Problems with charging: myth and reality

Technology sceptics see more problems than opportunities with rapid charging. Unfounded criticism, according to Jürgen Schenk, Head of Electric Drive Integration at Daimler AG.

As with many new technologies, electromobility needs to prove itself in the face of a flood of prejudices. Among these are numerous false, yet frequently propagated assertions. One examples concerns rapid charging, which allows electric vehicles to achieve a range similar to that of those with a combustion engine. The possibility to charge the battery within a short period of time is far too complicated and prone to problems, according to these sceptical, self-proclaimed "experts". Furthermore, the tech-sceptics add, regular charging leads the batteries to implode. The necessary infrastructure is also not given, they say.

Complicated and problematic? Insufficient infrastructure? Imploding batteries? Jürgen Schenk, Head of Electric Drive Integration at Daimler AG, smiles. "There's nothing complicated about rapid charging. Our electric vehicles will all be equipped with a plug on the side wall which permits charging with both alternating and DC voltage." This is the so-called CCS connector (Combined Charging System), which is standard in Europe. For rapid charging, using alternating voltage means charging can theoretically be carried out with 43 kilowatts. "In practical situations," explains Mr Schenk, "the chargers currently offer between 7 and 22 kilowatts. In order to be able to charge the battery, the vehicle must be appropriately equipped with a system which transforms alternating voltage into DC voltage. The majority of vehicles are currently equipped with a system suitable for eleven kilowatts. This way, a battery can be charged sufficiently for a range of 500 kilometres in approximately seven to eight hours."

Time-saver: Over the course of a year, charging, instead of refueling, will save you 10 minutes of time.

100 kilometres range in four minutes

With a DC voltage connector one can attain up to 350 kilowatts, in theory. DC voltage chargers currently allow for 50 kilowatts, and thus a 500-kilometre charge can be completed in around 2 hours. Schenk explains that on motorways "charging stations are currently being built which can charge a vehicle with sufficient energy to last 300 kilometres – all in 30 minutes and with up to 150 kilowatts." Meanwhile, the most advanced technology – so-called High Performance Charging – offers an output of 350 kilowatts, whereby only four minutes of charging yield a range of 100 kilometres. "That corresponds roughly to the time required to refuel a vehicle with a conventional drive system today." With this scenario in mind, the future will see charging parks specifically designed for this purpose, which offer both charging possibilities and various connections.

On motorways, charging stations are currently being built which can charge a vehicle with sufficient energy to last 300 kilometres – all in 30 minutes and with up to 150 kilowatts.

Jürgen Schenk, Head of Electric Drive Integration at Daimler AG

With the most basic charging technology, such a station will deliver one megawatt, dividing the energy across 16 chargers each with an output of 150 kilowatts. If all 16 connections are occupied, the charging output decreases accordingly. Schenk believes that the infrastructure in Germany will drastically surpass the development of electric vehicles in the coming years. "And by 2022, we shouldn't fear any bottlenecks."

Daimler is working with other car companies on the creation of a Europe-wide rapid charging network

Daimler is currently part of a joint venture with other vehicle manufacturers (Ford, VW and BMW) working on building a Europe-wide rapid charging network. "We assume that the public infrastructure will be dominated by the 150 kilowatt variant. That's also a good thing, as not all small vehicles will be sufficiently equipped to cope with charging outputs of 350 kilowatts. Thus we plan to implement the high charging output with the upper vehicle segments."

For small vehicles, which do not need to be equipped to handle longer ranges, the technical outlay for greater charging performance will not be worthwhile. Schenk therefore thinks that "vehicles equipped for the 350 kilowatt variant will predominantly be destined for long-distance driving." Compact cars will probably be capped at 150 kilowatts. Purely for cost reasons, the 350-kilowatt technology will not make headway in this segment.

Charging with typical domestic connectors

Besides rapid charging, one will still be able to charge electric vehicles at home or at work without any trouble in the future. And that's where the proven eleven-kilowatt technology comes into play. "This technology can be optimally used with the existing private infrastructure. Here, I'm referring to typical household electrical connections. Nothing needs to be changed here," explains Schenk.

And what about batteries? How do batteries cope with regular rapid charging? Or let's put it another way: how often will the rapid charging technology actually be used in everyday life? Jürgen Schenk clarifies the situation: "We firmly believe that we can make rapid charging with up to 350 kilowatts possible without the customer noticing any battery ageing." That said, it is unlikely that the driver will regularly use a rapid charging station: "According to our research, the typical customer will complete about 85 percent of all charges using household connections, mostly by charging over the course of the working day, rather than using rapid charging." This therefore ultimately leaves a profile of less than 30 journeys per year for which rapid charging comes into question. Over ten years, that means we are looking at around 300 rapid charges.

A harmonised payment system for charging stations, regardless of the provider will surely come.

Jürgen Schenk

So, what about the problem of the numerous electricity providers and invoicing companies? Up to now, Germany is one of the big energy providers whereby the country is divided into small and large regions alike, in which each energy provider has developed their own payment methods. A harmonised payment system for charging stations, regardless of the provider, will surely come, according to Jürgen Schenk's prognosis.

Or better yet: "In the future, cars will pay for the charging current themselves, after having initially identified themselves at the charging station. The invoice will then be sent directly to the provider, which is assigned to the vehicle's identification number. One may think of it as roaming for electricity." Furthermore, while traveling, one will be able to reserve a charging station with the desired charging output using an app. What petrol station offers that kind of service?

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