High Power Charging for EV’s
How to innovate mobility with technologically leading products
Electromobility is old hat. Even the very first motorized vehicles had an electric motor. The challenge then as now: How can I get as much energy as possible into the mobile energy stores as quickly as possible?
As early as 1881, the Frenchman M. Gustave Trouvé presented his sensational tricycle – 12 kilometers per hour fast and quite similar to a stagecoach. With a range of about 14 kilometers, the vehicle was almost suitable for everyday use, because at that time the competition on the long distance was only the horse. Werner Siemens, Andreas Flocken, Ferdinand Porsche – the list of e-pioneers is long and contains amazing names. Between 1896 and 1939 there were 565 different brands of electric cars worldwide. In New York, the share of electric vehicles was 50 percent in 1901. The rest were steam cars or naphtha, acetylene or compressed air driven vehicles. Even Henry Ford developed a Ford Model T with an electric motor, which, however, did not go into series production. What followed was almost 100 years of electric mobility at a standstill.
Electromobility takes off
At the beginning of the 21st century, several major automobile groups dared to enter the market with electric models – electric vehicles thus received a new development boost and public attention. A good 10 years ago, the subject of e-mobility really took off when the first vehicles with longer ranges were presented. When Phoenix Contact entered the e-mobility market, the initial focus was on individual components. The first customer-specific connectors with combined signal and power transmission for charging electric vehicles were developed in 2009. As early as 2010, AC charging sockets for Chinese charging station manufacturers were built and delivered in large quantities. In 2011, there were applications with large volumes in the commercial vehicle sector. Electric buses in China used heavy connectors to change large batteries. In the depot, the discharged batteries were automatically replaced with charged ones in order to optimise the utilisation of the buses. To this day, heavy connectors for exchangeable batteries are used in Chinese buses.
In the early days, electric cars were mostly charged with alternating current. In order to achieve higher charging capacities and shorter charging times, especially in the public sector, it became necessary to standardise a solution for DC charging. Together with leading automotive manufacturers, Phoenix Contact developed and defined a worldwide charging standard for combined AC and DC charging (later Combined Charging System, CCS). CCS proved to be safe, flexible and practicable and in 2014 became the recognised standard for vehicles and public charging infrastructure in the European and American markets. (picture 3)
But the demand for faster charging times also for passenger cars became increasingly louder. The first pre-developments took place at the beginning of 2015. Developer Dirk Moseke from Phoenix Contact E-Mobility has accompanied the further development of the CCS standard almost from the very beginning and here he describes in his own words how the next steps proceeded:
“Of course, there were also specifications and standards in development. But there was nothing. And that was only two years ago! So we had to develop it ourselves. What do we have to do to get something completely different out of the already existing CCS standard with the defined mating face?
200 amps were no problem, but now 300 amps and more are required. Today we’re at 500 amps. There would be a yellow sign in a building in front of the access to such currents saying “Access prohibited”. And this is where we have to make the facilities freely accessible, exposed to the weather and possible abuses.
The first point was the development of suitable cables. With such currents, there are only two possibilities: larger cable cross-sections or significant heating. However, the cable must not become too thick, otherwise it becomes too heavy and stiff. So we have devoted ourselves to the subject of heat generation. The first task was to determine where the heat actually originated. In fact, it’s the wire itself that gets warm. However, the heat can also come from the vehicle, i.e. from a point that we cannot influence at all. The next thought was to cool with liquids. This means to rinse the copper directly with a heat dissipating medium. We rejected an oil-based solution, because it was far too complicated to handle – and anything but innovative.
Research and development working side by side
Next, we tried air cooling. To do this, we blew air into tubes containing the hot cables. But the air had to go somewhere and then came out in the connector again. In addition, air does not absorb heat so quickly. Our result: Not practical. So we did some more research on alternative coolants and ended up with the easy-to-handle and environmentally friendly glycol. In addition, we have used heat-conducting paste in the cable. This even worked partially, but was not suitable for series production. In the meantime, we had also discovered that it made sense to make the surface as large as possible. More surface area means better heat dissipation. So we did experiments with a lot of single strands. It partly looked as in a knitting room here, with shrink tubing, cable ties and duct tape. Basic research as it can also be found at any university.
Today we have a cable that leads two 25 mm2 copper wires twice – two for plus, two for minus. This ensures that the cable is not too heavy but nice and flexible. We have built a layer into the outer sheath that shows when the cable is worn out or damaged. In addition, the cable must not become hotter than 60 degrees so it can be enclosed – according to the standard. This is monitored by sensors and is coupled with a switch-off device. In addition, communication wires run through the cable, which the connector needs in combination with the column. The next challenge was the connector itself. First there was the requirement that we should cool the inlets via the cable. You can’t do that. This would resemble a refrigerator, which cools the beer in front of the television through its open door.
The most innovative system worldwide
We developed a heat sink, which initially consisted of a turned copper tube, which was encapsulated and to which the hoses were connected. This also worked, but was again very expensive to produce. Today we have a heat sink that encloses an insulating body. This way we cool down to the contacts.
All sealing points had to be perfect for the tests on the prototypes. 13 or 14 sealing points, some in delicate material compositions and equipped with leakage sensors. We have tested various materials in our own test laboratory, especially for their conductivity. Of course no manufacturer will tell you,but This was an enormous effort. Today we measure and monitor the temperature at the hottest points of the transmission, right in front of the contacts. In this way, we protect our entire system from external influences, for example from the vehicle side. This is currently the most innovative system in all e-mobility. We have patented the real-time temperature measurement. There is a locking system that prevents the vehicle from starting when loading. If the plug is dropped and damaged, it does not need to be completely replaced. We have made the frame of the mating face interchangeable. This makes maintenance cost-effective and flexible.
From the manufactory to the series
Then we developed the pre-series tools in cooperation with our tool shop. In some cases, we dared to use technologies that were completely new to us, such as ultrasonic welding of the copper cables to the contacts or casting of the DC contact area. The development of this production of highly complex components continues to be a challenge, as growth continues unabated and stormy. In pre-production, a connector took two days to manufacture. It’s like a manufactory. Meanwhile we are with real series production. The dynamics of the development of e-mobility became apparent after the presentation of our first samples at the beginning of 2018. At times, customers simply placed their orders without even inquiring about the price. (Fig. 5)
Innovative participation in shaping mobility change
At the end of 2018 we had the start of series production of our HPC connectors. At the same time we develop solutions for the international markets, where sometimes completely different standards prevail. 500 amps are future-proof in terms of performance today. But of course we are constantly working on optimizations. It’s more than just a connector. There’s so much intelligence in it that makes it really safe to deal with. And topics such as remote maintenance, charging cable routing – we are in constant exchange with the charging column manufacturers. So we’re not running out of tasks.”