An Electric Vehicle Charging Station (EVCS), also called Electric Vehicle Supply Equipment (EVSE); and/or a charging station or simply charger is a piece of equipment that supplies electrical power for charging plug-in electric vehicles (including hybrids, neighborhood electric vehicles, trucks, buses, and others).
Although batteries can only be charged with DC power, most electric vehicles have an onboard AC-to-DC converter that allows them to be plugged into a standard household AC electrical receptacle. Inexpensive low-power public charging stations will also provide AC power, known as “AC charging stations”. To facilitate higher power charging, which requires much larger AC-to-DC converters, the converter is built into the charging station instead of the vehicle, and the station supplies already-converted DC power directly to the vehicle, bypassing the vehicle’s onboard converter. These are known as “DC charging stations”. Most fully electric car models can accept both AC and DC power.
Charging stations provide connectors that conform to a variety of standards. DC charging stations are commonly equipped with multiple connectors to be able to supply a wide variety of vehicles. Public charging stations are typically found street-side or at retail shopping centers, government facilities, and other parking areas.
Charging station with NEMA connector for electric AMC Gremlin used by Seattle City Light in 1973. Multiple standards have been established for charging technology to enable interoperability across vendors. Standards are available for nomenclature, power, and connectors. Notably, Tesla has developed proprietary technology in these areas.
Under NEC-1999, Level 1 charging equipment was connected to the grid through a standard NEMA 5-20R 3-prong electrical outlet with grounding, and a ground-fault circuit interrupter was required within 12 in (300 mm) of the plug. The supply circuit required protection at 125% of the maximum rated current; for example, charging equipment rated at 16 A continuous current required a breaker sized to 20 A.
Level 2 charging equipment was permanently wired and fastened at a fixed location under NEC-1999. It also required grounding and ground-fault protection; in addition, it required an interlock to prevent vehicle startup during charging and a safety breakaway for the cable and connector. A 40 A breaker (125% of continuous maximum supply current) was required to protect the branch circuit. For convenience and speedier charging, many early EVs preferred that owners and operators install Level 2 charging equipment, which was connected to the EV either through an inductive paddle (Magne Charge) or a conductive connector (AVCON).
Level 3 charging equipment used an off-vehicle rectifier to convert the input AC power to DC, which was then supplied to the vehicle. A 500 A breaker (125% of continuous maximum supply current) was required to protect the branch circuit. At the time it was written, NEC-1999 anticipated that Level 3 charging equipment would require utilities to upgrade their distribution systems and transformers.
The Society of Automotive Engineers (SAE International) defines the general physical, electrical, communication, and performance requirements for EV charging systems used in North America, as part of standard SAE J1772. SAE J1772 defines four levels of charging, two levels each for AC and DC supplies; the differences between levels are based upon the power distribution type, standards and maximum power.
Alternating current (AC): AC charging stations connect the vehicle’s onboard charging circuitry directly to the AC supply.
AC Level 1: Connects directly to a standard 120 V North American residential outlet; capable of supplying 6–16 A (0.7–1.92 kW) depending on the capacity of a dedicated circuit.
AC Level 2: Utilizes 240 V residential or 208 V commercial power to supply between 6 and 80 A (1.4–19.2 kW). It provides a significant charging speed increase over Level 1 AC charging.
Direct current (DC): Commonly, though incorrectly, called “Level 3” charging based on the older NEC-1999 definition, DC charging is categorized separately in the SAE standard. In DC fast-charging, grid power is passed through an AC-to-DC rectifier before reaching the vehicle’s battery, bypassing any onboard rectifier (80 kW at 50–1000 V … 400 kW at 50–1000 V)
Additional standards released by SAE for charging include SAE J3068 (three-phase AC charging, using the Type 2 connector defined in IEC 62196-2) and SAE J3105 (automated connection of DC charging devices).
Tesla: In North America, Tesla vehicles use a proprietary charging port; to meet EU requirements on recharging points, Tesla vehicles sold there are equipped with an CCS Combo 2 port. Either port will take 480 V DC fast charging through its network of Tesla Superchargers. Depending on the Supercharger version, power is supplied at 72, 150, or 250 kW, corresponding to DC Levels 1 and 2 of SAE J1772. For a Tesla Model S, a supercharger can add around 275 km (170 miles) of range in about 30 minutes. As of Q4 2021, Tesla reported 3,476 supercharging stations.
Future development: An extension to the CCS DC fast-charging standard for electric cars and light trucks is under development, which will provide higher power charging for large commercial vehicles (Class 8, and possibly 6 and 7 as well, including school and transit buses). When the CharIN task force was formed in March 2018, the new standard being developed was originally called High Power Charging for Commercial Vehicles (HPCCV), later renamed Megawatt Charging System (MCS). MCS is expected to operate in the range of 200–1500 V and 0–3000 A for a theoretical maximum power of 4.5 MW. The proposal calls for MCS charge ports to be compatible with existing CCS and HPC chargers. The task force released aggregated requirements in February 2019, which called for maximum limits of 1000 V DC (optionally, 1500 V DC) and 3000 A continuous rating.