GB2222494A

GB2222494A - Battery with charge control

Info

Publication number: GB2222494A
Application number: GB8829574A
Authority: GB
Inventors: Christopher John Fairgrieve
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-08-31
Filing date: 1988-12-19
Publication date: 1990-03-07
Also published as: GB8829574D0; GB8820616D0

Abstract

A battery contains both battery cells (1) and additional electronic circuitry (2) and sensors packaged into one cohesive enclosure. The electronics enable the battery to monitor its own condition; to control charge and discharge rates; to protect the battery against accidental short circuit; to cut-off non-essential discharge to maintain charge capacity and to record date and time of significant events. The battery is provided with a means of measuring specific gravity (20, 24) using no moving parts. The status of the battery can be displayed on a solid state display (13) either on the battery itself or at a remote location. The battery is totally interchangeable with a conventional equivalent. <IMAGE>

Description

BATTERY WITH CHARGE CONTROL SYSTEM The invention relates to a battery comprising battery cell means and a charge control system mounted on the battery cell means and arranged to control the discharging and preferably also the charging of the battery cell means. The invention is particularly suited to the battery being a liquid electrolyte type battery.

In a majority of applications where an internal combustion engine is fitted to a vehicle a lead acid type battery is provided to supply the starting power. This battery is normally re-charged using a conventional regulator system after the engine has started. The regulator governs the charging rate to maintain a floating adequately charged battery during engine running.

In alternative applications such as emergency standby generators the starting batteries are charged by an external circuit either on a regular or an on-demand basis to ensure the charge level is maintained in the batteries.

For certain limited applications these methods of charge control are inadequate. A particular, but not unique example is where a battery is fitted in a sailing vessel to provide starting current for the auxiliary engine and to provide operating current for electric and electronic equipment within the vessel. In this situation the battery may be discharged inadvertently below a safe level. due to neglect or accident. This will prevent the engine being started to replenish the charge. Additional problems occur if the battery is charged at a rate higher than recommended by the manufacturers. This can cause damage to the battery and in extremes can cause explosive levels of hydrogen to be released from the battery into the sailing vessel.Due to the normal position of a sailing vessel battery being low down in the boat in an often inconvenient location the battery is prone to be neglected EP-A 0074444 discloses a rechargeable battery in which battery cell means and a control system are contained within a common housing. The control system is arranged to control the charging of the battery.

EP-A-0163822 discloses a rechargeable battery comprising battery cell means in the lid of which is test circuitry arranged to light different LEDs depending on the level of charge left in the battery cell means.

According to the present invention, a battery comprises battery cell means, a positive or negative first battery terminal, second and third battery terminals both of opposite polarity to the polarity of the first battery terminal, and a charge control system mounted on the battery cell means and arranged to measure the charge level of the battery cell means and to connect the second battery terminal to the battery cell means only when the charge level is above a first predetermined charge level value and to connect the third battery terminal to the battery cell means only when the charge level is above a second predetermined charge level value larger than the first predetermined charge level value.

Thus high priority electrical equipment, e.g. the auxiliary motor of a sailing vessel, may be connected to the second battery terminal and low priority electrical equipment, e.g. lighting and heating, may be connected to the third battery terminal. By choosing an appropriate value for the second predetermined charge level, the low priority equipment can be disconnected to conserve sufficient remaining charge for the operation of the high priority equipment.

As the charge control system is mounted on the battery cell means, the battery as a whole is a single unit that is compact and easy to handle and it may be retrofitted to replace a standard battery merely comprising battery cell means and permanently connected output terminals.

Usually the battery will be a liquid electrolyte type battery, i.e. the battery cell means are liquid electrolyte (e.g. lead acid) type battery cell means. The battery cell means will also usually comprise a plurality of battery cells.

The battery may further comprise a fourth battery terminal having the same polarity as the second and third battery terminals and the charge control system may be further arranged to connect the fourth battery terminal to the battery cell means only when the charge level is above a third predetermined charge level value larger than the second predetermined charge level value The fourth battery terminal is suited for connection to very low priority electrical equipment, since it is the first terminal to be disconnected as the battery cell means discharges.

In one particular embodiment, the first, second and third predetermined. charge level values are set at 0%, 30% and. 70% respectively of the charge level value of the battery cell means when fully charged.

The charge control system may be further arranged to regulate the charging current during charging of the battery cell means in accordance with the measured charge level to set the level of the charging current at the optimum value for the present value of the measured charge level.

