AU687135B2

AU687135B2 - Rechargeable battery system and method

Info

Publication number: AU687135B2
Application number: AU11591/95A
Authority: AU
Inventors: Ken E Jarvis
Original assignee: SUNLIGHT SOLAR SYSTEMS AUSTRAL
Current assignee: SUNLIGHT SOLAR SYSTEMS AUSTRALIA Pty Ltd
Priority date: 1994-02-28
Filing date: 1995-02-07
Publication date: 1998-02-19
Anticipated expiration: 2015-02-07
Also published as: AU1159195A

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): SUNLIGHT SOLAR SYSTEMS AUSTRALIA PTY LTD A.C.N. 064 122 023 Invention Title: RECHARGEABLE BATTERY SYSTEM AND METHOD a s The following statement is a full description of this invention, including the best method of performing it known to me/us: -2 RECHARGEABLE BATTERY SYSTEM AND METHOD Field of the Invention This invention relates to a rechargeable battery system and method and relates particularly but not exclusively to such which uses a solar panel as the source of energy for charging the batteries and wherein the batteries are connected to lighting so that lighting can be provided at night time and charging of the rechargeable batteries effected during daytime.

Description of Prior Art Hitherto, rechargeable battery systems which utilise solar energy fo:r charging the rechargeable batteries work in a passive mode where the charging and the subsequent energy take-off after charging operate independently. In a charging mode, the systems operate in a manner to use the energy produced by the solar panel which is protective of the battery. In the energy take-off mode they operate on simple timing circuits or demand circuits that generally have some type of cut-out 20 protection based on battery voltage to ensure the battery is not overly discharged. These systems run the risk of over-discharging the rechargeable batteries of the system if the timing period has been set incorrectly. This is because the battery voltage protection is not 100% reliable 25 as an indicator of battery condition. Alternatively, such systems do not fully utilise the available energy which is the result of a common practice to set the timer for a period that uses the system conservatively. Due to the dangers of over-charging, the charging circuit cut-outs are often also set conservatively which can mean the batteries never fully charge. Thus, in applications where the rechargeable battery system is used for powerl'ig lighting which is operated by energy obtained from solar panels staflahy/keoelspecWPM4146 CAP 23 1 I_ I -3charging the rechargeable batteries, the systems are designed to work for a worst case solar energy expectation, such as may be experienced during winter timer. In summer time however, considerably more energy can be collected and the systems do not take advantage of this to provide lighting with either greater light output or for a longer duration, or both, during summer periods.

Oblject and Statement of Invention The present invention has been devised to provide a different rechargeable battery system.

Therefore, in accordance with a first broad aspect of the present invention there may be provided a rechargeable battery system having: e1e Rechargeable battery means; S. 15 2. Controller means; 3. Supply terminals for supplying energy for charging the rechargeable battery means; and 4. Output terminals for permitting energy to 20 be obtained from the rechargeable battery means, :said controller means interconnecting with said rechargeable battery means, said supply terminals and said output terminals to monitor energy supplied for charging 25 said rechargeable battery means, and to control the obtaining of energy from said rechargeable battery means based on the energy supplied for charging.

In one aspect, said controller preferably controls the time energy can be obtained from said rechargeable battery means.

Preferably, the supply terminals are connected with a solar panel to effect charging via solar energy.

It is also particularly preferred that the solar panel and the rechargeable battery means are collectively of a capacity to permit a given amount of energy to be obtained from the rechargeable battery means under a worst 7'k'" -4case solar energy expectation, whereby under such conditions a known energy can be obtained from the output terminals for a given time period, and should the solar erergy exceed that worst case expectation, greater energy can be obtained from said output terminals than for the worst case expectation.

In another aspect said controller means preferably controls the energy provided at the output terminals such that one energy level can be provided for Sone period of time and another level of energy for another period of time.

It is particularly preferred that the output terminals be connected with lighting to provide lighting at ooow S" night time from the solar energy stored in the battery imeans during daytime.

