GB2601017A

GB2601017A - Reconfigurable electric batteries

Info

Publication number: GB2601017A
Application number: GB2106164.3A
Authority: GB
Inventors: Golubev Ilia; Shikhov Yury
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-11-17
Filing date: 2021-04-29
Publication date: 2022-05-18
Anticipated expiration: 2041-04-29
Also published as: GB2601017B; GB202106164D0

Abstract

A reconfigurable battery, comprising: at least two battery cell sections BCS connected in series, each battery cell section comprising two controllable switches and at least one battery cell BC; wherein in each battery cell section, the two controllable switches are operable to either set the battery cell section to an active mode where the battery cell is connected to the battery’s electrical circuit, or set the battery cell section to an idle mode such that the battery cell is bypassed; and control means configured to monitor and control each of the at least two battery cell sections; wherein whenever a switching condition (e.g. state of charge, state of health, temperature of the cell or switches, a time interval or a battery cell type) is fulfilled, the control means controls the switches of each of battery cell section such that the mode of the at least one battery cell of that battery cell section is changed.

Description

RECONFIGURABLE ELECTRIC BATTERIES

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for reconfiguring electric batteries, in particular for reconfiguring multi-module batteries.

Background to the Invention

To fight against climate change and global warming, it is an inevitable trend to progressively increase the percentage of renewable energy in electricity generation and the usage of green technologies in people's daily lives. As one of the most crucial enabling technologies of the 21st Century, electric batteries are under a fast-paced and extensive development and have found a wide range of applications, e.g., from storing energy generated by renewable energies to powering different electrical devices such as smartphones and electric vehicles.

However, today's widespread usage of batteries has highlighted many critical issues some of which are listed as follows: * whole battery failure as a result of a single cell failure; * the formation of an undesirable difference in charges in battery cells; * impossibility of mixing cells with a different chemical composition in one battery; * impossibility of mixing cells with a different state-of-health (SOH) in one battery; * impossibility of changing the number of cells in a battery for keeping the same operational voltage; * battery voltage dependency on a state-of-charge (SOC), state-of-health(SOH) and battery current, * power losses associated with battery management; and * additional weight and size associated with battery management system. 30 While the aforementioned issues are partially addressed by various battery management systems (BMS), existing solutions, however, are often accompanied by other problems such as for example the increased complexity of the technical implementation, limited functionality, significantly increased weight and power draw.

In existing BMS, battery management is typically done by measuring the voltage and current across the individual cells that make up the battery and processing those parameters within the battery or outside of it. Based on those parameters, the SOC (state-of-charge) of the battery cell and SOH (state-of-health) or degree of deterioration are estimated. When a difference in the charge of individual cells is detected, the balancing system is activated, which aims to equalize the charge level between the o cells. Different methods can be used to achieve this, such as using transformer converters, using inductive or capacitive storage elements, using switched battery elements, using balancing resistors or others. In case of reaching any of the peak (or threshold) parameters for any cell, the entire battery is disconnected and disabled. In other words, the lack of ability to flexibly replace or isolate any problematic cell in the battery results in the life of the whole battery being significantly limited by any short-lived problematic cell of the battery. Such way of operation is inefficient and not cost-effective.

Objects and aspects of the present claimed invention seek to alleviate at least these

problems with the prior art.

Summary of the invention

According to a first aspect of the present invention, there is provided a reconfigurable battery, comprising: at least two battery cell sections connected in series, each battery cell section comprising two controllable switches and at least one battery cell; wherein in each battery cell section, the two controllable switches are operable to either set the battery cell section to an active mode such that the at least one battery cell is connected to the battery's electrical circuit, or set the battery cell section to an idle mode such that the at least one battery cell is bypassed from the battery's electrical circuit; and control o means configured to monitor and control each of the at least two battery cell sections; wherein whenever a switching condition is fulfilled for any of the at least two battery cell sections, the control means is operable to control the controllable switches of each of that battery cell section such that the mode of that battery cell section is changed.

Preferably, the switching condition for each of the at least two battery cell sections is based on one or more of: a state of charge (SOC) of the at least one battery cell; a state of health (SOH) of the at least one battery cell; a temperature of the at least one battery cell; a temperature of each of the two controllable switches; a time interval; or a battery cell type.

Preferably, the control means is operable to change the mode of at least two battery cell sections in order to maintain substantially the same battery voltage.

Preferably, the control means is operable to rank each of the at least two battery cell sections in accordance with its SOC.

Preferably, during a discharging process, the control means is operable to identify, based on the SOC ranking of the at least two battery cell sections, the active battery cell section with the lowest SOC among all active battery cell sections, and the idle battery cell section with the highest SOC among all idle battery cell sections.

Preferably, the control means is operable to further change the active battery cell section with the lowest SOC to the idle mode and the idle battery cell section with the highest SOC to the active mode when the SOC of the active battery cell section is no more than that of the idle battery cell section.

Preferably, during a charging process, the control means is operable to identify, based on the SOC ranking of the at least two battery cell sections, the idle battery cell section with the lowest SOC among all idle battery cell sections, and the active battery cell section with the highest SOC among all active cell sections.

Preferably, the control means is operable to further change the idle battery cell section 15 with the lowest SOC to the active mode and the active battery cell section with the highest SOC to the idle mode when the SOC of the idle battery cell section is no more than that of the active battery cell section.

Preferably, during a discharging process, the control means is operable to identify the active battery cell section with the lowest voltage and the idle battery cell section with the highest voltage.

Preferably, the control means is operable to further change the active battery cell section with the lowest voltage to the idle mode and the idle battery cell section with the highest voltage to the active mode.

Preferably, the control means is operable to permanently set a battery cell section to the idle mode when the SOH of the at least one battery cell of the battery cell section is below a threshold SOH.

Preferably, the control means is operable to change the mode of any of at least two battery cell sections when the temperature of the at least one battery cell of the battery cell section is either above a maximum cell temperature or below a minimum cell temperature.

Preferably, the control means is operable to change the mode of any of at least two battery cell sections when the temperature of any of the two controllable switches is above a maximum switch temperature.

Preferably, the control means is operable to change the mode of one or more of at least two battery cell sections at time intervals.

Preferably, in any of the at least two battery cell sections, the at least one battery cell is of a single cell type.

Preferably, the at least two battery cell sections comprise at least two different cell 15 types.

Preferably, the control means is operable to set one or more of the at least two battery cell sections of a specific cell type to the active mode and any other battery cell section of a different cell type to the idle mode where the specific battery cell type is desired for a certain application.

Preferably, the at least two battery cell sections comprise one or more battery cell sections each having one or more energy storage cells and one or more battery cell sections each having one or more power cells, further wherein the control means is operable to set some or all of the one or more battery cell sections each having one or more power cells to the active mode where a short term heavy load is to be supplied.

