TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
charging starts to limit current flow. Battery charg-
tenance of these devices should be as recommended
ers are designed to limit charging currents to values
by the manufacturer. Included in the category of
that keep the charging equipment within a reason-
accessories are meters, equalizing control, indicat-
able size and cost. Battery chargers must also main-
ing lamps, dc voltage level alarm, ground detection
tain a sufficiently high current throughout charg-
alarm, and electrolyte level alarm. Meters and indi-
ing, so that at least 95 percent of the complete
cating lamps should be connected to the load side of
storage capacity is replaced within an acceptable
the circuit breakers on the circuit being monitored.
time period. This recharge time is usually not more
Connections on the line side can give a false indica-
than 8 hours for station service.
tion of power availability.
b. Charging equipment. Batteries must be
a. Equalizing control. Equalizing control should
charged by direct-current. The available sources are
include a manual switch for transferring the lower-
an ac-to-dc rectifier and an ac-to-dc motor-generator
rate float charge to the higher-rate equalize charge.
set. The use of motor-generator sets to supply sta-
Optional accessories include equalizing timers and
tion batteries is an unusual practice now because
automatically-controlled equalizing timing for ad-
the function is so reliably and economically handled
justable interval settings.
by rectifier type battery chargers. If motor-
(b) Input and output. Input and output circuits
generator sets are used, maintenance should be in
are always provided with protection. Fuses are
accordance with the manufacturer's instructions.
standard accessories. Circuit breakers are optional,
14-21. Rectifier type battery chargers.
but are a preferred means of isolating the battery
charger for maintenance.
There are several types of rectifiers used for battery
charging. All operate on the same principle permit-
14-23. Maintenance of battery chargers.
ting current to pass freely in one direction, while
Battery chargers are designed to require a mini-
permitting little, if any, current to flow in the re-
mum of maintenance. There are no rotating parts,
verse direction. Refer to manufacturer's instruc-
except in the optional timer, and all components
tions for details of each type.
normally have an indefinite life and no aging ef-
a. Silicon-controlled rectifier (SCR) type. This
fects. However, it is possible for a diode or rectifying
type uses silicon diodes to provide the rectification
stack to fail at long intervals, either by open-
of ac voltage input to dc voltage output. Units may
circuiting or short-circuiting. Failed items should be
include transistor-controlled magnetic amplifiers. If
replaced in accordance with the manufacturer's in-
not filtered, units can cause electromagnetic inter-
structions. Battery chargers should be kept clean,
dry, and checked periodically to make sure all con-
(RFI). A properly filtered unit will eliminate this
nections are tight. If necessary, dry air may be used
problem. However, the filter capacitor may take sev-
to blow dust out of the interior. In the event of any
eral minutes to discharge, even after isolation of the
irregular operation, examine and tighten, if neces-
battery charger from the ac input and the battery.
sary, all internal and external connections and
This feature should be noted by a warning label on
check circuits for continuity. If the difficulty cannot
the battery charger.
be remedied, contact the manufacturer.
b. Controlled ferro-resonant type. This is an im-
a. Checking. Regardless of the quality of the bat-
proved version of the simple ferro-resonant type,
tery charger, its operation should be checked, at the
which was the first static battery charger devel-
same time as its battery is inspected, to ensure that
oped, and which used a constant voltage trans-
it is functioning properly. Any radical trouble will be
former and selenium stacks. The simple ferro-
indicated by overheated components on either the
resonant type was quieter and much easier to use
battery charger or the battery installation, by blown
than a motor-generator, but had serious control
fuses, or by failure to complete the charge. In such
shortcomings. The controlled ferro-resonant type in-
cases the trouble must be located and remedied.
cludes a control winding, a triac, and a control cir-
Certain adjustments may gradually "drift" from
cuit to overcome these problems. It is very impor-
their normal position and require correction. At
tant for personnel to distinguish between "simple"
each monthly inspection provide recorded checks on
ferro-resonant units and "controlled" ferro-resonant
the following data:
units to be sure that the dual-rate (float/equalize)
requirement for battery charging is acceptable.
(1) Check the voltage of battery chargers in
14-22. Accessories for battery chargers.
(2) Check the current output and/or voltage of
Dependent upon the specific unit, battery chargers
battery chargers in cycle operation, during normal
will be provided with various accessories. The main-