TM 9-6140-200-14
2-4 Operation Under Usual Conditions.
a. Keep your vehicle batteries at full charge. Automotive batteries are designed
with the expectation that equipment use will keep the batteries fully charged at
all times. Allowing the battery to discharge below 10.5 volts not only prevents it
from starting your equipment, but also causes damage that shortens battery life.
The more often you allow your batteries to go dead, the more likely it is they will
fail completely. In addition, sulfate from the acid becomes very difficult to
remove when left on the battery plates for months at a time, which decreases
the capacity of the battery. If your batteries are brought to full charge on a
regular basis, they will lose the ability to take a full charge and will fail
prematurely.
(1) Run the engine often enough to keep the battery charged. All batteries
slowly lose charge while the equipment is not running. Under normal
conditions, your equipment should be operated at least once every three
months to keep the battery near full charge. More often is batter, for both
the battery and the equipment. Failure to recharge the battery periodically
during long-term equipment storage will result in a battery that is dead and
damaged.
(2) Run the engine fast enough to charge the battery. At low idle, engine
electrical system will not generate enough voltage to charge the battery.
The typical engine must be run at speeds of 1000 to 1200 RPM to generate
enough voltage. This is equivalent to high idle, or a vehicle speed of 20
miles per hour or faster. Your equipment may be different, so check your
equipment manual to make sure these parameters are correct. Use of
lights, radios, or other accessories while idling the engine at low RPM will
discharge your battery; just the same as using them with the engine off.
(3) Run the engine long enough to bring the battery back to full charge. A
battery typically requires 20 to 30 minutes of charging to replace the power
used to start the engine. Numerous short periods of operation (less than 20
minutes at a time) will eventually discharge the battery, even if the engine is
operated at high speed. Extended operation at high idle is hard on most
engines. Refer to your equipment manual and local SOP before running
your equipment at high idle for extended periods.
2-2
