NiCd (Nickel-Cadmium) battery charger is an electronic device that controls current and voltage, designed to safely charge rechargeable batteries or battery groups with NiCd chemistry. In order for NiCd batteries to have a long life, the output values of the charger (rectifier) must be precisely adjusted according to the capacity (Ah) and number of cells of the battery. How Does a NiCd Battery Charger Work? NiCd batteries are constant current due to their structure. It requires charging with (constant current). The charging process consists of the following stages and principles: Constant Current Stage: The charger keeps the current constant until the battery is charged. The voltage of the battery gradually increases as it is charged. Cell Voltage Monitoring: The nominal voltage of NiCd cells is 1.2 V. During charging, this value reaches 1.4 V to 1.45 V per cell. Charging Cut-off Methods (Delta V): When NiCd batteries reach full charge, there is a slight decrease in voltage. Smart chargers stop charging or switch to "trickle charge" mode when they detect this -Δ V (negative delta voltage) curve. Temperature Monitoring (Δ T / Δ t): Fully charged NiCd batteries begin to convert energy into heat. Safe devices detect a sudden temperature increase and cut off the current.
How Should the Rectifier Output Be According to Battery Ah Capacity? There is a direct mathematical relationship between the capacity of NiCd batteries (Ah) and the current (A) and voltage (V) outputs of the industrial rectifier.
Net Result To charge a NiCd battery, your rectifier must have a constant current mode, the current output must be set to 10% of the battery Ah value (0.1C), and the total output voltage must be limited to not exceed the number of cells connected in series × 1.42 V.
