Portable battery charger

#The present invention relates to a portable battery charging apparatus for recharging battery powered appliances, tools, toys or the like, without the need for an AC power source.

#A common problem with battery powered appliances., tools or toys that operate on rechargeable battery packs is that the battery pack tends to reach a discharged condition when the device is in use. If the battery is internal to the appliance, use of the appliance must be discontinued while the battery is recharged via a conventional AC/DC battery charger. In the case of a battery powered appliance such as a home video camera, a delay in operational time often results in the irreversible loss of opportunity. This problem has been addressed by the manufacturers of battery powered appliances, such as garden tools, in some instances, by supplying a removable battery pack (U.S. Pat. Nos. 3,757,194 and 4,084,123). In this way the discharged battery pack may be replaced with a fully charged battery pack enabling the device to be operated for an additional period of time.

#There are still several problems associated with the use of a secondary battery pack. The first problem relates to the significant expense associated with the purchase of the second battery pack. An additional problem is that the second battery pack is, in many instances, rarely utilized because it can only be used with the specific appliance for which it was purchased. It is for the lack of use that a second battery pack is rarely purchased. Another problem associated with a second rechargeable battery pack relates to the fact that, the second battery pack must have been thoroughly recharged within a suitable period of time, because of the tendency of rechargeable batteries to "self-discharge" during storage. For example, a fully recharged battery pack of a nickel-cadmium design, will lose approximately 1% of its nominal charge per day if stored at room temperature, ie 77 degrees Fahrenheit.

#FIG. 1 is a perspective view of the preferred embodiment of the invention as it is used to charge the battery of a battery powered appliance;

#FIG. 2 is a perspective view of the battery powered appliance and the associated rechargeable battery pack which has been adapted to accept the use of a portable battery charger;

#FIG. 3 is a cut-a-way view of the portable battery charger;

#Referring to FIGS. 1 and 2 of the drawings, there is shown a portable battery charger 10 in the form designated for attachment to an appliance such as a portable video camera 12. A plastic housing 13 is designed for attachment to the rear of the video camera 12 directly in contact with a rechargeable camera battery pack 14. Mounting brackets 15, 16 and 17 and 18 are designed for rapid attachment and detachment directly onto the rear of the camera battery pack 14. The lower brackets 15 and 16 are rigid and immobile. The upper brackets 17 and 18 are movable and are attached to a release mechanism 19 for removing the portable battery charger from the camera battery pack 14. The housing 13 is equipped with a sliding compartment cover 20 at the bottom through which primary batteries 21 are introduced. The primary batteries 21 are preferably alkaline cells, but can be of other chemistries such as standard carbon zinc or heavy duty carbon zinc as will be well known and understood by those skilled in the art.

#Internal to the portable battery charger 10 are electrical contacts and shunts through which the primary batteries 21 are connected in series as will be described in greater detail later.

#Electrical contact is made from the portable battery charger 10 to the rechargeable camera battery pack 14 via two external electrical contacts 23 and 24. These external electrical contacts 23 and 24 are preferably formed from nickel plated steel strip or tin plated brass alloy and are spring loaded to produce the proper contact force to exposed contact pads 30 and 31 of the rechargeable battery pack 14.