Preferably, the two controllable switches of each of the least two battery cell sections are connected in series and comprise a first switch terminal, a second switch terminal and a common switch terminal wherein each battery cell section is configured such that the first switch terminal is connected to a positive terminal of the at least one battery cell, the second switch terminal is connected to a negative terminal of the at least one battery cell, and the common switch terminal is connected to another battery cell section.

Preferably, the control means is operable to change a switch state of one or both of the two controllable switches in order to change the mode of the at least one battery cell of that battery cell section.

Preferably, the at least one battery cell comprises two or more battery cells which are connected in series-parallel connection.

Preferably, each of the at least two battery cell sections further comprises an internal balancing circuit configured to balance the SOC of each of the at least one battery cell during battery's operation.

Preferably, the reconfigurable battery is configured in such a modular manner that each of the at least two battery cell sections is enclosed in a battery module and all the battery modules are connected in series, each battery module comprising: battery control means and module control means; an upstream interface; and a downstream interface.

Preferably, the battery control means, when activated, is operable to communicate with other battery modules via the downstream interface of the same battery module and to decide on the mode of each battery module which is in effect the mode of the battery cell section of the battery module.

Preferably, the module control means of each battery module is operable to communicate with the battery control unit and to control the mode of the battery cell section by controlling the two controllable switches.

Preferably, the reconfigurable battery is configured to activate the battery control means when the corresponding battery module is selected to be the only master module of the battery.

Preferably, the reconfigurable battery is configured to inhibit the battery control means of each slave battery module.

Preferably, the module control means of each slave battery module is operable to communicate with the battery control means of the master module via the upstream interface of the battery module.

Preferably, the battery control means is operable to regulate an output battery voltage by calculating a difference voltage between the output battery voltage and a reference battery voltage and change the mode of one or more of the battery modules whenever the difference voltage is above a threshold voltage.

According to a second aspect of the present invention, there is provided a method for operating a reconfigurable battery comprising: at least two battery cell sections connected in series, each battery cell section comprising two controllable switches and at least one battery cell; wherein in each battery cell section, the two controllable switches are operable to either set the battery cell section to an active mode such that the at least one battery cell is connected to the battery's electrical circuit, or set the battery cell section to an idle mode such that the at least one battery cell is bypassed from the battery's electrical circuit; and control means configured to monitor and control each of the at least two battery cell sections; the method comprising: monitoring each of the at least two battery cell sections; and changing the mode of a battery cell section whenever a switching condition is fulfilled for that battery cell section.

Detailed Description

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 depicts a schematic of an existing battery comprising four serially connected battery cells; Figures 2(a)-2(d) depict four different configurations of a reconfigurable battery in accordance with an embodiment; Figures 3(a)-3(c) depict the charging or discharging process of three reconfigurable batteries, each being arranged in the same manner as any of examples shown in to Figures 2(a)-2(d), in accordance with an embodiment; Figure 4 depicts the discharging process of each of ten battery cells of a battery without implementing the battery balancing method used in the examples shown in Figures 3(a)-3(c); Figure 5 depicts the discharging process of each of ten battery cells of a battery after implementing the battery balancing method used in the examples shown in Figures 3(a)-3(c); Figures 6 depicts a cell balancing period of the discharging process shown in Figure 5; Figure 7 depicts a steady state period of the discharging process shown in Figure 5; Figure 8 is a flowchart showing a balanced battery operation during the discharging 25 process of a reconfigurable battery in accordance with an embodiment; Figure 9 is a flowchart showing a balanced battery operation during the charging process of a configuration battery in accordance with an embodiment; Figure 10 depicts the discharging process of a used reconfigurable battery configured with one redundant battery cell in accordance with an embodiment; Figure 11 depicts a reconfigurable battery comprising two different types of battery cells in accordance with an embodiment; Figure 12 depicts a large-scale reconfigurable battery in accordance with an 5 embodiment; Figure 13 depicts a packaged large-scale reconfigurable battery in accordance with an embodiment; and to Figure 14 depicts a packaged multi-module reconfigurable battery in accordance with an embodiment.

With reference to Figure 1, the example battery consists of four battery cells that are connected in series and wired between the positive and negative terminals of the battery. In such a configuration, when any battery cell fails or has insufficiently low charge, the whole battery will not function properly, e.g., providing low or no output voltage, and will thus have to be replaced completely.

To extend the life of a battery, it is thus desirable to have flexible control over each individual battery cell such that any battery cell in the battery can be selectively connected or disconnected for example in accordance with an application need and/or an operational state of the battery. In such a manner, all the battery cells of the battery can operate in a much more balanced manner, that is, all the battery cells of the battery can maintain a substantially equalised charge level either during the charging or discharging stage. The embodiments described herein are capable of providing such flexible battery power management.

Figures 2(a)-2(d) depict four different configurations of a reconfigurable battery in accordance with an embodiment. In the embodiment, the battery may comprise four battery cells BC1-BC4 and eight controllable switches CS1-CS8. The battery cells and controllable switches may be connected in such a way that the battery can be regarded as a string of four serially connected battery cell units, each comprising one battery cell and two controllable switches. The battery cells BC1-BC4 may be for example energy storage cells. The controllable switches may be electrically operated switches, such as power transistors (e.g., metal-oxide-semiconductor field-effect transistors (MOSFETs)).

For example, with reference to Figure 2(a), the battery cell unit BCU as indicated by the dashed circle may comprise one battery cell BC1 and two controllable switches CS1, CS2. The two controllable switches CS1, 052 may be connected in series with each other and may provide a first switch terminal Ti, a common switch terminal TO and a second switch terminal T2, which may respectively be connected to the positive terminal of battery cell BC1, the positive terminal of battery cell BC2 in the adjacent battery cell unit, and the negative terminal of battery cell BC1. Each of the eight controllable switches may be individually controlled by a control unit (not shown) of the battery. Each controllable switch may have an ON state and an OFF state corresponding respectively to the conduction state and the non-conduction state of the switch. When controllable switch CS1 is set to the OFF state and controllable switch CS2 is set to the ON state, battery cell BC1 may be connected to the string of battery cell units and be regarded as in an active mode. In contrast, when controllable switch CS1 is set to the ON state and controllable switch CS2 is set to the OFF state, battery cell BC1 may be disconnected from the string of battery cell and be regarded as in an idle mode. In this case, the battery current may flow through controllable switch 051.

Figure 2(a) depicts a first configuration where all controllable switches are in the OFF state, resulting in each of the battery cells being disconnected and the battery not outputting any electricity.

Figure 2(b) depicts a second configuration where controllable switches CS1, CS3, 055, CS7 are set to the OFF state while controllable switches 052, 054, CS6, 058 are set to the ON state. In such a configuration, the four battery cells are connected in series, thus equivalent to the example battery shown in Figure 1.

