Tech Question of the Week: What information is available on electric vehicle (EV) battery degradation due to different charging speeds?

Response From: National Renewable Energy Laboratory (NREL)

Question: What information is available on electric vehicle (EV) battery degradation due to different charging speeds?

First, for general information on the expected life cycle of an EV battery, please refer to the Department of Energy’s At A Glance: Electric-Drive Vehicles fact sheet (https://afdc.energy.gov/files/u/publication/electric-drive_vehicles.pdf). Specifically, see the maintenance section for information on battery life:

“Electrical systems (battery, motor, and associated electronics) require minimal scheduled maintenance. A manufacturer’s warranty of a battery typically covers 8 years/100,000 miles. Expected battery lifetime is 12–15 years under normal operating conditions.

Next, it is our understanding that while EV batteries may degrade faster with the use of direct current (DC) fast charging compared to the use of Level 2 charging, the difference is minimal.

 This study compared four new 2012 Nissan Leaf EVs, two of which were charged exclusively by Level 2 chargers and two of which were charged exclusively by DC fast chargers. The conclusion of the report states the following:

A greater loss in battery capacity was observed for the fast-charged vehicles, though the difference compared to the level two charged vehicles was small in comparison to the overall capacity loss. The vehicle operation was, as intended, verified to be very similar between test groups, and the largest difference in conditions noted was battery temperature during charging. Hotter ambient temperatures appear to have accelerated capacity loss for all of the vehicles in the study, though the exact relationship remains to be seen.”

 

Further, a 2020 Geotab study of 6,300 EVs showed similar results to the above INL report (https://www.geotab.com/press-release/ev-battery-degradation-tool/):

“The use of DC fast chargers appears to speed up the process of degradation but there is not much difference in battery health based on frequent use of Level 1 versus Level 2 charging.”

Lastly, in 2023, Recurrent studied the battery management systems of 12,500 Tesla vehicles in the US and found that there was no significant difference in range degradation or battery damage when relying on fast charging versus level 2 or 1 charging. You may refer to the Recurrent article Full Speed Ahead: EV Study Reveals Impacts of Fast Charging (https://www.recurrentauto.com/research/impacts-of-fast-charging) more information on their results.

Battery Degradation Tools

NREL’s Battery Lifetime Analysis and Simulation Tool (BLAST) Suite (https://www.nrel.gov/transportation/blast.html) combines NREL’s battery degradation modeling with electrical and thermal performance models in order to assess battery lifespan and performance for behind-the-meter, vehicle, and stationary applications. BLAST tools incorporate realistic lab-based drive-cycles or simulated real-world driving patterns to anticipate EV battery lifetimes. In particular, BLAST-Lite (https://github.com/NREL/BLAST-Lite), which is available online, provides a library of battery lifetime and degradation models for various commercial lithium-ion batteries from recent years.

Further, Geotab offers a tool from 2020 comparing battery degradation of different EV models (https://www.geotab.com/blog/ev-battery-health/). Please note that we cannot verify the accuracy of nongovernmental resources. You may filter by model, model year, or add multiple models to compare the vehicles’ estimated battery degradation. This tool was developed from the study of 6,300 fleet and consumer EVs referenced above.

St George News: Addition of 2 zero-emission shuttle vans helps advance park, EVZion goal of ‘smart mobility solutions’

St George News Article

ST. GEORGE — Visitors to Zion National Park are riding in style after two Lightning ZEV3 Class 3 passenger vans were added to the shuttle fleet Tuesday.

The deployment of these zero-emission vehicles will augment the goals of the Utah Clean Cities East Zion pilot shuttle program.

“The public-private initiative is a landmark demonstration of how industry, federal and local agencies can come together to demonstrate smart mobility solutions that increase regional resiliency and connectivity,” said a news release from businesswire.com.

As part of a pilot program that began in 2019, EVZion has “developed a zero-emission, electric vehicle shuttle system to demonstrate the efficiency of electric vehicle transportation in rural gateway communities,” the news release said.

This high-tech, electric shuttle pilot and demonstration project involves national laboratory data collection, industry partner road testing in extreme climate fluctuations and local community leadership, according to the EVZion website.

“The opportunity to work with the Utah Clean Cities team and our partners to demonstrate the viability and scalability of all-electric, zero-emission passenger systems aligns perfectly with our mission and vision,” Nick Bettis, vice president of marketing and sales operations at Lightning eMotors, said in the news release. “As the only electrified vehicle provider actively delivering customized, fully electric Class 3 shuttles and a robust range of charging solutions, Lightning eMotors is excited to be part of the EVZion project.”

The vans were customized with rear-facing cameras to allow the side mirrors to be folded so that the vans can pass each other in the Mt. Carmel Tunnel. In conjunction with the deployment of the two vans, Lightning is demonstrating Lightning Mobile, which provides DC fast charging in a trailer format. This technology is especially valuable for charging EVs in locations that may be remote from the grid.

“The historic Mt. Carmel Tunnel, an iconic landmark since its inauguration on July 4, 1930, has long struggled with accommodating oversized vehicles and maintaining a safe traffic flow,” said Tammie Bostick, Utah Clean Cities executive director and project lead of the EVZion project. “By adopting these shuttles, tailored to the tunnel’s dimensions, we’re taking an active step towards ensuring a two-way traffic flow that eliminates the frustrating hours and miles of backed-up vehicles.

