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MIT Technology Review
MIT Technology Review
How Electric Cars Swap Batteries
Better Place’s switching stations allow electric cars to swap batteries during long trips.
Photographs by Gil Lavi
October 25, 2011
Each Better Place charge point is connected wirelessly to a national operations center that tracks the energy needs of all batteries in the network. The rate of charge can be varied to balance demand on the electricity grid with the need to ensure that each battery is prepared for a car’s next journey. When possible, charge points draw the most electricity during off-peak hours, soaking up excess capacity when demand is low.
A display to the left of the speedometer, similar to a gas gauge, shows the battery’s remaining charge. The car’s computer continuously monitors the charge level and the distance to the planned destination. If the battery doesn’t have enough charge to make it, the driver is notified and offered a route to the most convenient switching station. Better Place’s Israeli network is designed so that one is never more than 25 miles away.
A battery switching station looks much like a car wash. Hydraulic clamps take hold of the wheels and maneuver the vehicle into position over the underground machinery that will change the battery. Screens inside the car and on the wall of the station guide the driver.
As the car approaches the station, it identifies itself over a wireless link so that the correct type of battery can be moved into place.
Beneath the switching station, a series of industrial robots handle a stock of 16 batteries, one of which can be seen at the lower right in this image. To maintain their capacity, the batteries are kept cool as they are recharged. Each battery has a maximum capacity of 22 kilowatt-hours, yielding a driving range of approximately 100 miles in normal conditions. Better Place calculates that this range is sufficient forof regular journeys, with the switching stations on hand for the rest.
The underside of the car is automatically washed and dried, and then a well opens beneath the car so the battery switcher can go to work.
A robot reaches up to release and remove the car’s battery, which sits between the rear passenger seat and the trunk. That battery is lowered into a rack, where it will be recharged. The robot then lifts a fully charged replacement battery into the vacant space. After the opening closes, the clamps release the car. The entire process takes three minutes and 40 seconds.