WO1991017451A1

WO1991017451A1 - Battery testing

Info

Publication number: WO1991017451A1
Application number: PCT/GB1991/000705
Authority: WO
Inventors: Alwyn Peter Ogborn
Original assignee: Alwyn Peter Ogborn
Priority date: 1990-05-02
Filing date: 1991-05-02
Publication date: 1991-11-14
Also published as: EP0527214A1; GB9009907D0; AU7773191A; GB2243695A; GB2243695B

Abstract

The invention relates to the field of battery testing. In battery installations such as may be used for emergency power supplies or for computer installations, a plurality of cells are used, each of which needs to be periodically checked for the general condition of charge storage capability, during routine maintenance. This requires checking the voltage and current of each cell over a period of time and involves individually disconnecting each cell from the battery. The present disclosure concerns a system for testing a battery having a plurality of cells. The system comprises a plurality of modules (10) connected to the cells (C) of the battery, an assignment unit (20), a decoder (30), a voltmeter (40), a computer station (50) for controlling the system, and display means (80) for displaying test results of the battery. The modules are connected with the battery cells through a plurality of leads (11) without the need for disconnecting each cell of the battery. The principal use of the disclosed system will be for automated testing of such batteries.

Description

BATTERY TESTING

TECHNICAL FIELD

The invention relates to battery testing.

BACKGROUND ART

In known battery installations, for example those which are- used, as emergency back-up power supplies for large computer installations', oil rigs, or the like, periodic checks on the condition of the battery must be made for reasons of safety and maintenance.

Conventional battery installations can have a large number of energy cells linked in series. For example, a battery which is designed to supply power at 120 volts may have 100 cells each of voltage 1.2 volts linked in series.

A conventional method of testing such a battery is to charge up the whole battery, and then monitor the voltage of the whole battery as it discharges across a known electrical load. If the condition of an individual cell is to be tested, the cell must be disconnected and discharged across another electrical load, noting the voltage drop during discharge.

Since each cell may weigh of the order of a few kilograms, such installations are bulky and stationary and movement of the installations may risk spillage of hazardous chemicals. Therefore, movement of the battery installation is to be avoided. Also, since cells are generally connected in series and are often held in rack systems, it is often inconvenient to individually disconnect each cell for testing.

DISCLOSURE OF THE INVENTION

The present invention addresses some of the above mentioned technical problems.

According to one aspect o the present invention, there is provided a battery testing system for testing an electrical battery which has a plurality of electrical cells, characterised in that the system comprises:- voltage reading means for reading a plurality of voltages of said plurality of cells; and at least one control means unit arranged to control reading of said plurality of voltages in a predetermined sequence.

Usually each cell of the battery to be tested will have at least one pole, and the system will have means for reading a plurality of voltages of a said plurality of poles.

One or more said voltages may be read at a pole of each cell of the battery.

Preferably, said voltage reading means includes one or more monitor means arranged to be connected to one or more of said poles, said monitor means arranged to produce one or more data signals in response to the voltages of said poles. Preferably, a said monitor means further comprises one or more visual indicators for indicating individual cells which accord to pre-defined conditions.

Preferably, said visual indicators are light emitting devices.

Preferably, said control means is a computer arranged to control said sequence of reading.

Said control means may be further arranged to control a display of test parameters and/or results.

Preferably , the test results include a plot of the difference in voltage between opposite poles of a single said cell over a period of time.

The battery testing system may further comprise one or more display means (80) for display of test parameters and/or test results.

Preferably, the battery testing system further comprises at least one data storage means.

Where a data storage means is provided, the control means may be arranged to control passage of data to and/or from the data storage means.

Preferably, said data storage means is a computer memory device for storage of test parameter data and/or test result data. Preferably, the battery testing further comprises a reference clock for designating the time elapsed from the start of a said sequence.

