The method of estimating the battery charging rate estimating means and a battery charging rate

Providing the battery charging rate estimating means estimating the charging rate of the battery, said battery charging rate estimating means and the battery charge estimation methods can be battery charging rate (SOC) estimation error suppressed to a small level. Estimating battery charging apparatus comprising: a charge and discharge current detection unit, a terminal voltage detection means calculation coulomb charging rate estimation unit for integrating charge and discharge current value by calculation and coulomb charging rate estimation; charging open circuit voltage estimation rate estimation unit for open circuit voltage estimation value from the charge and discharge current and the terminal voltage value of the open-circuit voltage estimated value and the estimated value of the open circuit voltage estimating the charging rate; calculating a first difference means for obtaining by method coulomb charging rate calculated by the charging rate and the charging rate between the open circuit voltage difference method based on the difference in charging rate, estimated by using the error model as the state quantity of the error of the error model; and a second difference calculating unit , the rate for charging the battery is calculated by subtracting the charging rate by the Coulomb calculation method to the error.