C&D Technologies RS-1476 Standby Battery Vented Cell - Manual (Page 19)

Additional deep and/or frequent discharges can shorten service life, even with proper maintenance and
operation. This section will consider batteries that are used in full float service. They will not be exposed to
service in which the standby power system is not capable of supporting peak loads. In such cases the battery
would be exposed to numerous partial discharges. In float service, the charger voltage is regulated and filtered
and the battery is operated in a temperature controlled environment.
For optimal service, adjust the chargers to the recommended float voltages shown in Table 5. See Part 4,
Section 1.3 for temperature correction factors. If more frequent discharges are anticipated, use a higher float
voltage setting. Operating within these criteria will maximize battery service life.
Equalize charges are used to bring cell voltages into a narrower operating range, or to assure full state of charge
before a discharge performance test. An equalizing charge may be required at a voltage higher than the nominal
float voltage to restore proper voltage to a battery which has:
• been subjected to frequent discharges, resulting in a partial state of charge condition
• been charged at less than minimum float voltage, resulting in an undercharged condition
An equalizing charge should be given when the lowest cell voltage reaches the minimum allowable cell voltage
shown in Table 6. Please note that antimony cells require regular equalization, while lead-calcium cells should
be equalized when a cell reaches a low voltage limit.
4.2 Equalize charge
As noted above, equalize charges are used to narrow the overall voltage spread of a battery system. Equalize
charges are needed on a regular basis for lead antimony cells, and on an as-needed basis for lead calcium cells.
Minimum allowable cell voltage is the point at which arrangements should be made to provide an equalizing
charge. It does not imply the battery is malfunctioning or will not provide power if called upon. The ability to
perform an equalize charge on a system will depend on the maximum voltage capability for the system. Lower
equalize voltages require longer equalize time, and higher voltages require shorter times. Consult the supplier of
the charging equipment if the maximum voltage capability of the system is not known.
*The longer equalization time is to be used for the lower equalization voltage; the shorter equalization time is to be used for the higher
equalization voltage.
Terminating Equalize Charge: The duration of an equalize charge for lead calcium batteries will depend on
various factors, including the local battery environment, the conditions causing the need for equalization, the
total voltage variability within the system, and the length of time that the low cell voltage condition persisted.
Terminating the charge will depend on the voltage rise of the low cell and the stability of the voltage in the
lowest cell. Start measuring the voltage of the lowest cell in the system eight hours after initiation of the equalize
charge. The equalization can be terminated after 24 hours when the lowest voltage cell is within 0.05 V of the
string average (in volts per cell) AND the voltage has not changed for three consecutive hourly readings and the
charging current is stable. If these conditions are not reached within 2 days of charge initiation please contact
your C&D representative.
LEAD-CALCIUM CELLS
PART 2
CHARGING AND OPERATION OF BATTERY (CONTINUED)
Nominal Specific Gravity
(See Part 4, Sec. 1.3)
Interval
Equalize
Voltage per Cell (VPC)
Duration
1.215
Equalize at minimum
3 month intervals or if
voltage drops below 2.12 or
gravity drops below 1.200
2.33 8-24 Hours
Nominal Specific Gravity
(See Part 4, Sec. 1.3)
Equalize When Lowest
Cell in String Reaches
Equalize Voltage per Cell Duration*
1.215 2.12 2.33-2.38
48-24 Hours 1.250 2.15 2.38-2.43
1.300 2.23 2.45-2.50
Table 6 - Equalize Charge Voltages
LEAD-ANTIMONY CELLS
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