08-5
ENGINE ELECTRIC SYSTEM
RODIUS 2005.07
1452-01
1. DESCRIPTION AND OPERATION OF ENGINE
ELECTRICAL SYSTEM
1) BATTERY
The sealed battery is standard on all cars. There are no vent plugs in the cover. The battery is
completely sealed, except for two small vent holes in the sides.
These vent holes allow the small amount of gas pro-duced in the battery to escape. The battery
has the following advantages over conventional batteries:
No water addition for the life of the battery.
Overcharge protection. If too much voltage is applied to the battery, it will not accept as
much current as a conventional battery. In a conventional battery, the excess voltage will
still try to charge the battery, leading to gassing, which causes liquid loss.
Not as liable to self-discharge as a conventional battery. This is particularly important when
a battery is left standing for long periods of time.
More power available in a lighter, smaller case. -
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The battery has three major functions in the electrical system. First, the battery provides a
source of energy for cranking the engine. Second, the battery acts as a voltage stabilizer for the
electrical system. Finally, the battery can, for a limited time, provide energy when the electrical
demand exceeds the output of the alternator.
2) RATINGS
A battery has two ratings: (1) a reserve capacity rating designated at 27°C (80°F), which
is the time a fully charged battery will provide 25 amperes of current flow at or above 10.5 volts;
(2) a cold cranking amp rating determined under testing at -18°C (0°F), which indicates
the cranking
load capacity.
▶Reserve Capacity
The reserve capacity (RC) is the maximum length of time it is possible to travel at night with the
minimum electrical load and no alternator output. Expressed in minutes, the RC rating is the
time required for a fully charged battery, at a temperature of 27 °C (80 °F) and being
discharged at
a current of 25 amperes, to reach a terminal voltage of 10.5 volts.
▶Cold Cranking Amperage
The cold cranking amperage test is expressed at a battery temperature of -18°C (0°F).
The current rating is the minimum amperage, which must be maintained by the battery for 30
seconds at the specified temperature, while meeting a minimum voltage requirement of 7.2
volts. This
rating is a measure of cold cranking capacity.
The battery is not designed to last indefinitely. However, with proper care, the battery will
provide many years of service. If the battery tests well, but fails to perform satisfactorily
in service for no apparent reason, the following factors may point to the cause of the trouble:
08-6
RODIUS 2005.07
1452-01
ENGINE ELECTRIC SYSTEM
Vehicle accessories are left on overnight.
Slow average driving speeds are used for short periods.
The vehicle’s electrical load is more than the alternator output, particularly with the
addition of aftermarket equipment.
Defects in the charging system, such as electrical shorts, a slipping alternator belt, a faulty
alternator, or a faulty voltage regulator.
Battery abuse, including failure to keep the battery cable terminals clean and tight or a
loose battery holddown clamp.
Mechanical problems in the electrical system, such as shorted or pinched wires. -
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3) CHARGING SYSTEM
Alternators use a new type of regulator that incorpo-rates a diode trio. A Delta stator, a rectifier
bridge, and a rotor with slip rings and brushes are electrically similar to earlier alternators.
A
conventional pulley and fan are used.
There is no test hole.
4) CHARGING TIME REQUIRED
The time required to charge a battery will vary depending upon the following factors:
Size of Battery
- A Completely discharged large heavy-duty battery required more than twice the recharging
time as a completely discharged small passenger car battery.
Temperature
<00540047004700680047009300960095008e008c00990047009b00900094008c0047009e00900093009300470089008c00470095008c008c008b008c008b0047009b00960047008a008f00880099008e008c00470088009500a0004700890088009b009b00
8c009900a000470088009b004700540058005f00b6006a0047>(0°F) than at 27°C
(80°F).
When a fast charger is connected to a cold battery, the current accepted by the battery will
be very low at first. The battery will accept a higher current rate as the battery warms.
Charger Capacity
- A charger which can supply only 5 amperes will require a much longer charging period
than a charger that can supply 30 amperes or more.
State-of-Charge
- A completely discharged battery requires more than twice as much charge as a onehalf
charged battery. Because the electrolyte is nearly pure water and a poor conductor in a
completely discharged battery, the current accepted by the battery is very low at first. Later,
as the charging current causes the electrolyte acid content to
increase, the charging current will likewise increase. ▶
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