The primary disadvantage of constant current
charging is that THE CHARGING CURRENT
REMAINS AT A STEADY VALUE UNLESS YOU
CHANGE IT. A battery charged with too high current
rate would overheat and damage the plates, making the
battery useless. Do NOT allow the battery temperature
to exceed 110° while charging.
CONSTANT VOLTAGE CHARGING.
Constant voltage charging, also known as constant
potential charging, is usually done with a motor
generator set. The motor drives a generator (similar to
a generator on a vehicle); this generator produces
current to charge the battery. The voltage in this type of
system is usually held constant. With a constant
voltage, the charging rate to a low battery will be high.
But as the battery approaches full charge, the opposing
voltage of the battery goes up so it more strongly
opposes the charging current. This opposition to the
charging current indicates that a smaller charge is
needed. As the battery approaches full charge, the
charging voltage decreases. This condition decreases
the ability to maintain a charging current to the battery.
As a result, the charging current tapers off to a very low
value by the time the battery is fully charged. This
principle of operation is the same as that of the voltage
regulator on a vehicle.
CHARGING PRACTICES.It is easy to
connect the battery to the charger, turn the charging
current on, and, after a normal charging period, turn the
charging current off and remove the battery. Certain
precautions however are necessary both BEFORE and
DURING the charging period. These practices are as
1. Clean and inspect the battery thoroughly before
placing it on charge. Use a solution of baking
soda and water for cleaning; and inspect for
cracks or breaks in the container.
Do not permit the soda and water solution
to enter the cells. To do so would neutralize the
acid within the electrolyte.
2. Connect the battery to the charger. Be sure the
battery terminals are connected properly;
connect positive post to positive (+) terminal
and the negative post to negative (-) terminal.
The positive terminals of both battery and
charger are marked; those unmarked are
negative. The positive post of the battery is, in
most cases, slightly larger than the negative
post. Ensure all connections are tight.
See that the vent holes are clear and open. DO
NOT REMOVE BATTERY CARS DURING
CHARGING. This prevents acid from spraying
onto the top of the battery and keeps dirt out of
Check the electrolyte level before charging
begins and during charging. Add distilled water
if the level of electrolyte is below the top of the
Keep the charging room well ventilated. DO
NOT SMOKE NEAR BATTERIES BEING
CHARGED. Batteries on charge release
hydrogen gas. A small spark may cause an
Take frequent hydrometer readings of each cell
and record them. You can expect the specific
gravity to rise during the charge. If it does not
rise, remove the battery and dispose of it as per
local hazardous material disposal instruction.
Keep close watch for excessive gassing,
especially at the very beginning of the charge
when using the constant voltage method.
Reduce the charging current if excessive
gassing occurs. Some gassing is normal and
aids in remixing the electrolyte.
Do not remove a battery until it has been
Placing New Batteries in Service
New batteries may come to you full of electrolyte
and fully charged. In this case, all that is necessary is to
install the batteries properly in the piece of equipment.
Most batteries shipped to NCF units are received
charged and dry.
Charged and dry batteries will retain their state of
full charge indefinitely so long as moisture is not
allowed to enter the cells. Therefore, batteries should
be stored in a dry place. Moisture and air entering the
cells will allow the negative plates to oxidize. The
oxidation causes the battery to lose its charge.
To activate a dry battery, remove the restrictors
from the vents and remove the vent caps. Then fill all
the cells to the proper level with electrolyte. The best
results are obtained when the temperature of the
battery and electrolyte is within the range of 60°F to