Range. RANGE. Range! Implicit in this answer is anxiety over the condition of the used lithium battery: Has it been abused? How much range is the battery good for? Fortunately, both the private sector and government research agencies are hot on the trail, studying in detail the residual life of used EV batteries. The researchers run production batteries through carefully controlled and quantified charge/discharge cycles, and both research sectors study real-world cars and how each model’s batteries are holding up. Fleet records have been especially useful, because drivers of fleet vehicles have no incentive to protect the longevity of the vehicle they have temporarily checked out.
The short answer from the fleet vehicle studies is endearing: most EV batteries lose range only very slowly and will therefore likely last the lifespan of the vehicle (EV performance records document real-world battery degradation rates). It is highly unlikely that a buyer of a used EV will ever need to buy a replacement battery. One relatively new startup (www.recurrentauto.com) is offering used car dealers an analysis – specific to the model and model year for sale – detailing what is known about that particular vehicle cohort (based on 9000 cars whose owners have signed up to have their battery’s performance monitored continuously). The dealers can then post the report with the car, offering any prospective buyer an authoritative third-party assessment of the prognosis of the battery’s likely range at the time of sale and into the future.
The co-founder of Recurrent, Scott Case, gave a recent talk to the Denver Electric Vehicle Council, outlining the company’s services (Recurrent charges only the dealers, not the buyers, nor private owners who want more details about their own vehicles).
Among the battery longevity tidbits that he shared:
- A 2018 Bolt battery has highly variable performance, losing about 40 miles of range after the initial break-in, but holding that diminished range fairly steady for years afterwards.
- In contrast, a 2018 Tesla Model 3 has a highly predictable range trajectory, losing only about 20 miles of range after the initial break-in, but it too holds that range for years afterwards.
- Efficiency (miles per kilowatt-hour) is a key metric, and the EPA rates the Tesla Model 3 as the most efficient EV on the road today, but under the real world conditions that Recurrent monitors (details below), Nissan Leafs get higher efficiency. This inconsistency appears to be due to the more conservative driving habits of Nissan owners, not any difference in the vehicles themselves. One listener to the presentation, who owns both a Leaf and a Model 3, confirms that he drives more aggressively when behind the wheel of the Model 3.
- Degradation factors are (in random order): age of battery (younger better), climate in which the vehicle resides (cooler better), battery temperature during charging/discharging (warmer better, up to a point), charging speed (less fast-charging better), total number of charge/discharge cycles the battery has experienced (fewer better), depth of discharge (don’t go below 30% charge state), and amount of storage at very high or very low charge states (less better). These factors have all been well confirmed in laboratory testing as well.
Given the choice between buying a used EV with many years on the battery but low miles, versus a newer EV with high mileage, Scott would prefer the higher mileage vehicle. He noted that this is the opposite tradeoff to that which regular car (internal combustion engine) buyers sensibly prefer.
The patterns are reasonably well established for batteries in general, and are now being well documented for specific EV models as well. But what about my individual car, or an individual car that you are considering buying: has it been coddled or abused? There is not much information to go on, unless the current owner choses to have their car monitored by an independent third-party such as Recurrent. In that case, the owner can get Recurrent to generate a free independent report at the time of sale, which can be shown to prospective buyers.
What does signing up with Recurrent entail? Signing up is free to the owner (Recurrent is eager to collect more data from cool climates like Colorado), and entails allowing Recurrent – through a third party which anonymizes the data for statistical analyses – to monitor your car for a specified number of times per day (usually 3) to record your odometer, charge state, charging condition, estimated range, and so forth. They ask for your zip code to determine the area’s general climate, but do not have access to your car’s GPS, so they can’t track you or your driving behavior. Owners have questioned whether this frequent monitoring itself consumes power and thereby has an effect on range, but Recurrent claims that their studies indicate that the power consumption by the thrice-daily “pings” for data is too small to measure. Owners who sign up for the thrice-daily monitoring get an exhaustive analysis each month of how their battery is holding up. Owners can also obtain a free overall summary report, typically requested at a time of sale.
Are there any costs to the owner? Potentially. I tried signing up for my 2012 Volt and found that this vehicle was designed only for 3G cellular transmissions of data, so I would have to have the dealer rip out the 3G hardware and replace it with 4G hardware (GM refused to quote a price for this swap-out: they just charged me $3000 to replace a defective chip, so they appear to be working hard to monetize EV repair revenues). Older Nissan Leafs suffer from the same short-sighted hardware obsolescence. Most other manufacturers were more forward looking in their designs (even western La Plata county was transitioning to 4G in 2012!). In addition, I was told that I would have to pay Onstar (GM’s over-the-air communication system to the vehicle) $15-$38/month to allow Recurrent to read the data from my car. However, not all manufacturers follow that mercenary practice, and some owners may prefer to pay for that service for other reasons (emergency assistance, etc.).
Recurrent claims that increasing a buyer’s confidence in the condition of a used battery appreciably raises the value of a used EV. Historically, used car sales per year are about twice the number of new car sales. Down the road, the world will need many used EVs to satisfy the full spectrum of buyers. The company claims that their mission is to expedite the transition to electric transport, a goal many of us share.
