The Bi-Directional Bonus for EVs

Bi-directional charging is a value-added feature that seems certain to help accelerate EV adoption.

Ford’s 2022 F-150 Lightning can be equipped to power a home’s typical energy needs for up to three days. (Ford)

Although other automakers have talked about the potential for electric vehicles (EVs) to use their increasingly powerful batteries for purposes beyond propelling the vehicle, it was Ford that brought the capability known as bi-directional charging to prominence when it revealed details of its F-150 Lightning last May. A subsequent high-visibility marketing campaign dramatically showed the Lightning using its bi-directional charging capability to power a sizeable home during a power outage.

With its seminal Leaf EV, Nissan was an early advocate of bi-directional charging for a variety of V2G functions. (Nissan)

Now, just months before the Lightning hits dealer showrooms, the outsized response to the Lightning – Ford has twice doubled the truck’s projected annual production volume to a current 150,000 units – and the gee-whiz nature of its Intelligent Backup Power capability may accelerate the industry’s march toward bi-directional charging as a standard feature for most EVs. Although there is specific hardware and software required on both sides of the charging cable to derive the benefits of the so-called vehicle-to-grid (V2G) capability, , none of it requires a deal-breaking investment for either OEMs or consumers. And fast-moving innovations in onboard power electronics – particularly the vital AC/DC inverters that are at the heart of bi-directional capability – promise to reduce costs and broaden possibilities.

“I think every electric vehicle, eventually, will be bi-directional capable – it's really only a matter of time,” maintained Matt Londre, president of Willow Glen Electric and regional leader of Northern California for Qmerit, which manages a national network of certified electricians that help ensure EV buyers receive safe, reliable home-charging installations. Qmerit currently collaborates with Ford, GM, Audi, BMW, Lucid, Rivian, Volvo and Mercedes-Benz as a preferred installer of home chargers.

“Once the F-150 Lightning comes out with it, kind of bringing the bi-directional capabilities even more mainstream,” Londre added, “it's going be a very large and popular thing. Almost ‘table stakes.’”

Unlocking EV value

Semiconductor advances such as those in the BorgWarner silicon-carbide inverter promise to speed advanced features such as bi-directional charging. (BorgWarner)

The potential to use an EV’s onboard battery energy presents opportunities to help maximize the vehicle purchase, said Ryan O’Gorman, Ford electric vehicle manager, Strategic Partnerships, in an interview with SAE Media. “I think this is probably the most game-changing product for our customer in the way of mobility – because it goes beyond mobility. It's just going to be really cool to see how customers use it; it'll be really exciting to see it market.”

Ford set an alluring benchmark for the Intelligent Backup Power system: power the entire electrical needs of the “typical” home for three days. Estimates vary regarding a typical home’s daily usage, but Ford press material mentioned an “average of 30 kWh per day (this estimate likely is conservative, particularly in unusually hot or cold weather). “You'll hear about the extreme power outages people will bring up where they've been out for a week or two weeks or something like that. But for the majority of power outages, three full days is going to cover it,” O’Gorman said.

Ford will be the first mainstream automaker to offer bi-directional charging to consumers when the F-150 Lightning will start arriving in showrooms in mid-2022. The company is confident enough that Intelligent Backup Power is such a compelling “bonus” feature of ownership that it’s structured an intriguing go-to-market strategy: Every customer who opts for a Lightning with the extended-range battery (estimated max driving range of 300 miles/483 km) will receive the 80-amp Charge Station Pro, the Level 2 home charger required for Intelligent Backup Power, included in the purchase. The Lightning’s lower-level chargers input into the 400V vehicle system at 48 amps or 32 amps.

O’Gorman explained that onboard Intelligent Backup Power capability is enabled through the inverter and associated power electronics, which channels the battery pack’s DC power through the charge cord, “then it's provided to an inverter that's external to the Charge Station Pro installed in the house. That inverter then takes the DC power that's come from the battery, converts it to AC and plumbs that into your main panel, effectively,” he said. On the home side, the wiring would include a transfer switch and a critical-loads panel that O’Gorman said might be standard with a backup installation. Typically, the inverter allows 9.6 kW of flow into the residence, he said.

Lightning pickup buyers who choose the standard-range battery (230 miles/370 km max driving range) also can install the Charge Station Pro and get Intelligent Backup Power, O’Gorman added. The only substantive difference, he said, is that pickups with the standard-range battery don’t have the dual onboard chargers (19.2-kW total) fitted to extended-range models, meaning the maximum recharging rate is 9.6 kW.

