WO2002035677A1

WO2002035677A1 - A battery monitoring system

Info

Publication number: WO2002035677A1
Application number: PCT/AU2001/001368
Authority: WO
Inventors: Kerry D Nufer
Original assignee: Kerry D Nufer
Priority date: 2000-10-25
Filing date: 2001-10-25
Publication date: 2002-05-02
Also published as: AU1199202A; AUPR102000A0; NZ526091A

Abstract

A battery monitoring system for monitoring cells in a battery bank where the cells are interconnected between output terminals, the system having: a controller having a plurality of current sinks that are operable to supply an alternating current of a predetermined magnitude to the bank such that the predetermined current is caused to flow through the cells; and a plurality of transducers arranged in series with one another and coupled to the controller, wherein each transducer is coupled to electrodes of an associated said cell and each said transducer being adapted to measure cell characteristics and the impedance between an electrode of an associated cell and a link connected to the electrode, at least some of the plurality of transducers being powered by cells of the bank, the transducers functioning to transmit information to and receive information from the controller, the transducers measuring characteristics of the cells when the predetermined current flows through the cells.

Description

A BATTERY MONITORING SYSTEM

Field of the Invention

This invention relates to a battery monitoring system. In particular, the invention relates to a battery monitoring system for monitoring cells in a battery bank having a plurality of connected battery cells.

Description of the Prior Art The cells in a battery bank require routine monitoring for maintenance purposes. Such monitoring has traditionally involved measurement of battery parameters such as cell terminal voltage, cell specific gravity, cell impedance, inter-cell connection impedance and cell temperature.

Simple measurement of cell terminal voltage does not yield results which provide an accurate indication of battery capacity. Specific gravity testing is not possible with modern sealed valve regulated lead acid (VRLA) batteries.

There have been various earlier proposals for measuring battery cell characteristics while the battery is in service. Many of these earlier proposals such as those disclosed in United States Patent specifications

5,705,929, 6,094,030 and 5,666,040 required complex wiring looms to connect each individual cell in a bank of cells to monitoring circuitry.

The installation of such looms was not only complex but gave rise to difficulty in obtaining accurate readings. These wiring looms introduced added unwanted resistance into the testing circuit paths. Long wiring looms were also susceptible to stray pick-up of test currents and interference.

Some earlier proposals such as those disclosed in United States Patent specifications 5,969,625 and 5,281 ,920 provide for cell impedance measurement but disclose devices which do not provide for a large dynamic range in the AC current employed in obtaining an indication of cell impedance. It is an object of the present invention to provide a battery monitoring system which at least minimises some of the disadvantages referred to above.

Summary of the Invention

According to a first aspect of the invention there is provided a battery monitoring system for monitoring cells in a battery bank where the cells are interconnected between output terminals, the system having: a controller having a plurality of current sinks that are operable to supply an alternating current of a predetermined magnitude to the bank such that the predetermined current is caused to flow through the cells; and a plurality of transducers arranged in series with one another and coupled to the controller, wherein each transducer is coupled to electrodes of an associated said cell and each said transducer being adapted to measure cell characteristics and the impedance between an electrode of an associated cell and a link connected to the electrode, at least some of the plurality of transducers being powered by cells of the bank, the transducers functioning to transmit information to and receive information from the controller, the transducers measuring characteristics of the cells when the predetermined current flows through the cells.

The characteristics measured by the transducers may comprise the terminal voltage of the cells, cell impedance and operating temperature of the cells.

It is preferred that the controller be powered from the output terminals of the battery bank. A DC to DC converter may be coupled to the output terminals and the controller, wherein the converter is adapted to supply power to the controller. The converter may reduce the voltage at the terminals to a level of say 12VDC for supply to the controller.

The controller has a plurality of current sinks and by summing the outputs from selected ones of these sinks an AC current of a predetermined magnitude may be provided for application to the cells in the bank. Preferably the first three transducers in a string of series connected transducers derive their power supply partially from the controller whilst the other transducers in the string are powered from cells in the bank.

Advantageously, at least one of the transducers has a microcontroller which is coupled to the controller. The transducer may have an analogue to digital converter coupled to the micro-controller. The transducer may have a DC amplifier coupled to the analogue to digital converter. The DC amplifier may be coupled to the electrodes of an associated cell. The transducer may have a rectifier coupled to the analogue to digital converter. The transducer may have a band-pass filter coupled to the rectifier. The transducer may have an AC amplifier coupled to the band-pass filter. The AC amplifier may be coupled to the electrodes of an associated cell. The transducer may have an analogue multiplexer coupling the AC amplifier to the electrodes of the associated cell, wherein the analogue multiplexer is controlled by the micro-controller. The transducer may include opto-couplers which are coupled to the micro-controller, the opto-couplers enabling the micro-controller to transmit information to and receive information from the controller. The transducer includes a fibre optic emitter and a fibre optic detector which are coupled to the micro-controller, the fibre optic emitter and fibre optic detector enabling the micro-controller to transmit information to and receive information from the controller. The transducer may have a temperature sensor coupled to the micro-controller.

Advantageously, the controller includes a micro-controller. Preferably, the micro-controller is coupled to the current sinks. Preferably, the controller includes a user interface for enabling a user to configure the system, the user interface being coupled to the micro-controller. The user interface may include a display and a keyboard. The controller may have a data communication interface which is coupled to the micro-controller.

Advantageously, the controller and the transducers are coupled together by a fibre optic cable. The system may be configured to monitor the cells in a plurality of battery banks.

The alternating current supplied by the current sinks may be sinusoidal or non-sinusoidal.

In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings.

Brief Description of the Drawings

Fig. 1 is a block diagram of a battery monitoring system according to a first embodiment of the invention;

Fig. 2 is a block diagram of a transducer employed in the system of Fig. 1 ;

Fig. 3 is a block diagram of a controller employed in the system of Fig. 1 ;

Fig. 4 is a block diagram of a battery monitoring system according to a second embodiment of the invention; Fig. 5 is a block diagram of a transducer employed in the system of Fig. 4;

Figs. 6A to 6C are flowcharts illustrating various operations of the transducer of Fig. 5;

Fig. 7 is a block diagram of a controller employed in the system of Fig. 4;

Figs. 8A to 8C form a schematic diagram of the battery monitoring system of Fig. 4;

Figs. 9A to 9C form a schematic diagram of the transducer of Fig. 5; Fig. 10 illustrates the communications data packet structure used by the system of Fig. 4;

Fig. 11 illustrates the communications line code used by the system of Fig. 4;

Fig. 12A is a schematic diagram which illustrates the interconnection of the transducer of Figs. 9A to 9C with a cell of the battery bank in the case where the cells of the battery bank are interconnected by dual links; Fig. 12B is a schematic diagram which illustrates the interconnection of the transducer of Figs. 9A to 9C with a cell of the battery bank in the case where the cells of the battery bank are interconnected by a single link; Figs. 13A to 13D form a schematic diagram of the main processor, display and keyboard circuitry of the battery monitoring system illustrated in Figs. 8A to 8C;

Figs. 14A to 14G form a schematic diagram of the precision current sink circuitry of the battery monitoring system illustrated in Figs. 8A to 8C;

Figs. 15A to 151 form a schematic diagram of the power supply and system interface circuitry of the battery monitoring system illustrated in Figs. 8A to 8C; and

Figs. 16A to 16C form a schematic diagram of the DC to DC converter of the battery monitoring system of Figs. 8A to 8C.

Detailed Description

Referring to Fig. 1 , a first embodiment of a battery monitoring system is designated generally by the numeral 20. The figure shows 12 cells 21 connected in series with one another and to a load associated with output terminals 22, 23.

The system 20 includes a DC to DC converter 24 which is coupled to the output terminals 22, 23. The converter 24 functions to reduce the voltage made available by the battery bank to a level suitable for powering the system 20. For example the converter 24 may reduce the voltage at the battery bank terminals to 12VDC.

