In sub-freezing temperatures, water should be added
just
before charging is completed
to insure prompt mixing
with the electrolyte. Otherwise it may freeze on the surface
before mixing. No permanent harm results from low
temperature operation as long as freezing is avoided.
b. High temperatures have an adverse effect and all
practical means should be employed to keep the battery
temperature at normal values:
- Avoid overdischarging
- Charge in cool location
- Supply ample ventilation during charge by always opening
battery compartment or battery cover and circulating air by
fans if necessary
- Allow battery to cool down before starting charge.
The effect of temperature on battery life on any lead acid
truck battery is shown below.
AVERAGE LIFETIME BATTERY TEMPERATURE, °F
Figure 3 - Temperature vs. Battery Life Curve
EXAMPLE:
If the average lifetime temperature of the battery
is 100°F, it will result in a battery life of
approximately 53% as compared to 100% at
77°F.
12. DISCHARGE
CHARACTERISTICS
a. In general, a battery may be discharged without harm at
any rate of current it will deliver, but the discharge should not
be continued beyond the point where the cells approach
exhaustion, or where the voltage falls below a useful value.
b. Discharging at a constant current value, the initial voltage
will depend on the rate of discharge and the normal
characteristic of the cell. As the discharge continues, the cell
voltage will slowly decrease during the first 70 to 80 percent
of the total time period. It will then fall more rapidly, passing
over the “knee” of the curve to the “final” voltage as full time
and capacity are reached. This “knee” is more pronounced
at low rates of discharge.
c. During discharge there is normally a rise in battery
temperature, depending on the ambient temperature, on the
rate of discharge and the type of battery assembly from the
standpoint of heat dissipation. The higher the ampere dis-
charge rate, the greater the temperature rise effect. During
discharge, a battery’s temperature will normally rise. The
speed and magnitude of this temperature rise is dependent
on the following conditions:
- ambient temperatures
- battery design and layout,
- and battery discharger rate.
Batteries subject to high discharge rates will
incur higher temperature increases.
d. As mentioned, a battery should not be discharged beyond the
point where the cells approach exhaustion. This is
referred to as “overdischarging” and can have very harmful
results, particularly if repeated for several days or cycles.
Overdischarge can be avoided by using a lift interrupt device.
When installed on the vehicle, the lift interrupt device gives a
constant readout of battery condition and locks out the lift
mechanisms as the battery approaches 80% depth of discharge.
TABLE 3
SPECIFIC GRAVITIES @ 77°F
Cell Type
Fully Charged
80% Discharge*
100% Discharge*
E-55L
1.315
1.160
1.120
E-75L
1.315
1.160
1.120
E-75
1.280
1.160
1.130
E-460
1.280
1.140
1.105
E-85
1.280
1.150
1.120
E-85D
1.280
1.140
1.110
E-100
1.315
1.155
1.115
E-100X
1.280
1.130
1.090
E-110
1.315
1.155
1.115
E-100D
1.280
1.145
1.115
E-125
1.280
1.140
1.105
E-125D
1.280
1.130
1.100
E-140
1.280
1.140
1.105
E-140X
1.280
1.140
1.105
E-155
1.315
1.150
1.100
*
These values are for discharging at the 6 Hr. rate, read immediately
at the completion of the discharge and corrected to 77°F.
13. CHARGING EQUIPMENT
a. Battery charging should be accomplished with an
electronically controlled charger.
b. When the discharged battery is placed on charge, the
battery will draw a relatively high current which will be at or
close to the capacity of the charger. Within a few minutes,
the current will adapt itself to the state of discharge of the
battery, remaining high if the battery is considerably
discharged or decreasing to a low rate if the battery is only
partially discharged. The charging rate should be controlled by
a control unit.
c. When charging any industrial battery, only use an approved
charger that is capable of returning a discharged battery’s
specific gravity back to it’s nameplate rating within an 8 hour
period. Several chargers offered by EnerSys will accomplish
this requirement. Some charger technologies, such as
ferro-resonant, will not adequately charge and EnerSys
Ironclad tubular battery and will result in undercharging and
short life. Please consult an EnerSys representative for more
information.
d. Although a number of chargers meet the mentioned
general requirements above, not all chargers are equal.
Contact your local EnerSys representative for more details.
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