WHAT ACCUMULATOR SHALL I USE?

Radio Record, Volume I, Issue 10, 23 September 1927, Page 15

WHAT ACCUMULATOR SHALL I USE?

oo will last. This is a question that a good many prospective set-owners are considering, and much depends upon getting a correct answer, ‘To purchase an accumulator without knowing how long it will Jast upon your set before requiring recharging is obviously unwise; but if the following simple rules are borne in mind, there is no need to rely upon other people’s opinion, for you can work out accurately what type of- accumulator is required, and how long it ‘The current which a valve takes out of an accumulator is reckoned in amperes. Some of the _ bright-emitter valves take half an ampere or more to light them. Other valves of the semidull emitter type take about a quarter of an ampere, whilst the most economical type of all are the ‘‘.06’s," which, as their title implies, take only six-one-hundredths of an amipere-ie., three-fiftieths. A Simple Caiculation. When several valves are used at once, their respective current consumptions must be added together, to find out how much current the set will need. For instance, three of the .06 type will take a total of .18 ampere, whilst two valves, each taking .25 ampere, follow- ed by .a power-valve taking, say, .5 ampere, would take a total of one aimpere (more than five times as much). As every valve-maker indicates the valve’s current-consumption upon the valve-box, it is a very easy matter to determine the current required by any given number or type of valves. ‘hen simply multiply this figure by the number of hours which the accumulator must run without recharging, and you have arrived at the class of accummulator which is required. To make this perfectly clear, ict us take the case of a four-valve set, which is to be work---EE

ed from, say, Cossor Wuncells. We will assume the owner lives in the country and can only charge his accumvlator once a fortnight, and that he will use the set for an average period of four hours per day. Determining Required Capacities. Consulting the valve-maker’s specification, we find that each valve.is rated at 25 ampere, so that four valves will consume a total current of one ampere. We have to multiply this by the number of hours which the accumulator must run without recharging, in this instance 14 x 4=56. The required accumulator, then, must deliver one ampere for 56 hours-i.e., it must have a capacity of at least 56 ampere hours. The nearest obtainable figure would be 60 actual ampere hours, which would just give a little necessary margin. If the set had been only a two-valve set, the figures would have been halved, the figures in this.instance being 25 «= 2 {(=.5). multiplied by 56, =23 actual ampere hours. Our final example, worked in the reverse direction, will make the principle perfectly clear. How long would a 20 actual ampere hour accumulator last without recharging, if used upon a set employing two bright emitter valves, each rated at, .7 ampere? The total current required by the set would be 1.4 amperes, and this number must be divided into the 20 actual empere hours of the accumulator, as folOWS i20 — =14.28 1.4 This shows that the accumulator would only last about fourteen hours without recharging, so an accumulator with a greater capacity would be necessary, or, better still, dull-emitter valves should be } employed instead.