The system 20 includes a controller 25 adapted to be powered by the converter 24 although the controller 25 may be powered in any other suitable manner. The controller 25 has an external data connection 26 and is coupled to a first transducer 27 of a plurality of series connected transducers

28 to 38. A bus 41 connects transducer 27 to the controller 25 and the transducers 27 to 38 are coupled in series with each other. In one embodiment the bus 41 is a ribbon cable and the transducers 27 to 38 are connected to each other by short lengths of like ribbon cable. Bus or ribbon cable 41 also provides for the connections which allow for measurement of the impedance of links 52 between adjacent cells. The links 52 may take the s form of single or multiple pieces of solid bus bar or flexible cable. Fig. 2 shows in greater detail the connection between the transducers 27 to 38 and the cells.

With the system 20 a theoretically limitless number of transducers may be daisy-chained together in series to monitor each of the o cells in a battery bank. The controller 25 supervises battery condition data acquisition via the transducers 27 to 38, acts as a temporary store of data, adjudicates alarm conditions and provides a single point of interface to the outside world via communications interfaces such as by data connection 26. If desired a number of controllers may be networked through one controller s configured as a group controller.

In Fig. 1 twelve cells are connected to each other to form a battery bank. However the number of cells is illustrated by way of example only. The individual cells in the bank may be connected to each other in any suitable way. In this embodiment the cells may be connected with heavy o flexible cable or solid aluminium or copper. At the very ends of the bank, cables 39, 40 connect the bank to terminals 22 and 23.

The transducers 27 to 38 are daisy-chained to each other and are connected to the cells. The last transducer 38 is connected to the last cell by a cable 42 such as a transducer string termination cable. Cable 42 5 closes the communications current loop and terminates the N-1 transducer sensing line.

The transducers 27 to 38 are connected to each cell of the battery bank via a probe lead set. This set includes two conductors - one for power and the other for signals - so as to not cause artificial voltage drops 0 due to IR losses in the power lead. This facilitates powering of the transducers 27 to 38 as well as the simultaneous sensing of terminal voltage of each cell and impedance of the cells and of the link between adjacent cells. Fig. 2 shows connection details and structure of a typical transducer identified as transducer "N" in a string of like constructed transducers. Transducer "N" is shown connected to two cells identified as cell "N" and cell "N-1 ". A third cell "N+1 " is also shown. The three cells are interconnected by links 52. Transducer "N" has a DC amplifier 53 coupled across the terminals of cell "N". Amplifier 53 provides an output indicative of the positive voltage across the terminals of the cell "N". AC amplifier 54 is a low noise amplifier. As explained below an AC current of a predetermined magnitude is caused to flow through the series connected cells of the battery bank. The output from amplifier 54 being indicative of the AC voltage drop across the terminals of the cell "N". This information coupled with the known value of the AC current flowing through the cell allows the cell impedance to be determined.

AC amplifier 55 is a low noise amplifier and this amplifier provides an output indicative of the AC voltage drop across one of the links 52. This information coupled with the known value of the AC current flowing through the cells allows the impedance of the link between cells "N" and "N-1" to be determined.

Amplifiers 54 and 55 are coupled to a switch 56 which alternately connects the output from a selected one of these two amplifiers to band pass filter 57. Filter 57 has a centre frequency matching the frequency of the AC current which is caused to flow through the cells of the battery bank.

Switch 56 is controlled by micro-controller 58. A precision rectifier 59 receives the output from the filter 57 and ensures that the output is converted into a positive voltage signal proportional to the applied AC signal from the output of the band-pass filter.

The transducer includes a temperature sensor 60 which provides an output indicative of the temperature of the cell "N". Sensor 60 may be placed against a housing or casing of the cell. Analogue multiplexer 61 receives the outputs from sensor 60, from amplifier 53 and from the rectifier 59 and selectively supplies them to an analogue to digital (A/D) converter 62. The multiplexer 61 is controlled by the micro-controller 58 and has voltage references 63 coupled to it.

The transducer includes a power supply 64. In a preferred form, each transducer has two 5 volt regulated power supplies derived from a primary supply via the cells in the battery bank. Each transducer has three positive battery feeds from the cell ahead of the cell to which the transducer is coupled and translates them one position at a time between connectors extending between the transducers. For example, if the power from cells N+1 , N+2 and N+3 are presented on connections from cells ahead of transducer N, power from feed N+3 will be used to power transducer N.

When power is presented on the connector to the following transducers, incoming N+1 and N+2 will be translated to N+2 and N+3 whilst connection 1 will be connected to the positive power input to transducer N.

Using this method of precession, each transducer is able to receive power at a suitable voltage from the cells in the battery bank.

Power for the first three transducers in a string of series connected transducers is partially derived from the controller 25 which includes separate power supplies.

All aspects of transducer operation are controlled by the micro- controller 58 included in each transducer. These aspects include:

(a) power management;

(b) communications;

(c) multiplexer channel selection;

(d) A/D converter operation; and (e) battery link selection (i.e. operation of switch 56).

The communication to and from the transducer "N" occurs in a half duplex manner on data connection 71. The micro-controller 58 controls a transmitting opto-coupler 72 which allows data to be coupled to connection 71 through the operation of switch 73. Switch 73 is subsequently modulated on and off by data being transmitted from the controller 25 and shorts out the

Light Emitting Diode (LED) 74 of the receiving opto-coupler 75. Since the light emitting diode circuit has a fairly constant voltage drop while there is a constant current flowing through it, the shorting action results in a voltage drop which is transmitted and level shifted through the chain of other diodes to the controller constant current source. At this point 71 the resulting voltage variation is sensed and used to recover the transmit data from the transducer. The return path for this data connection 71 is via the battery itself. Currents due to data flow and application of the AC test current are not undertaken simultaneously, preventing injection of interference into the impedance measuring process.

The processor 58 is powered up from a sleep state by a current flowing through receiving opto-coupler 75 which causes an interrupt. The processor 58 reads data, determines whether the address corresponds to the address for the particular transducer and responds if required. When the processor 58 responds it must have a current flow through opto-coupler 72 in order to be able to communicate. The transmitting opto-coupler 72 transmits data by applying a temporary short circuit across LED 74 of the opto-coupler 75. This has the effect of causing a single diode voltage drop along the connection 71. At the controller 25, this drop is detected and decoded. Data communication is via a modified self-clocking Manchester coding scheme which is highly resilient to timing variations in transmission clocking variations. Data rate is nominally 2400 bits/sec.

Fig. 3 shows a detailed block diagram of a controller 25. The controller 25 has a plurality of selectable precision current sinks 80 for providing AC current signals. An AC current typically having a frequency of 1 KHZ is derived from these sinks 80 and caused to flow through the cells in the battery bank. The sinks 80 are typically 16 in number and supply currents of 1 mA, 2mA, 2mA, 5mA, 10mA, 20mA, 20mA, 50mA, 100mA, 200mA, 1 Amp, 2 Amp and 2 Amp peak to peak. Selected ones of the sinks 80 may be summed to provide an AC current of a predetermined magnitude. In this way a particularly large dynamic range of AC current is available for allowing a determination of cell impedance and link impedance to be made for a variety of different battery bank configurations.

The voltage output available from the converter 24 is made available to the current sinks 80 and a power supply/regulator 81. Regulator 81 provides a local power supply for the controller 25 although power may also be derived from an alternative 240VAC supply.

The controller 25 has a micro-controller 82. A keyboard 83 and a display 84 are associated with the micro-controller 82. The first three transducers in a string are powered by the controller 25 as shown and a transducer transmit data stream to connection 71. The connection 71 is coupled to an amplifier 85 which in turn is connected to a Schmitt trigger 86 to allow received data from the transducers to be supplied to the micro-controller 82. The micro-controller 82 has an alarm 87 and communications interfaces 88 associated with it.

The minimum system configuration would include a controller 25 and a single transducer. The controller 25 functions as a master device of the system. It supervises and manages all communications with the transducers 27 to 38; accepts commands from the keyboard 83 and displays results on the display 84.

The precision current sinks 80 allow the system 20 to obtain cell and link impedance measurements. Where a battery bank is tested in a live system the majority of the current flows through the bank due to the relatively low impedance it would represent. For precise measurements, the leakage current through rectifiers, the load and other components can also be measured.

The current from the current sinks 80 is modulated by 1V peak to peak 1 KHZ sine wave. During an impedance test, a transducer requests the controller 25 to generate a specific current, if the current is too large or small for the transducer, it will request that the controller 25 to either decrease or increase the current in steps as small as 1 mA in order to detect the resultant voltage within range of the transducer detector. The value of current is recorded in the transducer memory and used with the measured AC 1 kHz voltage to calculate the impedance of the cell or link in accordance with Ohms

Law.

