Ques. How is the cadmium test made?
Ans. A plate of cadmium is mounted in a hard rubber frame and immersed in the electrolyte. The test consists in taking voltage readings between the cadmium plate and the positive or negative plates of the cell. During charge the cadmium plate reads negative to the negative plate, until the cell is about full, when the reading should be zero; the charge should be continued until the cadmium reads 0.2 volt positive to the negative while charging at the normal rate.
Ques. Name some portable instruments that should be provided for testing batteries.
Ans. 1, a hydrometer syringe (specific gravity tester); 2, an acid testing set (can be used instead of the syringe); 3, a low reading voltmeter; 4, suitable prods, and 5, a thermometer.
Ques. What precaution should be taken in charging a battery?
Ans. Care should be taken not to have a naked flame anywhere in its vicinity.
To either charge or discharge a battery at too rapid a rate involves the generation of heat. Thus, while this is not liable to result in a flame under usual conditions, the battery may take fire, if it be improperly connected or improperly used.
Ques. What is the effect of varying the charging current?
Ans. In charging a storage cell, particularly for the first time, a weaker current than that specified may be used with the same result, provided the prescribed duration of the charge be proportionally lengthened. The battery may also be occasionally charged beyond the prescribed voltage, ten or twenty per cent. overcharge effecting no injury, although if frequently repeated, it shortens the life of the battery.
Ques. What are the charge indications?