The centralized utilization of batteries retired from electric vehicles(EVs)can be a new kind of flexible loads participating in power dispatch. The operation and output characteristics of second-life batteries are studied based on the experiment data. A risk power dispatch model with second-life batteries as flexible loads considering the discordance risk of retired batteries and the error risk of second-life batteries and wind generators is built. The model aims at the minimum operation cost and risk of the system and the second-life batteries is utilized to reduce the peak valley difference of power load and the fluctuation of the power system and save energy. The simulation results on a ten-unit test system have certified the effectiveness of the proposed dispatch model and the economic benefit of utilizing second-life batteries as flexible loads.