Electronics and Semiconductors

Overview: EV types and their infrastructure and charging requirements

26 May 2021
A queue of EVs being charged from external power source. Source: Adobe Stock

Electric vehicles (EVs) have been around for a long time. However, new battery systems, charging technologies and vehicle designs have recently reshaped this segment of an automotive market that is still evolving. EVs denote any licensed road vehicle driven in part or full by electric motors that are powered by an external source via a plug, such as an array of batteries. Included are vehicles such as vans, cars, small buses, two/three-wheeled vehicles, small trucks and quadricycles (micro vehicles).

Types of EVs

At a broad level, EVs are classified as battery-electric, extended-range electric and plug-in hybrid electric. A battery-electric car, or a pure EV, is driven by a battery-powered electric motor that requires an outside power source for charging. Extended-range EVs also achieve all of their total motive force from an electric motor. These vehicles also rely on an internal combustion engine that automatically starts operating to produce the power needed over the battery range; the vehicle’s wheels never run straight from the internal combustion engine. Extended-range EVs often feature smaller battery packs than are found in full-sized battery-powered EVs.

The plug-in hybrid EVs feature both an electric motor and internal combustion engine. The batteries can be charged from an external power source and the vehicle can cover many miles with that electrical power alone. Plug-in hybrid EVs should not be confused with hybrid EVs that are not plugged in. When compared in terms of size, plug-in hybrid EVs are smaller than the other types, and thus, have fewer kW of available power.

EV charging requirements

Direct current (DC) power is always used to charge the batteries of EVs. However, the power provided by the grid is alternating current (AC), which has to be converted into DC before being delivered to the batteries. In the case of an onboard charger or AC charging point, the AC power is transformed into DC power by the apparatus present in the vehicle. Size and weight constraints also make it difficult to have a charging port in the car. Therefore, a DC charging point transfers AC power to DC power within the charging point, and thus eliminates the need for a charger inside the vehicle. The DC charger is not constrained by size or weight and is better suited to handle large charging currents and charging time can also be reduced. Because of this, the DC charging point is bigger and more costly than the AC charging point.

Charging infrastructure requirements

The EV charging system has four BS EN 61851-1 standard types referred to as “Modes.” Mode 1 has a socket outlet and a non-dedicated circuit. It is straightforward as the plug needs to go in an already present socket outlet with no in-cable control container. However, it is not recommended to use this mode for charging an EV as all the socket outlets cannot guarantee residual current device (RCD) protection to prevent shocks. And, if the homeowner does have RCD protection, there can be some places in the house where this protection is not present.

The Mode 2 charging infrastructure utilizes a standard socket outlet with the cable carrying an in-cable control and protective device. This cable is present between the socket outlet and the EV, offering charging power and RCD protection. Mode 2 can prove to be a good charging infrastructure for certain types of EVs, for example, for those with moderate charging needs like a few plug-in EVs and two-wheelers. Few vehicles may be fitted with a Mode 2 cable, while other vehicles may also offer the Mode 3 cable option. Mode 2 is also essential as a backup mode for compatible vehicles in areas without separate charging points.

In Mode 3 charging system, there is a dedicated AC socket outlet that uses the car’s onboard charging system. Smart charging and other features are added in such charging points, in addition, for protection, communication and control systems. Mode 3 charging systems are developed exclusively for the charging of EVs and have an individual dedicated circuit, and are ideal for commercial, public and residential applications. Such charging points operate on a specific protocol to permit the vehicle and charging point to communicate while being charged. Looking into the future, Mode 3 is most advantageous for charging battery-powered EVs at homes as they are likely to offer many smart features.

Mode 4 charging systems have dedicated connectors. They deliver DC power at the output, and the charger is incorporated into the charging point. It is also the main difference between Mode 4 and Mode 3 charging systems, as the latter utilizes the on-board charger of an EV. Mode 4 charging points can supply high power such that a vehicle can take about 15 minutes to charge up to 80%.

Conclusion

New developments promise easier and faster charging for EVs. For now, Mode 3 charging systems are an all-rounder as they can be used both for commercial and residential applications. Mode 4 cannot be used at homes because of large capital expenses and complex electrical network infrastructure requirements.

To contact the author of this article, email engineering360editors@globalspec.com


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