The world is entering a period of rapid buildout of EV charging infrastructure. Average total cost of EV ownership is falling below that of comparable internal combustion vehicles while EV adoption rates continue to trend upwards.  Expect to see more and more electric vehicle chargers in parking lots and gas stations.

Porticos has broad experience in the engineering design of electric vehicle chargers.  In this series of posts we’ll explore the intricacies of electric vehicle chargers from the perspective of new product development.

Electric Vehicle Chargers, commonly called Electric Vehicle Supply Equipment (EVSE), are the fuel stations of the burgeoning electric vehicle economy.  Explore an urban parking deck and you are likely to find a row of commercial charging stations. Unlike traditional gas pumps, they require little infrastructure.  There are no buried fuel tanks, piping networks, or weekly tanker deliveries.  All that is needed to install an EVSE is electrical service.

“It would be reasonable to suppose that an EVSE must be a much simpler device than a gas pump. The truth of the matter is that they are rather complex, with a unique set of engineering challenges.”

-Kevin Carpenter, Co-Founder, and CTO of Porticos. Tweet

What is an EV Charger?

Using car power charger
User holding a SAE J1771 (Combo 1) connector. Photo credit dcbel.

In simplest terms, an EVSE provides electrical power to EVs in order to charge their onboard batteries.

At low charging rates, EV Chargers act as a switch that allows 120, 208, or 240V AC power available in a home or commercial site to pass to the EV. Since batteries must be charged with DC, the EV then performs AC to DC power conversion with its on-board charger (OBC). In this situation, the main function of an EVSE is to safely manage when power is available to the EV, ensuring the connector is not energized when it is being handled by a user or when electrical faults occur.

At higher charging rates, EVSEs negotiate charging rates and perform the AC to DC power conversion in addition to the safety functions stated above. Along with these core functionalities, EV chargers commonly have energy meters, indicators or displays to inform the user of the state of the device, as well as wireless communications to relay performance data and facilitate billing.

Terminology

Before too many details are discussed, it would be wise to establish common terminology for some pieces of charging hardware. Luckily, the European Automobile Manufacturers Association has standardized on the following terms:

Terminology for common electric vehicle charging station parts. Terminology as defined by ACEA
Terminology for common electric vehicle charging station parts. Terminology as defined by ACEA.

Charging Standards

There are two major standards for charging EVs with cables. SAE J1772 governs North America, and IEC 61851-1  governs the EU, with most of the rest of the world employing a mixture of the two. The exceptions are China and Japan who have developed their own standards.

These standards control the physical layout of the connector and vehicle inlet, the electrical safety strategy, the communications protocol between the EV and EVSE, and the overall performance of the system.  Of great interest to the consumer is the last piece, as this defines the charging speed of each standard.

For SAE J1772, AC Level 1 represents charging by plugging a portable EVSE into a standard North American electrical outlet. AC Level 2 represents charging through a 240V outlet, commonly seen as oven, dryer, or water heater connections, using a portable or permanent charger. These connections, while convenient, are rather slow, requiring several hours to add appreciable range to an EV. Coupled with their low cost, AC Level 1 and 2 charging is ideal for residential locations where charging can occur overnight. DC chargers require more power than typical residential service can provide, and are also cost-prohibitive.

The table below details the various types of charging defined by the SAE and IEC standards, as well as how they translate into real-world charging rates for two modern EVs.

Standard: SAE Level, or IEC Mode: Current (A) Voltage (V) Power (kW) Charge Rate, mi/h, 2022 Ford Mustang Mach E, Base Charge Rate, mi/h, 2022 Nissan Leaf Plus
SAE J1772 AC Level 1 12 120 1.44 4.9 5.8
16 120 1.92 6.5 7.7
AC Level 2 80 208-240 19.2 36* 27*
DC Level 1 80 50-1000 80 270 323
DC Level 2 400 50-1000 400 389** 404**
IEC 61851-1 Mode 1: AC Single Phase 16 250 4 14 16
Mode 1: AC Three Phase 16 480 11 37 27*
Mode 2 AC Single Phase 32 250 7.4 25 27*
Mode 2: AC Three Phase 32 480 22 36* 27*
Mode 3: AC Single Phase 63 250 14.5 36* 27*
Mode 3: AC Three Phase 63 480 43.5 36* 27*
Mode 4: DC 200 400 80 270 323
Megawatt Charging System (MCS) *** TBD 3000 1250 3,750 n/a n/a

* While many AC charging standards are capable of delivering more power, the Mustang Mach E onboard charger is capable of charging its battery at a maximum of 11kW. The Nissan Leaf onboard charger can charge at 6.6kW.
** The maximum charging rate is 115kW for the Mustang Mach E and 100kW for the Nissan Leaf Plus. Their batteries cannot handle this rate for long, however. Average charging rates are around 200mi/h over a one-hour span for both vehicles.
*** MCS is an emerging standard being developed by the CharIN electric mobility non-profit primarily for charging heavy-duty vehicles such as semi-trailer trucks, busses, and municipal waste trucks.

The above standards dictate the use of the following connectors:

Drawing of J1772 (CCS1 Combo) connector, with labeled pinouts. This is a view facing the end of the plug.
SAE J1772 (Combo 1)

Mliu92, CC BY-SA 4.0, via Wikimedia Commons

Male plug for CCS Combo 2, based on IEC 62196-2 Type 2 extended with high voltage DC connectors.
IEC 62196 Type 2 (Combo 2)

Mliu92, CC BY-SA 4.0, via Wikimedia Commons

Both connectors feature upper zones with pins responsible for communications and AC charging, and optional lower zones dedicated to DC charging. When the DC pins are included, these connectors are commonly referred to as Combo 1 and Combo 2 connectors.

As mentioned above, electrical safety, power electronics, user-centered design, and wireless communications are just a few of the many topics we will cover in detail in future posts. Be on the lookout for these to appear in the coming months, and please reach out to Porticos for answers to all of your EV Charger development questions!

About Porticos

A WORLD OF OPTIMIZED PRODUCTS

About Porticos — Porticos, Inc. is a mechanical engineering and product design development company located in Research Triangle Park, NC.

Established in 2003, Porticos continues to produce innovative and effective solutions for its clients and the markets they serve. Porticos, Inc. provides mechanical design, analysis, research, and development services to clients including Dell, Motorola, Raytheon, and many others.