The battery cell means may be integral with(i.e.non-detachably mounted on) the charge control system. However, the connection between the two components need not be permanent. In fact, it is preferable for the charge control system to be detachably mounted on the battery cell means. Being able to separate the two components facilitates manufacture and servicing. Preferably, the charge control system is detachably mounted on the top of the battery cell means. If the battery cell means has a fifth battery terminal of the same polarity as the second and third battery terminals and to which the second and third battery terminals are connectable under the control of the charge control system, the second and third battery terminals may be mounted on the charge control system and the charge control system may be arranged to cover the fifth battery terminal.In this way, the fifth battery terminal is not exposed and unauthorised bypassing of the charge control system is prevented. If the fourth battery terminal is provided, it too may be connectable to the fifth battery terminal under the control of the charge control system and mounted on the charge control system.

If the battery cell means has a sixth battery terminal of the same polarity as the first battery terminal and to which the first battery terminal is connected, the first battery terminal may be mounted on the charge control system and the charge control system may be arranged to cover the sixth battery terminal. Thus, all electrical power from the battery cell means flows through the charge control means.

The detachable mounting of the charge control system on the battery cell means may be achieved by the charge control system gripping the fifth and sixth battery terminals. A recess may be provided in the battery cell means and the charge control system detachably mounted in this recess.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a battery in accordance with the present invention, showing an upper lid section containing electronics removed from a lower battery-cells section.

Figure 2 illustrates the battery of Figure 1 when assembled by detachably mounting the upper lid section on the lower batterycells section.

Figure 3 shows a display unit used to indicate the status and condition of the battery.

Figure 4 shows a resonance sensor for measuring the battery electrolyte specific gravity.

Figure 5 illustrates a delay receive sensor for specific gravity measurement.

Figure 6 illustrates a temperature monitor probe.

Figure 7 shows a fuseable link provided on the battery casing.

-Figure 8 shows an overall circuit diagram of the electronics contained in the battery lid.

Figure 9 shows a block diagram schematic of a charge/discharge control circuit shown in Figure 8.

Figure 10 shows a block diagram schematic of the display unit shown in Figure 8.

Figure 11 shows a block diagram schematic of a main control unit shown in Figure 8.

The example of the battery descibed below is designed to monitor its own condition, control the charging and discharge currents to maintain its health, and to report by visual and audio means in accordance with pre-programmed logical instructions.

Referring now to Figure 1 the drawing illustrates the physical construction of the two primary sections of the battery. Batterycells 1 are provided with a lid 2 which contains the electronics and processing equipment to monitor and control the battery condition. Electrolyte filler holes 3 are extended through the lid 2 and fitted with normal cell caps 9 to enable electrolyte level to be replenished, or checked during calibration. Positive and negative terminals 4 and 5 of the battery cells are connected by the circuitry in the lid 2 to respective external terminals 7 and 8. Reduced discharge terminals 10 and 11 are provided on the upper side of the lid 2 as shown. A display module 13 is mounted in a recess in the upper face of the lid. A fuseable link 28 is also fitted on the upper lid.Additional connection points are provided at the edge of the lid, namely an external charge point 6 and a connector 12 to enable a remote display to be connected to the battery. The leads to a resonance sensor 20, a delay receiver sensor 24 and a temperature sensor 26 are also shown.

Figure 2 shows the normal situation where the upper lid section 2 is fitted to and joined with the lower battery-cells section 1.

This is the configuration that would normally be maintained after despatch from the factory until return for repair or replacement of the battery-cells section. In this configuration the battery is totally interchangeable for. a conventional battery. The same size terminals are provided for connection to the alternator, generator or starter motor as appropriate. In all respects in its minimum configuration the battery can replace other equivalent batteries of the same capacity and discharge current capability.

Figure 3 is a schematic of the display module 13 fitted into the upper lid of the battery. A solid state display 14 is used to show to the user: battery charge level as a percentage of full charge; the discharge rate or charge rate as applicable; the time to 30% discharge, 70% discharge and 100% discharge at present rate; the time to full charge; the warning condition; the time in GMT and date; calibration data during manufacturer's setting up.

Four buttons are provided adjacent to the display 14. 15A and 15B are used to calibrate and set up the battery after manufacture.

Button 16A is a master override that isolates all the lid electronics and reverts the battery to a non-intelligent state.

