GB2391727A

GB2391727A - Solar-powered battery charging

Info

Publication number: GB2391727A
Application number: GB0306065A
Authority: GB
Inventors: Stephen Michael Kuester
Original assignee: Handley Kuester Ltd
Current assignee: Handley Kuester Ltd
Priority date: 2002-03-15
Filing date: 2003-03-17
Publication date: 2004-02-11
Anticipated expiration: 2023-03-17
Also published as: WO2003079513A2; GB0206168D0; AU2003214418A1; GB0306065D0; WO2003079513A3; GB2391727B

Abstract

A solar panel 4 of a battery charger supplies charging current alternately to two battery-charging stations 11 or 14 within the charger-casing 1, during a recurrent operating cycle in which one battery is charged while the open-circuit voltage of the other is monitored during successive periods of the cycle controlled by a microprocessor 25 of a circuit-panel 17. Charging current is supplied to the batteries via respective transistors 27,28, only one of which is ON at any time and is pulsed OFF and ON for regulating the average rate of charging if the output of the solar panel 4 exceeds an optimum magnitude, or for trickle charging the relevant battery if its monitored open-circuit voltage indicates it to be fully charged. Flashing LED indicators 20,21 show charge conditions and charge-rate of the respective batteries, and guides optimisation of orientation of the casing 1 for fastest charge. Charging stations 11 for two AA batteries are transverse to the stations 14 for two AAA batteries so only one battery-type can be charged at a time.

Description

f 239] 727 801ar-Powered Battery Charging 5 This invention relates to

battery charging and is particularly concerned with battery charging using solar power. According to one aspect of the present invention there is 10 provided a method of battery charging wherein a battery to be charged is supplied during a recurrent operating cycle with charging current derived from solar power, the cycle comprises successive monitoring and charging periods during which, respectively, the open- circuit 15 voltage of the battery is monitored and the charging current is supplied to charge the battery, and wherein the supply of charging current to the battery during the charging period is regulated in dependence upon the monitored open-circuit voltage.

According to another aspect of the invention there is provided a solarpowered battery charger comprising positive and negative connectors for establishing electrical connection to a battery to be charged, solar 25 panel means, and circuit means for supplying charging current derived from the solar-panel means to the battery during a recurrent operating cycle, wherein the cycle comprises successive monitoring and charging periods during which, respectively, the open-circuit voltage of 30 the battery is monitored and the charging current is supplied to charge the battery, and wherein the supply of charging current to the battery during the charging period is regulated in dependence upon the monitored open- circuit voltage.

The solar-power current may also be monitored, and in these circumstances the charging current supplied to the

battery during the charging period may be regulated if the monitored current exceeds a pre-set value, to limit power transfer to the battery. The charging current may be regulated in this respect, by pulsing the charging 5 current supplied to the battery ON and OFF. Pulsing ON and OFF of the current supplied to the battery may also be used for regulation of the charging current in dependence upon the open-circuit voltage.

10 The method and battery-charger of the invention may be used for charging a further battery at the same time as the first-mentioned battery, and in this respect the further battery to be charged may be supplied with charging current alternately with supply to the first 15 mentioned battery, the charging current being supplied to charge the further battery during the monitoring period of the first-mentioned battery. The open-circuit voltage of the further battery may be monitored during the charging period of the first-mentioned battery, and the 20 supply of charging current to the further battery during its charging period may be regulated in dependence upon its monitored open-circuit voltage.

A solar-powered battery-charger, and a method of solar 25 powered battery charging, in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the solar-powered 30 battery-charger in accordance with the invention, from the front and one side, with its stand deployed; Figures 2 and 3 are perspective views of the solar-

powered battery-charger of Figure 1 from the rear and the 35 other side, with its stand retracted, Figure 2 showing the charger with its batterycover lid closed and Figure 3 with the lid open;

Figures 4 and 5 are exploded perspective views of the solar-powered battery-charger of Figure 1, Figure 4 from the front and Figure S from the rear; and 5 Figure 6 is an electrical circuit diagram of the solar-

powered battery-charger of Figure 1.

The solar-powered battery-charger to be described is for use in charging one or two AA re-chargeable batteries or, 10 selectively, one or two AAA re-chargeable batteries; the batteries may be NiCd (nickel cadmium) or Nigh (nickel metal hydride), and other battery-configurations, for example, of the configuration known as "chewing gum", may be accommodated. The charging function is self-adaptive 15 to the solar energy received and the state of the re-

chargeable batteries entered to be charged, and utilizes the available energy efficiently.