S: According to a further aspect of the present invention there may be provided a method of controlling the energy obtainable from a rechargeable battery system having a rechargeable battery means, controller means, supply Sterminals for supplying energy for charging said rechargeable battery means, and output terminals for permitting energy to be obtained from said rechargeable battery means, said controller means interconnecting with oe oo S" said rechargeable battery means, said supply terminals and Je said output terminals, said method involving monitoring said energy supplied for charging said rechargeable battery means and controlling the energy obtained from said output terminals based on the energy supplied for charging.

Preferably, the method in one aspect involves controlling the time energy is obtained from said rechargeable battery means.

Preferably, the charging energy is provided via a solar energy panel.

Preferably, in another aspect, the controller means controls the energy provided at the output terminals 5 such that one energy level is provided for one period of time, and another energy level for another period of time.

Preferably, the method also involves arranging for the solar energy panel and the rechargeable battery means to have a capacity to permit a given amount of energy to be obtained from the rechargeable battery means for a worst case expectation, and allowing a known amount of energy to be obtained from the output terminals for a given time period, and if the energy supplied to the rechargeable battery means exceeds that worst case expectation, allowing greater energy to be obtained from said output terminals than for the worst case expectation.

It is particularly preferred that the method be used for lighting, and permitting light to be provided at night time from lighting from the solar energy stored in the battery means during day time.

In accordance with a further aspect of the present invention there may be provided a rechargeable battery system having: 1. Rechargeable battery means; 2. Controller means; 3. Supply terminals for supplying energy for recharging said rechargeable battery means; and 4. Output terminals for permitting energy to be obtained from said rechargeable battery means, said controller means interconnecting with said rechargeable battery means, said supply terminals and said 30 output terminals to monitor energy obtained from said rechargeable battery means and to control the charging based on the energy obtained therefrom to ensure charging without over charging.

In accordance with a further aspect of the present invention, there may be provided any one of the inventions previously recited and monitor/comparator means staf~ahy/keoospcWPM4146 CAP 23 1 -6oo*o**

A.

A

o

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eeeee: A oe*oo*

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Ao *c connected with the rechargeable battery means, to measure battery terminal voltage at at least one known battery state and to compare the actual measured voltage against expected battery voltage for said at least one known battery state and to provide an output consequent on a nonfavourable comparison.

Most preferably the rechargeable battery means comprises a plurality of rechargeable battery means and wherein the monitor/comparator measures and compares each battery terminal voltage against at least one known battery state expected voltage, and the output is used to disconnect a battery that does not compare favourably with the known battery state.

In accordance with a further aspect of the 15 present invention there may be provided a method of controlling charging of a rechargeable battery means in a rechargeable battery system having a rechargeable battery means, controller means, supply terminals for supplying energy for charging said rechargeable battery means, and 20 output terminals for permitting energy to be obtained from said rechargeable battery means, said controller means interconnecting with said rechargeable battery means, said supply terminals and said output terminals, said method involving monitoring energy obtained from said rechargeable battery means and controlling the charging based on the energy obtained therefrom thereby ensuring charging without overcharging.

Brief Description of Drawings In order that the invention can be more clearly ascertained, examples of a preferred embodiment for use in a solar powered lighting system will now be described with reference to the accompar.\ ".ng drawings wherein: Figure 1 is a .l .c schematic diagram of one particular system; Figure 2 is a detailed circuit diagram of a controller means; and Figures 3, 4 and 5 are flow diagrams of the 1 t c 'V K 7 programming in the central processor unit in the controller means.

Detailed Description of Preferred Embodiment Referring firstly to Figure 1 to the block schematic diagram there is provided a controller which is a circuit w-,-zh operates as a controller means for controlling charging and subsequent discharging (extraction of energy from the rechargeable batteries). It can be seen that the controller 1 is connected with a solar panel 3.

The controller 1 is also connected with a rechargeable battery 5 which may comprise a number of batteries connected in parallel. The controller 1 is also connected with a load which can draw energy from the rechargeable battery 5. In this case, the load is three lamps L 1

L

2 L3. These lamps are selectively operated by means of a lamp switch 7. Thus, the lamp switch 7 is controlled from a controller 1 to supply energy to the lamps L 1

L

2

L

3 from the rechargeable battery 5. The system has supply terminals (not shown) for permitting connection with the solar panel 3 to enable energy from the solar panel 3 to be supplied for charging the rechargeable battery means. The system also has output terminals (not shown) for permitting energy to be obtained from the rechargeable battery means so that the lamps L 2

L

3 can be made to operate.

