Capacity And Testing; Low Cell Voltages - C&D Technologies LIBERTY 1000 Series Installation And Operating Instructions Manual

3.2 Capacity and testing

Batteries are rated in Ampere-hours or kiloWatts on their ability to
deliver a certain number of amperes or power, respectively, to the load
for a specified amount of time before cell voltages drop to a final
design potential. It is important to understand that the ampere-hour
capacity or kiloWatts of a cell or battery depends upon the rate at
which it is discharged. Consult C&D Technologies specification sheet
12-373 for the ratings of various cell types.
C&D Technologies lead-acid batteries and cells are designed for
optimum performance, either as short, high-rate or long, low-rate
discharge batteries. Short, high-rate discharge batteries are typically
discharged to lower end-potentials, such as 1.65 to 1.67 Volts per cell.
These voltages are not practical end potentials for long, low-rate
discharges that normally terminate at 1.75 Volts per cell or higher final
voltages.
It is also important to consider low ambient operating temperatures
when calculating required battery size. Low operating temperatures
will reduce available battery capacity approximately 0.5 percent
per degree F. Refer to Section 3.4 "Effects of Temperature" for
temperature compensation and additional information. To be valid,
a capacity test must be based upon:
• A fully charged battery and balanced cell potentials. This may
require an equalize charge or, in cases of sulfation, other action.
Consult the C&D Technologies Technical Service Department at the
address or telephone number shown on page 1 of this manual for
additional information.
• Battery must be at float voltage for at least 3-7 days. This is
especially important following an equalize charge in order to clear
gases developed at the surface of the plates.
• Temperature correction for cells tested at any temperature other
than 77°F (25°C).
• All connections are correct and at minimal resistance.
A complete description of capacity tests is beyond the scope of this
manual but is discussed in detail in IEEE 1188-1996 and other
professional society standards. These standards are applicable to
VRLA batteries similar to the Liberty Series 1000 batteries. It is
important to recognize that standby batteries/cells are designed
for emergency standby operation and excessive testing or
cycling of a battery can materially shorten the life of a battery.
C&D Technologies can supply batteries specifically designed for cycle
service. Consult your C&D Technologies representative or the
Technical Service Department located in Blue Bell, PA about testing
procedures and special service requirements.

3.3 Low cell voltages

With proper float operation at recommended voltages, individual cell
voltages should be within +/- 0.05 Volts of the average cell voltage for
Liberty Series 1000 batteries.
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