GB2256741A

GB2256741A - Discharging means provided in power pack casing.

Info

Publication number: GB2256741A
Application number: GB9112587A
Authority: GB
Inventors: Gabriel Yui Lung Tong
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-06-11
Filing date: 1991-06-11
Publication date: 1992-12-16
Anticipated expiration: 2011-06-11
Also published as: GB2256741B; DE4141488A1; GB9112587D0

Description

2 ' 6---p' 1 1" -) 4 1 POWER PACK The present invention relates to a power

pack, and particularly but not exclusively to a battery pack incorporating nickel-cadmium battery cells.

Nickel-cadmium battery cells have a drawback which is generally known as memory effect. If a nickel-cadmium battery cell is recharged up too frequently from a condition other than fully discharged, the recharging capacity will be significantly reduced. It is therefore always recommended to discharge fully a nickel-cadmium battery cell before it is recharged.

According to the invention, there is provided a power pack which comprises a casing, one or more battery cells electrically connected together and contained in the casing, at least two terminals disposed on or extending out of the casing and electrically connected to the battery cell or cells, and discharging means contained within the casing and arranged to discharge the battery cell or cells.

Preferably, the discharging means comprises an electrical circuit having an energy-dissipating element.

It is preferred embodiment, the energy-dissipating element is heatproducing, and the casing has an internal partition separating the energydissipating element from the battery cell or cells so that the latter is or are thermally- insulated from the former.

In a preferred that the casing wall adjacent the energydissipating element has at least one aperture through which the interior of the casing communicates with the outside of the casing.

preferably, the electrical circuit includes a switch for controlling the operation of said discharging means.

Advantageously, the electrical circuit includes a light emitting indicator for indicating when said discharging means is in operation.

It is preferred that the part of the wall of the casing adjacent the energy-dissipating element is detachable.

In a preferred embodiment, the discharging means comprises a resistor.

Preferably, a thermostat is electrically connected in series between the battery cell or cells and one of the two terminals.

It is preferred that the electrical connection made among the components of the power pack and immediately adjacent the wall of the casing is provided by means of metallic strips so that the casing can be made as small as possible.

3 The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

1 Figure 1 is a sectional side view of an embodiment of a power pack according to the invention; Figure 2 is a partial sectional plan view of the power pack of Figure 1; and Figure 3 is a circuit diagram of the power pack of Figures 1 and 2.

Referring to Figures 1 and 2 of the drawings, there is shown a power pack 10 embodying the invention, which power pack 10 comprises a easing 11 and five nickel-cadmium battery cells 12 held therein in a staggered manner. The battery cells 12 are connected electrically in series together by metallic strips 13. Each metallic strip 13 is connected to a corresponding battery cell terminal by soldering.

The power pack 10 has a pair of terminals 14 for electrical connection to either a battery charger for recharging or an electrical appliance to supply power thereto. Each terminal 14 is provided by a metallic strip 15 having one end extending out of the casing 11. The other ends of the metallic strips 15 are connected to the corresponding terminal metallic strips 13 of the series of battery cells 12, one directly and the other one via a thermostat 21. The thermostat 21 is provided to disconnect the battery cells 12 from a faulty loading condition, such as shortcircuiting of the terminals 14.

Referring also to Figure 3, the power pack 10 is provided with a discharging circuit 16 for discharging the battery cells 12. The circuit 16 is f ormed by a resistor 17 connectable by an electrical switch 18 across the terminal metallic strips 13 of the series of battery cells 12. A light-emitting diode 19, together with an associated current-limiting resistor 20, is connected electrically in parallel with the resistor 17. The switch 18, the lightemitting diode 19 and the current-limiting resistor 20 are supported on a printed circuit board 22 which is located adjacent the top wall of the casing 11 and between the two top battery cells 12, as shown in Figure 1. The thermostat 21 is located in the same end of the casing 11 as the terminals 14.

The discharging resistor 17 is located in the other end of the casing 11, but within a compartment 23 therefor. The compartment 23 is formed by a Lshaped partition 24. The part of the wall of the casing 11 adjacent the resistor 17 is detachably snapped in place, thereby forming a lid 25 of the compartment 23. The resistor 17 is a wound resistor having a value of resistance less than ten ohms, and produces heat when the battery cells 12 are discharged through it. To this end, eight slots 26 are formed in the lid 25, through which slots 26 heat produced by the resistor 17 is dissipated out of the casing 11. The partition 24 serves to insulate thermally the battery cells 12 from the resistor 17.

All the electrical connection among various components of the power pack 10, namely the battery cells 12$ the terminals 14, the resistor 17 and the thermostat 21, which is made immediately adjacent the wall of the casing 11, is provided by metallic strips$ as shown in Figures 1 and 2. This arrangement permits the casing 11 to be made as small as possible.

In use, the switch 18 is closed to discharge the battery cells 12 through the resistor 179 irrespective of whether or not the power pack 10 remains attached to an electrical appliance. The lightemitting diode 19 serves to indicate when the discharging operation is taking place until it finishes when the battery cells 12 are fully discharged. At this time, the power pack 10 is ready to be recharged by means of a battery charger.

It is appreciated that apart from a resistorg any other suitable energydissipating elements could be used, such as a halogen light bulb which can also serve to provide an indication for the discharging operation. Also, the design of the power pack is suitable f or any other types of battery cell suffering the drawback of memory effect.

The invention has been described by way of example only, and various other modifications of and/or alterations to the described embodiment may be made by persons skilled in the art without departing from the scope of the invention as specified in the appended claims.

Claims

1. A power pack comprising a casing, one or more battery cells electrically connected together and contained in the casing, at least two terminals disposed on or extending out of the casing and electrically connected to the battery cell or cells, and discharging means contained within the casing and arranged to discharge the battery cell or cells.

2. A power pack as claimed in claim 1, wherein said discharging means comprises an electrical circuit having an energy-dissipating element.

3. A power pack as claimed in claim 2, wherein the energy-dissipating element is heat-producing, and the casing has an internal partition separating the energydissipating element from the battery cell or cells so that the latter is or are thermally-insulated from the former.

4. A power pack as claimed in claim 2 or claim 3, wherein the casing wall adjacent the energy-dissipating element has at least one aperture through which the interior of the casing communicates with the outside of the casing.

5. A power pack as claimed in any one of claims 2 to 4, wherein the electrical circuit includes a switch for controlling the operation of said discharging means.

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6. A power pack as claimed in any one of claims 2 to 5, wherein the electrical circuit includes a light-emitting indicator for indicating when said discharging means is in operation.

7. A power pack as claimed in any one of claims 2 to 6, wherein the part of the wall of the casing adjacent the energy-dissipating element is detachable.

8. A power pack as claimed in any one of the preceding claims, wherein said discharging means comprises a resistor.

9. A power pack as claimed in any one of the preceding claims, wherein a thermostat is electrically connected in series between the battery cell or cells and one of the two terminals.

10. A power as claimed in any one of the preceding claims, wherein the electrical connection made among the components of the power pack and immediately adjacent the wall of the casing is provided by means of metallic strips so that the casing can be made as small as possible.

11. A power pack substantially as hereinbefore described with reference to the accompanying drawings.