GB2550881A

GB2550881A - Methods and apparatus for energy storage

Info

Publication number: GB2550881A
Application number: GB1609344.5A
Authority: GB
Inventors: Shaw Robin; Irish Stephen
Original assignee: Hyperdrive Innovation Ltd
Current assignee: Hyperdrive Innovation Ltd
Priority date: 2016-05-26
Filing date: 2016-05-26
Publication date: 2017-12-06
Anticipated expiration: 2036-05-26
Also published as: GB201609344D0; GB2554789A; GB2554789B; WO2017203265A1; GB2554788A; GB2554788B; GB201712035D0; GB2550881B; GB201712037D0

Abstract

Methods and apparatus for energy storage A battery module controller configured to cooperate with other similar battery module controllers to provide a self-organising array of battery modules is disclosed herein. Each battery module comprises at least one energy storage cell. The battery module controller comprises a unique identifier and is configured to (i) send a network message comprising its unique identifier; (ii) receive one or more network messages each comprising a unique identifier of a respective other controller of a battery module in the array; and (iii) identify, based on the received one or more messages, one of the controllers of the array as a master controller. Preferably the master controller is used to determine a charging demand for charging the array of battery modules and to send a network message with this charging demand to a charger, or to control a diagnostic process of the array. Other aspects of the invention include a battery module controller configured to determine the electrical arrangement (series and/or parallel) of a plurality of battery modules, a method for determining the arrangement of battery modules in an array, and a method of assembling an array of battery modules.

Description

Methods and Apparatus for Energy Storage

This invention relates to methods and apparatus related to energy storage, and in particular to battery controllers and battery control methods, and in particular to battery control methods and apparatus for systems comprising pluralities of interconnected batteries.

Generally, battery powered apparatus is arranged to accept a predetermined number of batteries in a predefined arrangement. Typically one or more batteries will be installed into a pre-existing compartment with terminals or connection leads to allow the battery or battery systems to simply be plugged in. This is advantageous because the size and shape of the pre-existing compartment can physically constrain the number and type of batteries which can be introduced to the apparatus. This makes it unlikely that consumers and other operators will plug unsuitable batteries into the apparatus.

In addition, if the number and type of batteries and their electrical arrangement (e.g. the arrangement of series and/or parallel connections between these batteries) can be known in advance the power delivery performance and charging demand of these batteries can be predicted with reasonable accuracy.

This approach to arranging series of batteries, and sets of series of batteries arranged in parallel, has previously been thought to be entirely adequate.

The present disclosure however may provide an adaptable and fault-tolerant arrangement system. Aspects and examples of the invention aim to address this and other technical problems and are set out in the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 includes Figure 1A which shows a type of battery module, and Figure 1B which shows a further example of the type of battery module illustrated in Figure 1 A;

Figure 2 shows an array of battery modules which may comprise battery modules such as those illustrated in Figure 1;

Figure 3 shows a flow chart to describe a method of self-arbitration for implementation by apparatus such as that illustrated in Figure 1 and Figure 2;

Figure 4A shows another array of battery modules;

Figure 4B shows yet another array of battery modules;

Figure 5 shows a flow chart to describe a method of determining the arrangement of battery modules in an array using current measurements;

Figure 6 shows a flow chart to describe a method of determining the number of strings in an array of battery modules in an array using voltage measurements; and

Figure 7 shows a flow chart to describe a method of determining the arrangement of battery modules in an array using voltage measurements.

In the drawings like reference numerals are used to indicate like elements.

DETAILED DESCRIPTION

Figure 1A illustrates a battery 100 comprising a battery controller 102. This controller 102 is configured to communicate with other similar controllers with which it may be connected so that a set of battery modules having such controllers can organise themselves to operate in concert to provide improved power characteristics. The ability to self-organise may be significant because it enables the array as a whole to be fault tolerant - it includes inherent redundancy because if one module fails, the array as a whole may continue to operate. As will be explained below, to provide this self-organising functionality the battery controller is configured so that, when it is connected in communication with other such battery controllers it sends a message to those controllers. This message comprises the controller’s own unique identifier. In addition it also receiver network messages from each of the other controllers with which it is connected, each such message also comprising a unique identifier of each other battery in the array. One of the controllers in this array can then be identified as the master controller.

This master controller may then control functions of the array as a whole such as charging control, power demand balancing across the array, and fault-finding.

Figure 1A shows an example of a battery 100 comprising a controller 102 configured to operate in this manner. In addition to the controller 102, the battery 100 comprises a communication interface 103 adapted for sending and receiving messages over a communications link 110 to permit communication with other similar controllers. The communication interface illustrated in Figure 1 comprises a serial BUS interface, such as a controller area network, CAN, interface.

The controller 100 comprises at least some data storage, for example in the form of nonvolatile memory. This data storage stores a unique identifier of the controller. The controller is configured to operate the communication interface 103 to broadcast its unique identifier at intervals (e.g. periodic or aperiodic intervals, or in response to sensing connection to another similar battery). The controller 102 is also configured to use the communications interface 103 to listen to the communications link 110 to obtain broadcast messages received from other similar controllers and to obtain from those messages the unique identifiers of those controllers.

In operation, the controller sends a message comprising its unique identifier. This may be done at intervals (e.g. periodically, aperiodically, or in response to a trigger such as sensing connection to another device such as a charger or another similar controller). The controller 102 also listens at the communications interface 103 to receive one or more network messages from other similar controllers. Each such received message comprises a unique identifier of the controller which sent it. Each such message can also carry battery data such as battery terminal voltage.

The controller 102 can then identify, based on these received messages, one of these other controllers as a master controller. One way this can be achieved is by selecting a one of the controllers identified based on the values of the unique identifiers received in these messages. For example, the controller having the highest value identifier may be selected as the master.

The controller 102 is configured so that, in the event that it is connected in a series of batteries and designated as the master controller, it determines a charging demand for the series based on the received messages. For example, the battery terminal voltages can be obtained from the messages and summed together by the master controller to determine the voltage of the series. The controller can then send, via the communications interface, a network message comprising the charging demand via the communications interface. This too may be sent at intervals (as described above). This charging demand may be configured to cause a charger coupled to the series to provide electrical energy to the series according to the demand.

This is just one example of how the master controller may be used. Another example of its usefulness is as follows. The controller may be configured to store the unique identifiers received from other controllers (e.g. those associated with other similar batteries). In the event that a new message is received, the controller may compare the unique identifier carried by that new message with the stored identifiers. In the event that the unique identifier does not match the stored identifiers, the controller may repeat the process of identifying which controller in the series is to be master. Yet a further example is that the controller may repeat the process of identifying the master in the event that a message comprising a particular one of the stored identifiers is not received for more than a selected interval. These two examples are significant because they permit the series of batteries to reliably elect a master controller in the event of addition of a new battery, or the removal or failure of an existing one. It will be appreciated in the context of the present disclosure that this may provide an inherently robust and adaptable system which can continue to operate in the event of loss or failure of a member of a series. In addition it can also allow a series to be easily augmented or maintained by simply plugging in supplementary batteries.

The controller 102 may also be configured so that, in the event that it is designated as master it can control a diagnostic process of the series. Conversely, because all members of the series apply the same rules of arbitration to select the master controller, each controller knows which commands are to be obeyed. This can permit the master controller to perform one or more diagnostic processes in the series.

Examples of such embodiments will be described in more detail below. It will be appreciated in the context of the present disclosure however that the batteries need not report their terminal voltage, the master may simply make a charging demand based on the number of unique identifiers it has received. Although an example of a single series of batteries has been described, a set of these series strings of batteries may also be arranged in parallel to provide an array - a set of series strings, each string connected in parallel with the others. Accordingly, embodiments of the controller illustrated in Figure 1A may be configured to determine the arrangement of the electrical connections between battery modules in the array. In other words it may determine the electrical arrangement of series and parallel connections which make up the array. In such embodiments the charging demand mentioned above may comprise both a current request and a voltage request. The current request may be based on the number of parallel strings in the array.

