PS Magazine - TB 43-PS-590
PS, The Preventative Maintenance Monthly
ISSUE 590
JANUARY 2002
Color Counts
Watch the gauge when you turn the switch to
ON and before you crank up the engine. The
gauge needle should land in the yellow section,
or between 22-26 volts. If the needle goes into
the red section at the left of the gauge, your bat-
teries are weak, defective or need charging, or
there’s a short in the system.
Now, crank up the engine. If the needle hangs
to the left after you’ve started the engine, one
battery could have a bad cell.
After the engine starts, run it at fast idle—
about 1,500 rpm. The battery charging system is
working OK if the needle settles at about 28.5
volts, shown by the notch in the green section.
PS 590
Overcharging
Overcharging is the culprit when the
needle hangs in the red section on the right
side of the gauge.
Overcharging means that water will boil
out of the batteries and the plates inside can
be damaged. Another clue to overcharging
is a battery that often needs water.
If the gauge shows a high rate of charge
after the engine’s been running for 30 min-
utes, there’s a good chance the batteries are
being cooked to death.
Undercharging
Undercharging is the villain
when the needle settles well
below that 28.5-volt mark, even
though it’s still in the green.
If your BAT/GEN gauge
indicates any of these problems,
get your mechanic to check out
the charging system.
PS 590
M
ost Army vehicles have a BAT-GEN indicator to show you operators the condi-
tion of their batteries.
But you must know how to “read” that gauge so you can tip off your mechanic to
battery trouble before you get stranded in the boonies.
Here’s how:
Turn off all electrical components. Then it’s just the batteries and your alterna-
tor/generator showing up on the gauge.
This is
OVERCHARGING
Red: 30-34 volts
This is
UNDERCHARGING
Green: 26-30 volts
over-
charging!
that
burns
me up!
under-
charging?
No wonder
I feel
run
down!
Charge is OK to start engine
Yellow: 22-26 volts
Correct charging is about 28.5 volts
Green: 26-30 volts
7
JAN 02
6
Lead-Acid Batteries…
590. 06-07 (C)
11/23/01
3:45 PM
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