The invention includes an automated battery testing apparatus for testing the charge storage capability of a battery having a plurality of cells, said apparatus characterised by comprising : a plurality of voltage reading means each connected to one or more cells of the battery for reading a plurality of voltages of said cells; assignment means connected with said plurality of voltage reading means, and arranged to assign to each of said voltage reading means a task of reading at least one said voltage; and control means arranged to activate said reading of voltages such that the voltage of each cell is read in a controlled sequence of reading.

According to another aspect of the present invention, there is provided an automated battery testing apparatus for testing a battery, said battery comprising a plurality of charge cells each having at least one pole, characterised in that the apparatus comprises: a plurality of monitor modules, each module capable of reading a voltage of one or more cells connected thereto; a data transmission means connected between said monitor modules and arranged to carry data between said monitor modules, wherein said plurality of modules are connected in a chain by the data transmission means such that data is capable of being transmitted along the chain from one said monitor module to another said monitor module and the monitor modules are arranged such that the data is transmissible via the monitor modules. According to yet another aspect of the present invention there is provided an automated battery testing apparatus for testing a battery, the battery comprising a plurality of charge cells each having at least one pole, characterised in that the apparatus comprises; a plurality of monitor modules, each module capable of reading a voltage of one or more cells connected thereto; and a data transmission means arranged to carry data between the monitor modules, wherein the monitor modules are each connectable to the data transmission means such that each monitor module is capable of performing a voltage reading operation of the cells connected thereto substantially independently of a voltage reading operation of any other monitor module.

The invention includes a monitor module for reading a plurality of voltages of a battery, said module characterised by having : a scanner circuit including a plurality of connection leads for attachment to a plurality of poles of the battery , the circuit being capable of addressing each connection lead in a sequence and thereby reading a voltage of each attached pole; a calibration circuit for comparing the voltage of each attached pole to a reference voltage; and means for input or output of data respectively to or from the module, wherein said module is connectable to one or more other modules and a control means and is capable of co-operating with the other modules and the control means for performing a battery testing operation. The invention includes a method of testing an electrical battery having a plurality of electrical cells, the cells having a plurality of poles, said method characterised by having the steps (i) and (ii) of :

(i) reading in sequence a voltage of each pole of a set of three or more poles of the battery; and (ii) recording the voltage of each pole together with data corresponding to the times elapsed between the start of a test period and the reading of each respective pole voltage.

An advantageous effect of the invention may be that a battery monitoring system capable of testing the condition of each individual cell in a battery without the need to disconnect each cell from its neighbouring connected cells, and of identifying the charge storage capacity of each individual cell in the battery may be provided.

The invention may also have the advantageous effect that automated monitoring of a battery discharge over a prolonged test period may be made without the need for continuous supervision by a human operator.

A further advantageous effect of the invention may be that by a reduction in the time taken to perform a scan operation in a battery test, a greater number of voltage and/or current readings may be provided in a test period of a battery of cells. DESCRIPTION OF THE DRAWINGS

By way of example, specific embodiments of a battery monitoring system will now be described, with reference to the accompanying drawings, in which :-

Figure 1 is a schematic block diagram of a first monitoring system according to a first embodiment of the present invention;

Figure 2 shows part of a typical output of the system, for a battery of cells;

Figure 3 shows part of another typical output of the system, for another battery of cells;

Figure 4 shows schematically a second monitoring system according to a second embodiment of the present invention; and

Figure 5 shows schematically a third monitoring system according to a third embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The applicant contemplates that the best mode for carrying out the invention is as now described.

Referring to Figure 1 of the accompanying drawings, the first monitoring system includes a plurality of monitor modules 10, an assignment unit 20, a decoder 30, an electronic voltmeter 40, a control means (50) in the form of a computer or computer logic unit, a clock unit 60, an electrical load 70, a display 80, and a shunt 90.