Figure 1B shows a further example of a battery such as that shown in Figure 1A. The example illustrated in Figure 1B comprises a controller 102, three energy storage cells 104a-c; a voltage buffer 106 for providing an indication of the voltage across one of the cells 104 to the controller 102; a current sensor 108 for sensing current flowing into or out of the cells 104; a disconnector 105; and terminals 112a and 112b.

The controller 102 is coupled to the output of the voltage buffer 106 and to the current sensor 108. The controller 102 is also coupled to control the disconnector 105, and to send and receive messages via the communication interface 103.

The energy storage cells 104a-104c are coupled together in series, with the current sensor 108 and the disconnector 107. The current sensor 108, the disconnector 107, and the cells 104a-104c are together arranged between the terminals 112a, 112b so that a voltage based on the combined total voltage across the cells can be applied to the terminals 112a, 112b, and the current passed between the terminals can be sensed by the current sensor 108.

The disconnector 107 comprises an electrically operable impedance controller, such as a switch, contactor or relay or a voltage controlled impedance such as a transistor. The disconnector 107 can be controlled by the controller 102 to modify the impedance of a current path between the terminals 112a, 112b, for example to provide an open circuit impedance between those terminals.

The voltage buffer 106 is arranged to provide a cell voltage to the controller 102. Although not illustrated in Figure 1, the battery comprises one such voltage buffer for each cell to provide the controller with cell voltage data indicating the voltage of each of the cells. This may permit the controller also to operate a battery management system to balance cell voltages, for example by dissipating energy stored in one or more of the cells.

The controller 102 is configured to operate the communication interface to send and receive messages. These messages generally all comprise an identifier of the controller 102 and may also comprise at least one of: (a) some status information associated with the battery 100 in which the controller 102 is present and (b) one or more commands or requests. Different types of message may be involved. For example, the controller 102 is configured so that at intervals it broadcasts, via the communications interface 103, a report message comprising its unique identifier. This may permit the arbitration method described above to be carried out so that one controller of an array of batteries can be identified as a master. Where the messages include a command or request these messages may also comprise an identifier of the device, or the type of device, for which they are intended. Where the messages include status information this may comprise one or more parameters selected from the following list: terminal voltage; one or more individual cell voltages; battery state of charge; battery temperature; electrical current sensed by the current sensor, error flags and status indicators such as overvoltage, under-voltage, over-temperature, under-temperature indicators. Examples of different message types and the data they may contain are explained below.

One example of a command message may comprise a disconnect message carrying an identifier of a controller and a command to cause the identified controller to operate its disconnector 107 to switch off the current path through the battery - e.g. to provide an open circuit voltage at the battery terminals. The controller 102 is configured so that, in the event that it receives a disconnect message from a controller of the array which has been designated as the master controller, it responds by operating its disconnector 107 to provide an open circuit impedance at its terminals. To achieve this, the disconnector 105 may disconnect fully (e.g. by breaking the current flow path altogether), or it could just prevent either charging or discharging. For example, if the disconnector 105 comprises a mechanical contactor the current path may be broken, whereas if it comprises a pair of back-to-back MOSFETs current flow may be switched off in only one direction. As noted above, the controller is also configured so that, at intervals, it sends report messages via the communications interface 103 indicating its status. These messages may reflect the connection status of the current path through the battery. It will be appreciated in the context of the present disclosure that disconnecting the current path through the battery need not disconnect the communication interface 103 from the channel 110. A “disconnected” battery may remain connected for communications purposes (e.g. via CAN so will maintain comms with the master controller throughout the operation). The “disconnection” in this context refers to preventing or modifying current flow through the main terminals of the battery.

The controller 102 is configured so that in the event that it is designated as the master controller, it determines the electrical arrangement of the array in which it is connected by communicating with the other batteries in that array. Operation of the controller 102 to perform this process will now be described.

In operation, when current is being supplied to the battery (and to the series of batteries in which it is included) from a charger the controller 102 selects, from the stored list of unique identifiers, another battery of the array which is to be disconnected. The controller 102 then sends a disconnect message via the communication interface 107 to the controller 102’ of the selected other battery. After the disconnect message has been sent, the controller 102 verifies that the selected battery has been disconnected based on report messages received over the communication interface from that selected battery. The controller 102 then receives report messages from the other batteries with which its communication interface 107 is able to communicate. The controller then identifies the batteries which are connected in series with the selected other battery by identifying those batteries whose report messages indicate zero current. The master then knows how much current it should be receiving from the charger, and can compare this with the measured values received from the packs in the array. It can then carry out the self-test procedure and determine which packs are in each parallel string whilst controlling the current being requested from the charger, which it will use as a comparison as explained in more detail below.

An example of the kind of data which may be obtained by this process is outlined in the table below. Prior to the master controller (designated ID 1 in the table below) sending a disconnect message, it has obtained from report messages received from other similar controllers. These report messages provide an indication of the electrical current sensed by those controllers. In the example illustrated below, the master controller has selected controller 3 to be disconnected, and sent a disconnect message to that controller (designated 3 in the table below). After sending the disconnect message, the master controller obtains electrical current values from further report messages received from the other controllers.

Table 1 - Example of Reported Current Values Before and After Disconnect Message

It can be seen from Table 1 that after one of the controllers has received a disconnect message, the reported current passed by some other controllers (designated 2 and 5 in Table 1) is reduced to zero. The master controller 102 can thus identify those other controllers (2 and 5) as being in series with the controller it selected for disconnection. It may allocate a string identifier to these batteries and store data indicating the string to which each battery has been allocated. For example, the string ID may be selected based on the battery which is selected for disconnection, but any other method of selecting an identifier for the string may also be used. An example of data which may be stored after the performance of the method explained above with reference to Table 1 is shown in Table 2.

Table 2 - Allocation of Batteries to Strings

This process can be repeated by reconnecting the selected battery, and then disconnecting another selected battery of the array until the controller 102 has recorded data indicating the identity of the series string to which each of the different batteries belong.

The controller 102 may use this information about the electrical arrangement of batteries in the array to determine a charging demand for the array. For example, in the event that the controller determines that the array includes a single string, the controller may operate the communication interface to send a request message to a charger connected to the array which requests the delivery of a certain charging current. That charging current may bebased on the rated maximum of a single battery pack, multiplied by the number of parallel series (strings) of battery modules in the electrical arrangement. The controller may be configured to modify (e.g. to reduce the requested current) based on cell temperatures (high or low) or based on cell voltages (as the cells with the highest state of charge reach their upper charging threshold).

The controller 102 may also be configured so that, in the event that it is designated as the master controller, it performs safety control of the array. This may comprise performing a diagnostic for detection of faults in the array. For example, the controller 102 may determine based on the messages it receives from other controllers whether certain safety conditions are met. If such a safety condition is not met the controller may initiate a safety action.

An example of a safety condition is checking that the total voltage of the batteries which make up one string match the total voltage of all other strings. Another example is checking that the current through each battery of a string matched the current through other batteries in that string. Other examples are possible. For example, if this is happening during charging using a charger controlled by the master controller, then the master controller may confirm if the deduced number of parallel strings of the electrical arrangement is correct by referring to the expected charge current. For example, if there are 5 parallel strings and the total charge current requested from the charger is 100A then we would expect to see 20A on each string (allow a small measurement tolerance of, a few percent). If we disconnect one string then the current on the other 4 strings should increase to 25A. However if it was measured at 33A then this indicates that the deduced arrangement is incorrect and an error state should be indicated. Accordingly, the controller may be configured to send disconnect messages to a controller belonging to a first string and to sense current through a battery of a second, different, string during that disconnection. In the event that the sensed current does not match a prediction based on the deduced electrical arrangement, the controller may trigger a safety action.

An example of a safety action is sending an error message and/or operating a disconnector to disconnect the batteries of the array.

