Connector Solutions for HEV/EV Charging Systems
HEV/EV charging system technology presents some of the most dynamic engineering challenges in the current global market. The ongoing quest for greater vehicle range and shorter battery recharging times present exciting challenges to companies in the field.
Connector Solutions for HEV/EV Charging Systems, by ODU USA
The hybrid electric and electric vehicle (HEV/EV) market has been rapidly evolving since the first mass-produced models became commercially available in the 1990s. Current market evolution is primarily driven by two key factors: increasing vehicle range and facilitating shorter stops at charging stations, by either swapping a vehicle’s discharged batteries with a fully charged set or through faster charging technology.
The Charging Interface
The rate at which batteries can be recharged depends on the applied voltage and current, both of which are constrained by the physical characteristics of the recipient battery. As such, connector technology has evolved alongside vehicle and battery technologies to deliver the higher voltages and currents necessary to facilitate faster charging.
In a move that has at least somewhat hindered market-wide evolution, different regions of the world have adopted different connector standards to fulfill these ever-changing changing needs. The current variety of connection types that comply with international standards is summarized in Table 1, save for Tesla’s Supercharger port, as the company chose to develop its own port capable of delivering up to 120kW at a time when none of the standard ports could deliver more than 62.5kW.
In order to enable SAE J1772 compliant North American charger systems to be used with Tesla vehicles, Tesla selected ODU-USA to completely redesign the Tesla J1772 adapter. The new design featured TURNTAC contact technology, which offers a rated life expectancy exceeding 10,000 mating cycles, an insertion misalignment tolerance up to 5°, stable connections, and low disconnection force.
The continuing trend towards charging at higher voltages and currents has also introduced a new challenge: heat. Even the most conductive cables and connectors experience some electrical resistance at normal operating temperatures, resulting in at least marginal energy loss in the form of heat.
To address this issue, HUBER+SUHNER developed the RADOX HPC high-power charging system, which incorporates an integrated liquid-cooling system that enables the delivery of up to 400kW in anticipation of next-generation battery technologies currently under development. These super-fast systems are capable of providing an 80% battery charge in as little as 15 minutes, and actively cool both the cable and connector, which enables the use of much smaller cable cross-sections than uncooled fast-charging systems and, in turn, provides greater cable flexibility, lighter weight, and easier handling. HUBER+SUHNER also selected TURNTAC contacts for its ports, which are compatible with both North American and European CCS connections.
Battery charging time is much less critical than overall system cost for home battery charging systems, as most HEV/EV owners simply plug in their vehicle at the end of the day and wake up to a fully charged set of batteries the next morning. This market segment is also much higher-volume than the high-power commercial charging station market since there are about as many home charging systems as there are HEV/EV owners. As such, home charging systems typically use lower power, non-CCS ports that utilize more economical high-lifecycle contact solutions than commercial charging ports.
Battery swapping as a commercial-level HEV/EV charging solution for personal vehicles was ultimately rejected by many vehicle manufacturers (including Tesla’s Elon Musk, who was originally a proponent of battery swapping for this market) in favor of developing increasingly fast charging systems. However, this solution has proven both efficient and cost-effective for heavier-duty HEVs/EVs, such as light trucks and limousines. This market is widely served by custom connectors that offer axial and radial tolerance compensation of ±5mm, high vibration absorption, and EMC damping for ampacity greater than 300A.
In China, which is leading the way in charging systems capable of delivering greater than 120kW, the battery-swapping trend has infiltrated both the personal and commercial HEV/EV markets, but this trend may be short-lived due to the widespread deployment of fast and superfast charging stations throughout the country. By the end of 2016, there were already more than 150,000 such stations, and that total is expected to rise to 800,000 by 2020.
Connectors for HEV/EV applications aren’t limited to the charging interface. Multiple batteries must be interconnected within these vehicles, and the entire battery bank must be securely and reliably connected to the vehicle’s electric drive system. These applications often employ customized two- and three-pole connectors capable of high current transmission (e.g., up to 160A at 85°C or 200A at 125°C ambient temperature), providing high levels (e.g., 65dB) of electromagnetic shielding and robust (e.g., IP69) environmental sealing, and withstanding considerable levels of vibration.
HEV/EV technology is one of the most dynamic engineering fields in the current global market. The ongoing quest for greater vehicle range and shorter battery recharging times present exciting challenges to companies in the field. Looking ahead, we can expect to see deployment of docking stations that will fully automate the process of plugging ultrafast chargers into personal vehicles, so drivers never even have to exit their cars if they don’t want to. As ultrafast chargers become capable of delivering up to 600kW — a feat that’s projected to come to fruition within the next five years — a full charge could be achieved in as few as 10 minutes. Additionally, as self-driving cars proliferate over the coming years, vehicles may even decide when and where to go to recharge.
Much of the necessary technology for these and other HEV/EV advancements already exists, so it will be exciting to see and continue to support new vehicle and connector technologies over the next 15 years and beyond.