Figure 2-10.Battery drain test setup.
rating by two. For example, a battery with 400 cold-
cranking amps rating should be loaded to 200 amps
(400 ÷ 2 = 200). Connect the battery load tester, as
shown in figure 2-11. Turn the control knob until the
ammeter reads the correct load for your battery.
After checking the battery charge and finding the
amp load value, you are ready to test battery output.
Make sure that the tester is connected properly. Turn
the load control knob until the ammeter reads the
correct load for your battery. Hold the load for 15
seconds. Next, read the voltmeter while the load is
Figure 2-11.Instrument hookup for battery capacity test.
applied. Then turn the load control completely off so
the battery will not be discharged. If the voltmeter
reads 9.5 volts or more at room temperature, the
battery is good. If the battery reads below 9.5 volts at
room temperature, battery performance is poor. This
condition indicates that the battery is not producing
enough current to run the starting motor properly.
Familiarize yourself with proper operating
procedures for the type of tester you have available.
Improper operation of electrical test equipment may
result in serious damage to the test equipment or the
unit being tested.
QUICK CHARGE TEST.The quick charge
test, also known as 3-minute charge test, determines if
the battery is sulfated. If the results of the battery load
test are poor, fast charge the battery. Charge the battery
for 3 minutes at 30 to 40 amps. Test the voltage while
charging. If the voltage goes ABOVE 15.5 volts, the
battery plates are sulfated and the battery needs to be
The generator is a machine that applies the
principle of electromagnetic induction to convert
mechanical energy, supplied by the engine, into
electrical energy. The generator restores to the battery
the energy that has been used up in cranking the
engine. Whether the energy required for the rest of the
electrical system is supplied directly by the generator,
by the battery, or by a combination of both depends on
the conditions under which the generator is operating.
The two types of generators are as follows:
The dc generator supplies electrical energy
directly to the battery and or electrical system
through various regulating devices.
The ac generator (alternator) has the same
function as the dc generator but because only
direct current can be used to charge a battery, a
component, called a rectifier, must be used to
convert from alternating to direct current. The ac
generator (alternator) will be explained in
further detail later in this chapter.
Direct-Current (dc) Generator
The dc generator (fig. 2-12) essentially consists of
an armature, a field frame, field coils, and a
commutator with brushes to establish electrical
contact with the rotating element. The magnetic field
of the generator usually is produced by the