Electric cars

Why Electric Car Calendar Age Matters More Than Model Year

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Buying or selling a used electric vehicle is inherently different from its ICE counterpart. The main reason is that the battery, which is the most expensive part of any electric vehicle, is difficult to evaluate. Batteries age differently from combustion engines. For example, Recurrent’s research found that an odometer isn’t a particularly accurate indicator of battery health. It’s no better than fourth or fifth best, depending on the manufacturer.

The high-voltage lithium-ion batteries that power electric cars naturally degrade over time and charge cycles. This topic has been widely front cover and my team compared capacity vs power vanish.

Today we are releasing a preview of new data on calendar age as a predictor of vehicle range and show how this differs from Model year for two reasons :

  1. Vehicles of the same model year may be produced up to 12 months apart.
  1. Each time a battery is replaced for any reason after initial production, the calendar age clock resets.

To illustrate the first point, here is new data that clearly shows the difference between the date of manufacture (which likely closely matches the calendar age) and the model year in terms of range degradation for two example families of vehicles (grouped by similar battery configurations).

In the graphs above, you see the same range degradation data plotted left and right. However, on the left side, the x-axis uses “model year” to represent the age of the vehicle, using a simplifying assumption that each model year vehicle was produced on January 1 (in the middle of the model year).

On the right side, the actual manufacturing date is used. You can see how smoother and more continuous the decay curves are in the plots on the right. Indeed, the degradation of autonomy is a factor of civil age and not of model year. Whether a vehicle is a 2017 or 2018 matters less than how long the battery has been manufactured.

As an EV shopper (new or used), to maximize the chances of getting a good battery, imagine you’re in the dairy section of the supermarket, looking for the carton of milk with the longest expiration date.

In fact, doing this as an EV buyer is a painstaking and imperfect process, but thankfully Recurrent factors the “birthdate” of vehicles (and the batteries themselves) into its reports.

What about battery replacements?

For some EVs – both as part of general recalls and due to specific warranty replacements – the calendar age of the battery is starting to really deviate from the car’s production date.

More recently, Chevy has been replacing batteries in Bolts due to initial manufacturing QA issues. In addition to the safety benefit of the booster, owners get a huge increase in range with their replacement batteries.

The graph above tracks a cohort of the same vehicles in the recurring community, one year apart, before and after the recall. Even though these cars have higher odometers and older model years than 2021, they average 40 miles more range in comparable weather conditions than they did a year ago.

The X-axis in this graph is the estimated range at 100% load and the Y-axis is the frequency of readings for 479 Bolts subscribed to Recurrent’s platform. We track battery replacements on all EV models, both as a result of recalls and on an ad hoc basis. When/if an EV battery is replaced, the vehicle should be worth a lot more, but you’ll want to have a plan in place to demonstrate that value. Fortunately, these 497 owners do.

Scott Case is CEO of Recurrent. Recurrent was founded in 2020 with the goal of providing more transparency and trust in used electric cars. Through its comprehensive battery reports for owners, buyers and sellers of electric vehicles, it aims to accelerate the global adoption of electric vehicles. To learn more about Recurring, visit https://www.recurrentauto.com/.