The transducers 27 to 38 may be simply connected to each cell as described. In an alternative arrangement the transducers 27 to 38 may be fully incorporated into the casing and structure of the cell itself and this may include the conductors which extend from the transducer to the electrodes of the cell. With the transducers 27 to 38 incorporated into the structure of the cells the cells in a bank simply need to be interconnected with a daisy- chained data cable as shown in Fig. 1.

When the transducer is incorporated into the cell, when the cell is constructed, the connections shown in Figs. 1 and 2 are present inside the cell and the transducer is mounted within the casing of the cell in a suitable location. The transducer may carry a serial number which uniquely identifies the cell and may recapture information indicative of the operation of the cell which may be accessed externally. This allows a determination of cell operation history and performance to be obtained.

The system 20 may be used with any type of battery technology. A second embodiment of a battery monitoring system 90 is illustrated in Fig. 4. For convenience, features of the battery monitoring system 90 that are similar or correspond to features of the battery monitoring system 20 have been referenced using the same reference numbers.

The system 90 differs from the previously described system 20 in a number of respects. For example, the bus 41 of the system 90 is in the form of a fibre optic cable and the transducers 27 to 38 are connected to each other by short lengths of like fibre optic cable. A further difference is that each transducer 27 to 38 of the system 90 derives its power from an associated cell. Further differences between the systems 20 and 90 will become apparent from the following discussion.

Fig. 5 shows connection details and structure of a typical transducer identified as transducer "N" in a string of like constructed transducers. Transducer "N" is shown connected to a single cell identified as cell "N". Cell "N" is located between two cells identified as cell "N-1 " and cell "N+1 ".

The three cells are interconnected by links 52. Transducer "N" has a DC instrumentation amplifier 53 coupled across the terminals of cell "N". Amplifier 53 provides an output indicative of the positive voltage across the terminals of the cell "N". Transducer "N" also has an AC instrumentation amplifier 54. Each input of amplifier 54 is coupled to the output of an associated analogue multiplexer 65, 66. Of the three inputs of multiplexer 65, one is AC coupled to the link 52 which is coupled to the positive terminal of cell "N", one is AC coupled to the positive terminal of cell "N" and one is AC coupled to the negative terminal of cell "N". Of the three inputs of multiplexer 66, one is AC coupled to the positive terminal of cell "N", one is AC coupled to the negative terminal of cell "N" and one is AC coupled to the link 52 which is coupled to the negative terminal of cell "N". The link 52 which is coupled to the positive terminal of cell "N" is termed the positive link while the link 52 which is coupled to the negative terminal of cell "N" is termed the negative link. A microprocessor 58 controls the multiplexers 65, 66 to couple the inputs of the amplifier 54 to: (a) the positive link and the positive terminal of the cell "N"; or

(b) the positive and negative terminals of the cell "N"; or

(c) the negative link and the negative terminal of the cell "N". When an AC current having a predetermined magnitude controlled by a precision current sink is caused to flow through the series connected cells of the battery bank, the output from amplifier 54 provides an indication of the AC voltage drop between the input terminals of the amplifier 54. Depending on how the inputs of the amplifier 54 are coupled to the cell "N" or positive or negative links, the voltage drop information coupled with the known value of the AC current flowing through the cell "N" allows the impedance of the positive link, negative link or the cell "N" to be determined. The output of amplifier 54 is coupled to the input of a switched gain amplifier 67. The output of the amplifier 67 is coupled to a band-pass filter 57. Filter 57 has a centre frequency matching the frequency of the AC current which is caused to flow through the cells of the battery. A precision rectifier 59 receives the output from the filter 57 and ensures that the output is converted into a positive voltage signal proportional to the applied AC signal from the output of the band-pass filter. A switch 61 receives the outputs from amplifier 53 and from the rectifier 59 and selectively supplies them to a low-pass filter 68 which removes noise from the output from amplifier 53 or rectifier 59. An analogue to digital (A/D) converter 62 receives the output from the filter 68. The switch 61 is controlled by the micro-controller 58.

The transducer "N" includes a power supply 64. In a preferred form, each transducer has a 5 volt regulated power supply derived from a primary supply via the cell "N". In particular, the 5 volt regulated power supply is coupled to the positive and negative terminals of the cell "N". Aspects of transducer operation which are controlled by the micro-controller 58 included in each transducer include:

(a) power management;

(b) communications;

(c) multiplexer channel selection; (d) remote supervision of the precision current sink;

(e) operation of switch 61 ; and

(f) A/D converter operation;

The transducer "N" includes a fibre optic emitter 69 and a fibre optic detector 70 which couple the micro-controller 58 to the fibre optic cable 41. The micro-controller 58 reads data arriving at the detector 70 and transmits data using the emitter 69. Data arriving at the detector 70 can include address data indicating the particular transducer for which the data is intended.

Referring to Fig. 6A, when a transducer powers-up, the micro- controller 58 associated with the transducer performs a number of hardware check routines. Upon completion of the hardware check routines the microcontroller 58 controls a light emitting diode (LED) which is associated with the transducer to provide a visual indication of whether or not the hardware check routines detected any hardware faults. If the hardware check routines detected any hardware faults the micro-controller 58 controls the LED to flash continuously. If the hardware check routines did not detect any hardware faults the micro-controller controls the LED to emit a single flash upon completion of the hardware check routines. After setting up communication interrupts the micro-controller 58 enters a sleep state in which the power consumption of the micro-controller 58 is reduced.

Referring to Fig. 6B, the micro-controller 58 is awoken from the sleep state by a communications interrupt caused by the fibre optic detector 70 associated with the micro-controller detecting the transmission of a data packet on the fibre optic cable 41 . The micro-controller 58 reads the data packet and determines whether the data packet is addressed to the microcontroller 58. If it is determined that the data packet is not addressed to the micro-controller 58, the micro-controller 58 re-enters the sleep state. If it is determined that the data packet is addressed to the micro-controller 58, the micro-controller 58 powers itself up fully and commences to interpret the command data which is included in the data packet.

Referring to Fig. 6C, when interpreting the command data the micro-controller 58 firstly determines whether the command data is instructing the transducer to conduct a housekeeping function. If it is determined that the command data is instructing the transducer to conduct a housekeeping function, the micro-controller 58 performs the housekeeping function, assembles a reply data packet confirming that the housekeeping function has been performed and transmits the reply data packet onto the fibre optic cable

41 via the fibre optic emitter 69. If it is determined that the command data is not instructing the transducer to perform a housekeeping function, the microcontroller 58 determines whether the command data is instructing the transducer to measure the voltage of the cell associated with the transducer. If it is determined that the command data is instructing the transducer to measure the cell voltage, the micro-controller 58 configures the transducer to measure the cell voltage by controlling the switch 61 to couple the amplifier 53 to the low-pass filter 68. The micro-controller 58 then controls the A/D converter 62 to convert the analogue output signal from the low-pass filter 68 into a digital format which is proportional to the cell voltage.

The output from the A D converter 62 is then communicated to the microcontroller 58 which assembles the cell voltage data into a reply data packet and transmits the reply data packet onto the fibre optic cable 41 via the fibre optic emitter 69. If it is determined that the command data is not instructing the transducer to measure the cell voltage, the micro-controller 58 determines whether the command data is instructing the transducer to measure an impedance of the associated cell.

