Cub Cadet CC 500 BAT - Manual (Page 8)

ELECTRICAL SYSTEM
4
Kirchhoff’s current law
Kirchhoff’s current law deals with nodes. Nodes are the
junction of two or more wires or the junction of a wire to
a component.
Kirchhoff’s current law states that what ever current
goes into a node must come out.
As an example: Three wires are connected with a wire
nut. one wire has 5 amps going into the wire nut. The
sum of the current coming out of the other two wires
must equal 5 amps. That could be 3 amps in one wire
and 2 amps in the other or it could be 2.5 amps in each
wire, but the total must be the same as the current
coming in. See Figure 2.2.
Kirchhoff’s voltage law
Kirchhoff’s voltage law deals with voltage drops. A volt-
age drop is the amount of voltage used up or “dropped”
by a resistance in the circuit. Ohm’s law stated that V =
IxR, every component in a circuit has resistance, even
the wires. To push current through a resistance, it takes
voltage. Kirchhoff’s voltage law states that the sum of
all the voltage drops equals the source voltage.
An example: a circuit has a battery of 12V, a light bulb
that creates 3 ohms of resistance and there is 4 amps
of current in the circuit. The wires are assumed to have
0 ohms, if the proper size wire is used and there is no
corrosion in the wire, the resistance will be too small to
worry about. The light bulb uses 12 volts (4 amps x 3
ohms = 12 volts). the battery has 12 volts that equals
the 12 volts used by the light bulb.
How the system is wired together
All circuits have some basic rules that must be fol-
lowed:
1. All circuits must have at least one voltage
source. It is could be a battery, an altenator or
both.
2. All circuits must have a load. To make a circuit
with out a load is the same as shorting out the
power source. A load could be:
• light
• motor
• resistor
• starter
• etc....
3. All circuits must have a complete path back to
the voltage source. This is also known as having
continuity.
NOTE: On outdoor power equipment, the frame
of the machine is used as the return path to the
battery. This is referred to as grounding the
machine. Any point on the frame should be the
same as the negative post of the battery (Electri-
cally), unless there is a bad connection between
the battery and the frame.
4. Most circuits have additional components like
switches and fuses.
Equipment needed to diagnosis an electrical system:
• Digital volt ohm meter
• Wiring or a schematic diagram.
Equipment that may be useful:
• Fused jumper wires.
• Hand tools to gain access to components.
• Flash light.
CAUTION: A test light can not be used on this
mower. The system voltage is 48 volts. It will
destroy the test light and may result in injury to
the technician.
Figure 2.2
5 Amps
3 Amps
2 Amps
Node