Pour the acid into the water. Never under any circumstances pour the water into the acid, else an explosion may occur from the heat developed. Mix the electrolyte in a stone crock, or glass container, stirring with a glass rod, and testing from time to time with a hydrometer. Let it stand until cool and then pour it into the battery jars, filling them to ½ inch above the top of the plates.
Then begin charging. The first charge will probably take a longer time than subsequent charges. If the installation is of the automatic type, all that is necessary is to start the engine. If it is not of the automatic type, proceed as follows:
First be sure all connections are right. Then start the engine and bring the dynamo up to its rated speed. Adjust the voltage to the pressure specified. Then throw the switch connecting generator to battery. Watch the ammeter. It should register in amperes, one-eighth of the ampere-hour capacity of the battery, as already explained. If it registers too high, reduce the voltage of the generator slightly, by means of the field rheostat connected to the generator. This will also reduce the amperes flowing. If too low, raise the voltage until the amperes register correctly. Continue the charging operation until the cells begin to give off gas freely; or until the specific gravity of the electrolyte, measured by the hydrometer, stands at 1.24. Your battery is now fully charged. Throw the switch over to the service line, and your accumulator is ready to furnish light if you turn on your lamps.
Occasionally add distilled water to the cells, to make up for evaporation. It is seldom necessary to add acid, as this does not evaporate. If the battery is kept fully charged, it will not freeze even when the thermometer is well below zero.
A storage battery should be installed as near the house as possible—in the house, if possible. Since its current capacity is small, transmission losses must be reduced to a minimum.
In wiring the house for storage battery service, the same rules apply as with standard voltage. Not more than 6 amperes should be used on any single branch circuit. With low voltage batteries (from 12 volts to 32 volts) it is well to use No. 10 or No. 12 B. & S. gauge rubber-covered wire, instead of the usual No. 14 used with standard voltage. The extra expense will be only a few cents for each circuit, and precious volts will be saved in distribution of the current.
CHAPTER XII
BATTERY CHARGING DEVICES