THE 112-VOLT B ACCUMULATOR

Radio Record, Volume I, Issue 15, 28 October 1927, Page 14

THE 112-VOLT B ACCUMULATOR

t ALTERNATIVE TIPS FROM A CONSTRUCTOR The following letter was addressed to "‘Megohm" by a Wanganui constructor, who appears to have tackled the B accumulator with a determination to make a thoroughly lasting and serviceable battery. ‘Lhe letter speaks. for itself, and as it coutains an alternative mietliod of construction, it is printed in full, Letters such as this and others that have been received from constructors are appreciated, as they show that the page is appreciated ,and helpful. ‘The letter reads as follows :-~ You have expressed a wish in the "Record"? to hear the results obtained by your readers in carrying out the ideas and suggestions which you publish, so I am wriling to let you know that the B battery which I have constructed more than fulfils the claims which you made in your descriptive article. In the first place I wish to thank you for your previous reply to my queries re the battery. I made a few variations, which were as follow: (1) Instead of making a grid work of hatiens to support the tubes I bored the necessary number of holes in a piece of three-ply which just fits inside the case; to steady the bottom of the tubes I burnt seats with a red hot piece of iron, one inch diameter, and rounded, to correspond with the shape of the end of a test-tube. This makes a neat job, and a good deal less trouble than the battens. I have made the case, etc., suitable for 140 volts, but so far as my set only requires 90 volts I have made the battery up to 98 volts. The punching of the plates was a tedious job, but was facilitated somewhat by a punch which made five holes at a time; 60 holes were made in each positive and negative plate, holes varying from 1-l16in. to fin. in diameter. (2) Instead of using wires for connecting up each I4v. section of the battery I burned on lead bridges. (8) I inserted l}in. wide strips of celluloid between each 14-volt section; then made a sort of inner lid of celluloid which sits right down on these strips. Where necessary I burned on lead strips fo stand vertically and cut the lid to allow about + inch to come through, I don’t think I will bother about the front panel and plugs, the inner celluloid gives a fair amount of protection to the battery, and the usual spring clip can tap the battery at 24, 26, 28, 30, 42, 52, 56, 70, 84, 90, and 98 volts. (4) To grease the top of the tubes and the lead connection I melted motor gear grease in a tobacco tin and. then dipped the ends of the tubes etc., to a depth of tin. (5) Peroxide of lead was not available, so ordinary red lead was used for the positive plates and litharge for the negatives. This pasting was tedious, but seems welf worth while. For mixing I used aw@® of the strength recommended by you, 1170 sp. T For charging I used an A and B charger, and gave a continuous charge of about 100 milliamps for about 70 hours, by which time the positives had assumed the characteristic deep chocolate colour, the specific gravity had tisen to 1220, the tubes were gassing freely, and the voltage was right up. On connectirig up to my set IT was nleased to find that it worked with a tick and a zip which had been absent for some time owing to the gradual decline of mv drv hatteries, which were down to about 67 volts. Since using the new hattery T have pulled in sev-

eral stations, including 2UH and KFON, which I had not had previous-. ly. I gave the battery about 15 hours’ use on the set, and then put it on charge again, as I thought it better not to try and get too much out of it for a start. It apparently still had plenty of kick at the end of the first 15 hours’ use, voltage right up, and posilive plates still deep chocolate, but for a while I intend to use it and charge it on the principle of a little in and a little ont. The batterv has cost: Test tubes, 18s. 1ld.; lead, 13s. 94.; litharge and red lead, 1s. 6d.; sulphuric acid, 2s.; brass screws, 64.; three-ply, Is., a total of £1 16s. 10d. The case was made from henzine-box wool, which was dressed, stained and polished. ‘hese materials, as well as solder and grease, IT had, so the trifle these were worth would still keen the total cost of the batterv under £2. It. of course, remains to be seett whether fhe paste will hold inside the folded plates, but with a low charging rate and not over-dischareing I do not anicipate much tronble, and I must sav that at present I feel very nleased with the result-VYours in Radio, ‘‘Positive " (Provided that the plates have been closed at the bottom as directed, and not too great a charging rate is adonted. no fronble is to be anticipated. — "Megohm.’’)