GB2545700A

GB2545700A - Configurable battery module and system

Info

Publication number: GB2545700A
Application number: GB1522658.2A
Authority: GB
Inventors: William Dale Bishop Peter
Original assignee: PowerOasis Ltd
Current assignee: PowerOasis Ltd
Priority date: 2015-12-22
Filing date: 2015-12-22
Publication date: 2017-06-28
Also published as: GB201522658D0

Abstract

A configurable battery module 10 and a power supply system incorporating such a module are disclosed. The configurable battery module 10 is operable to provide at least one of a plurality of output voltages and a plurality of capacities. To achieve this, the configurable battery module 10 comprises two terminals 12, 14, a plurality of cells C1-C4, switching circuitry 20 for selectively connecting at least a subset of the plurality of cells in at least one of series and parallel between the two terminals, and a controller, which may be in the form of a microprocessor 35, operable to select at least one of the output voltage and the capacity and to configure the battery module by controlling the switching circuitry to connect the cells so as to provide the at least one of the selected output voltage and the capacity. A sensor 30 may also be used alongside the controller 35 and switches 20. The battery module 10 may be associated with a charging circuit and/or load circuit.

Description

CONFIGURABLE BATTERY MODULE AND SYSTEM

FIELD OF THE TNVENTTON

Aspects and embodiments relate to a configurable battery module removably insertable into a power supply system and a power supply system including such a configurable battery module.

BACKGROUND

Batteries formed of chemical cells can provide electrical energy to devices. They may be used as a backup energy supply when, for example, a grid or generator power supply is unavailable. For example they may be used to supply backup power for remote locations such as mobile telephone base stations which maybe powered by a power source such as solar or wind that may not be continuously available. Generally when such a power source is required the voltage and capacity required is assessed and suitable battery modules providing such voltage and capacity are installed. This requires many different battery modules to be manufactured and stocked.

Furthermore, there maybe instances where the required capacity changes and this renders the installed battery sub-optimal.

Aspects and embodiments seek to address at least some of the issues outlined above. SUMMARY A first aspect of the present invention provides a configurable battery module operable to provide at least one of a plurality of output voltages and a plurality of capacities, said configurable battery module comprising: two terminals; a plurality of cells; switching circuitry for selectively connecting at least a subset of said plurality of cells in at least one of series and parallel between said two terminals; and a controller operable to select said at least one of said output voltage and said capacity and to configure said battery module by controlling said switching circuitry to connect said cells so as to provide said at least one of said selected output voltage and said capacity.

The first aspect recognises that there are significant overheads associated with providing battery modules with different characteristics for different purposes and that the provision of a more universal battery module applicable to many situations would be desirable. It also recognises that many battery modules are formed from a plurality of individual cells connected together and addresses the issues associated with multiple battery module manufacture and supply by providing interconnections between the cells that are dynamically controllable as opposed to static, thereby providing modules where the cells are connected in different parallel and/or series configurations. In this way the voltage and/or capacity provided by such a battery module can be selected in a controllable manner by using switching circuitry to provide series and/or parallel connections between the cells in order to provide the desired voltage and/or capacity.

In this way a battery module is designed so that it can be configured to provide different characteristics depending on the circumstances. Furthermore, as the cells within the battery module age or develop faults, then as the configuration of the battery module is controllable, it may be changed to compensate for this.

Thus, a battery module that is suitable for more applications and is thus, more universally applicable is provided. Such a battery module has multiple cells interconnected by controllable switching circuitry such that the interconnections between the cells are controlled to provide selected capacities and/or voltages, enabling the battery module to be suitable for more applications and in this way reducing manufacturing and stocking costs. The configurability provides additional advantages of allowing a user with one battery for example an electric bike battery to use it in two separate devices with different voltage requirements by moving the battery between devices.

Furthermore, in some applications such as the supply of a backup power system to a wireless telecommunication base station, the voltage level required may differ with the type of base station, some being configured to operate with a supply of 24V for example and others with a supply of 48V. Having a configurable battery module which can be configured to supply either voltage allows a single battery module to be used as a replacement module in any of the base stations.

Although in many cases the cells may all be of the same type, in some cases, a configurable hybrid battery is provided that comprises a battery module formed from cells having at least two different battery cell chemistries. These can be interconnected by the controllable switches in the same way that cells with the same chemistry can be. One advantage of having a hybrid battery module with cells having different cell chemistries is that cells with different properties are available for selection by the controller as required.

The controller may be a microprocessor configured to respond to input signals to transmit control signals to switching circuitry. However, in its simplest form the “controller” simply responds to a mechanical switch which is set by a user to set the switching circuitry to interconnect the cells to output the selected voltage level. In this case the controller is simply switching circuitry which is controlled by the mechanical switch to align the cells in the required configuration dependent on the position of the mechanical switch. In some embodiments the mechanical switch may be set by a user, while in others there may be an interlocking device on the battery module holder within the system that it is used in, perhaps a backup power supply system, the interlocking device acting to automatically set the switch to the required value for that system as the battery module is loaded into position.

In some embodiments, said configurable battery module further comprises: a sensor operable to detect at least one of: a characteristic of said battery module and at least one circuit to which said battery module is connected; wherein said controller is operable to select said at least one of said output voltage and said capacity in dependence upon an output of said sensor

The provision of a sensor within the battery module allows it to detect characteristics of the system to which it is connected or of itself and this allows the configuration to be self-controlled so that the battery module may sense the requirements of the circuit to which it is connected and from this information may control the switching circuitry to configure itself to make its output suitable for that system. The sensor may also be configured to detect changes or faults within the battery module itself and this may allow the battery to reconfigure itself to respond to situations where the configuration of the battery is no longer optimal.

Such a self-configurable battery module has the advantage that it can be used in the same way as a conventional battery module in that it can simply be inserted into a system, whereupon the sensor can sense the requirements of the system, and the controller control the switching circuitry to connect the cells together in an appropriate way.

The circuit to which it is connected and whose characteristics are sensed may be a circuit that the battery module is supplying current to and/or it maybe a charging circuit. In either case the battery module is such that the sensor can detect a characteristic, such as the voltage level of the circuit, and the controller can configure the cells within the battery module appropriately, allowing for the battery to be used in a number of different scenarios. In this regard, although in many systems the battery module will be configured to supply a certain voltage required by the system it is powering and the charging circuitry will be associated with that system and therefore be configured to charge batteries within that system with that same voltage, in some systems the charging circuitry may be remote from the system being powered. Where the battery module comprises a sensor, switching circuitry and a controller then it can determine the charging voltage of any charging circuitry in the same way that it senses the voltage of the circuit that it is powering and provided that the voltage is one of the plurality of output voltages that the battery module can be configured to provide, the controller can control the switching circuitry to match the voltage level of the charging circuitry and in this way charging circuitry of many different specifications can be used to charge the battery module.

