Patent ID: 8004243

Claim:
A method for estimating battery capacity of a battery, the method comprising the steps of: reading CAC Prior , wherein CAC Prior is the last determined computed amp-hour capacity of the battery; monitoring battery current of the battery using a current sensor; determining SOCbyAh First time at a first time, wherein h SOCbyAh First time is the state of charge of the battery calculated by amp-hours at said first time; determining SOCbyOCV First time at said first time, wherein SOCbyOCV First time is the state of charge of the battery calculated from the battery open circuit voltage (OCV) at said first time; determining SOCbyAh Second time at a second time, wherein SOCbyAh Second time is the state of charge of the battery calculated by amp-hours at said second time; determining SOCbyOCV Second time at said second time, wherein SOCbyOCV Second time is the state of charge of the battery calculated from the battery OCV at said second time; calculating ΔSOCbyAh, wherein Δ SOC by Ah=SOC by Ah First time −SOC by Ah Second time calculating ΔSOCbyOCV, wherein Δ SOC by OCV=SOC by OCV First time −SOC by OCV Second time ; calculating a weighting function, W, defined as W = 100 - ( k ⁢ ⁢ 1 * 100 * SOCbyAhError Δ ⁢ ⁢ SOCbyAh + k ⁢ ⁢ 2 * 100 * SOCbyOCVError Δ ⁢ ⁢ SOCbyOCV + k ⁢ ⁢ 3 * SOCbyOCVErrorPrev ) wherein SOCbyAhError is the error associated with determining SOCbyAh, SOCbyOCVError is the error associated with determining SOCbyOCV, SOCbyOCVErrorPrev is the previously determined error associated with SOCbyOCV, and k 1 , k 2 and k 3 are constants; and calculating CAC Updated , wherein said CAC Updated =(W)(CAC Prior ).