Patent ID: 8527225

Claim:
An estimation apparatus comprising a controller which estimates an internal reaction of a secondary battery, wherein the controller calculates a voltage drop amount due to an internal resistance of the secondary battery by using an expression (I): Δ ⁢ ⁢ V = RT αβ ⁢ ⁢ F ⁢ arc ⁢ ⁢ sinh ( - R r ⁢ I RT αβ ⁢ ⁢ F ) - R d ⁢ I ( I ) where ΔV represents the voltage drop amount, R represents a gas constant, T represents a temperature, α represents an oxidation reduction transfer coefficient (α=0.5) of an electrode, β represents a correction coefficient (0<β<1), F represents the Faraday constant, I represents a discharge current, Rr represents a component of a reaction resistance included in the internal resistance, and Rd represents a component of a direct-current resistance included in the internal resistance.