“This approach not only respects the park’s history but also paves the way for a more enjoyable and secure experience for all visitors.”

Lightning’s ZEV3 passenger vans have a long track record of operating in public and private transit and on-demand microtransit contexts across the county, the news release said.

The EVZion ribbon-cutting follows a recent announcement by Teton Village, Wyoming, about the acquisition of Lightning eMotors vehicles to replace the diesel buses that serve nearly half a million people in and around Teton Village resort.

Following are Zion National Park shuttle service reminders from the park service:

  • You do not need a ticket or reservation to ride the park shuttle or enter the park.
  • During the shuttle season, visitors cannot drive personal vehicles on Zion Canyon Scenic Drive.
  • Later in 2023, the park will share information about shuttle operations in December.
  • Shuttles arrive about every 15 minutes on the Springdale Line (outside the park) and about every 5-10 minutes on the Zion Canyon Line (inside the park).

Tech Question of the Week: What are the main variables impacting the total cost of ownership (TCO) analysis for electric and compressed natural gas (CNG) school and transit buses?

First, it’s important to note that a TCO analysis will depend on several factors, which can vary based on region or site. In addition to the upfront vehicle purchase cost, a major factor impacting school and transit bus TCO is the upfront cost of procuring and installing infrastructure, and the cost of daily fueling. Please see below for a high-level overview of the cost inputs to consider, a broad discussion of some major cost factors, and resources for additional cost data.

TCO Inputs

Argonne National Laboratory’s (ANL) Alternative Fuel Life-Cycle Environmental and Economic Transportation (AFLEET) Tool (https://afleet-web.es.anl.gov/) is our go-to tool for analyzing the TCO of alternative fuel vehicles, including school and transit buses. Please note, there have been recent updates to AFLEET this year.

It may be helpful to review and adjust the default values in the Inputs tab of the AFLEET spreadsheet tool for an idea of the various factors that impact a TCO analysis. In no particular order, a high-level overview of key inputs used in AFLEET’s TCO analysis are listed below:

  • Location
  • Vehicle Purchase Price
  • Number of Vehicles Purchased
  • Years of Planned Ownership
  • Annual Vehicle Mileage
  • Fuel Economy
  • Maintenance & Repair
  • Fuel Price
  • Fueling Infrastructure
  • Financing Options

Many of the key infrastructure procurement and installation costs and daily fueling inputs will vary based on the region or site. For example, daily fueling in extreme-temperature operations (i.e., temperatures that require air conditioning or heating) will vary for buses, lowering fuel economy and increasing average fueling costs. Please see below for some additional cost variables based on the bus fuel type.

Upfront Infrastructure Costs and Daily Fueling

Battery Electric Bus (BEB)

Infrastructure costs for electric buses can differ significantly based on the type of charger and site. Any utility or facility upgrades to accommodate charging infrastructure needs will impact the overall project costs, especially depending on the scale of the transition that the fleet is considering. The cost of adding a few electric buses and chargers to the fleet looks a lot different than a full fleet transition and the accompanying upgrades. However, a longer transition timeline gives more time for capital costs to decrease as the technologies mature and potential supply chain issues are resolved.

For reference, you may want to refer to a 2020 report from the National Renewable Energy Laboratory (NREL), Financial Analysis of Battery Electric Transit Buses, which discusses parameters to prioritize when considering an electric bus investment (https://afdc.energy.gov/files/u/publication/financial_analysis_be_transit_buses.pdf). In particular, see Table 5 on page 27.

The electricity fueling cost for BEBs is location dependent. You may refer to the U.S. Energy Information Administration State Electricity Profile page (https://www.eia.gov/electricity/state/) for a snapshot of electricity prices in your state. While not captured in AFLEET, fueling costs will vary further depending on electric utility rate structure offerings such as a time-of-use (TOU) rate that allows fleets to avoid any high demand charges. Ultimately, charging off-peak with a TOU rate will lower the TCO for electric buses.

 CNG Bus

The cost of installing CNG infrastructure is influenced by station size, capacity, and the way the CNG is dispensed (i.e., fast-fill or time-fill). You may refer to an NREL report, Costs Associated with Compressed Natural Gas Vehicle Fueling Infrastructure (https://afdc.energy.gov/files/u/publication/cng_infrastructure_costs.pdf?447f42ad57) for an overview of factors to consider in the implementation of fueling stations and equipment. In particular, please refer to PDF page 11 and 12 for example applications and station sizes, and relative cost ranges.

It may be worthwhile to consider fuel price volatility of CNG when determining CNG fueling costs for TCO. For example, based on the Clean Cities Alternative Fuel Price Reports, the retail price of CNG on a gasoline gallon equivalent basis has gone up nearly 50% between January 2021 and January 2023 (https://afdc.energy.gov/fuels/prices.html). That said, fleets may have the ability to purchase CNG at lower and less variable rates than retail customers. As such, we recommend working with your local CNG provider to determine your specific fuel price contract costs for your needs.

Vehicle Cost Resources

Beyond default AFLEET values, you may be interested in the following resources for electric and CNG bus cost data. Please note that we aren’t aware of many recent publicly available resources on CNG bus costs. Additionally, it’s possible that more electric and CNG bus cost data will become available as a result of some of the federal incentive programs that have received funding under the Inflation Reduction Act (e.g., Clean School Bus and Low or No Emission Grant (Low No) Program):