A typical electric battery to be monitored by the system comprises an array of electric energy cells C_π to Cm-., each cell C being connected in series to adjacent neighbouring cells. Each monitor module 10 is attached to poles of a corresponding plurality of cells by connection leads 11. For example, the first monitor module has a number m of connection leads, each lead being respectively connected to a pole of one of the cells C_u to C_lm as shown in Figure 1. In the first embodiment, the number m is eight, although in other embodiments it could be for example 16, 32, 64 or any other integer number. Connection of a lead to a cell is made by a secure electrically conducting fastening, for example a clamp which fits onto the battery pole, and which is connected with the lead via a 4mm plug with an internal fuse. Each module has a set of light emitting diode warning lights 12, each light corresponding to one of the connected leads 11 and one of the corresponding cells C_n to Cι -

A number N of monitor modules are connected to assignment unit 20 by data buses 14. Each monitor module is addressed in turn, and the voltage of a positive (or negative) pole of each cell is read sequentially along the cell array in a serial scan operation. For example, at the start of the serial scan operation, the first module is addressed and the voltage at the positive pole of the first cell C_u is read. A signal which corresponds to the voltage at the positive pole of the first cell is transferred via the assignment unit to the decode unit, and is input to the computer 50. The computer records the voltage for that first cell, together with the time at which the voltage reading was taken, referenced to the start of the monitoring operation. The Clock 60 provides a time keeping signal, which is input to the computer 50.

The computer then addresses the second cell C₁₂ via the first module and reads voltage data at the positive pole of the second cell in the same manner as above, and so on for all the remaining cells C₁₃ to C_lm connected to the first module.

Next the second module is addressed by the computer and the voltages at the positive poles of the cells C₂₁ to C_2m, which are connected to the second module, are recorded and so on for further modules up to the last module N and the final cell C_nm.

If the total number of cells in the battery is not a multiple of m, the number of leads per module, then the voltage readings from any remaining unattached leads on the final module are ignored.

The voltage readings at the poles of each cell are collated at the end of the scan. The voltage across each individual cell is deduced from the above voltages by the suitably programmed computer 50.

The current flowing through the battery is determined by reading the voltage across a shunt 90 with voltmeter 40. An output signal from the voltmeter which relates to the current is input to the decoder 30.

For example, if a current of 100 A flows through the shunt, and a voltage of lOOmV drops across the shunt, then 1 millivolt of voltage read by the millivoltmeter corresponds to 1A of current flowing through the shunt and load.

The system then begins a second scan operation and records the voltage data as before, and continues on subsequent scans until the end of the test period is reached and scanning terminates. Each scan operation preferably has a duration of the order of one minute. The test period may be prolonged over a period of hours. Activation of the scanning operations is controlled by the computer 50.

The variation of the cell voltage over the test period depends on the condition of the cell and the value of the electrical load 70. For a given electrical load 70, the voltage across a cell in poor condition is reduced more quickly than for a cell in good condition.

A trigger voltage level may be set, such that if any cell falls below this set voltage, the corresponding light on the corresponding monitor module is activated and the cell can be easily identified either during or at the end of the test period. Thus, the described first embodiment may have the advantage of providing easy identification of cells which discharge to a voltage which is below a pre-set voltage, in a time which is shorter than a prescribed time.

On completion of the test period, the first monitoring system displays for each cell the variation of cell voltage against time over the complete test period. From a consideration of the voltage across each cell over the test period, and the current flowing through the battery over the test period, the capacity of each cell is calculated in ampere hours, and also displayed. Each cell capacity may be displayed as a percentage of rated cell capacity; where the rated cell capacity is the specified capacity of an average newly manufactured cell. Individual newly manufactured cells may have a capacity slightly above or below the rated capacity.

The first monitoring system may also display an overall battery voltage across terminals of the battery, and/or an average load current through the battery.

From the above display, the condition of each individual cell may be assessed. The display may be in the form of a video picture, paper print out or other hard copy, and may be presented in the form of a graph or a table of numbers. The visual display and processing of data is also controlled by the suitably programmed computer 50.

