With the increasing number of Electric Vehicles (EV) on a global scale, EV charging has become an essential aspect of car ownership. To compete with internal combustion engine (ICE) vehicles, the charging time of EVs needs to be at similar levels as refueling conventional vehicles. Historically speaking, charging stations technology dates to the same time as EVs. Charging stations in the early 1900s utilized bulky mercury-arc rectifiers, essentially glass bulbs containing liquid mercury. However, today’s technology has improved exponentially with advancements in power electronics. In the modern era, EV chargers started the technological journey as a device that could recharge a car overnight.This advancement did not come cheap as they were a result of significantinvestment in research and development . The result has made the recharging experience comparable to a refueling stop for a conventional car.
The availability of EV charging infrastructure in a region directly impacts EV adoption. A higher density of charging outlets means a reduction in the point-to-point distance between stations, minimizing range anxiety. In addition to the number of chargers, the power capacity of chargers has also increased, paving the way for fast charging station networks based on direct current (DC) technology.
A number of utilities have announced large scale installation of publicaly accessible charging stations and State Grid Corporation of China (SGCC) is one of them. In fact, China has emerged as a market leader in installed charging infrastructure as it increased its publicly accessible charging stations by almost 51% in 2017. This has brought China’s public charging outlets market share close to 48% globally. The graph below shows the global distribution of public EV charging outlets in 2017.
EV chargers are no longer ‘plug & sleep’ devices
All EVs equipped with battery storage have one thing in common: DC. As our grids are based on AC, EVs cannot be charged without an AC to DC conversion mechanism (AC-DC converter or simply called a converter). It results in two design possibilities; embedding the converter in the car (onboard charger) or coupling the converter with AC hardware outside the car (offboard charger). With an onboard charger, one can essentially use standard AC outlets to charge the vehicle. However, due to low voltage and current-carrying capability of normal AC outlets, the charging process can extend between 6 to 8 hours. The charging time of an EV is a function of battery capacity and charging power.
To reduce range anxiety, EV batteries have gone through multiple phases of capacity enhancements. Right now, a typical battery-electric vehicle (BEV) has, on average, 40 kWh capacity; with some models reaching 100 kWh. Higher battery capacity also means an increase in charging time provided the charging power (kW) is kept constant. That’s why EV chargers also went through technological evolution to increase the charging power. Slow charging methods (offboard chargers) are further divided into two types (Level 1 and Level 2), based on their capacity. Level 1 is the slowest form of charging, requiring EVs to have an onboard AC-DC converter. In the US, Level 1 chargers use a standard 120V (16A) single phase grounded outlet, and, in the case of Europe, a 240V (20A) outlet is used.
Some of the home chargers and most of the public chargers are level 2 chargers. Grid connections at voltages 230V (United States) or 400V (Europe) are required for level 2 chargers. Level 2 chargers also include a built-in AC-DC converter. The major differences are the amount of power available and, consequently, the time needed to reach full state-of-charge. Level 2 chargers have significantly higher power levels than level 1 chargers, as shown in Table 1.
Here are some of the examples of the time difference to complete one full charging cycle with level 1 and level 2 chargers for different EV models:
With an increase of input kW capacity, the weight of the onboard charger also increases due to bigger hardware components for AC to DC conversion and power quality conditioning. DC fast chargers (also known as Level 3 chargers) can solve this issue because AC to DC conversion is done outside the vehicle with the charging station looking like a gas pump-sized machine. Theoretically, all commercially available chargers are either based on slow AC charging mechanism (level 1 & 2) or DC fast charging. However, there are different standards used by car manufactures for the charging plug and communication protocol required to keep track of battery parameters. For example, Tesla has the Supercharger Network; Nissan Leaf and other models utilize CHAdeMO, and other groups use SAE Combo standard called combined charging system (CCS). The chart below summarizes the EV charger capacity and their relevant standard types adopted in different regions.
Win, Lose, or Draw?
CHAdeMO was the first to arrive on scene when Japan installed its first DC fast charging station back in 2008. Right now, there are more than 1,600 CHAdeMO fast-charging stations in the USA and roughly 3,000 in Europe.
European car manufacturers and the European Union (EU), even though it does not restrict installation of other technologies, support SAE CCS. This is evident from their plans to install charging infrastructure in major European countries. However, CHAdeMO is not expected to vanish anytime soon, especially when Nissan is backing it. Both charging standards have their pros and cons. CHAdeMO’s controller area network (CAN) communication protocol makes its integration with rest of the vehicle easy as CAN protocol is used for onboard communication for all EVs. On the other hand, CCS operates on a programmable logic controller (PLC) protocol which makes it an ideal candidate for smart grid integration.
There is a possibility that all charging standards keep on penetrating the market with multi-standard charging stations, but some recent events indicate that there might be a conclusive win. In 2016, Tesla motors joined ‘CharIn’, an association which fully backs CCS. In 2017, Honda, a mainstream Japanese car manufacturer, opted for CCS on its ‘Honda Clarity (BEV)’ which could be an indication of a turning point in this competition for standards. Additionally, South Korea officially announced to adopt CCS as the fast charging standard earlier this year. And finally, European car manufacturers BMW, VW, and Daimler created a joint-venture to install 400 charging stations by 2020 in EU countries. Even though CCS has a wide range of ‘silent supporters’, it still has not had the same level of committed support like Nissan and Tesla’s have shown for CHAdeMO and Supercharger, respectively. It will also be very interesting to see the European Union’s role in harmonization of charging standards in the coming years. The graphs below depict CCS is approaching CHAdeMO levels with the backing of top-tier automotive OEMs in EU.
Standards war can hamper EV adoption
If CCS succeeds in capturing a major portion of the market, automotive OEMs supporting CCS will have a competitive advantage over other OEMs due to extensive charging networks. Although competition in the market is considered healthy from an end-consumer perspective, in this case, competition in standards can potentially make EV users ambiguous in their choice of vehicle, which can negatively impact EV adoption rate. Range anxiety could also increase if we reach a point when a consumer reaches a fast charging station and finds out that the charging plug is incompatible with their vehicle model.
This article is a 3rd from a series of articles published as a follow-up to our report on Impact of EVs on theirsurrounding ecosystem. You can have a look at the report content here: