Patent ID: 7459912

Claim:
A life determining method of a nickel-hydride battery, comprising the steps of: (a) preparing beforehand data representing a relationship of life of the battery to load power applied to the battery in discharge and environmental temperature of a place where the battery is installed; (b) measuring the load power and the environmental temperature of the battery in discharge; (c) selecting a life value corresponding to the measured values of the load power and the environmental temperature from the data to set the life value as an expected life value; (d) calculating a first life reduction amount from a natural logarithmic function with the number-of-discharges of the battery as a variable; (e) calculating an average value of battery temperatures measured at a fixed time interval during charge and discharge or during pause of the charge and discharge, to calculate a second life reduction amount from the product of the number-of-discharges and a value of an exponential function with the difference between the average value of battery temperature and the measured value of environmental temperature as a variable; and (f) setting a value obtained by subtracting the first life reduction amount and the second life reduction amount from the expected life value to a remaining life value.