Figure 2(c) depicts a third configuration where controllable switches CS1, CS4, 055, 0S7 are set to the OFF state while controllable switches CS2, CS3, CS6, CS8 are set to the ON state. Since controllable switch CS4 is set to the OFF state controllable switch CS3 is set to the ON state, battery cell BC2 is thus disconnected from the electrical circuit of the battery or the battery cell unit string and the battery current flows via controllable switch CS3 instead. The other three battery cells BC1, BC3, BC4 are connected to the battery cell unit string and hence contribute to the output of the battery, e.g., the output voltage is the sum of the voltage of each battery cell BC1, BC3, BC4.

Figure 2(d) depicts a fourth configuration where controllable switches C52, CS3, CS5, 0S7 are set to the OFF state while controllable switches CS1, CS4, CS6, CS8 are set to the ON state. In this configuration, battery cell BC1 is disconnected from the battery cell unit string and the other three cells BC2, BC3, BC4 are connected to the battery cell unit string and thereby contribute to the output of the battery.

Note that, only one controllable switch is in the ON state in steady state operation.

During mode switching, i.e. when a battery cell in a battery cell unit is switched from the active mode to the idle mode or from the idle mode to the active, the break-before-make technique is used, that is firstly the controllable switch in the ON state goes to the OFF state, then the controllable switch in the OFF state goes to the ON state. As such, there is a moment when both controllable switches are in the OFF state.

A battery balancing method is proposed to control the operation of the reconfigurable battery shown in any of Figures 2(a)-2(d). In the proposed battery balancing method, during operation, any active battery cell may be switched to the idle mode in accordance with an operational state of the cell and in the meantime an idle battery cell may be switched to the active mode in order to maintain substantially the same output voltage. The operational state may be for example the state of charge (SOC), state of health (SOH), output voltage, output current or temperature of the battery cell. Alternatively or additionally, during operation, the operating mode (i.e. the active mode or the idle mode) of any battery cell may be switched upon receiving an external request, e.g., for a different output voltage. The operational state of the cell may be monitored continuously or periodically by a control unit.

Figure 3(a) depicts the charging process of a reconfigurable battery with five originally unbalanced battery cells. As shown in the figure, the battery may comprise five energy storage cells ESC21-E5C25 and ten controllable switches CS, the energy storage cells and controllable switches being arranged in the same manner as the reconfigurable battery shown in any of Figures 2(a)-2(d), i.e. the operating mode (the active mode or the idle mode) of each battery cell is controlled by two controllable switches. The controllable switches may be individually controlled by a control unit of the battery. Among the five energy storage cells, energy storage cell ESC23 may have been substantially discharged and thus have a much lower SOC in comparison with the other four cells ESC21, ESC32, ESC24, ESC25 which may have substantially the same SOC (e.g., 50% SOC). The control unit of the battery may be configured to monitor the operational state (e.g., SOC) of each energy storage cell and may identify such an energy storage cell with the lowest SOC. In some embodiments, the monitoring of each energy storage cell may be performed periodically, i.e. at predefined time intervals.

Usually, the SOC of a battery cell (e.g., an energy storage cell) cannot be measured directly but it can be estimated with a reasonably good accuracy from direct measurement of other parameters of the battery cell. Many SOC estimation methods have been developed and implemented in various types of batteries. By way of an example, the SOC of a battery can be estimated based on an open circuit voltage (OCV) of the battery and an accumulation of current flowing through the battery. The SOC of the battery can be calculated using the following three equations: OCV = V - [1] SOC = f K1 x Idt + K2 x SOC(OCV), [2] SOC = f K3 x kit + K4 x SOC(OCV). [3] Where OCV denotes the open circuit voltage, V, R, I denote respectively the voltage, resistance and current of the battery, Ki denotes a charge efficiency while the battery is being externally charged, K2 is a weighting coefficient while the battery is being externally charged, K3 denotes a charge efficiency while the battery is not being externally charged, and K4 denotes a weighting coefficient while the battery is not being externally charged. More detailed and accurate procedure for SOC calculation is given in EP2159099B1, which is incorporated herein by reference.

With continued reference to Figure 3(a), during the charging process, the control unit may keep energy storage cell E5C23 with the lowest SOC to the active mode and allow the cell ESC23 to continuously receive energy and accumulate charge. The control unit may control the controllable switches associated with the other four energy storage cells ESC21, ESC22, ESC24, ESC25 in such a manner that the operating mode of each of the energy storage cells ESC21, E5C22, E5C24, ESC25 alternates between the active mode (being charged) and the idle mode (not being charged). While in the idle mode, an energy storage cell may maintain existing energy and may not contribute to the battery's operation either in charging or in discharging processes.

For example, in a first charging state CS1 of the charging process, energy storage cell ESC21 is set to the idle mode and energy storage cells E5C22, E5C24, E5C25 are set to the active mode. As mentioned above, energy storage cell ESC23 with the lowest SOC is kept in the active mode. In a second charging state CS2, the control unit may switch the mode of energy storage cell ESC21 from the idle mode in the first charging state CS1 to the active mode and switch the mode energy storage cell E5C22 from the active mode to the idle mode. In a third charging state CS3, the control unit may switch the mode of energy storage cell ESC22 from the idle mode to the active mode and switch the mode energy storage cell ESC24 from the active mode to the idle mode. In a fourth charging state C54, the control unit may switch the mode of energy storage cell E5C24 from the idle mode to the active mode and switch the mode of energy storage cell ESC25 from the active mode to the idle mode. The control unit of the battery may repeat the aforementioned four charging states until all the energy storage cells are fully charged. The mode switching of energy storage cells ESC21, ESC22, ESC24, ESC25 may occur whenever a switching condition is fulfilled. The switching condition may be determined based on one or more of the following factors: the SOC of each cell; the SOH of each cell; the temperature of each cell; the temperature of each controllable switch; the type of each cell; or a predefined regular time interval.

For example, whenever a switching condition is fulfilled (e.g., at certain regular time internals), the control unit may change the charging state of the battery in a predefined order e.g., from CS1 to CS2 to CS3 to CS4 to CS1. This control routine may be able to balance the battery by allowing energy storage cells ESC21, ESC22, ESC24, ESC25 with a higher initial charge to receive less energy, while energy storage cell ESC23 with a lower initial charge to receive more energy.

Figure 3(b) depicts the discharging process of a reconfigurable battery with five originally unbalanced battery cells. The reconfigurable battery may comprise five energy storage cells and ten controllable switches and may be arranged in the same manner as the battery shown in Figure 3(a) or any of Figures 2(a)-2(d). The operating mode of each energy storage cell may be controlled by two controllable switches. Among the five energy storage cells, energy storage cell ESC34 may be a new and fully charged cell and hence may have a much higher SOC in comparison with the other four cells ESC31, ESC32, ESC33, ESC35 which may have may substantially the same SOC. The control unit of the battery may be configured to monitor the operational state (e.g., SOC) of each energy storage cell and may identify such an energy storage cell with the highest SOC.