Although the characteristic can be a number of things, in some embodiments, said characteristic of said circuit comprises a voltage level, said controller being operable to control said switching circuitry in response to said detected voltage level.

The voltage supplied by the battery should be appropriate to the circuit/system to which the battery is connected. In this regard it should be noted that although the cells may be interconnected to output a certain nominal voltage the actual voltage output at any one time depends on the state of charge of the cells within the battery module, so in effect the controller determines the most likely configuration of the cells to provide the detected voltage level. A battery that is added to a system, perhaps as a back-up power solution, may be connected to the voltage rails of the circuit being powered and with the appropriate sensor can detect the voltage on these rails and a controller can then control the switching circuitry to connect the cells in an appropriate way to output the required voltage. Similarly where the circuit is a charging circuit, the sensor can detect the voltage supplied by the charging circuit and control the switching circuitry to match that voltage. In some embodiments the charging currents are also sensed as an additional check that the correct voltage determination has been made. Furthermore, in some embodiments the voltage may be monitored again during operation as a charger’s voltage may fall once current is drawn and this acts as a further check, and allows for reconfiguration where the initial determination was not accurate.

In some embodiments, said controller is operable to select from said plurality of output voltages an output voltage closest to said detected voltage level and to control said switching circuitry such that said plurality of cells are connected to output said selected output voltage.

Given that the battery module is made up of multiple cells each configured to provide a certain voltage, there are certain connections that can be made between the cells to provide a number of possible output voltages. On detection of the voltage level of the system to which the battery is connected, the switching circuitry may be controlled to output the one of these output voltage levels that is closest to the detected voltage level.

In some embodiments, said characteristic of said circuit comprises an output current, said controller being operable to control said switching circuitry in response to said detected current to configure said battery module to provide a selected capacity.

The interconnections of the cells can be used not only to control the voltage output by the battery module but also to control the capacity of the battery module. In this regard several cells connected in parallel will provide a higher capacity than a single cell would. Thus, if an indication of a current or load required can be determined this can be used to control the capacity of the battery module by controlling the switching circuitry. The capacity required may be determined when the battery module is added to the system, and it may additionally in some embodiments be determined periodically thereafter, such that as a system’s requirements change then so too can the capacity of the battery supplying the system. In this way cells of the battery module can be periodically switched out of the system thereby increasing their lifetime. Careful control of the switching can allow each cell to be utilised for similar amounts of time.

In some cases rather than judging their remaining capacity from the time that they have actively been supplying power, the sensor or additional sensors may be used to determine the current output from the cells or from each cell, such that as a capacity of a cell falls it can be switched out of the system and replaced with another cell. Such a battery module with in effect over capacity may be used in systems that require high availability, lifetime and reliability. In some situations it may be advantageous to keep some capacity in reserve, and to allow the controller to reconfigure the battery module to switch to use the reserve cells when required. For example, where a configurable battery is used in an electric bike pack, there could be a reserve switch to indicate to the controller to switch to reserve cells when the main bulk of the cells of the battery module have discharged, allowing a user to reach home. This reserve switch could be one operated by a user or it could be one that the controller controls in response to the sensor detecting the currently used cells having discharged to a certain low level. In the latter embodiment the battery module may have an output for providing an indication that it has switched to its reserve capacity.

In some embodiments, said characteristic further comprises at least one of a current and a voltage output by at least one of said cells of said battery module, said controller being operable to control said switching circuitry in response to said detected at least one of said current and said voltage.

As noted above in some embodiments, the capacity of the battery module can be changed by switching cells into and out of the circuit where the load requirements change. These changes in load requirements might be detected by changes in current supplied by the battery module. Such a system can also be used to switch cells out when their charge levels starts to fall as they age or fail, thereby providing a battery module with a longer lifetime and higher reliability.

In some embodiments the switching circuitry may comprise an isolating switch to isolate said plurality of cells and switching circuitry from said one of said terminals and said controller may be configured in response to detecting a current output by said battery module falling below a predetermined level to isolate said cells from said terminal. In this way the entire battery module may be isolated from the system. The isolation of a module from a power supply system may cause its own problems particularly if it is arranged in series with other modules, thus, the isolation of individual cells, such that the module is still within the system may be preferable.

In some embodiments, said characteristic comprises at least one of an output from a motor speed controller within said circuit; an output from a load controller; an output from a control bus controlling components powered by said battery module, an output from further battery modules forming part of a same power supply system, and an environmental characteristic.

In addition to, or as an alternative to the characteristic of the circuit being a voltage and/or current level, the characteristic(s) sensed may be other features of the circuit which affect its power requirements. Thus, where the battery module is powering a drive motor for example, then a speed controller may indicate a required capacity, similarly a load controller may also provide such information. In a complex system, the status of various components may affect both the capacity and the voltage required from the battery and thus, signals from a control bus which might provide such indications can be used in the configuration of the battery module. Where the battery module forms backup power for a remote base station for example, then the characteristic may be characteristics of other battery modules forming the power supply system. Indications that one of the battery modules is failing for example or requires charging may cause the controller to configure the battery module to increase the capacity supplied by that battery module. Where the characteristic is an environmental characteristic, such as time or temperature, then either of these may indicate when the backup power supply is likely to be required. In a system that uses solar energy as the main power supply for example, then the time and/or temperature maybe an indication of when this power may not be available. Alternatively and/or additionally the time may be an indication of when the base station is likely to be operating at a high capacity and additional power may be required.

In some embodiments, during initialisation of said battery module, in response to said sensor detecting said circuit to be unpowered, said controller is operable to control said switching circuitry to configure said battery module initially to provide a lowest one of said plurality of output voltages, and to determine from said sensor if a current output by said battery module to said circuit is greater than a predetermined level and if not, to reconfigure said switching circuitry to progress through said plurality of output voltages until said sensor detects said current output by said battery module to said circuit to be greater than said predetermined level.