Because electrician labor and other costs vary widely, O’Gorman said he’d prefer not to speculate on installation costs. Ford has selected established nationwide solar/electrical installer Sunrun as its installation partner for Intelligent Backup Power, although the customer is free to choose another installer, he added. “We're not force-feeding the customers anything, we're leaving it to them to take the best path. But we are providing really good resources to make it easy. So, it should be relatively painless,” he said.

A typical V2G power-flow arrangement. (Nissan)
Advanced inverter is the heart of eLeapPower’s Smart Inverter System. (eLeapPower)
Matt Londre, president of Willow Glen Electric and regional leader of Northern California for Qmerit. (QMerit)

The Charge Station Pro, like nearly all other home chargers, uses the SAE standard J1772 combined charging system (CCS) connector, which was presciently designed to enable bi-directional power flow for both AC and DC current. Londre from Qmerit, which is the preferred installer for the bi-directional Connected Home Charging Station offered by Lucid Motors for its ultra-premium Air sedan, said that in addition to nearly all home chargers incorporating bi-directional capability, the industry could evolve like the mobile phone sector, with just a few manufacturers taking the lead.

“If there's a company making a fantastic charger, let's standardize on that one. And let other companies also try to find some amazing ways to differentiate their chargers,” he asserted. “Right now, if you can offer bi-directional charger in your charger, like the Lucid Connected will offer, that is one of the best product differentiators I've ever heard of in my career.” And powering the home is just one trick in bi-directional charging’s repertoire.

Londre forsees “many options in the future with powering the house, with powering your neighborhood, with powering the grid for everybody around. “In the future, I anticipate there being a time when, rather than paying 50 bucks at a garage, at airport long-term parking, they'll be paying you 50 bucks a day for access to your battery for the week when you're gone.”

Others quickly joining

That was the vision at Nissan, being one of the earliest players in the contemporary EV market with its groundbreaking Leaf, introduced in 2010. As early as 2015, Nissan was engaged with demonstrations of vehicle-to-grid bi-directional charging as a load- and cost-balancing solution. In 2018, the company initiated a pilot program in which the Leaf was grid-connected to help manage power at its headquarters in Franklin, Tenn. and its design center in San Diego. A similar pilot program, on a fleet scale, was in installed in Europe.

And in January, 2022, Volkswagen announced that all models in its new ID model range with 77 kWh battery packs will be built with bi-directional charging capability – and over-the-air (OTA) software updating will enable the function for “vehicles already delivered, as well.” The company said a specific home charger will be required and it was unclear whether or when the bi-directional charging capability would be available in the North American market. The CEO of Rivian, another premium EV maker, also has said Rivan vehicles will at some point offer bi-directional charging. It seems inevitable that more are soon follow to that point at which Qmerit’s Londre believes the feature effectively will be standard.

The onboard essentials

Although there are certain equipment requirements on the home side of the charging cable, the necessary hardware to make an EV bi-directional-capable is limited largely to equipment that already is required, specifically the inverter. As demonstrated by Volkswagen’s intent to enable the function strictly through a software update, it appears that in many situations, little about an inverter’s silicon platform need be altered to impart bi-directional charging functionality.

Moreover, inverters and other EV power electronics are rapidly evolving. Electronic-components suppliers such as BorgWarner, Bosch, Continental and ZF are turning to innovations such as silicon-carbide (SiC) and gallium-nitride (GaN) power and field-effect transistors (FETs) and semiconductors promise substantial near-term performance and efficiency upgrades – and perhaps cost reductions on a systems basis.

One startup, eLeapPower, which spoke with SAE Media about bi-directional charging, said its pending Smart Inverter System is “a really powerful, very differently configured inverter,” according to CEO Russell Pullan. With investor funding that includes a multimillion-dollar, multiyear award from the Bill Gates’ Breakthrough Energy, as well as funding from Natural Resources Canada. The Smart Inverter System uses the capabilities of the EV’s traction motor and other hardware to, among other things, eliminate the need for an onboard charger, which Pullan calls a serious EV system energy “bottleneck.”

Pullan also said his is the only system the company is aware of that can take DC power directly into the inverter. “Fleets who have their own solar power on site can now make their fleets completely green.” He said the technology currently is going into trials in Canada and is slated for production with a Chinese commercial-vehicle partner in 2023. He said the technology is open to potential advances from SiC and GaN semiconductors, depending on a customer’s cost requirements.

And at CES 2022, ZF announced a new scalable and modular e-motor inverter architecture that can be used in powertrain systems ranging from 400V to 800V. Critically, the inverter features architecture that isn’t dependent on predefined semiconductors, the company said. The next-generation inverter, called the Modular eDrive Kit, "[optimizes] the link between the power semiconductor boundary conditions and control software in order to gain the full potential from the semiconductor configuration," ZF said, particularly when employing SiC chips.