Analog battery balancing system

Abstract

The present invention relates to a system for analog balancing of rechargeable batteries which will find application in the field of electronic engineering, particularly in all fields of industry where multicell rechargeable batteries are used. The system consists of n number of identical balancing modules (2.1, 2.2... 2.n), each with five terminals, two of them connected to the positive+ V and negative - V potential of one cell (1.1, 1.2... 1.n) of the battery, the other two are connected to the positive+ Vb and negative - Vb potential of the battery, and the fifth terminal (3.1, 3.2... 3.n) is for switching the balancing module (2.1, 2.2... 2.n) on and off to the corresponding cell of the battery via a logic signal. The balancing module (2.1, 2.2... 2.n) includes two operational amplifiers (4.1, 4.2... 4.n) and (5.1, 5.2... 5.n) as well as a controllable current consumer (6.1, 6.2... 6.n).

Description

[0001] Analog battery balancing system

[0002] Technical field

[0003] The present invention relates to a system for analogue balancing of rechargeable batteries which will find application in the field of electronic engineering and more particularly in all fields of industry, household and transport where rechargeable batteries with more than one cell connected in series are used.

[0004] Background of the invention

[0005] Rechargeable batteries with more than one cell are widely used in various applications such as electric vehicles, portable electronic devices and energy storage systems. Multi-cell batteries consist of several cells connected in series or parallel to achieve the desired voltage and capacity. Each cell in the battery has its own voltage, capacity and internal resistance characteristics. Balancing is necessary to equalize cell voltages and prevent situations where one cell is overcharged, and another is undercharged. This is essential to ensure long battery life and efficient operation, as well as to prevent damage and hazards such as overheating or explosion.

[0006] In practice, analogue and digital balancing systems are used, which are based on monitoring the individual voltage of each cell by a common control system that gives a command to balance the respective cell if necessary. The voltage levels at which decisions are made are related to the type and chemistry of the battery and need readjustment. Balancing can be passive and active. In passive balancing, excess charge from the higher charged cells is dissipated by resistors. This is a simple and inexpensive method, but is not very effective in large batteries, and, in addition, can result in energy loss, e.g. heat. Active balancing uses electronic circuitry, such as DC-DC converters or other active components, to transfer energy from the higher charged cells to the less charged cells. This method is more efficient, results in no energy loss and is preferred for large and expensive batteries.

[0007] Technical summary of the invention

[0008] It is the object of the invention to provide an analogue battery balancing system which provides the capability of active and passive balancing of all types of multi-cell batteries, the balancing of cell voltages depending only on the accuracy of the components with which the system is implemented, without the need for external control circuitry.

[0009] The problem is solved by designing an analog battery balancing system that is composed of n number of identical balancing modules, where n is the number of cells of the battery connected in series. Each of the balancing modules has five terminals, two of which are connected to the positive+ V and negative - V potential of a battery cell, the other two are connected to the positive+ Vb and negative - Vb potential of the battery cell, and the fifth terminal is for switching the balancing module on and off to the corresponding battery cell via a logic signal. Each balancing module comprises an operational amplifier connected to the positive+ Vb and negative - Vb potentials of the battery, the output of which has a voltage Vb / n and is connected to a second operational amplifier, the second input of which is provided with the voltage V of the corresponding cell of the battery. The output of the second operational amplifier is connected to a controlled current consumer which is connected in parallel to the positive+ V and negative -V potential of the corresponding battery cell.

[0010] In one embodiment of the invention, the controllable current consumer is a passive consumer for converting energy withdrawn from the cell into heat. In another embodiment of the invention, the controllable current consumer is an active current consumer that is composed of a DC / DC converter for converting the energy withdrawn from the cell and feeding it back to the battery by connecting its output to the positive+ Vb and negative -Vb potential of the battery.

[0011] The advantage of the system is that the balancing is performed by identical circuits for each cell, which are independent of each other and do not need an additional external control circuit. It is also an advantage that the balancing system can be applied to all types of batteries, with more than one cell connected in series, irrespective of the cell voltage and battery chemistry.

[0012] Description of the attached figures

[0013] The present invention is illustrated in the appended figures, where:

[0014] Figure 1 is a schematic diagram of the analog battery balancing system according to the invention;

[0015] Figure 2 is a schematic diagram of the balancing module with a passive current consumer; and

[0016] Figure 3 is a schematic diagram of the balancing module with an active current consumer.

[0017] Examples of embodiments of the invention

[0018] The designed analog battery balancing system shown in Fig. 1 is composed of n numbers of identical balancing modules 2.1, 2.2 ... 2.n, where n is the number of cells 1.1, 1.2 ... 1.n connected in series on the battery. Each of the balancing modules 2.1, 2.2 ... 2.n has five terminals, two of which are connected to the positives- V and negative - V potential of a cell 1.1, 1.2 ... l.n of the battery, the other two are connected to the positive+ Vb and the negative - Vb potential of the battery, and the fifth terminal 3.1, 3.2 ... 3.n is for switching the balancing module 2.1, 2.2 ... 2.n on and off to the respective battery cell via a logic signal. Each balancing module 2.1, 2.2 ... 2.n includes an operational amplifier 4.1, 4.2 ... 4.n connected to the positive+ Vb and negative - Vb potential of the battery. The output signal of each of the amplifiers 4.1, 4.2 ... 4.n is proportional to the voltage of all the cells of the battery divided by the number of cells connected in series - Vb / n and is connected to a second operational amplifier 5.1, 5.2 ... 5.n, to whose second input is applied the voltage V of the corresponding cell of the battery. The second amplifiers 5.1, 5.2 ...