Conveniently, the supply terminals can be at a location shown generally by numeral 9. The output terminals can conveniently be at a location shown by numeral 11. The controller 1 is connected with a temperature measuring circuit 13, a discharge measuring circuit 15, a charge 30 measuring circuit 17 and a charge circuit 19. The controller 1 utilises a microprocessor which is programmed to enable the system to operate broadly as follows. During day time the controller permits the solar panel 3 to supply energy to the rechargeable battery 5 for recharging the rechargeable battery 5. The controller 1 measures the amount of energy being fed to the battery and records the 3iaItaiy!ee/specVPM4146 CAP 23 1 8 total amount of energy charge the battery receives during the daylight charging period. This is recorded using EPROM technology. The recording can be each day, or over a series of successive days. This can be predetermined in the software.

As the voltage of the solar panel 3 falls as night approaches, the controller 1 initiates activation of the lamps L 1

L

2

L

3 This occurs when the voltage of the solar panel 3 falls below a pre-set limit. At this time, the controller 1 examines the available power in the system having regard to the values recorded during the charging process. The controller 1 makes a decision based on the available power as to whether there is sufficient power to meet a preset minimum period of illumination whilst energising all of lamps L 1

L

2

L

3 For example, a system which uses three lamps will, based on the available amp hours of the battery 5 and the amp hours required to run the lamps for a pre-set minimum time, decide to switch on one, two or all three lamps. During operation of the lamps, the system monitors the amount of power used and continuously calculates the available power remaining in the battery 5. By monitoring this power, the controller 1 can at any stage (based on pre-set limits) decide to selectively switch off lamps as may be required to ensure the system meets its minimum timing specification. This feature is particularly suitable where at certain time periods higher light output is required in a given area than at other time periods. For example, when persons are leaving a building in winter time, it may be desirable to have greater illumination at that time than at early hours in the morning when only security lighting is required.

The system can be programmed to provide the greater light output at any given period and this need not be at an initial period of operation of the lamps.

The charging is controlled by the controller 1 having regard to ambient temperature sensed by the staftahy/keep/ePM446 CAP 23 1 I- 9 temperature measuring circuit 13 and will control the charge circuit 19 to stop charging of the battery 5 when the battery 5 it at its capacity. Typically, the battery terminal voltage can be monitored by the controller 1 and when this reaches a particular level it can be determined that the battery is fully cr'. During the charging process the energy supplie. i. itored by the charge measuring circuit 17 and infoi-. on relating thereto stored in the controller 1. Similarly, during operation of the lamps L, L2, 13, the energy taken from the battery is monitored by the discharge measuring circuit 15 and the information relating thereto stored in the controller 1.

Thus, the controller 1 is interconnected with the rechargeable battery 5, the supply terminals at location 9, and the output terminals at location 11 to monitor energy supplied for charging the battery 5 and to control the obtaining of energy from the battery 5 based on the energy supplied for charging. The controller 1 can operate in several modes as will be described hereinafter to control 20 the obtaining of energy f-om the battery 5 by the load, such as lamps L, L2, 113. In one aspect this can be by controlling the time the energy is taken from the battery and in another aspect it can be such that one level of energy can be provided for one period of time and another 25 level of energy for a different period of time. The controller 1 also operates to control the charging based on the energy obtained from the rechargeable battery means during discharging and to control the charging based on the energy obtained from the solar panel 3 to ensure maximum charging without overcharging.

The system has three user selectable modes of operation: 1. Standard Mode. In this mode operation is for a fixed period of time set by the user.

