A microcontroller controlled battery fuel gauge and charger

State-of-charge indication for a secondary battery is becoming increasingly important for battery-operated electronics. Consumers are demanding fast charging times, increased battery lifetime, and fuel gauge capabilities. This paper presents an effective method of determining the state of charge in secondary cell batteries. A NiMH battery is used for the test since it is one of the more difficult batteries to determine state of charge. This method monitors the battery's temperature, voltage, and discharge/charge rate. A microcontroller then manipulates the information, using look-up tables to determine the state of charge. This technique can be used for both charge and discharge, without having to completely discharge the battery before each charging cycle. Also, by modifying the look-up tables, this technique can be employed in many other battery technologies, and is not limited to NiMH.<>