As an example of fault detection which can be implemented by the controller 102. The controller 102 can determine a charging current request, and send that request to a charger coupled to the array. The controller 102 can then determine an actual current sensed in the array, and compare that current with the charging current request. In the event that the actual current does not match the requested charging current, the controller 102 can determine that a fault has occurred and trigger a safety action. The actual current may be sensed by the controller 102 using the current sensor 108 in its battery. The controller 102 may also validate this ‘actual current’ by checking it against electrical current data received from another controller which is in the same string as that controller - e.g. it may check its own current sensor value against a current sensor value received from another battery which it has identified as being in the same string.

The above described methods and apparatus are just some of the advantageous configurations of this apparatus and its use. Others are possible. For example, the communication interface need not be separate from the controller. The controller 102 may itself be provided with a means for communicating information to the outside world to provide the communications link 110. As shown this link may be two way, that is, the link may allow for either or both of transmission and/or reception of communication signals. Alternatively, according to the desired functionality, the link may be only one way. Using communications link 110, the controller 102 may communicate information relating to the battery module 100, including state of charge, output voltage of one or more cells, output current, temperature, fault messages, or configuration information relating to the controller 102 or the battery module 100. Similarly the communications link 110 may allow the battery module to receive information, for example, configuration information for the module 100 or the controller 102; instructions for balancing the cells 104; requests for information relating to the module 100, or the controller 102, or one or more of cells 104; or instructions to decouple the module 100 as a whole from a wider array. The communications link may be provided as a wired, wireless, or fibre optic connection, for example, or by any other means known in the art for providing communications channels. Where it is provided by a wired connection it may be mediated through the terminals 112a, 112b, for example by modulating a data signal over DC power couplings connected to the terminals.

The controller 102 may receive information from both the current sensor 108 and the voltage buffer 106, and uses this to determine information, such as state of charge of the cell, or general battery health, or to balance charge between the cells 104. In addition, it may communicate this information via the communications link 110. The power output terminals 112 may be connected to an external device which requires power. In this case the external device draws power from the battery module 100, and the cells 104 deplete their charge. The charge on the cells may be replaced by connecting the battery module to a charging device, which supplied current to the cell. In each case, whether charging or discharging, information from the current sensor 108 can be used by the controller 102 to keep an accurate track of the state of charge of the battery module 100

As explained above, it will be appreciated that additional voltage buffers could be included to provide voltage measurements the voltage across more than one cell 104 of the module 100. In particular, a measurement may be taken across each cell 104 in the module 100 and supplied to the controller 102.

The controller 102 may use the measured current and voltage readings to perform load balancing on the cells 104. That is, the controller 102 may be configured to ensure that each cell 104 in the battery module 100 charges and discharges at the same rate, regardless of the capacity of any given cell 104 in the module 100. Such balancing may include calculating the state of charge of each cell 104 in the battery module 100, and/or diverting power from cells which have a higher state of charge into those which have a lower state of charge, in order to even out the state of charge of the cells 104 relative to one another. Power is supplied to, and drawn from, the battery module 100 via the two external power output terminals 112.

While Figure 1 shows a voltage buffer as measuring the voltage of a single cell, any means for measuring the voltage may be employed. Similarly, where current is measured any means for providing an indication of current level and/or direction may be used. While three cells 104a-c are shown as part of the battery module 100, any number of cells 104 may be included as part of a battery module. The cells 104 are typically rechargeable battery cells, but may be any type of energy storage cell. Lastly, while not shown in the Figure, the module may include means for measuring the temperature, e.g. thermocouples, thermistors or other thermometry means known in the art.

Messages sent and/or received by the controller 102 via the communication interface 103 may comprise one or more items of the following information: Cell Voltages, Cell Temperatures, Error flags and status indicators, Other component temperatures (eg PCB, conductors, ICs), Electric current readings, Serial number, and Charger control commands.

Other variations and changes to this apparatus are envisaged.

Turning now to Figure 2, an array 201 of battery modules 200a-i is shown. The battery modules 200 are arranged in three series strings connected in parallel, in Figure 2 each string includes three battery modules connected in series using their power output terminals 212. In addition, each battery module 200 is able to communicate with other battery modules in the array 201 via a series of busses 214a-c which connect the communications links 210 of each battery module 200 to one another.

In Figure 2 a total of nine battery modules 200 are shown connected together, as described above. It will be readily apparent, however, that the size of the array 201 can be arbitrarily chosen according to the power requirements of the system. Starting from just two modules, the array can be expanded arbitrarily, including threads of any length, and as many parallel threads as required. The array has overall output connections 222, to which a load can be connected to power the load, or to which a charger can be connected to recharge the cells of the array.

While the busses 214 of Figure 2 are shown as three separate busses, which allow connection between each battery module in the array, it is possible to link every battery module to the others using just a single bus, or indeed any number of busses connected together.

Additional functionality of the battery modules 100, 200 shown in Figures 1 and 2 is further illustrated in Figure 3. In battery arrays such as the example in Figure 2, it can be desirable to provide a centralised control of the array, to reduce the complexity of controlling each module of the array separately. It is possible to provide the functionality required to control the entire array to each controller 102. However, the array may be able to uniquely determine which controller is control of the array (which is the master controller), and which controllers do not directly control the array, but may respond to the master controller (the slave controllers).

Figure 3 illustrates one way in which this may be achieved. The first step 350 specifies that the controller sends a message comprising a unique controller identifier. The controller identifier may be a controller serial number, or it may be any other number assigned to the controller which is unique to that array. Since each controller which forms part of a battery module can do this, a plurality of network messages will be sent, one from each controller.

In step 352, the controller receives a network message comprising a unique identifier from each other controller of a battery module in the array. Once again, since the method may be carried out by each controller, each controller receives a network message from each other controller in the array.

In step 354, the modules use the received information, and their own unique identifier to identify a single master controller. Any controller which is not the master module is a slave module. The determination of which modules are master and slave modules may depend to some degree on the choice of unique identifier for the modules. As an example, if a controller serial number is used, then the controllers may determine which controller is master by ranking the serial numbers in numerical order. The rules may further specify that the controller with the lowest ranking serial number is the master controller. Since by assumption the identifier is unique, this means that every controller in the array will agree which one is the master, and which are slaves. There are many other ways in which a master controller may be determined, with the only criterion being that the result must be unique and agreed upon by every controller in the array.

In principle it is possible to assemble an array in which only some of the battery modules are configured to perform the method steps described in Figure 3. In this case, the only requirement is that the battery modules which are not configured to participate are instead configured to receive commands from the controller which is configured to participate, and which is identified as a master controller. That is, battery modules which are not configured to participate in the self-arbitration process will be deemed to be slave modules, wherein the only requirement is that they are configured to respond to commands in the same way that a slave module does.

Further, the array itself may have a controller, which can participate in the selfarbitration. It may be desirable to make this controller the master controller by default, for example by forcing the controller serial number to be 0, following the above example, which uses the lowest serial number as the master controller.

Moreover, the process depicted by Figure 3 may be repeated. For example, the array may be configured to detect the addition or removal of a battery module from the array, and trigger the self-arbitration process of Figure 3 in response to this. This ensures that in the event that a battery module is removed which includes the master controller, the array can easily and quickly determine a new master controller, and continue to operate. Similarly, the array may periodically perform this process, or perform it at random or semi-random intervals.

Once a master controller has been determined by the array, the master controller performs various other functions in relation the operation of the array. For example, a master controller may be responsible for determining the amount of current required from a charger, in order to charge the battery modules of the array. Similarly, the master controller may perform load balancing between the battery modules of the array, to ensure that the output current and/or voltage match the intended values, and that each battery module in the array is delivering power at a rate which will cause all battery modules to run out of charge at the same time. A further process which the master module may control is that of determining the arrangement of the battery modules in the array. As shown in Figure 2, there may be a plurality of threads connected to each other in parallel, each thread having a plurality of battery modules 200 connected in series with one another. Clearly in the event that the arrangement is known in advance, it is simple to calculate the expected output current and voltage, if the voltage and current of each battery module is known (this information can, for example, be reported to a master controller by the controller in each module, communicating via the bus 214).