2. Automatic Mode. In this mode it operates for a fixed minimum period of time as well as a siaoahyflWoplspocilPM4146 CAP 23 1 10 supplementary period of time. The supplementary period of time is determined by the amount of power received during the charging period. This may be a single or multiple charging period preceding a particular night mode of operation, i.e. over several prior days. The supplementary time is calculated based on the amount of excess power available in such a way as to ensure efficient maximum use of the light from lamps L 1

L

2

L

3 whilst maintaining good protection of the battery 5 and leaving sufficient excess power to enable battery recharging where the battery charged state is low having regard to the next day's solar energy collection for a worst-case expectation.

3. Mode 2. The controller 1 can also operate in a mode similar to mode 2 above but it can also operate at a higher level of light output for a predetermined time and operate at a lower level of light output for the remaining period of time. Thus, one energy level can be pprovided for one period of time and a different energy level provided for a different period of time. This mode 20 can be used in combination with the automatic mode above or :in the standard mode above.

:Referring now to Figure 2 there i& shown a detailed circuit diagram of the system. Here, supply terminals 21 are shown whereby energy can be supplied from 25 a solar panel 3. Output terminals 23 are shown where the load such as the lamps L 1

L

2

L

3 are connected with a battery connected to terminals The circuit operates as follows. The microcontroller forming the CPU of the controller circuit 1 type 87C552 monitors the voltage of the solar panel 3 and when the voltage increases above the battery voltage then the controller 1 provides a signal to the charging circuit 19 (transistor T4 MOSFET power driver) and charging commences.

The controller 1 then continuously monitors both the solar panel voltage and the battery voltage and when the battery voltage reaches its boost maximum voltage (dependent on sIaIvahy/kolspocPM4146 CAP 23 1 11 battery type) it turns off the charging circuit 19 (T4).

It will then turn the charging circuit 19 back on when the battery voltage drops below a pre-set figure. The controller is then in a float charge mode and will cycle the charging circuit on at 13 volts and off at 14.1 volts.

These voltages are set for 20 0 C and there is a temperature compensation circuit comprising the temperature measuring circuit 13 which shifts these voltages according to a preprogrammed arrangement according to the battery temperature...

The energy being supplied to the battery 5 is monitored by measuring the current flowing through shuntresistor Rc, and then applying a time constant to give amps per hour. The internal program then adds this charge energy amount to the battery's existing capacity thas keeping an accsrate recorded measurement of the battery's actual capacity. The controller 1 is programmed to have the ability to re-direct excess power from the solar panel 3 to any external de"rice when the batteries 5 are fully 20 charged. This has not been shown in the circuits.

During night time the controller 1 monitors the solar panel 3 voltage and when this voltage drops below 2 volts it then turns on the lamps through transistors TI, T2, T3 for lamps L 1 L2, L 3 respectively. The lamps will 25 be illuminated according to the decisions implemented by the micro-controller as explained above.

With the lights operating, th controller 1 measures the amount of energy taken from the battery 5 via shunt resistor and it i referenced to a time constant giving amp/hour.

At the time when the lamps are activated, a timer in controller 1 is actuated and beings a count-down preset by the user. This timer has the capability of switching off one or more of the lamps L 1

L

2

L

3 at any time during the above operation to have a high intensity light output period and a lower light output intensity period as may be 9tallfahyfkoeocspPM44G CAP 23 1 12 determined by the power available.

The controller 1 will have set in it a minimum lamp operating period which will be extended each night of operation by analysing the amount of charge the battery receives during, for example, a preceding three day period and then calculating the optimum extra time and capacity available.

A typical operating condition for the lamps Li,

L

2

L

3 is as follows:

L

i battery voltage must be above pre-set level 1 and the actual capacity is above

L

2 battery voltage must be above pre-set level 2 and the actual capacity is above 45%; and

L

3 battery voltage must be above pre-set level 3 and the actual capacity is above If the battery reaches a pre-set lower limit of its capacity then the controller 1 will shut the lamps down and will not operate the lamps again until the battery has been recharged.

20 The c-ntroller 1 has the ability to monitor light levels of L 1

L

2 or L 3 and can vary the light intensity of

L

2 and L3 depending on battery condition and amount of charge received by the battery in a preceding period.

In the charging mode the solar panel voltage is 25 attenuated by Rl, R2 network and then interfaced to the controller 1 by IC 1 on A/D input 1.