In contrast to the charging process, during the discharging process, the control unit may keep energy storage cell ESC34 with the highest SOC to the active mode and force energy storage cell ESC34 to continuously supply energy to e.g., an external load. The control unit may control the controllable switches associated with the other four energy storage cells ESC31, ESC32, ESC33, ESC35 in such a manner that the operating mode of each of the energy storage cells ESC31, ESC32, ESC33, ESC35 alternates between the active mode (being discharged) and the idle mode (not being discharged).

For example, in a first discharging state DS1 of the discharging process, energy storage cell ESC31 is set to the idle mode and energy storage cells ESC32, ESC33, ESC35 are set to the active mode. As mentioned above, energy storage cell ESC34 with the highest SOC is kept in the active mode. In a second discharging state DS2, the control unit may switch the mode of energy storage cell ESC31 from the idle mode to the active mode and switch the mode energy storage cell ESC32 from the active mode to the idle mode. In a third discharging state DS3, the control unit may switch the mode of energy storage cell ESC32 from the idle mode to the active mode and switch the mode energy storage cell ESC33 from the active mode to the idle mode. In a fourth discharging state DS4, the control unit may switch the mode of energy storage cell ESC33 from the idle mode to the active mode and switch the mode energy storage cell ESC35 from the active mode to the idle mode.

The control unit of the battery may repeat the aforementioned four discharging states until all the battery cells are completely discharged or until the energy supply from the battery is no longer needed. The mode switching of energy storage cells ESC31, ESC32, ESC33, ESC35 may occur whenever a switching condition is fulfilled. The switching condition may be determined based on one or more of the following factors: the SOC of each cell; the SOH of each cell; the temperature of each cell; the temperature of each controllable switch; the type of each cell; or a predefined regular time interval.

For example, whenever a switching condition is fulfilled (e.g., at certain regular time internals), the control unit may change the discharging state of the battery in a predefined order e.g., from DS1 to DS2 to DS3 to DS4 to DS1. This control routine may allow to balance the battery by allowing energy storage cells ESC31, ESC32, ESC33, ESC35 with a lower initial charge to supply less energy, while energy storage cell ESC33 with a higher initial charge to supply more energy. In some embodiments, the number of active energy storage cells as well as the number of idle energy storage cells in the battery may remain constant at any given moment of time during both charging and discharging processes.

Figure 3(c) depicts the charging or discharging process of a reconfigurable battery with four originally balanced battery cells. The reconfigurable battery may comprise five energy storage cells having substantially the same SOC (e.g., 50% SOC) and ten controllable switches and may be arranged in the same manner as the battery shown in any of Figures 2(a)-2(d). In this case, the battery may be operable to keep all the energy storage cells balanced during the charging or discharging process. As shown in the figure, during the charging or discharging process, the control unit may alternately switch the mode of the four energy storage cells ESC41-ESC44 of the originally balanced battery between the active mode and the idle mode. For example, in a first charging or discharging state Si, energy storage cell ESC41 is set to the idle mode and the other three energy storage cells ESC42 to ESC44 are set to the active mode. In a second charging or discharging state S2, the control unit may switch the mode of energy storage cell ESC41 from the idle mode to the active mode and switch the mode energy storage cell ESC42 from the active mode to the idle mode. In a third charging or discharging state S3, the control unit may switch the mode of energy storage cell ESC42 from the idle mode to the active mode and switch the mode energy storage cell ESC43 from the active mode to the idle mode. In a fourth discharging state 34, the control unit may switch the mode of energy storage cell ESC43 from the idle mode to the active mode and switch the mode of energy storage cell ESC44 from the active mode to the idle mode.

Same as the examples shown in Figures 3(a) and 3(b), the control unit may repeat the four states until all the battery cells are completely discharged or until the energy supply from the battery is no longer needed. For example, whenever a switching condition is fulfilled (e.g., at certain regular time internals), the control unit may change the charging or discharging state of the battery in a predefined order e.g., from Si to S2 to S3 to S4 to Si. As such, any energy storage cell ESC41 to ESC 44 in the battery may receive or deliver substantially the same amount of energy so as to ensure the battery stay in the balanced condition during continuous operation.

Note that, a reconfigurable battery generally comprises more battery cells than actually needed, for example, to satisfy load voltage requirements. Hence, the number of battery cells that are set to the active mode is less than the total number of battery cells contained in the battery. In this particular example shown in Figure 3(c), the battery comprises a total of four battery cells but only three cells are active at any given moment of time while one other cell is always idle. So, the total output voltage of the battery is a sum of the voltage of the three battery cells that are in the active mode.

However, the total energy capacitance of the battery is equal to the overall energy capacity of the four energy cells ESC41-ESC44. The above described battery balancing method can be useful in cases where battery cells have, for example, different original energy capacity, different SOH or different SOC.

With reference to Figure 4, the battery may comprise ten battery cells that are connected in series. The battery may be in a fixed configuration as the example shown in Figure 1. Without the help of the battery balancing method, the ten battery cells having different SOH may discharge at different rates and may reach a minimal acceptable voltage at different times. Note that, a battery cell with a lower SOH typically discharges at a faster rate than a battery cell with a higher SOH. Also note that, typically, the output voltage of a battery is linearly proportional to the battery's SOC within a certain range of the output voltage, and thus can be used to indicate the SOC of the battery. As soon as one (e.g., energy storage cell ESC11 in Figure 4) of the ten battery cells reaches the lowest voltage, also known as low-cut-off voltage, the battery discharging process may be stopped in order to prevent permanent cell damage. At that moment, there is still a significant portion of unused energy present in other battery cells. Unused energy can be estimated with a gray rectangular 20 in Figure 4.

With reference to Figure 5, the battery may comprise ten battery cells that are connected in series and may further comprise twenty controllable switches. The battery cells (e.g., energy storage cells) and controllable switches may be connected in the same manner as any of the examples shown in Figure 2(a)-2(d), thereby allowing the operating mode of each battery cell to be flexibly controlled and thus the SOC of all the battery cells to be balanced. The ten battery cells may have different original SOC (manifested as different output voltages) and SOH. As shown in the figure, the initially separate discharging curves gradually converge after a period of time. Dashed rectangular 21 and dashed rectangular 22 represent respectively a cell balancing period during the initial discharging process and a steady state period after all the battery cells have reached a balanced state.

With reference to Figure 6, during the cell balancing period of the discharging process (as indicated by dashed rectangular 21 in Figure 5), the control unit of the battery may estimate the SOC of each battery cell and subsequently rank all the battery cells in accordance with their respective SOC. The control unit may then identify for example the three battery cells with the lowest SOCs and set them to the idle mode (the corresponding curve segment -24) until the SOC of at least one of other battery cells with higher original SOCs reaches substantially the same SOC. The control unit may set the other seven battery cells in the active mode such that they can continuously supply energy to an external load (the corresponding curve segment -23). The battery may be considered unbalanced until it reaches point 25, upon which all battery cells in the battery become balanced.

