WO2013113438A1

WO2013113438A1 - Charge equalization for cells of a battery

Info

Publication number: WO2013113438A1
Application number: PCT/EP2012/075066
Authority: WO
Inventors: Stefan Butzmann
Original assignee: Robert Bosch Gmbh; Samsung Sdi Co., Ltd.
Priority date: 2012-02-01
Filing date: 2012-12-11
Publication date: 2013-08-08
Also published as: DE102012201404A1

Abstract

The invention relates to a charge equalization method for battery cells (50) of a battery by switching discharge currents. A discharge current flows across a resistor (30) that is connected in parallel to a battery module (40) having at least one battery cell (50) and is switched by means of a transistor (20) associated with the battery module (40), the transistor (20) being switched on and off by means of a pulse-width-modulated signal. The invention further relates to a device (10) for carrying out the method, a battery comprising the device (10) and a vehicle comprising the device (10) or the battery.

Description

description

title

CHARGE COMPENSATION FOR CELLS OF A BATTERY The present invention relates to a method and a corresponding device for charge compensation of the battery cells of a battery. In particular, the invention relates to a method and a device for charge equalization of at least one battery module comprising at least one battery cell of a battery. The invention also relates to a battery with the device according to the invention. Furthermore, the invention relates to a vehicle having a device according to the invention

Battery.

Background Art Lithium ion batteries for electric and hybrid vehicles include

Typically, a plurality of series-connected battery modules, each comprising at least one battery cell, wherein the battery modules for

Purposes of balancing each with a

Charge balancing circuit (Balancingschaltung) are provided.

A known from the prior art device 10 for

Charge compensation of a battery module 40 is shown in FIG. The battery module 40 shown in FIG. 1 comprises a single battery cell 50.

By means of the vertically marked points it is pointed out that in the same battery further battery modules can be present.

In the case of the balancing circuit 10 shown in FIG. 1, a transistor 20 is actuated for the purpose of balancing, which then has a resistance

(Balancing resistor) 30 parallel to the demagnified battery cell 50th

on. In the balancing circuit 10 shown in FIG

Resistor 30 between a pole (not labeled) of the battery cell 50 and the collector terminal (not marked) of the transistor 20, which in turn is connected at its emitter terminal (not marked) to the other pole (not marked) of the battery cell 50. The balancing circuit 10 comprises a control device 70 which is designed to detect the battery cell voltage and to turn on the transistor 20 based on the detected battery cell voltage in order to partially discharge the battery cell 50 via the resistor 30 for the purpose of charge equalization. For this purpose, the transistor 20 at its base terminal (not

marked) with a first connection (not marked) of the

Control device 70 connected. The controller 70 includes an analog-to-digital converter (not shown) configured to convert the input voltage applied to the controller 70 into digital data

implement, by means of the control device 70 for detecting the

Battery cell voltage to be evaluated.

The balancing circuit 10 further comprises a capacitor 60 connected between a second and a third terminal (not marked) of FIG

Control device 70 is connected. The balancing circuit 10 also comprises two further resistors 31, 32. In this case, the further resistor 31 is connected between the terminal (not marked) of the resistor 30, at which the resistor 30 is connected to one pole of the battery cell 50, and a terminal (not marked). of the capacitor 60 connected. Further, the other additional resistor 32 is connected between the emitter terminal of the transistor 20 and the other terminal (not labeled) of the capacitor 60.

After the transistor 20 has been turned on, during a discharge of the battery cell 50, a power loss is generated in the balancing resistor 30, which heats it. In FIG. 2, the signal S is for turning on the transistor

20 as a function of the time t shown. In FIG. 3, the temperature T of the balancing resistor 30 after switching on the transistor 20 is shown as a function of the time t. For the life of the resistor 30 in addition to the amount of power loss and thus the temperature H and the number of Balancingvorgänge and the gradient of the

Temperature increase of importance. The document DE 10 2009 028 977 A1 discloses a battery system which comprises at least two DC / DC converters and at least two battery modules, wherein a battery module is connected to a respective first input of a DC / DC converter and wherein the at least two battery modules via an electrical connection for the purpose of charge equalization between the

Battery modules are connected together. A battery module includes a single battery cell or a circuit of multiple battery cells.

