The U.S. government is attempting to encourage the construction of so-called rapid chargers, which can charge electric vehicles in 15 to 40 minutes. This is still slower than a traditional fill-up at a petrol station, but it is faster than the hours-long process at public chargers that deliver electricity at 7 to 19 kilowatts.
Trucking companies and charger manufacturers have installed and tested megawatt-powered charging systems. Some prototypes exceed 3 megawatts in power output. National Renewable Energy Laboratory and other national laboratories are developing megawatt-level designs to charge trucks in under thirty minutes.
Additionally, automakers are exploring methods to improve the batteries themselves in order to accelerate charging times.
However, there is considerable debate over how rapid charging will need to be and where chargers should be placed. The outcome of this debate could affect the future of transport in the coming years.
Some in the EV industry believe that super-fast charging will be necessary for widespread consumer adoption of the vehicles. According to them, making rapid charging readily accessible is essential to alleviating “range anxiety” — the fear that drivers will become stranded on the side of the road without power.
“It’s human nature to want things to be better, faster, and cheaper,” says Dan Bowermaster, director of electric-vehicle research at the Electric Power Research Institute, a non-profit organisation that provides guidance to the power industry.
Others contend that this viewpoint is a remnant to the fueling practises of the era of internal combustion engines. It may be necessary to install faster chargers on intercity highways so that people can travel extended distances. However, some industry experts believe that, in addition to creating a backbone of highway chargers, it would be more effective to install massive numbers of slower chargers at locations where people park—offices, restaurants, shops, and apartments—to make charging a car a convenient and ubiquitous experience.
The majority of charge occurs at home, and this trend is likely to continue. Earlier adopters of EVs have typically been high-income homeowners of single-family homes with a garage or driveway where vehicles can slowly sip electricity for hours. However, residents of multifamily dwellings have less access to charging.
In order to expedite the transition to electric vehicles, the U.S. government approved spending $7.5 billion over several years to increase the number of available outlets. Approximately 7,300 locations in the United States currently have rapid chargers, with the majority of the equipment being first-generation.
Existing rapid chargers range in power output from 50 to 350 kilowatts. Depending on the charging rate of the EV battery, they are able to charge a battery to 80% in 15 minutes at the highest power level or around an hour at the lower end. Currently, only a smattering of high-end passenger EVs are capable of using a 350-kilowatt charger.
The more prevalent type of public charger, known as a level 2, has a power output between 7 and 19 kilowatts and utilises the same type of outlet as an electric clothes dryer. It is commonly available in apartments and offices and can charge a battery to 80% in four to ten hours.
A standard wall outlet adds a few miles of charge per hour and could take 40 hours or more to fully charge a vehicle. However, it typically adds enough range overnight for EV commuters to rely on it. The majority, however, install a level 2 charger in their garage.
Tested megawatt chargers for the trucking industry are considered the domain of 18-wheelers and other heavy commercial vehicles with enormous batteries.
There are considerations between price and utility. Rapid chargers necessitate an expensive utility infrastructure and charging apparatus; ultra-rapid charging would be even more costly.
“Higher power costs more,” declares Bowermaster. “At some point, for these higher power levels, larger and larger wires are required. At some point, the wire becomes so large that it is not only weighty, but also difficult to bend around the charging port.”
This could cause accessibility issues for disabled and elderly motorists. According to Jonathan Levy, chief commercial officer of EVgo, a fast-charging service provider, this issue may be solvable with mechanical aids to reduce the weight of cables and connectors or robotic limbs to automate the process. Additionally, robots could power autonomous vehicles.
Solid-state batteries, in which the electrolyte that conducts the electric current is a solid rather than a liquid as is the case with the majority of batteries in use today, could be used to speed up charging. Solid-state batteries could be a game-changer for achieving greater energy density and quicker charging speeds.
“You can travel further on a full charge, and the battery charges more quickly,” says Levy. It has been speculated that it will be three to five years before this occurs.
Nick Nigro, proprietor of the research firm Atlas Public Policy, anticipates that the market for passenger vehicles will adopt a standard of 350-kilowatt charging. “It’s not clear that going much higher than that for regular passenger vehicles will have much value,” he says.
Even if 350-kilowatt charging is available, it is not consistent. Extreme outdoor temperatures and the condition of a vehicle’s battery affect recharge. Once a battery’s charge reaches about 80%, the rate slows substantially; this is known as the charging curve.
“If you plug an empty battery into a 350-kilowatt charger, it will charge that quickly.” According to Jenny Baker, a senior lecturer in mechanical engineering at Swansea University in Wales who studies solid-state batteries and environmental impacts, “as the battery becomes more full, it becomes somewhat more difficult to push [the energy] in.”
“Eventually, you might as well just be trickle-charging,” she said, referring to being inserted into a standard wall outlet.
Each battery has a unique charging curve that determines how long it can sustain increased charge rates. Ken Tennyson, senior director of quality and conformance at EV fast-charging provider Electrify America, explains that automakers are attempting to lengthen the charge curve so that electric vehicles can utilise more of the kilowatt power delivery for a longer duration. By doing so, it is possible to reduce the duration of the charge session.
Other modifications would optimise the battery’s power delivery. Tennyson states that most EVs use a 400-volt system, but some manufacturers are transitioning to 800 volts, thereby doubling the power that the same current would provide. To provide drivers with the fastest possible charge, however, not only an 800 volt EV but also the most advanced charging apparatus would be required.
