Why we need both: “Fast Charging” and “Normal Charging”

In this first article of a small series about electric vehicle charging, I will explain why fast charging is overrated and we (also) need far more “normal charging.”

When I read the press in Germany these days about electric vehicles and charging, newspapers are full of “fast charging.” Everybody seems to write about how we need more fast chargers. The German government is even stepping in to make sure enough fast chargers are built off the beaten track so that people who do not live between say Frankfurt and Düsseldorf are also served. This focus on fast charging is also true for a number of other bigger countries in Europe, such as France, Italy, Spain, and others. 

Why does everybody seem to be so obsessed with fast charging? Is fast charging the future and “normal charging” will vanish into oblivion, at least in the public space?

Not so fast. Let us first start by defining what we mean by “fast charging.” Generally the term is used for charging powers starting at 50kW but can go up to 350kW, whereas “normal charging” generally refers 7-22kW (3.6kW or less from a household plug is usually referred to as “slow charging”). The range from 50-350kW is huge, since the maximum charging power has increased substantially over the last years. When the term was coined, the fastest charging power was usually 50kW or sometimes 100kW. Therefore, a new term has been invented to determine the upper range of fast charging: “High power charging” (HPC) which usually refers to 150-350kW. 

In the public opinion, the terms fast charging and high power charging are often used interchangeably, referring to the most rapid charging available today, and for the remainder of this article I will focus on high power charging. Now why is everybody so focussed on that “really fast charging”?

People, i.e. we, don’t want to change. Most of us in Europe and elsewhere have grown up with the gas station. We go to a place where we don’t really want to go to, but it only takes 5 min or so, and we pick up a magazine on the way. Already as small kids we accompanied our mum or our dad to the gas station, often receiving a chocolate bar conveniently placed close to the cash counter. That is what we are accustomed to. That is what we want to keep. And we believe that the “e-gas station” is the best substitute to that. And don’t get me wrong: I am completely convinced that we need the “e-gas stations” on motorways. I do not want to have to have a three hour coffee break when driving from Munich to Vienna. But in cities? Let’s have closer look.

Today’s cars are mostly limited to 100kW - 150kW (The fastest charging EVs today are in the range of 250 to 270kW). Therefore most cars will need about an hour to charge their batteries. Hang on. Why does it take a 50kWh battery close to one hour to be fully charged at 100kW? Should it not be more like 30 min? 

The battery management system only allows the battery to be charged at full power in a small range, and will then lower the charging speed to protect the battery from damage. This is also the reason why most EV makers’ information about charging time can be misleading (albeit not wrong). Typically, a statement would look like “from 0% to 80% in 40min.” However, you do not want to get your car to 0%, as you do not want to use the last drop of gasoline when arriving at a gas station. Also, depleting the battery completely damages it, so under normal circumstances you may want to keep the battery at least at 20% charged, ideally even more. And charging from 20% to 100% takes far longer than from 0% to 80%. So you want to wait for an hour until your car is charged again? I don't if I can avoid it.

Fast forward a couple of years and more and more cars will be able to charge quicker, granted. But even at 350kW, it will still take some 15 min or so to charge a 60kWh battery, for the same reason pointed out above. 15 min is not a problem on the motorway, where a break every couple of hours is advised anyway, but it is an inconvenience in the city. Not unsurmountable, but an inconvenience nonetheless. 

The other aspect about HPC charging is the immense cost of installation, which ultimately the user has to pay for. It is not so much the fast charging stations themselves, which are far more expensive than normal charging stations, but the cost of connecting to the grid. On the motorway, where HPC charging is needed the most, you may able to “plug into an overland electricity line” (its more complicated than that, but let’s stick to the principles). Also, you usually have enough space to put up the necessary infrastructure like the power transformers and inverters. 

In the city, things become more complicated: In the large majority of the cases, you cannot simply plug into the “normal" electricity line, i.e. lower tension electricity line which feeds city houses and lies below the pedestrian sidewalks. You need to connect to the “middle tension line”, and then transform and invert the electricity to meet EVs requirements. The large and expensive equipment required to achieve this needs to be installed somewhere, in an already crowded city quite a challenge. Underground? Good luck convincing the municipal engineering department. So you need to find a large enough private space for the charging stations and the other infrastructure. That is complicated enough but probably still doable when we talk about say 2 charge points of 150kW, but a whole different story when we want to built up a “e-gas station”, e.g. 10 charge points of 350kW. Even the free capacity at the middle tension may not be enough. Finally, chances are the middle tension line is not exactly where you intend to built up your “e-gas station”. Consequently, a lot of earth works need to be carried out to bring the cables to where you need them.

Let’s summarise: HPC charging is both necessary and doable on most motorways or overland roads, but it becomes far more complicated and hugely expensive in cities.

What is the alternative then? Very simple: Good old “normal charging”. In cities, the majority of cars are not driving most of the time, but are parked somewhere (an average passenger vehicle stands 95% of its time). Be it at home, at the office, when shopping, or going to the movies: The car is parked. So when it is possible to combine parking and charging, you can always “top up charge” your car. 

Let’s do a small example: You go to the movies. On average, you will stay for roughly two hours. You leave your car where you would usually park it anyway and just plug into a charge point. At 11kW charging power, you can increase your battery state of charge by 22 kWh (2hx11kW). Suppose you have an ID.3 with a battery of 58kWh net, if you started at say 40% state of charge (23kWh left), you get to 45kWh or almost 80% state of charge. This is cheaper, better for your battery, and more convenient since you charge where you want to go anyway. The “only” requirement is a charging station right where we need it, and that is mostly not the case today. 

Have a look at the Netherlands, which is arguably way ahead in electro-mobility. Amsterdam has less than 900k inhabitants and 4,500 public charge points. Munich has 1.4m inhabitants and 1,200 public charge points. Berlin has 3.6m inhabitants and 1,000 public charge points. Sounds strange? Well, I believe that the Netherlands have understood that it is the mixture of different charging options which is needed. HPC charging on motorways, and a very dense network of normal charge points in the cities.

Amsterdam plans 18,000 public charge points by 2030. Munich intends to add another 2,700 within the next up to 7 years, which would bring it to 80% of Amsterdams 2021 level, at 50% larger a population. Berlin? Working on a plan. We are curious to see.

We can discuss how large exactly that number in each city needs to be. But in my opinion, it is clear that we will need thousands and thousands more in each of those cities. Let’s get started.