The electrical system of your car acts
like the nervous system in your body. In your car, messages are passed
through metal wires in the form of not-so-tiny electrical currants where they
are converted into power for the ignition, computers, lights & accessories of
the car.
Many vehicle electrical components are not
directly connected with the vehicle engine or drive train operation, such as the
lights, horn, windshield wipers, radio,
power windows and locks. Wiring to devices which will not be operated
except when the vehicle is being driven, such as the windshield wipers, are
typically routed through the ignition switch. Wiring to the vehicle
systems which can be operated at any time, such as the lights, are powered
directly from the vehicle's battery.
Each circuit has a switch that acts like a
drawbridge. When the drawbridge is lowered, the circuit is complete and
the electrical current can flow; when the drawbridge is up, the circuit is
incomplete and the current cannot flow. For example, when you turn on the
headlights, a switch lowers the drawbridge for that circuit, the circuit is
complete and current flows to the illuminate the headlights.
Relays are back up safety switches that
are used on circuits with particularly strong electrical current.
The most common problem is typically blown
fuses and fusible links, which are lengths of wire calibrated to melt when
current flow exceeds a certain value. Sometimes fuses overheat or vibrate
apart after long service. However, the more common cause of blown fuses is
a short in the wiring or an electrical device or an overload in an electric
motor, switch or solenoid.
Shorts allow a constant flow of current
through the battery which can run down a battery overnight if not corrected.
Other wiring problems include bad connections at plug-in connectors caused by
dirt, grease, corrosion, overheating or short circuits. Wires can also
short inside of the harness due to vibration or from being pinched between
vehicle parts.
Parasitic drains are electronic components
that place a small, continuous drain on the battery after the ignition is turned
off. The current drain from these loads is extremely small and typically
does not discharge the battery completely.
The
Battery
The battery plays a key role in the
overall functioning of the
electrical
system. To ensure reliability and extend useful service life, the battery
should receive periodic inspection and maintenance. The level of
electrolyte (the liquid in each battery cell) must be correct. The battery must
be fully charged. The posts must be clean. Battery cables and
terminals must be in good condition and firmly attached.
As with most things in life, a battery
ages and grows tired with use. Cold weather and frequent jump-starting reduces
the efficiency of batteries. Although it is difficult to determine the
exact amount of useful life remaining in any battery, several tests can used as
indicators of its ability to perform satisfactorily.
100%
65%
40%
18%
80˚
32˚
0˚
-20˚
A battery's efficiency is
dramatically affected by the temperature. On a very cold day, A battery
may lose up to 80% of it's ability to provide a spark, while it make take
twice the energy to start the car.
Battery sizes vary greatly due to the
variety of vehicle types and sizes on the road. However, a battery's
electrical size has almost no relationship to its physical size. Battery
manufacturers use the following battery ratings:
Cold Cranking Amps (CCA) - The
maximum amount of current that flows for 30 seconds at 7.2 volts with the
battery temperature at 0˚F. This measurement indicates how much current
the battery can produce when cold and is the standard measurement for modern
batteries.
Cranking Amps (CA) - The maximum
amount of current that flows for 30 seconds at 7.2 volts with the battery
temperature at 32˚ F. This measurement may also be called hot cranking
amps (HCA).
Reserve Capacity (RC) - The
number of minutes that the battery can produce 25 amps at 10.5 volts with
battery temperature at 80˚ F. Reserve capacity indicates how long the
battery can operate the vehicle electrical system in the event of a charging
system failure.
Please note:batteries can be
dangerous and they can explode! Battery electrolyte contains sulfuric acid
and can cause serious skin and eye burns. Be very careful and always wear
gloves when servicing yourself!
Cold weather note: If a battery is frozen,
it cannot be tested. Only badly discharged batteries will freeze. In
addition, freezing generally damages the battery plates. Therefore, frozen
batteries should be replaced. If it is not replaced, it must be thawed and
recharged before testing.
One last note. Batteries should be
recharged slowly, 5-7 amps, whenever possible. Slow charging
minimizes the risk of possible damage or overheating caused by charging. Be
certain to remove the battery when fully charged, however, as overcharging is
harmful.
power windows and locks. Wiring to devices which will not be operated
except when the vehicle is being driven, such as the windshield wipers, are
typically routed through the ignition switch. Wiring to the vehicle
systems which can be operated at any time, such as the lights, are powered
directly from the vehicle's battery.
For example, when you turn on the
headlights, a switch lowers the drawbridge for that circuit, the circuit is
complete and current flows to the illuminate the headlights. 
electrical
system. To ensure reliability and extend useful service life, the battery
should receive periodic inspection and maintenance. The level of
electrolyte (the liquid in each battery cell) must be correct. The battery must
be fully charged. The posts must be clean. Battery cables and
terminals must be in good condition and firmly attached.
Cold weather note: If a battery is frozen,
it cannot be tested. Only badly discharged batteries will freeze. In
addition, freezing generally damages the battery plates. Therefore, frozen
batteries should be replaced. If it is not replaced, it must be thawed and
recharged before testing.