The battery 5 voltage is attenuated by R3, R4 network and then interfaced to controller 1 by IC 2 on A/D input 2.

The charging current is measured by reading the voltage across the shunt resistor RCH, ground referenced by IC3, amplified by IC4 and then inputed to controller 1 on A/D input 3.

Temperature compensation is provided by way of the temperature sensor and R5. The output is fed to the controller 1 on A/D input 4.

safVahy!oespecVPM4 WCAP 23 195 13 The output P01 of the controller 1 turns on a MOSFET power driver which in turn switches on transistor T4 (type IRF540).

During the taking of power from the battery 5 the discharge current is measured by reading the voltage across shunt resistor RcH, ground referenced by IC5 and amplified by IC6 and then fed as an input to the controller on A/D input The lamp operation is as follows. The output P02 of the controller 1 supplies logic level output to drive transistor T1 to an on condition.

Output P03 of the controller 1 supplies logic level output to drive transistor Ti to an on condition.

Output P04 of the controller 1 supplied logic level output to drive transistor T3 on. Each of the transistors Tl, T2, T3 are type IRF540.

Outputs P05 through 8 can be used to provide digital output signals to drive external transistors or relays (not shown).

20 The diode D1 is a Schottky diode type PBYR1645 and this prevents discharge of the battery through the solar panel.

The software flow diagrams forming Figure 3 are self-explanatory. A suitable programmer can implement the 25 necessary programming functions to the microprocessor of the controller 1 to implement these functions.

Modifications may be made to the invention as would be apparent to persons skilled in the battery solar lighting arts. For example, instead of stepping the lamps

L

1

L

2

L

3 in accordance with the available energy, the lamps LI, L 2

L

3 may be continuously operated but the lamp switch 7 may comprise a control circuit which controls the light output and thus the energy consumed. In this way, a continuously variable light output may be achieved without the steps cleated by switching on or off lamps L 2 L3.

Instead of using lighting as the lead, other stafthyIoWJsec'PtA4146 CAP 23 1 _I II g IIPIIB~ls~-- 14 loads can be used.

These and other modifications may be made without departing from the ambit of the invention, the nature of which is to be determined from the foregoing description.

stafahyi/optspestPM4148 CAP 23 1,95

-I-

Claims

1. Rechargeable battery means;

2. Controller means;

3. Supply terminals for supplying energy for charging the rechargeable battery means; and

4. Output terminals for permitting energy to be obtained from the rechargeable battery means, said controller means interconnecting with said rechargeable battery means, said supply terminals and said S"output terminals to monitor energy supplied for charging 15 said rechargeable battery means, and to control the i obtaining of energy from said rechargeable battery means based on the energy supplied for charging. 2. The system as claimed in claim 1 wherein said controller means controls the time during which energy can 20 be obtained from said rechargeable battery means. 3. The system as claimed in claim 1 or claim 2 wherein said supply terminals are connected with a solar Spanel to effect charging via solar energy. S" 4. The system as claimed in claim 3 wherein said •eo 25 solar panel and said rechargeable battery means are collectively of a capacity to permit a given amount of energy to be obtained from said rechargeable battery means under a worst case solar energy expectation, whereby under such conditions a known energy can be obtained from said 2 output terminals for a given time period, and should the solar energy exceed that worst case expectation, greater energy can be obtained from said output terminals than for the worst case expectation.

The system as claimed in any one of the preceding claims wherein said controller means preferably controls the energy provided at said output terminals such that one i 1-91-1 iml-l' 'M 1, i I* -16- energy level can be provided for one period of time and another level of energy for another period of time.

6. The system as claimed in any one of the preceding claims wherein said output terminals are connected with lighting to provide lighting at night time from the solar energy stored in said rechargeable battery means during daytime.

7. The system as claimed in any one of the preceding claims further including monitor/comparator means, connected with said rechargeable battery means, to measure battery terminal voltage at at least one known battery state and to compare the actual measured voltage against expected battery voltage for said at least one known battery state and to provide an output signal consequent on 15 a non-favourable comparison.

