C&D Technologies RS-1476 Standby Battery Vented Cell - Manual (Page 23)

PART 4
REFERENCE INFORMATION, TROUBLE SHOOTING & EXTENDED MAINTENANCE
SECTION 1 - REFERENCE INFORMATION
A battery used in full float service that has been properly installed and not subjected to frequent discharges and
recharges, floated at the recommended charging voltages and maintained in accordance with recommended practices
will require minimal attention. This is particularly true for lead calcium alloy batteries. Lead antimony batteries will
require more frequent watering and equalizing charges as they age.
1.1 Battery voltage measurements and equipment voltmeter calibration
Battery voltage measurements must be taken at the battery terminals, not at the attached equipment. The voltmeter
should be a digital type with at least 3 1/2 digits display with an accuracy better than 0.25%.
When the battery is not subject to any discharge, but merely in full float operation the battery terminal voltage should
be close to the meter reading on the attached equipment. If this is not the case, check the voltmeter(s) for errors and
have them calibrated by a certified testing laboratory.
This practice can avoid charging the battery at incorrect voltages that may be too high thereby causing premature
aging and short life. Charging at a voltage lower than specified will result in damage to cell plates or electrodes that
can reduce available capacity when the battery is called upon for support or a scheduled capacity test.
1.2 Constant current charging
Although constant potential charging is more common, another method of charging a battery which may be used in
some applications is one in which the battery receives its charge from a charger having a constant current control.
Under this method, the voltage will rise to any value consistent with the current (a pre-adjusted value). Usually, the
current is adjusted to 2.0-2.5 amperes per 100 ampere-hours of battery eight-hour rating. Note: This type of charging
is only to be employed for the initial charge, or recharge after a performance test.
For example, a 1200 ampere-hour cell may be charged at 24 to 30 amperes for a prescribed time, which typically
does not exceed 48 hours. One method for determining if a battery is fully charged is to monitor the voltage and
specific gravity of selected cells three times for three successive hours. When these values cease to increase between
readings, you can be sure that the battery is fully charged. A slight increase in cell temperature may cause readings
to vary slightly. In no event should cell temperature be allowed to exceed 120°F (49°C). If cell temperature(s) should
approach this level, reduce the charging current or immediately remove charger.
1.3 Specific gravity, effects of temperature, electrolyte level and recharge
The nominal specific gravity of a cell is specified at 77°F (25°C) when fully charged,
with the electrolyte fully mixed and between the high and low lines. Under these
conditions the variation from nominal should be +0.010/-0.005 or less. If these
conditions are not met there will be variations in the measurements which will exceed
the previously stated tolerances from nominal. Variation from the midpoint of the level
lines can affect the specified range by an additional +/-0.012, or more depending, on
the levels and battery design. Variation in readings may have many causes unrelated
to battery condition, including stratification, need for watering, recent water addition, or
less than full state of charge.
RS1476/0215/CD 21 www.cdtechno.com
PART 3
DRY-CHARGED BATTERIES, PREPARATION & CHARGING
NOTE: Please refer to RS02208 for dry-charge batteries, preparation and charging.
Effect of temperature
Electrolyte temperature above 77°F (25°C) will result in a lower observed specific gravity reading approximately equal
to a loss of 1 point (0.001) for each 3°F (1.67°C). In contrast electrolyte below 77°F (25°C) will read approximately 1
point (0.001) higher for each 3°F (1.67°C). Higher temperatures expand the volume of electrolyte which reduces the
observed specific gravity, while lower temperatures condense the electrolyte and thereby concentrate the electrolyte.
The lead acid battery is an electrochemical device. Heat accelerates chemical activity; cold slows it down. Normal
battery operating temperature is considered to be 77°F (25°C). Higher-than-normal temperature has the following
effects on a lead acid battery:
• Shortens life
• Increases performance
• Increases internal discharge or local action losses
Acceptable Specific Gravity
Nominal 1.215 1.250 1.300
Minimum 1.200 1.215 1.285
Maximum 1.240 1.275 1.325
Note: It is anticipated that the maximum
specific gravities will occur near the low
level line.
• Lowers cell voltage for a given charge current
• Raises charging current for a given charge voltage
• Increases water usage
• Increases maintenance requirements