Patent ID: 7768233

Claim:
An automated method for determining state of charge (SOC) of a battery having an ohmic resistance (R), a double layer voltage (V dl ), an open circuit voltage (V oc ), and a characterizing constant ( A = 1 C dl ) , where C dl is a double layer capacitance of the battery, the method comprising: obtaining, at an electronic and processor-based energy management controller, sampled terminal voltage (V) data for the battery; obtaining, at the energy management controller, sampled terminal current (I) data for the battery; calculating, with the energy management controller, a vector quantity φ (k) in accordance with the relationship φ (k)=[dt(k)V(k −1), I(k)−I (k−1)dt(k)I(k−1)dt(k)U(k −1)] T , where k indicates a present time step, T indicates a matrix transpose, and U( )indicates a unit step function; calculating, with the energy management controller, battery parameters θ 1 , θ 2 , θ 3 , and θ 4 in accordance with the relationship V(k)−V(k−1)=θ T θ (k), where θ=[θ 1 , θ 2 , θ 3 , θ 4 ] T and T indicates a matrix transpose; generating, with the energy management controller, a present SOC value from the battery parameters θ 1 and θ 4 ; and saving θ in a memory element, for use as an initial condition for a subsequent iteration of the method; wherein θ 1 = - B = - 1 τ , where τ is a double layer time constant for the battery; θ 2 =R; θ 3 =BR +A; and θ 4 =BV oc .