As the roster of light-duty and commercial-purpose battery electric vehicles (EVs) begins an almost catalytic expansion in 2022, better, faster, and smarter battery recharging is on the way to accompany the takeoff. Charging advances — chiefly related to recharging times and charger access — have long been touted as vital to consumer and commercial acceptance of EVs. Now the government and automotive and electronics industries are hastening initiatives and technology to support the EV “experience.”

In mid-December 2021, U.S. Vice President Kamala Harris unveiled the Biden Administration’s EV Charging Action Plan as explanation for how the federal government intends to execute the $7.5 billion broadly directed to building out the nation’s recharging network. The plan is part of the long-negotiated $1.2 trillion ($550 billion in new spending) infrastructure bill officially known as the Infrastructure Investment and Jobs Act.

The EV Charging Action Plan offered the government’s general strategy, saying: “The Department of Energy (DOE) and Department of Transportation (DOT) will establish a Joint Office of Energy and Transportation focused on deploying EV infrastructure.” The plan noted that, “the initial focus will be building a convenient, reliable public charging network that can build public confidence, with a focus on filling gaps in rural, disadvantaged, and hard-to-reach locations.”

More specifically, the new infrastructure bill aims to establish a nationwide network of a half-million public EV chargers. The bill’s $7.5 billion recharging-network investment includes $5 billion for “formula funding” for individual states to take part in building the national charging network. The remaining $2.5 billion will be directed to “communities and corridors through a competitive grant program that will support innovative approaches and ensure that charger deployment meets Administration priorities such as supporting rural charging, improving local air quality, and increasing EV charging access in disadvantaged communities.”

Speaking specifically to the bill’s charging-infrastructure emphasis, the Alliance for Automotive Innovation (AAI) called for all federally funded DC fast chargers at transit hubs and on charging “corridors” to be capable of charging at up to 350 kW. AAI stated in a release, “As more and more electric vehicles come to market with larger batteries, charging speed is going to become increasingly important. EV charging at 350 kW is needed for corridor charging not only to reduce the recharge time of each EV, but also to increase the throughput of EVs to allow more EVs to charge from the same connector.” The AAI also said it is less costly to install 350-kW capacity now than to retrofit later.

A gallium nitride (GaN)-based traction inverter — items Q1 through Q8 are GaN power transistors — promises greatly reduced power losses that will help speed recharging and improve EV driving range. (Photo: GaN Systems)

Batteries as Part of the Equation

The Biden Administration also acknowledged that advances in batteries can translate into faster and better recharging. It is encouraging efforts to improve the U.S. domestic supply chain for EV battery materials and production. One example is a comprehensive plan to support battery manufacturing through initiatives such as the DOE’s Loan Programs Office and its Advanced Technology Vehicles Manufacturing Loan Program to “support the domestic battery supply chain.” Other monies in the new bill — separate from the EV-charging infrastructure investment — include $3 billion directed to competitive grants for battery minerals and refined materials and $3 billion to build, retool or expand battery manufacturing, and establish recycling facilities.

Meanwhile, automakers and battery developers and suppliers are engaged in ongoing improvement of existing batteries, chemistry and power electronics to squeeze more performance from current or soon-to-come battery formats. Increased battery capacity or system efficiency for example, can improve driving range, lessening the need for recharging. And smarter power electronics can help batteries to recharge more quickly.

Volvo’s Polestar, for one, recently enhanced its propulsion system, via an over-the-air software update that required no service visit, to incorporate a new battery “preconditioning” function tied to the navigation system. When the driver selects a public DC charger as a destination, the battery pack’s temperature and other operational parameters are tailored to have the battery in optimum condition for the quickest recharge when the charger location is reached.

Another fast-advancing method to quicker recharging is to increase vehicle electrical-system capacity — higher voltages can enable smaller, lighter components that always are an EV development priority, as well as the ability to accept more power, more quickly, from a charger. Porsche led the way with an 800-volt architecture for its Taycan EV, doubling the system voltage of typical EVs.

Diagram of Hyundai vehicle-to-load (V2L) bi-directional “smart” charging system. (Photo: Hyundai)

But higher voltages, many industry sources claim, are inevitable at every EV price point. The Hyundai Group’s new E-GMP platform for EVs was engineered as an 800-V system, but in concession to the likelihood that a significant 800-V charging infrastructure will take time to install, the E-GMP charging system can operate at 400 volts without any adapters or extra components, internally stepping up 400-V input to 800 V. For its newly launched Ioniq 5 EV, the company claims 800-V charging can enable a recharge from 10 percent battery capacity to 80 percent in 18 minutes.

Bi-Directional Charging, Innovative Inverters

For residence-based charging, it’s expected that bi-directional capability will emerge as a must-have feature that adds considerable potential value to the EV purchase equation. Ford has been an early promoter, featuring in promotions for its upcoming F-150 Lightning pickup bi-directional charging’s ability to use an EV’s battery to operate high-energy power tools or even an entire home for as much as three days.

Hyundai’s Ioniq 5 has somewhat more limited bi-directional power capability (at 77 kWh its battery is smaller than that expected for the F-150 Lightning), but can be used to power small appliances and other equipment or charge another EV. This vehicle-to-load (V2L) functionality also has been demonstrated by other automakers and is projected to be promoted as an EV advantage over internalcombustion power.

Residences and other structures must be appropriately wired for the kind of whole-home bi-directional power Ford promotes. But the feature quickly will be “table stakes” for EV batteries, said Matt Londre, President of Willow Glen Electric and Regional Leader of Northern California for Qmerit, which manages a national network of certified electricians to help ensure EV buyers receive safe, reliable, and permitted home-charging installations.

Higher-capacity charging, bi-directional functionality and other charging-related advances are enabled, in some instances, by the quickly evolving technology in one of an EV system’s most crucial power-electronics components, the inverter. BorgWarner, for example, has a 400-V inverter employing silicon-carbide (SiC) as its primary semiconductor material.

Earmarked for a 2023 production EV, the company said in a release, “The system features greater durability through its wire-bondless power switch design, in which the silicon-isolated gate bipolar transistor power switches have been replaced by SiC metal-oxide-semiconductor field-effect transistor power switches. This delivers up to a 70 percent reduction in switching losses, offering OEMs improved performance and reduced costs for their electrified propulsion systems.”

Gallium-nitride (GaN) semiconductors also are speculated to impart new performance advantages for EV inverters and other power electronics. GaN semiconductors have 1,000 times more electron mobility than silicon, said Paul Weiner, vice president of strategic marketing for GaN Systems, in an article written for SAE International in 2021. In comparison testing conducted in 2020, he said the efficiency of a GaN-based traction inverter is improved significantly by reducing power losses by 50 percent, resulting in battery energy saving and extended driving range, not to mention potentially significant system-cost reduction.

This article was written by Bill Visnic, Editorial Director, Mobility Media, SAE International. For more information visit here .