The range of the batteries being used is currently one of the most critically discussed aspects of electric vehicles. Although one battery charge is sufficient for over 80 % of the daily trips driven, situations do arise where a greater range must be reliably guaranteed. Stadtwerke Offenbach Holding GmbH is therefore running a trial of two fast-charging technologies in order to be able to drive purely on electric power even in the event of longer journeys arising.

The group’s delivery vehicles generally need an average daily range of 50–70 km andin any case not more than 170 km. Not all journeys, therefore, can be made on a purely electric basis using the electric car models currently on the market – especially if auxiliary consumers such as heating and lights are switched on or the outside temperature is low and battery capacity thus drops.

Against this backdrop the group installed two different fast-charging technologies in the trial. Using the DC fast-charging method the user is able to charge the vehicle battery back up to 80 % within 25 minutes. This is being tried out in the project with the Mitsubishi I-MiEV, which in addition to this connector has another for gentle charging of the battery overnight from a domestic electricity socket. For comparison purposes, AC charging, the method primarily favoured in Germany, was tried out with the Stromos vehicle. The electric car charges through an intelligent control system between vehicle and charging infrastructure at up to 32 A and 400 V. The charging process takes up to 3 hours. The plug used is an IEC type II, which is currently going through the standardisation process.

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