An electric vehicle contains many sub-systems that need to inter-operate so the vehicle can function as intended. These disparate systems range from the battery string, comprising Lithium-Ion modules to various drive systems, converters, auxiliary modules, and charging and monitoring systems. As a result, choosing the right connector for each in-vehicle application is essential to a reliable vehicle.
Given the safety implications associated with vehicles, both for the driver / passengers and other road users, it is not surprising that many standards and automotive-specific requirements exist. Electrical safety is one key point, such as the use of a High-Voltage Interconnect Loop (HVIL) to shut the system down as a hazard develops. Other more basic protections such as ensuring high voltage connectors cannot be touched are important, especially for mechanics working on the vehicle. Other automotive requirements include contact position assurance (CPA) / terminal position assurance (TPA) and secondary locking of the connector assembly.
The trade-off between safety and cost
Improving safety is essential and a constant quest for designers, but this often leads to longer development cycles, with higher costs – as well as the potential for more expensive components (such as connectors) being required. Correctly assessing the needs at an early stage can ensure that costs are kept to a minimum without safety being compromised. Key considerations for designers include:
· What are the basic electrical requirements (current and voltage)?
· Will a locking system be required for safety or vibration?
· Does the connection form part of the service process?
· Is keying required to avoid potentially hazardous mis-connection?
Establishing answers to these questions will go a long way to defining the connector type that will meet the needs of the specific application.
However, apart from the basic operational and safety requirements, there are more considerations that will shape the decision and selection process. Many modern electric vehicles are very densely packed, so the available space may be small. The demand for ever higher efficiency in vehicles means that the weight of every component (including connectors) is under scrutiny.
As the market for electric vehicles grows, so does the number of available options, giving designers a huge choice. However, as the market remains in a relatively early stage, relevant standards are few and far between, making the choice challenging.
A broad range of connectors with significant options
One supplier with an extensive range of connectors for electric vehicles is Amphenol. Most of its products are based on the company’s RADSOK technology, which guarantees coverage up to 65% of the contact surface area. Its comprehensive range offers multiple options allowing the designer to select the right product for their own individual application:
· Electromagnetic shielding can be selected to cover individual contacts or the entire connector.
· Sealing / ingress protection is available up to IP6K9K when mated which keeps fingers out as well as dirt and moisture that could be a source of failure.
· Additional interlocks and / or secondary locking ensure connectors remain mated.
· Optional keying and colour variations are available to ensure connectors are not mis-plugged.
· Products such as the PowerLokseries offer choices of up to four poles as well as metal and plastic housings, coding configurations and colour options.
· For high current applications such as electrical distribution, drive systems or motor control connectors are available from 2.8 mm to 14.0 mm diameter, giving the ability to safely handle currents up to 650 A. The Manual Service Disconnect (MSD) series provides an additional level of safety, especially for the distribution box.
Shock and vibration resistant solutions
One of the most rugged products on the market is the Imperium High Voltage / High Current (HVHC) connector system from Molex that is able to withstand more heavy shocks and vibrations than any other available product. Currently available in diameters of 8.00 mm and 11.00 mm, new configurations are being developed to broaden the range as well as to demonstrate how customer-specific requirements can be met by repackaging.
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Figure 2: Imperium High Voltage / High Current (HVHC) connector system from Molex
As things are evolving so rapidly in the electric vehicle space, there are few, if any, standards for connectors. In Europe, the most common charging connector is the Mennekes (Type 2) plug that is covered by IEC 62196-2 & IEC 62196-3. This plug is used to charge the Tesla electric vehicles and is available as part of Amphenol’s HVCO series.
The majority of today’s electric vehicles are in Asia. Here a bidirectional charging standard known as CHAdeMO is the most popular and products from manufacturers such as JAE are compliant with this standard.
JAE’s KW01 and KW02 series are rugged and highly reliable solutions with rust resistant contacts, and a flame-retardant and weather-resistant resin housing and cable. Both series can be supplied as complete cable assemblies, giving OEMs a turnkey solution. The KW02 also allows energy from the vehicle battery to supply power to the home when plugged in – the so-called ‘Vehicle-to-Home’ (V2H) standard that allows users to reduce energy costs by using energy stored in their vehicle at peak times and then recharging when demand is lower.