EP2700141A1

EP2700141A1 - A system and method for balancing energy storage devices

Info

Publication number: EP2700141A1
Application number: EP12714333.7A
Authority: EP
Inventors: Rudolf Vidael; Eric Verhaeven
Original assignee: 4Esys
Current assignee: 4Esys
Priority date: 2011-04-19
Filing date: 2012-04-18
Publication date: 2014-02-26
Also published as: WO2012143396A1

Abstract

The present invention is directed to a method for balancing a series connection of energy storage devices comprising: - measuring, calculating or learning an unbalance parameter in a series connection of energy storage devices, - determining a type, and/or a status, and/or a value and/or a deviation of the unbalance parameter, and - restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices. The present invention is further directed to a system for balancing a series connection of energy storage devices comprising: - a means for determining a measured, calculated or learned unbalance parameter in a series connection of energy storage devices, - a means for determining a type, and/or a status, and/or a value and/or a deviation of the unbalance parameter, and - a means for restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices. The invention is also directed to the use of the above system or method for balancing a series connection of electric double-layer capacitors, lithium capacitors, electrochemical battery devices and battery packs, and lithium battery devices like lithium-polymer and lithium-ion battery devices, and blended combinations thereof.

Description

A SYSTEM AND METHOD FOR BALANCING ENERGY STORAGE DEVICES.

FIELD OF THE INVENTION The present invention relates to a method and system for balancing energy storage devices, more specifically a series connection of energy storage devices. Further, it relates to an assembly comprising a series connection of energy storage devices and such balancing system. Additionally, the invention relates to the use of such system or method for balancing a series connection of electric double-layer capacitors, lithium capacitors, electrochemical battery devices and battery packs like lead-acid or NiMH, and lithium battery devices like lithium-polymer and lithium-ion battery devices, and blended combinations thereof.

BACKGROUND OF THE INVENTION

Recently, a lot of effort has been put in enhancing the use of energy storage media, in particular large numbers of energy storage devices in series connection. Such series connection is for example used in hybrid drive trains for buses, waste collection vehicles, fork lift trucks and electric cars.

Usually, a series connection of energy storage devices for medium and high voltage applications comprises a large number of energy storage devices. For example, since the maximum voltage of an energy storage device is limited to for example about 2.5V to 3.0V in case of a double layer capacitor, a number in the range of 20 to 25 energy storage devices need to be serially connected to form an energy storage device stack delivering a voltage of for example 60V.

A general problem of series connections of energy storing devices is that varying characteristics of each individual energy storage device such as for example differences in self-discharge, capacitance and internal resistance or differences due to environmental conditions such as temperature, causes energy storage devices to carry unequal voltages, resulting into a stack in a so-called unbalanced condition. The total stack capacity and current is limited by the single energy storage device operating at its voltage limit (minimum or maximum), resulting in poorly utilized energy storage devices, unless charge equalization is performed. Considering the above, it is an object of the present invention to provide a system and method for balancing a series connection of energy storage devices with an improved efficiency and less time consuming balancing, even upon extending the series connection to large numbers of energy storage devices or heavy-duty applications requiring repetitive alternating energy delivery and storage in rapid succession.

Further, it is an object of the present invention to provide a system and method with controlled adaption management (CAM) which allows as much as possible compensation, even at individual energy storage device level, from charge unbalance originating from parasitic effects, internal resistance deviations, capacity mismatch, aging effects and temperature effects.

Further, it is an object of the present invention to provide a system for balancing a series connection of energy storage devices with a dedicated structure while allowing automatically controlled balancing which can be activated and deactivated at any time.

Another object of the present invention is to provide a low-cost system and method for balancing a series connection of energy storage devices, which is easily scalable to large numbers of energy storage devices.

A further object of the present invention is to provide a system and method for balancing a series connection of energy storage devices, which is easily scalable to different types of energy storage devices.

The invention meets the above objectives by measuring, calculating or learning an unbalance parameter in a series connection of energy storage devices, determining a type, and/or a status, and/or a value, and/or a deviation of the unbalance parameter, and restricting, generating or adapting an energy flow in the series connection of energy storage devices. SUMMARY OF THE INVENTION

The present invention is directed to a method for balancing a series connection of energy storage devices comprising:

- measuring, calculating or learning an unbalance parameter in a series connection of energy storage devices,

- determining a type, and/or a status, and/or a value and/or a deviation of the unbalance parameter, and

- restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices.

The present invention is further directed to a system for balancing a series connection of energy storage devices comprising:

- a means for determining a measured, calculated or learned unbalance parameter in a series connection of energy storage devices,

- a means for determining a type, and/or a status, and/or a value and/or a deviation of the unbalance parameter, and

- a means for restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices.

The invention is also directed to the use of the above system or method for balancing a series connection of electric double-layer capacitors, lithium capacitors, electrochemical battery devices and battery packs, and lithium battery devices like lithium-polymer and lithium-ion battery devices, and blended combinations thereof. BRIEF DESCRIPTION OF THE DRAWINGS:

FIG 2, 3a and 3b illustrate prior art systems or methods.

FIG 1 and 4 to 13 illustrate several embodiments of a system or method in accordance with the present invention.

DESCRIPTION OF THE INVENTION As a first embodiment of the present invention, a method for balancing a series connection of energy storage devices is provided comprising:

- restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices. In a further embodiment, the method may comprise the step of determining the assembly level to which the unbalance parameter relates. In the context of the present invention, assembly levels are understood as considerable topology levels in a series connection of energy storage devices, such as individual energy storage device level, substring of energy storage devices level, multi-substring of energy storage devices level, section level, total series connection level, system level or application level or a combination thereof.

Consequently, the unbalance parameter may be measured, calculated, or learned, as well as its type, status, value or deviation determined, on individual energy storage device level, substring of energy storage devices level, multi-substring of energy storage devices level, on section level, on total series connection level, on system level or on application level or a combination thereof.

The energy flow(s) may be restricted, generated or adapted on individual energy storage device level, substring of energy storage devices level, multi-substring of energy storage devices level, on section level, on total series connection level, on system level or on application level or a combination thereof.

Restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices includes restricting, generating or adapting any energy flow or charge transfer in, to, or over the series connection of energy storage devices at any assembly level, or any current flow or charge transfer in, over, to an intermediate storage element (capacitor, inductor, etc), a (precharge) contactor, a switch, an electric connection, a controller, a fuse or a peripheral element in an assembly including the series connection.

