Abstract: A car power source apparatus is provided with a driving battery which drives an electric motor, heaters which heat the driving battery, a control circuit which controls power to the heaters, a temperature sensor which detects battery temperature and issues a detected temperature signal to the control circuit, and a surrounding temperature sensor which detects surrounding temperature and also issues a detected temperature signal to the control circuit. When the car is not being driven and the driving battery is heated via the heaters powered by the driving battery, the set temperature is changed corresponding to the detected surrounding temperature in the control circuit.

Abstract: A method of detecting a state-of-charge of a battery detects a current of a battery and a voltage of the battery, calculating a state-of-charge of the battery as a first state-of-charge based on an integration of the current of the battery thus detected, while calculating the state-of-charge of the battery as a second state-of-charge based on the voltage of the battery and calculating a synthetic state-of-charge obtained by taking a weighted mean of the first state-of-charge and the second state-of-charge as the state-of-charge of the battery, and weighting the weighted mean in order to increase weighting of the second state-of-charge in a region in which a capacity of the battery is increased and a region in which the capacity of the battery is reduced and to increase weighting of the first state-of-charge in other regions.

Abstract: The car power source apparatus is provided with a driving battery which drives an electric motor, heaters which heat the driving battery, a control circuit which controls power to the heaters, a temperature sensor which detects battery temperature and issues a detected temperature signal to the control circuit, and a surrounding temperature sensor which detects surrounding temperature and also issues a detected temperature signal to the control circuit. When the car is not being driven and the driving battery is heated via the heaters powered by the driving battery, the set temperature is changed corresponding to the detected surrounding temperature in the control circuit.