With reference to Figure 7(a), the steady state period may correspond to a portion of the discharge process after point 25 in Figure 6. The same period is indicated by dashed rectangular 22 in Figure 5. As shown in the figure, within the steady state period, the ten discharging curves may follow substantially the same slope or gradient. Here, the slope or gradient of a discharging curve represents the rate of change of voltage with respect to time. In other words, all the battery cells may discharge at substantially the same rate. However, each discharging curve may comprise a plurality of mode-switching features that are result from the mode of the battery cell being switched during the discharging process. For example, the discharging curve of one battery cell with a low SOH, as shown in Figure 7(b), may comprise a higher number of mode switching features (suggesting a higher frequency of mode switching) than the discharging curve of another battery cell with a high SOH, as shown in Figure 7(c). Since discharging curve 27 shown in Figure 7(b) has a greater gradient, the corresponding battery cell is thus a weak cell having a lower SOH. By contrast, the smaller gradient of discharging curve 28 shown in Figure 7(c) suggests that the corresponding battery cell is a strong cell having a higher SOH. Note that many different methods can be equally suitable for accurate estimation of the SOH of a battery cell. For example, U510386420B2 and US9791519B2 disclose two methods for calculation of the SOH of a battery, which are incorporated herein for reference.

At a certain moment in time, the strong cell (in Figure 7(c)) is switched (e.g., by the control unit of the battery) from the active mode to the idle mode, the moment of mode switching corresponding to fragment 29. Then, the strong cell spends a short period of time 30 in the idle mode and subsequently is switched back to the active mode, the moment of mode switching corresponding to fragment 31. At the same time, due to the fact that the weak cell (in Figure 7(b)) tends to lose its voltage (and thus SOC) more quickly than a strong cell, it is thus switched into the idle mode more often, thereby reducing the proportion of the active time in a certain time window. This is in contrast to the strong cell which has a higher proportion of the active time in the same time window.

Therefore, the battery balancing method is capable of balancing the SOC of different battery cells that have different SOC and/or SOH throughout the battery's operation.

Reconfigurable batteries such as those shown in Figures 2(a)-2(d) may be operated in different ways depending on the criteria for switching any given battery cell into the active mode or the idle mode. During operation, the control unit of a reconfigurable battery may perform various different control tasks in accordance with instructions (or operation steps) defined in the control routine or control algorithm which may be in the form of code. The control unit of the battery may comprise a memory and a processor used respectively for storing and executing the control routine. It should be noted that the control routine used for controlling mode switching of each battery cell is different for the charging process and the discharging process.

With reference to Figure 8, in an embodiment, the control unit may be configured to perform the following five operation steps during the discharging process: At step 810, the control unit may check the SOC of each active battery cell and may rank all the active battery cells in accordance with their respective SOC. The control unit may identify the active battery cell with the lowest SOC in the SOC ranking. The checking of the SOC of each battery cell may be achieved for example by periodical measurements of variables (e.g., voltage V, current I, resistance R) of each battery cell and subsequent estimation of the SOC of the cell based on the measurements.

At step 820, the control unit may continue to check the SOC of each idle battery cell and in a similar manner, identify the idle battery cell with the highest SOC.

At step 830, the control unit may compare the SOC of the identified active battery cell that has the lowest SOC among all the active cells with the SOC of the identified idle battery cell that has the highest SOC among all the idle cells. If the SOC of the active cell is higher than that of the idle cell, then the control unit may return to step 810; otherwise, the control unit may proceed to step 840.

At step 840, the control unit may switch the active battery cell into the idle mode, for example, by changing the ON/OFF states of the two controllable switches associated with the battery cell.

At step 850, the control unit may switch the idle battery cell into the active mode. 10 The above described discharging process may ensure that all the battery cells discharge at substantially the same rate.

With reference to Figure 9, in an embodiment, the control unit may be configured to perform the following five operation steps during the charging process: At step 910, the control unit may check the SOC of each idle battery cell and may rank all the idle battery cells in accordance with their respective SOC. The control unit may identify the idle battery cell with the lowest SOC in the SOC ranking. The checking of the SOC of each battery cell may be achieved for example by periodical measurements of variables (e.g., voltage V, current I, resistance R) of each battery cell and subsequent estimation of the SOC of the cell based on the measurements.

At step 920, the control unit may continue to check the SOC of each active battery cell and, in a similar manner, identify the active battery cell with the highest SOC.

At step 930, the control unit may compare the SOC of the identified idle battery cell that has the lowest SOC among all the idle cells with the SOC of the identified active battery cell that has the highest SOC among all the active cells. If the SOC of the idle cell is higher than that of the active cell, then the control unit may return to step 910; otherwise, the control unit may proceed to step 940.

At step 940, the control unit may switch the idle battery cell into the active mode, for example, by changing the ON/OFF states of the two controllable switches associated with the battery cell.

At step 950, the control unit may switch the active battery cell into the idle mode.

As it has been shown above, the battery balancing method can effectively manage battery configurations with battery cells of different SOC and SOH levels. Additionally, such methods can also allow for redundancy implementation to maintain normal battery operation even with multiple cell failures. Cell failure can occur due to different reasons, such as for example operating at a too high or too low voltage, operating at an over-temperature, operating at an under-temperature, or caused by mechanical damage. Some cell failures like mechanical damage are permanent, while others like under-temperature induced cell failure are temporary. Cell failure condition is also known as SOF (state-of-fail). To handle single or multiple cell SOF the battery may be designed and configured with several redundant cells.

With reference to Figure 10, the reconfigurable battery may have been used and therefore comprise four used energy storage cells ESC51, ESC52, ESC53, ESC55 each with for example a 90% SOH and a 50% SOC, one dead energy storage cell E5C54 with a SOH below an threshold SOH level (e.g., 10% SOH), and one new and fully charged energy storage cell ESC56 with a maximum SOH (e.g., 100% SOH) and a maximum SOC (e.g., 100% SOC). Energy storage cell ESC56 was included in the battery as a redundant cell. During operation, the control unit of the battery may identify the dead cell E5C54 by checking whether the estimated SOH of the cell is below a threshold SOH (e.g., 10% SOH).

When the control unit identifies the dead energy storage cell ESC54, it may permanently set the dead cell to the idle mode and may switch the redundant energy storage cell ESC56 to the active mode to compensate the loss of one cell and thus to maintain substantially the same output voltage. Since the redundant energy storage cell E5C56 is a new cell and thus has a much higher SOC than the other four energy storage cells ESC51, ESC52, E5C53, ESC55, the reconfigurable battery is in an unbalanced state. Hence, the reconfigurable battery will undergo a cell balancing process (e.g., the discharging process of an originally unbalanced battery illustrated in Figure 3(b)) during the initial period (e.g., the cell balancing period illustrated in Figures and 6) of the discharging process. As described above, during the cell balancing period and while the battery is discharging, the new energy storage cell with the highest SOC may be maintained in the active mode so as to supply more energy to an external load whereas the mode of the other four energy storage cells ESC51, ESC52, ESC53, ESC55 may be switched in an alternated manner with one energy storage cell being in the idle mode in each discharging state, e.g., ESC51 is in the idle mode in the first discharging state DS1, E5C52 is in the idle mode in second discharging state D52, ESC53 is in the idle mode in the third discharging state DS3, ESC55 is in the idle mode in the fourth discharging state DS4.