This override can only be used once. It removes all protections and controls and requires factory re-setting. Button 16B is used to acknowledge periodic alarm conditions that occur during the battery's life such as below 30% charge and time to zero charge.

The display provides detailed visual output 14 but also provides tone or voice synthesised output through a speaker 46. The whole display unit 13 can be duplicated at a remote position to the battery itself using the external display port 12 shown in Figures 1 and 2 with an appropriate connecting cable.

Figure 4 shows a schematic of a resonance sensor 22 for measuring the specific gravity (density) of the battery-cells 1. The sensor is placed into one of the individual cells (56 in Fig. 1) in the battery-cells and is connected to the lid 2 by the leads 20. One of the single biggest problems with monitoring the state and condition of a lead acid battery is to be able to measure accurately by a solid state means the density or specific gravity of the electrolyte. One of the sensors used in the sensor 22 is a resonance tube 19 containing a transmitter 17 and a receiver 18 that has holes 21 in the body of the tube 19 to permit electrolyte to enter the resonance chamber. The control electronics causes a variable frequency signal to be transmitted by the transducer 17.

The receiver 18 and sensor monitoring electronics 48 (Figure 11) detect the vibration amplitude set up in the tube 19. The frequency at which maximum amplitude vibration occurs is a direct linear function of the density of the electrolyte in the tube 19.

The sensor conversion electronics converts this frequency to an output of density to the main processing unit 54 (Figure 11). The density/specific gravity measurement requires a temperature correction to establish the battery charge. This temperature is monitored by a temperature probe 27 (Figure 6). An additional means of cross-checking the electrolyte density is to measure the delay of an audio frequency pulse transmitted through the electrolyte and the body of the cell. The speed of sound in a fluid is directly dependent on the fluid density. Hence the transmitter transducer 17 fulfils a dual function. It transmits a variable frequency tuneable to the resonant frequency of the tube 19 for a period sufficient to measure this frequency. It then alters to transmit a series of variable frequency pulses that are received by the receiving probe 25 contained in its own free flooding sensor tube 23. This tube 23 is positioned at the opposite end of the battery to enable the longest pulse propagation delay possible. Again temperature calibration of pulse delay is required.

The measurement of specific gravity using the resonance tube and pulse delay gives a reasonably accurate value of electrolyte density. It does however suffer from manufacturing tolerances in the placing of the tubes relative to each other in the cells, movement in their location due to temperature expansion and contraction of the metallic plates or vibration during life, and manufacturing tolerances of the resonance tube itself.

Accordingly a major effort is made on completion of manufacture and at logical points in the battery's life ( e.g. completion of long 'normal' charge where the condition of the charge and hence density is accurately known) to self-calibrate these sensors.

External calibration is a normal maintenance function to supplement the batteries own self-calibration. The two buttons 15A and 15B on figure 3 are used in conjunction with the display 14 for the purpose.

The battery function as is explained below includes precautions to ensure that the battery-cells are protected throughout their life from accidental or deliberate damage. One aspect of this is protection against accidental short-circuit. To achieve this protection a fuseable link short circuit cut-out 28 is provided on the upper surface of the lid 2. Detail of this cut-out is shown in figure 7. Due to the high current required from the battery (in some applications up to 500A for up to 20 seconds) under normal internal combusion engine starting conditions, several criteria had to be met. A low resistance must be offered under normal operation, however accurate overcurrent protection must be provided. The device must be cheap, reliable and yet easy to replace, and safe in a potentially explosive environment such as a fuel vapour filled boat bilge.The invention includes the cut-out device now described. Two posts 29 are provided, made of copper, each with a larger diameter hole 58 and a smaller clamp screw 57 to lock a horizontal tube 30 and distort it sufficiently to make a good electrical contact around some 80% of the tube 30 circumference. This ensures that the heating effect between the posts 29 and tube 30 is minimised. The tube 30 has a hole 31 drilled through it to produce a smaller cross-sectional area 'fuse' section 59. The diameter of this hole is adjusted depending on the maximum rating of the battery in peak current amps. To protect the user from damage when the fuseable link is destroyed the whole circuit cut-out 28 is covered in a heavy duty commercial rubberised paint.

Turning to the circuit diagram shown in figure 8 the fundamental principles of the battery are expanded and explained. The electronics consists of 3 major components: a display module 13, a charge/discharge controller 39 and a main control unit 40. In addition the short cicuit cut-out 28 and a by-pass 32 are shown.

