Alpha Technologies Industrial Ni-Cd Batteries Standard Range - Manual (Page 15)

EN-ALPHA-TMSR-001 (10/09) 15
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4.7 Open Circuit Loss
The state of charge of a Ni-Cd cell on open circuit slowly self-discharges. Ni-Cd batteries are affected signifi cantly
by temperature. The higher the temperature, the higher loss of capacity. Ni-Cd batteries self-discharge at a
niminal rate of 2% per month at 20°C.
4.8 Cycling
The Alpha Ni-Cd battery is designed to obtain a huge number of cycles in stationary standby operations. The
important fact and basis for the number of cycles the battery is able to provide is the depth of discharge. The less
deeply a battery is discharged the greater the number of cycles it is capable to provide before being unable to
achieve the minimum design limit. On the graph below typical values for the effect of depth of discharge on the
available cycle life can be found.
4.0 Operating Features, continued
Graph 4-3, Self-discharge of NiCd-accumulators (fully charged)
Graph 4-4, Cycle life vs. depth of discharge as a percentage of rated battery capacity @ 20°C