However, in the event that the arrangement of the modules is not known, then it can be difficult to calculate the output voltage and/or current of the array - an important parameter for determining the practical application of the array. Similarly, the current required to charge an array, and the current to direct along each thread is strongly dependent on the arrangement of the battery modules in the array. In order to charge the modules in the array as quickly as possible, while ensuring safety by preventing overcharging. Therefore, the array may be configured to determine the arrangement of the battery modules relative to one another. This may be performed by the master controller, as determined above, or it may be determined by any one of the controllers. As mentioned above, in the case where there is a master controller, this may be a controller which is part of the array, rather than, for example, the controller which is part of the battery module as shown in Figure 1.

In order to understand the process for determining the arrangement of the battery modules in the array, consider Figure 4A. In this figure, thirteen battery modules 400a-m are shown spread between four strings. As shown, a first string comprises four modules 400a-d, a second string comprises three modules 400e-g, a third string comprises four modules 400h-k, and a fourth string comprises two modules 400l-m. It will be understood that this arrangement is merely illustrative of the possible arrangements of battery modules in an array, and that any number of strings is possible, each string comprising one or more battery modules. Moreover, the array may be structured in such a way that additional battery modules can be added to any of the strings at any time, or even added to create a new string. In such systems, as described above, it is important to be able to determine the arrangement of each battery module relative to the others. In other words, it is important to be able to determine which battery modules are connected in series with each other (in a string). Note that for simplicity, no bus is shown in Figure 4A. However, the modules of the array may nonetheless be configured to communicate with one another, e.g. via a bus (not shown), or by wireless communications, for example.

One approach for detecting the arrangement of battery module sin the array is shown in Figure 4B. This figure is similar to Figure 4A, in that a plurality of battery modules 400a-e (in this example there are five battery modules, although any number is possible) are connected together in a plurality of strings (in this example two strings, although as described above, any number is possible), with each string having one or more battery modules 400 connected together in series. Each module may communicate with one another via a bus 414. In this example, the battery array 401 is provided with a predetermined number of bays, in this case six bays, into which a battery module may be inserted.

Each bay is provided with a bypass, for example a switch 416. In the event that a bay is occupied, the switch is left open circuit 416a, so that the battery module terminals 412 are not shorted out. When a bay is unoccupied, the switch may be closed, in order that the other batteries in that string maintain connectivity to the output terminals of the array 422. It is important that it is not possible to close every switch in a given string simultaneously, as this would short out other strings in the array. Compliance with this requirement may be implemented electronically, mechanically, or in any other way known to those in the art. Similarly, as discussed above, it is important that the switch of a given bay is not closed when a battery module is occupying that bay. This may be ensured by physical design of the battery modules, which can be designed to force a break-before-make connection in the sense that the switch is opened prior to mounting the module in a bay, and inhibiting (for example preventing) closure of the switch while a module is occupying the bay.

Using this arrangement, a controller need only have rudimentary knowledge of the array, in order to determine the arrangement. For example, if the controller is provided with a map of the bays of the array (that is, it knows that there are m parallel strings, and it further knows how many bays are in each string), and the switches are arranged to communicate whether they are open or closed, then the controller can immediately determine how many strings are occupied, and which bays of which strings are occupied. This is enough to determine at a basic level the arrangement of the battery modules. More detailed information can be provided to the controller if each switch is also configured to provide information relating to its physical position in the array. A more detailed determination may be made by providing the battery modules and/or the bays with a means for allocating an identifier to the battery module. This may be fixed to the bay, so that any battery module mounted in such a bay automatically takes on this identifier. The controller is then arranged to associate this identifier with a particular battery module’s battery information, for example state of charge, output voltage, current etc., all of which can be communicated to the controller, for example via the bus. A further development of this idea is that each battery module is provided with a DIP switch, or other manually configurable identification device. When a battery module is mounted in the array, the identification device can be set to a unique value indicative of the battery module’s position in the array. For example, a first portion of the identification value could represent the string number, and a second portion of the identification value could represent the position in the string of the battery module. This is effectively equivalent to assigning an (x, y) coordinate to each battery in the array, and consequently can be extended indefinitely to map arrays of arbitrary size. Alternatively, each battery module could be provided with two DIP switches, one for the x coordinate (e.g. string number), and one for the y coordinate (e.g. position in string).

Note that mapping the array in this way does not require that the battery modules are actually arranged in a rectilinear manner in physical space. It simply means that different strings may be counted using one variable (e.g. x), while position in the string may be counted using another variable (e.g. y). Such a system allows for an easy determination as to whether any two battery modules are in series with one another or not, in this example by comparing their x-coordinates. In many cases it is not possible to detect the actual physical position of a battery module in a string, as swapping two modules in the same string with one another results in an electrically equivalent circuit. Therefore, in this example the y coordinate may not correspond strictly to physical location of battery modules. Instead, battery modules in a string may be labelled sequentially in the order that they are determined to be in a particular string. Similarly, swapping entire strings with one another results in an electrically equivalent circuit, so in this example the x-coordinate of a particular string may not correlate with the physical location of that string. Instead, strings may be labelled sequentially in the order that they are discovered to be an independent string.

In determining the arrangement of the battery modules, it is not necessary that the position of a given module in the string is known. For the present purposes, it is only necessary to determine which battery modules are in series with one another. However, position in a string may provide useful information in the event that a fault is detected (discussed in further detail below), so that a user can be alerted, and advised not only that a battery module requires replacement or attention, but the physical location of that module.

Note that since each position in the grid of (x, y) coordinates formed in this way can comprise at most one battery module, the (x, y) position of any given battery module can serve as a unique identifier for use in the method illustrated in Figure 3. By default, for example, the master controller could be determined by the following rules: (i) Find the controller for which x + y is lowest; and (ii) In the event that more than one controller has equal lowest value of x + y, select from these controllers the controller having the lowest x value.

The above method requires that the battery modules are all configured correctly when they are mounted in the array. In the event of user error for example, the array may be configured to detect, e.g. a duplicate identifier, and signal an error message. However, such an approach requires user intervention. As is illustrated in Figure 5, the present disclosure provides a method for the array to determine the arrangement of the battery modules which make up the array.

The first step 560 is that the master controller (which may be a controller which is part of a battery module, or a dedicated controller, for example) selects a battery module in the array, and decouples the battery module from the array. This may be achieved, for example, by communicating with the selected module (e.g. via a bus), and sending a request to the selected battery to decouple. Upon receiving such a request, the selected battery module responds by decoupling itself from the array. In this context, by decoupling, what is meant is that the battery module breaks the connection between itself and the rest of the array, e.g. by activating a circuit breaker or electronic switch. When a battery module has been decoupled in this way, it is as if the battery module is not present in the array from an electrical connectivity perspective. For the avoidance of doubt, a battery module which has been decoupled in this way may still be able to communicate with the other battery modules in the array, for example via a bus. Additionally, in the event that the array is provided with by passes, as shown in Figure 4B, when a battery module is decoupled in this way, the switch will not be closed to compensate for the decoupling.

The second step 562 in Figure 5 comprises the master controller receiving a determination reading from each of the battery modules in the array. As is described in more detail below, this may be a current reading or a voltage reading, or indeed any reading which will allow the master controller to determine the arrangement of the modules in the array.

The final step 564 in Figure 5 is to determine the arrangement of one or more modules in the array, based on the readings taken in step 562. This determination may optionally be made by comparing the readings received in step 562 with earlier values, or it may be based solely on the readings themselves. These steps may be repeated as often as necessary to determine the position of each battery module in the array, or at least to determine which battery modules in the array are connected in series in a single string.

Figure 6 provides an example of the steps which may occur when current measurements are used to determine the arrangement of the battery modules in the array. This method relies on the fact that battery modules connected in series with one another will all register zero current if any one of them is decoupled. This effect is similar to that seen in fairy lights, which are traditionally wired together in series; when one bulb breaks, the whole string of lights goes out, since no current can flow.

The first step 670 in Figure 6 is once again to select and decouple a battery module from the array, similar to the situation described in Figure 5.

The next step 672 in Figure 6 is to receive a current measurement from each battery module in the array.

