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1.3.1 CONVERSION OF ENERGY
During charging, the active masses of the electrodes
convert electrical energy into chemical energy. The
discharge process reaction reverses it.
1.3.2 ELECTROLYSIS AND EVOLUTION OF
GAS DURING OVERCHARGE AND
REVERSAL CHARGE
During overcharge, the water of the electrolyte is
decomposed. The hydrogen generated at the negative
Cadmium electrodes and oxygen generated at the positive
Nickelhydroxide electrodes escape through the vent of
the cell.
2 H20
1.3.3 OXYGEN RECOMBINATION BY INTERNAL
ELECTROCHEMICAL REDUCTION ON
ELECTROLYTE-WET LIVE PARTS
A part of the oxygen generated, reduces according to the
two side reactions below. According to 1.3.2, the reduced
oxygen is equivalent to an amount of hydrogen that is not
generated. In total, the recombination of oxygen
suppresses the decomposition of water, but it heats
the cells.
+
+
O
2 H
0
4e°
2
2
Chemical reduction of oxygen at electrolyte-wetted
Cadmium during normal overcharge.
+
+
2 Cd 0
2 H
0
2
2
1.4 Specified definitions
1.4.1 CURRENT RATES
The current rates express values of current in ampere (A)
used to charge and discharge cells and batteries as a
multiple of its (nominal) current. For example, a current of
20 A used to charge a cell with a rated capacity of 100 Ah
would be expressed as C
1.4.2 RATED CURRENT (I
The rated discharge current of the battery returns not
less than its rated C
capacity in 1 hour.
1
The document reference is online, please check the correspondence between the online documentation and the printed version.
+
2H2
02
+
4 0H° Heat
+
2 Cd (OH)
Heat
2
= 0.2*I
or 0.2 C
= 0.2*I
5
1
1
)
1
1.4.3 RATED CAPACITY C
The rated capacity is the minimum capacity, expressed in
Ah, obtained from a charged battery when discharged at
the I
rate to the EPV.
1
1.4.4 CONSTANT VOLTAGE CURRENT I
The I
is the discharge current, which the battery delivers
pr
at the conclusion of a 15sec power discharge, controlled
as maintained a constant voltage of half the nominal
battery voltage.
1.4.5 EPV = END POINT VOLTAGE OF
THE BATTERY
Unless otherwise stated during discharge the EPV of the
battery corresponds roughly to 1 Volt * number of cells.
1.5 Commonly used terms
1.5.1 CONSTANT (LOW) CURRENT
CHARGING (APPENDIX 2)
The constant current charging is a method used to charge
a fully discharged battery with a predefined current and
duration. The recommended rates for charge are 0.2*I
7 hours, or 0.1*I
for 14 hours. For the commissioning and
1
reconditioning of cells 8 hours at 0.2*I
recommended.
1.5.2 IUI CHARGING – (FAST CHARGING IN
ACCORDANCE WITH APPENDIX 1)
The IUI-charge recommended in this manual is a general
method for recharging the batteries from an unknown
state of charge. It shall not be applied at battery
temperatures below 0°C and on batteries stored inactive
for more than 3 month.
1.5.3 END OF CHARGE VOLTAGE
The end of charge voltage is the voltage of a battery or
cell prior to the charge current being switched off.
1.5.4 CONSTANT VOLTAGE CHARGING
Constant voltage charges (e.g. at 1.425 Volt per cell) shall
not be used to maintain and recondition the cells of
batteries as the overcharge at constant current (section
1.5.1) is more efficient to condition cells imbalanced from
cyclic services with constant voltage charges and shallow
discharges.
.
1.5.5 CAPACITY TEST
1
A capacity test is the measurement of the discharge time
and the discharge voltage at a constant discharge current
until the defined EPV is met. The product of discharge time
and discharge current calculates the capacity.
8
1
PR
for
1
is strongly
1
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