If it is determined that the command data is instructing the transducer to measure an impedance associated with the cell, the microcontroller 58 configures the transducer to measure the particular impedance associated with the cell. The micro-controller 58 controls the switch 61 to couple the rectifier 59 to the low-pass filter 68. If the impedance to be measured is the impedance of the positive link, the micro-controller 58 controls the multiplexers 65, 66 to couple the inputs of the amplifier 54 to the positive link and the positive terminal of the cell. If the impedance to be measure is the impedance of the cell, the micro-controller 58 controls the multiplexers 65, 66 to couple the inputs of the amplifier 54 to the positive and negative terminals of the cell. If the impedance to be measured is the impedance of the negative link, the micro-controller 58 controls the multiplexers 65, 66 to couple the inputs of the amplifier to the negative link and the negative terminal of the cell. The micro-controller 58 determines the previous test current used and instructs the precision current sink, via the fibre optic emitter 69, to cause that same current to flow through the cell. The micro-controller 58 then controls the A/D converter 62 to convert the analogue output signal from the low-pass filter 68 into a digital format which is proportional to the measured voltage. The output from the A/D converter 62 is then communicated to the micro-controller 58. After taking gain and conversion losses into account, the micro-controller 58 calculates the impedance using Ohm's law. If the calculated impedance falls outside a predetermined range the micro-controller 58 instructs the precision current sink to adjust the current flowing through the cell by a particular amount. The transducer then measures the impedance again while the adjusted current flows through the cell. Once the measured impedance falls within the predetermined range the micro-controller 58 assembles the impedance data into a reply data packet and transmits the reply data packet onto the fibre optic cable 41 via the fibre optic emitter 69. If it is determined that the command data is not instructing the transducer to measure an impedance associated with the cell, the micro-controller 58 assembles an error code and assembles this error code into a reply data packet. The reply data packet is then transmitted onto the fibre optic cable 41 via the fibre optic emitter 69.

Fig. 7 shows a detailed block diagram of the controller 25 associated with the system 90. The controller 25 has been modified to dispense with the transducer power supplies, transducer communications current loop, amplifier 85 and Schmitt trigger 86 of the system 20. Further, instead of 16 current sinks the controller 25 has 11 current sinks supplying currents of 1 mA, 2mA, 2mA, 5mA, 20mA, 20mA, 50mA, 200mA, 200mA, 500mA and 2 Amp peak to peak.

Similarly to the system 20, the voltage output available from the converter 24 is made available to the current sinks 80 and a power supply/regulator 81. Regulator 81 provides a local power supply for the controller 25 although power may also be derived from an alternative 240VAC supply.

In place of the transducer communications current loop, amplifier 85 and the Schmitt trigger 86, the controller 25 has a fibre optic detector and a fibre optic emitter which allow the controller 25 to couple with the fibre optic cable 41.

Figs. 8A to 8C provide further detail of the system 90. The controller 25 is shown as having two modules. A first one of the modules relates to the main processor, display and keyboard circuitry while a second one of the modules relates to the power supply, interface and current sink circuitry. Connectors J08' and J09' of the first module couple with connectors J08 and J09 of the second module.

Connector J03 and/or connector J04 of the second module provide the external data connection 26 of the controller 25. Connector J03 provides for RS232 communications while connector J04 provides for RS485 or ETHERNET communications. Connectors J21 and J22 are intended to function as major and minor alarm outputs to be used for activating clean relay contacts to external devices.

Connector J07 enables auxiliary control devices to interface with the controller 25.

Connectors J01 and J05 of the controller 25 are coupled to the DC-DC converter 24. In particular, connectors J01 and J05 are coupled to connectors J01 ' and J02 of the converter 24.

The controller 25 may be powered by the converter 24 or from an AC plug pack coupled to the controller 25 via connector J02. If a plug pack is used to supply power to the controller 25, the supply from the plug pack takes precedence over the supply from the converter 24 such that the supply from the converter 24 is effectively disconnected from the controller 25. The controller 25 includes two duplex Plastic Optical Fibre

(POF) ports. The transmitter interface of the first port is designated as POF TX Batt 1 , while the transmitter interface of the second port is designated as POF TX Batt 2. The receiver interface of the first port is designated as POF RX Batt 1 , while the receiver interface of the second port is designated as POF RX Batt 2. Provision of the second POF port enables a second fibre optic loop to be coupled to the controller 25.

Transducers 27 to 38 are each coupled to an associated one of the cells 21 as previously described in connection with Fig. 5. Each transducer 27 to 38 also includes an auxiliary peripheral interface designated as Adj V Measure. The auxiliary peripheral interface enables transducers 27 to 38 to measure an additional external voltage. The auxiliary peripheral interface of each transducer 27 to 37 is coupled to a cell 21 adjacent to the cell 21 to which the other inputs of each said transducer 27 to 37 are coupled.

Each transducer 27 to 38 includes a POF port having a transmitter interface designated as POF TX and a receiver interface designated as POF RX. The receiver interface POF RX of transducer 27 is coupled to the transmitter interface POF TX Batt 1 of the controller 25. The transmitter interface POF TX of transducer 27 is coupled to the receiver interface POF RX of transducer 28 and the transmitter interface POF TX of transducer 28 is coupled to the receiver interface POF RX of transducer 29. The remaining transducers 30 to 38 are coupled together in a similar fashion. 5 The transmitter interface POF TX of transducer 38 is coupled to the receiver interface POF RX Batt 1.

Cells 21 are coupled together in series via links 52. The cable 39 couples the positive terminal of a first one of the cells 21 to the terminal 22. The cable 40 couples the negative terminal of a last one of the cells 21 to o the terminal 23. Terminals 22 and 23 are coupled to a load distribution and battery rectifier system.

The converter 24 is adapted to perform a number of functions including powering the controller 25 and coupling the battery bank to the precision current sink incorporated into the controller 25. s With regard to powering the controller 25, connector J21 of the converter 24 is coupled to the cables 39, 40 so that the battery bank supplies power to the converter 24. According to the preferred form of the system 90, the converter 24 is adapted to convert a nominal voltage of 48VDC supplied by the battery bank to 12VDC, which is suitable for powering the controller 25. 0 Further, the converter 24 is adapted to isolate the voltage supplied by the battery bank from the controller supply voltage. The converter 24 also includes redundant power supply sources for the controller 25.

Connector J11 of the converter 24 enables a second battery bank to be coupled to the converter 24. A selector means, such as a switch, 5 enables the converter 24 to be coupled to either one of the two battery banks.

Additional selector means can be provided if more than two battery banks are to be coupled to the converter 24.

The controller 25 controls the overall operation of the system 90. In particular, the controller 25 supervises the measurement of cell 0 characteristics via the transducers 27 to 38. The controller 25 transmits a data packet incorporating address and command data to the transducers 27 to 38 via the first POF port. The transducer to which the data packet is addressed responds by performing the command to which the command data refers. If the command instructs the addressed transducer to measure a particular impedance associated with the cell to which the transducer is coupled, the transducer responds by transmitting a data packet to the controller 25. The data packet transmitted to the controller 25 instructs the controller 25 to control the precision current sink to sink a specified amount of AC current through the battery bank. When the specified amount of AC current is being sunk by the precision current sink, the transducer measures the AC voltage formed across the impedance to be measured as a result of the AC current. After the gain and conversion losses of the transducer are taken into account, the transducer calculates the impedance using Ohm's law. The calculated impedance data is then transmitted to the controller 25 by the transducer.

Data packets are transmitted along the POF using a modified Manchester self-clocking coding scheme. Each transducer 27 to 38 is transparent to the flow of data, which eventually appears back at the controller 25. This enables the integrity of the communications loop to be monitored by allowing for the detection of faults in the communications loop or data errors. If the controller 25 transmits a data packet addressed to a specific transducer and the transducer receives the data packet, the transducer responds to the data packet by performing the action specified by the command data contained in the data packet. The transducer also transmits a reply data packet to the controller 25. If the controller 25 does not receive a reply data packet from the addressed transducer within a certain period of time after having transmitted the data packet to the transducer, the controller 25 registers that there is a fault in the communications with the addressed transducer.

In some cases, the controller 25 may instruct more than one transducer to simultaneously measure the characteristic of a like number of cells. In that case, the individual transducers do not automatically transmit the measured data back to the controller 25. Instead, the controller 25 separately polls the transducers to transmit the measured data.

A detailed schematic diagram of one of the transducers 27 to 38 is illustrated in Figs. 9A to 9C. The illustrated transducer includes an RJ45 socket which is designated as J01. Socket J01 receives an associated plug which is coupled to the terminals and links of an associated cell. Socket J01 includes eight pins. The pin allocations of socket J01 are provided in Table 1 below.

Table 1. Socket J01 Pin Allocations

As mentioned previously, power for the transducer is derived from the cell to which the transducer is coupled. In particular, the cell is coupled to a 5VDC regulated power supply 64 in the form of a switched-mode power supply adapted to supply power to the various components of the transducer. Power supply 64 includes a switched-mode power supply integrated circuit U03, inductor L01 , capacitors C10, C11 and C30, resistors R30 and R31 and a diode D20.