In the context of the present invention, said unbalance parameter is understood as any parameter of which the status, value, or deviation differs from the status, value, or deviation of said parameter corresponding to the majority of the energy storage devices.

In an embodiment in accordance with the present invention, said measuring may be performed by capturing voltage or current.

In another embodiment in accordance with the present invention, said calculating may be performed by mathematical operations and filtering techniques. In another embodiment in accordance with the present invention, said learning may be performed by capturing the history of the status, the value or the deviation of an unbalance parameter, and predicting said status, value or deviation.

Further, in accordance with the present invention a system for balancing a series connection of energy storage devices is provided comprising:

In an embodiment in accordance with the present invention, the means for determining a measured, calculated or learned unbalance parameter in a series connection of energy storage devices, the means for determining a type, and/or a status, and/or a value and/or a deviation of the unbalance parameter, and the means for restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices may comprise a switching means receiving a control signal wherein said control signal has attribute settings adapted as a function of said unbalance parameter or set of said unbalance parameters.

In a further embodiment, the method may comprise the step of determining the assembly level to which the unbalance parameter relates. In the context of the present invention, assembly levels are understood as considerable topology levels in a series connection of energy storage devices, such as individual energy storage device level, substring of energy storage devices level, multi-substring of energy storage devices level, section level, total series connection level, system level or application level or a combination thereof.

Determining the assembly level or condition related to the unbalance parameter can be done by identification of substring location. Substrings are preferably connected through a backplane configuration using connectors of a quick-disconnect or slide-in type for modularity. The lock-unlock fastening of these substring connectors is preferably remote. By entering and connecting one or more substrings into each slot of the backplane connector of the assembly, each substring (for example part of a module containing two or more substrings) automatically obtains a unique assembly identification number applied by the software (Controller Area Network (CAN) Id, Serial Id). This is established by reading the so called Id pins at the backplane connector (0 to 5² - 1 possible Id's) which is established by simply returning internal reference voltages or grounds to the controller of the substring. This offers flexibility to randomly insert the substring or module in the system and provides the benefits for the manufacturer to produce fully identical and interchangeable RCM modules. Preferably an automatic assembly configuration system and method identifies the number of required substrings for the provided application. Depending of the applications, an assembly consists of several substrings configured into one or more modules. By applying the available information (number of CAN Id's, Current Loop Status, available temperature sensors) the application software, located in the main assembly controller, automatically determines the required or available substrings or modules that makes the assembly complete. This results into automatic adaptation and matching of the assembly performances and diagnostics. Benefit for the manufacturer is that no software modification is required per assembly configuration. Additionally, an embodiment in accordance with the present invention may be based on intermediate energy storage regulation as explained below, because this approach offers the best sizing possibilities, interference characteristics and cost- effectiveness with commercially readily available low-cost components for circuit design and regulation of the balancing system.

In an embodiment of the present invention and as illustrated in FIG 1 , a system for balancing a series connection of energy storage devices is provided comprising:

a) an intermediate storage element (b) coupled between a pair of non-adjacent sections (d) of one or a number of adjacent energy storage devices (a1 , a2, a3) of a series connection of energy storage devices, said sections each having a more positive terminal (A) at one end and a more negative terminal (B) at its other end;

b) and a switching means (c) receiving a control signal for switching sequentially between coupling terminals (A) to each other via said intermediate storage element and coupling terminals (B) to each other via said intermediate storage element; said control signal has attribute settings adapted as a function of an unbalance parameter or set of parameters

Preferably, these sections contain a nominally equal amount of energy storage capacity. In the context of the present invention, terminal (A) and terminal (B) are to be understood as respectively the more positive terminal at one end and the more negative terminal at the other end of each section of one or a number of adjacent energy storage devices. To illustrate the advantages of the above embodiment, a prior art system is shown in FIG 2, FIG 3a and FIG 3b as described in US2004/0246635, wherein switch series S1 and S2 are switched alternatingly, placing the capacitors (37) and (38) subsequently in parallel to (B1 ) and (B2), and (B2) and (B3) respectively. A major disadvantage of this method is its inability to efficiently redistribute charge between non-adjacent energy storage devices in a series connection. All such charge redistribution requires multiple, sequential transfer operations making the process slow and lossy.

However, by using an intermediate storage element that is coupled between a pair of non-adjacent sections and a switching means switching sequentially between coupling terminals (A) to each other via said intermediate storage element and coupling terminals (B) to each other via said intermediate storage element, only a limited number of components are required per energy storage device, while balancing groups of energy storage devices, or individual energy storage devices, is possible over the complete series connection or part of it. The switching means switches alternating, placing the intermediate storage element subsequently in parallel to the series connection of (a1 ) and (a2), and to the series connection of (a2) and (a3). Therefore, in steady state, V(a1 )+V(a2) = V(a2)+V(a3) and thus V(a1 ) = V(a3). During the iterative process of charge equalization, the voltage V(a2) of storage device (a2) remains essentially unaffected, while the voltage V(a1 ) of storage device (a1 ) becomes equal to the voltage V(a3) of storage device (a3). Another advantage is that such system performs with improved efficiency and requires less time to achieve balancing, even upon extending the series connection to large numbers of energy storage devices or heavy-duty applications requiring repeated energy delivery and storage in rapid succession. As a balancing system and method according to the invention is able to convey electrical energy between non-adjacent energy storage devices or groups of non- adjacent energy storage devices, and as the speed of energy charge transfer is proportional to the electric potential difference between those energy storage devices or groups, the use of such system results in a generally faster charge redistribution in the series connection of energy storage devices than can be attained with systems allowing only charge to be transferred between adjacent energy storage devices or groups of energy storage devices. Additionally, by using a control signal having attribute settings adapted as a function of the unbalance parameter or set of parameters, switching means may be more efficiently controlled in order to allow dedicated compensation of charge unbalance originating from parasitic effects, internal resistance deviations, capacity mismatch, aging effects and temperature effects.

Hence, the performances, efficiencies, and lifetime of energy storage devices may be improved if such compensations or adaptations can be made online on deviations from external or internal origin.

In the context of the present invention, a control signal attribute setting is understood as any type of attribute setting pertaining to controlling switching means, such as for example interrupt, on-time, off-time, frequency, phase, amplitude, waveform, skewness, duty cycle, or slew rate. They may be continuous or discrete, and may be applied to all switching means or selectively to individual or a selection of switching means.

