Requirements of EV Charging
While EVs can charge at the home, from a regular domestic supply, this is slow – and best-suited to overnight charging. Instead, many drivers want to charge much faster, and this requires the use of high-power DC charging stations, capable of charging an EV in less than 30 minutes.
As well as safely meeting the electrical requirements of handling such large currents and voltages, there’s also a need for effective thermal management to handle the heat produced.
Reliability is essential, as drivers expect to always find a working charger. The EV charging infrastructure must function well in harsh environments, particularly in high temperatures in hotter climates, as well as sub-zero conditions elsewhere. With chargers often in relatively remote locations, the cost of sending a maintenance team to handle a repair is significant – hence operators want to minimise any problems.
Standardisation is key to meeting these goals. For vehicle charging today, one widely-adopted standard is ISO 15118, which enables efficient bidirectional communication between EVs and charging infrastructure, optimising charging efficiency and enabling vehicle-to-grid integration. ISO 15118 supports both AC and DC charging, including high power DC charging.
High voltage connectors
As EVs demand more power for longer ranges, high voltage connectors play a vital role. These connectors ensure safe and efficient power transfer in compact spaces, thus enabling fast-charging capabilities, and reducing wait times at charging stations.
DC charging stations can supply high voltages of 300V to 750V DC directly to a vehicle’s battery (bypassing the vehicle’s own on-board charger), at up to 400A. This requires a three-phase AC input from the grid, and cannot normally be powered from a domestic building.
Connector vendors such as Molex and TE offer power connectors that can handle high currents at the voltages involved in EV charging. For example, TE’s ERNI PowerElements connectors are rated at up to 500A, which means they can handle the 400A required for the highest-power charging mode defined by the IEC 61851 standard2.
Looking ahead, more vehicles will use 800V batteries, increasing the possible charging speed compared to today’s more common 400V. Moving to 800V also enables the use of lower currents, and therefore thinner and lighter-weight cables.
Data connectivity
It’s not just about delivering power to a vehicle – with the rise of smart charging stations, data connectivity connectors are becoming increasingly important. They enable real-time monitoring, diagnostics, and remote management, so that operators can resolve any problems quickly, and can provide the best possible charging experience for the user.
Data transfer must be secure and reliable, so a vehicle can identify itself to the charging station, and automatically start the charging process.
A broad range of connectivity technologies are in use at charging stations, including industrial standards such as MODBUS, MBUS and RS485, as well as power-line communication (PLC) over the main power cable. Wireless communication, such as 4G and Wi-Fi, is another option.
Locking connectors ensure reliable connection for data signals. For example, Molex’s Molex Easy-On FFC/FPC connectors have a dual-contact arrangement that ensures secure mating, while the lock-nail mechanism provides good cable retention.
Heat management
EV charging can generate significant heat. The faster an EV is charged, the more heat regulation is needed, as high currents generate a substantial amount of heat due to the internal resistance of the cable and plug.
This makes products like heat shrink tubes essential. They provide insulation, protect cables, and ensure safety during the charging process. Careful mechanical design is also required, with forced air cooling likely to be necessary in some hotter climates.
Today’s high speed charging stations are already outputting power of up to 350kW, and power delivery of more than a megawatt is not far away – although probably more likely to be used for trucks than for cars. With this kind of power, heat dissipation can be a major problem, and solutions such as liquid-cooled cables are being employed for effective thermal management. Employing liquid cooling means the cables can be lighter and thinner, reducing the cable’s weight by around 40 per cent compared to an uncooled cable.
Heat dissipation can also be reduced by improving efficiency, with new silicon carbide and gallium nitride devices enabling power losses to be significantly reduced.
Harnessing solar energy
With a push towards green energy, many charging stations are now integrating solar panels. At home, the extra power from a roof-mounted solar panel, connected via a suitable inverter, can substantially increase the speed of charging an EV. Solar in-line fuses, coupled with IPE OFF-board cable harnesses, are enabling solar energy to be used efficiently and safely.
Companies with large fleets can roll out solar power on a bigger scale. For example, at Utrecht in the Netherlands, a shade roof made up of 2,160 solar panels has been installed on a car park, enabling up to 500 charging points3.
As charging standards add support for bi-directional charging, this means that the charger’s solar panels and the car’s battery can feed energy back to the supplier, known as vehicle-to-grid (V2G).
Conclusions
The EV charging landscape is undergoing a radical transformation. To ensure the shift to EVs continues quickly enough to meet our net zero targets, consumer acceptance is vital. This means that charging an EV needs to be as convenient as refuelling with petrol or diesel.
As we transition to a world where electric cars dominate the roads, IPE OFF-board products are ensuring that this journey is efficient, safe, and sustainable.
1https://www.acea.auto/figure/charging-point-deployment-versus-sales-of-electrically-chargeable-cars/
2https://www.avnet.com/wps/portal/abacus/resources/article/next-generation-pcb-mounted-relays-in-ev-charging-systems/
3https://www.avnet.com/wps/portal/silica/resources/article/the-ins-and-outs-of-vehicle-to-grid-charging/