As noted previously, the battery module can be self-configurable and can configure itself by detecting properties of the circuit to which it is connected. This works well where the battery module is only one part of the power supply system such that on connection of the battery module to the circuit the circuit is being powered by other means. Where the battery module is connected to an unpowered or dormant system then self-configuration is more of a challenge. This is addressed in embodiments, by configuring the battery module to progressively increase the output voltage through the different voltage levels that it is designed to supply. In this way potential damage to the system being powered by supplying a voltage that is too high can be mitigated. The appropriate voltage may be detected by the sensor which senses the battery module providing a load when the output voltage reaches a certain level as the circuit(s) being driven switch on. In this regard many circuits are controlled by electronic components such as switches that require certain voltage levels to function. Once that voltage level is reached the components will switch on and a current will be drawn.

In some embodiments, said battery module comprises an input operable to receive a control signal; said controller being operable to select said at least one of said output voltage and said capacity in dependence upon said control signal.

An alternative and/or additional way of controlling the configuration of the battery module is to do so in response to an input control signal. This is an alternative way of providing initialisation of an unpowered system, and is also appropriate for battery modules without sensors.

The externally generated control signal may have a number of forms, in some embodiments, said control signal comprises at least one of: an initialisation control signal; a control signal received from a further battery module arranged to power a same circuit as said battery module, and a power supply supervisory system controller for controlling a plurality of battery modules powering a same circuit.

As noted previously, in some cases a battery module may be added to a system which is currently unpowered such that the sensor does not detect a characteristic of the power supply system making self-configuration difficult. This can be addressed by providing the battery module with an input which can receive an initialisation signal indicating a characteristic of the system allowing the battery module to configure itself appropriately. In its simplest form the initialisation signal may be triggered by a switch on the side of the battery allowing a user to select the desired voltage. Alternatively the signal could be provided automatically via a “handshake” with the equipment it is being connected to. Additional control signals that the configurable battery module may be configured to respond to may be ones generated by other parts of the power supply system of which the battery module is a part. Thus, in some cases the power supply system may comprise a number of battery modules which are controlled by a central supervisory system which centrally controls the charging and loading of the battery modules that form the power supply. Having a configurable battery module in such a system allows for greater granularity in the control with variations in capacity requirements for example being able to be catered for at both a system and an individual battery module level. In other cases the control signal may be generated by another battery module in the system. In this regard, some form of central control of the power system may be provided at the battery module level, where a controller in one battery module acts as a master to the power supply system and transmits control signals to control other battery module’s function and configurations.

In some embodiments, said controller is operable to generate a control signal to control at least one further battery module arranged to power a same circuit as said configurable battery module, said configurable battery module further comprising an output for outputting said control signal to said at least one further battery module.

As noted above, where the battery module is within a power supply system comprising a number of battery modules, then there maybe some sort of central control of the battery modules as a whole. In this regard individual control at the battery module level may allow a more universal battery module to be used and may help preserve that battery module’s lifetime, however, unilateral action taken at one battery module to change its capacity or shut itself down, might prove detrimental to operation of a power supply in which that battery module is operating. For example, if one battery module connected in series with other battery modules provided within a power supply shuts itself down as an act of self-preservation, the whole string of battery modules within the power supply may be incapacitated. Thus, in some cases additional more central control can be advantageous where in addition to controlling the configuration of itself a “master” battery module can generate and transmit control signals to other battery modules. These signals may cause them to switch in and out of the circuit and receive charge as required, they may also in some cases indicate a preferred configuration for the modules, such that their capacity for example can be changed as required.

In some embodiments, the battery module further comprises an isolating switch operable to selectively isolate said plurality of cells and said switching circuitry from one of said terminals.

An isolating switch that can isolate the plurality of cells from a terminal may be advantageous in many circumstances. It allows the cells to be isolated from the circuit when no current is required, and it may also be convenient when the battery module is initially applied to a system. In such a self-configurable battery module it allows the sensor to sense the circuit and the controller to configure the battery module before the cells are connected to the circuit, thereby allowing the battery module to supply an appropriate voltage and/or capacity on connection to the system. It should be noted that conventional battery packs may comprise an isolating switch for isolating the cells from the terminals when there is no load required and the battery is in sleep mode. Applying a voltage to the battery may wake it up and the isolating switch will close. In embodiments the controller will control the isolating switch not to close until the battery has configured itself.

In some embodiments, said controller is configured to control said isolating switch to isolate said plurality of cells and switching circuitry from said one of said terminals in response to detecting a current output by said battery module falling below a predetermined level.

Such an isolating switch can also be used in conjunction with the controller to protect a battery module whose capacity is falling below a certain threshold value, avoiding its use when in a very low charged state which might lead to it or other units in the system being damaged.

In some embodiments, said controller is operable following configuring said battery module to control said isolating switch such that said plurality of cells and said switching circuitry are connected to said one of said terminals.

As noted previously the isolating switch is a convenient way of isolating the cells from the circuit prior to configuration. Once configuration is complete the controller can control the isolating switch to connect the cells to the terminals such that the battery module becomes operational.

In some embodiments, said plurality of cells are connected together in a plurality of banks, each bank providing a predetermined nominal voltage level, said controller being operable to control said switching circuitry to connect at least a subset of said banks in parallel in order to provide an increased capacity and to control said switching circuitry to connect at least a subset of said banks in series in order to provide a higher output voltage.

Although in some cases the switching circuitry may be controllable at an individual cell level, in some embodiments, cells are arranged in banks, so that a plurality of cells form a single bank and control of the configuration can be performed at the bank level. In such a case, cells within each bank may be hard-wired to provide a predetermined voltage and the controller controls the switching at the bank level, so that banks are connected in parallel or series to the terminals and/or are isolated from them depending on the voltage level and/or capacity required. In this way an output voltage that is a multiple of the voltages output by the individual banks can be provided by controlling the switching circuitry between banks of cells. In other embodiments there is a combination of switching cells both within the banks and between banks, such that individual banks can be configured to output different voltages and have different capacities and different combinations of the banks can be used.

Although the cells and banks can be arranged to provide a number of different voltages and capacities, in some embodiments said plurality of nominal output voltages comprises 12V, 24V and 48V. It should be noted that these are nominal voltages, in that the actual voltage output will vary over a range around these nominal values, due to variations in charge and discharge currents and state of charge levels.

Many systems are designed to operate at certain predetermined voltages which for legacy reasons may be a factor of 2V. Thus, arranging the banks to provide 4 or 12V outputs and the module to provide multiples of this makes the battery module suitable for use in many conventional systems.

