Exide Technologies Section 92.61 - Manual (Page 22)

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C. Proceed to Step 3.
STEP 3
The initial charge is complete. Charger voltage can now be
reduced to float voltage setting per Section 12.2. For a target
float charge of 2.25 VPC on a 24-cell system, you would set
the charger voltage to 54 volts.
SECTION 12
12.0 Operation
12.0.1 Cycle Method of Operation
In cycle operation, the degree of discharge will vary for dif-
ferent applications. Therefore, the frequency of recharging
and the amount of charge necessary will vary. The amount
of charge necessary depends on the number of ampere
hours discharged. Generally, Absolyte GP cells require
approximately 105-110% of the ampere-hours removed to be
returned to achieve a full state of charge.
The upper voltage settings recommended, given that the
maxium charge current is 5% of the nominal C
100
Amp-hour
rating and ambient temperatures of 25°C (77°F), are as fol-
lows:
2.28 ± 0.02 VPC @ 0-2% DOD
2.33 ± 0.02 VPC @ 3-5% DOD
2.38 ± 0.02 VPC @ >5% DOD
Due to the variety of applications and charging equipment
(particularly in Photovoltaic systems) it is recommended that
you contact an GNB representative when determining proper
recharge profiles.
12.1 Floating Charge Method
In this type of operation, the battery is connected in parallel
with a constant voltage charger and the critical load circuits.
The charger should be capable of maintaining the required
constant voltage at battery terminals and also supply a nor-
mal connected load where applicable. This sustains the bat-
tery in a fully charged condition and also makes it available
to assume the emergency power requirements in the event of
an AC power interruption or charger failure.
12.2 Float Charge - Float Voltages
Following are the float voltage ranges recommended for the
Absolyte Battery System. Select any “volts per cell” (VPC)
value within the range listed that will result in the series string
having an average volts per cell equal to that value.
RECOMMENDED FLOAT RANGE (@77°F)
2.23 to 2.27 VPC
NOTE: Recommended float voltages are for 77°F. For other
temperatures a compensation factor of .003 V/°F (.0055 V/°C)
per cell is recommended. The minimum voltage is 2.20 VPC,
temperature correction does not apply below this voltage. The
maximum voltage is 2.35 VPC, temperature correction does not
apply above this voltage.
TEMPERATURE CORRECTION
V corrected = V25°C - (( T actual-25°C) x ( .0055V/°C)) or
V corrected = V77°F - ((T actual-77°F) x (.003V/°F))
See Appendix A for standard values.
Modern constant voltage output charging equipment is recom-
mended for the floating charger method of operation of GNB
Absolyte batteries. This type of charger, properly adjusted to the
recommended float voltages and following recommended surveil-
lance procedures, will assist in obtaining consistent serviceability
and optimum life.
After the battery has been given its initial charge (refer to
Section 11), the charger should be adjusted to provide the
recommended float voltages at the battery terminals.
Do not use float voltages higher or lower than those recom-
mended. Reduced capacity or battery life will result.
Check and record battery terminal voltage on a regular
basis. Monthly checks are recommended. See Section 15.0,
Records, second bullet. If battery float voltage is above or
below the correct value, adjust charger to provide proper volt-
age as measured at the battery terminals.
12.3 Voltmeter Calibration
Panel and portable voltmeters used to indicate battery float
voltages should be accurate at the operating voltage value.
The same holds true for portable meters used to read indi-
vidual cell voltages. These meters should be checked against
a standard every six months and calibrated when necessary.
12.4 Recharge
All batteries should be recharged as soon as possible follow-
ing a discharge with constant voltage chargers. However, to
recharge in the shortest period of time, raise the charger out-
put voltage to the highest value which the connected system
will permit. Do not exceed the voltages and times listed in
Table C, Section 13.2.
12.5 Determining State-of-Charge
If the normal connected load is constant (no emergency load
connected), the following method can be used to determine
the approximate state-of-charge of the battery. The state-of-
charge can be identified to some degree by the amount of
charging current going to the battery. When initially placed
on charge or recharge following a discharge, the charging
current, read at the charger ammeter, will be a combination
of the load current plus the current necessary to charge the
battery. The current to the battery will start to decrease and
will finally stabilize when the battery becomes fully charged.
If the current level remains constant for three consecutive
hours, then this reflects a state-of-charge of approximately 95
to 98%. For most requirements, the battery is ready for use.
If the normal connected load is variable (i.e. telecommunica-
tions), the following method may be used to check the state-
of-charge of the battery. Measure the voltage across a pilot
cell (See Section 14.0 for definition of pilot cell). If the voltage
is stable for 24 consecutive hours, the battery reflects a state
of charge of approximately 95%.