In the context of the present invention, the unbalance parameter is understood as any type of parameter measurable in the energy storage system and usable as a basis for adapting a control signal attribute setting (see further below).

The balancing system may comprise a measurement means for measuring the unbalance parameter or set of parameters, and may comprise additionally a processor for processing the measured unbalance parameters to obtain calculated or learned unbalance parameters.

Further, it is also an advantage that a system in accordance with the present invention allows a dedicated structure while automatically controlled balancing which can be activated and deactivated at any time is still possible.

Another advantage of such system is that manufacturing cost is minimal with commercially readily available low-cost components for circuit design while easily scalable to large numbers of energy storage devices and different types of energy storage devices. In the context of the present invention, an energy storage device (also called "cell" in the context of the present invention) may be any device adapted to store electrical charge, for example electric double-layer capacitors (EDLCs or so-called ultracapacitors or supercaps), lead acid or NiMH batteries, lithium capacitors, electrochemical battery devices and battery packs, and lithium battery devices like lithium-polymer and lithium-ion battery devices, and blended combinations thereof.

The energy storage device may be not only an individual or single cell, but also a unit (called multicell) comprising a specific combination of cells connected in parallel and/or in series.

Such multicell may combine cells with the same chemistry, e.g. two lithium cells connected in parallel to increase capacity, or may combine cells with different chemistry (also referred to as blended combination), e.g. a lead-acid cell connected in parallel with an ultracapacitor cell, a lithium cell connected in parallel with two series-connected ultracapacitors, or an ultracapacitor cell connected in parallel with two series-connected NiMH cells. As practical example, a 24V battery for forklifts comprises one string composed of 12 multicells in series connection, where each multicell consists of a lead acid cell in parallel with an ultracapacitor.

In an embodiment in accordance with the present invention, said non-adjacent sections of a one or a number of adjacent energy storage devices may comprise one or an equal number of nominally equally sized energy storage devices.

In the context of the present invention nominally equally sized means that an acceptable deviation between the characteristics of the energy storage devices may be allowed.

In another embodiment according to the present invention, a system for balancing a series connection of energy storage devices may be provided comprising a plurality of a pair of non-adjacent sections of one or a number of adjacent energy storage devices and a plurality of respective intermediate storage elements.

In a further embodiment in accordance with the present invention and as illustrated in FIG 4, the plurality of respective intermediate storage elements may constitute one or a plurality of serial strings of intermediate storage elements (e). In particular by assembling such strings using bus systems, the manufacturing of the strings and consequently of the complete system may be significantly simplified. In a particular embodiment in accordance with the invention, two or more pairs of non-adjacent sections of a one or a number of adjacent energy storage devices may comprise overlapping energy storage devices.

In another particular embodiment of the present invention, the switching means may concurrently couple all terminals (A) and concurrently couple all terminals (B) with a number of intermediate storage elements equal to the number of respective coupled terminals minus one.

In the context of the present invention, the intermediate storage element may be any electrical component adapted to intermediately store electrical charge between being coupled to terminals (A) and being coupled to terminals (B), for example capacitors, inductors and transformers.

Using charge shuttling with energy storage elements such as capacitors has the advantage that balancing can be executed during all possible operation modes of the series connecting of energy storage devices, i.e. not only while charging but also while discharging or in idle mode operation.

In a preferred embodiment in accordance with the present invention, the intermediate storage element may be a capacitor. By using a commercially available and technically mature capacitor and switch technology the efficiency and reliability of the balancing system may be highly improved due to efficient charge transportation. The capacitor used as intermediate storage element may have any capacitance, but preferably between 1 nanofarad and 1 millifarad, more preferably between 10 nanofarad and 100 microfarad, and most preferably around 10 microfarad. The applied capacitors may be low-cost components defined for low voltage, usually in the order of maximum energy storage device voltages.

The switching means may comprise any electrical component adapted to obtain sequential coupling of the intermediate storage element to terminals (A) and to terminals (B).

The switching means may comprise a Field Effect Transistor (FET) to couple each energy storage device via terminal (A) to an intermediate storage element and a FET to couple each energy storage device via terminal (B) to an intermediate storage element.

In an alternative embodiment the above FETs may be replaced by a combination of a diode and a FET. In a particular embodiment according to the present invention the switching means may comprise an alternating configuration of p-channel Metal Oxide Silicon Field Effect Transistors (MOSFETs) and n-channel MOSFETs.

In such alternating configuration of p-channel MOSFETs and n-channel MOSFETs, the positive and negative electrodes of the intermediate storage element are connected to the drain electrodes of two p-channel MOSFETs, their source electrodes being connected to the terminals (A) of the respective non-adjacent sections of one or a group of energy storage devices, and the positive and negative electrodes of the intermediate storage element are connected to the drain electrodes of two n-channel MOSFETs, their source electrodes being connected to the terminals (B) of the respective sections. The electric potentials of the terminals (A) are generally higher than the potentials of the respective terminals (B). The gate electrodes of the MOSFETs are connected using a resistance to their respective source terminals (A) and capacitively coupled to a control signal source. The gate terminal itself may function as a control signal source for other MOSFETs as well.

In an alternative alternating configuration of p-channel MOSFETs and n-channel MOSFETs, the positive and negative electrodes of the intermediate storage element are connected to the source electrodes of two n-channel MOSFETs, their drain electrodes being connected to the terminals (A) of the respective non-adjacent sections of one or a group of energy storage devices, and the positive and negative electrodes of the intermediate storage element are connected to the source electrodes of two p-channel MOSFETs, their drain electrodes being connected to the terminals (B) of the respective sections. The electric potentials of the terminals (A) are generally higher than the potentials of the respective terminals (B). The gate electrodes of the MOSFETs are connected using a resistance to their respective source terminals and are capacitively coupled to a control signal source. The gate terminal itself may function as a control signal source for other MOSFETs as well.

Other alternative alternating configurations of p-channel MOSFETs and n-channel MOSFETs can be derived from a combination of either of the two embodiments described above and may result in a reduced component count, by trivial omission of extraneous FETs.

The switching means may also comprise a multiplexer system.

Individual energy storage devices and/or groups of energy storage devices may be brought towards a desired charge or energy levels by introducing additional or external energy source(s) allowing balancing over a larger dynamic range of the individual energy storage device voltages.