In some embodiments, said controller is operable in response to said sensor indicating said at least one of a current or a voltage output by said at least one cell has fallen below a predetermined level to determine whether a configuration of said plurality of cells not including said at least one cell is possible to provide said selected output voltage and where so, to control said switching circuitry to connect said cells to output said selected voltage and where not, to control said isolating switch to isolate said plurality of cells from said one of said terminals .

The sensor may be configured to detect the current and/or voltage output by the cells and this can be used to detect a cell losing its charge or failing, which can be compensated for by reconfiguring the battery module where it has sufficient cells to output the required voltage without the discharged/failing cell(s) being included in the power circuit. However, where many cells have become discharged to a certain level it may be that reconfiguration to compensate for this and still output the required voltage is not possible. In this case, in embodiments the controller is configured to respond to this by isolating the battery module from the circuit.

In some embodiments, said controller is operable in response to said sensor detecting at least one of a voltage or current output by said plurality of cells falling below a predetermined level to generate and output a low power indicator signal prior to controlling said isolating switch.

Where the battery module is in a power supply where sudden loss of power may be particularly disadvantageous, for example where it is providing power for a base station then the output of a warning signal prior to isolating the power source from the circuit maybe advantageous.

In some embodiments, said configurable battery module is housed in a housing with a standard form factor.

Some conventional battery modules have a standard form factor, such that any battery module manufactured with this form factor can be used interchangeably. The standard form factor will dictate the volume, shape and terminal location for the battery module allowing it to fit into a system designed to be powered by a battery with such a form factor. The self-configurable battery can be made with a standard form factor and in this way can be simply slotted into systems designed for such battery modules, the configurable nature of the battery module allowing it to output the appropriate voltage. It should be noted that the form factor may be one for a lead acid battery, the configurable nature of the battery allowing it to be used in such a system.

In this regard there may be systems currently powered by an array of lead acid battery modules and being able to replace them with battery modules according to embodiments as they age and/or fail can be advantageous. Lead acid battery modules are particularly heavy and the ability to use lighter modules according to embodiments can make their replacement an easier and more convenient operation.

In this regard the cells within the battery modules may comprise a number of different chemistries, but in some embodiments they comprise lithium ion cells.

The costs of manufacturing lithium ion cells are decreasing. These cells are also lightweight and have a long lifetime if their operation and charging are carefully controlled. Thus, they provide a reliable and cost effective cell in a module that has a controller that controls the configuration use of these cells.

Although the switching circuitry may be made up of many different switching circuits, such as transistors, solid state switches or mechanical relays in some embodiments, said switching circuitry comprises a plurality of FETs (Field Effect Transistors). These are cheap, robust and easily controllable devices and as such suitable for interconnecting the individual cells and/or banks.

In some embodiments, where said at least one of said selected output voltage and capacity are such that a subset of said plurality of cells are connected to said terminals at any one time, said controller is further operable to periodically switch between subsets of cells that are connected to said terminals.

As noted previously, in some cases it may be advantageous for the cells to share the load and thus, the ability to periodically switch between cells may increase flexibility and improve the lifetime of a battery module.

In some embodiments, said sensor is operable to determine a voltage output by said plurality of interconnected cells following control of said switching circuitry and where it is substantially less than a voltage level expected by said controller said controller is operable to control said switching circuitry to connect said cells to provide a higher voltage level.

In some cases the sensor may be configured to sense the voltage output by the cells and to determine when it is significantly lower than the voltage desired and indeed expected. This may be done following configuration and prior to connection to the system, or it may be done during operation. In such a case, where the battery module is not currently configured with all cells in series, the controller can reconfigure the battery module to connect more cells in series in order that the battery module outputs a higher voltage, the configuration being based on the sensed not the expected voltage from the configuration. The controller can then later reconfigure the battery once the cells have been charged. This can help avoid a battery module being damaged where it is not charged to the same amount as other battery modules in a cluster, perhaps having been added to the system in a substantially uncharged state. This may also be used during operation where the battery cells are depleted and the output voltage level falling. The ability to reconfigure could allow additional charge to be extracted from the battery module. A significantly lower than expected voltage may be one that is say 2V less than the system voltage. The actual voltage level will depend to some extent on the system and battery module. Thus, in some cases the voltage level difference that is viewed as significant may be that of a single cell and where the difference is this or greater than this, then the battery module may be reconfigured to compensate for the difference. A second aspect of the present invention provides a power supply system comprising: a power supply system comprising at least one battery module according to a first aspect; and at least one further battery module.

In some cases the further battery module may be a configurable battery module according to an embodiment or it maybe a conventional battery module.

In some embodiments, said power supply system further comprises at least one circuit electrically connected to said battery module.

In some embodiments, said at least one circuit comprises a system load.

In some embodiments, said at least one circuit comprises a charging circuit for supplying current to said at least one battery module.

In some embodiments, said power supply system further comprises a power management system for controlling operation of said plurality of battery modules.

In some embodiments, said power supply system comprises a backup power supply system for a base station.

Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

Figure 1 shows a battery unit according to an embodiment;

Figures 2a - 2e shows the battery unit of Figure l configured to supply different voltage levels and have different capacities according to various embodiments;

Figure 3 shows a battery unit according to a further embodiment;

Figures 4a and 4b show a power supply system to which a battery unit according to an embodiment may be added;

Figure 5 shows a battery cluster with replaceable battery modules with a standard form factor;

Figure 6 shows a battery cluster with a plurality of configurable battery modules configured to communicate with each other;

Figure 7 schematically shows a configurable battery module powering an electric bike motor according to an embodiment; and

Figure 8 schematically shows a configurable battery module forming part of a backup power supply for a remote base station.

DESCRIPTION OF THE EMBODIMENTS

Before describing features of particular arrangements in more detail, a general overview is provided:

Battery packs may be used in a wide range of applications. Such applications may include: electric or hybrid vehicles, local energy storage, or industrial back-up power supplies. Battery packs or modules comprise a plurality of cells. The cells in a battery module may all be of the same general chemistry. In some cases, a hybrid battery may be provided. A hybrid battery may comprise a battery module formed from at least two different battery cell chemistries. The battery module may comprise a single-use battery, but are typically of more use if the battery comprises at least one rechargeable cell. Such rechargeable cells may, for example, comprise lithium ion cells or lead acid cells.

