OLD DRY BATTERIES

Manawatu Times, Issue 6848, 1 March 1929, Page 9

OLD DRY BATTERIES

EMERGENCY RENOVATION. Some suggestion as to the renovation for emergency purposes of old dry batteries which have survived their normal period of usefulness are given by an Australian technical expert. The directions are simple and designed to interest the amateur temporarily deprived of his regular power supply. Miany amateurs who use low consumption types of valves collect in the course of a year a number of old dry cells which have once done duty in lighting the filaments of the valves. Although these cells have littlo value as a permanent source of power for a wireless set, they can often bo made to provide an emergency power supply in cases whore the battery in use fails unexpectedly. It will probably be found, if the old cells aro tested with a voltmeter or ammeter, that some have recuperated considerably during the period of rest they havo had since they wore removed from the receiver. In an emergency several cells can often be selected showing a degree of recuperation which will permit of their use until a new sot of cells can be obtained. Failing this, a good way to make old cells do emergency service is to connect them in series-parallel circuit. This arrangement of colls greatly reduces the load imposed on individual cells and permits an old battery to be used for a short period. If three cells are required to operate a receiver and nine old cells are available, the nine cells should be divided into three groups of three cells each. The cells in each group are then connected, so that all carbon or central terminals are connected together in the ordinary scries arrangement—that is, with the carbon terminals of ono group of three cells connected to the zinc terminal of the next and so on. ‘ The battery is then connected to the receiver in the ordinary way.

When an old battery is required to do duty for a longer period than a few hours, the best way of ensuring that it will be able to deliver the current required is to convert it into a wet battery. A jar, large enough in the mouth to take the cell should be obtained. The paper casing should be stripped from the cell, leaving exposed the zinc .container, which will probably be considerably corroded. Several large holes should then be made in this zinc casing. These holes can be made with a chisel or an old bit in a handbrace. The cell is then placed in the jar, and a strong solution made by dissolving sal ammoniac in water is poured into the jar so that it comes above the level of the holes made in the zinc casing of the cell. After the cell has been allowed to stand long enough for the sal ammoniac solution to penetrate the material surrounding the carbon rod, it will be found to be capable of delivering a fairly strong and steady current.

A simpler but less effective method of restoring old dry cells for additional temporary service is to obtain an old bit, and with it make a hole about an inch and a half deep in the pitch or wax sealing on the top of the cell. This hole should be filled with a sal ammoniac solution. When the solution has passed into the interior of the cell the hole in the top should be filled with soap, sealing-wax, paraffin wax, pitch, or some ot'heT substance, which will seal it and prevent evaporation.