Man's physical universe



as the sulfuric acid is removed from the solution as a battery is discharged,

a hydrometer is all that is necessary to determine whether

or not a battery needs charging. When the battery is charged, the

electrolysis carries hydrogen to the cathode, re-forming sulfuric acid,

while the oxygen at the anode restores the lead oxide, and the original

condition of the battery is restored.

The difference of potential between the two electrodes of a charged

storage battery is 2 volts. The voltage of a battery may be increased

2 volts for each cell added, the cells being connected in series. Thus a

6-volt battery has 3 cells, and a 12-volt battery has 6 cells. It is customary

to place each pair of electrodes in separate glass or hardrubber


more plates.

Each electrode may consist of one, two, three, four, or

The number of plates increases the surface exposed and

thus increases the amount of energy that the battery can store, but it

does not change the voltage. The cathode and anode plates must be

kept from touching each other in order to prevent internal short circuits,

so they are separated by insulators made of wood, corded hard

rubber, or glass cloth which will

be pervious to the sulfuric acid but

will not be acted upon by it.

The storage battery is used most extensively in automobiles; without

a storage battery a self-starter would be impossible. The battery is

kept in the charged condition in the automobile by a generator which

is operated when the engine is running. Storage batteries for modern

cars must be very rugged because they not only furnish the energy

to start the car, but they also operate the lights, radios, ignition

systems, sirens, and cigarette-lighters; in addition, they must withstand

severe and almost constant jolting about and must have a large

reserve of power for starting cars in the winter.

Storage batteries are used to operate radio sets in remote communities

not served by electrical lines. They are also used in private

lighting plants to supply power when the generator is not in use.


are operated by the energy from storage batteries when they

are submerged.

Edison invented another very rugged but less efficient type of storage

battery consisting of a negative electrode of iron oxide in


steel pockets and a positive electrode of nickel hydrate in perforated

steel tubes immersed in a solution of potassium hydroxide.

This battery

is especially valuable because it may be discharged to zero voltage,

accidentally charged in reverse, or short-circuited without permanent

injury. It is relatively light in weight, compact and durable,

and has a long life. Severe vibrations and concussions do not affect it.

Such storage batteries are used for lighting and air conditioning of

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