Smart charging and V2G is the method by which a charging network decides when each vehicle charges, to spare the power grid at busy hours, and by which a car can even send power back. V2G means vehicle-to-grid, the sending of power from a vehicle's battery back to the grid.
Without smart charging, every driver starts charging as soon as the car is parked. In the evening this adds a large load to the grid at the same time as lights and fans. With smart charging, the charging network software slows some charges and delays others. It gives priority to the vehicles that must leave early. This is a form of grid balancing.
Here is a typical case. A gated community in Noida has 20 car chargers and a transformer that can supply 100 kilowatts. If all 20 cars charge at 7 kilowatts each, the demand is 140 kilowatts. The software limits each car to 5 kilowatts, so the demand is 100 kilowatts. It gives more power to the cars whose owners leave at 6 a.m. After 11 p.m., when other demand falls, it raises the charging rate again.
The owner can usually set a departure time in the app, for example "ready by 7 a.m." The software then works backwards. It needs only a few hours at full speed to fill the battery, so it can wait for cheaper or less busy hours. Under India's time-of-day tariff rules, electricity distribution companies charge less in the daytime solar hours and more in the evening peak. Some states also charge less after midnight. Smart charging uses these differences.
V2G goes one step further. At 7 p.m., a car with a full battery and an owner who will not need it until morning can send 3 kilowatts back for an hour. A virtual power plant (VPP) combines many such small sources and sells their flexibility to the grid. The smart part sits at the grid edge, where homes and vehicles meet the grid. V2G is rare in India today.