Patent ID: 8866446
Filing Date: 2014-10-21
Classification: G01R,H01M,H02J,Y02E

Abstract:
1. An end-of-discharge voltage correction device for correcting an end-of-discharge voltage of a first parallel-connected unit in which sodium-sulfur battery cells or series-connected units each including series-connected cells are connected in parallel with one another, said end-of-discharge voltage correction device comprising: a discharge depth deriving section for deriving a discharge depth of the first parallel-connected unit in each charge/discharge cycle; an increment deriving section for deriving an increment of an equivalent cycle count in each charge/discharge cycle, said increment becoming greater as the discharge depth derived by said discharge depth deriving section increases; an equivalent cycle count deriving section for deriving the equivalent cycle count by adding the increment derived by said increment deriving section; an information holding section for holding information indicative of a relationship between an open voltage and a discharge depth; a first absolute depth deriving section for, with reference to the information held by said information holding section, deriving, as an absolute depth, a discharge depth of the first parallel-connected unit corresponding to an open voltage after termination of discharge of the first parallel-connected unit; a second absolute depth deriving section for, with reference to the information held by said information holding section and referred to by said first absolute depth deriving section, deriving, as an absolute depth, a discharge depth of a second parallel-connected unit corresponding to an open voltage after termination of discharge of said second parallel-connected unit, said second parallel-connected unit being connected in series with the first parallel-connected unit; a ratio deriving section for deriving the ratio of a capacity discharged by the second parallel-connected unit from initiation of the discharge until the absolute depth derived by said second absolute depth deriving section is reached with respect to a capacity discharged by the first parallel-connected unit from initiation of the discharge until the absolute depth derived by said first absolute depth deriving section is reached, in a case where it is assumed that a healthy parallel number of the first parallel-connected unit is equal to a healthy parallel number of the second parallel-connected unit; a healthy parallel number deriving section for deriving the healthy parallel number of the first parallel-connected unit by multiplying the healthy parallel number of the second parallel-connected unit by the ratio derived by said ratio deriving section; an ohmic resistance correction section for increasing an estimated value of an ohmic resistance of the first parallel-connected unit as the equivalent cycle count derived by said equivalent cycle count deriving section increases, while increasing the estimated value of the ohmic resistance of the first parallel-connected unit as the healthy parallel number derived by said healthy parallel number deriving section decreases; and an end-of-discharge voltage correction section for: subtracting, from an end-of-discharge open voltage, the product of a discharge current of the first parallel-connected unit and the estimated value of the ohmic resistance of the first parallel-connected unit corrected by said ohmic resistance correction section and the product of the discharge current of the first parallel-connected unit having a time delay process performed thereon and a polarization resistance of the first parallel-connected unit; and setting a resulting value as an end-of-discharge voltage.