GB2077525A

GB2077525A - Battery recharger and rechargeable flash lamp

Info

Publication number: GB2077525A
Application number: GB8018120A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-06-03
Filing date: 1980-06-03
Publication date: 1981-12-16
Also published as: AU7776881A

Abstract

A torch 10 has rechargeable batteries which can be connected across terminals 29, 30 of a battery recharger. The interconnection between the batteries and the bulb of the torch is formed, such that, insertion of terminal 30 into the torch disconnects the bulb from the batteries and preferably connects the bulb across the power source of the recharger. When the battery voltage exceeds a reference voltage, given by 49, the comparator, 50, opens switch T1 and charging ceases. Draining of the power source, 43, which may be a car battery, is prevented by timer circuit 51 opening switch T2 after a predetermined time. <IMAGE>

Description

SPECIFCAT'ON Battery rechargers and rechargeable apparatus This invention relates to battery rechargers and rechargeable apparatus.

According to the present invention there is pro vided a battery recharger comprising a circuit having an input and an output and switch means for dis I connecting the input from the output; means for connecting a battery to be charged across the out put; means for connecting the input to a D.C. source of electrical power and means for operating the switch means to complete the circuit whenever the voltage supplied by the battery is less than a predetermined level.

Means may be provided for disconnecting the input from the output after a predetermined period of time has elapsed. This means may be constituted by a switch, which opens whenever the charge on a capacitor, which is charged in response to the con nection of the battery across the output or an indication thereof, rises above a predetermined level.

The recharger may be arranged for recharging a battery located in a battery operated device, in which case the recharger may include means for isolating the active part of the device from the battery during charging. In this latter case the recharger is prefer ably provided with means for connecting the active part of the device across the recharger, and hence, in use, across the power source input so that the device can be operated during charging but independent thereof.

Preferably the recharger includes a housing for receiving a battery and/or a battery-operated device containing a battery. The means for connecting the battery across the output may comprise a pair of terminals projecting from the housing, and at least one of these terminals may be arranged to project into the device to connect with the battery inside the device. Such a terminal may constitute the discon necting means and may be formed with two mutual electrically isolated portions, one of which connects, in use, to the battery and the other of which con nects, in use, to the active part of the device. Preferably the insertion of the two part terminal isolates the battery from the active part ofthe device.

The housing may include a lid, which must be opened to allow insertion of a battery or device into the housing, in which case the lid may be arranged to operate one or more functions ofthe recharger e.g. the opening ofthe lid may cause the elapsed time capacitor to be discharged and the closing of the lid may initiate charging of the capacitor.

One or more ofthe switches in the circuit may be constituted by semi-conductor devices such as trans istors.

The means for opening the first mentioned switch may include means for providing a reference vol tage, and a differential amplifier used as a voltage comparator and connected such that, in use, the reference voltage is applied to its positive input and the battery voltage is connected to its negative input.

The circuit may include a filter circuit. The battery recharger may be mountable in a motor vehicle in which case the vehicle battery may constitute the D.C. power source.

According to another aspect of the invention there may be provided a rechargeable battery operated device including an active portion, a battery, means for connecting the active portion across the battery, said connecting means defining first and second contacts on either side of the battery, each of the contacts being engageable, in use, by respective output terminals of a battery recharger, at least one of said contacts being disposed within the device and accessible through an opening therein.

Said one contact may be constituted by a pair of electrically conductive elements, normally held in contact with each other. The elements may be electrically disconnectable from each other on or by .he insertion of a recharger output terminal. The effect of electrically disconnecting the metal elements is to isolate the battery from the active portion of the device.

Preferably the device is a torch, in which case the active portion is constituted by a bulb.

The invention further provides the combination of a torch as hereinbefore defined and a battery recharger as hereinbefore defined. If the battery recharger is mountable in a motor vehicle, the torch may constitute an interior light for the vehicle, when it is located in or on the recharger.