The power consumption of the transducer varies in accordance with the particular task being performed by the transducer. The power consumption of the transducer is typically at a maximum when the transducer is transmitting data on the fibre optic cable 41. The power consumption of the transducer is typically at a minimum when the micro-controller 58 enters the previously mentioned sleep-state.

The transducer also includes a Programmable System on Chip (PsoC) integrated circuit U01 which provides the amplifier 53, band-pass filter 57, micro-controller 58, A/D converter 62, amplifier 67 and low-pass filter 68, which have been mentioned previously.

The auxiliary peripheral interface of the transducer is designated generally by the numeral 101. In addition to enabling the transducer to measure an additional external voltage, interface 101 enables the transducer to interface with miscellaneous external measurement devices. The interface 101 has a four-pin connector J03. The pin allocations of connector J03 are provided in Table 2 below.

Table 2. Connector J03 Pin Allocations

The auxiliary peripheral interface 101 also includes resistors

R32 to R37 and diodes D18 and D19. Pin 2 of connector J03 is coupled to an A/D converter 102 contained in the integrated circuit U01. The output of the A/D converter 102 is coupled to the micro-controller 58. Pin 3 of connector J03 is coupled to switch SW1.

A DC input sealer and protection circuit 100 is coupled to pins 3 and 6 of the socket J01 and switches SW1 and SW2. The input sealer portion of the circuit 100 includes resistors R07 to R10. In the preferred embodiment of the system 90 the input sealer portion of the circuit 100 is configured to provide a ratio of 6:1 between the input and output of the circuit 100. The input protection portion of the circuit 100 includes diodes D13 to D16. The input protection portion of the circuit 100 provides protection against excessive input voltage excursions both above and below the upper and lower supply rail voltages provided by the power supply 64.

When the transducer measures a DC voltage across pins 3 and 6 of socket J01 , switches SW1 and SW2 are operated by the micro-controller 58 to be in their default positions so that the output of circuit 100 is coupled to instrument amplifier 53. In the case where pins 3 and 6 of socket J01 are coupled to the terminals of a cell, the output of circuit 100 will be a differential DC voltage representative of the potential of the cell. The output of amplifier 53, which is ground referenced, is coupled to the low-pass filter 68. Switch SW3 is operated by the micro-controller 58 to couple the output of the low- pass filter 68 to the A/D converter 62 which is coupled to the micro-controller 58. Micro-controller 58 processes the digital output of the A/D converter 62 to obtain the value of the voltage being measured. The micro-controller 58 automatically adjusts the gain of amplifier 53 to ensure that the output of the amplifier 53 is within the input range of the A/D converter 62 to account for cell and monoblock voltages in excess of 16 volts. In processing the digital output of the A/D converter 62, the micro-controller 58 takes into account the gain or attenuation of the amplifier 53.

An input bias circuit 103 is AC coupled to pins 1 , 2, 3, 6, 7 and 8 of the socket J01 via capacitors C01 to C06. The input bias circuit 103 includes resistors R01 to R06 which are coupled to the capacitors C01 to C06 and an analogue ground potential AGnd which is derived from the analogue circuitry of the integrated circuit U01. In the preferred embodiment of the system 90 the analogue ground potential AGnd is approximately 2.5V. An input protection circuit 104 is coupled to the input bias circuit

103. The input protection circuit 104 includes diodes D01 to D12 and a diode D17. The input protection circuit 104 provides a clamping action to prevent the applied input signal from momentarily exceeding the upper power supply rail voltage provided by the power supply 64 or falling more than 0.5V below the lower supply rail voltage

A dual 4:1 CMOS multiplexer integrated circuit U04 is coupled to the input protection circuit 104. The integrated circuit U04 provides multiplexers 65, 66. The operation of the multiplexers 65, 66 is controlled by the micro-controller 58 which is coupled to the circuit U04 via pins A and B. The micro-controller 58 controls the circuit U04 to couple the signal from pins

1 and 2, or pins 3 and 6, or pins 7 and 8 of the socket J01 to the amplifier 54. Amplifier 54 includes amplifiers U02A, U02B and resistors R20 to R23. The output signal produced by amplifier 54 is referenced to ground potential and is applied to amplifier 67.

The output of amplifier 54 is coupled to switched gain amplifier 67 and the output of amplifier 54 is coupled to band-pass filter 57. When the transducer is configured to measure the impedance of a load while an AC sine wave current flows through the load, filter 57 is tuned to the frequency of the current in order to remove out-of-band noise. The output of band-pass filter 57 is coupled to rectifier 59. Rectifier 59 includes amplifiers U02C and U02B, resistors R40 to R47 and diodes D06, D07. The output of rectifier 59, which is a full-wave rectified sinusoid, is applied to the non-inverting input of amplifier 53 via switch SW1 which is controlled by the micro-controller 58. Simultaneously, the micro-controller 58 causes the switch SW2 to couple the analogue ground potential AGnd so that the amplifier 53 operates as a single input stage. The output of amplifier 53 is applied to the low-pass filter 68 so as to remove the AC ripple components of the full-wave rectified waveform. The resulting DC voltage presented to the A/D converter 62 is a function of the AC voltage developed across the cell or the positive or negative links. The digital output of the A/D converter 62 is presented to the micro-controller 58 which calculates the impedance by dividing the measured voltage by the AC current flowing through the battery bank and multiplying by an appropriate adjustment factor to account for the detection process.

The LED previously referred to in connection with the operation of the transducer is designated as D30. LED D30 is coupled to an output of the micro-controller 58 and a resistor R50.

The transducer also includes an internal programming interface 105. Programming interface 105 includes a four-pin connector J02 which is coupled to the integrated circuit U01. A suitable programming device can be coupled to the connector J02 to program the integrated circuit U01. The fibre optic emitter 69 and the fibre optic detector 70 are coupled to the micro-controller 58. When the detector 70 is illuminated, the presence of incoming data is registered by the micro-controller 58, which awakens from the sleep-state to process the incoming data. The microcontroller 58 immediately couples the incoming data on pin 11 of the integrated circuit U01 to pin 12 of U01 via internal connections and the internal bus structure of the micro-controller 58. The emitter 69 coupled to pin 12 transmits the data to an adjacent device, which will either be a transducer or the controller 25. The data must be fully circulated back to the controller 25 in real time in order for the data transmission to be declared valid by the controller 25. As well as retransmitting the received data, the micro-controller 58 reads the data and compares the address data contained in the received data with the address of the transducer. If the address data indicates that the incoming data is a general broadcast to all of the transducers or is intended for the receiving transducer, the controller 25 decodes the data. After performing the action specified by the received data, the transducer transmits a response to the controller 25. In the preferred embodiment, the system 90 uses a packeted data structure for communications between the controller 25 and the transducers 27 to 38. The packeted data structure, which is illustrated in Fig. 10, includes a plurality of 8 bit bytes which provide address, command and payload information. The data structure also includes start and end flags as well as check-sum information for increased transmission integrity.

Addressing provides for general broadcasting as well as group and individual addressing regimes. The command codes can be either single or multiple bytes, and are designed to enable future expansion of the system 90.

A modified Manchester line coding system, which includes bit- timing information and provides for robust performance in noisy environments, carries the data packets. Referring to Fig. 11 , the period of an individual bit is divided into three sub-periods. The first 1/3^rd of the period is always low. The second 1/3^rd is high for transmission of a 'zero' and low for transmission of a '1 '. The last 1/3^rd is always high. Bit timing is extracted from the high to low transition during each bit period. The value of the bit is determined by sampling at the intervening periods during the bit period.

Although the transducer generally acts as a slave to the controller 25, which generally acts as a master, the transducer is able to act as a sub-master to the controller 25. In particular, the transducer is able to act as a sub-master to the precision current sink incorporated into the controller 25. This sub-master operation occurs when the transducer is requested by the controller 25 to undertake an impedance measurement. When this occurs, the transducer determines what the last test current level and frequency were and transmits these to the controller 25. The controller 25 controls the precision current sink to sink a current having the same current level and frequency through the battery bank. The controller 25 also transmits a confirmation message to the transducer, which will then attempt to perform the impedance measurement. If the test current is too high or low, the transducer sends a request to the controller 25 for the current level to be appropriately adjusted. The controller 25 then adjusts the current level and sends a confirmation message to the transducer, which again attempts to perform the impedance measurement.