The final step 674 in Figure 6 the current measurements are analysed, and any readings of zero are determined to be received from battery modules which are in series with the selected battery module. Conversely, any non-zero current readings iRs-ijreceived from battery modules are determined to belong to battery modules which are not in series with the selected battery module. That is to say, any non-zero readings must belong to battery modules which are in parallel with the selected battery module (or in a different string). Each non-zero reading may come from battery modules which are in series with each other in a parallel string, or they may come from battery modules which are arranged in a plurality of other strings.

Once the battery modules which are in series with the selected module have been determined, the process can be repeated by selecting a second battery module, and repeating the steps. This can be performed as a check by selecting as a second module one which was previously determined to be in series with the first module, or the second module may be one which was determined to be in parallel with the originally selected module, in order to determine which modules are connected in series with the second module. In this way, repeating the steps allows for the position of each module in the array to be mapped out.

In order to ensure that the location of every module is determined, the process may be repeated once for each module in the array. Alternatively, it is possible to make this determination by repeating the process m times, where m is the number of strings in the array, if each time the process is repeated, a module which is not in series with any previously selected module is chosen. In fact, in the special case where the final module to be selected is the only module in its string, the minimum number of cycles of the process is m-1.

In the method of Figure 6, it is possible that the received current readings are zero for a different reason, for example the current measuring device, or the cells of the battery module may be faulty. Therefore, it is an optional feature of this method to receive initial readings prior to decoupling the selected battery module from the array. This initial reading is then compared with the determination reading to determine whether any of the battery modules are reading zero, even if they were not reading zero before the process began.

It is also possible to determine the arrangement of modules in the array relative to one another using voltage measurements. In this case, the method is a little more complicated, but only requires a voltage measurement in a single location: the voltage output by the array as a whole.

The process can be thought of as a two stage process. The first stage determines how many strings there are in the arrangement of the array, and the second determines which of these are connected in series with one another.

Figure 7 [RS2]illustrates a method for carrying out the first stage of the method. In the figure, the first step 670 is to set a counter, n to a value of 1. This counter is used to determine the number of strings in the array. It is initialised at 1, because as will become clear below, the method involves incrementing n until the number of strings has been determined. Due to the details of the method, the number of strings determined by the method could be too high unless n is initialised at 1.

The next step 672 is to select a combination of n modules, and decouple those modules from the array. In the case of n = 1, this involves selecting a single module.

Next, at step 674, a measurement is made of the total voltage output, Vtot, from the array. If this voltage is zero, then the module(s) which has been disconnected has completely broken the circuit. In general if n modules have been decoupled to achieve this, then the number of parallel strings in the array must be n or less. For example, when there is only one string in the array, then decoupling any module in the array will cause the total output voltage, Vtot of the array to drop to zero, since any decoupling any module will break the circuit. Clearly, however, decoupling a second, third, fourth, etc. module will not change this situation, and Vtot will remain zero. In general, when the array comprises n parallel strings, decoupling a single module from each string will cause Vtot to drop to zero. Any further decoupling of modules will not affect this result. For this reason, a value of n which gives Vtot = 0 is an upper bound on the number of strings in the array, and consequently the number of strings in the array may be less than a particular value of n. This is why the method initialises the value of n at 1 and then counts upwards; the first value of n will be the lowest possible value, and will therefore inherently be equal to the number of strings in the array.

In the event that Vtot is determined to be zero, then the number of strings in the array is determined to be n at step 676.

In the event that Vtot is not equal to zero, the method proceeds to step 678 in which a determination as to whether every combination of n modules has been tested is made. In the simple case of n= 1, this simply means determining whether each individual module has been decoupled in turn. For larger values of n, this step requires that each possible combination of n modules out of the number of modules in the array has been decoupled.

In the event that not every combination of modules has been tested, the method reverts to step 672, and a new combination of n modules is selected, and the process repeats.

In the event that every combination of n modules has been tested in this way, the value of n is incremented by one, and the process is repeated using the new value of n until a combination of modules is found which causes Vtot to be zero, at which point the current value of n is determined to be the number of strings in the array, and the process finishes.

In some cases, it the process may include measuring the total output voltage prior to initiating the method described above, and shown in Figure 6. In particular, if the total output voltage is zero before the method starts, then it will not be possible to determine the number of strings as described above. In this case, the method will not be run, and instead an error message can be issued.

Turning now to Figure 7, there is shown a further method of using the information determined in the method of Figure 6 to further determine which modules are connected to one another in series in strings. The method is based on the idea described above that a single string will not output any voltage if any one of the modules in that string is decoupled.

The method of Figure 7 begins at step 780, in which a known combination of n modules which when decoupled results in the total output of the array, Vtot, to be zero. Such a combination will be known, for example, if the method of Figure 6 has been carried out, as it will be the final combination selected at step 672.

In general, the following steps simply swap modules by recoupling one module from the known combination with other modules, and note the effect of such a swap. For example, step 781 selects a module from the known combination of modules. This module will be used for swapping purposes.

In step 782, the selected module (the first module) is recoupled, while a second module, which was not part of the original known set of modules is decoupled.

At step 783, a determination is made as to whether Vtot, is zero. If it is, then decoupling the second module is electrically equivalent to decoupling the first module. The only way for this to be true is if the first and second modules are electrically connected together in series. That is to say, they are part of the same string. In the event that Vtot, is zero, therefore, a determination is made that the first and second modules are coupled together in series at step 784. On the other hand, if Vtot, is not zero, then decoupling the second module is not electrically equivalent to decoupling the first module. The only way for this to be true is if the first and second modules are electrically connected together in parallel. That is to say, they are part of different strings. In the event that Vtot, is not zero, therefore, a determination is made that the first and second modules are not coupled together in series at step 785.

In either case, the process proceeds to step 786 in which a determination is made as to whether every second module has been tested in this way. That is to say, whether each module that was not part of the original set of n modules known to result in the total output of the array, Vtot, to be zero combination when decoupled together, has been tested to determine which modules it is equivalent to.

If this is not the case, and there are other second modules to be tested, then the process returns to step 782, and using the same first module, repeats the process, selecting a different second module, which is then categorised as described above, based on whether decoupling the second module is electrically equivalent to decoupling the first module.

On the other hand, if at step 786 the result is that each of the second modules has been tested, then a further determination is made at step 787 regarding whether all first modules have been tested in this way. If they have, then the method ends, because necessarily each module has been tested, and therefore the array has been mapped out in full.

On the other hand, if each first module has not been tested, then the process reverts back to step 781, and selects a new first module, and the process repeats as described above, using the newly selected first module as a basis for swapping.

It will be appreciated in the context of the present disclosure that determining the electrical equivalence of decoupling pairs of first and second modules may be performed in any order, as long as the method continues until all modules have been determined to be part of one of the strings. In addition, it may be the case that each module can be mapped to a string before the process reaches the end at step 788. In this case, there may be a step which detects that the array has been fully mapped, and ends the process at that point.

Turning now to Figure 8, there is shown a method for error detection. As explained above, the master controller may issue a charging demand to a charging unit attached to the array. This is step 890 in Figure 8. A charging demand typically specifies a charging current, and a charging voltage. If the master controller is aware of the layout of the array, it can determine the voltage based on the number of modules in each string, and it can determine the current based on the number of strings. The specific design of the modules, including the number of cells and type of cells it comprises will also play a part in determining how much voltage and current is required. In short, the purpose of selecting a specific voltage and current combination is that each module receives a sufficient voltage and current to charge it. In practice, while higher currents result in faster charging, there are safety limits which mean that currents may be limited. The controller is aware of these limits for the modules in the array, and selects a charging current for the array as a whole based on the maximum allowable charging current, and its knowledge of the arrangement of the modules in the array. For example, when there are n strings in the array, the current is split between them, and each receives 1/n of the total current. Therefore, two arrays comprising the same number of modules may have vastly different maximum charging currents, due to the modules being electrically connected in different ways between the two arrays. The total current demanded from the charging unit is calculated by the controller so that the current flowing through the battery module with the lowest maximum safe charging current is at that maximum value.

