Charging Control of NiCd or NiMH Secondary Batteries or Chargers with the NTS Series

Outline

• Characteristically, NiCd or NiMH secondary batteries cannot be charged over a specified temperature, and they can be quickly charged only within a specified temperature range. Murata's NTS Series NTC Thermistor is used to promptly detect the temperature range that will allow quick charging. (*1 in the figure below)
• Murata's NTS Series NTC Thermistor reliably detects the completion of charging by detecting a temperature rise of the battery itself (*2 in the figure below). (In addition to this method, the Delta-V detection method (which uses a decrease in the battery's electromotive force occurring at the completion of charging) is available to check whether charging has completed. However, this method may cause detection errors if the ambient temperature changes during charging.)

Circuit example: Temperature detection of secondary battery and charger

Roles of the NTC Thermistors

• Detects temperature rises of the battery cell during charging.
• Detects the ambient temperature that will allow quick charging.
• Detects heat generation of a battery cell caused by abnormal current.
• Performs temperature compensation for voltage measurement for display of the remaining amount of energy.