24VDC ELECTRIC SUPPLY SYSTEM
ELECTRICAL SYSTEM DESCRIPTION
The Komatsu truck utilizes a 24VDC electrical system
which supplies power for engine starting circuits and
most non-propulsion electrical components. The
24VDC engine starting circuit is supplied by four, heavy
duty Type 8D, 12 volt storage batteries. Several com-
ponents require 12VDC and are supplied by circuits
tapped off the starting batteries. Two, smaller, 12VDC
batteries (Type 4D) supply 24VDC for the non-propul-
sion components; Engine Control System, circuit re-
lays, indicator lamps, etc.
The batteries are of the lead-acid type, each containing
six 2-volt cells. With the engine “Off”, power is supplied
by batteries. During engine cranking, power is supplied
by the four engine cranking batteries only. When the
engine is running, power is supplied by an engine
driven high capacity alternator.
Lead-acid storage batteries contain sulphuric acid,
which if handled improperly may cause serious
burns on skin or other serious injuries to person-
nel. Wear protective gloves, aprons and eye pro-
tection when handling and servicing lead–acid
storage batteries. See the precautions in Section
“A” of this manual to insure proper handling of
batteries and accidents involving sulphuric acid.
During operation, the storage batteries function as an
electrochemical device for converting chemical energy
into the electrical energy required for operating the
accessories when the engine is shut down.
BATTERIES
Maintenance and Service
The electrolyte level of each cell should be checked at
the interval specified in the Lubrication and Service
Section “P”, and water added if necessary. The proper
level to maintain is
3
⁄
8
–
1
⁄
2
in. (10-13 mm) above the
plates. To insure maximum battery life, use only dis-
tilled water or water recommended by the battery
manufacturer. After adding water in freezing weather,
operate the engine for at least 30 minutes to thoroughly
mix the electrolyte.
DO NOT SMOKE or allow flame around a dead
battery or during the recharging operation. The
expelled gas from a dead cell is extremely explo-
sive.
Excessive consumption of water indicates leakage or
overcharging. Normal water usage for a unit operating
eight hours per day is about one to two ounces per cell
per month. For heavy duty operation (24 hour) normal
consumption should run about one to two ounces per
cell per week. Any appreciable increase over these
figures should be considered a danger signal.
Troubleshooting
Two most common troubles that occur in the charging
system are undercharging and overcharging of the
truck’s batteries.
An undercharged battery is incapable of providing
sufficient power to the truck’s electrical system.
Some possible causes for an undercharged battery
are:
Sulfated battery plates
Loose or corroded battery connections
Defective wire in electrical system
Loose alternator drive belt
A defective alternator
Overcharging, which causes overheating, is first indi-
cated by excessive use of water. If allowed to continue,
cell covers will push up at the positive ends and in
extreme cases the battery container will become dis-
torted and cracked.
Leakage can be detected by continual wetness of the
battery or excessive corrosion of the terminals, battery
carrier and surrounding area. (A slight amount of cor-
rosion is normal in lead–acid batteries). Inspect the
case, covers and sealing compound for holes, cracks
or other signs of leakage. Check battery hold down
connections to make sure the tension is not great
enough to crack the battery, or loose enough to allow
vibration to open the seams. A leaking battery should
be replaced.
D02018 24VDC Electric Supply System D2-1
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