According to the present invention, said series connection of energy storage devices (also called string of energy storage devices), fully or partially balanced by methods according to the invention, may be organized as a plurality of substrings and/or as a plurality of modules including one or more substrings. Between these substrings of energy storage devices or between these modules an intersubstring balancing system may be implemented.

Such intersubstring balancing system may comprise a capacitor. As illustrated in FIG 5a and 5b, capacitive intersubstring balancing may be performed by selecting from each string a section of one or more energy-storage devices, these sections being non-adjacent, and by using a capacitor (Cbal) coupled between said non-adjacent sections and a switching means alternating between closed switches SAI and SA2 and closed switches SBI and SB2- This way of intersubstring balancing may perform with improved efficiency and requires less time to achieve balancing, even upon extending the series connection to large numbers of energy storage devices or heavy-duty applications requiring repeated energy delivery and storage in rapid succession. Alternatively and as illustrated in FIG 6, such intersubstring balancing system may comprise an inductor providing theoretically lossless charge transfer between the substrings of energy storage devices.

In order to expand the effect of the intersubstring balancing system, non-adjacent sections of more than three energy storage devices of each substring may be balanced to each other.

As shown in FIG 7, also a combination of a capacitor (Cbal) and a controllable inductive coupling may be used. This way it would be possible to charge the capacitor using a substring with a high voltage and discharge the capacitor to a substring with a low voltage, which may be very interesting upon seeking balancing complete substrings to each other. Another advantage of this intersubstring balancing system may be that less 'local' effects can occur within an individual substring, and that fast active balancing throughout a plurality of substrings or a plurality of modules may be achieved.

Additionally, the present invention provides an assembly comprising a series connection of energy storage devices and balancing system in accordance with the embodiments as described above. Further, in an embodiment in accordance with the present invention, a method for balancing a series connecting of energy storage devices may be provided wherein measuring, calculating or learning an unbalance parameter in a series connection of energy storage devices, determining a type, a status, and a value or a deviation of the unbalance parameter, and restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices may comprise controlling a switching means by means of a control signal having attribute settings wherein said attribute settings are adapted as a function of said unbalance parameter or a set of said unbalance parameters..

Further, in an embodiment according to the present invention, also a method for balancing a series connection of energy storage devices is provided, comprising the steps of, by reference to FIG 1 :

a. providing a series connection of energy storage devices,

b. selecting from said series connection a pair of non-adjacent sections (d) of one or a number of adjacent energy storage devices (a1 , a2, a3), said sections to be balanced to each other and each having a more positive terminal (A) at one end and a more negative terminal (B) at its other end, c. controlling a switching means by means of a control signal having attribute settings such that said switching means switches sequentially between coupling the terminals A to each other via said intermediate storage elements and coupling the terminals B to each other via said intermediate storage elements; said attribute settings being adapted as a function of an unbalance parameter or a set of parameters.

Preferably, these sections contain a nominally equal amount of energy storage capacity. For example, one seeks to balance energy storage device (a1 ) with energy storage device (a3):

- first select a first section consisting of energy storage device (a1 ) and a second section consisting of energy storage device (a3), both sections being separated by energy storage device (a2).

- couple terminal (A) of energy storage device (a1 ) to terminal (A) of energy storage device (a3) via an intermediate storage element, which results in that the intermediate storage element is coupled in parallel over energy storage device (a1 ) and energy storage device (a2)

- decouple terminals (A) and couple terminal (B) of energy storage device (a1 ) to terminal (B) of energy storage device (a3) via the intermediate storage element, which results in that the intermediate storage element is then coupled in parallel over energy storage device (a2) and energy storage device (a3).

For example, by reference to FIG 4, one seeks to balance energy storage device (a1 ) with energy storage device (a4):

- first select a first section consisting of energy storage device (a1 ) and a second section consisting of energy storage device (a4), both sections are separated by energy storage devices (a2) and (a3).

- couple terminal (A) of energy storage device (a1 ) to terminal (A) of energy storage device (a4) via an intermediate storage element, which results in that the intermediate storage element is coupled in parallel over energy storage device (a1 ), (a2), and (a3)

- decouple terminals (A) and couple terminal (B) of energy storage device (a1 ) to terminal (B) of energy storage device (a4) via the intermediate storage element, which results in that the intermediate storage element is then coupled in parallel over energy storage device (a2), (a3), and (a4).

For example, one seeks to balance a group of energy storage devices (a1 ) and (a2) with a group of energy storage devices (a4) and (a5):

- first select a first section consisting of energy storage devices (a1 ) and (a2), and a second section consisting of energy storage devices (a4) and (a5), both sections are separated by energy storage device (a3).

- couple terminal (A) of the section consisting of energy storage devices (a1 ) and (a2) to terminal (A) of the section consisting of energy storage devices (a4) and (a5) via an intermediate storage element, which results in that the intermediate storage element is coupled in parallel over energy storage device (a1 ), (a2), and (a3).

- decouple terminals (A) and couple terminal (B) of the section consisting of energy storage devices (a1 ) and (a2) to terminal (B) of the section consisting of energy storage devices(a4) and (a5) via the intermediate storage element, which results in that the intermediate storage element is then coupled in parallel over energy storage device (a3), (a4), and (a5).

A method in accordance with the embodiments described above may be used for balancing a series connection of electric double-layer capacitors (EDLCs or so-called ultracapacitors or supercaps), lead acid or NiMH batteries, lithium capacitors, electrochemical battery devices and battery packs, and lithium battery devices like lithium-polymer and lithium-ion battery devices, and blended combinations thereof. A first advantage of such method is that balancing becomes less time consuming due to improved efficiency of charge transfer through the series section, particularly upon extending the series connection to large numbers of energy storage devices.

Further, such method only requires a dedicated balancing system structure, while automatically controlled balancing which can be activated and deactivated at any time is still possible.

Another advantage of a method in accordance with the present invention is that large numbers of energy storage devices in a serial connection may be balanced concurrently.

A system in accordance with the present invention with a plurality of substrings of intermediate energy storage devices and corresponding switching means and intermediate energy storage elements may use either one single or multiple independent control signals for carefully controlling and achieving efficient energy transfer without unwanted effects.

Also, a system in accordance with the present invention with a plurality of strings of intermediate energy storage elements and corresponding switching means may use either one single or multiple independent control signals for carefully controlling and achieving efficient energy transfer without unwanted effects.