The DC / DC converters make it possible to input a large number of

Battery modules parallel and / or in series.

At a voltage difference between the battery modules through the electrical connection equalizing currents flow, which align the voltage between the battery modules to each other. At the same voltage of all

Battery modules, that is, in the balanced state of charge, however, flow no compensation currents. The electrical connection can therefore remain in the case of the balanced state. The electrical connection between the battery modules may comprise an additional resistance element or be formed by means of a simple wire. Again, a power loss is generated during the discharge of the battery cell 50. Again, for the life of the electrical connection in particular the amount of power loss, which is generated for example by a contact resistance or the additional resistance element, is important.

Disclosure of the invention

According to the invention, a method for charge equalization of battery cells of a battery by switching a discharge current or by switching discharge currents is described. In this case, a discharge current flows or

Charge compensation current in each case via a resistor connected in parallel with a battery module, which has at least one battery cell. The discharge current is switched by means of a transistor associated with the battery module, wherein the transistor is switched on and off according to a pulse width modulated signal. Illustrated clearly, there is provided a method for charge equalization of at least one battery module comprising at least one battery cell, wherein for discharging the battery module, a transistor associated with the battery module, which switches a battery module associated resistor in parallel to the battery module is switched on in the on state. According to the invention, the transistor is switched on and off by means of a pulse width modulated signal of the battery module.

In particular, the method according to the invention can also be advantageously used during a discharging process of the battery or during a charging process of the battery.

According to the invention, a device is also provided for the charge balance of at least one battery module comprising at least one battery cell. The device according to the invention comprises a

Control device which is adapted to detect the battery module voltage and for discharging the battery module or for charge compensation, a transistor associated with the battery module, which in the on state, a battery module associated resistance with the

Battery module switches in parallel, turn on. According to the invention

Control device further aligned during the

Charge compensation process of the battery module to generate a pulse width modulated signal and the transistor by means of the generated

Switch pulse width modulated signal on and off.

According to the invention, a battery is further provided which comprises at least one battery module comprising at least one battery cell

Battery module associated transistor, a battery module associated resistance and the inventive device for charge compensation of the battery module comprises.

Advantageous developments of the invention are specified in the subclaims and described in the description. In a particularly preferred embodiment of the invention, the transistor is switched on and off by means of the pulse-width-modulated signal, which has an increasing pulse duration.

Advantageously, by means of the method according to the invention, it can first be achieved that the gradient of the temperature rise of that resistor (balancing resistor) is reduced, which is connected in parallel to the battery module for partially discharging or for equalizing the charge of a battery module of a battery by means of a transistor (balancing transistor). For this purpose, as explained above, the balancing transistors are switched on or controlled in a pulse-width-modulated manner, wherein in an advantageous embodiment of the invention the pulse duration or the duty cycle (duty cycle) of the

Pulse width modulation (PWM) is selected increasing. The rise of

Temperature of the Balancingwiderstandes is proportional to the increase in the pulse duration of the pulse modulation.

The controlled by the pulse width modulation switching on and off of the balancing transistor leads to a reduction of the temperature gradient of Balancingwiderstandes and correspondingly to smaller temperature strokes.

In a further particularly preferred embodiment of the invention, the transistor is switched on and off by means of the pulse-width-modulated signal, which has a frequency exceeding at least one predetermined threshold.

The fact that the frequency of the pulse width modulation is selected as high as possible, the height of the temperature strokes of Balancingwiderstandes can be further reduced significantly. The controlled according to a pulse width modulation on and off the

Balancingtransistors can be made in particular software controlled.

Another aspect of the invention relates to a device for charge equalization of at least one battery module, in which the control device a

Pulse width modulation unit, which is adapted to the inventive pulse width modulated signal for switching on and off of the transistor to generate and the transistor by means of the generated

Switch pulse width modulated signal on and off.