Referring to Figs. 12A and 12B, a transducer is coupled to an associated cell 21 by means of a plurality of conductors 106 and an RJ45 plug J03. The conductors 106 connect to the cell 21 and the plug J03. Socket J01 of the transducer receives the plug J03. A plurality of cells 21 are interconnected by links 52. Links 52 may, for example, be formed from flexible cable or solid aluminium or copper links cut from bus bar. The links 52 are rated to carry high currents due to the fact that most types of industrial battery installations operate with high currents. As illustrated in Fig. 12A, larger capacity cells are often fitted with dual lugs for both the positive and negative terminals in which case the links 52 extend from each terminal as shown. The transducers are adapted for connection to dual lug cells and single lug cells (see Fig. 12B).

Power for the transducer is derived from the cell 21 monitored by the transducer. Power for the transducer is obtained from the cell 21 using dedicated conductors. The current requirements of the transducer vary according to the type of activity being undertaken by the transducer. In the preferred embodiment, the transducer draws a maximum current of approximately 20mA when transmitting data via the fibre optic emitter 69. When the micro-controller 58 is in the sleep-state, the current drawn by the transducer is reduced to less than a mA.

The large amount of gain provided by various components of the transducer (e.g. amplifiers 53 and 54) together with the presence of AC magnetic flux components associated with the current flowing through the battery bank mean that care needs to taken when coupling the transducers to the cells 21 to avoid unwanted coupling of the AC magnetic flux components with the transducer. This is accomplished by twisting each pair of the conductors 106 to the point of connection with the cell 21 or link 52. Using this methodology the impedance of the junction between the link conductor and the cell terminal can be measured.

Referring to Figs. 13A to 13D, the first module of the controller 25 includes a main processor, display circuitry and keyboard circuitry. The overall operation of the system 90 is controlled by the main processor which is in the form of micro-controller 82.

A 20MHz cyrstal XTAL01 is coupled to the micro-controller 82. Crystal XTAL01 is coupled to ground via capacitors C50 and C51.

A reset switch network 107 is coupled to the micro-controller 82. The reset switch network includes a reset switch SW4, a capacitor C52 and a resistor R54.

A resistor network 108 including resistors R55 and R56 is coupled to the micro-controller 82.

Connector J09' is also coupled to the micro-controller 82. Display 84 is coupled to the micro-controller 82. In the preferred form of the system 90, the display 84 is in the form of a dual row 16 character LCD.

Keyboard 83 is coupled to the micro-controller 82. In the preferred form of the system 90, the keyboard 83 includes switches SW0 to SW3 and resistors R50 to R53.

A fibre optic detector interface circuit 109 is coupled to the micro-controller 82 and connector J08'. Circuit 109 includes transistors Q01 , Q11 , Q21 , Q31 and resistors R01 , R02, R03, R11 , R12, R13, R21 , R22, R23, R31 , R32, R33.

A beeper interface circuit 110 is coupled to the connector J08'. The beeper interface circuit 110 includes transistor Q45 and resistors R45 to R47.

A fibre optic emitter interface circuit 111 is coupled to the microcontroller 82 and connectors J08', J09'. Circuit 111 includes transistors Q05, Q15, Q25, Q35 and resistors R05, R06, R07, R15, R16, R17, R25, R26, R27, R35, R36, R37. Resistors R38 and R39 are coupled to the micro-controller 82 and connector J09'. The pins of the micro-controller 82 which are connected to resistors R38 and R39 are normally high impedance and cause resistors R38 and R39 to source current to the alarm relay driver transistors.

A program running on the micro-controller 82 enables user interaction with the system 90 via the keyboard 83 and display 84. The program also supervises communications between the various modules of the controller 25 and communications with the transducers. The program also controls a beeper (not shown) which is coupled to the micro-controller 82 via the beeper interface circuit 110. Further, the program controls alarm relays (not shown) which are coupled to the micro-controller 82.

On power-up, the micro-controller 82 performs a hardware check and controls the display 84 to prompt the user to input information via the keyboard 83. By pressing various ones of the switches SW0 to SW3 which form part of the keyboard 83, the user is able to cause the system 90 to enter one of the following modes:

(a) A general set-up mode which enables the user to configure the controller 25.

(b) A transducer assignment mode which enables the user to configure the transducers and assign them to their respective cells. (c) An operations set-up mode which enables the user to define the parameters associated with the battery monitoring process, (d) A monitor mode which enables the micro-controller 82 to be placed into one of several operating states, including: (i) A manual monitoring state in which specified parameters of particular cells are monitored, (ii) An automatic monitoring state in which the micro-controller 82 places itself into the sleep-state and periodically awakens to obtain the specified parameters of the monitored cells, (iii) A remote monitoring state in which the micro-controller 82 places itself into the sleep-state and awaits an instruction from an external source, which is coupled to the micro-controller via the external data connection 26, to obtain the specified parameters of the monitored cells.

Data acquired by the micro-controller 82 during the monitoring process is stored by the micro-controller 82 until the data is downloaded or otherwise discarded. Referring to Figs. 14A to 14G, the second module of the controller 25 also includes the precision current sinks 80, and a precision waveform generator 112

There are eleven precision current sinks. The current sinks are configured as 1 mA, 2mA, 2mA, 5mA, 20mA, 20mA, 50mA, 200mA, 200mA, 500mA and 2Amp peak to peak current sinks. The current sinks 80 are able to sink between 1 mA through to 3Amps peak to peak. The ability of the current sinks 80 to sink such a range of current amplitudes facilitates a wide dynamic range of impedance measurements using a narrow amplitude detection range as well as flexible off sets to account for current lost through the load and statistical measurement of very low impedance values. Further, rapid go, no-go impedance thresholds are able to be tested during discharge testing of the battery bank.

The 1 mA current sink includes resistors RA01 , amplifiers U02A and U02B, transistor Q01 , capacitors C01 to C04 and resistors R003 and R004.

The first 2mA current sink includes resistors RA02, amplifiers U02C and U02D, transistor Q02, capacitors C05 to C08 and resistors R005 to R008.

The second 2mA current sink includes resistors RA03, amplifiers U03A and U03B, transistor Q03, capacitors C09 to C12 and resistors R009 to R012. The 5mA current sink includes resistors RA04, amplifiers U03C and U03D, transistor Q04, capacitors C13 to C16 and resistors R013 to R016.

The first 20mA current sink includes resistors RA22, amplifiers U22C and U22D, transistor Q22, capacitors C25 to C28 and resistors R025 to R028.

The second 20mA current sink includes resistors RA23, amplifiers U23A and U23B, transistor Q23, capacitors C29 to C32 and resistors R029 to R032.

The 50mA current sink includes resistors RA24, amplifiers U23C and U24D, transistor Q24, capacitors C33 to C36 and resistors R033 to R036.

The first 200mA current sink includes resistors RA42, amplifiers U42C and U42D, transistor Q42, capacitors C45 to C48 and resistors R045 to R048. The second 200mA current sink includes resistors RA43, amplifiers U43A and U43B, transistor Q43, capacitors C70 and C50 to C52 and resistors R049 to R052.

The 500mA current sink includes resistors RA44, amplifiers U43C and U44D, transistor Q44, capacitors C53 to C56 and resistors R037 to R041 and R053 to R057.

The 2Amp current sink includes resistors RA62, amplifiers U62C and U62D, transistor Q62, capacitors C65 to C68 and resistors R066 to R068 and R070 to R072. A heat-sink HS2 is mounted to transistor Q62.

The current sinks are arranged into three groups. The first group includes the 1 mA, 2mA and 5mA current sinks. The second group includes the 20mA and 50mA current sinks. The third group includes the 200mA and 500mA current sinks. The fourth group includes the 2Amp current sink.

The outputs of a digital potentiometer array U01 are coupled to the first group of current sinks. The output of amplifier U06A is coupled to the top of each potentiometer element in the array U01. A capacitor C17 serves as a bypass for the supply to the digital potentiometer array U01.