The control signal may comprise one or a combination of different types of attribute settings, or may comprise a number of sub-signals each comprising one or a combination of different types of attribute signals. Adaptive control of the attribute settings may be continuous or discrete, and may be applied synchronously or asynchronously, to all switching means or selectively to individual or a selection of switching means. As an example, switching of the switching means may be controlled in synchronism for all switching means on system level, and/or while the on- or off-time may be controlled per individual switching means.

Useful measured unbalance parameters may be for example:

Voltage (V) (e.g. Vtotalstring the total additive voltage of a modular string or substring of serial connections of energy storage devices; Vcelldifferential: the voltage difference between energy storage devices within a string or substring; Vslope: structural increment or decrement of energy storage device voltages throughout a serial connection of devices amounting to a deviation from the horizontal)

Temperature (°C/ F),

Ohmic internal resistance (Ohm),

Current (A)

Charge (C),

Diffusion resistance (Ohm)

Charge transfer polarization of the positive electrode (F)

Charge transfer polarization of the negative electrode (F)

Capacity between positive electrode and electrolyte (F)

Capacity between negative electrode and electrolyte (F)

Polarization resistance (Ohm)

State Of Charge (%)

State Of Health (%)

State Of Function (%)

Activation polarisation (F)

Concentration polarization (F)

Capacity (Ah or F)

Leakage Current (imA) Such unbalance parameter may be measured on individual energy storage device level, on section level, on total series connection level, on system level, on application level etc. In accordance with the present invention, the unbalance parameter may be measured, but may also be achieved by calculating it from a measured unbalance parameter, or learned by comparing measured or calculated unbalance parameters with specific thresholds and stored values (also-called tracking). Such calculated unbalance parameters may be for example a maximum, a minimum, an average, a delta, a Root Mean Square, a deviation, etc based on measured unbalance parameters.

As an example of using a measured unbalance parameter, the frequency of the control signal can be adapted to the total voltage parameter Vtotal of the serial connected cells. This allows maximizing charge transfer to maximum charging levels of the cells such that overvoltage charging of weaker cells will be minimized and even prevented.

As an example of using a calculated unbalance parameter: The frequency of the control signal can be adapted to the parameter (Vhigh-Vlow). Higher frequency of the control signal results in faster charge transfer and therefore better balancing of charge between cells. Therefore the rate (Vhigh-Vlow) change and corresponding balance status can be adapted and optimized. As an example of using a learned unbalance parameter: The differential voltage (Vhigh-Vlow) for a number of cells can be tracked versus the total voltage Vtotal in charging or discharging operation. The frequency of the control signal can be adapted such that the differential voltage is minimal when Vtotal is reaching maximum with the cells fully charged.

In a particular embodiment, the control signal for the individual switching means may have attribute settings adapted such that a selection of switching means is made inactive. By selectively rendering specific selective switches of the switching means inactive or active, the topology of the active circuit of the balancing circuit may be changed between subsequent balancing cycles or even during a balancing cycle, resulting in even more efficient balancing of the energy storage devices.

As an illustration, FIG 8a depicts a series connection of energy storage devices and a single string of intermediate storage elements controlled by the S1 /S2 commands in FIG 9, when gate control signals U1 = S1 and U2 = S2. This configuration exchanges charge between the energy storage devices B1 and B3 and B5. By inhibiting gate control pulses U1 and U2, as shown in FIG 8b, a circuit exchanging charge solely between B1 and B5 is obtained. In fact, by doing so, the topology of the system is changed. Obviously, depending on the charging state of B1 and B5, the charge transfer speed between B1 and B5 may be increased.

In a method in accordance with the present invention a plurality of pairs of non- adjacent sections of one or a number of adjacent energy storage devices may be selected and the terminals of each pair may be coupled via respective intermediate storage elements, said respective intermediate storage elements constituting one or multiple serial strings of intermediate storage elements.

In a further method in accordance with the present invention the step of selecting may be performed such that two or more pairs comprise overlapping energy storage devices.

A preferred method for balancing a series connection of energy storage devices according to the present invention is provided, wherein each non-adjacent section of one or a number of adjacent energy storage devices may be selected such that it consists of one energy storage device, wherein said respective intermediate storage elements may constitute three serial strings of intermediate storage elements, wherein pairs of said sections corresponding to the first and second of said serial strings may not comprise overlapping storage devices, and wherein at least one pair corresponding to the third of said serial strings may comprise a storage device overlapping with a storage device of a pair corresponding to the first string, and a storage device overlapping with a storage device of a pair corresponding to the second string. By selecting a first energy storage device which belongs to a pair of sections balanced by an intermediate storage element of the first serial string, and a second energy storage device which belongs to a pair of sections balanced by an intermediate storage element of the second serial strings, and then sequentially coupling terminals (A) and terminals (B) of these energy storage devices via an intermediate storage element belonging to a third serial string, the energy storage devices balanced to each other via the first serial string are balanced to the energy storage devices balanced to each other via the third serial string.

A balancing system in accordance with the present invention and adapted to perform the above method is illustrated schematically in FIG 9, wherein four electric energy storage elements (a1 , a2, a3, a4) are charge equalized using three charge redistribution stages. These three stages are controlled, respectively by signals (R1 ..2), (S1 ..2) and (T1 ..2), which do not need to have a relationship between each other and can be configured independently to ensure efficient energy transfer and balancing without unwanted effects. The stages based on the R, S and T signals yield V(a2) = V(a4), V(a1 ) = V(a3) and V(a1 ) = V(a4) respectively, and, hence, V(a1 ) = V(a2) = V(a3) = V(a4). Such system is designed for balancing a series connection of energy storage devices at the individual energy storage device level, wherein each section consists of one energy storage device, wherein said respective intermediate storage elements constitute three serial strings, wherein pairs corresponding to the first and second of said serial strings do not comprise overlapping storage devices, and wherein at least one pair corresponding to the third of said serial strings of intermediate storage elements comprise a storage device overlapping with a storage device of a pair corresponding to the first string, and a storage device overlapping with a storage device of a pair corresponding to the second string.

In such system and method, controlled variables may include for instance the switching frequency of the gate turn-off and turn-on commands (R1 /R2, S1 /S2 and T1 /T2) of the three serial strings, in particular to control the speed of the charge redistribution. Also a phase shift between the signals of the three strings may be a useful controlled variable, in particular to mitigate the effects of charge injection through the MOSFET gates, in case MOSFETs are used.