The invention may be performed in many ways, specific embodiments of which will now be described, with reference to and as illustrated in the accompanying drawings, in which: Figure 1 a is a vertical section through a torch; Figure 1 b is a vertical section through the base of a battery recharger; Figure 2a is a detailed enlarged view of a contact ofthetorch and a terminal of the battery recharger in a disengaged position; Figure 2b is a view of the contact and terminal of Figure 2a in an engaged position; Figure 3 is a perspective view of the battery recharger; and Figure 4 is a schematic diagram of the electrical circuit of the battery recharger and the torch.

Figure la shows a torch or flash-lamp generally indicated at 10, which has a body 11 comprising a generallyfrusto-conical bulb housing 12 and a hollow cylindrical battery housing extension 13. The open end of extension 13 is closed by a friction fitted metal base 14.

The base 14 is connected to one terminal of the bulb 15 through its mounting 16 by a copper strip 17 in a well known manner. The strip 17 is interrupted by a switch 18. The base 14 is also connected, by a copper spring 19, to the negative end of a pair of series connected rechargeable batteries 20, which are disposed axially in extension 13. The positive end of the battery assembly is connected to the other or central terminal 21 of bulb 15 via contact 22. Contact 22, the construction of which is best seen in Figure 2, comprises a pair of resilient metal elements 23 which extends generally parallel to each other into the extension 13 away from a slot 24 formed in extension 13.

The free ends of elements 23 are spaced by means of an electrically insulating block 25. As will be seen in Figure 2a each element 23 is formed midway along its length with an inwardly extending concave projection 26. The elements 23 are mounted such that the projections 26 are resiliently held in contact with each other forming an electrical path between the battery 20, which is urged against the left hand element by spring 19, and bulb 15 the central termi nal, 21, of which is held against the right hand element.

In normal use the torch 10 is switched on and off by switch 18.

Figure 1 b shows the base 27 of a battery charger generally indicated at 28. Two terminals 29 and 30 project upwardly from base 27 and, in use, are supplied with D.C. power via a printed circuit board 31 mounted within base 27.

Terminal 29 is in the form of a resilient electrically conducting clip, which engages base 14 of the torch.

Terminal 30 is formed as a rigid post 30a having a pointed free end 31, which is dimensioned to pass through slot 24 to contact elements 26.

It will be seen that when the torch 10 is mounted on base 27, as indicated by the dotted lines in Figure 1, batteries 20 are connected across terminals 29 and 30 and are therefore in position to be charged by power fed to those terminals.

Figures 2a and 2b show a more sophisticated arrangement wherein the rigid post 30a is divided, by means of an insulating axially extending sheet, into first and second terminals. The left hand section of the post serves as recharging terminal 30, whilst the right hand section forms a terminal 32, which can be connected, as described below, to a power source. With this arrangement the insertion of the post into slot 24 separates elements 23, thus isolating the batteries from the bulb. Further the bulb 15 is connected to terminal 32. The post 30a is provided with an insulating collar 30b for limiting insertion of the post 30a into slot 24.

Figure 3 shows the battery recharger 28 as a whole and it will be seen that it includes an electrically insulating housing 33 mounted on base 27 and a pair of horizontally extending side walls 34,35 and a lid 36 hinged on wall 34 to close the opening between the free ends of walls 34,35. Each wall 34,35 carries respective pairs of spaced electrically conducting strips 37,38. Lid 36 carries a cooperating electrically conducting strips 39,40 for each pair of strips 37.38, whereby strips 37 are interconnected when the lid 36 is open, as shown in Figure 3, and strips 38 are interconnected when the lid 36 is closed.

Figure 4 shows the circuit 41 of recharger 28 and torch 10. The circuit 41 can be divided into a main charging circuit, a protection circuit and a power supply circuit.