Figure 2 of the accompanying drawings shows one example of a possible paper print-out, and although Figure 2 shows a print-out for only four cells, it will be appreciated that in practice there will be a print-out for each cell. The print is a plot of cell voltage against time elased, from the start of the test period.

Figure 2 relates to a test in which healthy cells are not expected to drop below one volt over a five hour test period. Cell number 1 is very unhealthy and has dropped to negligible voltage almost immediately. Cells 2 and 4 are slightly healthier, and maintain adequate voltage for about one hour. Cell number 3 is still healthy after two hours.

Also displayed in Figure 2 is the capacity in ampere hours of each of cells 1 to 4. Cell number 2 has a capacity of 41.5 ampere hours (AH in Figure 2), which represents 19.7% of the rated capacity of the cell, whilst cell number 4 has a capacity of greater than 61.7 ampere hours.

It will be understood that Figure 2 shows an extreme condition, and that in most cases with well maintained batteries, a majority of the cells will prove healthy. However, this embodiment of the invention enables individual unhealthy cells to be pin-pointed immediately, and they can then be repaired or replaced.

Figure 3 of the accompanying drawings shows another example of a possible paper print out for four cells of another, much healthier, battery. The cells of the other battery have a lower rated capacity than those of Figure 2.

Cell numbers 13 to 16 in Figure 3 all maintain a voltage of greater than

1 volt for a period of about 5 hours, and have ampere hour capacities of 90% or more of their rated capacities.

Other information about a battery test, for instance, the name of the customer, the date of the test, the number and type of cells, the battery manufacturer's name, the general use to which the battery is put, the rated capacity of the battery, and the average load current through the battery, may be displayed in any display described herein. For example, in the paper print display described hereinabove, the above other information may be printed on a cover sheet.

The variation of the cell voltage against time elapsed from the start of the test period may be displayed during the test period, so that it may not be necessary to wait until the end of a complete test period before being able to identify cells which are in poor condition. In fact, the fall of a cell voltage below the set level also causes the video display corresponding to that particular cell to be highlighted by a reversal in colour on the monitor screen, as well as the fall being identified by the corresponding monitor light, as aforesaid.

Referring to Figure 4 of the accompanying drawings, a second monitoring system for monitoring a battery comprises a computer 100 having a display 101, a volt meter 102 for reading voltage across a shunt^' 103, and a number R of monitor modules 104_l5 104₂, 104₃ 104_R, and a load 105.

In the second monitoring system, each monitor module 104 has an integer number P of connection leads 107, each lead being connected to a pole of one of the cells 106 of a battery. The number P of connection leads, is preferably 16 and is preferably the same number for each module. However, the number P is not necessarily so restricted, and P may be different for each module. Other values of P may be, for example, 2, 4, 8, 32 or 64.

Each of the monitor modules 104 has a scanner circuit, a calibration circuit, an input port, and an output port. The monitor modules are connected in a chain of one module after the other, by a data transmission means 114 such as a data bus which may be, for example, an RS 232 bus or a similar bus. Data may be transferred over the data bus 114 in a parallel or in a serial manner. The data bus connects an output port of the first module of 104 with the computer. Thus in this configuration, if the module has a number P = 16 of connection leads, then the second monitoring system can monitor 16 cells of a battery. If further modules are required to be added, then the output port of the first monitor module 104_! is connected to the input port of the second module 104₂ and communication between modules and the computer continues via the data bus 114.

The voltmeter 102 is also connected to the computer 100 by a data bus

116. The voltmeter measures the voltage across a shunt resistor 103. Alternatively, the voltmeter 102 can be connected to the modules 104 by the data bus 114 and thence to the computer.

Operation of the second monitoring system will now be described.

Taking as an example a case where only one module (the first module) is present (i.e R = 1); the scanner circuit sequentially addresses each connection lead 1 to P of the first module in a modular scan operation, to serially read the pole voltages of cells connected thereto. The scanner circuit may address each cell in turn under its own localised control routine, or may be subject to control by routine of the computer and act as a "slave" unit thereto for the addressing of each cell connected to the module.

