Charging Medium- and Heavy-Duty Electric Vehicles: Plugging into the Future Part II

The medium- and heavy-duty electric vehicle (EV) market is growing. However, mass electrification of medium- and heavy-duty vehicles will require charging infrastructure and standards tailored to meet their high energy needs. Leaders have an opportunity to increase electrification of these vehicles and reduce greenhouse gas emissions by closing this infrastructure gap.

Key takeaways:

• Medium- and heavy-duty EVs have different charging needs and require separate infrastructure investments from light-duty EVs.
• There is a lack of consensus on standards for the megawatt charging systems medium- and heavy-duty EVs require.
• Achieving electrification goals for medium- and heavy-duty vehicles—and reducing their greenhouse gas emissions—requires closing the infrastructure gap.

This post is part of a two-part series. The first part discussed the need to electrify medium- and heavy-duty vehicles, which would reduce greenhouse gas emissions and improve air quality. The post also provided an update on the types of medium- and heavy-duty EVs announced and released.

Charging needs

As discussed in part I, medium- and heavy-duty EVs have high energy needs because they are heavier than their light-duty counterparts, pull heavier loads, and often travel longer routes each day. This means that some of the medium-and heavy-duty EVs require big battery packs of up to 1,000 kWh.

The high energy needs and big battery packs present challenges for medium- and heavy-duty EVs. Most of our public EV charging infrastructure accommodates light-duty EVs. The most popular EV chargers are Level 2 chargers, which can fully charge an average light-duty EV in 8-10 hours. Comparatively, an electric truck with a 600-kWh battery would need 80-100 hours to fully charge using a Level 2 charger!

DC fast chargers are the fastest chargers available today. They range from 50 kW to 350 kW. The fastest DC fast chargers can fill a light-duty EV battery up to 80 percent in about 10 minutes. A 600-kWh electric truck would require six hours to charge using a 100 kW DC fast charger.

Charger types

A variety of connectors and plugs exist for medium- and heavy-duty EVs. These can be classified into three types of EV chargers:

1. Plug-in connectors (manual conductive) are like the EV chargers light-duty EVs use. They are popular because they are cheaper, simpler, and can support higher power transfer. Manual plug-in connectors are popular applications for fleets using the overnight depot charging model.
2. Conductive automated connection devices are another very popular format for commercial EV charging. The automated chargers can connect to vehicles to carry out DC fast charging and can be used for opportunity charging and overnight depot charging.

The SAE J3105 is a recommended standard for battery electric buses and heavy-duty vehicles. The chargers usually function through the EV’s overhead pantograph (an apparatus mounted on the roof of the EV to collect power through contact with an overhead line).

Some automated connection devices can function through an automated charging pin inserted into EVs without an overhead pantograph.

3. Automated wireless (inductive) chargers are an emerging technology with many exciting applications. The chargers wirelessly transfer power to EVs, making it convenient and fast to charge batteries. These chargers are expensive to set up and have a slightly lower power range (50-250 kW typical).

Charging models

Medium- and heavy-duty EVs use two primary charging models: depot charging and on-route charging. Fleets with medium- and heavy-duty EVs often opt for Level 2 chargers (up to 19kW) for overnight charging at their depots. Other fleets opt for EVs with smaller batteries and install DC fast chargers along fixed routes for “opportunity charging” as the EVs make stops. Opportunity charging is a popular model for electric transit buses.

Fleets with larger vehicles that go longer distances may require DC fast charging at their depots as well as along the routes traveled by their vehicles. While a 350 kW DC fast charger is considered fast for light-duty EVs, medium- and heavy-duty EVs require even faster charging, especially if they rely on DC fast charging for on-route charging.

Lack of public infrastructure

While some innovative fleets have deployed these chargers and charging models, medium- and heavy-duty charging infrastructure has not received the same attention as light-duty charging. The lack of charging options has remained a bottleneck for the increased adoption of these vehicles.

