TM 116140203141
d. Pulse Charging. Several types of automatic
high rates with automatic pulse or constant current
charging equipment are available which provide the
charging equipment, since the voltage level required
charging current in the form of high current pulses in-
to reduce the charging current is not reached. This can
terspersed with periods of no current or discharge. In
result in overheating of the batteries and spewage of
general, these charges function in the same manner as
electrolyte out of the cell vents. It is recommended
automatic constant current types, in that the current
that new batteries be charged at a current no higher
level is reduced when the battery voltage rises to pro-
than the 2-hour rate for the first cycle and the charge
vide a controlled overcharge. Because of the nature of
should be continued until the voltage reaches at least
the pulse charge and the automatic controls employed,
1.50 volts per cell. When charging a new battery, the
it is usually possible to charge at very high rates.
voltages of all the individual cells should be checked
Charge time of 1 hour is typical. One type of charge
periodically for either very high or low values.
analyzer that can charge 24-volt batteries in 1 hour is
f. Standby or Trickle Charging. Because the self-dis-
the AN/USM-432. Figure 2-8 gives its front panel
charge of a nickel-cadmium battery is approximately
layout.
1.2 percent per day at normal temperatures, standby
charging is required to maintain its full rated capacity.
e. Charging of New or Unformed Batteries. Bat-
For standby charging in the temperature range of
teries which have never been cycled have a different
60F to 90F, use a current equal to 3 ma per ampere-
charge voltage characteristic than used batteries. This
hour rated capacity or a constant potential of
occurs because the cadmium electrode in a new battery
1.35V/cell. Batteries on standby charge must be regu-
may have a large excess of uncharged cadmium oxide
larly checked to ensure adequate electrolyte level.
which must be formed by overcharging. Thus, the
sharp voltage rise seen in figure 2-7 does not occur
during the first cycle. Up to 150 percent overcharge
Charge efficiency is the ratio of ampere-hours avail-
may be required to reach full charge. Because of this
able on discharge to ampere-hours returned to a bat-
condition, care must be taken when charging at very