Battery modules comprise a plurality of cells and appropriate choice of cell arrangement within a battery module typically sets the voltage and capacity provided by the battery module. Battery units, modules or packs may be used in a wide range of applications and depending on the application battery units that can provide particular voltages and/or capacities will be selected. Conventionally a plurality of different battery units have been manufactured each providing a particular specific voltage and capacity, the relevant unit being selected and employed for a particular application. Embodiments seek to provide a more universal battery unit or pack that is configurable and in some cases self-configurable to provide a desired voltage and/or capacity, using controllable switching circuitry to interconnect cells or banks of cells within the battery pack in either a series or parallel arrangement thereby controlling the voltage and/or capacity output. This allows a battery pack to be employed more universally reducing the manufacturing and stocking requirements of different battery packs and thereby reducing overheads.

The self-configurable nature of embodiments of the battery pack enables it to be simply inserted into a circuit whereupon it can detect the required voltage for example and control circuitry can configure the switching circuitry to provide this voltage. Where for example the battery unit is used in a backup power situation, which is a fairly common use for such battery units, circuitry within the battery unit can detect the voltage and/or load of the system it is to provide power to and can configure itself accordingly by controlling the switching circuitry which interconnects at least some of the cells within the unit. Once configured an isolating switch within the battery pack can be switched to connect the cells to the terminals of the battery pack.

Aspects and embodiments recognise that provision of a configurable battery module that is able to adapt in response to at least one characteristic of the power supply system within which it has been placed, may allow not only for more universal application of such a module but also for improved battery module operation within that power supply system, allowing for a battery module to operate as an intelligent, or more active, component in a power supply system or overall system and allowing its configuration to be changed to compensate for changes in load for example.

Embodiments recognise that a battery module may be configured to operate in conjunction with other battery modules and or a central control hub, to adapt to changes in themselves or in other battery modules or in the requirements of the system and to self-optimise and form a distributed battery control system.

Aspects and embodiments recognise that there may be advantages associated with allowing a battery module within a power supply to determine characteristics of the power supply into which it has been placed. Furthermore, embodiments recognise that by allowing a battery module to communicate or issue signals outside of itself, it may be possible to more effectively manage that battery module within the power supply and/or more effectively manage the power supply system into which the battery module may be placed. A general battery module arrangement may comprise a battery module which is removably insertable into a power supply system. The cell chemistry and physical size of a battery module may be selected in dependence upon envisaged application. The voltage and capacity may also depend on the application but each battery module is able to configure itself to supply different voltages and/or capacities. The battery module comprises a controller or battery management circuitry that is configured to generate a control signal in response to a detected characteristic of a circuit to which it is connected or a characteristic of the battery module itself. The battery module may also comprise an output configured to output said control signal to a component of said power supply system external to itself.

In some embodiments the battery modules are configured in response to an external signal, which may take the form of a switch operated by a user, in other embodiments they maybe self-configurable. Figure l shows an example of such a self-configurable battery unit to according to one embodiment. Battery unit to has positive and negative terminals 12,14 respectively between which multiple banks of cells, Cl to C4 are arranged, the banks of cells Cl to C4 being interconnected by switches 20 which are controlled by controller 35 to provide either serial or parallel connections between the banks of cells.

Battery unit 10 also comprises an isolating switch 22 for connecting or isolating the banks of cells from the terminal 12 via in this embodiment a sensor 30. Sensor 30 is a current and voltage sensor and can sense the voltage at terminal 12 when switch 22 is open, and this provides it with information on the voltage level required by the circuit (not shown) to which it is connected. Sensor 30 can also sense the current that is supplied by the battery module 10 to the circuit when switch 22 is closed and the battery is supplying power to the circuit. It can also sense current flowing in the other direction during a charging cycle.

Sensor 30 outputs the information that it has sensed to controller 35 which in this embodiment comprises a microprocessor. Controller 35 determines from the information received the required voltage and/or capacity of the battery module and transmits control signals to the switches 20 such that they connect the cells in such a was so as to provide the required output voltage and/or capacity. Following configuration of the battery module, controller 35 controls isolating switch 22 to connect the cells to the terminal 12. In this way the battery unit supplies the required voltage to the system to which it is connected.

During operation sensor 30 may continue to monitor the voltage and current at the terminal 12 and may control switches 20 to rearrange the configuration as required. In this regard, it may be that one of the cells within a banks of cell is failing and where the banks of cells are not currently all arranged in series, then the bank of cells with the failing cell can be isolated from the other cells and from the terminal 12, while the module can be reconfigured to still output the desired voltage.

Figures 2a - 2e show different possible interconnections of the cells in the battery pack of Figure 1, each arrangement providing a different voltage and capacity. In this way a single battery pack with a more universal application that can be used in different systems is provided. This removes the need to manufacture and stock a different type of battery pack for each scenario.

Figure 2a shows the switches 20 arranged with each bank of cells Cl to C4 connected in parallel. Thus, where each bank of cells provides a 12V output, then such an arrangement provides a 12 V battery with a high capacity.

Figure 2b shows the banks of cells Cl to C4 arranged with Cl and C2 in series and with C3 and C4 not being used. Thus, it provides a battery pack with a 24V output used at half capacity. This may be useful where a battery pack with a long lifetime and high reliability is required as when cells within bank Cl or C2 start to degrade then one or both of banks C3 or C4 can be switched into the circuit, with the degraded bank being switched out.

Were the circuit of Figure 2b to be used at full capacity, switch 20 would connect to point 20a and switch 20’ to point 20b. This arrangement is shown in figure 2C.

Figure 2d shows the battery pack used at half capacity and outputting 24V with C3 and C4 being used. As can be seen by simply switching the switches 20 different banks of cells can be connected between the terminals. In this way as cells within a bank age the bank may be replaced by another. The replacement may be temporary with a bank of cells recovering or being recharged. The trigger to switch between banks may be based on a time each bank is used for, determined by the microprocessor 35, or it may be that sensor 30 detects a fall in current or a drop in voltage output by the bank and this may trigger the microprocessor to switch to using another bank.

Figure 2e shows the battery pack arranged with the switches set to output 48V, that is all of Ci to C4 being arranged in series. In this case were a cell within a bank to start to fail, then there is no possibility of switching a bank out and retaining the output voltage.

Figures 1 and 2 show a fairly simple example where four banks of cells are arranged between switches which allow them to be connected in parallel, in series, in a combination of both or out of the circuit completely. Clearly more cells could be arranged in more complex arrangements with further switches providing for a greater number of different possible voltage outputs and capacities. For example, the individual banks of cells Cl to C4 may be formed of 4 sets of 3V cells which may be arranged in series, or they may be interconnected by controllable switches in a matrix type arrangement in which the cells within the banks can be interconnected in different ways. This may have the advantage of allowing individual cells to be switched into and out of the system as they fail which may increase the lifetime of the module.