The operation of the cut-out has been explained above. The bypass is operated by the master override button 16A. Pressing button 16A reverts the battery to its normal dumb state. A signal 34C switches the by-pass to short out the short circuit cut-out 28. Having once been activated the override button 16A is factory resettable only. Signals 34A and 34B trigger various other actions in the main control unit 40 and the charge/discharge control 39 as explained below. Temperature signal 26, pulse delay signal 24, and frequency resonance signals 20, are connected to the main control unit 40. The two battery connections on the battery-cells 4 and 5 are connected as shown to the intelligent battery terminals 7 and 8 on the lid. The 30% and 70% discharge terminals 10 and 11 are shown. Voltage monitoring and operating power for the main control unit 40 is provided by leads 33 and 60.

Other connections between the units 35, 36, 37, 38 and 61 are shown. The external charge connection 6 into the charge/discharge control and the external remote display connection 12 are shown.

Turning to Figure 9 the operation of the Charge/Discharge controller 39 is first explained. This controller carries out two separate, but related primary functions. It ensures that the charge current to the battery-cells 1 from the external source, routed either through the terminal 8 or the external connection 6, is regulated to ensure optimum charge rate for the condition of the battery at that time. The charge/discharge controller 39 also ensures that current is regulated to the 30% 10, 70% 11 and 100% terminals 8. Turning first to the charge control. The main control unit 40 monitors the battery-cells charge condition as explained below. Built into the control unit 40 logic is the temperature/charge curve that represents these particular batterycells 1.Taking an example: if the control unit 40 knows that the charge level in the battery-cells is at 50% of full charge it can calculate the maximum charge current permitted in this charge condition. The charge control circuit 42 will regulate the charge rate to be at or below the maximum permitted rate depending on the charging capability of the external source. The charging rate is monitored by a discharge/charge monitor 45 and signalled to a control unit 40 via a connection 61. The charge/discharge switch 41 also permits charging either via external terminal 8 or external charge point 6. If the master override 16A causes an override signal 34A the charge/discharge switch 41 disconnects links 6, 10, 11, 62 and 63 and reverts the battery back to its unintelligent state by directly connecting 4 to 8.

Turning to the discharge state the same modules carry out slightly different functions. The battery provides three discharge points (in this example, although no limit is necessary) one which will be cut-off when the battery charge is reduced to 70% of full charge 10, one that is cut off when battery charge is reduced to 30% of full charge 11 and a third 8 that permits full discharge.

This arrangement permits non-essential electrics such as water heaters to be run when the battery is between 70% and 100% charged, important electrics such as lighting to be run down to 30% of battery charge but still retaining sufficient charge at all times to enable the battery to carry out its prime function of starting the engine. Hence the monitoring function of the Main Control Unit 40 decides whether switches 43 or 44 are made permitting discharge or broken preventing discharge. The link to terminal 8 is assumed to be always made for discharge down to 0% of battery-cells capacity. Warnings and acknowledgements are generated by and accepted on the display panel 13 described below.

Turning to Figure 10 additional features of the display panel 13 are amplified and explained. The four buttons 16A master override, 16B warning acknowledgement, 15A and 15B calibration buttons are shown. A conventional solid state LCD or LED type display 14 is utilised driven by the display drive 47. Signals to the display are multiplexed down the link 38 from the Main control unit 40. Audio warnings either as 'bleeps' or synthesised voice are passed to the audio output loudspeaker 46 through a display drive 47. The display can be programmed either to cycle automatically through all the output data described above or can be manually cycled using the acknowledge button 16B.

The Main Control Unit 40 is shown in block diagram form in Figure 11. Signals 20, 24 and 26 are received from the resonance tube 19, the pulse delay 23 and the temperature probe 27. These are converted by a sensor monitoring circuit 48 into density and temperature values 50 and 51. These values are combined with the instantaneous voltage value measured across lines 33 and 60 from the battery-cells terminals and the discharge/charge rate 61 from the monitor 45 in accordance with an optimising algorithm to establish the 'best guess' charge value from all sensor information. This information is further compared with the integrated change of charge since the last auto or manual calibration held in the control unit memory 53. The output from the combination of all this data and optimisation provides an accurate measure of charge status.The processor calculates the answers to two questions, namely what is present charge level and what to do about it? The processor 54 carries out the required calculations to establish these answers in accordance with pre programmed logic instructions. These instructions are varied depending on the particular battery-cells that comprise the charge reservoir for this battery. As described earlier too high charge or charging rate will cause correction signals to be sent to the charge regulating circuitry 41 and 42 via link 35. Similarly too low battery-cell total charge will cause switches 43, 44 or both to be opened to reduce discharge rate. In either case alarms and warnings will be sent to the display via link 38. A memory 53 records charge history as is significant to battery health including excursions below 5% of total charge, overcurrent discharge that did not last long enough to fracture link 28 and in the case of emergency the date and time from the clock 49 of emergency override button 16A being pushed. Having the state of charge data available to the main processor allows a large number of status indications to be made on the display 13. These include date and time, charge/discharge rate, time to 30%, 70% or 100% charge/discharge, battery temperature, etc. The memory enables a battery-cells history to be retained.

