10.11 Charging Circuit - JLG sky trak mmv Service Manual

10.11 CHARGING CIRCUIT

The purpose of the charging circuit is to maintain battery
voltage between 13.8 and 14.2 volts. The ignition switch
must be in the RUN position with the engine running for
the charging system to operate.
The charging circuit consists of the battery and a belt-
driven alternator with an internal voltage regulator. These
components work together to provide electrical power for
the vehicle, including the starting system, operator's dis-
play panel, horn, solenoids, back-up alarm, joystick, logic
panel and all accessories.
Current flows from the positive post of the battery to the
BATT terminal on the starter motor.
When the ignition switch is in the RUN position, excitation
and the alternator begins emitting a charge. Current flows
from the alternator B+ terminal to the starter motor B ter-
minal, then through the positive (+) battery cable to the
battery. The circuit in the instrument panel connects to
the battery positive terminal through the fuse panel and
detects field voltages in excess of 16 volts or system volt-
ages that is less than 2-4 volts below battery voltage.
Either of these conditions will cause the warning light in
the operator's display panel to illuminate.
The warning indicator (14), a battery-shaped icon on the
operator's display panel, illuminates for three seconds
when the engine is started and will remain illuminated if
the engine is not running. The warning indicator illumi-
nates when the battery is at a low state of charge, and
when the alternator is no longer able to charge the bat-
tery.
Model MMV Rev. 12/04
The negative (-) post of the battery (4) is connected to the
main chassis ground, a stud located on a weldment at the
hydraulic reservoir. Other ground leads routed directly
from the main chassis ground are provided to the alterna-
tor, fuel shutoff switch, maintenance reset switch and
spliced within the wiring harness to other electrical sys-
tem grounds.
The alternator includes an internal voltage regulator that
limits alternator voltage to a pre-set value and helps pre-
vent circuit overloads, power surges, etc. during peak-
voltage output.
Beyond inspecting the fan belt every 1,000 hours of en-
gine operation, there is no periodic maintenance required
for the charging circuit. When inspecting the fan belt, also
check the electrical wiring and connectors.
Under normal conditions the alternator will have no prob-
lem keeping the battery charged. The only condition in
which the battery may cause a problem is when it has
been completely discharged for an extended period of
time. In this condition, the alternator may be unable to re-
charge the battery, and a battery charger will be required
for recharging.
Electrical System
14
MM1971
10.91