Data corresponding to the voltage present at each pole is fed from the scanner circuit via the data bus 114 to the computer 100 which produces a display output similar to that as described hereinbefore with reference to the first embodiment. Because the scanner circuit communicates directly with the computer, there is no need for a discrete assignment unit or decoder unit.

At the end of a modular scan operation of each of the connection leads 1 to P of the first module, the total voltage across the cells is determined by the computer. The voltage across each individual cell is also determined from the voltages read by the first module.

Where more than one module is used, further modules are connected in a chain as shown in Figure 4 of the accompanying drawings via the data bus 114, each module 104 having its own scanner circuit for scanning cells connected the respective connection leads 1 to P of the module. In this case, a complete scan operation of the battery commences with voltage data being read at the first cell C_π and, where there are R modules, the complete scan operation ends with reading the voltage of the final cell C_R . The complete scan operation comprises a number R of modular scan operations performed consecutively, one after the other for the respective modules 1 to R.

Data may be transferred from the appropriate module to the computer either at the end of the scan, at the end of a modular scan operation, or after a read operation of each particular cell, connected to the module, and where data is not transferred to the computer immediately after reading, the data can be stored in a memory unit of the module pending such transfer. The data is transferred via the output port and data bus.

The chain connected modules are each addressed in turn by the computer for activation of scanning, and then for transfer of data. For example, in a complete scan operation of all the modules, the computer instructs the first module via the data bus and input port of the first module to commence scanning. The scan circuit of the first module scans each cell 1 to P connected to the first module, and voltage data corresponding to voltages read at the poles of the battery which are connected to the leads of the first module is transferred to the computer or stored at the first module as described hereinabove. During this time, each other module is disabled from scanning by instructions from the computer via the data bus and the input ports of the other modules.

Then, after the end of the modular scan operation of the first module, a completion signal is sent from the first module to the computer and the computer disables the first module from further scanning and instructs the second module to perform a modular scan operation. At this stage, the other modules are disabled by the computer. The second module performs a scan operation of its connected cells in the same way as the first module, and the process is repeated for subsequent modules until the end of a complete scan operation of all the cells of the whole battery has occurred. Then, after appropriate data transfers and resetting of the modules, further complete scans of the whole battery are performed to the end of a test period.

The calibration circuit of each monitor compares the voltage read from each connection lead of the monitor with the voltage of a reference lead of the first monitor, to establish the voltage levels of the poles connected to the connection leads compared to voltage of the pole connected to the reference lead. The calibration circuit may also refer to a reference voltage such as may be provided across a fixed reference element, for example, a Zener diode in the calibration circuit.

In a test situation, the computer 100 and display 101 may be kept at the site of the battery for the purpose of testing, and the modules 104 may be portable. In this case, prior to the test period, the system may be physically assembled by connection of the modules to the cells of the battery, connection of the voltmeter 102 and the resistor 103, and connection of the load to the battery. The modules can then be connected via the data bus 114, the voltmeter connected as hereinabove described, and a program containing instructions for operation of the system may be down loaded into the memory of the computer 100 by, for example, use of a floppy disc, a compact disc read only memory or the like, and then the program used to control operation of the system via the computer's logic unit.

Thus, due to the chain construction of the modules, the second monitoring system may be adaptable to fit a range of sizes of battery having variable numbers of cells. The second monitoring system may be easily uprated in cell monitoring capacity by the addition of further modules to the chain.

Referring to Figure 5 of the accompanying drawings, a third monitoring system comprises a computer 200 having a display 201, a volt meter 202 for reading a voltage across a shunt 203, a number R of monitor modules 204_! , 204, ... 204_R, and a load 205. The third monitoring system is similar to the second monitoring system, but in the third monitoring system, the monitor modules 204 are connected with the computer 200 by a parallel data bus 214 such that data or instructions may be communicated between the computer and each one of the monitor modules substantially independently of the other monitor modules, and each monitor module can be addressed or instructed independently of the operation of each other monitor module.

