C&D Technologies RS-2061 Standby Batteries for Renewable Energy Applications - Manual (Page 12)

A complete description of capacity tests on lead acid batteries is beyond the scope of this manual but is
discussed in detail in current releases of IEEE STD 450 and IEEE 1188.
A full-load service test to be performed not more than once every twelve (12) months to verify battery capacity
at users originally specified discharge rate.
Battery Degradation
Properly maintained and charged lead-acid storage batteries should provide many years of trouble-free
service. However, despite their inherent dependability, failure to operate or maintain batteries correctly may
lead to damage, shortened life, possible loss of service and voiding the warranty. The following paragraphs
address some of the most frequently encountered problems.
Low Cell Voltages
With proper operation, at recommended voltages and individual cell temperatures varying not more than 5°F
(2.8°C), individual cell voltages of a battery at 100% state of charge should be within plus or minus 50mV of
the average cell voltage.
When the voltages of individual cells are lower than normal, it is logical to conclude that insufficient charging
has occurred. The following are possible causes:
• Panel voltmeter reading high. This results in a low system voltage. Recalibrate panel meter.
• Poor terminal connections. Remove connections, clean contact surfaces, neutralize with baking
soda solution, dry, coat with NO-OX-ID grease and reassemble.
• Impurities, such as metallic objects, inadvertently introduced into cell electrolyte.
Such contaminants dissolve in the electrolyte, increasing the rate of self-discharge. Unless the
amount of contaminant is very small, the affected cell or cells will require replacement.
Voltage Drop
IEEE 450 discusses the significance of connection integrity. Typically, a voltage drop between cells should
be 30mV or less, at rated current. Voltage drop between rows (inter-tray) is typically less than 100mV,
at rated current.
Electrolyte Stratification
A condition when the specific gravity of the electrolyte decreases from the bottom to the top of the container.
Stratification does not materially inhibit the ability of a lead-acid battery to deliver power. However, its capac-
ity will naturally be reduced from optimum value. Conducting an equalization charge can eliminate electrolyte
stratification.
Low System Voltage and Sulfation
If a battery is left in a partial state of discharge for extended periods, cell voltages may vary erratically. Re-
charging the battery fully and maintaining it on charge until the specific gravities of all cells stabilize over three
successive hourly measurements can reverse this. Conducting an equalize charge. Another method is
to repeat battery cycling several times until all cells are within ±0.005 of the recommended specific gravity.
In advanced cases, sulfate may be extremely difficult to reduce. C&D Technologies recommends that, in cases
of advanced sulfation, contact the C&D Technologies Technical Service Department for assistance.
RS02061/0514/CD 12 www.cdtechno.com