The charging of electric vehicles is a quickly evolving field of endeavor, and at this time, there are three main types of charging.
Level 1, or slow charging, basically involves plugging a car into an everyday house current, which – as one might expect – take many hours to fully charge an electric vehicle (EV). Level 2 charging uses a 240 V AC current at power levels that are not typically available in most homes. Lastly, Level 3 charging, also known as DC fast charge, utilizes DC at up to 500 V. Level 3 charging can deliver 100 kW of electrical power or more, and can charge an EV approximately five times as quickly.
Electric Vehicles (EV) Charing Standards
The defining standard for the charging of EVs in the U.S. is SAE J1772. As the technology advances, the standard continues to evolve, but its parameters for Level 1 and Level 2 AC charging have coalesced. For Level 1, it is 120 V at 16 amps or less for a maximum of 1.92 kW, and to 240 Volts at 80 amps or less for a maximum of 19.2 kW for Level 2. All EVs sold in the U.S. can accommodate this standard, and come equipped with a port that can receive the plug through which SAE J1772 EV chargers deliver power. The port pictured below is standard on just about all EVs sold in the U.S. and will accommodate all Level 1 or Level 2 charging systems.
Figure 1: The SAE J1712 plug from the charger and the J1712 port on the EV with its port protector open.
This port not only delivers power, but it also accommodates the complex bursts of information that constantly flow back and forth between the vehicle and the charger, ensuring that the battery neither overcharges nor charges incorrectly. The standard itself defines the nature of the “handshake” between the vehicle and the charger. Because the motorist is, in effect, working with enough electrical power to move a subway train and he or she is not a trained technician, the standard provides for multiple layers of built-in protection to ensure safety.
Wireless Electric Car Charging System
Inductive charging is a form of Level 2 charging that transfers power from the charger to the EV via an electromagnetic connection and completely eliminates the need to connect anything from the charger to the EV. The process works in a similar manner to that of an electrical transformer, in which a primary coil imparts power to a secondary coil with which it has no physical contact. The primary coil uses the electrical power source to create a magnetic field, which induces electricity in the secondary. In the case of the EV inductive charger, the primary coil is in the charger, and the secondary is in the EV, which imparts the induced electricity to the battery under charge.
This method, of course, eliminates the hassle of plug, cable and port. It does, however, require precise positioning of the EV in relation to the charger, because coil alignment is critical. Due to the modest amount of power that can be transferred using this method in a given amount of time, consumers can expect to see inductive chargers for the home market only for the time being.
Level 2 EV Chargers
But, even eliminating inductive charging from consideration (for now), when one considers that 50 kW/h is not an uncommon capacity for a fully charged EV battery, it is no wonder that Level 2 chargers are not a considered a satisfactory solution. The most energy that a Level 2 charger can impart is under 20 kW, requiring 2½ hours of charging time. Do the math and that does not add up to an attractive prospect for a busy traveler. Level 3 chargers are the next frontier, and while standards are more or less stable for Level 1 and Level 2 chargers, Level 3 standards are still quite contentious.
Level 3 EV Chargers
At this time, there are three competing standards for Level 3 chargers. SAE J1772 has now been appended to include a standard for Level 3 charging, the SAE J1772 Combined Combo System DC Fast Charge (CCS DC Fast Charge). Most U.S. and European EV manufacturers have agreed to adopt it. There is also the CHAdeMO standard, which is championed by Japanese EV producers. Worldwide, CHAdeMO is the most widely adopted standard. It’s worth noting that most of the Level 3 charging stations now cropping up in the U.S. have the capability to accommodate vehicles adhering to either the CCS or the CHAdeMO standard. The third standard, only used by Tesla, is the Tesla Supercharger, although owners of the Tesla Model S can purchase an add-on that will enable it to use the CHAdeMO standard as well.
As it stands, standards specify a maximum power for CHAdeMO chargers of up to 62.5 kW. The CCS is of similar capacity, and it is expected to be upgraded to approximately 90 kW, but the limits here are murky at best, and at this point, it seems to be more up to the manufacturers than to the regulators. The Tesla Supercharger standard is written for 120 kW. However, as in any game of evolving, competing standards, it can be expected that there is a lot of “specsmanship” involved in these ratings, and in any event, it should be assumed that all three are subject to change.
How Do Public EV Charging Stations Work?
Beyond charging time and kW/h of run-time, EV motorists may want to consider another important factor in finding the right charging station for their vehicle – geography. Remarkably, a driver’s physical location in the U.S. can determine which types of charging stations are most accessible. CCS and CHAdeMO facilities are most common on the East and West coasts. Tesla stations, though fewer in total, are more widely dispersed on the interstates nationwide, and not concentrated on either coast. The Tesla EVs have larger batteries than most other EVs, so the vehicles are better suited for the longer trips that Tesla Supercharger stations can facilitate.
Figure 3: A CCS Plug and Port.
Interestingly, the Chevy Volt doesn’t include a capability for Level 3 charging. This is perhaps because the vehicle includes a built-in gas engine that’s only purpose is to charge the battery when needed. Most Volt owners prefer to charge the vehicle’s smaller, 18.4 kW/h battery at home, although Level 2 charging is fully supported.
The ChargePoint Company is a leading supplier of Level 3 chargers and maintains a large network of public charging stations nationwide. The company’s commercially available CPE200 50 kW Level 3 Charger comes equipped to service EVs with both CCS and CHAdeMO receptacles. It’s probably a safe bet that neither standard is poised to dominate the other. In fact, they are similar enough that many contend it is reasonable to hope they are capable of converging. Who can then doubt that the battle will begin again when the industry is ready for a Level 4?