Method and device for judging the condition of secondary batteries and method for regenerating secondary batteries
The internal resistance related value which is related to the internal resistance of a secondary battery is compared with a previously obtained relation between the internal resistance related value and battery condition to judge the battery condition of the secondary battery. Since the internal resistance related value is a value related to the internal resistance which closely depends on the battery condition, the battery condition can be judged in detail based on the above relation. And the internal resistance related value can be obtained more speedily with a predetermined method. On the other hand, when the level of the degradation of a negative electrode is low, an electrolyte is supplemented, and when the level of the degradation of the negative electrode is high, a reducing agent is added to the electrolyte to regenerate the secondary battery. With this regenerating method, the performance of the negative electrode can be recovered without degrading a positive electrode.
1. A method for judging the condition of a secondary battery, characterized in that the method comprises the steps of obtaining a first resistance component mainly composed of an ion conduction resistance of an electrolyte, and a second resistance component mainly composed of a reaction resistance of electrodes respectively by a predetermined method as the internal resistance related value which is related to the internal resistance of the secondary battery, plotting an internal resistance co-ordinate showing a co-ordinate of the internal resistance of the secondary battery in a plane co-ordinate of which one axis component is the first resistance component and the other axis component is the second resistance component, and comparing the internal resistance co-ordinate with a previously obtained relation between the internal resistance co-ordinate and battery condition, which has been previously plotted on the plane co-ordinate, to judge the condition of the secondary battery.
2. A method as claimed in claim 1 , wherein a normal region as a set region of the internal resistance co-ordinate where a reference battery equivalent to the secondary battery is in a normal condition, and a degradation region as a set region of the internal resistance co-ordinate where the reference battery is in a degraded condition, are previously investigated and plotted in said plane co-ordinate, the position of the internal resistance co-ordinate of the secondary battery relative to said normal region and degradation region is investigated to judge whether the secondary battery is in a normal condition or degraded condition.
3. A method as claimed in claim 1 , wherein the degraded condition is divided into a first degraded condition which is mainly caused by an increase of an ion conduction resistance, a second degraded condition which is mainly caused by an increase of the ion conduction resistance and a reaction resistance, and a third degraded condition which is mainly caused by an excessive increase of the reaction resistance when the secondary battery is judged to be in the degraded condition, a first degradation region as a set region of the internal resistance co-ordinate where a reference battery equivalent to the secondary battery is in the first degraded condition, a second degradation region as a set region of the internal resistance co-ordinate where the reference battery is in a second degraded condition and a third degradation region as a set region of the internal resistance co-ordinate where the reference battery is in a third degraded condition are previously investigated respectively, and plotted in the plane co-ordinate, the position of the internal resistance co-ordinate of the secondary battery relative to the first degradation region, second degradation region and third degradation region is investigated to judge whether the secondary battery is in the first degradation region, second degradation region or third degradation region.