Abstract: Cycle life of power battery has a direct effect on the use of electric vehicles. This paper investigates
the life prediction methods by inducing cycle life degradation model of power battery based on nickel-metal
hydride batteries and manganese-based lithium ion batteries. Batteries were tested with reference of the
test method of FreedomCAR, the U.S. Department of Energy's fuel cell vehicles development programs, and
combined with the conventional power battery operating condition of China. Life decay way was studied with
the combination of normal cycle and bus cycle, with the fitting formula of battery cycle life attenuation being
determined. The results show that the Ni-MH battery and Li-ion battery capacities fade with cycle number
followed an exponential decay distribution and the 1/2 power change path respectively. The cycle life model
and reliability evaluation method are helpful for battery life prediction and establishing an accelerated cycle life
prediction model.

Key words: electrical vehicle;, power battery, normal cycle, bus cycle, capacity attenuation model