GB2243695A

GB2243695A - Battery testing

Info

Publication number: GB2243695A
Application number: GB9009907A
Authority: GB
Inventors: Alwyn Peter Ogborn
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-05-02
Filing date: 1990-05-02
Publication date: 1991-11-06
Anticipated expiration: 2010-05-02
Also published as: GB2243695B; EP0527214A1; WO1991017451A1; AU7773191A; GB9009907D0

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 The invention relates to battery testing.

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 to supply power at 120 volts may have 100 cells each of voltage 1.2 volts linked in series.

Since each cell may weigh of the order of a few kilograms, such installations are bulky and stationary.

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.

According to the invention, there is provided a battery testing system for testing an electrical battery which has a plurality of electrical cells, the system comprising : means for reading a plurality of voltages of said plurality of cells; and at least one logic unit arranged to control reading of said plurality of voltages in a pre-determined 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 said plurality of poles.

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

Preferably said logic unit is a computer arranged to control said sequence of reading.

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 voltages of said poles.

preferably said monitor means further comprises a plurality of visual indicators for indicating individual cells according to pre-defined conditions.

preferably said indicators are light emitting devices.

Preferably the battery testing system further comprises one or more display means for display of test parameters and/or test results.

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

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

Preferably said data storage means is a computer memory device for storage of said test parameters and/or results.

Said logic unit may be arranged to control said display of test parameters and/or results.

Said logic unit may be further arranged to control passage of data to and/or from said data storage means.

Preferably the battery testing system further comprises a reference clock for designating the time elapsed from the start of a said sequence.

The system may have a plurality of modules, each module being arranged for connection to an associated set of cells.

The modules may each be connected to an assignment unit.

The invention includes a method of testing an electrical battery having a plurality of electrical cells, the method comprising using at least one logic unit to read a plurality of voltages of said plurality of cells, the logic unit being used to control reading of said plurality of voltages in a pre-determined sequence.

The invention includes an electrical battery or cell connected to, or embodying therewithin, a battery testing system according to the invention.

By way of example, a specific embodiment 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 monitoring system according to a preferred embodiment of the present invention; Figure 2 shows part of a typical output of the system, for a battery of cells; and Figure 3 shows part of another typical output of the system, for another battery of cells.

The system includes a plurality of monitor modules 10, an assignment unit 20, a decoder 30, an electronic voltmeter 40, a computer 50, 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 C11 to Cnm, 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 C11 to Cim as shown in Figure 1. In this preferred 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 C11 to C1m.

A number N of monitor modules are connected to assignment unit 20 by data buses 12. 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 C11 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 C1m 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 C2m, 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 Cnm.

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 100A flows through the shunt, and a voltage of 100mV 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. 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 preferred embodiment may have the advantage of providing easy identification of cells which discharge to a voltage which is below a preset voltage, in a time which is shorter than a prescribed time.

On completion of the test period, the preferred 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 preferred 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 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.

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 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 also 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.

The preferred embodiment is capable of testing each individual cell in a battery without the need to disconnect each cell from its neighbouring connected cells, and of identifying the condition of each individual cell in the battery.

Thus, the preferred embodiment may have the advantage of giving automated monitoring of a battery discharge over a prolonged test period, without the need for continuous supervision.

Whilst the invention has been described hereinabove with reference to a preferred embodiment, 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 series with other cells, or any connection combination or method thereof.

Although in general, electric stand-by batteries are stationary permanent installations, 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.

Selected features of the above described preferred 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 also 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.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A battery testing system for testing an electrical battery which has a plurality of electrical cells, said system comprising: voltage reading means for reading a plurality of voltages of said plurality of cells; and at least one logic unit 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 3, in which a pole of each cell of the battery is connected to at least one pole of another said cell of the battery, said connection remaining intact during reading of the voltages.

5. A battery testing system according to claim 2, 3 or 4 wherein said logic unit is a computer arranged to control said sequence of reading.

6. A battery testing system according to any one of claims 2 to 5, wherein 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.

7. A battery testing system according to claim 6, wherein said monitor means further comprises a plurality of visual indicators for indicating individual cells which accord to pre-defined conditions.

8. A battery testing system according to claim 7, wherein said indicators are light emitting devices.

9. A battery testing system as claimed in any one of claims 2 to 8, further comprising one or more display means for display of test parameters and/or test results.

10. A battery testing system according to claim 9, 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.

11. A battery testing system as claimed in any one of the preceding claims, further comprising at least one data storage means.

12. A battery testing system according to claim 11, as appendant to claim 9, wherein said data storage means is a computer memory device for storage of said test parameters and/or results.

13. A battery testing system according to claim 12, wherein said logic unit is arranged to control said display of test parameters and/or results.

14. A battery testing system according to any one of claims 11 to 13, wherein said logic unit is further arranged to control passage of data to and/or from said data storage means.

15. A battery testing system according to any one of the preceding claims further comprising a reference clock for designating the time elapsed from the start of a said sequence.

16. A battery testing system constructed and arranged substantially as hereinbefore described, with reference to figure 1 of the accompanying drawings.

17. A method of testing an electrical battery having a plurality of electrical cells, the method comprising using a voltage reading means to read a plurality of voltages of said plurality of cells, and using a logic unit to control reading of said plurality of voltages in a predetermined sequence.

18. A method as claimed in claim 17, in which each said cell has at least one pole connected to another said cell and the plurality of voltages comprises the voltages of each said pole.

19. An electrical battery or cell connected to, or embodying therewithin, a substantial part of a battery testing system according to any one of the preceding claims.