In a further embodiment in accordance with the present invention, the method may comprise an additional step of intersubstring balancing between a plurality of substrings or between a plurality of modules comprising one or more substrings of energy storage devices.

Below an example of a method and system in accordance with the present invention is provided. It should be well understood that the present invention is not limited to the parameters and measuring principles detailed in this example, but that these are included as specific elements to illustrate specific working principles of the present invention.

A/ USED UNBALANCE PARAMETERS AND CONTROL SIGNALS a) The table below shows specific defined measured unbalance parameters.

MEASURED ENTITY PARAMETER (unit)

Actual Cell Voltage (V)

Substring Temperature (°C/ F)

Multisubstring Ohmic internal resistance (Ohm)

String Current (A)

Multistring Charge (C)

Diffusion resistance (Ohm)

Charge transfer polarization of the positive electrode (F)

Charge transfer polarization of the negative electrode (F)

Capacity between positive electrode and electrolyte (F)

Capacity between negative electrode and electrolyte (F)

Polarization resistance (Ohm)

State Of Charge (%)

State Of Health (%)

State Of Function (%)

Activation polarisation (F) Concentration polarization (F)

Capacity (Ah or F)

Leakage Current (imA)

Examples of measured unbalance parameters are:

Measured_Actual_Cell_Voltage: the measured voltage over a cell.

Measured_Actual_Substring_Voltage, the measured voltage over a substring: The frequency of the control signal (Control_Output_PWM_Frequency) adapted to the Measured_Actual_Substring_Voltage of in the series connected cells. b) The table below shows specific defined calculated unbalance parameters:

CALCULATED ENTITY PARAMETER (unit)

Maximum Cell Voltage (V)

Minimum Substring Temperature (°C/ F)

Average Multisubstring Ohmic internal resistance (Ohm)

Filtered String Current (A)

Delta Multistring Charge (C)

Total Diffusion resistance (Ohm)

Root Mean Square Charge transfer polarization of the positive electrode (F)

Deviation Charge transfer polarization of negative electrode (F)

Balanced Capacity between positive electrode and electrolyte (F)

Capacity between negative electrode and electrolyte (F)

Polarization resistance (Ohm)

State Of Charge (%)

State Of Health (%)

State Of Function (%)

Activation polarisation (F)

Concentration polarization (F)

Capacity (Ah or F) Leakage Current (imA)

Examples of a calculated unbalance parameters are:

• Calculated_Maximum_Cell_Voltage:

the maximum of all Measured_Actual_Cell_Voltages during a key-on/key-off cycle.

• Calculated_Minimum_Cell_Voltage:

the minimum of all Measured_Actual_Cell_Voltages during a key-on/key-off cycle.

• Calculated_Delta_Cell_Voltage =

Calculated_Maximum_Cell_Voltage - Calculated_Minimum_Cell_Voltage:

the frequency of the control signal Control_Output_PWM_Frequency can be adapted to the parameter Calculated_Delta_Cell_Voltage. he table below shows specific defined learned unbalance parameters:

LEARNED ENTITY PARAMETER (unit)

Maximum Cell Voltage (V)

Minimum Substring Temperature (°C/ F)

Average Multisubstring Ohmic internal resistance (Ohm)

Filtered String Current (A)

Delta Multistring Charge (C)

Total Diffusion resistance (Ohm)

Root Mean Square Charge transfer polarization of

the positive electrode (F)

Deviation Charge transfer polarization of

the negative electrode (F)

Balanced Capacity between positive electrode

and electrolyte (F)

Capacity between negative

electrode and electrolyte (F)

Polarization resistance (Ohm)

State Of Charge (%)

State Of Health (%)

State Of Function (%) Activation polarisation (F)

Concentration polarization (F)

Capacity (Ah or F)

Leakage Current (imA)

Examples of learned unbalance parameters are:

• Learned_Maximum_Cell_Voltage:

the learned value of the Calculated_Maximum_Cell_Voltage.

· Learned_Delta_Cell_Voltage:

the learned value of the Calculaled_Delta_Cell_Voltage:

• The differential voltage Learned_Delta_Cell_Voltage for a number of cells can be tracked versus the Calculated_Total_Substring_Voltage in charging or discharging operation. The frequency of the control signal (Control_Output_PWM_Frequency) can be adapted such that the differential frequency is minimal when Calculated_Total_Substring_Voltage is reaching maximum when the cells are fully charged.

d) The table below shows control signal attribute settings based on unbalance parameters:

Example of an attribute setting: • Control_Output_PWM_Frequency, the frequency of the PWM signal used as output.

B/ MEASUREMENT SYSTEM AND DETERMINATION OF CALCULATED AND LEARNED UNBALANCE PARAMETERS. a) Measurement on energy storage device level:

The measured unbalance parameter is Measured_Actual_Cell_Voltage.

The measurement system uses a high precision difference amplifier with a high common-mode rejection ratio (CMRR). The inputs of this amplifier are connected to the appropriate nodes in the series connection of N cells by closing appropriate switches.

The actual voltages of the cells are supposed to have a positive voltage. If the high precision difference amplifier uses a reference voltage R, the absolute value of the difference between the output voltage and the reference voltage is a measure for the voltage of the cell.

Safety resistors and fuses are added to limit the current in case of a failure of one of the switches or their control circuit. b) Measurement on substring of energy storage devices level

The measured unbalance parameter is Measured_Actual_Substring_Current.

Given the nature of the applied current transducers (e.g. 0 to +/- 400A) and electronic interfaces, deviations are obtained with current readings. Not only fluctuate these deviations from system to system, but during their lifetime components (e.g. current transducers) have the tendencies to change over time (aging) or even during external conditions (temperature, humidity, etc). In addition reading has to be accurate at low current during the so-called pre-charge phase (few Amperes). For this purpose at each key-on of the system the measured deviation is determined and subtracted to allow optimal determination of the current values during the applied key-on/key-off cycle. An additional benefit for the manufacturer is the usage of a cheaper current transducer. See FIG 10

The following measured, calculated, and learned unbalance parameters can be determined:

• Measured_Actual_Substring_CurrentAtZero

• Learned_Actual_Substring_CurrentAtZero

• Calculated_Actual_Substring_Current = Measured_Actual_Substring_Current - Learned_Actual_Substring_CurrentAtZero

c) Measurement on multisubstring level:

With dual voltage measurement the measured unbalance parameters are:

Measured_Actual_Multisubstring_Low_Bank_Voltage and

Measured_Actual_Multisubstring_High_Bank_Voltage

An energy storage system as shown in FIG 1 1 , with positive high voltage terminal HV+ and negative high voltage terminal HV-, is internally consisting of a serial connection of two substrings, one identified as Low Bank Multisubstring and High Bank Multisubstring. The voltage over each substring is measured by Voltage Transducer 1 (over Low Bank Multisubstring) and by Voltage Transducer 2 (over High Bank Multisubstring). Following the unbalance parameters of these transducers, it is easily possible to determine the balancing behavior between both substrings in relation with the total high voltage value.