The outputs of a digital potentiometer array U21 are coupled to the second group of current sinks. The output of amplifier U06B is coupled to the top of each potentiometer element in the array U21. A capacitor C37 serves as a bypass for the supply to the digital potentiometer array U21. The outputs of a digital potentiometer array U41 are coupled to the third group of current sinks. The output of amplifier U06C is coupled to the top of each potentiometer element in the array U41. A capacitor C57 serves as a bypass for the supply to the digital potentiometer array U41.

The outputs of a digital potentiometer array U61 are coupled to the fourth group of current sinks. The output of amplifier U06D is coupled to the top of each potentiometer element in the array U61. A capacitor C77 serves as a bypass for the supply to the digital potentiometer array U61.

A precision current waveform is made to flow through the battery bank by applying a test waveform voltage produced by a waveform generator to the base of one or more of the transistors Q01 , Q02, Q03, Q04, Q22, Q23,

Q24, Q42, Q43, Q44 and Q62 by an associated amplifier U02B, U02D, U03B, U03D, U22D, U23B, U24D, U42D, U43B, U44D or U62D. As the test waveform voltage applied to the base of a transistor varies, a similarly varying current flows through the collector of the transistor and, subsequently, through the battery bank under test. Each amplifier U02B, U02D, U03B, U03D, U22D, U23B, U24D, U42D, U43B, U44D and U62D includes feedback from the emitter of the associated transistor Q01 , Q02, Q03, Q04, Q22, Q23, Q24, Q42, Q43, Q44 and Q62. This feedback provides for closed-loop control of the transistor collector currents and also minimises distortion effects in the base-emitter junction of the transistors.

The test waveform is applied to those transistors Q01 , Q02, Q03, Q04, Q22, Q23, Q24, Q42, Q43, Q44 or Q62 that are needed in order to sink the required amount of current. Potentiometer arrays U01 , U21 , U41 and U61 are used to enable and calibrate the voltage level applied to the base of the transistors. Amplifiers U02A, U02C, U03A, U03C, U22C, U23A, U23C, U42C, U43A, U43C and U62C function as differential sensing amplifiers which provide feedback to the waveform generator for calibration purposes of the voltage waveforms appearing across the resistors that are coupled to the collectors of the transistors Q01 , Q02, Q03, Q04, Q22, Q23, Q24, Q42, Q43, Q44 and Q62. The feedback voltage waveform is rectified to produce a DC voltage (designated as CalVolts), which is read by a precision current sink controller (see Fig. 15G). The precision current sink controller determines the value of calibration offset required for each potentiometer U01 , U21 , U41 and U61 so that the correct amount of current is sunk by each current sink 80. The precision current sink controller stores the calibration offset values in memory for future use in controlling the resistances of the digital potentiometers. If the stored calibration offset value associated with a particular potentiometer is used to set the resistance of that potentiometer, this will enable the transistor associated with that potentiometer to sink the correct amount of current. The resistance of each potentiometer can also be controlled to turn the associated transistors off so that those transistors are unable to sink current.

In the preferred embodiment, the transistors Q01 , Q02, Q03, Q04, Q22, Q23, Q24, Q42, Q43, Q44 and Q62 are turned on by applying a voltage waveform having a peak to peak amplitude of approximately 1V across the resistors coupled to the emitters of the transistors. The amplitude of the voltage waveform applied to each transistor will vary in accordance with the resistance of the potentiometers. The average value of the voltage waveform is set to approximately 0.6V thereby permitting Class A operation of the transistor stage with minimal additional average current.

Collective monitoring of all of the currents sunk by the various current sinks 80 is accomplished by the precision current sink controller monitoring the voltage across resistor R017. Resistor R017 is coupled to a connector J05 and diodes D08 to D12. Diodes D08 to D12 are power diodes which reduce the power dissipation of transistors Q01 , Q02, Q03, Q04, Q22, Q23, Q24, Q42, Q43, Q44 and Q62. The inputs of an amplifier U07D are coupled across the resistor R017 by resistors R103, R104 and capacitors C95, C96. A resistor R106 and a capacitor C97 provide negative feedback around the amplifier U07D. Further, the amplifier U07D is coupled to digital potentiometer U61 . A resistor R107 and a capacitor C98 are coupled to the wiper of a potentiometer 61 .

A reference voltage supply includes a regulator U03, amplifiers U07B and U07C, capacitor C60 and resistors R096 to R100 and R105. The waveform generator circuitry includes a sine wave generator U05, amplifiers U04A to U04D and U07A, resistors RA71 , R042, R018, R019, R092 to R095, R120 and R121 , capacitors C71 to C73 and C40, C41 , and diodes D06, D07.

For most applications, a sine wave voltage waveform generated by the sine wave generator U05 and having a frequency of approximately 1000Hz is applied to the transistors Q01 , Q02, Q03, Q04, Q22, Q23, Q24, Q42, Q43, Q44 and Q62. In order to suit the frequency of the transducer band-pass filters, this frequency can be slightly offset by the transducer to ensure maximum output of each transducer filter. The precision current sink controller can disable the sine wave generator U05 and generate waveforms other than a 1000Hz sine wave. The signal generated by the precision current sink controller is coupled via resistor R043 and capacitor C74 to the same analogue network used by the sine wave generator U05. The current sinks 80 can also be operated to cause a calibrated

DC current up to 3Amps to flow through the battery bank. The cell responses to step currents can be measured by rapidly switching the DC current on and off.

Further, the use of an arbitrary waveform, such as a square wave, to operate the transistors Q01 , Q02, Q03, Q04, Q22, Q23, Q24, Q42, Q43, Q44 and Q62 permits a number of other characteristics of the cells to be monitored. This is achieved by retuning the band-pass filters in the transducers and measuring the frequency spectrum of the resulting waveform.

Referring to Figs. 15A to 151, the second module of the controller 25 also includes: alarm interface 87; a negative rail generator 113; a fan output driver 114; an auxiliary interface 115; fibre optic detectors 70; fibre optic emitters 69; external data connection 26; precision current sink controller 116; an ambient and heat sink temperature sensor circuit 117; and power supply/regulator 81.

Alarm interface 87 includes relays RL1 and RL2, transistors Q5 and Q6, diodes D22 and D23, resistors R085 to R088, and connectors J21 and J22. System alarms are indicated through software or the clean NC/NO contacts of relays RL1 and RL2 which are coupled to external devices. On power-up of the system 90, relays RL1 and RL2 are energised for fail-safe operation. Although relays RL1 and RL2 are the major and minor alarm relays by default, they may be configured to perform other functions.

Negative rail generator 113 includes a -5V generating circuit U14, diodes D20 and D20, resistors R078 to R080, resistors R101 and R102 and capacitors C90 to C94. The negative rail generator 113 generates -5V for the sine wave generator U05. Fan output driver 114 includes a transistor Q05, diode D03, resistors R122 and R123 and connectors J 11 and J12.

Auxiliary interface 115 includes connector J07. The auxiliary interface 115 enables the connection of local data devices to the controller 25. The fibre optic emitters 69 and detectors 70 enable the controller 25 to communicate with the transducers.

External data connection 26 includes data communication circuits U13 and U15, connectors J03, J04 and J09, jumpers JP1 , resistor R001 , capacitors C82 to C85 and capacitors C75 and C76. Precision current sink controller 116 includes micro-controller

U70, logic circuit U16, regulator U12, opto-couplers U10 and U11 , resistors R022, R058, R059, R076 to R078, R083, R084, R089 to R091 , R108 to R1 12, capacitors C49, C74, C80, C81 , crystal X1 , beeper BP1 and connectors J08 and J10. Activating beeper BP1 indicates faults and keyboard operation.

The ambient and heat sink temperature sensor circuit 117 includes sensor circuits U17 to U19, amplifier U20A, diode D24, resistors R1 13 to R119 and capacitors U18, U19.

Power supply/regulator 81 includes a 5V regulator U72, a switched-mode power supply CV03, opto-couplers U08 and U09, diodes D01 ,

D05, inductors L1 , L2, capacitors C18 to C20, C38, C39, resistors R020, R021 , R073, R074, R075, R082 and connectors J01 , J02. A heat sink HS1 is mounted on regulator U72.

Power for the controller 25 is derived from the converter 24 via

J01 or an AC plug pack via J02. If an AC plug pack is used, the power supplied by the plug pack takes precedence over the supply from the converter 24 such that the supply from the converter 24 is effectively disconnected from the controller 25.

