Charging in this way requires two sets of batteries for the electric vehicle, with one set of batteries powering the electric vehicle and the other set doing the ground DC charging.If the battery in use runs out of power, it is removed and replaced with another set of batteries. Charging in this way greatly reduces charging time. But the cost of shortening the charging time is the need to set up in a larger number of battery replacement stations, and need a lot of staff to maintain the battery replacement station, so need to invest a lot of cost, reducing the charging of electric vehicles intelligent, so generally do not use this way of charging.