8. The system of claim 7 wherein said rechargeable battery means comprises a plurality of battery means and wherein said monitor/comparator means measures and compares each battery terminal voltage against at least one known battery state expected voltage, and said output signal is used to disconnect a battery that does.not compare favourably with said known battery state.

9. The system as claimed in any one the preceding claims further including means to monitor the energy 25 obtained from said rechargeable battery means to control the charging based on the energy obtained therefrom to ensure charging without overcharging.

A method of controlling the energy obtainable from a rechargeable battery system having a rechargeable 3 battery means, controller means, supply terminals for supplying energy for charging said rechargeable battery means, and output terminals for permitting energy to be obtained from said rechargeable battery means, said controller means interconnecting with said rechargeable battery means, said supply terminals and said output terminals, h 41:4 'A 2 1 Il~ ~ermasm~-- l- I-*l -17- said method involving monitoring said energy supplied for charging said rechargeable battery means and controlling the energy obtained from said output terminals based on the energy supplied for charging.

11. The method of claim 10 including controlling the time during which energy is obtained from said rechargeable battery means.

12. The method of claim 10 or claim 11 comprising providing the energy for charging via a solar energy panel. Lj

13. The method of any one of claims 10 to 12 further including operating said controller means to 6ontrol the energy provided at said output terminals such that one energy level is provided for one period of time, and another energy level for another period of time. 15

14. The method as claimed in any one of claims 12 or S: 13 including arranging said solar energy panel and said rechargeable battery means to have a capacity to permit a given amount of energy to be obtained from said rechargeable battery means for a worst case expectation, 20 and allowing a known amount of energy to be obtained from said output terminals for a given time period, and if the t* energy supplied to said rechargeable battery means exceeds that worst case expectation, allowing greater energy to be obtained from said output terminals than for the worst case 2 expectation.

15. The method as claimed in any one of claims 12 to 14 further including using a system for lighting, and permitting light to be provided at night time from lighting from the solar energy stored in said rechargeable battery means during day time.

16. The method as claimed in any one of claims 10 to further including monitoring said rechargeable battery means to measure battery terminal voltage at at least one known battery state and comparing the act,\l measured 3 2 voltage against known expected voltage for said at least one known battery state and providing an output signal 1t t, C M11'1" 1. 1 -18- consequent on a non-favourable comparison.

17. The method of claim 16 wherein said rechargeable battery means comprises a plurality of rechargeable battery means and wherein said monitoring and said comparison are in respect of each battery terminal voltage and wherein said output signal is used to disconnect a battery that does not compare favourably against known expected voltage for said at least one known battery.

18. The method of any one of claims 10 to 17 further including monitoring the energy obtained from said rechargeable battery means to control the charging based on the energy obtained therefrom to ensure charging without overcharging.

•19. A rechargeable battery system having: 15 1. Rechargeable battery means; 2. Controller means; oo0 3. Supply terminals for supplying energy for recharging said e -;.lrgeable battery means; and 20 4. Output terminals for permitting energy to be obtained from said rechargeable battery means, said controller means interconnecting with said S" rechargeable battery means, said supply terminals and said .2 5 output terminals to monitor energy obtained from said rechargeable battery means and to control the charging based on the energy obtained therefrom to ensure charging without overcharging.

The system as claimed in claim 19 wherein said controller controls the time during which energy can be obtained from said rechargeable battery means.

21. The system as claimed in claim 19 or claim wherein said supply terminals are connected with a solar panel to effect charging via solar energy.

22. The system as claimed in claim 21 wherein said solar panel and said rechargeable battery means are t I ,k4 11 a I -19- collectively of a capacity to permit a given amount of energy to be obtained from said rechargeable battery means under a worst case solar energy expectation, whereby under such conditions a known energy can be obtained from said output terminals for a given time period, and should the solar energy exceed that worst case expectation, greater energy can be obtained from said output terminals than for the worst case expectation.

23. The system as claimed in any one of claims 19 to 22 wherein said controller preferably controls the energy provided at said output terminals such that one energy level can be provided for one period of time and another level of energy for another period of time.

