RESISTANCES IN SUPPLY

Radio Record, Volume I, Issue 40, 20 April 1928, Page 13

RESISTANCES IN SUPPLY

QUITE recently a paragraph was reprinted from an American journal giving a method of giving equal! drain over the whole of the cells of a

B acemulator by treating the total voltage as the output of a B eliminator and by means of variable resistances cu‘ting down the voltage to suit the several valves. A correspondent figured the matter out, and sent his view of the question, showing that the consumption of current would be greater than by the tapping system, as the drain over the whole battery would be equal to that of the total of all the valves. This is quite correct, and at first sight the idea appears to be uneconomical. But we must not lose sight of the purpose of the proposed idea-the equal use of all the cells in the battery. Under the tapping system the higher voltage cells are putting out less current, as they are supplying fewer valves, and. so, in order to fully charge the latter, the former always receive a considerable overcharge, and this is what it is sought to avoid. By adopting the B -eliniinator system of control, we dissipate in the resistances the power that would gtherwise be expended in overcharge, causing a certain amount of deterioration of the overcharged cells, and the battery is charged up in the usual time, no part being obliged to receive an overcharge as formerly. In the issues of September 30 and October 7 last, "Megohm" described a method of charging a 112-volt accumulator at low voltage by connecting the rows of cells in parallel by the substitution of a "parallel" connector in place of the "series" connector. In the original battery the unequal use of cells was provided for by the use of a "reverse" connector, which, when substituted by the "series" coynector, had the same effect as if four rows of high voltage cells were lifted over and used for low voltage, the low voltage being used as high. This connector was not described, as it was considered that many constructors would consider it "too complicated." But all the same, the battery is most convenient when constructed with the switching arrangement, as by merely changing the con-necting-piece the battery is charged by an A battery charger, giving 16 to 20 volts and instantly connected in "sries" or "reverse" at will. An alternative set of figtres is marked under the tapping sockets for use when in "reverse." Any constructor writing in will be supplied with a diagram of this connector.