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

The automatic plant most desirable--How an automobile lighting and
starting system works--How the same results can be achieved in
house lighting, by means of automatic devices--Plants without
automatic regulation--Care necessary--The use of heating devices on
storage battery current--Portable batteries--An electricity
"route"--Automobile power for lighting a few lamps.

The water-power electric plants described in preceding chapters are
practically automatic in operation. This is very desirable, as such
plants require the minimum of care. It is possible to attain this same
end with a storage battery plant.

Automatic maintenance approaches a high degree of perfection in the
electric starting and lighting device on a modern automobile. In this
case, a small dynamo geared to the main shaft is running whenever the
engine is running. It is always ready to "pump" electricity into the
storage battery when needed. An electric magnet, wound in a peculiar
manner, automatically cuts off the charging current from the dynamo,
when the battery is "full;" and the same magnet, or "regulator,"
permits the current to flow into the battery when needed. The
principle is the same as in the familiar plumbing trap, which
constantly maintains a given level of water in a tank, no matter how
much water may be drawn from the tank. The result, in the case of the
automobile battery, is that the battery is always kept fully charged;
for no sooner does the "level" of electricity begin to drop (when used
for starting or lighting) than the generator begins to charge. This is
very desirable in more ways than one. In the first place, the energy
of the battery is always the same; and in the second place, the mere
fact that the battery is