Developing Infrastructure to Charge Plug-In Electric Vehicles
To widely accept the use of plug-in hybrid electric vehicles (PHEVs) and all-electric vehicles (EVs), consumers and fleets need a developed infrastructure of charging stations. Drivers need affordable, convenient, and compatible options for charging at home (or at fleet facilities, in the case of fleets). Charging stations at workplaces and public destinations may also bolster the market acceptance of PEVs.
Charging plug-in electric vehicles requires plugging into electric vehicle supply equipment (EVSE). Hybrid electric vehicles (HEVs) are charged using regenerative braking and the internal combustion engine and are not plugged into charging equipment.
Charging equipment for plug-in hybrid electric vehicles (PHEVs) and all-electric vehicles (EVs) is classified by the rate at which the batteries are charged. Charging times vary based on how depleted the battery is, how much energy it holds, the type of battery, and the type of EVSE. The charging time can range from 15 minutes to 20 hours or more, depending on these factors.
AC Level 1 Charging
AC Level 1 EVSE (often referred to simply as Level 1) provides charging through a 120 volt (V) AC plug and requires electrical installation per the National Electrical Code. Most, if not all, PEVs will come with an AC Level 1 EVSE cordset so that no additional charging equipment is required. On one end of the cord is a standard, three-prong household plug (NEMA 5-15 connector). On the other end is a J1772 standard connector (see the Connectors and Plugs section below), which plugs into the vehicle.
Based on the battery type and vehicle, AC Level 1 charging adds about 2 to 5 miles of range to a PEV per hour of charging time. AC Level 1 is typically used for charging when there is only a 120 V outlet available, but can easily provide all of a driver's needs. For example, 8 hours of charging at 120V can replenish 40 miles of electric range, which is over 30% further than the average daily driving distance for vehicle owners in the United States as indicated by the National Household Transportation Survey.
AC Level 2 Charging
AC Level 2 equipment (often referred to simply as Level 2) offers charging through 240 V (typical in residential applications) or 208 V (typical in commercial applications) electrical service. AC Level 2 EVSE requires installation of home charging or public charging equipment and a dedicated circuit of 20 to 100 amps, depending on the EVSE requirements. This charging option can operate at up to 80 amperes and 19.2 kW. However, most residential AC Level 2 EVSE will operate at lower power. Many such units operate at up to 30 amperes, delivering 7.2 kW of power. These units require a dedicated 40 amp circuit.
Most homes have 240 V service available, and because AC Level 2 EVSE can charge a typical EV battery overnight, they will commonly be installed for EV owners' homes. AC Level 2 equipment uses the same connector on the vehicle that Level 1 equipment uses and all commercially available PEVs have the ability to charge from AC level 1 and AC level 2 EVSE. Based on the vehicle and circuit capacity, AC Level 2 adds about 10 to 20 miles of range per hour of charging time.
Future AC Charging Options
An additional standard (SAE J3068) is under development for higher rates of AC charging using three-phase power, which is common at commercial and industrial locations in the United States. Some components of the standard will be adapted from the European three-phase charging standards and specified for North American AC grid voltages and requirements. In the U.S., the common three-phase voltages are typically 208/120 V, 480/277 V. The standard will target power levels between 6kW and 130kW.
DC Fast Charging
Direct-current (DC) fast charging equipment, sometimes called DC Level 2 (typically 208/480 V AC three-phase input), enables rapid charging along heavy traffic corridors and at public stations. EVs equipped with either a CHAdeMO or SAE DC fast charge receptacle can add 50 to 70 miles of range in about 20 minutes.
Inductive charging equipment, which uses an electromagnetic field to transfer electricity to a PEV without a cord, has been recently introduced commercially for installation as an aftermarket add-on. Currently available wireless charging stations operate at power levels comparable to AC Level 2.
Connectors and Plugs
Most modern charging equipment and vehicles have a standard connector and receptacle based on the SAE J1772 standard developed by SAE International. Any vehicle with this plug receptacle should be able to use any J1772-compliant AC Level 1 or AC Level 2 EVSE. All major vehicle and charging system manufacturers support this standard in the U.S., which should eliminate drivers' concerns about whether their vehicle is compatible with the infrastructure. Three types of DC Fast Charging exist today. CHAdeMO is the most common as it is used by the Nissan Leaf and Mitsubishi vehicles. Recently, the Chevy Spark and the BMW i3 came to market with the SAE J1772 combined charging system (CCS), which uses a single port for either AC Level 1 and 2 or DC Level 2 charging. Additionally, Tesla is rapidly expanding their supercharger network, which is based on their own connector and currently only charges Tesla vehicles. Each of these three standards operate at a variety of DC voltages, and each has a different maximum power level but replenish miles of range at roughly the same rate on average.