Battery charger detecting full charge of batteries using a thermostat and thermistor in a battery pack

摘要

A battery charging system is disclosed for charging two different types of battery packs, a known three terminal type including batteries and a thermostat switch, and a newer four terminal type further including a thermistor for sensing battery temperature. A charging control circuit stops charging current to the battery pack when a contact of the thermostat switch is open or when the thermistor detects a temperature above a predetermined temperature. If either the thermostat switch or the thermistor fail to properly operate, charging current to the battery pack is stopped securely to avoid damaging batteries.