The main charging circuit essentially comprises input terminals 42, to which a battery or other D.C.

source 43, can be connected, output terminals 29 and 30, across which torch 10 is connected as hereinbefore described, a normally open transistor for switch 44, resistor 45, filter circuit 46, fuse 47 and charging control circuit 48.

The charging control circuit 48 comprises a reference voltage circuit 49, and on operational amplifier 50. The output of reference voltage circuit 49 is connected to the positive input of amplifier 50, whilst the negative input of the amplifier is connected to the positive end of batteries 20. The output of amplifier 50 is connected to the gate of transistor switch 44, which is arranged to switch-on whenever the output of amplifier 50 is positive i.e. when the voltage supplied by batteries 20 is less than the output voltage of reference circuit 49.

Thus when the batteries 20 are undercharged switch 44 is turned on and the batteries 20 are charged by battery 43. As soon as the voltage supplied by batteries 20 reaches the reference level the output of amplifier 50 becomes non-positive and switch 44 opens thus halting the charging operation.

The torch can therefore be left in the battery charger 28 until next required without the battery 43 becoming drained.

The filter circuit 46, removes any stray electrical energy peaks, whilst the fuse 47 protects against current surge.

The protector circuit generally indicated at 51 comprise a further transistor switch 52 disposed in the main charging circuit, an R.C. circuit 53 and a switch 54 which is arranged either two connect the capacitor 55 of circuit 53 across battery 43 or so that it can discharge through resistor R6 in accordance with the time constant of circuit 53.

The switch 54 is constituted by metal strips 37 to 40, which are connected such that when lid 36 is closed the capacitor 55 is connected across battery 43 and when lid 36 is open it is connected for discharge.

Thus each time the lid of housing 36 is opened to insert torch 10 in the housing 33 the capacitor 55 is discharged. When the lid 36 is closed after insertion oftorch 10 the capacitor 55 is connected to charge up and switch 52 is turned on. Whilst the charge of capacitor 55 is below a predetermined level it holds switch 52 on, thus allowing charging of the batteries 20 to take place. After a period of time, which is determine by values of resistor R5 and capacitor 55, has elapsed, the charge on the capacitor goes above the predetermined level and switch 52 opens.

The values of resistor R5 and R6 and capacitor 55 are chosen such that the capacitor 55 discharges extremely quickly, typically within 0.5 sec, and charges slowly, typically over a period of three or more hours. Thus it is fully discharged each time lid 36 is opened and the batteries 20 are fully charged before switch 52 opens.

The protection circuit 51 prevents battery 43 from being seriousoy drained if any fault occurs in the main circuit, for instance if a short circuit occurs between terminals 29 and 30.

Finally the power supply circuit comprises resistance 56, terminal 32, right-hand element 26, bulb 21, switch t S, base 14, terminal 29 and battery 43.

As previously explained when the torch 10 is placed on to the housing the insertion of the post 30a separates elements 26 isolating the bulb 15 from the battery 20 and connecting the bulb to terminal 32 and hence across battery 43. In Figure 4 this is represented by switch 57. Thus the torch 10 can be switched on when it is in the housing without drawing power from batteries 20.

This arrangement is particularly useful when the recharger is mounted in a motor vehicle, as it enables the torch to be used as an interior or engine light, whilst still mounted in the housing. If the recharger 28 is mounted in a vehicle the battery 43 may be constituted by the vehicle battery. It will be appreciated that the provision ofthe control and protection circuits ensure that the drain on the vehicle battery is kept to a minimum.

Preferably switches 44 and 52 are constituted by low resistance devices such as VMOS F.E.T.'s. It will further be appreciated that the rechargers of this type can be used with any other suitably constructed battery operated device when the values of the components of the voltage reference circuit are suitably adjusted. In some cases the protection circuit and the power supply circuit may not be required, in which case the post 30 may be formed as a single element.