• Measured_Actual_Multisubstring_Low_Bank_Voltage

• Measured_Actual_Multisubstring_High_Bank_Voltage

· Calculated_Filtered_Multisubstring_Low_Bank_Voltage

• Calculated_Filtered_Multisubstring_High_Bank_Voltage

• Calulated_Balanced_Multisubstring_Low_Bank_Voltage, • Calculated_Balanced_Multisubstring_High_Bank_Voltage

Wherein Calculated_Balanced_Multisubstring_Low_Bank_Voltage =

100% ^* Calculated_Filtered_Multisubstring_Low_Bank_Voltage /

(Calculated_Filtered_Multisubstring_Low_Bank_Voltage +

Calculated_Balanced_Multisubstring_High_Bank_Voltage)

and wherein Calculated_Balanced_Multisubstring_High_Bank_Voltage =

100% ^* Calculated_Filtered_Multisubstring_High_Bank_Voltage /

(Calculated_Filtered_Multisubstring_Low_Bank_Voltage +

Calculated_Balanced_Multisubstring_High_Bank_Voltage)

• Learned_ Balanced_Multisubstring_Low_Bank_Voltage

• Learned_ Balanced_Multisubstring_High_Bank_Voltage Voltages from the individual substrings are measured by individual substring controllers and provided towards the system controller via CAN. In addition, the total system voltage is measured by two separate voltage transducers (upper and lower bank). The system controller determines which substring controllers are located in which bank and determines the different system and bank voltages via dual mode (sum of substring voltages, bank voltages). In case one substring voltage is failing per bank the system determines the missing voltage per bank (backup values) and provides the missing information via CAN towards the other substring controllers and the application making the overall system more robust and reliable. In addition this information is used to determine the overall system balancing behaviour with dedicated diagnostic malfunction code in case of system unbalance detection.

Isolation Voltage Measurement:

An energy storage system, with positive high voltage terminal HV+ and negative high voltage terminal HV-, is connected towards following circuitry. See FIG 12

A virtual point of equilibrium (VP) is obtained between HV+, HV-, and chassis of the application by the introduction of R1 , R2, R3a, R3b where R1 = R2 = R3a + R3b. This means that there are reference current leaks introduced between HV+, HV-, and Chassis.

Any disturbances caused by external leak currents between HV+, HV-, and chassis will lead towards a modification of the point of equilibrium, which will result into a deviation of Vout.

By applying a specific circuit topology ('star') between the different potential voltages (HV+, HV-, and chassis of the application) a virtual point is defined with 'reference current leaks'. The current leak towards ground is scaled and provided with a negative offset by the introduction of a voltage polarity inverter and fed into an operational amplifier, providing a unipolar analogue signal readable by the system controller. The digital signal, obtained from the analogue signal via ADC with dedicated analogue and digital filtering, is then applied with a specific algorithm that allows measurement of the deviation from the reference leak currents and detection of an isolation failure when exceeding calibratable thresholds. Similar approaches can be obtained with other topologies like 'triangle' or 'pi'.

• Measured_Actual_Multisubstring_lsolation_Voltage

• Calculated_Filtered_Multisubstring_lsolation_Voltage

• Learned_Deviation_Multitring_lsolation_Voltage CI CHARGE TRANSFER SYSTEM for restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices. a) Balancing within a substring of energy storage devices:

a detailed embodiment is illustrated in FIG 13. b) Intersubstring balancing:

The intersubstring balancing is used to balance substrings of cells with each other. A balancing mechanism between these substrings is certainly necessary, however using such a balancing system to solve problems of certain substring malfunctions is not recommended.

Balancing by turning off intersubstring balancing

When the energy storage devices, consisting of several substrings of cells, is not used (not charged or discharged for a longer time), the intersubstring balancing can be kept active and dependent for the power supply on its own energy. Intersubstring balancing can be achieved by turning of each within-substring balancing at a predefined string voltage. By turning-off the balancing in this substring, no more power of the substring will be consumed by the switches and the voltage will remain at the turn-off voltage. If all substrings are configured like this and they can all keep balancing for a sufficient time, all substrings will eventually reach the same substring voltage and will be balanced. When this method is used additional intersubstring balancing might not be recommended.

Capacitive balancing Version 1 : see FIG 5a

A section of the M first cells of a substring can be balanced with a section of the M last except one cells of the previous substring. When M is chosen 3 and the substring has N cells, cells 1 , 2 and 3 are balanced with cells N-3, N-2 and N-1 of the previous string. There should be at least one capacitor between switches SA2 and SB1 .This increases the voltage at which the balancing takes place and as such increases the efficiency of the balancing.

In the first state switches SAI and SA2 are closed to let capacitor Cbal exchange energy with the section of cells Cn, C1 , C2, C3. In the second state switches SB1 and SB2 are closed to let capacitor Cbal exchange energy with the section of cells C(N-3), C(N-2), C(N-1 ) and CN. By switching between these two states the balancing between the substrings is guaranteed. Version 2: see FIG 5b

Another way to create the same balancing behaviour and efficiency is to take cell C1 as the cell included in the two non-adjacent sections connected to capacitor Cbal in both switch states instead of the last cell of the previous substring.

The control is similar as in version 1 but now the two series connection of cells are C(N-2), C(N-1 ), CN, C1 and C1 , C2, C3, C4. c) Assembly balancing

When deviations in current or voltage (positive or negative) are detected, the assembly is automatically protected by regulating or opening one or more contactors or fuses bringing the assembly into a safe mode by limiting or decoupling energy flow between the assembly and the application. This is determined by comparing the current or voltage dynamics versus the allowed contactor or fuse characteristics. These characteristics are located in a so-called lookup table which allows the manufacturer to program any fuse type characteristic. Deviations can be registered with specific malfunction code.

