Popular Science Monthly 



469 



Reconstructing a Dry Battery 



CONSTRUCTING or reconstructing 

 a dry battery, if it is done care- 

 fully and with pure materials, will pre- 

 vent the unfortunate experience of the 

 amateur experimenter, who upon buy- 

 ing dry cells in an electrical store, finds 

 they are old and that a generous por- 

 tion of their strength has seeped out 

 while lying on the shelves. So far as 

 the cost of construction is concerned, a 

 home-made dry battery is about as ex- 

 pensive as a standard ready-made cell. 

 The only gain is in the life and con- 

 sistent ability of the battery. 



The foundation of the home-made dry 

 cell consists of the zinc cylinder, care- 

 fully cleaned, from a worn-out battery. 

 The cup should be boiled in clean water 

 for several minutes. When the inner 

 zinc surface is washed, it is lined with 

 three or four layers of white blotting 

 paper. This paper should be laid in firm- 

 ly and held with clips but not glued. Two 

 disks of blotting paper are placed in the 

 bottom of the cup. Care should be taken 

 that none of the inner surface of the 

 zinc is exposed to the chemicals that 

 are afterwards put in, or the life of the 

 cell will be considerably shortened. 



After blotting paper is in place, it 

 should be soaked for several minutes in 

 a solution of zinc chloride and sal am- 

 moniac in distilled water. To arrive at 

 the correct proportion of chemicals will 

 take a little time unless a hydrometer is 

 handy. The zinc chloride should be dis- 

 solved first. Crystals should be dis- 

 solved in the water until the hydrometer 

 reading is 32 degrees. If a hydrometer 

 is not available, a saturated solution of 

 zinc chloride should be made; that is to 

 say, a solution that has dissolved as 

 much of the chemical as it is able. 

 Add half again as much water as was 

 originally used. This brings the solution 

 to an approximate 32 degrees. 



Powdered sal ammoniac should now 

 be added until the solution is again sat- 

 urated, when it is read\- for soaking tlic 

 l)lotter lining of the zinc. The soaking 

 process should continue until the blotter 

 can absorb no more of the solution. 



Chemicals with which the battery is 

 filled consist of a thorough mixture of 

 two parts of manganese powder and 

 three parts of powdered carbon or 



graphite. Carbon is cheaper. Coke is 

 still cheaper, although it does not an- 

 swer the purpose quite so effectively. 

 Retort carbon, or arc carbon, pulverized 

 in an iron retort, can be used. The two 

 powders can be thoroughly mixed if they 

 are placed in a covered jar of some sort, 

 and the jar rolled 

 and shaken care- 

 fully. Pains 

 should be taken 

 in mixing the 

 powders, as a 

 generous propor- 

 tion of the bat- 

 tery's future per- 

 f o r m a n c e de- 

 pends upon this 

 operation. When 

 the manganese 

 and carbon pow- 

 ders are thor- 

 oughly inter- 

 mingled, they 

 are moistened 

 w i t h the zinc 

 chloride-sal am- 

 moniac solution. 



Section through an ordi- 

 nary dry cell 



Aloistening the powder does not mean 

 bringing it to a pasty state. It should 

 have a damp, lumpy appearance. 



Tamping the mixture into the zinc 

 shell is the next step, and it is the most 

 important part of the process. After the 



carbon rod is 

 placed in the 

 center, the pow- 

 der should be 

 dropped in, a 

 little at a time, 

 and tamped 

 down forcibly 

 w i t h a blunt 

 stick and a ham- 

 mer. It is a 

 painstaking pro- 

 cess, but the re- 

 sults are worth 

 the eft'ort. When the container is filled 

 within about one-half inch from the top, 

 the blotting paper layers are folded in- 

 ward and the rest of the space filled 

 with sealing wax or a mixture of par- 

 affin and resin. 



When the battery is finished, if the 

 directions are carefully followed, it 

 should give excellent results. 



Method of mixing ma- 

 terials in a mortar 



