Your Mileage May Vary: The State of Electric Vehicle Charging
While an internal combustion engine vehicle can be refueled rapidly and universally at any gas station, the state of EV charging is stratified, and recharging times vary. EV charging typically falls into three major categories, referred to as levels 1, 2 and 3. It is important to emphasize that the information contained in this article is specific to the North American market, as standards vary region to region.
Both level 1 and level 2 charging utilize an EV’s onboard charger to convert the alternating current (AC) supplied by the electrical grid into direct current (DC) and carefully regulate the output voltage and current to an appropriate level for charging its battery. The advantage of level 1 charging is that an EV is plugged directly into a standard 120 V outlet. While this is convenient in the sense that this type of outlet is found almost anywhere there is electricity, the charging rate is low. In an hour of charging, a typical EV can expect to gain 2-5 miles of range per hour of charging.
Level 2 charging offers a far greater rate when compared to level 1. To accomplish this, an EV is connected to a 240 / 208 V circuit, commonly used to power stoves and clothes dryers. As with level 1 charging, the vehicle’s onboard charger is utilized in this process. Due to the higher voltage and current available, this type of charging typically offers 10-40 miles of range per hour of charging. It is important to realize that the level 2 charging rate achieved by a particular EV and charger combination depends on the onboard charger equipped in the vehicle, as well as the amount of current available to the charger from the grid.
Most EVs use a standardized SAE International (formerly the Society of Automotive Engineers) J1772 connector for the purpose of level 1 and level 2 charging. While Tesla has opted to build its cars exclusively with a proprietary charging connector, a physical adaptor allowing the use of standard level 2 chargers is included with each of its vehicles. Level 2 chargers can be hardwired or plugged into specialized outlets.
Finally, an EV can be charged using a DC fast charger (DCFC). This type of charging is often referred to as level 3 charging. This type of charging is typically reserved for commercial and public installations. A DCFC outputs high voltage DC to charge the vehicle’s battery pack directly, bypassing the onboard charger. This allows the battery pack to charge at a much greater rate, as the charging power is not limited by the small onboard charger. Instead, the vehicle charges as fast as is safe for the battery or at the maximum rating of the charger, whichever is lower.
The charging rate achieved by this method varies widely depending on the charger’s capabilities and the specifications of the battery pack within the EV. Rates typically range from 150-1000 miles of range per hour of charging. This means that most EVs can fully recharge at a modestly sized DCFC in well under an hour. Note that unlike levels 1 and 2 charging, unfortunately, there is not a single standard connector for DCFCs. This means that one must keep in mind the type of connector their vehicle possesses when looking for a compatible DCFC.
It is important to stress that the charging rate achieved at any charging level is highly dependent on the particular EV being charged. The number of miles of range replenished at a given charging rate also varies with the miles per gallon of gasoline-equivalent (MPGe) rating of the vehicle as well as environmental factors and the driver’s habits. In the case of the two levels of AC charging, the charging rate is primarily tied to the capacity of the onboard charger, along with the ampacity of the supply circuit. In the case of a DCFC, the limiting factor is the vehicle’s battery pack as well as the power output of the DCFC. While other aspects of electric vehicles are indubitably far more exciting, it is important for EV owners, both current and future, to have a working knowledge of the charging standards available for their vehicle.