Similarly, the total voltage supplied will be divided between each battery module in a string which may be viewed as a potential divider. For example, if all of the modules of a string are at the same state of charge, when there are m modules in a string, each will receive Mm of the voltage supplied, and the total supplied voltage can be increased above the maximum safe supply voltage of each individual battery module. The controller can calculate the supplied voltage in order to make a demand by taking the arrangement of the array into account, and selecting a voltage that means that the battery module with the lowest maximum safe voltage has that maximum safe voltage across it.

Next at step 892, a value of voltage and/or current calculated in step 890 is compared with a measured value.

As the controller has calculated the charging demand based on its knowledge of the arrangement of the array and the operating parameters of the battery modules, the measured value and the calculated value should match. In the event that they do not match, this is indicative of an error. Therefore in step 894, when the measured value and the calculated value do not match, a determination is made that an error has occurred.

This error may be the result of one of several problems with the array. For example, it is possible that although a battery module is electrically connected to the array, it may not be in communications contact with the master controller, for example because the communications link has not correctly connected to a communications bus. Therefore, while it will charge and discharge along with the other battery modules in the array, the master controller will not know about the battery module, and will not account for it when making a charging demand. This in turn means that when the current and/or voltage is measured and compared with the calculated value, the measured value will be lower than the calculated value, as there is an extra module being charged.

The reverse situation, in which the battery module correctly makes a communications connection, but is not correctly electrically connected, will be picked up in the methods for determining the arrangement of battery modules in the array, described above. In this case, the methods for determining an arrangement of the modules in the array can further include detecting this type of error.

Another possible source of error could be if the current and/or measurement is itself faulty. In this case, the master controller could determine the expected current and/or voltage at several points in the array, and compare it with measurements. In particular, the current in each string should be equal, so if one reading in a string is significantly different from the others, this could be an indication that there is a fault with the measurement apparatus of that battery module. Similarly, the voltage across an entire string should be equal for all strings, and any string measuring a significantly different voltage to the others (as determined by summing the voltages across each module in a given string) could be an indication of an error in the voltage measurement of a particular battery module in that string.

Moreover, if a series of measurements around the array all result in readings which do not match the calculated readings, then this could be an indication that the charging unit itself is malfunctioning.

In the event that an error occurs, the controller may be further configured to alert a user to the error. In particular, it may further provide an indication of the type of error and the likely cause, for example, if the measured readings are lower than the calculated values, then the controller may propose that one or more battery modules have not made a communications link correctly, and may suggest to a user that checking the communications connections could solve the problem.

Additionally or alternatively, the controller may further send a message to the charging unit to stop the charging process. This is a safety feature to prevent unsafe charging from occurring. Alternatively, in some cases, the master controller may simply send a network message with a revised charging demand to the charging unit, to bring the measured values closer to the maximum safe values for the array.

The processes of Figures 5, 6, 7 or 8 may be repeated at selected intervals, in order to ensure that an accurate and up to date arrangement of the battery modules of the array is available for use in all calculations. For example, one or more of the controllers of the array may be configured to detect the addition or removal of a battery to/from the array, and to request that the arrangement be determined again (or simply trigger the determination process itself). Alternatively, the process could be carried out periodically at regular intervals or on detection of a shut down or switch on of the array.

In addition, the detection process may be carried out in addition to some of the other features described herein. For example, the master controller may be selected according to the self-arbitration methods described above. Moreover, the battery modules may be provided with additional location information, as described above in relation to DIP switches, to allow a precise physical location of the battery module in the array to be supplied to a user, in the event that a fault is detected, and repair, replacement or other attention is required by a user in relation to a specific battery module of the array.

In each of the methods detailed in Figures 5, 6, 7 or 8 the selection of battery modules may be performed in a similar way to the selection of a master controller. That is by considering unique identifiers associated with each battery module or a controller therein. The first battery module to be selected may then be, for example, the battery number with the numerically lowest unique identifier, e.g. serial number.

Turning now to Figure 9, there is shown a system 930 for mounting a plurality of battery modules. The system comprises a series of bays 932, which are shaped and sized to accommodate the battery modules described herein. Optionally, connectors for the battery modules may be provided (not shown), which allow the battery modules to connect to battery modules in adjacent bays. Additionally, the mounting system may include a controller to perform the methods set out above. In this case the controller for the system may be chosen to be a master controller by default.

It will be appreciated in the context of the present disclosure however that the activities and apparatus outlined herein, such as the operation of the controller 102 illustrated in Figure 1 and described elsewhere in the specification, may be implemented with any kind of logic such as assemblies of logic gates or other kinds of programmable logic such as software and/or computer program instructions executed by a processor. Other kinds of programmable logic also include programmable processors, programmable digital logic (e.g., a field programmable gate array (FPGA), an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM)), an application specific integrated circuit, ASIC, or any other kind of digital logic, software, code, electronic instructions, flash memory, optical disks, CD-ROMs, DVD ROMs, magnetic or optical cards, other types of machine-readable mediums suitable for storing electronic instructions, such as software and firmware, or any suitable combination thereof.

With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. It will be appreciated however that the functionality need not be divided in this way, and should not be taken to imply any particular structure of hardware other than that described and claimed below. The function of one or more of the elements shown in the drawings may be further subdivided, and/or distributed throughout apparatus of the disclosure. In some embodiments the function of one or more elements shown in the drawings may be integrated into a single functional unit.

The above embodiments are to be understood as illustrative examples. Further embodiments are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

In some examples, one or more memory elements can store data and/or program instructions used to implement the operations described herein. Embodiments of the disclosure provide tangible, non-transitory storage media comprising program instructions operable to program a processor to perform any one or more of the methods described and/or claimed herein and/or to provide data processing apparatus as described and/or claimed herein.

Claims

1. A battery module controller configured to cooperate with other similar battery module controllers to provide a self-organising array of battery modules, each battery module comprising at least one energy storage cell, the battery module controller comprising a unique identifier and being configured to: (i) send a network message comprising its unique identifier; (ii) receive one or more network messages each comprising a unique identifier of a respective other controller of a battery module in the array; (iii) identify, based on the received one or more messages, one of the controllers of the array as a master controller.

2. The battery module controller of claim 1, wherein, in the event that the battery module controller is designated as the master controller, to: (iv) determine a charging demand for charging the array of battery modules, and to send a network message comprising the charging demand to a charger coupled to the array.

3. The apparatus of claim 1 wherein the master controller is configured to control a diagnostic process of the array.

4. The apparatus of any of claims 1 to 3, wherein the array is arranged into one or more strings of battery modules, wherein each string comprises one or more battery modules electrically connected to one another in a series arrangement, and wherein any given string is connected to any other strings in a parallel arrangement, and wherein the diagnostic process comprises determining the arrangement of the electrical connections between battery modules in the array.

5. The apparatus of claim 4 as dependent on claim 2 wherein the charging demand comprises at least one of a current request and a voltage request.

6. The apparatus of claim 5, wherein the current and/or voltage request is based at least in part on the electrical arrangement of the battery modules.

7. The apparatus of claim 5 or 6, wherein the voltage request is based in part on the number of battery modules in the strings.

8. The apparatus of any of claims 5 to 7, wherein the current request is based on the number of strings.

9. The apparatus of any of claims 5 to 8, wherein the charging demand is based in part on received information relating to the temperature of one or more cells or battery modules in the array.

10. The apparatus of any of claims 4 to 9 wherein determining the electrical arrangement comprises sending a network message comprising a command configured to cause a selected battery module controller to modify the impedance of an electrical current path through the battery, for example by disconnecting the electrical current path.

11. The apparatus of claim 10 wherein the electrical arrangement is determined based on currents and/or voltages sensed while the impedance of the current path through the selected battery is modified, for example while said module is disconnected.

12. The apparatus of any of claims 2 to 10 wherein the diagnostic process includes detection of faults in the array, for example wherein the fault detection includes: (i) determining a charging current required to result in a specified current through a portion of the array; (ii) comparing a current measured through the portion of the array with the specified current; and (iii) in the event that there is a discrepancy between the measured current and the specified current, determining that a fault has occurred.