In a particularly preferred embodiment of the invention is the

Control device of the device according to the invention designed as an integrated circuit in which in particular the pulse width modulation unit is implemented.

Thus, advantageously controlled by the pulse width modulation switching on and off of the balancing transistor by means of a pulse width modulation unit, preferably in an application-specific integrated

Balancing-ASIC circuit of the battery module of the battery is implemented. In particular, the pulse width modulation unit may also be implemented in the integrated circuit (IC) for detecting the battery module voltage. Thus, according to the invention enables the

Temperature gradient of the Balancingwiderstandes of the integrated circuit in which the pulse width modulation unit is integrated, can be controlled autonomously.

In a further embodiment of the invention, the pulse width modulation unit implemented in this way can also be used to determine the magnitude of the

Adjusting the temperature strokes of the balancing resistor.

The device according to the invention can be used in its entirety in the

be integrated battery according to the invention.

According to the invention, there is further provided a vehicle, in particular an electric or hybrid vehicle, comprising a battery with at least one battery module comprising at least one battery cell, a transistor associated with the battery module, a resistor associated with the battery module and a device for compensating the charge

Battery module or a battery according to the invention comprises. The battery comprising the at least one battery module can, according to a preferred embodiment, be a lithium-ion battery. drawings

Embodiments of the invention will be explained in more detail with reference to the drawings and the description below. Show it:

1 shows a battery module with a battery cell and a device for charge compensation of the battery module according to the prior art,

Figure 2 is a known from the prior art and shown in dependence on the time course of a signal for switching on of the

Device comprising FIG. 1 comprising a balancing transistor,

FIG. 3 shows a curve of the temperature of a balancing resistor encompassed by the device from FIG. 1, which is known from the prior art and is shown as a function of time, which is parallel to the battery module from FIG. 1 through the balancing transistor switched on by means of the signal from FIG is switched

4 shows a battery module with a battery cell and a device for charge compensation of the battery module according to a first embodiment of the invention,

Figure 5 shows a function of time shown course of a

signal according to the invention for switching on a balancing transistor comprised by the device according to the first embodiment of the invention, and

FIG. 6 shows a course of the temperature, as a function of time, of a balancing resistance encompassed by the device according to the first embodiment of the invention, which is determined by means of the

According to the invention signal 5 switched balancing transistor is connected in parallel to the battery module of Figure 4. Embodiments of the invention

In the figure 4 is a device 10 for charge compensation of a

Battery module 40 shown according to a first embodiment of the invention. The battery module 40 comprises a single one as shown

Battery cell 50, but may also include two or more battery cells. By means of the vertically marked points it is pointed out that further battery modules can be present in the same battery (not marked).

In order to discharge the battery cell 50, a transistor (balancing transistor) 20 assigned to the battery cell 50, which in the switched-on state switches a resistance (balancing resistor) 30 assigned to the battery cell 50 in parallel to the battery cell 50, by means of a pulse width modulated signal at least during a discharge process of the battery cell 50 - and off.

The device 10 comprises a control device 70, which the

Battery cell voltage detected and based on the detected

Battery cell voltage the balancing transistor 20 on and off.

The control device 70 generates the pulse width modulated signal, by means of which the balancing transistor 20 at least during a

Discharge process of the battery cell 50 is turned on and off. In this case, the balancing transistor 20 via its emitter or collector terminal

(not labeled) connected in series with the balancing resistor 30 and connected via its base terminal (not labeled) to a first terminal (not marked) of the controller 70. The control device 70 comprises an integrated circuit 71, which is in particular designed to detect the battery cell voltage. In the integrated circuit 71 is preferably a pulse width modulation unit 72nd

implemented, which is adapted to generate the pulse width modulated signal for switching on and off of the balancing transistor 20 and the

Balancing transistor 20 by means of the generated pulse-width modulated signal on and off. Between a second and a third terminal (not marked) of the control device 70, a capacitor 60 is connected. Furthermore, the

Capacitor 60 with one of its terminals also with the at a pole (not marked) of the battery cell 50 coupled terminal (not

1) of the balancing resistor 30 and with its other terminal connected to the emitter terminal of the balancing transistor 20, which is coupled to the other pole (not marked) of the battery cell 50, in each case via a further resistor 31, 32.

