METHOD AND CIRCUIT ARRANGEMENT FOR ACTIVELY BALANCING CELLS OF AN ELECTRIC ENERGY STORE

Abstract

The invention relates to an arrangement (10) for balancing the battery cells (11) of a battery string, in particular the battery cells (11) of a battery module which has a plurality of serially connected battery cells (11). The arrangement (10) has an inductor (9) for storing electric energy and switching devices (17) on the supply side for connecting the poles of a first battery cell (11) to the inductor (9) via a first connection point (13) and a second connection point (14). The arrangement can be actuated by a controller such that electric energy can be transmitted from at least one first battery cell (11) to the inductor (9) and from the inductor (9) to at least one second battery cell (11). According to the invention, the arrangement (10) has a third connection point (15) and a fourth connection point (16) in order to balance the charge and two switching devices (17) on the transfer side, wherein the inductor (9) is connected to the third connection point (15) and the fourth connection point (16) via the two switching devices (17) on the transfer side.

Claims

1. An arrangement (10) for balancing the battery cells (11) of a battery string, the arrangement (10) comprising: an inductor (9) for storing electrical energy, feed-side switching devices (17) connect connecting the poles of a first battery cell (11) by way of a first connection point (13) and a second connection point (14) to the inductor (9), and a control device configured to control electrical energy can be transmitted from an at least one battery cell (11) into the inductor (9) and from the inductor (9) to at least a second battery cell (11), a third connection point (15), a fourth connection point (16), and two transfer-side switching devices (17), wherein the inductor (9) is connected by way of the two transfer-side switching devices (17) to the third connection point (15) and the fourth connection point (16) for charge balancing.

2. The arrangement (10) as claimed in claim 1, characterized in that the third connection point (15) is connected to the highest potential and the fourth connection point (16) is connected to the lowest potential of the battery string, and the inductor (9) is connected by way of the transfer-side switching devices (17) in two polarities or flow directions (18) to the highest and the lowest potential of the battery string.

3. The arrangement (10) as claimed in claim 1, characterized in that a switching device (17) comprises a parallel connection of a switch (1), (2), (3), (4) and a diode (5), (6), (7), (8).

4. The arrangement (10) as claimed in claim 3, characterized in that the second feed-side connection point (14) is connected to the highest potential of the battery string connecting to the negative pole of the first battery cell (11) by way of a series connection (12) that comprises two diodes (5), (6), (7), (8) arranged in a cut-off direction, the first feed-side connection point (13) is connected to the lowest potential of the battery string connecting to the positive pole of the first battery cell (11) by way of a series connection (12) that comprises two diodes (5), (6), (7), (8) arranged in a cut-off direction, and the inductor (9) is arranged between the respective two diodes (5), (6), (7), (8) that are arranged in series.

5. A battery cell arrangement (20) characterized in that the battery cell arrangement (20) comprises a battery cell (11) and an arrangement (10) as claimed in claim 1, said arrangement connected to said battery cell.

6. A battery string having a plurality of battery cell arrangements (20) as claimed in claim 5, characterized in that the arrangement (10) is structurally similar for each battery cell arrangement (20), and the battery cells (11) of the battery cell arrangement (20) are connected in series to form a string.

7. The battery string as claimed in claim 6, characterized in that the third connection points (15) of the arrangements (10) are connected to the highest potential and the fourth connection points (16) are connected to the lowest potential of the battery string, wherein electrical energy transmitted between the battery cells (11) by a balancing current is received and discharged by an inductor (9).

8. A battery string controller for controlling the switching devices (17) in a battery string as claimed in claim 6, characterized in that the battery string controller is configured to control the switching devices (17) such that the balancing current is received by the inductor (9) from the battery cell (11) that is connected in a battery cell arrangement (20) to said inductor or from at least one second battery cell (11) that is adjacent to the battery cell (11) enabling adjustment of the direction of the balancing current that is flowing through the at least second battery cell (11).

9. The battery string controller as claimed in claim 8, characterized in that the magnitude of a predeterminable balancing current is controlled by the battery string controller, wherein the number of battery cells (11) being supplied is adjusted so as to control the balancing current.