By the time all the five energy storage cells reach a substantially equalised SOC, the 10 reconfigurable battery may be regarded as balanced and may enter the stead state operation (as shown in Figure 7).

In many applications where a higher energy capacity and/or a higher battery voltage are desired, for example for powering electrical vehicles, larger-scale batteries formed by series-parallel connection of a plurality of battery cells need to have a balanced operation. The battery balancing method is also applicable for balancing large-scale batteries which may comprise a plurality of battery cells with different SOHs and SOCs and/or a plurality of battery cells of different types, some types of cells being suitable for long-term operation while others being suitable for short-term high-power delivery.

With reference to Figure 11, the reconfigurable battery may comprise four energy storage cells ESC61-ESC64 and four power cells PC61-PC64, each having for example a 90% SOH and a 50% SOC. The energy storage cells ESC61-E5C64 may have a high energy capacity but limited capability to deliver high current in a short period of time. In contrast, the power cells PC61-PC64 may be able to deliver high current for a short period time but have a limited energy capacity. Depending on application, the control unit may switch one type of cells into the active mode while keeping the other type of cells into the idle mode. For example, in cases where a short term heavy load (e.g., during vehicle acceleration) is to be supplied, the control unit may switch all the power cells PC61-PC64 into the active mode while keeping the energy storage cells ESC61-ESC64 in the idle mode, as shown in Figure 12(a). This prevents early aging of the energy storage cells ESC61-ESC64 triggered by overcurrent conditions and therefore extends the total battery lifetime. In cases where long term light loads (e.g., during constant speed driving) are to be supplied, the control unit may switch the energy storage cells ESC61-ESC64 to the active mode and keep or switch the power cells PC61-PC64 to the idle mode. Note that the aforementioned battery balancing method is applicable under the light load operation only or for energy storage cells only.

In some embodiments, rather than supplying the long term light load with only energy storage cells, the reconfigurable battery may be configured in such a way that two energy storage cells (e.g., ESC61, ESC63) and two power cells (e.g., PC61, PC63) are to used together to supply the long term light load. The control unit of the battery may periodically switch the mode of all the energy storage cells such that the energy storage cells are used in an alternated manner, for example, in a first discharging state, energy storage cells ESC61, ESC63 and power cells PC61, PC63 are set to the active mode while in a second discharging state, energy storage cells ESC62, ESC64 and power cells PC62, PC64 are set to the active mode, the first discharging state and the second discharging state alternate continuously.

With reference to Figure 12, the large-scale reconfigurable battery may be built from several battery cell sections BCS connected in series. Each section BCS may comprise one or more battery cells BC and two controllable switches CS. The one or more battery cells BC may be in series-parallel connection and may form a number of battery cell columns and a number of battery cell rows. The number of battery cell rows may determine the total voltage of the battery cell section BCS while the number of battery cell columns may determine the total current of the battery cell section BCS. The total number of battery cells BC may determine the total energy capacity of the battery cell section BCS. The ON/OFF states of the two controllable switches CS may determine whether the associated battery cell section BCS (thus the one or more battery cells BC comprised in the battery cell section BCS) is connected to the electrical circuit of the battery, in the same way as the simple examples shown in Figure 2(a)-2(d). During operation (discharging or charging), some sections may be in the active mode while others may be in the idle mode. As shown in the figure, active sections are depicted in bold lines.

For the purpose of illustrating the operating principle of large-scale reconfigurable batteries, Figure 12 only shows some components of the battery. However, in a fully functioning battery, there may be many other components in addition to those battery cells BC and controllable switches CS. With reference to Figure 13, the packaged large-scale reconfigurable battery LBA may comprise several battery cell sections BCS connected in series, a battery control unit BCU connected to each battery cell section, and other additional components such as for example, voltage sensors VSR, current sensors CSR, temperature sensors TSR, and internal balancing circuits IBC. In each battery cell section BCS, a temperature sensor TSR may be attached to or placed in proximity to each controllable switch CS for monitoring the temperature of each switch. One or more additional temperature sensors TSR may be attached to one or more battery cells BC so as to monitor the cell temperatures. One voltage sensor VSR may be used to monitor the voltage of each cell row and one voltage sensor VSR may be used to monitor the total voltage of the battery cell section BCS. One current sensor CSR may be used to monitor the battery current BC. In different embodiments, depending on application need, different numbers and/or different types of sensors may be used in each battery cell section.

If a battery cell section BCS contains more than one cell in series, an internal cell balancing circuit IBC may be deployed inside this battery cell section BCS to balance for example the SOC of the battery cells BC during operation. Any available cell balancing topology may be used. An example cell balancing method may be implemented by parallelly connecting a controllable resistor (e.g., comprising a controllable switch and a resistor connected in series) to each battery cell BC of a battery cell string or a battery cell column. As such, each battery cell BC can be shunted with the controllable resistor. Hence, when a particular battery cell has too high charge the corresponding controllable resistor can be activated and absorb a certain portion of charge. This cell balancing method is detailed in EP2075893B1, which is incorporated herein for reference. The internal balancing circuit IBC may be controlled by the battery control unit BCU.

The battery control unit BCU may be configured to monitor the operational state of each battery cell section BCS by for example, periodically comparing signals SIG (e.g., switch temperatures, cell temperatures, row voltage, total voltage, ) received from all the sensors of each battery cell section BCS with certain thresholds or ranges. If the operational state of any battery cell section BCS is not meeting a certain criterion (e.g., the SOC of the battery cell section BCS is lower than a certain threshold), the battery control unit BCU may change the mode of the corresponding battery cell section BCS (e.g., switch it to the idle mode when its SOC is too low). The battery control unit BCU may also perform circuit protection functions. For example, when the battery current to exceeds a maximum current threshold, the battery control unit BCU may switch all the battery cell sections BCS to the idle mode such that the battery electric circuit is disconnected, thereby avoiding overcurrent damage of battery cells BC. Also, when one or more cell temperatures of a battery cell section BCS exceed a maximum temperature threshold or drop below a minimum temperature threshold, the battery control unit BCU may switch the corresponding battery cell section BCS to the idle mode. Furthermore, when the temperature of any controllable switch CS is above a maximum switch temperature, the battery control unit BCU may switch the mode of the corresponding battery cell sections BCS e.g., from the active mode to the idle mode.