Each module has a scan circuit and an input/output port for connection to the data bus 214. The scan circuits are incorporated into the monitor modules for scanning the cells connected thereto in a serial manner which is substantially the same as the modular scan operation described hereinabove where data may be stored in each module at the end of each scan or passed along the data bus to the computer. However, in the third monitoring system, a plurality of modular scans may all be performed simultaneously with each other.

Thus, in the third monitoring system, a complete scan operation of the battery via a number R of modules is as follows;

The computer 200 instructs via the data bus 214, each module to perform a modular scan operation, resulting in R modular scans being performed simultaneously. When all modular scans are complete, data is transferred via the data bus 214 to the computer, and the computer outputs a display, for example such as described hereinabove, plotting the voltage versus time or current versus time for each cell as well as the total charge holding capacity of each cell and of the battery in ampere-hours.

At the end of the complete scan period, the computer resets all the modules and instructs each module to perform another modular scan, this being a second complete scan operation of the battery. Subsequent complete scans are performed until the end of the test period.

In the third embodiment, simultaneous modular scan operations of modules may have an advantage of reducing the time taken to perform a complete scan operation, and may therefore enable greater resolution in a battery monitoring system, i.e, more voltage and/or current readings per test period. In any one or more of these specific embodiments described herein, whilst voltages of individual cells have been shown to be displayed at the end of a test period, or at the end of each successive scan, the voltage of an individual cell may be determined and/or displayed during a scan operation, after reading a voltage across that particular cell.

Certain modifications of the above embodiments will be apparent to the person skilled in the art. For example, a logic unit may be incorporated into one or more of the monitor modules and may be capable of controlling .the scan operations of the monitor modules and all other essential operations of the system in collecting data. In such a case, a computer and display may be used only for down loading of the data at the test site or remotely therefrom, for processing of data and display of results.

In other specific embodiments, the cells are not limited to being tested consecutively but a particular cell or group of cells, eg a malfunctioning cell, may be selectively tested in preference to other cells.

Whilst the invention has been described hereinabove with reference to certain specific embodiments, it is not intended that the invention is restricted to the features described above. For example, the above described system may be employed in a permanent deployment as a continuous monitoring system in which a warning system, as exemplified by the warning light feature on the monitor modules, can be extended to trigger alarms upon failure of individual cells or the whole battery during discharge of the battery across its normal load. The invention is not restricted for use in testing batteries which have cells connected in series. The invention is also intended for, and applies equally well to, the testing of batteries in which individual cells are connected in parallel with or in series with other cells, or any connection combination thereof.

Although in general, electric stand-by batteries are stationary permanent installations, one or more of the above described preferred embodiment of the invention may be deployed in a permanent, or semi-permanent-installation, or as a portable test facility. Embodiments of the invention may be deployed either in a completely self contained unit, or as part of a permanent fixture. In other embodiments, the invention may be applied to mobile battery units, for example those used in electric vehicles, as part of the equipment of the vehicle.

Selected features of the above described embodiments of the invention may be incorporated into a manufactured battery cell, for example a monitor module may be supplied already integrated into a battery cell unit, for convenient connection thereof.

Any of the data and/or other information may be stored, e.g., on a data disc.

The invention includes embodiments in which data is read and stored at the site of a battery, but data processing and/or display is performed at a site remote from the battery. The processing and display of data and/or test results may be performed on equipment physically unconnected with an embodiment of the invention.

Claims

1. A battery testing system for testing an electrical battery which has a plurality of electrical cells, characterised in that the system comprises :-

voltage reading means (10, 20, 30, 40, 90) for reading a plurality of voltages of said plurality of cells; and

at least one control means unit (50) arranged to control reading of said plurality of voltages in a predetermined sequence.

