Battery apparatus and method for monitoring battery state of a secondary battery

A method for evaluating characteristic of a secondary battery passing power to/from one or more electric devices mounted on a vehicle, the method comprising steps of:

• measuring the current and voltage of the secondary battery according to a plurality of frequencies generated by the one or more electric devices;
• calculating impedance of the secondary battery from the measurement results;
• and
• evaluating the battery characteristic of the secondary battery from the impedance calculated;
• wherein the electric device is a generator driven by an internal combustion engine of the vehicle and measure current and voltage of the secondary battery while controlling the output of the generator and changing the frequency of the state detection current applied to the secondary battery, the method further comprising steps of:
• calculating an impedance from the plurality of measurement results;
• calculating the remaining amount of the secondary battery from the impedance and the battery characteristic;
• calculating a parasitic capacity of the secondary battery from the remaining amount and the impedance;
• performing deterioration calculation according to the parasitic capacity of the secondary battery to obtain a service life;
• calculating a correction value of the change of the remaining amount or the service life according to the integration current of the secondary battery successively measured during the impedance calculation;
• maintaining an error of the calculation result of remaining amount or the service life up to the preceding time;
• calculating an error caused by the current calculation result in which the change from the preceding calculation result is corrected;
• and
• obtaining a weighted mean of the error of the preceding error and the current error.

A secondary battery evaluation method for evaluating a secondary battery by calculating the impedance according to measurement results of current and voltage of the secondary battery and referencing the battery characteristic, the method comprising steps of:

• calculating the impedance while successively changing the frequency of the current flowing to the secondary battery;
• calculating the remaining amount of the secondary battery from the impedance and the battery characteristic;
• calculating a correction value of the remaining amount change according to an integration current of the secondary battery successively measured during impedance calculation;
• and
• calculating the remaining amount of the secondary battery by averaging the remaining amount and the correction value.

A battery apparatus for evaluating battery characteristic of a secondary battery passing power to/from one or more electric devices mounted on a vehicle, comprising:

• control means for applying the state detection current by a plurality of frequencies generated by operation of the one or more electric devices to the secondary battery;
• impedance calculation means for measuring current and voltage of the secondary battery based on the frequency and calculating the impedance of the secondary battery from the measurement results;
• storage means containing characteristic relationship between the remaining amount and the impedance of the secondary battery;
• and
• battery characteristic calculation means for evaluating the battery characteristic of the secondary battery for the impedance calculated according to the characteristic relationship;
• wherein the electric device is a motor/generator for driving the vehicle and generating electricity by receiving the drive force from the vehicle or a generator driven by an internal combustion engine as a passive source of the vehicle and the control means detects a non-power running period of the motor/generator, stops output of the motor/generator or the generator, and changes the frequency of the state detection current applied to the secondary battery.

A battery apparatus comprising:

• a voltage/current detection unit for detecting voltage and current of a secondary battery;
• a storage unit for storing battery characteristics of the secondary battery calculated in advance so as to be referenced;
• and
• a CPU having an impedance calculation unit for calculating the impedance of the secondary battery from the detected voltage and current, a remaining amount calculation unit for calculating the remaining amount of the secondary battery according to the calculated impedance and the battery characteristics, a remaining amount change correction unit for correcting the remaining amount change according to an integration current of the secondary battery, a service life calculation unit for calculating the service life of the secondary battery according to the parasitic capacity calculated by the impedance calculation unit and the remaining amount calculated by the remaining amount calculation unit, and a service life change correction unit for correcting the service life change;
• wherein the calculation results of the remaining amount calculation unit and the remaining amount change correction unit and/or the service life calculation unit and the service life change correction unit are subjected to weighted mean to obtain the remaining amount and/or the service life of the secondary battery.