The higher the AWG Number, the smaller the wire.
The larger the amperage of a circuit, the larger the wire that is needed.
Load requires 1 gallon per minute of flow
at 12 volts. Since the load requirement is
met we can determine the hose (wire) size
is “OK.”
— Source of Flow
Alternator and Battery
12 volt
Adequate Wire Size (gauge)
Inadequate Wire Size (gauge)
Load requires 1 gallon per minute of flow at
12 volts, but only half that mount can be
delivered. Therefore, the hose (wire) size is
too small.
— Source of Flow
Alternator and Battery
12 volt
1 inch
diameter hose
1/2 inch
diameter hose
When electrical systems are designed, the wire size is calculated for the specific requirements of the electrical components being
used. When electrical components are added or upgraded, the wire size has to be upgraded also. For example, replacing a
low torque starter with a high torque starter will normally require the battery cables and possibly the battery to be upgraded.
A word about wire gauge
The size of a wire (gauge) is expressed in terms of a standard American Wire Gauge (AWG) measurement.
The higher the AWG number, the smaller the wire. For example, a 14 gauge wire is smaller than a 10 gauge wire. The smaller
the wire, the greater its resistance to the flow of electrons and the greater the heat generated when the wire is conducting
electricity. The heat can destroy insulation and even kindle a fire. THE LARGER THE AMPERAGE OF A CIRCUIT, THE LARGER THE
Think of wiring as a water hose.
The electrical current is like water flowing through the hose. The source or supply of this water would be the battery and
alternator. Look at the diagrams below. The first diagram shows a one inch diameter hose which allows one gallon per minute of
flow. Since the load requires only a gallon per minute of flow, we can say that this hose (wire size) is of sufficient size to carry the
supply of water (current) to the load. This all changes when we reduce the water hose (wire size) to one half inch as shown in the
second diagram. The hose (wire) can only deliver half the current needed by the load— this hose (wire) is NOT of sufficient size
to carry the needed supply of water (current) to the load.
Wiring is just as important as any other component in the starting and charging system. It must
be capable of delivering the amount of current that the load is demanding.