The position of slot 24 in torch 10 is preferred but it will be seen that it can be formed anywhere within the body provided a connection can be made between an element or elements 26 adjacent to the slot 24 and the terminal of battery 20. The disposition of elements 26 within the housing reduces the possibility of a short circuit occurring between them.

Claims

1. A battery recharger comprising a circuit having an input and an output, switch means for disconnecting the input from the output, the input being arranged for connection across a D.C. source of electrical power and the output being arranged for connection to a battery to be charged, and operating means for switching the switch means to complete the circuit, whenever the voltage supplied by the battery is less than a predetermined value.

2. A battery recharger as claimed in claim 1, further comprising protection means for disconnecting the input from the output after a predetermined period of time has elapsed.

3. A battery recharger as claimed in claim 2, wherein the protection means includes a switch, which opens whenever the charge on a capacitor, which is charged in response to the connection of the battery across the output, or an indication thereof, rises above a predetermined level.

4. A battery recharger as claimed in any one of the preceding claims, wherein the recharger is arranged for recharging a battery in a batteryoperated device, and wherein the recharger further comprises means for isolating the active part of the device from the battery during charging.

5. A battery recharger as claimed in claim 4, further comprising connecting means for connecting the active part of the device across the recharger, and hence, in use, across the power source input so that the device can be operated during charging but independent thereof.

6. A battery recharger as claimed in any one of the preceding claims, including a housing for receiving a battery and/or a battery-operated device containing a battery.

7. A battery recharger as claimed in claim 4 or 5, including a housing for receiving the batteryoperated device and wherein the output comprises a pairofterminals projecting from the housing, at least one of these terminals being arranged to project into the device, in use, to connect with the battery inside the device.

8. A battery recharger as claimed in claim 7, wherein the one terminal forms at least part of the isolating means.

9. A battery recharger as claimed in claim 8, wherein the one terminal is formed with two mutually electrically isolated portions, one of which connects, in use, to the battery and the other of which connects, in use, to the active part of the device.

10. A battery recharger as claimed in any one of claims 6 to 9, wherein the housing includes a lid, which must be moved to allow insertion of a battery or device into the housing, the lid being arranged to operate one or more functions of the recharger.

11. A battery recharger as claimed in claim 10, when dependent on claim 3, wherein movement of the lid controls charging and discharging of the capacitor.

12. A battery recharger as claimed in any one of the preceding claims, wherein the operating means includes means for providing a reference voltage and a differential amplifier, used as a voltage comparator, connected such that, in use, the reference voltage is applied to its positive input and the battery voltage is connected to its negative input.

13. A battery recharger as claimed in any one of the preceding claims, wherein the circuit includes a filter circuit and/or a fuse.

14. A battery recharger as claimed in any one of the preceding claims, wherein the recharger is mountable in a motor vehicle and the inputs are connectable to the vehicle battery.

15. A battery-operated device including an active portion, a rechargeable battery and means for connecting the active portion across the battery, the connecting means defining first and second electrical contacts on respective electrical sides of the battery, each of the contacts being engageable by respective output terminals of a battery recharger, at least one of the contacts being disposed within the device and accessible through an opening therein.

16. A device as claimed in claim 15, wherein the one contact is constituted by a pair of normally engaged electrically conductive elements, which are disengageable, on or by the insertion of a recharger output terminal, to isolate the battery from the active portion of the device.

17. A device as claimed in claim 15 or claim 16, wherein the device is a torch and the active portion is a bulb.

18. The combination of a device as claimed in any one of claims 15 to 17 and a battery recharger as claimed in any one of claims 1 to 14.

19. Acomtination as claimed in claim 18, wherein the battery recharger is mountable in a motor vehicle and wherein the device is a torch, which constitutes an interior light for the vehicle, when it is located in or on the recharger.

20. A battery recharger substantially as hereinbefore described with reference to the accompanying drawings.

21. A battery-operated device substantially as hereinbefore described with reference to the accompanying drawings.