Patent attributes
An object of the present invention is to provide a battery condition monitor that is capable of reducing labor and equipment costs for parameter setting for evaluation of the battery's condition and capable of readily responding to variations due to individual differences among the same model of vehicles. The battery condition monitor according to the present invention measures a lower limit voltage value for the time when a load during engine startup is substantially connected to a brand-new battery, as an initial reference lower limit voltage value VLIF; and derives a reference discharge characteristic of the brand-new battery with respect to the vehicle-unique load during engine startup, using the initial reference lower limit voltage value VLIF, an initial reference no-load voltage value VOIF which is a no-load voltage of that battery, and information about the rate of change in the internal resistance with respect to change in the no-load voltage of the battery, the information being previously stored in a storage unit, thereby to evaluate the condition of the battery based on the reference discharge characteristic.