FIG. 5 shows the profile of the signal S according to the invention for switching on a balancing transistor 20 comprised by the device according to the first embodiment of the invention as a function of time t. The signal S is pulse width modulated and in particular has an increasing pulse duration or an increasing duty cycle (duty cycle) ID. In FIG. 5, by way of example only a single pulse duration is identified by ID.

FIG. 6 shows a profile of the temperature T of a balancing resistor 30 comprised by the device 10 according to the first embodiment of the invention as a function of the time t. The balancing resistor 30 is connected in parallel to the battery cell 50 from FIG. 4 by the balancing transistor 20 which is switched on by means of the pulse-width-modulated signal S from FIG.

The use of the pulse-width modulated signal S for switching on and off of the balancing transistor 20 initially leads to a reduction of the gradient of the increase of the Balancingwiderstandstemperatur T, but also to many smaller strokes H of the Balancingwiderstandstemperatur T. In the figure 6 is an example of a temperature H.

The increase in the temperature T of the balancing resistor 30 is proportional to the pulse duration ID of the pulse width modulated signal S. The height of the temperature H of the balancing 30 can be significantly reduced by the frequency of the pulse width modulated signal S is set as high as possible.

Claims

claims

1 . Method for charge equalization of battery cells (50) of a battery

by switching a discharge current which flows in parallel via a resistor (30) connected in parallel with a battery module (40) which has at least one battery cell (50) and by means of a battery module (40)

associated transistor (20) is switched, characterized in that the transistor (20) is switched on and off according to a pulse width modulated signal (S).

2. The method of claim 1, wherein the pulse width modulated signal (S) has an increasing pulse duration (ID).

3. The method according to any one of claims 1 or 2, wherein the

Pulse width modulated signal (S) has a predetermined threshold exceeding frequency.

4. Device (10) for charge equalization of battery cells (50) one

A battery comprising a controller (70) adapted to detect a battery module voltage and a transistor (20) associated with the battery module (40) which, when turned on, has a transistor (20) connected thereto

Battery module (40) associated resistor (30) with the battery module (40) in parallel switches to switch, characterized in that the

Control device (70) is further aligned to a

pulse width modulated signal (S) to produce and the transistor (20) by means of the generated pulse width modulated signal (S) on and

off.

5. Device (10) according to claim 4, wherein the control device (70) is adapted to the pulse width modulated signal (S) for on and

Turning off the transistor (20) with a pulse duration (ID), which increases during the charge equalization process to produce. Device (10) according to one of claims 4 or 5, wherein the

Control means (70) is adapted to generate the pulse width modulated signal (S) for turning on and off the transistor (20) at a frequency exceeding a predetermined threshold.

Device (10) according to one of claims 4 to 6, wherein the

Control device (70) comprises a pulse width modulation unit (72) which is designed to generate the pulse width modulated signal (S) for switching the transistor (20) on and off and to connect the transistor (20) by means of the generated pulse width modulated signal (S). and turn off.

Device (10) according to one of claims 4 to 7, wherein the

Control device (70) is designed as an integrated circuit (71), in which in particular the pulse width modulation unit is implemented.

Battery having at least one battery module (40) comprising at least one battery cell, a transistor (20) associated with the battery module (40), a resistor (30) associated with the battery module (40) and a device (10) aligned for charge equalization of the battery module (40). according to one of claims 4 to 8.

0. Vehicle with a battery with at least one at least one

Battery cell (50) comprising battery module (40), a the

Battery module (40) associated transistor (20), a battery module (40) associated resistor (30) and a charge equalization of the battery module (40) aligned device (10) according to one of claims 4 to 8 or with a battery according to claim 9.