Referring to Figures 1 to 5, the solar-powered battery 20 charger has a plastics casing 1 with a front escutcheon 2 and rear battery-cover lid 3. A solar panel 4 made up of four solar cells 5 is mounted within the front of the casing 1 under a bordering frame to be exposed to sunlight through the escutcheon 2. The inner rim 7 of 25 the frame 6 is metallised to reflect light onto the panel 4. The orientation of the casing 1 can be adjusted in elevation for optimum reception of solar energy, using a 30 stand 8 that is hinged to the lid 3 at the rear of the charger. The stand 8, which retracts flat onto the lid 3 as illustrated in Figure 2, can be deployed as illustrated in Figure from its retracted condition, to act as a stay setting the required tilt angle for the 35 panel 4.

( The lid 3 is hinged to the rear of the casing l and is openable by release of a spring-clip 9 to reveal a compartment lo within the casing 1 for receiving the re-

chargeable batteries to be charged. In this regard, and 5 as illustrated most clearly in Figure 3, a pair of recessed-locations 11 with positive and negative battery contacts 12 and 13 respectively, are defined within the compartment 10 to receive individual AA batteries side-

by-side with one another for charging. A second pair of 10 recessedlocations 14, which have positive and negative battery contacts 15 and 16 respectively, are also defined extending transversely of the locations 11, for receiving individual AAA batteries. The disposition of the locations 14 transversely of locations 11 ensures that 15 one or two batteries of only one type, AA or AAA, can be entered in the charger at any time for charging.

Charging of the one or two batteries entered into the locations 11 or 14 is carried out in accordance with 20 solar energy received by the panel 4, under control of electrical circuitry carried by a panel 17 (Figures 4 and 5) located behind the panel 14 within the casing 1. The circuitry on the panel 17 includes a socket 18 for power take-off that is accessible externally through an 25 aperture 19 of the casing 1, and two dual-colour LED indicators 20 and 21 that project into respective recessed apertures 22 of the casing 1. The LED indicators 20 and 21 are used principally to provide indication of charge conditions of the two batteries of 30 either type, AA or AAA, entered either in locations 11 or 14. In this regard, the indicator 20 is associated with one location 11 and one location 14, and the indicator 21 is associated with the other pair of locations 11 and 14.

These associations are indicated on the casing 1 by two 35 markings 23 each of which leads from the aperture 22 of the respective indicator 20 and 21 to bracket the relevant pair of locations 11 and 14.

Referring to Figure 6, the solar panel 4 has an output of up to 2 volts depending upon the solar energy received and the electrical loading of it. A DC-DC voltage converter 24 responds to an output of more than 0.8 volts 5 from the panel 4 to power a micro-controller 25 and the take-off socket 18. The converter 24 also supplies a voltage-low' signal to the controller 25 on a connection 26 in the circumstances in which the output of the panel 4 is insufficient, namely, less than a threshold of 1.3 10 volts, to charge a battery entered in either location 11 or either location 14. Charging proceeds under the control of the controller 25 only while the voltage output of the panel 4 is at or above this threshold.

15 The battery locations 11 and 14 associated with the LED indicator 20 are constituting charging station I, whereas those associated with the LED indicator 21 are identified as constituting charging station II. The positive contacts 12 and 15 of the two locations 11 and 14 of each 20 station I and II are connected together, as are the corresponding negative contacts 13 and 16, and the micro-

controller 25 regulates current supply to the two stations I and II via respective switching transistors 27 and 28. Only one of the transistors 27 and 28 is ON at 25 any time, so that batteries in stations I and II are connected to the solar panel 4 to receive charge in alternate cycles recurrently. The controller 25 monitors the battery voltage at stations I and II via respective connections 29 and 30, and also monitors the average 30 current supplied during each charging cycle, via a connection 31.