13. The apparatus of claim 12, wherein the fault detection includes: (i) determining a charging voltage required to provide a specified voltage across a portion of the array; (ii) comparing a voltage measured across the portion of the array with the specified voltage; and (iii) in the event that there is a discrepancy between the measured voltage and the specified voltage, determining that a fault has occurred.

14. The apparatus of claim 12 or 13, wherein the portion of the array is the battery module comprising the master controller.

15. The apparatus of any of claims 10 to 14 wherein, in the event that the controller determines that a fault has occurred, the master controller is further configured to: (i) adjust the requested current; and/or (ii) abort the charging process; and/or (iii) transmit an error message.

16. The apparatus of claim 11, or any preceding claim as dependent thereon wherein modifying the impedance comprises applying a time varying adjustment.

17. A battery module controller configured to determine the electrical arrangement of a plurality of battery modules, wherein the electrical arrangement comprises series and/or parallel electrical connections of said battery modules and each battery module comprises at least one energy storage cell, the battery module controller comprising a unique identifier and being configured to: (i) send a network message comprising its unique identifier; (ii) receive a plurality of network messages each comprising a unique identifier of a respective other controller of a battery module of the plurality of battery modules; (iii) identify one of the controllers of the array as a master controller, and, in the event that the battery module controller is designated as the master controller, to (iv) send and receive network messages comprising unique identifiers of the other controllers to determine the electrical arrangement of battery modules in the array.

18. The battery module controller of claim 17, wherein identifying one of the controllers as a master controller comprises identifying based on the received plurality of network messages in step (ii).

19. The apparatus of claim 17 or 18 wherein determining the electrical arrangement comprises sending a network message comprising a command configured to cause a selected battery module controller to disconnect its battery module from the plurality of battery modules, and determining the electrical arrangement based on voltages sensed while the selected battery module is disconnected.

20. The apparatus of any of claims 17 to 19 further configured so that, in the event that the battery module controller is designated as the master controller, the battery module controller determines a charging current required to charge the plurality of battery modules based on the electrical arrangement.

21. The apparatus of any of claims 17 to 20 further configured so that, in the event that the battery module controller is designated as the master controller, the battery module controller determines a charging voltage required to charge the battery modules based on the electrical arrangement.

22. The apparatus of any of claims 20 or 21, wherein the charging demand is based in part on received information relating to the temperature of one or more cells or battery modules in the array.

23. The apparatus of any of claims 17 to 22, wherein the master controller is configured to control a diagnostic process of the array.

24. The apparatus of claim 23, wherein the diagnostic process includes detection of faults in the plurality of battery modules.

25. The apparatus of claim 24, wherein the fault detection includes: (i) determining a charging current required to result in a specified current through a specified battery module; (ii) comparing a current measured through the specified battery module with the specified current; and (iii) in the event that there is a discrepancy between the measured current and the specified current, determining that a fault has occurred.

26. The apparatus of claim 24 or 25, wherein the fault detection includes: (i) determining a charging voltage required to provide a specified voltage across a specified battery module; (ii) comparing a voltage measured across the specified battery module with the specified voltage; and (iii) in the event that there is a discrepancy between the measured voltage and the specified voltage, determining that a fault has occurred.

27. The apparatus of claim 25 or 26, wherein the specified battery module is the battery module comprising the master controller.

28. The apparatus of any of claims 24 to 27 wherein, in the event that the controller determines that a fault has occurred, the master controller is further configured to: (i) adjust the requested current; and/or (ii) abort the charging process; and/or (iii) transmit an error message.

29. The apparatus of any of claims 17 to 28, wherein the master controller is configured to perform the (i) sending, (ii) receiving and (iii) identifying in the event of addition or removal of a battery module of the array.

30. The apparatus of any of claims 17 to 29 configured to detect addition or removal of a battery module based on network messages received from other of the battery modules.

31. The apparatus of any of claims 17 to 30 wherein the network messages comprise controller area network (CAN) messages.

32. The apparatus of any of claims 17 to 31 configured to perform the (i) sending, (ii) receiving and (iii) identifying steps at selected intervals.

33. The apparatus of any of claims 17 to 32, wherein the unique identifier is based on a serial number of the controller.

34. The apparatus of any of claims 17 to 33 further comprising the at least one energy storage cell.

35. A battery module comprising the apparatus of any preceding claim.

36. A system comprising a plurality of battery modules according to claim 35, each provided in a first housing shaped for installation into a second housing, wherein the second housing comprises a plurality of bays each adapted for retaining one of said battery modules and arranged to permit the battery modules to be connected together in at least one of series and parallel electrical arrangement.

37. The system of claim 36 further comprising a serial BUS arranged to permit each battery module to broadcast network messages to each other of the plurality of battery modules.

38. A battery module for use in a battery array, the battery module configured to determine the electrical arrangement of battery modules mounted in the array by sending a command to at least one other battery module of the array to cause disconnection of said battery module, and by obtaining a test voltage and/or test current signal from battery modules connected to the array while the at least one other battery is disconnected.

39. A battery module according to claim 38 configured to obtain a preceding current and/or preceding voltage signal from each of the battery modules connected to the array prior to disconnection of the at least one other battery.

40. The battery module of claim 38 or 39 wherein the electrical arrangement is determined based on a test voltage and/or test current signals and the preceding current and/or preceding voltage signals.

41. A battery module according to claim 38 or 39, wherein the controller is configured to perform the process steps set out in claims 1 to 15 to determine whether the controller is designated master controller, and only to perform the steps of claims 17 to 34 in the event that the controller is designated master controller.

42. A battery module for use in a battery array configured to participate in the determination of the arrangement of battery modules mounted in the array, relative to one another, the battery comprising: at least one cell; and a controller coupled to the cells of the battery module, and configured to: (i) provide electric current data from the battery module; and (ii) respond to a request to decouple the battery module from the array by decoupling the battery module from the array.

43. A battery module according to claim 42, wherein the electric current data is provided at selected intervals.

44. A battery module according to claim 42 or 43, wherein the electric current data is provided in response to a request.

45. A battery module according to any of claims 41 to 43, further configured to provide on request an initial reading from the battery module prior to performing step (i)·

46. A battery module according to any of claims 42 to 45, wherein the controller is further configured to perform the communication, reception, generation and identification process of claims 1 to 15, and to determine that the controller is not a master controller, prior to performing the steps of claims 42 to 45.

47. A battery module according to any of claims 21 to 26, wherein the first and second readings are current readings.

48. A mounting system for receiving a plurality of battery modules, and connecting the battery modules electrically to one another, the mounting system having one or more bays, each bay arranged to receive a battery module; wherein the one or more battery modules are arranged in the array and are connectable together in a combination of parallel and series arrangements, according to the current and voltage output requirements of the array.

49. A mounting system according to claim 48, wherein each bay has electrical connections to at least one other bay, so that the bays are connected together to form a series of strings, each string being connected in parallel to each other string, and each bay in each string being connected in series with each other bay in the same string.

50. A mounting system according to claim 49, wherein each bay has an electrical bypass for maintaining connectivity in the event that a given bay is unoccupied by a battery module.

51. A controller for the mounting system of any of claims 48 to 50, wherein the controller is arranged to provide the functionality of the controller of claims 1 to 33.

52. The controller of claim 51, wherein the controller is arranged to be a master controller.

53. An array of battery modules, comprising: one or more battery modules according to claims 34 to 46 and the mounting system of any of claims 48 to 50, and optionally the controller of claim 51 or 52.

54. A method of self-configuration for a plurality of controllers in an array of battery modules, the method comprising: (i) each controller sending a network message comprising a unique controller identifier; (ii) each controller receiving a network message comprising unique controller identifiers from the each other controller in the array; and (iii) identifying one of the controllers as a master controller,

55. The method of claim 54, wherein identifying one of the controllers as a master controller is based on the received network messages.

