switching element is opened and the second switching element is closed, during a second phase the first switching element is closed and the second switching element is open and during a third phase the first switching element is closed and the second switching element is open.

During the first phase, the current flows through the internal voltage source, through the internal resistance, through the internal inductance and through the second switching element. During the second phase, the current flows through the internal voltage source, through the internal resistance, through the internal inductance, through the first switching element and through the capacitor. During the third phase, the current flows through the internal voltage source, through the internal resistance, through the internal inductance, through the first switching element and through the capacitor. The current flows in the opposite direction during the third phase as during the second phase.

The battery heating device is preferably controlled in such a way that the first switching element is open and the second switching element is open during a first intermediate phase between the first phase and the second phase. It is also conceivable that the first switching element is open and the second switching element is open during a second intermediate phase between the third phase and the first phase. With the first and the second intermediate phase, high losses caused by the closing and opening of the switching elements can be avoided.

The battery heating device is preferably controlled in such a way that the first phase, the second phase and the third phase are repeated cyclically.

The invention also relates to the use of the battery heating device according to the invention, which heats a battery of a vehicle or an electrical device, such as power tools or gardening tools, using the method according to the invention.

Advantages of the Invention

The invention makes it possible to warm up the batteries before use by means of a plug-on device.

Using the battery heating device according to the invention and the method according to the invention, it is possible in a battery system for a motor vehicle to heat the battery cells of the battery to a suitable operating temperature in a relatively short time. This reduces the internal resistance of the battery cells, and the battery system of the motor vehicle is ready for use in a relatively short time. The battery heating device according to the invention can also be used with 12V lead-acid accumulators in the vehicle in order to facilitate the starting process of the vehicle in cold ambient temperatures.

By means of the method according to the invention, the battery heating device according to the invention can be operated in a similar way to a DC/DC converter or like a step-up converter. The alternating current that flows during this process always flows through the internal resistance of the battery and thus through the internal resistance of the battery cells. The resulting voltage drop converts electrical energy into heat at the internal resistance of the battery cells, causing the battery cells to heat up. During this process, electrical energy is transferred between the voltage source, the internal inductor, and the capacitor. The electrical energy is thus shifted between the battery and the capacitor. With the exception of the conversion of electrical energy into heat at the internal resistance of the battery cells, there are no other significant losses. The battery is therefore only slightly discharged.

character list

Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

• 1 eine schematische Darstellung der erfindungsgemäßen Batterieheizvorrichtung, die mit einer Batterie elektrisch verbunden ist,
• 2 eine schematische Darstellung der erfindungsgemäßen Batterieheizvorrichtung, wobei die Vorladeschaltung als MOSFET ausgebildet ist,
• 3 eine schematische Darstellung der erfindungsgemäßen Batterieheizvorrichtung während einer ersten Phase des erfindungsgemäßen Verfahrens,
• 4 eine schematische Darstellung der erfindungsgemäßen Batterieheizvorrichtung während einer zweiten Phase des erfindungsgemäßen Verfahrens und
• 5 eine schematische Darstellung der erfindungsgemäßen Batterieheizvorrichtung während einer dritten Phase des erfindungsgemäßen Verfahrens.

Show it:

• 1 a schematic representation of the battery heating device according to the invention, which is electrically connected to a battery,
• 2 a schematic representation of the battery heating device according to the invention, wherein the pre-charging circuit is designed as a MOSFET,
• 3 a schematic representation of the battery heating device according to the invention during a first phase of the method according to the invention,
• 4 a schematic representation of the battery heating device according to the invention during a second phase of the method according to the invention and
• 5 a schematic representation of the battery heating device according to the invention during a third phase of the method according to the invention.

Embodiments of the invention

In the following description of the embodiments of the invention, the same or similar elements are denoted by the same reference symbols, with a repeated description of these elements being dispensed with in individual cases. The figures represent the subject matter of the invention only schematically.

1 shows a schematic representation of a battery heating device 60 according to the invention, which is electrically connected to a battery 5 . The battery 5 comprises a plurality of battery cells, not shown here, which can be connected to one another both in series and in parallel within the battery 5, a disconnector 14, a positive pole 22 and a negative pole 21. The poles 21, 22 and the disconnector 14 can the battery heating device 60 according to the invention can be electrically connected to the battery 5 and separated from the battery 5 .

