Smart grid systems have been proposed to replace the conventional power distribution system in order to accommodate future market penetration of electric vehicles (EVs). Nevertheless, there are many factors to consider when large numbers of EVs require simultaneous charging in the smart grid. Among various optimization schemes, the most updated schemes proposed charging with coordination to optimize EV charging performance. In this case, huge amount of control signals are involved in the coordinated charging, therefore the charging performance is retarded. In this paper, a new threshold-based charging operation with historical average data of the EV charging system to improve the EV charging performance is proposed by minimizing control signal overhead, instead of maximum power delivery to all EVs. The moving average of historical data for BSOC levels of the EVs can properly approximate the charging profile of the EVs over time thus enabling the development of an optimization algorithm based on the threshold method. Up to 33% of the reduction in the control signal overhead is achieved with slight trade off in the power delivery to the EVs.