TM 5-3805-296-23-1
0004
ELECTRICAL SYSTEM
0004
Batteries
0004
Four 12V batteries located under the right front tread plate of the machine are standard equipment. The batteries
are connected in series and parallel to output 24V for starting, charging, and operation of the machine. Two
additional 12V batteries may be located at the front of the machine if it is equipped with the optional Arctic Starting
Aid. The arctic starting aid batteries are connected in series with each other and in parallel with the standard
equipment batteries to provide additional power for cold starts.
0004
CAUTION
Never operate the alternator without the batteries in the circuit. Making or breaking an
alternator connection with a heavy load on the circuit can cause damage to the regulator.
Failure to follow this caution may cause damage to the equipment.
The alternator is a 24V, internal regulator, self rectifying charging unit. The alternator is mounted on the front of the
engine and is driven by the accessory drive belt. When the engine is running, the alternator provides enough
current to run the machine's electrical systems and charge the batteries.
Starter
0004
This engine uses two starter motors to turn the engine. The transmission/chassis ECM will activate a starter relay
to energize the left and right starter motors when certain conditions are met. The transmission/chassis ECM moni-
tors the transmission shifter position, the park brake switch, and the ignition switch. If the transmission is in neutral,
the park brake is ON, and the ignition switch is in the START position, the transmission/chassis ECM will activate
the starter relay.
Solar Charger
0004
A solar panel is located on the hood of the Military 621G Scraper. The solar panel supplies up to 0.2 amps at 28V
in full sunlight. The solar charger is used to maintain battery state of charge when the machine is not in use. The
solar charger will pulse the batteries continuously, day and night, to offset parasitic drain on the batteries resulting
in increased battery life.
Electronic Control Modules
0004
The Military 621G Scraper has three electronic control modules (ECM's), a tractor operator monitor, an engine
ECM, and a transmission/chassis ECM. These modules operate with 24V, but may output lower or higher refer-
ence voltages to various sensors or solenoids on the machine. All three modules share a common data link which
allows for sharing of information between modules and for use of the electronic technician (ET) for diagnostics.
0004-5