24. The system as claimed in any one of claims 19 to e..o. 23 wherein said output terminals are connected with lighting to provide lighting at night time from the solar energy stored in said rechargeable battery means during o oo daytime.

The system as claimed in any one of claims 19 to 24 further including monitor/comparator means, connected with said rechargeable battery means, to measure battery terminal voltage at at least one known battery state and to compare the actual measured voltage against expected battery voltage for said at least one known battery state and to provide an output signal consequent on a non- favourable comparison.

26. The system as claimed in claim 25 wherein said rechargeable battery means comprises a plurality of battery means and wherein said monitor/comparator means measures S and compares each battery terminal voltage against at least one known battery state expected voltage, and said output signal is used to disconnect a battery that does not compare favourably with said at least one known battery state.

27. A method of controlling charging of a rechargeable battery means in a rechargeable battery system it A1 -1 9 f44 1 I having a rechargeable battery means, controller means, supply terminals for supplying energy for charging said rechargeable battery means, and output terminals for permitting energy to be obtained from said rechargeable battery means, said controller means interconnecting with said rechargeable battery means, said supply terminals and said output terminals, said method involving monitoring energy obtained from said rechargeable battery means and controlling the charging based on the energy obtained therefrom thereby ensuring charging without overcharging.

28. The method of claim 27 including controlling the time during which energy is obtained from said rechargeable battery means.

29. The method of claim 27 or claim 28 comprising 5 providing the energy for charging via a solar energy panel.

30. The method of any one of claims 27 to 29 further including operating said controller means to control the energy provided at said output terminals such that one energy level is provided for one period of time, and 2) another energy level for another period of time.

31. The method of any one of claims 29 or including arranging said solar energy panel and said rechargeable battery means to have a capacity to permit a given amount of energy to be obtained from said 2 rechargeable battery means for a worst case expectation, "i and allowing a known amount of energy to be obtained from said output terminals for a given time period, and if the energy supplied to said rechargeable battery means exceeds that worst case expectation, allowing greater energy to be obtained from said output terminals than for the worst case expecation.

32. The method of any one of claims 27 to 31 further including using the system for lighting, and permitting light to be provided at night time from lighting from the solar energy stored in said rechargeable battery means during day time. -21-

33. The method of any one of claims 27 to 32 further including monitoring sai4 rechargeable battery means to measure battery terminal voltage at at least one known battery state and comparing the actual measured voltage against known expected voltage for said at least one known battery state and providing an output signal consequent on a non-favourable comparison.

34. The method of claim 33 wherein said rechargeable battery means comprises a plurality of rechargeable battery means and wherein said monitoring and said comparison are in respect of each battery terminal voltage and wherein said output signal is used to disconnect a battery that does not compare favourably against known expected voltage for said at least one known battery state. 15

35. A system as claimed in any one of claims 1 to 9, or 19 to 26 substantially as herein described with reference to any one of the examples shown in the accompanying drawings.

36. A method as claimed in any one of claims 10 to 17, or 27 to 34 substantially as herein described with reference to any one of the examples shown in the accompanying drawings. DATED THIS 21ST DAY OF NOVEMBER 1997 25 SUNLIGHT SOLAR SYSTEMS AUSTRALIA PTY LTD By Its Patent Attorneys: GRIFFITH HACK Fellows Institute of Patent Attorneys of Australia melt-0imn, n K-~Ir N4 14, !AP 2' 1. 1 ABSTRACT A rechargeable battery system and method is disclosed which has: 1. Rechargeable battery means 2. Controller means 3. Supply terminals for supplying energy for charging the rechargeable battery means and 4. Output terminals (11) for permitting energy to be obtained from the rechargeable battery means The controller means is interconnected with the rechargeable battery means the supply terminals and said output terminals (11) to monitor energy supplied for charging said rechargeable battery means This is then used, in one embodiment, to control the obtaining of energy from the rechargeable battery means based on the energy supplied for charging. In another embodiment it is used to monitor energy obtained from the 20 rechargeable battery means to control the charging S..based on energy obtained therefrom to ensure charging without overcharging. S staffahyl/ekpspecPM414G CAP 23 1