D/ CONTROLLED ADAPTATION MANAGEMENT (CAM) WITH CELL LEARNING PARAMETER AND CELL INTEGRATION PARAMETER FUNCTIONALITY The performances, efficiencies, and lifetime of energy storage systems will be improved if compensations or adaptations can be made on deviations from external or internal origin. Cell Learning is the long term adjustment embedded within an energy storage system. Cell Integration is handling the same functionality for short term parameter adjustments. Basically, both strategies are used to make adjustments and adaptations to the ever changing loads, atmospheric and thermal conditions, and energy deviations to ensure that the application (e.g. vehicle) is providing the requiring power and energy (driveability and emissions) over a long lifetime. The two-dimensional table below contains for each individual cell and specific cell characteristic a Cell Learn Parameter (CLP), which represents a long-term correction based on that cell's operating conditions over a relatively long period of time. Cell Id/Cell P1 P2 P3 ...

Characteristic

...

X-1 CLP_1 ,X-1 CLP_2,X-1 CLP_3,X-1

X CLP_1 ,X CLP_2,X CLP_3,X

X+1 CLP_1 ,X+1 CLP_2,X+1 CLP_3X+1

...

The "cell learning" (updating CLP values) is enabled when the following requirements and/or conditions are met:

- application active or a minimum of energy present within storage system

- learning threshold for individual cell and specific parameter is exceeded

- current value is significantly deviating from previous value during a predefined time

Cell learning is a long term adjustment, which is stored permanently (e.g flash eprom) or sometimes temporary (e.g. RAM) and updated during "leaning mode". At power-up of the embedded controllers the cell integrator is set at an initial value and kept there until predefined conditions are met or predefined unbalance parameters reaches certain threshold values. Each CLP value is applied with a specific Cell Integrator value, which is a short term correction based on immediate operating conditions.

The Integrator value and CLP values represents a correction to the internal energy flow (energy recirculation or regulation) and the external energy flow (energy transfer towards or from the application) by e.g. Control_Output_PWM_Frequency.

Furthermore the obtained values will be applied for determining energy storage system characteristics like Stage of Charge (SOC) and State of Health (SOH), and diagnostics with associated Diagnostic Trouble Codes (DTCs).

Claims

CLAIMS:

1 . A method for balancing a series connection of energy storage devices comprising:

2. A method according to claim 1 , wherein the series connection is part of an assembly, and wherein the unbalance parameter is measured, calculated, or learned, as well as its type, and/or a status, and/or a value and/or deviation determined, on any assembly level such as individual energy storage device level, substring of energy storage devices level, multi-substring of energy storage devices level, on section level, on total series connection level, on system level or on application level or a combination thereof.

3. A method according to claim 1 or 2, wherein the energy flow(s) are restricted, generated or adapted on individual energy storage device level, substring of energy storage devices level, multi-substring of energy storage devices level, on section level, on total series connection level, on system level or on application level or a combination thereof.

4. A method according to claims 1 to 3, wherein restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices includes restricting, generating or adapting any energy flow or charge transfer in, to, or over the series connection of energy storage devices at any assembly level, or any current flow or charge transfer in, over, to an intermediate storage element, a (pre-charge) contactor, a switch, an electric connection, a controller, a fuse or a peripheral element in an assembly including the series connection.

5. A method according to any of the above claims, wherein said measuring may be performed by capturing voltage or current.

6. A method according to any of the above claims, wherein said calculating may be performed by mathematical operations and filtering techniques.

7. A method according to any of the above claims, wherein said learning may be performed by capturing history of the status, the value or the deviation of an unbalance parameter, and predicting said status, value or deviation.

8. A method according to any of the above claims, wherein measuring, calculating or learning an unbalance parameter in a series connection of energy storage devices, determining a type, and/or a status, and/or a value and/ or a deviation of the unbalance parameter, and restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices comprises controlling a switching means by means of a control signal having attribute settings wherein said attribute settings are adapted as a function of said unbalance parameter or a set of said unbalance parameters.

9. A method according to claim 8, comprising the steps of:

a. providing a series connection of energy storage devices,

b. selecting from said series connection a pair of non-adjacent sections (d) of one or a number of adjacent energy storage devices (a1 , a2, a3), said sections to be balanced to each other and each having a more positive terminal (A) at one end and a more negative terminal (B) at its other end,

c. controlling a switching means by means of a control signal having attribute settings such that said switching means switches sequentially between coupling the terminals A to each other via said intermediate storage elements and coupling the terminals B to each other via said intermediate storage elements; said attribute settings being adapted as a function of said unbalance parameter or a set of said unbalance parameters.

10. Use of a method according to any of the above claims, for balancing a series connection of electric double-layer capacitors, lithium capacitors, electrochemical battery devices and battery packs, and lithium battery devices like lithium-polymer and lithium-ion battery devices, and blended combinations thereof.

1 1 . A system for balancing a series connection of energy storage devices comprising:

12. A system according to claim 1 1 , wherein the energy flow includes any current flow or charge transfer to be restricted, generated or adapted in, to, or over the series connection of energy storage devices at any assembly level, or any current flow or charge transfer in, over, to an intermediate storage element, a (precharge) contactor, a switch, an electric connection, a controller, a fuse or a peripheral element in an assembly including said series connection.

13. A system according to claim 12, wherein the means for determining a measured, calculated or learned unbalance parameter in a series connection of energy storage devices, the means for determining a type, and/or a status, and/or a value and/or a deviation of the unbalance parameter, and the means for restricting, generating or adapting an energy flow in, over, or to the series connection of energy storage devices comprise a switching means receiving a control signal wherein said control signal has attribute settings adapted as a function of said unbalance parameter or set of said unbalance parameters.

14. A system according to claim 13 comprising:

b) and a switching means (c) receiving a control signal for switching sequentially between coupling terminals (A) to each other via said intermediate storage element and coupling terminals (B) to each other via said intermediate storage element; said control signal has attribute settings adapted as a function of said unbalance parameter or a set of said unbalance parameters.

15. Use of a system according to claims 1 1 to 14, for balancing a series connection of electric double-layer capacitors, lithium capacitors, electrochemical battery devices and battery packs, and lithium battery devices like lithium-polymer and lithium-ion battery devices, and blended combinations thereof.