10. A method for balancing battery cells (11) of a battery string having a battery string controller as claimed in claim 8, the direction of the balancing current in each battery cell arrangement (20) is adjusted in such a manner that: a positive balancing current occurs if energy is to be drawn from the first battery cell (11) and is to be supplied to the battery string; a negative balancing current occurs if energy is to be drawn from the battery string and is to be supplied to the first battery cell (11);

11. The arrangement (10) as claimed in claim 1, wherein the battery cells (11) are part of a battery module including a plurality of series connected battery cells (11).

12. A battery string having a plurality of battery cell arrangements (20) as claimed in claim 6, wherein the arrangement (10) is structurally identical.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The invention is further explained hereinunder with reference to the attached drawings and with the aid of preferred embodiments.

[0035] In the drawings:

[0036] FIG. 1 illustrates an example of an arrangement in accordance with the invention for balancing the battery cells of a battery string;

[0037] FIG. 2 illustrates an example of a battery string in accordance with the invention having a plurality of battery cells with a respective inventive arrangement that is allocated to said battery cells and is for balancing the battery cells.

DETAILED DESCRIPTION

[0038] FIG. 1 illustrates a referred exemplary embodiment of an arrangement 10 in accordance with the invention for balancing the battery cells 11 of a battery string.

[0039] FIG. 1 also illustrates an arrangement 10 for balancing the battery cells 11 of a battery string having a plurality of series-connected battery cells 11. The arrangement 10 comprises an inductor 9 for storing electrical energy. Furthermore, the arrangement 10 comprises on the feed-side switching devices 17 so as to connect the poles of a first battery cell 11 by way of a first connection point 13 and a second connection point 14 to the inductor 9. The switching devices 17 can be controlled by a control device, not illustrated in the figure, in such a manner that electrical energy can be transmitted from at least one battery cell 11 into the inductor 9 and from the inductor 9 to at least a second battery cell 11. Furthermore, the arrangement 10 comprises a third connection point 15 and a fourth connection point 16 for charge balancing and two transfer-side switching devices 17. The inductor 9 is connected to the third connection point 15 and the fourth connection point 16 by way of the two transfer-side switching devices 17.

[0040] As a result of the switching device 17 having sufficient dielectric strength, the arrangement 10 is suitable for being connected by way of the third connection point 15 to the highest potential V.sub.smax of the battery string and the fourth connection point 16 to the lowest potential V.sub.smin of the battery string. In so doing, the inductor 9 can be connected by way of the transfer-side switching devices 17 in two polarities or flow directions 18 to the highest and the lowest potential of the battery string for charge balancing using a balancing current. A balancing current that is flowing through the inductor 9 in the illustrated flow direction 18 is described as a positive balancing current.

[0041] The switching devices 17 comprise in each case a parallel connection of a switch 1, 2, 3, 4 and a diode 5, 6, 7, 8. Moreover, so as to connect the arrangement 10 to the negative pole of the first battery cell 11, the second feed-side connection point 14 can be connected to the highest potential V.sub.smax of the battery string by way of a series connection 12 that comprises two diodes 5, 8 that are arranged in the cut-off direction, and, so as to connect the arrangement 10 to the positive pole of the first battery cell 11, the first feed-side connection point 13 can be connected to the lowest potential V.sub.smin of the battery string by way of a series connection 12 that comprises two diodes 6, 7 that are arranged in the cut-off direction. The inductor 9 is arranged between the respective two diodes 5 and 8 or 6 and 7 that are arranged in series, in other words the inductor 9 is connected by one of its connections to the series connection 12 of the diodes 5 and 8 and by the other connection to the series connection 12 of the diodes 6 and 7.

[0042] FIG. 2 illustrates four battery cell arrangements 20, wherein each battery cell 11 comprises an arrangement 10 that is connected to it. In order to assist further differentiation, the four battery cell arrangements 20 are provided with the indices i, j, k and l. The battery cells 11 of the battery cell arrangements 20 are connected in series to form a string and form a battery string, wherein each battery cell arrangement 20 is embodied in a structurally similar, in particular identical, manner.