Government support has traditionally been focused on light-duty charging as light-duty EVs were introduced to the market first. Retailers, workplaces, and municipalities have also focused on installing light-duty chargers because these entities mostly encounter light-duty EVs.

Medium- and heavy-duty EV charging woes are compounded by the fact that most publicly available EV chargers are not physically accessible to larger vehicles. Chargers are often located in parking lots designed only to accommodate light-duty EVs. This excludes most medium- and heavy-duty buses and trucks from accessing the growing network of public chargers.

Plugging the gap

Governments, utilities, and other relevant actors have noted the growing market for medium- and heavy-duty EVs and have started taking action to fill the infrastructure gap. The bipartisan infrastructure bill, which Congress passed in November, authorizes the Congestion Mitigation and Air Quality Improvement Program funding and the Loan Program Office’s Advanced Technology Vehicle Manufacturing Program to include medium- and heavy-duty vehicles and infrastructure spending.

State and local governments are also keen on developing EV supply chains and electrifying their transportation systems. Many states now offer rebates and incentives for medium- and heavy-duty charging infrastructure. For example, the Salt River Project in Arizona offers a $1,500 rebate per port for medium- and heavy-duty charging infrastructure, while the Los Angeles Department of Water and Power offers up to $5,000 for each Level 2 charger and up to $75,000 per DC fast charger to commercial customers.

States are also forming regional coalitions with other states to accelerate development:

• The first such coalition was organized by Northeast States for Coordinated Air Use Management in 2020 when California, Connecticut, Colorado, Hawaii, Maine, Maryland, Massachusetts, New Jersey, New York, North Carolina, Oregon, Pennsylvania, Rhode Island, Vermont, and Washington announced a joint memorandum of understanding. The states committed to working collaboratively to advance and accelerate the electric medium- and heavy-duty vehicles market.
• Other states have followed suit; Illinois, Indiana, Michigan, Minnesota, and Wisconsin recently signed the Regional Electric Vehicle Midwest Coalition Memorandum of Understanding (MOU). The MOU creates a regional framework to accelerate vehicle electrification, focusing on medium- and heavy-duty fleets.

On the utility side, Portland General Electric, in partnership with Daimler Trucks North America, opened the first-of-its-kind heavy-duty electric truck charging site called “Electric Island.” The Electric Island is designed to accommodate megawatt charging and other developments in commercial EV charging.

Emerging technology

Megawatt charging is a new technology that is still in its infancy. Much like the early days of light-duty EV chargers, these chargers come in different forms and variants. There is a lack of consensus on standards. For example, liquid cooling for high-current conductors has not been validated yet. At the same time, non-cooled charging cables are impractical to use.

Furthermore, medium- and heavy-duty EVs do not have a standardized charging port location. This makes it challenging to design floorplans for charging facilities that accommodate all medium- and heavy-duty EVs.

Industry-wide standards need to be in place before we can expect scalability for medium- and heavy-duty charging infrastructure. CharIn and the National Renewable Energy Laboratory are developing a universal Megawatt Charging System for electric trucks and buses. Megawatt charging will make it possible to charge most of today’s medium- and heavy-duty EVs in under half an hour with charging capacity up to 3.75 megawatts. Such a reduction in charging time will make a viable business case for many use cases.

Looking Ahead
Policy makers, manufacturers, and fleets managers are turning their attention to electrifying medium- and heavy-duty fleets and have announced ambitious goals and targets. To realize the ambitious targets and goals, we must address the medium- and heavy-duty infrastructure gap.

Governments, utilities, and charging service providers must work in unison to provide charging solutions to medium- and heavy-duty EVs. Solutions include providing incentives to lower the cost of installing these chargers, developing universal standards for medium- and heavy-duty EV charging, and others.

Electrifying these vehicles, from urban delivery trucks to school buses and long-haul freight trucks, is key to reducing emissions from the transportation sector.

Contact M. Moaz Uddin, [email protected] with questions on electric vehicle policy.