As more electric vehicles hit the used-car market, dealers and buyers are starting to ask about the health and longevity of their batteries.

But there is a dearth of information. The auto industry lacks a standard method and set of metrics for reporting battery health to shoppers of used EVs. For now, it’s buyer beware.

“It’s a problem,” said Gabriel Shenhar, associate director of the auto test program at Consumer Reports. “We get that question quite a bit” from readers but “dealers and manufacturers are loath to share data.”

“I’d like to see something more robust and assuring for used-EV buyers,” Shenhar said.

To be sure, a lack of information about a particular vehicle’s history has long been an issue in the used-car market. Buyers don’t see metrics on the wear of engines and transmissions in internal combustion vehicles.

But the battery health question has taken on more urgency with the Inflation Reduction Act. The legislation includes a used-EV purchase credit of up to $4,000 or 30 percent of the price, whichever is lower.

The credit only applies to used EVs sold by licensed dealers. Battery packs are the priciest component in any EV, with replacements hitting five figures. Dealers will need to be prepared to discuss the health of used batteries with anxious potential buyers.

The averaged data approach

Recurrent, a Seattle company that tracks the burgeoning EV market, has proposed a solution. It has collected data from more than 12,000 battery-electric and plug-in hybrid electric vehicles across 55 different models operating in all 50 states.

The company continues to build its database and is modeling average battery capacity loss over time. Its analysis suggests capacity varies largely with total miles covered. Repeated use of DC fast charging also degrades capacity more quickly, Scott Case, Recurrent’s CEO, told Automotive News. He cited examples of EVs used by ride-sharing drivers that may be fast-charged as often as four or five times a day.

Recurrent is partnering with Edmunds.com to integrate battery life data into the online car shopping website. Based on model, shoppers interested in purchasing a particular VIN will see aggregated data on the health and range of the batteries in used EVs with similar miles.

But Recurrent’s approach has limitations. First, an average battery condition based on hundreds of examples of one model doesn’t address the core question: What’s the battery condition of the specific EV the shopper is considering buying?

Second, data provided to Recurrent is limited to statistics an automaker chooses to make available through the onboard diagnostics II port in a vehicle. That includes the battery’s energy capacity over time. But it omits data on the health of underlying battery cells, voltage traces or charge curves.

Others are looking to plug the data gap. J.D. Power and Motorq, a vehicle analytics company, said Wednesday they have formed a partnership to measure battery health.

They will provide EV owners and buyers with an independent measurement of the health of a specific vehicle’s battery, compared with its stated health when new. Individual vehicles that achieve a previously specified score will receive a J.D. Power validation.

“The most useful way of measuring the health of an EV battery is to see how it performs in the real world,” Arun Rajagopalan, co-founder and CEO of Motorq, said in a statement.

What data should automakers have?

Automakers can or may have access to significant data on battery health, but some collect more than others. Voltaiq, a Cupertino, Calif., software company whose products record and aggregate details on the material sources, chemistry, electrical behavior and history of each cell as it is produced, suggested most automakers could collect more data than they do today.

Voltaiq CEO Tal Sholklapper said that an EV mostly charged at the same charging station — at an owner’s home overnight, say — could provide a battery health check by logging its response to the same charging input over time: Does it still charge at original rates, or has the battery degraded so it charges more slowly?

Charging data can be logged by the vehicle or a telematics plug-in, then sent to a data repository.

Sholklapper said Voltaiq assumed this data would be available from vehicles when the company started in 2012. “The reality was that most OEMs didn’t have enough instrumentation on the battery packs to see about individual battery cells or modules,” he said.

Over time, batteries got the needed sensors — but makers had to add telematics hardware to upload high-fidelity data from the vehicle. Now, Sholklapper said, they largely have the right instrumentation and telematics on the vehicles. The next major challenge involves trading off acquiring enough data with the cost of daily cellular connection from the car to the data warehouse.

“Once you have that data, it’s a lot of information across many vehicles,” he said. The final step is “building the software tools and automation to actually analyze that.”

What could be vs. what is

Automaker practices for collecting data on used batteries vary. General Motors collects data, with customer consent, on battery capacity, charging events, state of charge and other diagnostic information via OnStar.

“We’ll have more to share in the future” on making that data available to owners and shoppers, said Natalee Runyan, senior manager in GM’s electrification communications group.

Ford declined to provide testing details.

“A Ford dealer’s checklist for pre-owned EV sale includes parameters that also apply to gas-powered products,” said Charles Poon, global director of electrified systems engineering at the automaker. “Specific to EVs, we [inspect] cooling systems, charging systems, vehicle cluster and underbody damage — including the battery.”

Hyundai assesses battery capacity via a scan tool used by its dealers. In the future, the automaker plans to publish the battery pack’s state of health on the window sticker or in the inspection report of certified pre-owned vehicles, said spokesperson Miles Johnson.

VW collects no data on battery condition during vehicle operation, said Mark Gillies, Volkswagen Group of America spokesperson. But its dealer diagnostic tools offer two tests. The first, which takes several hours, is part of the certification process for a certified pre-owned vehicle. A shorter second test provides current state of health (in percent of original capacity) that can be released to customers who may, for instance, question the range of a vehicle.

All four automakers warrant batteries against total failure for eight years or 100,000 miles. Hyundai and VW said if capacity falls below 70 percent of the original battery, the pack would be replaced under warranty. GM’s warranty is higher — 75 percent of original capacity.

Tesla’s claims

Tesla has said little publicly about battery life, although CEO Elon Musk claimed in a 2019 tweet that Model 3 batteries would last 300,000 to 500,000 miles — without specifying the meaning. But an informal survey crowdsourced to Model S drivers six years ago suggested batteries retained 90 to 95 percent of their original energy capacity after close to 100,000 miles.

Demands for battery and other operating data may increase. Such data would encompass not only battery health, but driving habits and more on how the car is used. U.S. Rep. Earl Carter, R-Ga., has formed a Congressional caucus to look into issues of vehicle data access as well.