Figure 3 shows such an arrangement where each of Cl to C4 is a bank of cells. Each bank of cells is formed of an arrangement of 4 cells each configured to output 3V.

These can be arranged in series or in parallel, such that each bank of cells may, for example, be configured to output any multiple of 3V up to 12V, and the module may output any one of 3V to 48V, although in most embodiments the configuration will be arranged such that it is controlled to output one of 12V, 24V, or 48V. There are certain voltage levels that are provided by conventional battery packs and it may be advantageous to limit the configurable battery to only supply one of these. When determining the voltage level to configure the battery module to output, having only a limited number of output voltage to select between makes the selection easier and reduces problems that might arise due to inaccuracies in sensing or variations in the power supply being sensed resulting in a selected output voltage being incorrect.

Where there are only a few to select between it is much less likely that an incorrect voltage will be selected.

Control of the switches can also be used to provide different capacities and the required capacity can be determined by the sensor sensing the current supplied by the battery module to the load. Where this is high and the configuration is such that the capacity of the battery module can be increased, then the controller can reconfigure the battery module to provide an increased capacity. In this embodiment, the arrangement of interconnections provided by the switching circuitry is such that within each bank of cells the individual cells may be connected in parallel or in series or in a combination of the two. Within the battery unit as a whole the switching circuitry is arranged so that the banks themselves can be connected in series with each other, in parallel with each other, or in a mixture of the two, or a bank may be isolated from the terminals.

Figure 4a illustrates schematically one possible generalised system 1 in which one or more battery modules according to at least one embodiment may be configured to operate. In the arrangement shown, an energy source 110 is provided which supplies a load 120 with power via a power supply 130.

The energy source may comprise a grid power supply, a generator power supply, a renewable power energy source, such as a wind turbine or solar cells and similar. The energy source may comprise a combination of such energy sources. The energy generated by those sources is passed via a connection 140 to the power supply system 130. The power supply system 130 receives the energy, adjusts that energy as appropriate to make it suitable for the load 120 and passes it, as appropriate to the load i20via a connection 150.

Figure 4b illustrates schematically a power source supply arrangement. The power source supply 130 receives energy from the energy source 110 and passes it to the load 120. In the arrangement shown in Figure 4a, the power supply system 130 comprises power source adjustment circuitry 160 and a rechargeable battery cluster 170. As shown in Figure 4b the power source adjustment circuitry may be configured to receive energy from the source 110 and adjust the characteristics of the supplied energy to meet the needs of the load 120 and supply such adjusted energy directly to the load 120. The power source adjustment circuitry 160 may also be configured to supply the rechargeable batteiy cluster 170 with appropriately adjusted energy and act as a charging circuit for this cluster of battery modules. In the event that the primary energy source 110 is unavailable, energy stored in the rechargeable batteiy cluster 170 may be supplied to the load 120 and this is also under the control of the power source adjustment circuitiy 160. A sensor within the rechargeable batteiy cluster 170 will sense the voltage supplied to the load when the energy source 110 is supplying the power and will configure itself to supply a suitable voltage and in some cases provide a suitable capacity. Although in this embodiment the battery cluster 170 is shown as being a rechargeable battery cluster it should be understood that a non-rechargeable battery cluster may be used in some embodiments, in such a case the link from power source adjustment circuitry 160 to battery cluster 170 will be absent.

The battery cluster 170 comprises a plurality of battery modules, at least one of which is a configurable battery module according to an embodiment. When such a configurable module is added to the cluster, it will configure itself to output the voltage level required by load 120. In this regard, it may do this in response to receipt of an initialisation signal indicating what this voltage is, or it may do this in response to a sensor within the module detecting the voltage supplied by other battery modules or by the energy source and in response to this, a controller within the module will control the switching circuitry to interconnect cells within the battery module to output the required voltage.

Figure 5 shows a cluster of battery modules 170 arranged as back-up power to a load according to a further embodiment. In this embodiment, the battery modules within the cluster have the standard form factor of lead acid batteries. Battery module 10 is inserted into the cluster 170 to replace one of the lead acid batteries that has failed or is nearing failure. Following insertion into the system, the detection of a voltage at the terminals will trigger the controller 35 within the battery module 10 to wake up and it will determine the voltage difference between the terminals 12,14 using sensor 30. Having sensed the voltage, it will configure switches 20 to connect the cells C such that they output a voltage that is substantially the same as the detected voltage and once this has been done it will control isolating switch 22 to close such that the cells are connected to the terminals and the battery module forms part of the backup power system. In this way, the battery module acts as a self-configurable battery module that has the form factor of a conventional lead acid battery module and can simply be inserted into a power supply system that is configured to use such conventional battery modules, whereupon it will configure itself to provide a suitable output voltage.

Figure 6 shows an alternative embodiment where the backup power supply 170 is formed of a plurality of batteries, which each have sensors 30, controllers 35 and communication circuitry 50 operable to communicate wirelessly with other battery modules. Battery module 10 is configured in this embodiment to be the master battery and port 60 is both an input and output port, outputting control signals to control other battery modules 70 and 80 within the cluster. Port 60 is also configured to receive signals from these battery modules. These signals may be indicative of an operational characteristic of the further battery modules and the communication circuitry 50 may simply receive these signals or it may actively interrogate the further battery modules 70, 80. These received signals may provide information on the current charge status of the modules and also in some cases on their potential failure.

Controller 35 within master battery module 10 analyses the signals received from the other modules 70, 80 along with signals received from its own sensor 30 and determines a preferred configuration of each module within the system and from this analysis generates control signals. These control signals are transmitted from master battery module 10 to battery modules 70 and 80 and to its own switching circuitry 20. The signals output to other battery modules may indicate a change in the configuration of the battery module or they may indicate that that module should be isolated from the system. The configuration of the battery modules 70 and 80 may be performed in response to signals detected by its own sensors and/or in response to the signals received at their input ports from the master battery module 10. In this regard sensors 30 within each battery module may detect the voltage levels supplied by individual cells or banks of cells within the battery module and determine cells that are failing. Controllers 35 within the module may reconfigure to remove failing cells from the power supply, while still configuring the module to supply a voltage level indicated by a control signal received from the master battery module 10.

