"SHORTED" BATTERIES

Radio Record, Volume I, Issue 34, 9 March 1928, Page 2

"SHORTED" BATTERIES

HELPFUL SUGGESTIONS H¥ useful life of a "B" battery is often prematurely ended by a short-circuit of that battery, without the owner of the set in which it is used realising when or how it hap. pened. If, for example, new batteries which have supposedly been subjected to a purely normal drain for a short time, show an abnormally low voltage upon being tested, the chances are that they have been ruined by some faulty connection, either on the batteries themselves or in the set. Before a claim is made the battery is defective, the connections inside tlie set should be examined. There may be a faulty or loose connection, 4 valve may be defective, a by-pass condenser may have broken down, or some metal object may have fallen across the battery terminals. The appearance of the battery itself will also help the set owner to determine whether or not a "short" has oecurred, Corrosion Caused, The cells of a ‘‘shorted" battery will all, or in part, be corroded, the electro-

RRL SS hos pec ND et TSP bend lyvte will generally leak out, and the pressure of a finger nail against the zine shell will often be sufficient to break through it, especially near the top. This point on the shell is where the upper part of the "bobbin’’ ends, and corrosion there is more pronounced than at any other place. However, in the case of batteries which have become "shorted" after having delivered a great part of their energy through normal use, a subsequent short-circuit is generally not sufficient to cause any change in the casual appearance of the zinc. There are other methods of determining in the laboratory whether or not a battery has been subjected. to a "short" or an extraordinarily heavy drain, but these are too complicated to be mentioned here. Internal ‘*Shorts.’’ Internal "shorts"? may be found in a ‘*B" battery, but due to the rigid inspections made at the factories ‘where really good batteries are made, these are rare. In the case of an internal "short," a single cell, or probably a few, will show a low voltage and the balance will show their normal voltage (1.5-1.6). Yet there are extreme cases where all cells will be low. due to a stray wire or the like having been accidentally dropped tmto the battery as it was being assembled.

Another point of importance is that it is possible to "short" one-half of a 45-volt battery and not the other half; that is, from the negative to the centre 22}-volt terminal, or from the centre to the 45-yolt terminal. This is explained by the fact that batteries of this type really consist of two separate 22}-volt blocks connected together by a common wire, and also that taps are sometimes taken from the batteries to the set that involve a partial battery. l‘or example, if two 45-volt batteries are used on a set, 2 tap may be taken from either 22} volts or from 674 volts. A short’? occuring im any of these places would include ouly a portion of a 45-volt battery. Valuable Hints. Here are some suggestions for the care of ‘‘B" batteries that should help to prolong their useful life. Never test the strength of a battery by shorting it through a wire and observing the intensity of the spark produced. Batteries should be tested by means of a good voltmeter-one having a resistance of at least 50 ohms per volt and preferably 100 ohms per volt. Voltmeters not conforming to the above specifications cause the consumer to discard his batteries when they are still capable of giving many more hours of useful service, Never use an anineter. Examine the Set. If large sparks are persistently produced when batteries are connected to a set, the valves of which are not lighted, the set should be examined for possible ‘‘shorts’? or broken down bypass condensers. Never leave batteries connected to a set behaving in this manner. Should the batteries become hot immediately after being connected to a set, a short-circuit is indicated, Disconnect them immediately, as "B’’ batteries will be completely ruined when short-circuited for even a short period