An EV Charging system discernment – electric cars without On-Board Chargers? • EVreporter

To represent Electric Vehicles (EVs) as equivalent to conventional combustion vehicles, the industry must find a way to ensure that the energy refilling process in EVs is as comparable to the normal fueling process. Refilling time, distance per refill (range), and refilling infrastructure availability are crucial for EV acceptance since conventional vehicles offer quick refill and abundant and efficient infrastructure in place. Battery capacity and range limitations put further focus on the ease and accessibility of charging.

Modes of EV Charging

Let’s try to understand how charging takes place in an EV. EV batteries are charged using Direct Current (DC). Since the Grid input is AC, intermediate circuitry is used to convert input AC to DC either using an Onboard Charger ECU sitting inside the vehicle or an External Charging Station which converts AC to DC externally and supplies DC to the vehicle. As per regulatory bodies, modes of EV charging can be classified as:

Mode 1 Charging: Charging is performed directly from a standard socket outlet without any additional installation. This enables EV users to charge the vehicle
literally from anywhere the AC supply network is present. Though it promises convenience, inherent safety issues related to Mode 1 and Slow charging made it
less appealing, and many countries have already put a restriction on the usage of Mode 1 Charging.

Mode 2 Charging: Charging is performed from a standard socket outlet using a charging cable integrated with EV Supply Equipment. EVSE integrated with the
cable establishes communication between EV and EVSE and provides synchronization on charging parameters, and provides electrical safety. By legislation, Mode 2 charging is also restricted in public areas and under stringent restrictions for private charging as well in many countries.

Mode 3 Charging: Charging is performed from a dedicated charging box which is attached to Main AC permanently having safety and control functions. High power charging can be achieved using this wall-mounted circuitry box which still supplies AC to EV, and the Onboard charger converts this AC to DC and charges this vehicle.

Mode 4 charging: Charging is performed using external DC EVSE, which converts AC to DC and supplies DC directly to the vehicle bypassing the onboard charger. This enables high-speed charging compared to AC charging with protection and control functions.

Charging from a standard socket outlet has almost been ruled out by the electric car industry and wall-mounted AC chargers and fast DC chargers are predominant.

Emerging solutions with wall-mounted DC charging:

Mode 1 & 2 charging methods are fading out given strict safety regulations, while Mode 3 and 4 are set to become the central pillars for the charging process. This can be a nudge to OEMs to rethink the future architecture in a way that “Do Electric Vehicle still need On-Board Charger (OBC)?”. This radical architectural change may raise concerns along with the potential benefit it can bring up. Let’s look at the proposed architecture and get some perspective.

As we can see from the above image, OBC is moved out of the EV and it becomes a part of the Wall mounted charger. The question arises – ‘How convenient the conversion from wall-mounted AC chargers to wall-mounted DC chargers will be’? Since wall-mount DC chargers (up to 25kW or 30kW power output) are not dealing with high power as High Power DC Fast Chargers, in terms of cost, installation space, and design complexities wall mounted DC chargers are not very far from AC Charger design. Already low-power residential wall-mounted DC chargers with reasonable pricing are available on the market – (SunAP EcoPower, Delta Electronics, Powertron India Private Limited, VrajEV etc). For electric 3Ws, Exicom is offering lower output 6kW/9kW wall-mounted DC chargers.

Also, Wall mounted DC chargers provide the same communication and safety functions as type 3 AC charging and fast charging DC stations eliminating any
functional discrepancies or extra effort needed due to the architectural change.

At the same time, shredding out one ECU from EV can have a significant boost for OEMs in terms of:

• Reduced development effort and complexity
• Quick time to market
• Reduced cost per EV

Also, wireless charging is starting to make a huge business impact and can expect dominance in the charging Ecosystem in the near future. As the saying “once something becomes wireless, there is no coming back to wires”. This calls for an additional ECU to handle wireless charging functionalities. Shredding out the OBC can be a tactical move for OEMs so that wireless charging capability can be incorporated comparatively easily, as when the industry evolves to that stage.

About the author

Sreeraj Arole is an automotive professional with 11+ years of industry experience and currently working with Wipro Limited, engaged in the EV charging domain as an EV Solution Architect.