In this embodiment the battery modules communicate with each other wirelessly, while in other embodiments they may have hardwired connections or communicate in some other manner.

In the embodiment described above battery module 10 acted as a master battery module. In other embodiments there may be an external power management system (not shown) which provides central control of the charging and loading of the battery modules. In this embodiment the battery modules are connected to the charging and load circuits by switching circuitry 90, which can be controlled by signals from the power management system to connect individual modules to the load and charging circuits as required. The power management system also transmits control signals to the battery modules which indicate desired configurations of the individual battery modules. These signals are received by communication circuitry 50 and transmitted to controller 35 which controls switching circuitry 20 and isolating switches 22 accordingly. Thus, in this embodiment rather than receiving external control signals from a master battery module they are received from a central power management system.

Figure 7 shows a further example of a battery module 10 according to an embodiment. In this example, the battery module 10 is used as the sole power supply for a system, in this case the motor 120 of an electric bike. The electric bike has a motor 120 that is powered by a battery module 10 and has control circuitry 180 that controls the supply of power to the motor 120 when it is required to be driven and controls supply of charging current when a charging circuit is connected to charging terminals 190 present on the bike.

As the battery module 10 is the sole power supply, when the battery module 10 is used for the first time, there is no means of determining the voltage level required by the electric bike motor 120. This is addressed in some embodiments by a battery module 10 that has a port for receiving a control initialisation signal which indicates the voltage which should be used. This may be a port that can receive a wireless communication signal, perhaps from a mobile phone of the user, which will indicate the voltage level required or it maybe a simple mechanical switch that the user can set to the required voltage level or which can in some cases interlock with the bike connector to “auto” set the switch.

In alternative embodiments, the battery module 10 may be self configurable and on connection to the electric bike and the electric bike being switched on, the battery will configure initially with its lowest possible voltage level configuration. In this regard, the battery module 10 comprises a plurality of cells that can be configured to output one of a plurality of voltage levels and initially it will output the lowest one of these and will determine whether any current is supplied from the battery at this voltage level. If no significant current is supplied, then it will reconfigure itself to the next higher voltage level and will determine if this is sufficient to power the circuits of the bike. It will continue to do this until a load is taken from the battery indicating that the circuit that it is powering has received enough voltage to switch it on. In this way, the battery module 10 can configure itself by determining the voltage level required to drive the load circuit. By starting at the lowest possible voltage potential damage to the load and control circuit can be avoided.

Controller 35 will control the switches to provide the desired voltage and may also control the switches to change the capacity of the battery module. In this regard, there maybe some external control mechanism which can indicate the expected journey length and the battery module will configure the capacity accordingly.

When the electric bike is to be recharged then a charging circuit will be connected to charging terminals 190. In some cases, the charging circuit may be specific to that particular electric bike and may be configured to charge at the voltage level of the load circuit of the electric bike. Alternatively, there may not be a specific charging circuit available. Embodiments can connect to different charging circuits and the self-configurable nature of the battery module allows it to be recharged by chargers that are not necessarily configured for the voltage level required to drive the electric bike itself. Thus, in embodiments, the sensor 30 will detect the voltage level of the charging circuit and controller 35 will control the switching circuitry 20 to configure the cells in a way appropriate to the voltage level of the charging circuit prior to the cells being connected by isolating switch 22 to this circuit. In this way, the battery module can be charged by different charging circuitry, which would allow central charging circuitry available perhaps in a town centre to be used for a number of different electric bikes. Furthermore, in some embodiments an input on the battery module may allow information regarding journey length of a subsequent journey to be received, perhaps via a wireless input from an app on the user’s phone. This information will allow the controller 35 to configure the cells not only to provide a suitable voltage but also the required capacity for the journey. This can allow the charging time to be reduced where the subsequent journey is to be short as fewer cells are used and therefore the charging time for them to be being fully or nearly fully charged is reduced. Fully charging cells rather than partially charging them can increase the lifetime of the cells for some cell chemistries.

Figure 8 schematically shows a base station 190 and its associated power supply. The power supply maybe mounted adjacent to or within the structure mounting the antenna of the base station. The base station is in this embodiment located at a location remote from a mains power supply and as such uses an intermittent energy source 110, which may for example be a solar power or wind turbine energy source.

Base stations may be powered by 24V, or 48V and very occasionally 12V power supplies and a configurable battery operable to configure itself to output any one of these voltages therefore provides a suitable power source for any one of the sites and can be used to replace conventional batteries within battery clusters 170 which act as backup power as they fail at these sites. In this way the base station network operators need only stock and carry one type of battery module.

Base station 190 comprises communication and processing circuitry 180 which receives wireless signals from user equipment and transmits them to further base stations or other user equipment. This circuitry is powered under the control of power control circuitry 160, which receives power from the energy source 110 when it is active or from the backup power source 170 which comprises the cluster of battery modules. Power control circuitry 160 also controls the recharging of the battery modules within battery cluster 170 using energy from energy source 110.

The battery cluster 170 is made up of removable battery modules, including at least one configurable battery module 10. This is inserted into the battery cluster 170 and a sensor in the battery module is operable to detect the voltage required by the system and a controller within the module will then configure switching circuitry to interconnect the cells within the battery module to provide the required voltage. The sensor will continue to detect the voltage and may act to reconfigure the battery module where required. This may include changing the capacity of the battery module and/or changing the nominal output voltage. The latter may occur where the actual output voltage has fallen due to the battery charge status falling. Reconfiguration may also occur where the sensor detects a cell within the battery module is failing whereupon it may reconfigure to supply a same voltage using a different subset of cells.

In some embodiments the controller within the battery module may be configured in response to the sensor detecting a fall in the charge level of a significant number of the cells within a module to output a low power indicator signal to the power control circuitry prior to controlling the isolating switch to isolate the battery module from the power supply. Where a significant number of cells are becoming discharged then it may not be possible to reconfigure the battery module to use other cells and isolation from the system may be desirable. However, prior to isolation it may be advantageous to warn the base station that this is about to happen. Thus, there may be a predetermined charge or voltage level which triggers the warning signal and a lower isolation level which triggers the isolation of the battery module from the power supply unit. Alternatively there may be one level which triggers the warning signal, isolation occurring a predetermined time thereafter. In any case, the output of the warning signal to the power control circuitry 160 enables the power control circuitry to form a controlled power down of the processing and communication circuitry 180 of the base station. This controlled power down allows the base station to notify user equipment of impending power loss which allows them to seek connections to other cells where they are available, it also enables the base station to save parameters before shutting down enabling faster reboot when power is restored.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

1. A configurable battery module operable to provide at least one of a plurality of output voltages and a plurality of capacities, said configurable battery module comprising: two terminals; a plurality of cells; switching circuitry for selectively connecting at least a subset of said plurality of cells in at least one of series and parallel between said two terminals; and a controller operable to select at least one of said output voltage and said capacity and to configure said battery module by controlling said switching circuitiy to connect said cells so as to provide said at least one of said selected output voltage and said capacity.

