INTRODUCTION TO THE HMMWV - OD1615 - LESSON 4/TASK 1
2.
Electrical System
The HMMWV electrical system is a 24 volt system capable of submerged
operation during fresh or saltwater fording. It provides for starting the
vehicle, charging the batteries, and operating the controls, gages, and
accessory items peculiar to this vehicle.
In the paragraphs that follow, the components that comprise the electrical
system on the HMMWV will be discussed. The electrical system on the HMMWV
consists of 15 components as follows:
batteries, alternator, starter,
wiring harness, protective control box, circuit breakers, instruments,
gages, indicators, lights, horn, windshield wiper/washer, heater/defroster,
slave receptacle, and trailer receptacle.
a. Batteries. Two 12 volt batteries are connected in series to supply
the 24 volt current required to start and operate the engine and lights.
The batteries are mounted in an enclosed compartment under the right front
crew seat. They are secured by a holddown clamp. The batteries are joined
by a negative to positive jumper cable. The remaining negative terminal is
connected to the vehicle ground, while the other positive terminal is
connected to the vehicle starter. The batteries supply the necessary power
to the starter through the circuit designated SA in TM 9-2320-280-20. This
circuit connects the batteries and the starter, however, it is also
connected to the power control box (PCB), which will be discussed later in
this text.
b. Alternator.
Most military vehicles are now equipped with
an
alternating current (ac) charging system. The reason for changing to the
ac
system is that an alternator is capable of producing a higher voltage
at
idle speed. Alternators convert mechanical energy to electrical energy
to
power the vehicle.
Many military vehicles are equipped with radios, firing devices, and other
high-current-drawing equipment. When this equipment is in operation and the
vehicle's engine is operating at a low rpm, a dc generator will not produce
the current and voltage required to keep the batteries charged, plus supply
the current required to operate the accessories properly.
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