Alpha Technologies Lomain Ni-Cd Pocket Plate Battery - Manual (Page 17)

17 745-680-B10-001 Rev. A
4.0 Operating Features
4.1 Capacity
The capacity of Nickel-Cadmium batteries is rated in ampere-hours (Ah) and is the quantity of
electricity at +20 °C (± 5 °C) available for a 5 hour discharge after being fully charged for 15
hours at 0.2C5. These figures and procedures are based on the IEC 62259 standard.
According to IEC 62259, 0.2C5A is also expressed as 0.2 ItA. The reference test current It is
expressed as:
ItA= Cn Ah 1h
Cn is the rated capacity declared by the manufacturer in ampere-hours (Ah) n is the
time based in hours (h) for which the rated capacity is declared
4.2 Cell voltage
The cell voltage of a Ni-Cd cell is the result of the electrochemical potentials of the Nickel and
the Cadmium active materials in the Potassium hydroxide electrolyte. Therefore, the nominal
voltage for this electrochemical couple is 1.2 V. From the electrochemistry of the reaction
given above, the free voltage of 1.3 V is given for the Ni-Cd cell. This voltage is also observed
directly after charging of the cell.
4.3 Internal resistance
The internal resistance of a Ni-Cd cell is dependant upon several factors, e.g., battery
temperature, state of discharge (whether high or low), cell type and size. The internal
resistance also depends on the cell type and size as well; it increases for lower state of
charge. Apart from this the internal resistance of a fully discharged cell no carries weight.
Reducing the temperature also increases the internal resistance. Contact your local
representative for specific information regarding conditions that may affect the battery.