In different embodiments, the battery cell sections BCS of the battery LBA shown in Figure 13 may be individually packaged rather than being enclosed together within one package (the battery package). This may reduce the mutual impact between battery cell sections and may improve the environmental resistance of the battery. As a centralised controller and being physically separate from other battery cell sections BCS, the battery control unit BCU adds complexity to the service and maintenance of the battery LBA. This is because it requires not only additional field replaceable units (control units) apart from packaged battery cell sections BCS, but also a considerable wiring effort. To improve serviceability of a large-scale reconfigurable battery LBA, a complete modular design is desirable.

With reference to Figure 14, the multi-module reconfigurable battery MBA may comprise one or more battery modules BM connected in series. In some embodiments, each battery module BM may have exactly the same interchangeable hardware and software. In some embodiments, each battery module BM may comprise a battery control unit BCU equipped with battery control software (e.g., the above described control algorithm), so any battery module BM in the battery MBA can manage the whole battery. In some embodiments, a hardware arbitration may be implemented to prevent possible logical conflict when two or more masters may attempt to control the same battery at the same time. In some embodiments, each of the battery module BM may further comprise an upstream interface USI and a downstream interface DSI. In some embodiments, all of the battery modules BM may be interconnected via these two to interfaces. In some embodiments, only one battery module BM may be used as the master module of the battery MBA and all the other modules of the battery MBA may be used as slave modules. When a battery module BM is selected to be the master module, its battery control unit BCU may be activated and be used to control the slave modules. The master module may communicate with the slave modules through its downstream interface DS! while each of the slave modules may communicate with the master module with its upstream interface USI. For each of the slave modules, its battery control unit BCU may be deactivated or inhibited.

In some embodiments, each battery module BM may comprise one battery cell section BCS which may comprise two controllable switches CS and one or more battery cells BC and which may be configured in the same manner as any of the battery cell sections BCS shown in Figure 13. Voltage sensors VSR may be used to measure the voltage of each battery cell row as well as the voltage of each battery cell column. One current sensor CSR may be used to measure the battery current. Temperature sensors TSR may be used to measure the temperatures of the two controllable switches CS and one or more battery cells BC. The measurements of voltages, currents and temperatures may be carried out in a periodical manner. The interval between two consecutive measurements may be predefined and/or adjustable. In some embodiments, each battery module BM may comprise a module control unit MCU which may be configured to receive measurement data from all the sensors, process and evaluate the data and subsequently command relevant components based on the evaluation of the measurement data. In some embodiments, each battery module may be allocated with a unique identity (ID) number which may be used by the battery control unit of the master module for the purpose of controlling all the battery modules. In some embodiments, each battery module BM may comprise a single type of battery cells BC, e.g., energy storage cells or power cells; whereas different battery modules may comprise different types of battery cells BC.

Since all the battery modules BM are interchangeable and any battery module BM can be configured to be the master module, the modular design shown in Figure 14 thus obviates the need for additional field serviceable units (e.g., separate control units) and improves the battery's serviceability and maintainability (e.g., reduces the wiring effort).

Once all the battery modules BM are connected, the battery control unit BCU of the first battery module BM in the module string is activated and used as the master module. The battery control unit BCU communicates (e.g., receiving status-related data from each slave module, sending commands to each slave module) with all the slave modules via the downstream interface DS! of the master module. Each of the slave modules communicates (e.g., receiving commands from the battery control unit BCU of the master module) with the master module via its upstream interface USI.

In some embodiments, the multi-module reconfigurable battery MBA shown in Figure 14 may be configured to stepwise regulate or adjust the battery voltage by dynamically changing the number of active modules. As mentioned above, the number of active modules determines the battery voltage while a total number of battery cells determines the total energy capacity of the battery MBA. For example, if the battery contains 30 battery modules BM and 20 of them are set to the active mode, then each active module contributes about 5% of the total battery voltage. The battery control unit BCU of the master module can stepwise regulate and adjust battery voltage by real-time change in the number of active modules. Increasing the number of active modules from 20 to 21 will add 5% to the total battery voltage.

Since the battery voltage declines during the nominal discharging process, the stepwise voltage regulation is thus a useful function for compensating the voltage drop during operation and maintaining substantially the same battery voltage. Note that, the battery voltage can also decline when one or more operating conditions vary, for example, when the operating temperature drops or when the external load is increased. To compensate for undesirable voltage drop, the battery control unit BCU of the master module may first identify the voltage drop (e.g., by periodically comparing the measured battery voltage to a target/reference battery voltage) and whenever the voltage drop exceeds a threshold voltage, change the number of active modules e.g., from 20 to 21 (e.g., by switching one idle module to the active mode), so as to compensate for the voltage decrease.

In some embodiments, in addition to the battery voltage regulation function, the multi-module reconfigurable battery MBA may be configured to receive particular voltage requests from a load controller, and change the number of active modules and corresponding battery voltage to meet a targeted load operation. For example, when an electric vehicle is in a low speed driving state, the battery control unit BCU of the master module may reduce the number of active modules to supply a low battery voltage. In contrast, when an electric vehicle is in a high speed driving state, the battery control unit of the master module may increase the number of active modules in order to boost the battery voltage.

In different embodiments, the multi-module reconfigurable battery MBA may be configured to allow a user to change the total number of battery modules BM in the battery MBA while maintaining substantially the same battery voltage. In the meantime, adding or removing battery modules BM in the battery changes the total battery energy capacity. For example, in case of the battery containing 30 battery modules BM, 20 of which are set to the active mode, adding 10 battery modules BM into the same battery MBA will increase the battery energy capacity by 33%. A 33% increase in battery energy capacity may increase vehicle mileage per one charge by 33%, for example. In such a case, the number of active modules will remain the same, consequently, battery voltage will remain the same, which allows the battery to be used on the existing load or vehicle without changing on-board electrical equipment.

It will be appreciated that the above described embodiments are given by way of example only, and that various modifications may be made to the embodiments without departing from the scope of the invention as defined in the appended claims.

