Patent ID: 8432135

Claim:
A method of controlling a lead-acid battery, comprising: a first computation step of computing a first accumulated charged electrical quantity by accumulating a charged electrical quantity for each charge cycle from the start of cycled use of a lead-acid battery, and of computing a first accumulated discharged electrical quantity by accumulating a discharge electrical quantity for each discharge cycle from the start of cycled use of the lead-acid battery; a judgment step of judging that the lead-acid battery is in a first region which is a partial region in a life cycle from the start of cycled use of the lead-acid battery until the life of the lead-acid battery ends, when the first accumulated discharged electrical quantity is less than a first setting value D 1 which is the first accumulated discharged electrical quantity obtained when, in a process of change of a capacity of the lead-acid battery occurring due to charge/discharge cycles of the lead-acid battery, the capacity is the maximum value D max , and of judging that the lead-acid battery is in a second region which is a region after the first region and extends until the life of the lead-acid battery ends, when the first accumulated discharged electrical quantity exceeds the first setting value D 1 ; a second computation step of, after judging in the judgment step that the lead-acid battery is in the second region, computing a second accumulated charged electrical quantity by accumulating a charged electrical quantity for each charge cycle in the second region, and of computing a second accumulated discharged electrical quantity by accumulating a discharged electrical quantity for each discharge cycle in the second region; and a control step of controlling the charged electrical quantity in the first region such that a first entire charged electrical quantity C 1 , which is the first accumulated charged electrical quantity at the end of the first region, is the electrical quantity equal to the product of the first setting value D 1 and a first value R 1 set in advance, and of controlling, after the lead-acid battery is judged to be in the second region, the charged electrical quantity in the second region such that a second entire charged electrical quantity C 2 , which is the second accumulated charged electrical quantity when the life of the lead-acid battery comes to an end, is the electrical quantity equal to the product of the second setting value D 2 , which is the second accumulated discharged electrical quantity when the life of the lead-acid battery comes to an end, and a second value R 2 set in advance to a value smaller than the first value R 1 .