CARE OF BATTERIES

Radio Record, Volume I, Issue 11, 30 September 1927, Page 15

CARE OF BATTERIES

SOME VALUABLE HINTS The following valuable hints on batteries were recently given by Mr. Preston Billing from. 3YA:If really satisfactory results are to be obtained with distant. stations the following points must be carefully attended to. Commencing: with what is termed the A battery (im case there are some listeners who are not certaitt which is the A battery, it is the battery which furnishes the power for lighting your valves), this is usually a wet or accumulator one of 6 volts pressure This battery should be kept fully charged; also it is advisable to purchase on: of a reasonable capacity in _amp-hours, as the discharge will | be" more uniform and will last longer | with a given, charge The condition of charge or otherwise of this battery may be best ascertained by means of the hydrometer. ‘This device measures the density of the acid in the cells and therefore gives a reliable indication of the state of charge, as the density of the sulphuric acid is proportional to the amount of charge in it. Most of these hydrometers have a range "of readings from 1150 spg. (specific gravity) to 13800 spg. Of course, all batteries are not filled to the same density-you can ascertain from the label on your battery the particular acid density at which it should be filled. For the sake of demonstration, supposing the battery was filled with an acid with 1750 spg., then when this particular battery is fully charged the hhydrometer will read 1750 spg. or thereabouts It shonld not be discharged below 1175 spg. If the _battery shonld be left in this condition for any length of time the plates will become sulphated. Should this occur it will be found difficult to eliminate the condition. It will also be found the: battery has lost a considerable amount of its former capacity on account of the sulphate deposit. Battery capacities are rated in what are known as amp-hours, and I will endeavour to explain what is meant by this term. If your set is a 5valve one and uses valves of the 201.A. type the approximate current consumption would be 1} amperes. If your set is in use for, say, three hours an evening, this would give us a total of 3 multiplied by 14, which gives us 32 amp-lhours’ consumption for the evening. Many listeners have their cwn battery chargers, and in order to give them some idea of the time required to replace the charge back into the

«battery the following information will be found very helpful. If your set is in use for 16 hours per week and eonsumes current at the rate of our previous example the total amp-honr consumption for the week will be 20 amp-horrs. Yo replace the charge in the battery, add one-third of the total amp-hours consumed over the discharge period In this instance we will call it 7, which, added to our previous 20, gives us a total of 27 amphours. If your charger operates at, say, a 2 ampere charging rate, it will take 27 divided by 2, leaving 13} hours of time to replace the current used. Always keep vour battery terminals elean, likewise the top of the battery. Unsatisfactory results are often caused through neglect in this respect, especially when clips are used to connect with the battery These clips should be cleaned frequently and wiped with vaseline to keep the acil from = corroding them. Do not forget to add distilled water, as evaporation takes place, and the tops of the plates should not be allowed to show. Sulphuric acid should not he added under any~ circumstances nnless acid is actually spilt or else only on the advice of a battery expert. With referenee to the B batteries, these are of two types: fa) the dry, fb) the wet or accumulator, ‘he majority of sets secm to be equipped with the. fa) type. Thev have the adyantage of requiring little attention excepting renewals, which take place at intervals depending on the B hattery consumption in milli-amnercs of the particular set in use. The use of a C battery is an absolnte necessity, especially as the B battery voltave increases, * This battery lias the effect of reducing the drain on the B batteries and resulis in purer reproduction, You can test vour own B batteries if you have at hand a voltmeter of suitable range. A new 45 volt block will, of course, show a 45 yolt reading or perhaps slightly more. The battery should be discarded when the pressure drops to 387 volts. Another method of testing is to employ a low reading ammeter of, say, 0-3 amperes scale reading, and of what is known as the moving iron type. Kaeh block should be momentarily shorted with the ammeter, and should they be in good condition the instrument will Le deflected smartly across the entire scale. 9 ‘This method must not be practised too often, or else the batteries will suffer, Also, this latter test must not Le applied under any circumstances to aceumulutor or

wet B hatteries You may test ‘the condition of vonr wet Bo batterv be means of the livdrometer as adyised with the A hattery It is highly jmnortant for the BR battery connections of either twne to Le kent eloan in order ta ensure a steady flow of enrrent,

BRSELURSSECOIERPRSORERRERRERGEUCOELEDSSRRERSSGRERED | NOTE BY "MEGOHM" The following paragraph was omitted from the Browning-Drake article Jast week :-It should be noted that the lower the H.T. voltage intended to be used, the more turns will be required on the tickler in order to obtain oscillation at the higher waye-lengths, ‘Turns on the tickler coil must be close together, not spaced as for ‘low-loss’’ winding. The- filament consumption of the P.M. SA valve was given as 1 amp., the decimal point having been omitted, The actual current required is -l amp. at 4 volts.