2. A configurable battery module according to claim l, said configurable batteiy module further comprising: a sensor operable to detect at least one characteristic of at least one of said battery module and at least one circuit to which said battery module is connected; wherein said controller is operable to select said at least one of said output voltage and said capacity in dependence upon an output of said sensor

3. A configurable batteiy module according to claim 2, wherein said at least one circuit comprises a charging circuit for delivering charging current to said configurable battery module.

4. A configurable battery module according to claim 2 or 3, wherein said at least one circuit comprises a circuit arranged to be driven by said configurable batteiy module, such that said configurable battery module is operable to supply current to said circuit.

5. A configurable battery module according to any one of claims 2 to 4, wherein said characteristic of said at least one circuit comprises a voltage level, said controller being operable to control said switching circuitry in response to said detected voltage level.

6. A configurable battery module according to claim 5, wherein said controller is operable to select from said plurality of output voltages an output voltage closest to said detected voltage level and to control said switching circuitry such that said plurality of cells are connected to provide said selected output voltage.

7. A configurable battery module according to any one of claims 2 to 6, wherein said characteristic comprises an output current, said controller being operable to control said switching circuitry in response to said detected current to configure said battery module to provide a selected capacity.

8. A configurable battery module according to any one of claims 2 to 7, wherein said characteristic comprises at least one of a current and a voltage output by at least one of said cells of said battery module, said controller being operable to control said switching circuitry in response to said detected at least one of said current and said voltage.

9. A configurable battery module according to any one of claims 2 to 8, wherein said characteristic of said circuit comprises at least one of an output from a motor speed controller within said circuit; an output from a load controller; an output from a control bus controlling components powered by said battery module; an output from further battery modules forming part of a same power supply system, and an environmental characteristic.

10. A configurable battery module according to any one of claims 2 to 9, wherein during initialisation of said battery module, in response to said sensor detecting said circuit to be unpowered, said controller is operable to control said switching circuitry to configure said battery module initially to provide a lowest one of said plurality of output voltages, and to determine from said sensor if a current output by said battery module to said circuit is greater than a predetermined level and if not, to reconfigure said switching circuitry to progress through said plurality of output voltages until said sensor detects said current output by said battery module to said circuit to be greater than said predetermined level.

11. A configurable battery module according to any one of claims 2 to 10, wherein said sensor is operable to determine a voltage output by said plurality of interconnected cells following control of said switching circuitry and where it is substantially less than a voltage level expected by said controller said controller is operable to control said switching circuitry to connect said cells to provide a higher voltage level.

12. A configurable battery module according to any preceding claim, wherein said battery module comprises an input operable to receive a control signal; said controller being operable to select said at least one of said output voltage and said capacity in dependence upon said control signal.

13. A configurable battery module according to claim 12, wherein said control signal comprises at least one of: an initialisation control signal; a control signal received from a further battery module arranged to power a same circuit as said battery module, and a power management system for controlling a plurality of battery modules powering a same circuit.

14. A configurable battery module according to any preceding claim, said controller being operable to generate a control signal to control at least one further battery module arranged to power a same circuit as said configurable battery module, said configurable battery module further comprising an output for outputting said control signal to said at least one further battery module.

15. A configurable battery module according to any preceding claim, wherein said switching circuitry further comprises an isolating switch operable to selectively isolate said plurality of cells and said switching circuitry from one of said terminals.

16. A configurable battery module according to claim 15, wherein said controller is operable following configuring said battery module to control said isolating switch such that said plurality of cells and said switching circuitry are connected to said one of said terminals.

17. A configurable battery module according to claim 15 or 16, when dependent on claim 8, wherein said controller is operable in response to said sensor indicating said at least one of a current or a voltage output by said at least one cell has fallen below a predetermined level to determine whether a configuration of said plurality of cells not including said at least one cell is possible to provide said selected output voltage and where so, to control said switching circuitry to connect said cells to output said selected voltage and where not to control said isolating switch to isolate said plurality of cells from said one of said terminals .

18. A configurable battery module according to claim 17, wherein said controller is operable prior to controlling said isolating switch to generate and output a low power indicator signal.

19. A configurable battery module according to any preceding claim, said configurable battery module being housed in a housing with a standard form factor.

20. A configurable battery module according to any preceding claim, where said cells comprise lithium ion cells.

21. A configurable battery module according to any preceding claim, wherein said plurality of cells are connected together in a plurality of banks, each bank providing a predetermined nominal voltage level, said controller being operable to control said switching circuitry to connect at least a subset of said banks in parallel in order to provide an increased capacity and to control said switching circuitry to connect at least a subset of said banks in series in order to provide a higher output voltage.

22. A configurable battery module according to claim 21, wherein said plurality of nominal output voltages comprises 12V, 24V and 48V.

23. A configurable battery module according to any preceding claim, wherein when said at least one of said selected output voltage and capacity are such that a subset of said plurality of cells are connected to said terminals at any one time, said controller is further operable to periodically switch between subsets of cells that are connected to said terminals.

24. A configurable battery module according to any preceding claim, wherein said battery module is a configurable hybrid battery module and said plurality of cells are formed of cells of at least two different cell chemistries.

25. A power supply system comprising: at least one battery module according to any preceding claim and at least one further battery module.

26. A power supply system according to claim 25, further comprising at least one circuit electrically connected to said battery module. 2η. A power supply system according to claim 26, wherein said at least one circuit comprises a system load.

28. A power supply system according to any one of claims 25 to 26, wherein said at least one circuit comprises a charging circuit for supplying current to said at least one battery module.

29. A power supply system according to any one of claims 25 to 28, wherein said power supply system further comprises a power management system for controlling operation of said plurality of battery modules.

30. A power supply system according to any one of claims 25 to 29, wherein said power supply system comprises a backup power supply system for a base station.

31. A configurable battery module substantially as hereinbefore described with reference to the accompanying figures.

32. A power supply system substantially as hereinbefore described with reference to the accompanying figures.