Each of the battery cells of the battery 5 simulates an electrical voltage source with an internal resistance. The electrical voltage sources of the battery cells form an internal voltage source Vi. The internal resistances of the battery cells and an electrical resistance of electrical lines form an internal resistance Ri, inductances of the electrical lines and the battery cells form an internal inductance Li. Optionally, a coil with an additional inductance can also be provided. In this case, the inductances of the electrical lines and the battery cells together with the inductance of the coil form the internal inductance Li.

The battery 5 thus has the internal voltage source Vi and the internal inductance Li. When idling, a voltage supplied by the internal voltage source Vi is present between the positive pole 22 and the negative pole 21 . The circuit breaker 14 can include a main pre-charging circuit.

The battery heating device 60 according to the invention includes a first switching element 61, a second switching element 62, a pre-charging circuit 63, an additional inductance Lz and a capacitor CA, which includes a positive terminal CA+ and a negative terminal CA-. The switching elements 61, 62 each have three connections, with a switching path being formed between a first connection and a second connection, which can be controlled by means of a third connection.

In the present case, the first switching element 61 and the second switching element 62 are embodied as field effect transistors. The switching elements 61, 62 each have a SOURCE connection, a DRAIN connection and a GATE connection. The switching elements 61, 62 are interconnected in such a way that the first connection is the SOURCE connection, the second connection is the DRAIN connection and the third connection is the GATE connection.

In the present case, the switching elements 61, 62 are n-channel MOSFETs of the enhancement type. The switching elements 61, 62 each have a switching path and an inverse diode connected in parallel with the switching path. The inverse diode, which is also referred to as the body diode, is created in every MOSFET due to its internal structure and is not an explicit component.

The first connection of the first switching element 61 is connected to a node 25 . The second terminal of the first switching element 61 is connected to the positive terminal CA+ of the capacitor CA. The first terminal of the second switching element 62 is connected to the negative pole 21 of the battery 5 and to the negative terminal CA- of the capacitor CA. The second connection of the second switching element 62 is connected to the node 25 . The node 25 is connected to the positive pole 22 of the battery 5 via the series connection of the additional inductance Lz and the pre-charging circuit 63 . In this case, the pre-charging circuit 63 can be in the form of a MOSFET. The MOSFET is used in linear mode, which turns on after the capacitor CA has been precharged.

2 also shows a schematic representation of the battery heating device 60 according to the invention 2 differs from the illustration 1 in that the pre-charging circuit 63 in 2 is designed as a MOSFET, which is used in linear operation and turns on after the pre-charging of the capacitor CA.

3 , 4 and 5 each show a battery heating device 60 according to the invention during a phase of the method according to the invention. To simplify the illustration, the first and second switching elements 61, 62 shown in 1 and 2 were shown as MOSFETs, and the precharge circuit 63 shown in 2 also represented as a MOSFET, in 3 , 4 and 5 each shown as a switch. During the method according to the invention, the node 25 is electrically connected to the positive pole 22 via the pre-charging circuit 63 designed as a MOSEFT. That is, the pre-charge circuit 63 formed as a MOSFET turns on after pre-charging the capacitor CA during the process. In 3 , 4 and 5 this is represented by a closed switch.

3 shows a schematic representation of the battery heating device 60 according to the invention during a first phase of the method according to the invention. During the first phase, the first switching element 61 is open and the second switching element 62 is closed. A current I flows through the internal voltage source Vi, through the internal resistance Ri, through the internal inductance Li, through the pre-charging circuit 63 and through the second switching element 62 during the first phase.

After the end of the first phase, the second switching element 62 is opened and a first intermediate phase begins, in which the first switching element 61 and the second switching element 62 are open. After the end of the first intermediate phase, the first switching element 61 is closed and a second phase begins.

4 shows a schematic representation of the battery heating device 60 according to the invention during the second phase of the method. During the second phase, the first switching element 61 is closed and the second switching element 62 is open. A current I flows through the internal voltage source Vi, the internal resistor Ri, the internal inductance Li, the pre-charging circuit 63, the first switching element 61 and the capacitor CA during the second phase.

5 shows a schematic representation of the battery system 10 during a third phase of the method. During the third phase, the first switching element 61 is closed and the second switching element 62 is open. A current I flows through the internal voltage source Vi, the internal resistor Ri, the internal inductor Li, the precharge circuit 63, the first switching element 61, and the capacitor CA during the third phase. However, the current I flows in the opposite direction during the third phase as during the second phase.