[0019] 5.n compare the voltage at the outputs of the amplifiers 4.1, 4.2 ... 4.n to the voltage of the cell to which they are connected. The output of each second operational amplifier 5.1, 5.2 ... 5.n is connected to a controllable current consumer 6.1, 6.2 ...

[0020] 6.n which is connected in parallel to the positive+ V and negative - V potential of the corresponding cell 1.1, 1.2 ... l.n ofthe battery.

[0021] If the voltage of any cell, for example 1.1, is higher than the voltage of the whole battery divided by the number of cells Vb / n, then the current consumer 6.1, which is connected in parallel to cell 1.1 , is triggered and takes part of its charging current. The greater the voltage of cell 1.1 relative to the averaged battery voltage for cell Vb / n, the greater the current through the corresponding current consumer 6.1. When the voltage of cell 1.1 tends to the average battery voltage Vb / n, the current through current consumer 6.1 tends to zero i.e. cell 1.1 is balanced and its voltage is equal to that of the other cells. If the voltage of cell 1.1 is lower than the average voltage Vb / n of the battery, the corresponding current consumer 6.1 is switched off.

[0022] In one embodiment of the invention shown in FIG. 2, the controlled current consumer 6.1, 6.2 ... 6.n is a passive consumer 7.1, 7.2 ... 7.n, such as a resistor or other resistive element, for converting the energy removed from the cell into heat. In another embodiment, shown in Fig. 3, the controlled current consumer 6.1 , 6.2 ... 6.n is an active consumer 8.1, 8.2 ... 8.n, which is composed of a DC / DC converter for converting the energy withdrawn from the cell and feeding it back with minimal losses to the battery by connecting its output to the positives- Vb and the negative - Vb potential of the batteiy .

[0023] With the analog balancing system created, cell voltage equalization is provided by comparing the average battery cell voltage TO the voltage of the specific cell and subtracting from the cell's charging current so that its voltage tends to the average battery cell voltage. The balancing is performed by identical balancing m odules for each cell, which are independent of each other and do not need additional external control circuitry to check the voltage of each individual cell and turn the balancing of the respective cell on and / or off. The common control circuit only needs to decide whether to enable or disable balancing, and can be used to connect or disconnect all balancing modules simultaneously, depending on the mode and state of the battery - charge, discharge, charge current magnitude, storage, etc. The balancing of cell voltages depends only on the accuracy of the components with which the balancing modules are implemented. The balancing system can be applied to all types of batteries, as it does not depend on the cell voltage, based on the chemical composition, and on the instantaneous battery voltage - for example if there is temperature compensation, and does not need to be readjusted when changing the voltage or battery type if the number of cells connected in series is maintained.

Claims

PATENT CLAIMS1. An analog batery balancing system, characterized in that it is composed of n numbers of identical balancing modules (2.1, 2.2 ... 2.n ), where n is the number of cells (1.1, 1.2 ... l.n) connected in series on the battery, where each balancing module (2.1, 2.2 ... 2.n) has five terminals, two of which are connected to the positives- V and negative - V potential of one cell (1.1, 1.2 ... l.n) of the battery, the other two are connected to the positive+ Vb and negative - Vb potential of the whole battery, and the fifth terminal (3.1, 3.2 ...

3. n) is for switching the balancing module (2.1, 2.2 ... 2.n) to the corresponding battery cell via a logic signal, where each balancing module (2.1, 2.2 ... 2.n) includes an operational amplifier (4.1, 4.2 ... 4.n) connected to the positives- Vb and negative - Vb potential of the battery, whose output has a voltage Vb / n and is connected to a second operational amplifier (5.1, 5.2 ... 5.n) whose second input is supplied with the voltage V of the corresponding cell ( 1.1 , 1.2 ... 1.n) of the battery, the output of the second operational amplifier (5.1, 5.2 ... 5.n) is connected to a controlled current consumer (6.1, 6.2 ... 6.n) which is connected in parallel to the positive* V and negative -V potential of the respective cell (1.1, 1.2 ... l.n) of the battery.

2. An analog batery balancing system according to claim 1, characterized in that the controlled current consumer (6.1, 6.2 ... 6.n) is a passive consumer (7.1, 7.2 ... 7.n) for converting the energy withdrawn from the cell into heat.

3. Analog batery balancing system according to claim 1, characterized in that the controllable current consumer (6.1, 6.2 ... 6.n) is an active consumer (8.1, 8.2 ... 8.n), which is composed of a DC / DC converter for converting the energy withdrawn from the cell and feeding it back to the battery by connecting its output to the positive* Vb and negative - Vb potential of the battery.

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