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9.2.5 Recharge interval
In order to prevent permanent damage to the battery, it is
recommended that recharge should be commenced immediately
after any discharge.
9.3 General
9.3.1 Discharge voltage
The minimum average voltage per cell should not fall below
1.60Vpc for a period of greater than 2 minutes on batteries
designed to give up to one hour standby period and for greater
than 5 minutes for standby periods in excess of one hour.
It is recommended that a low voltage disconnect feature be
included in the system to ensure compliance with the above
recommendation.
NB: A momentary dip in voltage below 1.60Vpc such as would
occur in switchgear closing operation or engine starting
applications is not considered detrimental.
9.3.2 Short circuit faults
Any short circuit fault should be cleared from the battery within
10 seconds.
9.3.3 Number of cells connected in series
The number of cells in series (N) will not affect the selected float
voltage per cell. Therefore, battery charging float voltage = N x
Cell Float Voltage. No special circuit arrangements are required.
9.3.4 Number of cells or cell strings connected in parallel
Under constant voltage charge conditions no special
arrangements have to be made for batteries in parallel.
However, where the parallel connection is made at the charger
or distribution board, the resistance between the battery terminal
and the common charge supply point must be within ±5% of the
mean value to avoid out of step conditions developing.
10. Maintenance
Routine maintenance of a battery is essential for ensuring
satisfactory performance. Good records will identify when
corrective action may be necessary to ensure the integrity of
emergency supply.
In practice, the content and frequency of a battery maintenance
schedule is specified by the user. It should consider site
criticality, location and available resource, together with the
prevailing operating conditions.
A maintenance schedule typically includes:
• Initial readings
Upon completion of the commissioning charge and immediately
after reverting to normal operation ensure that the battery
charging voltage is correct. Measure and record the ambient
temperature in the vicinity of the battery and all cell voltages.
Following a commissioning charge and after 6 months
continuous charge at the recommended float voltage, individual
cell voltages will stabilise within ±5% of the mean applied
voltage.
However, immediately following commissioning and for the
initial 6 months of continuous float charge, individual cell
voltage values outside the above tolerance may be observed
without adverse effect. There is no relationship between float
voltage and discharge capacity; cells are perfectly capable of
giving their discharge capacity even when outside the ±5%
range. After 6 months service, should any individual cell show a
continuing reduction or increase in voltage outside the above
limits over 3 successive monthly periods, EnerSys
®
should be
contacted for advice.
• Monthly readings
Ensure that the battery charging voltage is correct. Measure and
record the ambient temperature in the vicinity of the battery.
Visually inspect the battery; ensure it is kept clean and free from
corrosion. If necessary, clean with a damp cotton cloth and mild
detergent, do not use solvents or scouring powders.
• Three monthly readings
In addition to the monthly readings, measure and record the
voltage of all cells.
• Six monthly readings
In addition to the three monthly readings, measure and record
the internal ohmic value of all cells. Results should be compared
against previous readings such that a trend is generated
throughout a battery life cycle. EnerSys should be contacted for
advice when values change by 35% of the initial value.
• Annual readings
In addition to the six monthly readings, check all connections for
correct torque tightness and carry out a capacity discharge or
duty specification test.
• General
Record the details of any emergency or accidental discharge and
all corrective action that is undertaken.
It is recommended that records are kept in a manner such that
comparison with previous reports can be readily made.
11. Preservation
Keep the battery and surroundings clean and dry and ensure
bolted connections are tight. Keep connectors, pillars and bolted
connection covered with lanolised petroleum jelly.
Summary of Contents for PowerSafe 2DDM50-09
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