Solving "A" Battery Problems

Radio Record, Volume IV, Issue 17, 7 November 1930, Page 16

Solving "A" Battery Problems

— Use of Daniel Cells

ATTERY problems, especially those of the "A," loom largely in the troubles of set Owners who are far removed from electric power. Dry cells generally prove an expensive item, for they ave constantly running down. Accumulators haye sometimes to be taken long distances over rough roads. often impassable in winter, to be charged. They are not infrequently damaged, when not only inconvenience but expense is involved. Some time ago, in an article by "Hardup" the Daniel cell type of primary battery, which figured largely in the early days of electricity, was mentioned as being a good charger for "A" accumulators. This aroused a considerable amount of interest and Jetters came from all parts of New Zealand. Further details were given on different occasions in Questions and Answers and just recently the writer happened to mention in the "Exporter" that particulars of this battery would be supplied on request. The amount of correspondence resulting from that remark was amazing, and there was apparently only one thing. to do, and that was to go into the whole question fully and prepare a special article. ‘The details which are now given have been kindly supplied by a very satisfied user of this type of battery -Mr. Watson, of Brooklyn, Wellington, Mr. Watson has done a considerable amount of experimenting, and has evolved the strengths of the solution to a nicety, but he is not alone, for several correspondents have written us stating that they have had great success with this charger. It is not universally used because it requires a fair amount of attention, and unless a person is interested in keeping the battery always in the best condition it is no use his attempting

it. In many cases it can be’ used without an accumulator, though a small capacity one is preferable. The battery of primary cells is permanently connected to these and so the accumnulator constantly receives a charge. Here are the parts required for one cell, which will total approximately 1.1 volt:-A glass jar at least 3in. wide at the mouth-telephone type of glass Leclanehe containers are the best, but anything will do providing it is about the size of a 2lb. jam jar. In fact one of these would do quite well if the top were cut off to allow the porous pot to be inserted. An open mouthed jam jar would be even better. One porous pot. Correspondents have had difficulty in obtaining these and so we have entered into an arrangement with the Post and Telegraph Department that they may be obtained at the price of 6d. each upon application to the Stores Manager, P. and T. Department, Wellington, or Chief Postmaster, Christchurch. A quantity of copper sulphate, or, as it is better known, bluestone. For eight or nine cells 2Qibs. will be required every fortnight. Sulphuric acid. This should be obtained from a chemist who seils it 99 per cent. pure. If this is used one part in 60 to 80 parts of water by weight will make a sufficiently strong solution. ‘he amount, of course, wiil vary with the number of, cells to be used. A quantity of copper sheet. A quantity of scrap.zinc, which can be obtained from any foundry or the "tin" lining of packing cases. Distilled or pure rain water coilected in an earthenware jar.

An ounce of mercury to each pot. This is not ‘essential but it lengthens the life of the zines. For. a six-yolt accumulator about 9 cells: will be’ ample and should, if valves of light filament consumption are used, keep the battery fully charg. ed. For four volt valves 6 or 7, will be ample and for two volt, 4 will be needed. The assembly can be quite well. understood from the accompany: ing diagram.

A charger for a four-valve set. Two two-volt low-capatiy accumulators are shown in series. The scrap zine is collected, melted down, and moulded into rods 7-8ths or an inch thick and long enough to clear the porous’ pot. While in the mould place a terminal taken from an old "A" cell. This has a long shank, and will make a good contact with the zine, otherwise a copper wire properly cleaned should be pushed in. It should be long enough to connect with the copper of the next cell. Those who do not wish to goto the. trouble of making

their own zincs can. obtain them ready made. These are amalgumed and will make unnecessary the use of mercury. The thicker rods which can be home-made as we have described will give better service. Having moulded the rods, the next task is to prepare the copper. There is no wear on this, so the thinnest sheet copper can be used, 24-gauge being quite suitable and can be obtained from an ironmonger or metal worker, It is: eut into strips 63in. x 2in. wide. A terminal from the outside zine container of ‘an old "A’’. cell should, be soldered on to the short side for cqntact with the wire on the zinc of {he next cell. It will be found after a cell has been operating for some time that the ‘copper will become heavier, This is due to a deposit from the copper sulphate, or bluestone. The deposit is pure copper, and one of our correspondents at least sells this when it becomes too thick and obtains the price of a new set of plates thereby. SO Into the porous pots, which should be thoroughly clean, pour an ounce of mercury. This should be just sufficient to thinly cover the bottom of the pot. This is, of course, unnecessary if the zinc is amalgumed or if the constructor does not intend to use mercury. On the zine pour a solution of sulphuric and water.. To make this solution with pure sulphuric, put 10lb. weight of water_€ into a container and pour in very slowly two ountes weight of sulphuric acid. The method of mixing sulphuric acid and water is very important. Pour the sulphuric acid slowly on to the water, not the water on to the sulphuric. The latter will probably cause an explosion. Those who cannot obtain pure sulphurie ¢ould use commercial, which, being not so pure, must be mixed at a strength of one part to 40 by weight. Epsom salts may be used instead of the sulphuric, and a_ half-saturated solution is made by mixing 6% ounces Epsom salts to a pint of water. The sulphurie acid solution is now poured into the porous pots, which are placed in the jars. Put a handful of bluestone into each pot and pour upon it the distilled water. Now insert the zines and the cells are complete. we. HEY are connected up as is’ in the diagram. The zinc of one is eonnected to the copper of the other until the required number of cells are connected up. There will be a zine and .

copper left and these will be the negative and positive of the charger. . Connect these to the terminals of:'the accumulator. Do not worry because the voltage of the charger is higher than the voltage of your valves, because if an accumulator is between the two there will be no damage to either. If, however, they. are running 2 set of valves direct, the voltage must be the same, _ At an "A" battery the Daniel Cell will supply at least half an amp, so will be quite suitable for 4 or 5 valves sets using low filament consumption valves. If your set uses .06 valves of the 221 or "A" type the charger will do quite well as an "A" battery. As we mentioned previously, the battery will need an amount of attention. per sulphate must be added every fortnight, and the zines will probably wear through in about six months.

GRAVITY TYPE DANIEL CELL. A useful expedient where regular Daniel cells cannot be used. (1) Wooden plug, 4in, diam.; (2) brass rod, about 1-8in, diam,; (3) zine plate, in, thick; (4) ° copper wire; (5) distilled water;. (6) bluestone; (7) copper plate, 6in. x 4in. wx. 1-16in. The water should cover the zine plate. Apart from this, the battery should give excellent service. If anyone is in difficulty with this charger or requires further information they may obtain it by writing the Technical Editor.