In a battery management controller, analog-to-digital conversion circuitry converts analog signals, indicative of a battery voltage, a battery current, and a battery temperature, to digital signals. A memory stores a remaining-capacity lookup table that includes multiple groups of data. Each group of data includes a voltage, a current, a temperature, and a parameter associated with a remaining capacity corresponding to the voltage, the current and the temperature. A processor searches the lookup table for a current parameter value and an end-of-discharge parameter value based on the digital signals, and determines a full available charge capacity of the battery based on the current parameter value and the end-of-discharge parameter value. The processor also counts the number of charges flowing through the battery based on a battery current. The processor further determines an available state of charge of the battery according to the full available charge capacity and the number of charges.