===================================================

CHAPTER 12.
GENERAL SHOP INSTRUCTIONS.
--------------------------

CHARGING BATTERIES.

The equipment for charging batteries, instructions for building and
wiring charging benches have already been given. What we shall now
discuss is the actual charging. The charge a battery receives on the
charging bench is called a "bench charge."

Battery charging in the service station may be divided into two
general classes:

1. Charging batteries which have run down, but which are otherwise in
good condition, and which do not require repairs.

2. Charging batteries during or after the repair process.

The second class of charging is really a part of the repair process
and will-be described in the chapter on "Rebuilding the Battery."
Charging a battery always consists of sending a direct current through
it, the current entering the battery at the positive terminal and
leaving it at the negative terminal, the charging current, of course,
passing through the battery in the opposite direction to the current
which the battery produces when discharging. When a battery discharges
chemical changes take place by means of which electrical energy is
produced. When a battery is on charge, the charging current causes
chemical changes which are the reverse of those which take place on
discharge and which put the active materials and electrolyte in such a
condition that the battery serves as a source of electricity when
replaced in the car.

Batteries are charged not only in a repair shop but also in garages
which board automobiles, and in car dealers' shops. No matter where a
battery is charged, however, the same steps must be taken and the same
precautions observed.

When a Bench Charge is Necessary:

(a) When a battery runs down on account of the generator on the car
not having a sufficient output, or on account of considerable night
driving being done, or on account of frequent use of the starting
motor, or on account of neglect on the part of the car owner.

(b) Batteries used on cars or trucks without a generator, or batteries
used for Radio work should, of course, be given a bench charge at
regular intervals.

(c) When the specific gravity readings of all cells are below 1.200,
and these readings are within 50 points of each other.

Should the gravity reading of any cell be 50 points lower or higher
than that of the other cells, it is best to make a 15-seconds high