Charging a Plug-In Vehicle

April 6, 2023

Most people call the EVSE (Electrical Vehicle Supply Equipment) a “charger”. In reality, it is an expensive extension cord used to deliver AC power safely to a plug-in vehicle. To make this more readable, any vehicle that can be plugged in we will call an EV. Simply put, EVSE is a protocol to keep owners and their electric vehicles safe while charging. Using two-way communication between the EVSE and the on-board charger in the EV, the correct charging current is set. As part of the protocol, a safety lock-out exists, preventing current from flowing when the EVSE is not connected to the on-board charger located in the EV. If the cable is not correctly inserted, power will not flow through it. The EVSE can also detect hardware faults and disconnect the power to prevent battery damage, electrical shorts or worse still, a fire.

When an EV is plugged into the grid (AC outlet) at Level I and Level II, the grid is supplying AC current to the onboard charger and the onboard charger provides DC power to the HV battery. That cannot be done without changing it from AC to DC, therefore the onboard charger is a type of power supply.

What is meant by Level I, II and III charging?

Level I

This is a Single Phase Alternating Current (AC) EVSE device using grounded receptacles at the most commonly available voltages and currents. In North America this typically means 120V/16A using a standard home grounded outlet. The Society of Automotive Engineers (SAE) J1772 standard is the document that is used for Level I and II charging. A Level I EVSE comes with the EV, although a few OEMs sell the Level I EVSE as an option. A Level I EVSE is sometimes called a “trickle charger.”

Level II

Level II is a Single Phase Alternating Current (AC) EVSE device at 208-240V that can supply up to 80A. Most Level II EVSE seldom deliver more than 45 amps. To “future proof” your shop, consider a Level II EVSE that is rated up to 80 amps. These can be permanently fixed to the building or may have a 240 plug of some type that can be plugged in as needed. These Level II EVSE are installed at homes, businesses and should be at your shop. It is also called a “destination” charger.

Level III

This is a specification that is “not in use.” It was an SAE level that used high levels of AC voltage and current to “fast charge” an EV. To do this the EV needed a powerful onboard charger. The purpose built “DC fast chargers” were a better idea. To be technically correct make sure you do not refer to a “DC Fast Charger” as a “Level III.” Those with a high level of training will recognize that you have studied well, as you know the proper terminology.

DC Fast Charging

There are currently three types of DC Fast Chargers (DCFC) in use. No longer are we changing AC to DC as in Level I and Level II EVSE systems. DCFC can achieve very short charging times. If the current is high enough and the high voltage battery can handle the heat generated with the high current, charge times for 200 miles of range can be under 15 minutes today. On older EVs, the 200 mile recharge can take up to one hour or more.


The original DCFC, called “CHAdeMO”, was used by Nissan, Kia and Mitsubishi. Mitsubishi designed it for their i-MiEV, a small EV. It was popular in the original Nissan Leaf. It has a CAN system and was way ahead of its time is 2010.


Tesla (excluding the first Tesla Roadster) uses the same connector for Level I, Level II and DC Fast Charge. It has a proprietary Tesla connector that accepts both AC and DC voltage, so there’s no need to have a different connector specifically for DCFC, as the other standards require. To do this, the two larger pins (when suppling AC power) are directed to the onboard charger when using Level I and Level II. If the Tesla charger is DC, the two large pins will be directed to the HV pack. That way the connector on the Tesla is both AC and DC. Only Tesla vehicles can use their DC fast chargers, called Superchargers, for now. Tesla may open them up to all OEMs. Tesla installs and maintains these stations.

Combined Charging System

SAE set the standard for the Combined Charging System (CCS), as the American car companies wanted a smaller opening so that existing vehicles could use the same “gas flap” and also use the communication system with J1772. This DCFC, sometimes called a “combo plug,” was introduced in M/Y 2013 and is used in every OEM today, except Tesla. In 2022 Nissan brought an EV to America with CCS. CCS is replacing CHAdeMO.

When it comes to a Fast Charger, now we have a charger, not an EVSE. It supplies DC that can go directly to the HV battery. SAE has written many new standards for EV grid charging since J1772. There is more information on the SAE website,

The North American Five-Pin Receptacle

In North America and some other parts of the world, a five-pin system is used for Level I and Level II. Look at the J1772 receptacle and study the size of the pins. There are three large ones and two smaller ones. The larger ones are the AC lines and earth ground. The two smaller pins are used for communication and making sure the EV cannot move while plugged in.

What does each pin do? The Control Pilot (CP) is used to relay data between the EVSE and the charger about how much current is needed. It is sometimes called the “Pilot” or “Communication” pin. Next up is the Proximity Pilot (PP). That circuit makes sure you are plugged in all the way and keeps the vehicle from moving. It’s also called the “Safety” or “Proximity” pin. The term Protective Earth (PE) is a 6mm round pin that supplies an earth ground for the AC power and connects to the vehicle chassis. Two more pins, L1 and L2, supply the single phase AC power. Those five connections are all you need to recharge a high voltage battery pack.

AC Level II charging can supply more power or watts than Level I. If the Level II EVSE has 42 amps available to the on-board charger, the “charger” will recharge the HV battery faster than a Level II EVSE that only can supply 24 amps, as the charger in the EV can make use of more current. The on-board chargers range from a 3.3 kW output to almost 20 kW. As the EV world has evolved, the on-board chargers have been made more powerful to supply more current to the battery and reduce charging times.

In the CCS system, the small pins and PE still function the same way. Two larger pins were added at the bottom of the inlet, and they deliver DC power. ACDC (the company I own and where I work) designed and built an EVSE Break-Out-Box so the communication and power can be measured and scoped in real time. That allows for a proper diagnosis when a charging issue presents itself. We wanted to buy one years ago, but it was not available.

U.S. passenger vehicles sales fell in 2022, but the number of EV sales went up by a 65% over the previous year. There is a trend here. Are you ready for EVs?

About the Author

Craig Van Batenburg

Craig Van Batenburg is the lead trainer and CEO of ACDC, a hybrid and plug-in technician training company based in Worcester, Mass. ACDC started hybrid training in early 2000.  ACDC owns a fleet of 18 EMVs, from the most popular models to current EVs. Recently, ACDC has expanded to 5,000 square feet and added a battery lab. Class info is available at or call 508 826 4546. Contact Craig at [email protected].