56. The method of claim 54 or 55, wherein the method further comprises: (iv) the master controller determining a charging demand for charging the array of battery modules, and sending a network message comprising the charging demand to a charger coupled to the array.

57. The method of any of claims 54 to 56, further comprising the master controller controlling diagnostic processes of the array.

58. The method of any of claims 54 to 57, wherein the array is arranged into one or more strings of battery modules, wherein each string comprises one or more battery modules electrically connected to one another in a series arrangement, and wherein any given string is connected to any other strings in a parallel arrangement, and wherein the diagnostic process comprises determining the arrangement of the electrical connections between battery modules in the array.

59. The method of claim 58 as dependent on claim 56, wherein the charging demand comprises at least one of a current request and a voltage request.

60. The method of claim 59, wherein the current and/or voltage request is based at least in part on the electrical arrangement of the battery modules.

61. The method of claim 59 or 60, wherein the voltage request is based in part on the number of modules in the strings.

62. The method of any of claims 59 to 50, wherein the current request is based on the number of strings.

63. The method of any of claims 58 to 62 wherein determining the electrical arrangement comprises sending a network message comprising a command configured to cause a selected battery module controller to disconnect its battery module from the array, and determining the electrical arrangement based on currents or voltages sensed while the selected battery module is disconnected.

64. The method of any of claims 56 to 63 wherein the diagnostic process includes detection of faults in the array.

65. The method of claim 64, wherein the fault detection includes the master controller: (i) determining a charging current required to result in a specified current through a portion of the array; (ii) comparing a current measured through the portion of the array with the specified current; and (iii) in the event that there is a discrepancy between the measured current and the specified current, determining that a fault has occurred.

66. The method of claim 64 or 65, wherein the fault detection includes the master controller: (i) determining a charging voltage required to provide a specified voltage across a portion of the array; (ii) comparing a voltage measured across the portion of the array with the specified voltage; and (iii) in the event that there is a discrepancy between the measured voltage and the specified voltage, determining that a fault has occurred.

67. The method of claim 65 or 66, wherein the portion of the array is the battery module comprising the master controller.

68. The method of any of claims 64 to 67 wherein, in the event that the controller determines that a fault has occurred, the master controller is further configured to: (i) adjust the requested current; and/or (ii) abort the charging process; and/or (iii) transmit an error message.

69. The method of any of claims 54 to 68, wherein the unique controller identifier includes a serial number unique to each controller.

70. The method of claim 69, wherein the predetermined rules include ranking the controllers by serial number.

71. The method of any of claims 54 to 70, wherein the method is repeated at selected intervals, to update the identification of master the controller.

72. The method of any of claims 54 to 71, wherein the method includes monitoring for the addition or removal of a controller, and triggering execution of the method to update the identification of the master controller in the event that such an addition or removal is detected.

73. The method of claim 72, wherein the detection of addition or removal of a battery module is performed by exchanging controller area network (CAN) messages with battery modules in the array.

74. A method for determining the arrangement of battery modules in an array, relative to one another, each battery module comprising one or more cells and a controller, the method comprising the steps of: (i) selecting a battery module, and decoupling the selected battery module from the array; (ii) receiving a determination reading from each battery module in the array; and (iii) determining the arrangement of the battery modules in the array based on the determination readings received.

75. The method of claim 74, further comprising receiving an initial reading from each battery module in the array prior to step (i); and comparing the initial and determination readings for each battery module as part of the determination of which battery modules are coupled in series with the selected battery module.

76. The method of claim 74 or 75, wherein the determination and optionally the initial readings comprise current readings.

77. The method of any of claims 74 or 76, further comprising repeating the method by selecting a second battery module, to determine which battery modules are coupled in series with the second battery module.

78. The method of any of claims 74 to 77, further comprising repeating the method by selecting a different battery module each time, and determining which battery modules are coupled in series with the selected battery module, until a determination has been made as to which groups of battery modules are in series with one another, for each battery module in the array.

79. The method of any of claims 74 to 78, further comprising repeating the method steps so that they are carried out a total of m times, where m is the number of parallel strings of battery modules to determine which groups of battery modules are in series with one another for each battery module in the array.

80. The method of any of claims 74 to 79, further comprising the method steps of any of claims 54 to 73.

81. The method of claim 80, wherein the method steps of claims 54 to 73 are performed prior to the method steps of claims 74 to 79, and wherein the method steps of claims 74 to 79 are performed by the master controller determined by the method of any of claims 54 to 73.

82. The method of any of claims 74 to 81, wherein the method is repeated, selecting a second battery module, wherein the second battery module is not one which was determined to be in series with the battery module selected in step (i) of claim 74.

83. The method of any of claims 74 to 82, wherein the determination and optionally the initial readings comprise voltage readings.

84. The method of claim 83, wherein the method further includes calculating the total voltage output by the array, based on the determination of which battery modules are coupled to one another in series and the voltage readings of each battery module.

85. The method of claim 73 or 84, wherein the voltage at one or more points in the array is calculated from the determination of which battery modules are coupled to one another in series and the voltage readings of each battery module, and compared with a measured voltage at the one or more points.

86. The method of any of claims 74 to 85, wherein the current into or out of one or more cells in the array is calculated from the determination of which battery modules are coupled to one another in series and the current readings of each battery module, and compared with a measured voltage at the one or more points.

87. The method of claim 85 or 86, wherein the comparison of calculated values with measured values is used to detect faults.

88. The method of claim 87, wherein a fault with an individual current measurement is detected by comparing current measurements between battery modules determined to be in series with one another.

89. The method of claim 87 or 88, wherein voltages across sets of battery modules connected in parallel with one another are compared as part of fault detection.

90. The method of claim 85 or 86, wherein the comparison of calculated values with measured values is used to determine battery modules which require replacement.

91. The method of claim 90, wherein the method further includes alerting a user that one or more battery modules require replacement.

92. The method of claim 91, wherein the method further includes determining an approximate physical location of the one or more battery modules which require replacement, and providing this information to a user.

93. The method of any of claims 74 to 92, wherein the method is operated by the master controller determined by the method of any of claims 55 to 62.

94. The method of any of claims 74 to 93, wherein the method includes monitoring the array to detect the addition or removal of a battery module or a controller, and triggering the method in the event that such an addition or removal is detected, triggering an update to the identification of master and slave controllers.

95. The method of any of claims 74 to 94, wherein a master controller requests current for charging the battery modules from a current source external to the array, the amount of current requested being determined by the determined arrangement of the battery modules in the array.

96. The method of claim 95, further comprising determining the total current received, and comparing it with the requested current to perform an error check.

97. The method of claim 96, wherein in the event that the difference between the requested current and the received current is larger than a predetermined threshold further: (i) adjusting the requested current; and/or (ii) aborting the charging process; and/or (iii) issuing a warning signal.

98. The mounting system of any of claims 48 to 50, wherein the self-configuration and/or determination of the arrangement of the cells in the array is performed in accordance with the method of any of claims 54 to 73 and/or claims 74 to 97 respectively.

99. The array of claim 98, further comprising an array controller, configured to participate in the method of any of claims 54 to 73 and/or any of claims 131 to 154.

100. A method of assembling an array of battery modules, comprising: (i) electrically connecting a plurality of battery modules together in a combination of parallel and series arrangements, according to the current and voltage output requirements of the array; and (ii) triggering analysis of the arrangement of the battery modules in the array by a battery module in the array.

101. A method of assembling an array of battery modules according to claim 100, wherein the analysis of the arrangement of the battery modules in the array is performed according to the method of claims 74 to 97.

102. A method of assembling an array of battery modules according to claim 100, wherein the battery module which analyses the arrangement of the battery modules in the array comprises a master controller as identified by the method of any of claims 54 to 73.

103. A method of assembling an array of battery modules according to claim 100, wherein the battery module which analyses the arrangement of the battery modules in the array is also arranged to determine and request an amount of current required to charge the battery modules in the array from an external current source, based on the arrangement of the battery modules in the array.

104. A method substantially as described herein, and as illustrated in the accompanying drawings.

105. An apparatus substantially as described herein, and as illustrated in the accompanying drawings.