Buying or selling a used EV is inherently different from its ICE counterpart. The primary reason is that the battery, which is the most expensive part of any electric vehicle, is hard to evaluate. Batteries age differently than combustion engines. For example, Recurrent’s research has found that an odometer is not a particularly accurate indicator of battery health. It is no better than fourth or fifth best, depending on the manufacturer.
The high voltage lithium-ion batteries that power electric cars naturally degrade with time and charging cycles. That topic has been broadly covered before and my team has compared capacity vs power fade.
Today, we’re publishing a glimpse of new data on Calendar Age as a predictor of vehicle range and show how that’s different from Model Year for two reasons:
- Vehicles in the same model year can be produced up to 12 months apart.
- Anytime a battery is replaced for any reason after initial production, the calendar age clock resets.
To illustrate the first point, here’s new data that vividly shows the difference between manufacture date (which presumably aligns closely with calendar age) and model year in terms of range degradation for two example vehicle families (grouped by similar battery configurations).
In the charts above, you see the same range degradation data plotted on the left and on the right. However, on the left-hand side, the x-axis uses “model year” to represent vehicle age, using a simplifying assumption that every vehicle of a Model Year was produced on January 1 (the middle of the model year).
On the right-hand side, the actual manufacture date is used. You can see how much smoother and more continuous the degradation curves are in the right-hand plots. This is because range degradation is a factor of calendar age, not model year. Whether a vehicle is a 2017 or 2018 matters less than how long ago the battery was manufactured.
As an EV buyer (new or used), to maximize the chance of getting a battery that’s in great shape, pretend you’re in the dairy section of the supermarket, looking for the carton of milk with the furthest out expiration date.
Actually doing this as an EV buyer is a pain and an imperfect process, but fortunately, Recurrent takes into account the “date of birth” for vehicles (and batteries themselves) in its reports.
What about battery replacements?
For some EVs — both as a part of broad recalls and due to specific warranty replacements — the calendar age of the battery pack starts to really diverge from the production date of the car.
Most recently, Chevy has been replacing battery packs in Bolts due to initial manufacturing QA problems. In addition to the safety benefit of the recall, owners are getting a huge range boost with their replacement batteries.
The chart above follows a cohort of the same vehicles in the Recurrent community, one year apart, pre- and post-recall. Even though these cars have higher odometers and older model years than they did in 2021, they are getting on average 40 miles more range in comparable weather conditions than they did a year ago.
The X-axis in this chart is the estimated range at 100% charge and the Y-axis is the frequency of readings for 479 Bolts subscribed to Recurrent’s platform. We track battery replacements across EV models, both as a result of recalls and on a one-off basis. When/if an EV battery is replaced, the vehicle should be substantially more valuable, but you will want to have a plan in place to demonstrate that value. Which, luckily, these 497 owners do.
Scott Case is CEO of Recurrent. Recurrent was founded in 2020 with the goal to provide more transparency and confidence in pre-owned electric cars. Through its comprehensive battery reports for EV owners, buyers and sellers, it aims to accelerate the overall adoption of electric vehicles. To learn more about Recurrent, visit https://www.recurrentauto.com/.