14. CHARGING
CHARACTERISTICS
a. Only EnerSys approved charging methods should be
used. To maximize life, charging should not result in
excessive gassing during the initial stages of charge. In
addition, the charging method should keep end-of-charge
temperature below 110˚F.
b. Every effort should be made to ensure that the battery
receives the proper amount of charge. Consistent undercharge
and/or excessive overcharge will contribute to internal battery
problems with a loss of capacity and reduction of life.
c. 1. Sulfation - Residual sulfation remains in the plates
if the battery is not fully charged to nameplate specific
gravity or allowed to remain partially discharged for an
extended period of time. This results in reduced
performance and life. All motive power batteries must be
returned to nameplate specific gravity at least once per
week. However, more frequent recharges to nameplate
specific gravity is desirable.
2. Stratification - Caused by insufficient gassing at end of
charge. Little or no mixing of electrolyte will thus create a
higher concentration of electrolyte at the bottom of the cell
compared to the top. This will eventually lead to sulfation
of the bottom of the negative plate with subsequent fall off
of performance and capacity.
d. Overcharge
1. It is uneconomical from a power standpoint and wastes
electrical energy while running the risk of permanent dam-
age to the battery.
2. Excessive gassing, producing hydrogen and oxygen,
not only increases the frequency of water additions to
the battery but also increases an explosion hazard
significantly over normal and safe charge conditions.
3. It creates dangerously high battery temperature which
significantly shortens normal battery life if repeated
instances occur above 110°F. (See Figure 3 in Section 11.)
Higher temperatures, that is 15-20°F above the maximum
allowable temperature at the start of the charge, tend to
reduce the battery voltage on charge permitting higher
current flow from the charger and further raising the cell
temperatures. Battery temperature at the end of charge
should not exceed 110°F. To assure this, batteries should
not be put on charge above 90°F.
Should excessive battery temperature occur with some
frequency, contact the EnerSys Service Center nearest
you (see back page) for an analysis of its cause and
charger output adjustment, if necessary.
4. Unless charging under an opportunity or fast charging
method as described in Section 9 of this manual, make
sure the battery is not being charged more then once per
day. When the battery reaches full charge, the charge
should be stopped. No amount of overcharging can
increase battery capacity.
e. When charging batteries while they are in the vehicle,
assure proper ventilation and follow the manufacturers
instructions. Open the battery cover, if so equipped, as well as
the battery compartment cover of the vehicle. Not following these
recommendations can cause gaspockets to remain in the vehicle
or battery giving rise to possible explosions when the vehicle is
put into use.
f. Extra care spent in proper charging is effort well worth it in
trouble free battery performance, reduced maintenance and long
battery life. For information regarding charging room
layouts, refer to EnerSys Form 8041.
g. Equalizing charge. It is necessary that a battery be brought
to a state of full charge in order to avoid excess sulfation, yet
appreciable overcharge must also be avoided.
1. Light Depth of discharge (50% or less) equalize bi-weekly.
2. Medium Depth of discharge (60%) equalize weekly and
recharge every 48 hours.
3. Heavy Depth of discharge (80% or greater) or battery
temperature exceeding 100°F equalize weekly, but allow
sufficient time for battery temperature to drop below 100°F.
15. MAINTENANCE AND
RECORDS
Specific records should be maintained for each battery in
your fleet. These records will provide a means of identifying
batteries which may need repair adjustment, charger
problem or which have reached the end of their useful life.
Such records also help assure
warranty protection
. To assist
your record keeping, EnerSys has developed Form 5847
(see sample on page 16 of this manual). You may copy
Form 5847 to establish your own “Battery Log Book.”
a. Where more than several batteries are in use, each one
should be identified with a permanent number assigned
when received. That number should be plainly painted or
stamped on the battery. If a large number of batteries are
involved, including several sizes or types, various groups can
be given prefixes or suffixes to identify size, voltage or shift.
b. After each battery is received and equalized, record the
corrected specific gravity of each cell. This serves as
reference for comparison with later readings.
c. In a new application the depth of discharge should be
checked for several weeks to determine whether it is within a
safe range. This is done by reading the specific gravity of a
particular cell (or cells) at the beginning and end of the
discharge. This daily discharge should not exceed 80% (see
Table 3). If final corrected specific gravity is below 80%, there
is a problem. Call your vehicle dealer or local EnerSys
representative. The “pilot cell(s)” used for such purposes
should be changed at monthly intervals, as frequent
hydrometer readings may noticeably reduce their specific
gravity through inadvertent losses.
d. While the record sheet can accommodate daily specific
gravity readings for up to a month, EnerSys recommends
quarterly specific gravity readings once the duty cycle and
depth of discharge meet the criteria contained herein. When a
gravity reading indicates an irregularity, then more frequent
readings can be initiated. The final determination for frequence
of hydrometer readings should depend on your past
experience and advice from your local EnerSys representative.
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