Regulator U72 powers the micro-controller 82 and associated circuits.

Switched-mode power supply CV03 powers the precision current sink controller 116.

Communications is provided between the precision current sink controller 116 and the converter 24 via connector J01. If the converter 24 is coupled to two battery banks, opto-couplers U08 and U09 are used to control which battery bank the current sinks 80 are coupled to. Opto-couplers U08 and U09 can also be used for communicating with more elaborate converters 24, particularly in cases where temperature and multiple battery bank selection may be required. In this case the opto-transmission and receiving circuits do not rely on state information but use data transmission to manage battery bank connectivity. Referring to Figs. 16A to 16C, the converter 24 interfaces the controller 25 to the battery bank. The converter 24 is designed to couple with a battery bank having a particular output voltage range. In the illustrated embodiment, the converter 24 is designed to couple with a 48V bank of lead- acid battery cells. The illustrated converter 24 can be suitably modified to enable coupling with a battery bank of different potential. The converter 24 includes a power source for the controller 25 and a power source for the s precision current sinks 80.

The converter 24 includes a voltage regulator U01 , a switched- mode power supply module CV01 , amplifiers U02A and U02B, transistors Q03, Q23, Q24, Q43, diodes D01 to D06, D11 , D12, D21 , D22, D40, D41 , D42, zener diode Z01 , relays RL01 , RL02, RL03, resistors R03 to R12, R26 o to R33, R40, R41 , R43, R44, R50 to R53, potentiometers VR01 , VR21 , capacitors C02, C03 and connectors J01 ', J11 , J21 and J05.

A first battery bank is coupled to the converter 24 via connector J11. A second battery bank can be coupled to the converter 24 via connectorJ21. s The power source for the controller 25 is obtained from the switched-mode power supply module CV01 which is coupled to connectors J11 and J21 via diodes D11 , D12, D21 and D22. In the preferred embodiment, module CV01 provides a constant 12V isolated supply over an input range of 36V to 72V. The 12V output of CV01 is used by the converter 0 24 and is also made available to the controller 25 via connector J01 '.

Pins 2 and 4 of J01 ' enable the converter 24 to communicate with the precision current sink controller 116 which forms part of the controller 25. In the preferred embodiment, the TxD input to transistor Q24 is used to select which battery bank is coupled to the current sinks 80. Confirmation 5 that a particular battery bank has been coupled to the current sinks 80 is provided to the controller 25 via the RxD output.

In the preferred embodiment, the power source for the precision current sinks 80 is within 10% of 12V and little sink current is lost from the circuit. This is facilitated through the use of a pre-regulator in the form of 0 CV01 and a final regulator in the form of U01 to provide a steady 12V to the precision current sinks 80.

On application of power to the precision current sinks 80, relays RL02 and RL03 are disabled. As the input voltage to the converter 24 rises, CV01 activates and commences supplying power to U02A and U02B.

The voltage at the collector of Q43 rises momentarily to the input voltage less the diode drops arising from D01 to D06. As zener diode Z01 reaches 16V, the emitter of Q43 is kept at 14.5V, which is an acceptable input voltage for the regulator U01. There is little power dissipation by the regulator U01 as most of the power dissipation is through Q43.

A first Schmitt trigger comparator is formed by amplifier U02A, resistors R06 to R12 and potentiometer VR01. A second Schmitt trigger comparator is formed by amplifier U02B, resistors R26 to R32 and potentiometer VR21.

The Schmitt trigger comparators operate together and compare the reference voltage level set by potentiometers VR01 and VR21 with the potential of the battery bank. If the potential of the battery bank exceeds a reference voltage level, the output of the comparator associated with the exceeded reference voltage goes high causing the associated transistor Q03 or Q23 to saturate and activate the associated relay RL02 or RL03. Activating relay RL02 switches in resistors R40 and R41 , while activating relay RL03 switches in resistors R43 and R44. Switching in resistors R40, R41 or resistors R43, R44 provides additional voltage drop in the collector circuit of transistor Q43, thereby decreasing the dissipation requirements of the transistor Q43.

The first Schmitt trigger comparator and the second Schmitt trigger comparator are configured to switch at 50V and 40V, respectively. The foregoing describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

Claims

CLAIMS:

1. A battery monitoring system for monitoring cells in a battery bank where the cells are interconnected between output terminals, the system having: a controller having a plurality of current sinks that are operable to supply an alternating current of a predetermined magnitude to the bank such that the predetermined current is caused to flow through the cells; and a plurality of transducers arranged in series with one another and coupled to the controller, wherein each transducer is coupled to electrodes of an associated said cell and each said transducer being adapted to measure cell characteristics and the impedance between an electrode of an associated cell and a link connected to the electrode, at least some of the plurality of transducers being powered by cells of the bank, the transducers functioning to transmit information to and receive information from the controller, the transducers measuring characteristics of the cells when the predetermined current flows through the cells.

2. The system of claim 1 , wherein the cell characteristics measured by the transducers includes the terminal voltage of the cells.

3. The system of claim 1 , wherein the cell characteristics measured by the transducers includes cell impedance.

4. The system of claim 1 , wherein the cell characteristics measured by the transducers includes the operating temperature of the cells.

5. The system of claim 1 , wherein the controller is powered from the output terminals of the battery bank.

6. The system of claim 1 having a DC to DC converter coupled to the output terminals and the controller, wherein the converter is adapted to supply power to the controller.

7. The system of claim 6, wherein the DC to DC converter is adapted to reduce the voltage at the terminals for supply to the controller.

8. The system of claim 1 , wherein the outputs from selected ones of the current sinks are summed to produce the AC current of predetermined magnitude.

9. The system of claim 1 , wherein the first three transducers in a string of series connected transducers derive their power supply partially from the controller whilst the other transducers in the string are powered from cells in the bank. s

10. The system of claim 1 , wherein at least one of the transducers has a micro-controller which is coupled to the controller.

11. The system of claim 10, wherein the transducer has an analogue to digital converter coupled to the micro-controller.

12. The system of claim 11 , wherein the transducer has a DC o amplifier coupled to the analogue to digital converter.

13. The system of claim 12, wherein the DC amplifier is coupled to the electrodes of an associated cell.

14. The system of claim 11 , wherein the transducer has a rectifier coupled to the analogue to digital converter. s

15. The system of claim 14, wherein the transducer has a bandpass filter coupled to the rectifier.

16. The system of claim 15, wherein the transducer has an AC amplifier coupled to the band-pass filter.

17. The system of claim 16, wherein the AC amplifier is coupled to o the electrodes of an associated cell.

18. The system of claim 17, wherein the transducer has an analogue multiplexer coupling the AC amplifier to the electrodes of the associated cell, the analogue multiplexer being controlled by the microcontroller. 5

19. The system of claim 10, wherein transducer includes opto- couplers which are coupled to the micro-controller, the opto-couplers enabling the micro-controller to transmit information to and receive information from the controller.

20. The system of claim 10, wherein the transducer includes a fibre 0 optic emitter and a fibre optic detector which are coupled to the microcontroller, the fibre optic emitter and fibre optic detector enabling the microcontroller to transmit information to and receive information from the controller.

21. The system of claim 10, wherein the transducer includes a temperature sensor coupled to the micro-controller.

22. The system of claim 1 , wherein the controller includes a micro- controller.

23. The system of claim 22, wherein the micro-controller is coupled to the current sinks.

24. The system of claim 22, wherein the controller includes a user interface for enabling a user to configure the system, the user interface being coupled to the micro-controller.

25. The system of claim 24, wherein the user interface includes a display and a keyboard.

26. The system of claim 22, wherein the controller includes a data communication interface which is coupled to the micro-controller.

27. The system of claim 1 , wherein the controller and the transducers are coupled together by a fibre optic cable.

28. The system of claim 1 , wherein the system is configured to monitor the cells in a plurality of battery banks.

29. The system of claim 1 , wherein the alternating current supplied by the current sinks is sinusoidal.

30. The system of claim 1 , wherein the alternating current supplied by the current sinks is non-sinusoidal.

31. The system of claim 1 , wherein at least one of the transducers is integrally formed with an associated one of the cells.