Electric cars, with a history ranging back more than hundred years, are experiencing a renaissance. The rise in fuel costs, improved battery technologies and government incentives are just some of the factors that – in the long run – make Electric Vehicles (EVs) a great choice especially for individual mobility in the growing megacities. China shows an impressive rollout plan, but also European countries are driving this trend. Germany has a plan for 1 million EVs until 2020, France is moving ahead even faster with massive government funding for a plan to install 1 million EV charging spots until 2015 and 2 million EVs until 2020. The increased distribution of EVs also offers new business opportunities for utility providers creating new income sources and - in the future -also allow grid stabilization (cut of peak loads) via the EV's battery as buffer feeding energy back into the power grid.
The charging of these EV batteries can be done in different ways. The majority of the charging cycles will certainly happen at home or at work (estimation 80%), but public charging spots are required as well to ensure a fine grid of supply. There are different possibilities for charging. The most basic one is to use a single phase power supply of 230V and up to 32A AC via a typical 3kW On-Board-Charger, but also via a 3 phase 400V with up to 63A AC (typical 20kW charger). Charging with these currents is typically taking hours and is combined with parking times of the car (home, work, shopping). A closer equivalent of a gas station for conventional combustion engine cars is the DC charging (or also called fast charging) ranging up to 100kW power, but this has to be possible without damaging the battery pack.
Electric vehicles as part of the smart grid
All of these charging situations in public drive the need for user interaction at the charging spot. For