Toro VACU-POWER Service Manual page 69

Key-Lectric Starting System Operation (cont'd)
Figure 11 1
Battery: The battery is a six cell, lead acid, gel cell type.
It's capacity is 2.5 amp hours. Maximum draw under
normal starting conditions is 90 amps. Individual cells
are not available as soldering or welding on the battery
group is not recommended.
Starter Switch: The starter switch is closed when
rotated to the 'start' position. This allows current to flow
through the switch and to the starter motor.
Starter Motor: The starter is a direct current, permanent
magnet motor.
Alternator: The alternator's purpose is to charge the
battery.
It
is a magneto type alternator which means
that it generates electricity by passing a magnet by a
coil of wire. (Note: the coil of wire must form a complete
circuit.) When the magnet passes by the coil, current
flow is induced by the magnetic field.
The output of the coil is approximately 125 milliamps
at 14.5 volts. By itself, the alternator produces alter-
nating current. However, in this application, a diode
(one way Valve'), converts the alternating current to
direct current by a process called 'half wave
rectification'.
Half wave rectification can best be explained by means
of an illustration. See Figure 1 12.
Normal alternating current has a wave form as shown
in the figure. Notice that the voltage goes both positive
Electrical Systems
64
and negative. Because negative voltage would
damage the battery if used for charging, the diode
'removes' this portion of the wave so that it has the
waveform shown in Figure 11
5.
Notice, that although
the voltage still varies up and down, it never goes
negative. This arrangement allows charging of the
battery.
(HALF WAVE RECTIFIED)
CHARGER OUTPUT
Charger: An auxiliary charger is included with
Key-Lectric Vacu-Power Mowers in case the battery
discharges during storage. Using the charger allows
the battery to be recharged without running the
engine.
The output of the charger is 100 ma. at 14.5 volts DC.
While
it
is called DC, it pulses in the same fashion as
the alternator described above.
It
is important to note
that if measuring the voltage of the charger with an
analog (non-digital) meter, the voltage will appear low
due the pulsations. A normal reading from the charger
is
8.5
and
10.5
volts DC if the meter is set to read DC
voltage.
Key-Lectric Starting System Operation: When the
starter switch is 'off, the switch is open and current
cannot flow to the starter motor. However,
if
you
look
at
the schematic, you will see that current can flow from
the alternator to the battery. This charges the battery
during mowing.
When the starter switch is closed, current flows from
the battery and the alternator to energize the starter
motor. The battery supplies nearly all the current since
the alternator produces about 0.1 amp as compared
to the
90
amps produced by the battery during starting.
Key-Lectric Starting System Testing
Battery Testing:
Disconnect connector at battery and check battery
voltage with a volt/ohmmeter (VOM)
or
better yet, a
Vacu-Power Mower