2. A battery testing system as claimed in claim 1 , in which each cell of the battery to be tested has at least one pole, and the voltage reading means is capable of reading a plurality of voltages of said plurality of poles.

3. A battery testing system as claimed in claim 2, wherein one or more said voltages are read at a pole of each cell of the battery.

4. A battery testing system according to claim 2 or 3, wherein said voltage reading means includes one or more monitor means (10) arranged to be connected to one or more of said poles, said monitor means arranged to produce one or more data signals in response to the voltages of said poles.

5. A battery testing system according to claim 4, wherein a said monitor means further comprises one or more visual indicators (12) for indicating individual cells which accord to pre-defined conditions.

6. A battery testing system according to Claim 5, in which said visual indicators are light emitting devices.

7. A battery testing system according to claim 1, 2 or 3, wherein said control means is a computer (50) arranged to control said sequence of reading.

8. A battery testing system according to Claim 7, wherein said control means is further arranged to control a display of test parameters and/or results.

9. A battery testing system according to claim 8, wherein said test results include a plot of the difference in voltage between opposite poles of a single said cell over a period of time.

10. A battery testing system according to claim 1, 2 or 3, further comprising one or more display means (80) for display of test parameters and/or test results.

11. A battery testing system according to claim 1,2 or 3, further comprising at least one data storage means.

12. A battery testing system according to claim 11 , wherein said control means is arranged to control passage of data to and/or from said data storage means.

13. A battery testing system according to claim 12, wherein said data storage means is a computer memory device for storage of test parameter data and/or test result data.

14. A battery testing system according to claim 1 , 2 or 3, further comprising a reference clock (60) for designating the time elapsed from the start of a said sequence.

15. An automated battery testing apparatus for testing the charge storage capability of a battery having a plurality of cells, said apparatus characterised by comprising :

a plurality of voltage reading means (10) each connected to one or more cells of the battery for reading a plurality of voltages of said cells;

assignment means connected with said plurality of voltage reading means, and arranged to assign to each of said voltage reading means a task of reading at least one said voltage; and

control means (50) arranged to activate said reading of voltages such that the voltage of each cell is read in a controlled sequence of reading.

16. An automated battery testing apparatus for testing a battery, said battery comprising a plurality of charge cells each having at least one pole, characterised in that the apparatus comprises:

a plurality of monitor modules, each module capable of reading a voltage of one or more cells connected thereto; a data transmission means connected between said monitor modules and arranged to carry data between said monitor modules,

wherein said plurality of modules are connected in a chain by the data transmission means such that data is capable of being transmitted along the chain from one said monitor module to another said monitor module and the monitor modules are arranged such that the data is transmissible via the monitor modules.

17. An automated battery testing apparatus for testing a battery, the battery comprising a plurality of charge cells each having at least one pole, characterised in that the apparatus comprises;

a plurality of monitor modules, each module capable of reading a voltage of one or more cells connected thereto; and

a data transmission means arranged to carry data between the monitor modules,

wherein the monitor modules are each connectable to the data transmission means such that each monitor module is capable of performing a voltage reading operation of the cells connected thereto substantially independently of a voltage reading operation of any other monitor module.

18. A monitor module for reading a plurality of voltages of a battery, said module characterised by having : a scanner circuit including a plurality of connection leads for attachment to a plurality of poles of the battery , the circuit being capable of addressing each connection lead in a sequence and thereby reading a voltage of each attached pole;

a calibration circuit for comparing the voltage of each attached pole to a reference voltage; and

means for input or output of data respectively to or from the module, wherein said module is connectable to one or more other modules and a control means and is capable of co-operating with the other modules and the control means for performing a battery testing operation.

19. A method of testing an electrical battery having a plurality of electrical cells, the cells having a plurality of poles, said method characterised by having the steps (i) and (ii) of :

(i) reading in sequence a voltage of each pole of a set of three or more poles of the battery; and

(ii) recording the voltage of each pole together with data corresponding to the times elapsed between the start of a test period and the reading of each respective pole voltage.