While a battery is charging at station I, the associated LED indicator 20 is driven by the controller 25 to flash 35 green, and similarly, for a battery is charging at station II the indicator 21 is correspondingly driven to flash green. The rate of flashing in both cases

signifies the rate of charging, and since this latter rate is in general dependent upon supply from the panel 4, the flashing can be used as a guide for optimizing the orientation of the charger in both azimuth and elevation, 5 for the fastest charge. When charging is complete, the relevant indicator 20 or 21 remains on constantly green; if the battery is faulty the indicator 20 or 21 will show red. 10 The supply of charging current to the batteries at stations I and II alternately with one another during recurrent cycles, allows the controller 25 to monitor progress of the charging process of each battery. More especially, during the cyclic period when the battery at 15 station I is being charged, the transistor 28 is held OFF allowing the controller 25 to monitor the condition of the battery at station II via the connection 30, and correspondingly, during the period when the battery at station II is being charged, the transistor 27 is held 20 OFF and the condition of the battery at station I is monitored by the controller 25 via the connection 29. If only one station I or II is occupied by a battery, this is sensed by the controller 25 to hold the transistor 27 or 28 individual to the other station, OFF while that 25 condition persists, isolating that station from the panel 4 throughout.

The cyclic charging period for each battery is 30 seconds, and the controller 25 monitors the charging 30 current throughout this period via the connection 31.

While the current supplied by the panel 4 remains less than an optimum value appropriate to maximum power transfer from the panel 4, the associated transistor 27 or 2B is held ON during the charging period, but if that 35 value is exceeded (because the sunlight is too strong), the transistor is pulsed ON and OFF so as to achieve an averaging out to the optimum. During the following,

monitoring period of 30 seconds while the other battery is being charged and the associated transistor 27 or 28 is held OFF to isolate the subject battery from the panel 4, the open-circuit voltage of the subject battery is 5 sampled via the relevant connection 29 or 30. The sampled voltage enables the controller 25 to determine whether the subject battery is fully-charged or faulty.

If the battery is fully charged, the controller 25 invokes a tricklecharging mode of operation in relation 10 to that battery during each subsequent charging period (until the battery is removed) while it continues to be detected as fully charged. During each such charging period, the associated transistor 27 or 28 is pulsed ON and OFF with a reduced duty cycle so as to establish a 15 low average current to maintain the charge without over-

charging the battery.

The controller 25 detects the presence of a faulty battery in station I or II, by virtue of the magnitude of 20 current flow monitored via the connection 31 during the charging periods for that respective station, and the open-circuit voltage, and its rate of change, monitored during the monitoring periods.

25 The solar-powered battery-charger described above is entirely automatic in operation. There is no ON/OFF switch and the readiness of the charger for operation is indicated by the LED indicators 20 and 21; in the circumstances in which no battery is currently entered in 30 the charger the indicators 20 and 21 flash green and then red alternately with one another cyclically. When a battery is inserted, the controller 25 checks the rise time of the battery voltage as the battery is charged during the first minute. If the rise is too fast from a 35 low level, the battery may have a weak cell, in which case the relevant indicator 20 or 21 is turned on after 30-60 seconds by the controller 25 to show red. The

controller 25 nonetheless continues to try to charge the battery until it is removed; removal causes the indicator to be reset.

Claims

Claims:

1. A method of battery charging wherein a battery to be charged is supplied during a recurrent operating cycle with charging current derived from solar power, the cycle comprises successive monitoring and charging periods during which, respectively, the open-circuit voltage of the battery is monitored and the charging current is supplied to charge the battery, and wherein the supply of charging current to the battery during the charging period is regulated in dependence upon the monitored opencircuit voltage.

2. A method according to Claim 1 wherein the charging current is regulated in dependence upon the monitored open-circuit voltage, by pulsing the current supplied to the battery ON and OFF during the charging period.

3. A method according to Claim 1 or Claim 2 wherein the current derived from solar power is monitored, and the charging current supplied to the battery during the charging period is regulated if the monitored current exceeds a pre-set value, to limit power transfer to the battery.

4. A method according to Claim 3 wherein the charging current is regulated if the monitored current exceeds the pre-set value, by pulsing the charging current supplied to the battery ON and OFF.

5. A method according to any one of Claims to 4 wherein the battery is detected as faulty according to the magnitude of current flow to the battery during the charging period, the monitored open-circuit voltage and the rate of change of the monitored open-circuit voltage.

6. A method according to any one of Claims 1 to 5 wherein a further battery to be charged is supplied with charging current alternately with supply to the first-

mentioned battery, the charging current being supplied to charge the further battery during the monitoring period of the first-mentioned battery, and wherein the open-

circuit voltage of the further battery is monitored during the charging period of the first-mentioned battery, and the supply of charging current to the further battery during its charging period is regulated in dependence upon its monitored open-circuit voltage.

7. A method according to Claim 6 wherein the charging current supplied to each battery is regulated in dependence upon the monitored open-circuit voltage of that battery, by pulsing the current supplied to it ON and OFF during its charging period.