After the end of the third phase, the first switching element 61 is opened and a second intermediate phase begins, in which the first switching element 61 and the second switching element 62 are open. After the end of the second intermediate phase, the second switching element 62 is closed and another first phase begins.

The invention is not limited to the exemplary embodiments described here and the aspects highlighted therein. Rather, within the range specified by the claims, a large number of modifications are possible, which are within the scope of expert action.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US20140268959A1 [0004]

Claims (11)

Battery heating device (60) for heating a battery (5), which has an internal voltage source (Vi), an internal resistance (Ri), an internal inductance (Li), a positive pole (22) and a negative pole (21), wherein the battery heater (60) comprises a capacitor (CA) having a positive terminal (CA+) and a negative terminal (CA-), a first switching element (61) and a second switching element (62), wherein a first connection of the first switching element (61) is electrically connected to a node (25) which can be electrically connected to one of the poles (21, 22) of the battery (5), a second terminal of the first switching element (61) is electrically connected to one of the terminals (CA+, CA-) of the capacitor (CA), a first terminal of the second switching element (62) is electrically connected to the other of the terminals (CA+, CA-) of the capacitor (CA) and is electrically connectable to the other of the poles (21, 22) of the battery (5), and a second connection of the second switching element (62) is electrically connected to the node (25), and wherein the battery heating device (60) is set up such that an alternating current (I) is generated by its activation, which during the heating of the battery ( 5) flows through the battery (5) when the node (25) is electrically connected to one of the poles (21, 22) of the battery (5) and the first terminal of the second switching element (62) is electrically connected to the other of the poles ( 21, 22) of the battery (5). Battery heater (60) after claim 1 , characterized in that the first and second switching element (61, 62) are designed as semiconductor switches. Battery heater (60) after claim 1 or 2 , further comprising a pre-charging circuit (63), wherein a first terminal of the pre-charging circuit (63) is electrically connected to the node (25) or to the first terminal of the first switching element (61) and a second terminal of the pre-charging circuit (63) is electrically connected to a the poles (21, 22) can be connected. Battery heater (60) after claim 3 , characterized in that the pre-charging circuit (63) is designed as a MOSFET. Battery heater (60) according to any one of Claims 1 until 4 , further comprising an additional inductor (Lz), wherein a first terminal of the additional inductor (Lz) is electrically connected to the node (25) or, if present, electrically connected to the second terminal of the pre-charging circuit (63) and a second terminal the additional inductance (Lz) can be electrically connected to one of the poles (21, 22) of the battery (5). Method for heating a battery (5) using a battery heating device (60) according to one of the preceding claims, characterized in that the battery heating device (60) after the electrical connection of the junction point (25) to one of the poles (21, 22) of the battery (5) and the first connection of the second switching element (62) is electrically controlled with the other of the poles (21, 22) of the battery (5) in such a way that an alternating current (I) flows through the battery (5) during the heating of the Battery (5) flows. procedure after claim 6 , characterized in that the battery heating device (60) is controlled such that during a first phase electrical energy from the internal voltage source (Vi) of the battery (5) to the internal inductance (Li) of the battery (5) is transferred, during a second phase electrical energy is transferred from the internal inductance (Li) of the battery (5) to the capacitor (CA), and during a third phase electrical energy is transferred from the capacitor (CA) to the internal voltage source (Vi) of the battery (5) is transferred. procedure after claim 6 or 7 , characterized in that the battery heating device (60) is controlled in such a way that during a first phase the first switching element (61) is opened and the second switching element (62) is closed, during a second phase the first switching element (61) is closed and the second Switching element (62) is open and during a third phase the first switching element (61) is closed and the second switching element (62) is open. procedure after claim 8 , characterized in that the battery heating device (60) is controlled in such a way that during a first intermediate phase between the first phase and the second phase the first switching element (61) is opened and the second switching element (62) is opened and/or during a second intermediate phase between the third phase and the first phase, the first switching element (61) is open and the second switching element (62) is open. procedure after claim 8 or 9 , characterized in that the battery heater (60) is controlled such that the first phase, the second phase and the third phase are repeated cyclically. Use of a battery heater (60) according to any one of Claims 1 until 5 Which with a method according to one of Claims 6 until 10 a battery (5) of a vehicle or an electrical device heats.

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