Claims

1. A battery comprising battery cell means, a positive or negative first battery terminal, second and third battery terminals both of opposite polarity to the polarity of the first battery terminal, and a charge control system mounted on the battery cell means and arranged to measure the charge level of the battery cell means and to connect the second battery terminal to the battery cell means only when the charge level is above a first predetermined charge level value and to connect the third battery terminal to the battery cell means only when the charge level is above a second predetermined charge level value larger than the first predetermined charge level value.

2. A battery according to claim 1, wherein the battery cell means are liquid-electrolyte type battery cell means.

3. A battery according to claim 1 or claim 2 further comprising a fourth battery terminal having the same polarity as the second and third battery terminals and wherein the charge control system is further arranged to connect the fourth battery terminal to the battery cell means only when the charge level is above a third predetermined charge level value larger than the second predetermined charge level value.

4. A battery according to any one of the preceding claims, wherein the charge control system is further arranged to regulate the charging current during charging of the battery cell means in accordance with the measured charge level to set the level of the charging current at the optimum value for the present value of the measured charge level.

5. A battery according to any one of the preceding claims, wherein the charge control system is detachably mounted on the battery cell means.

6. A battery according to claim 5, wherein the charge control system is detachably mounted on the top of the battery cell means.

7. A battery according to claim 5 or claim 6, wherein the battery cell means has a fifth battery terminal of the same polarity as the second and third battery terminals and to which the second and third battery terminals are connectable under the control of the charge control system, the second and third battery terminals are mounted on the charge control system and the ~ charge control system is arranged to cover the fifth battery terminal.

8. A battery according to claim 7 and claim 3, wherein the fourth battery terminal is connectable to the fifth battery terminal under the control of the charge control system and is mounted on the charge control system.

9. A battery according to claim 7 or claim 8, wherein the battery cell means has a sixth battery terminal of the same polarity as the first battery terminal and to which the first battery terminal is connected, the first battery terminal is mounted on the charge control system and the charge control system is arranged to cover the sixth battery terminal.

10. A battery according to claim 9, wherein the charge control system is detachably mounted on the battery cell means by gripping the fifth and sixth battery terminals.

11. A battery according to any one of claims 5 to 10, wherein the battery cell means has a recess and the charge control system is detachably mounted in the recess.

12. A battery according to any one of the preceding claims, wherein the charge control system further comprises display means for displaying the charge level of the battery cell means.

13. A battery according to claim 12, wherein the display means is further arranged to display selectively the charge rate, discharge rate, time and time to a predetermined charge level value.

14. A battery according to any one of the preceding claims, further comprising second display means remote from the charge control system for displaying data generated by the charge control system.

15. A battery according to any one of the preceding claims, wherein the charge control system includes an event memory for recording events relating to the charging and discharging of the battery cell means and the time of occurrence of those events.

16. A battery according to any one of the preceding claims, wherein the charge control system contains circuit breaker means responsive to a short circuit across the exposed battery terminals of opposite polarities.

17. A battery according to any one of the preceding claims, further comprising a specific gravity sensor located in the battery cell means and connected to the charge control system for use in measuring the charge level.

18. A battery according to claim 17, wherein the specific gravity sensor is of the tuneable frequency type.

19. A battery according to claim 17, wherein the specific gravity sensor is of the measured pulse delay type.

20. A battery according to any one of claims 17 to 19, further comprising a temperature sensor connected to the charge control system for improving the accuracy of calculations made in measuring the charge level.

21. A battery according to any one of the preceding claims, wherein the charge control system is arranged to produce an audio output in dependence on the measured charge level.

22. A battery substantially as hereinbefore described with reference to and as illustrated in any of the accompanying drawings.

23. Any and all novel features and combinations and subcombinations thereof substantially as disclosed herein.