8. A method according to Claim 6 or Claim 7 wherein the current derived from solar power is monitored, and the charging current supplied to each battery during its respective charging period is regulated if the monitored current exceeds a pre-set value, to limit power transfer to that battery.

9. A method according to Claim 8 wherein the charging current supplied to each battery is regulated if the monitored current exceeds the pre-set value, by pulsing the charging current supplied to that battery ON and OFF.

10. A method according to any one of Claims 6 to g wherein the circuit means detects whether either battery is faulty according to the magnitude of current flow to each battery during its respective charging period, its monitored open-circuit voltage and the rate of change of its monitored open-circuit voltage.

11. A solar-powered battery charger comprising positive and negative connectors for establishing electrical connection to a battery to be charged, solar-panel means, and circuit means for supplying charging current derived from the solar-panel means to the battery during a recurrent operating cycle, wherein the cycle comprises successive monitoring and charging periods during which, respectively, the opencircuit voltage of the battery is monitored and the charging current is supplied to charge the battery, and wherein the supply of charging current to the battery during the charging period is regulated in dependence upon the monitored open-circuit voltage.

12. A solar-powered battery charger according to Claim 11 wherein the charging current supplied to the battery is regulated in dependence upon the monitored open-

circuit voltage, by pulsing the current supplied to the battery ON and OFF during the charging period.

13. A solar-powered battery charger according to Claim 11 or Claim 12 wherein the current derived from the solar-panel means is monitored, and the charging current supplied to the battery during the charging period is regulated if the monitored current exceeds a pre-set value, to limit power transfer to the battery.

14. A solar-powered battery charger according to Claim 13 wherein the charging current is regulated if the monitored current exceeds the preset value, by pulsing the charging current supplied to the battery ON and OFF.

15. A solar-powered battery charger according to any one of Claims ll to 14 wherein the circuit means is operative to detect whether the battery is faulty according to the magnitude of current flow to the battery during the charging period, the monitored open-circuit voltage and the rate of change of the monitored open-circuit voltage.

16. A solar-powered battery charger according to any one of Claims 11 to 15 for charging batteries of either of two different elongate configurations, wherein the solar-

panel means and the circuit means are contained within a casing, and two elongate battery-holding locations are defined in the casing for receiving batteries of the two configurations respectively for charging, each of the locations having positive and negative connectors which are interconnected with the positive and negative connectors of the other location and which are connected to the circuit means for establishing a charging connection between the circuit means and any battery entered in the two locations, and wherein the two locations extend transversely to one another such that while a battery is entered in either of the locations entry of another battery in the other location is precluded.

17. A solar-powered battery charger according to any one of Claims 11 to 16 including positive and negative connectors for establishing electrical connection to a further battery to be charged, and wherein said circuit means is arranged to supply charging current derived from the solar-panel means to the further battery alternately with supply to the first- mentioned battery, the charging current being supplied to charge the further battery during the monitoring period of the first-mentioned battery, and wherein the open-circuit voltage of the further battery is monitored during the charging period of the first-mentioned battery, and the supply of charging current to the further battery during its charging period is regulated in dependence upon its monitored open-circuit voltage.

18. A solar-powered battery charger according to Claim 17 wherein the circuit means regulates the charging current supplied to each battery in dependence upon the

( monitored open-circuit voltage of that battery, by pulsing the current supplied to it ON and OFF during its charging period.

19. A solar-powered battery charger according to Claim 17 or Claim 18 wherein the circuit means monitors the current supplied by the solarpanel means and regulates the supply of charging current to each battery if the monitored current exceeds a pre-set value, to limit power transfer to each battery.

20. A solar-powered battery charger according to Claim 19 wherein the charging current supplied to each battery is regulated if the monitored current exceeds the pre-set value, by pulsing the charging current supplied to that battery ON and OFF.

21. A solar-powered battery charger according to any one of Claims 17 to 20 wherein the circuit means detects whether either battery is faulty according to the magnitude of current flow to each battery during its respective charging period, its monitored open-circuit voltage and the rate of change of its monitored open-

circuit voltage.

22. A solar-powered battery charger according to any one of Claims 11 to 21 wherein the solar-panel means comprises a solar panel mounted within a frame, and the frame has a reflective rim for reflecting light onto the panel.

23. A solar-powered battery charger substantially as hereinbefore described with reference to the accompanying drawings.

24. A method of solar-powered battery charging substantially as hereinbefore described with reference to the accompanying drawings.