Alpha Technologies Industrial Ni-Cd Batteries Standard Range - Manual (Page 17)

EN-ALPHA-TMSR-001 (10/09) 17
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Principles and methods of sizing of Alpha Ni-Cd-batteries for standby applications.
All our Ni-Cd batteries used for standby fl oating applications are sized according to the international sizing
method IEEE 1115. Alpha has developed a special calculation program which is available over the Internet and
allows us to update it regularly. It provides the possibility to calculate with multiple discharges, and to include the
temperature derating factor as well as the ageing factor of the battery. A signifi cant feature and advantage of the
Ni-Cd battery in comparison to the lead acid battery is that it can be fully discharged without any inconvenience
to the lifetime or recharge of the battery. Further, it is an advantage to discharge the battery to the lowest practical
value to extract the maximum energy the battery is able to provide in order to fi nd out the most benefi cial solution.
The most important sizing parameters are:
5.1 Voltage window
This is the minimum and maximum voltage acceptable for the system. The maximum voltage provides the voltage
that is available to charge the battery, whereas, the minimum voltage gives the lowest voltage acceptable to the
system to that the battery can be discharged.
5.2 Load profi le
The load profi le is the electrical performance required by the system from the battery for the particular application.
It can be expressed in terms of amperes for certain duration or in watts for certain duration. The requirements
might vary for example from just one discharge to multiple discharge of a complex nature. In order to calculate the
appropriated battery size please take into consideration point 5.1 voltage window.
5.3 Ambient temperature
The ambient temperature will have in any case an infl uence on the sizing of the battery (see point 4.4 Impact of
temperature on cell performance and 4.5 Impact of temperature on lifetime).
5.4 Recharge time and state of charge
Some application might require a full discharge cycle of the battery after a certain time after the previous
discharge. The factors to be taken into account depend on the depth of discharge, the rate of discharge as well as
the charging conditions.
5.5 Aging
It might be required that a value has to be added to ensure the correct service of the battery during the lifetime.
The value to be used depends on the discharge rate of the battery and on the conditions under which is carried
out. Our experts or partners are able to help you chosing the right battery for your special requirements.
5.0 Battery Sizing