Test Your Batteries

Radio Record, Volume III, Issue 16, 1 November 1929, Page 30

Test Your Batteries

-WPANY amateurs are under the impression that as long as a "B"’ battery shows some voltage on a voltmeter, it is suitable for use. This is, however, very far from being the case. For instance, if a 90-volt battery which, on being tested, shows 30 volts in con‘nected in series with a new "B* battery, results will not be improved but rather diminished. > This is due to what is known as the | internal resistance of the cells. Simultaneously with the voltage drop comes an increase in the internal resistance, and as soon as a current is demanded of the cell its effective voltage drops to a very low figure. In these circumstances the complete battery may to all intents and purposes be regarded as a resistance. It is, therefore, obviously detrimental to connect it in series with new "B" batteries. A good plan is to discard a battery when its voltage has dropped to twothirds its orginal value. This is especially the case where it is being used on a multi-valve set. Distortion, crackling, and many other troubles are traced to worn-out "B" batteries, and the improvement in reception when they are replaced is well worth the outlay.