Claims

Claims 1. A reconfigurable battery, comprising: at least two battery cell sections connected in series, each battery cell section comprising two controllable switches and at least one battery cell; wherein in each battery cell section, the two controllable switches are operable to either set the battery cell section to an active mode such that the at least one battery cell is connected to the battery's electrical circuit, or set the battery cell section to an idle mode such that the at least one battery cell is bypassed from the battery's electrical circuit; and control means configured to monitor and control each of the at least two battery cell sections; wherein whenever a switching condition is fulfilled for any of the at least two battery cell sections, the control means is operable to control the controllable switches of each of that battery cell section such that the mode of that battery cell section is 15 changed.
2. A reconfigurable battery as claimed in claim 1, wherein the switching condition for each of the at least two battery cell sections is based on one or more of: a state of charge (SOC) of the at least one battery cell; a state of health (SOH) of the at least one battery cell; a temperature of the at least one battery cell; a temperature of each of the two controllable switches; a time interval; or a battery cell type.
3. A reconfigurable battery as claimed in claim 1 or claim 2, wherein the control means is operable to change the mode of at least two battery cell sections in order to maintain substantially the same battery voltage.
4. A reconfigurable battery as claimed in claim 2 or claim 3 when depending on claim 2, wherein the control means is operable to rank each of the at least two battery cell sections in accordance with its SOC.
5. A reconfigurable battery as claimed in claim 4, wherein during a discharging process, the control means is operable to identify, based on the SOC ranking of the at least two battery cell sections, the active battery cell section with the lowest SOC among all active battery cell sections, and the idle battery cell section with the highest SOC among all idle battery cell sections.
6. A reconfigurable battery as claimed in claim 5, wherein the control means is operable to further change the active battery cell section with the lowest SOC to the idle mode and the idle battery cell section with the highest SOC to the active mode when the SOC of the active battery cell section is no more than that of the idle battery cell section.
7. A reconfigurable battery as claimed in any of claims 4 to 6, wherein during a charging process, the control means is operable to identify, based on the SOC ranking of the at least two battery cell sections, the idle battery cell section with the lowest SOC among all idle battery cell sections, and the active battery cell section with the highest SOC among all active cell sections.
8. A reconfigurable battery as claimed in claim 7, wherein the control means is operable to further change the idle battery cell section with the lowest SOC to the active mode and the active battery cell section with the highest SOC to the idle mode when the SOC of the idle battery cell section is no more than that of the active battery cell section.
9. A reconfigurable battery as claimed in any of claims 4 to 8, wherein during a discharging process, the control means is operable to identify the active battery cell section with the lowest voltage and the idle battery cell section with the highest voltage.
10. A reconfigurable battery as claimed in claim 9, wherein the control means is operable to further change the active battery cell section with the lowest voltage to the idle mode and the idle battery cell section with the highest voltage to the active mode.
11. A reconfigurable battery as claimed in any of claims 2 to 10, wherein the control means is operable to permanently set a battery cell section to the idle mode when the SOH of the at least one battery cell of the battery cell section is below a threshold SOH.
12. A reconfigurable battery as claimed in any of claims 2 to 11, wherein the control means is operable to change the mode of any of at least two battery cell sections when the temperature of the at least one battery cell of the battery cell section is either above a maximum cell temperature or below a minimum cell temperature.
13. A reconfigurable battery as claimed in any of claims 2 to 12, wherein the control means is operable to change the mode of any of at least two battery cell sections when the temperature of any of the two controllable switches is above a maximum switch temperature.
14. A reconfigurable battery as claimed in any of claims 2 to 13, wherein the control means is operable to change the mode of one or more of at least two battery cell sections at time intervals.
15. A reconfigurable battery as claimed in any of claims 2 to 14, wherein in any of the at least two battery cell sections, the at least one battery cell is of a single cell type.
16. A reconfigurable battery as claimed in claim 15, wherein the at least two battery cell sections comprise at least two different cell types.
17. A reconfigurable battery as claimed in any of claims 16, wherein the control means is operable to set one or more of the at least two battery cell sections of a specific cell type to the active mode and any other battery cell section of a different cell type to the idle mode where the specific battery cell type is desired for a certain application.
18. A reconfigurable battery as claimed in claim 17, wherein the at least two battery cell sections comprise one or more battery cell sections each having one or more energy storage cells and one or more battery cell sections each having one or more power cells, further wherein the control means is operable to set some or all of the one or more battery cell sections each having one or more power cells to the active mode where a short term heavy load is to be supplied.
19. A reconfigurable battery as claimed in any preceding claim, wherein the two controllable switches of each of the least two battery cell sections are connected in series and comprise a first switch terminal, a second switch terminal and a common switch terminal wherein each battery cell section is configured such that the first switch terminal is connected to a positive terminal of the at least one battery cell, the second switch terminal is connected to a negative terminal of the at least one battery cell, and the common switch terminal is connected to another battery cell section.
20. A reconfigurable battery as claimed in claim 19, wherein the control means is operable to change a switch state of one or both of the two controllable switches in order to change the mode of the at least one battery cell of that battery cell section.
21. A reconfigurable battery as claimed in any preceding claim, wherein the at least one battery cell comprises two or more battery cells which are connected in series-parallel connection.
22. A reconfigurable battery as claimed in claim 18, wherein each of the at least two battery cell sections further comprises an internal balancing circuit configured to balance the SOC of each of the at least one battery cell during battery's operation.
23. A reconfigurable battery as claimed in any preceding claim, being configured in such a modular manner that each of the at least two battery cell sections is enclosed in a battery module and all the battery modules are connected in series, each battery module comprising: battery control means and module control means; an upstream interface; and a downstream interface.
24. A reconfigurable battery as claimed in claim 23, wherein the battery control means, when activated, is operable to communicate with other battery modules via the downstream interface of the same battery module and to decide on the mode of each battery module which is in effect the mode of the battery cell section of the battery module.
25. A reconfigurable battery as claimed in any of claims 23 or 24, wherein the module control means of each battery module is operable to communicate with the battery control unit and to control the mode of the battery cell section by controlling the two controllable switches.
26. A reconfigurable battery as claimed in any of claims 23 to 25, being configured to activate the battery control means when the corresponding battery module is selected 10 be the only master module of the battery.
27. A reconfigurable battery as claimed in claim 26, being configured to inhibit the battery control means of each slave battery module.
28. A reconfigurable battery as claimed in claim 27, wherein the module control means of each slave battery module is operable to communicate with the battery control means of the master module via the upstream interface of the battery module.
29. A reconfigurable battery as claimed in any of claims 23 to 28, wherein the battery control means is operable to regulate an output battery voltage by calculating a difference voltage between the output battery voltage and a reference battery voltage and change the mode of one or more of the battery modules whenever the difference voltage is above a threshold voltage.
30. A method for operating a reconfigurable battery comprising: at least two battery cell sections connected in series, each battery cell section comprising two controllable switches and at least one battery cell; wherein in each battery cell section, the two controllable switches are operable to either set the battery cell section to an active mode such that the at least one battery cell is connected to the battery's electrical circuit, or set the battery cell section to an idle mode such that the at least one battery cell is bypassed from the battery's electrical circuit; and control means configured to monitor and control each of the at least two battery cell sections; the method comprising: monitoring each of the at least two battery cell sections; and changing the mode of a battery cell section whenever a switching condition is fulfilled for that battery cell section.
31. A method as claimed in claim 30, wherein the switching condition for each of the at least two battery cell sections is based on one or more of: a state of charge (SOC) of the at least one battery cell; a state of health (SOH) of the at least one battery cell; a temperature of the at least one battery cell; a temperature of each of the two controllable switches; a time interval; or a battery cell type.