[0043] Furthermore, the third connection points 15 of the arrangements 10 are connected to the highest potential V.sub.smax and the fourth connection points 16 are connected to the lowest potential of the battery string V.sub.smin so that electrical energy can be transmitted between the battery cells 11 by means of a balancing current that can be received and discharged by an inductor 9.

[0044] The switching devices 17 in the arrangements 10 are to be controlled in such a manner that the balancing current can be received by the inductor 9 from the battery cell 11, which is connected in a battery cell arrangement 20 to said inductor, or from at least one battery cell 11 that is adjacent to this battery cell 11 so that it is possible to adjust the direction of the balancing current that is flowing through an at least second battery cell 11.

[0045] Some of the control options for the switching devices 17 are described hereinunder. This is achieved using the example of the battery cell arrangement 20 with the index j.

[0046] In a first control position, the switches 1,j and 2,j of the battery cell arrangement 20 are closed. Subsequently, a positive balancing current in the flow direction 18 occurs in the inductor 9, said balancing current being supplied from the battery cell 11,j. Once the switches 1,j and 2,j have opened, the balancing current that is stored in the inductor 9 flows by way of the diode 5,j through the battery cells 11 i,j,k and l and the diode 6,j back to the inductor 9. A charge from the battery cell 11,j is distributed to all battery cells 11, i,j,k,l of the battery string.

[0047] In a second control option, the switches 3,j and 4,j of the battery cell arrangement 20 are closed. Subsequently, a negative balancing current in the flow direction 18 occurs in the inductor 9, said balancing current being supplied from the battery cells 11,i,j,k,l. Once the switches 3,j and 4,j have opened, the balancing current that is stored in the inductor 9 flows by way of the diode 7,j through the battery cells 11,i and the diode 8,j back to the inductor 9. A charge from all battery cells 11, i,j,k,l of the battery string is distributed to the battery cell 11,j.

[0048] In a third control option, the switches 2,j and 4,j of the battery cell arrangement 20 are closed. Subsequently, a negative balancing current in the flow direction 18 occurs in the inductor 9, said balancing current being supplied from the battery cells 11,k,l. Once the switches 3,j and 4,j have opened, the balancing current that is stored in the inductor 9 flows by way of the diode 7,j through the battery cells 11,i and the diode 8,j back to the inductor 9. A charge from all battery cells 11,k,l of the battery string is distributed to the battery cell 11,j.

[0049] In a fourth control option, the switches 1,j and 3,j of the battery cell arrangement 20 are closed. Subsequently, a positive balancing current in the flow direction 18 occurs in the inductor 9, said balancing current being supplied from the battery cell 11,i. Once the switches 1,j and 3,j have opened, the balancing current that is stored in the inductor 9 flows by way of the diode 5,j through the battery cells 11,i,j,k,l and the diode 6,j back to the inductor 9. A charge from a battery cell 11,j is distributed to all battery cells 11, i,j,k,l of the battery string.

[0050] A fifth control option is described with reference to the battery cell arrangement 20 having the index 1.

[0051] In a fifth control option, the switches 1,l and 3,l of the battery cell arrangement 20 are closed. Subsequently, a positive balancing current in the flow direction 18 occurs in the inductor 9, said balancing current being supplied from the battery cell 11,i,j,k. Once the switches 1,l and 3,l have opened, the balancing current that is stored in the inductor 9 is distributed by way of the diode 5,l through the battery cells 11,i,j,k,l and the diode 6,l back to the inductor 9. A charge from three battery cells 11,i,j,k is distributed to all battery cells 11, i,j,k,l of the battery string.

[0052] It is evident from the previously described control options that it is possible by means of appropriately controlling the switching devices 17 to adjust the number of battery cells 11 being supplied and thus the magnitude of a balancing current by means of the battery string controller. Consequently, it is possible to control both the magnitude and the direction of the balancing current. In particular, it is possible in accordance with the first control option to form a positive balancing current, wherein energy is drawn from a first battery cell 11 and supplied to the battery string, and using the second control option to form a negative balancing current, wherein energy is drawn from the battery string and supplied to a second battery cell 11.