It had been about a year since I started driving a Nissan Leaf, and I found myself wondering what battery degradation—a loss of usable charge capacity—actually means. I had also heard rumors about a particular style of “recovery driving” that supposedly restores a Leaf battery. Was there any truth to it? I decided to investigate.
My conclusion was that lithium-ion batteries degrade through several different mechanisms, and certain conditions accelerate those mechanisms. Avoiding those conditions can extend a battery’s useful life. But a lithium-ion battery does not recover: the rumors about “recovery driving” were an urban legend.
Below I summarize how to extend battery life, what causes degradation, and why recovery driving cannot reverse it.
How to Help an EV Battery Last Longer
Here are the practical measures I found.
Keep the Battery Near a Moderate Temperature
- Avoid leaving the car in direct sunlight. Indoor or covered parking is preferable to an exposed rooftop parking lot.
- Reduce your speed when possible. Even on an expressway, cruising at around 80 km/h in the left lane is practical, and it also improves energy efficiency.
- An underground mechanical parking garage stays relatively stable in temperature through both summer and winter, which is friendly to an EV battery. It is comfortable for people too, because the cabin starts near 25°C.
Keep the State of Charge Between About 15% and 90%
- Do not let the state of charge fall below 15%, and especially avoid reaching 0%.
- If you charge to 100%, begin using the car soon afterward.
- Drivers who charge at home tend to leave the battery at 100%, so avoid doing that when possible.
When Fast-Charging, Stop Early If You Can
- Two short 15-minute fast-charging sessions are gentler than one continuous 30-minute session.
If You Have Time, Use a Lower-Power Fast Charger
- Fast chargers at dealerships range from roughly 44 kW to 150 kW, while those at convenience stores and roadside stations are often around 20–30 kW.
- Regular AC charging would be even better, as long as the battery is not left sitting at 100%.
Accelerate Gently
- Be especially careful about demanding high power when the state of charge is low.
What Causes Battery Degradation
Here, degradation means a reduction in SOH (state of health), where the battery’s usable capacity when new is treated as 100%. I am not discussing reduced maximum power output. The following is deliberately simplified, with the risk that simplification may introduce misunderstandings.
Cracks Form Inside the Battery Materials
- High temperature and fast charging cause normal expansion inside the battery. Faster expansion produces larger microscopic cracks.
- Even apart from expansion, the high current involved in fast charging can contribute. High output during sudden acceleration can have a similar effect.
Metals Dissolve into the Electrolyte
- The amount of dissolved material rises sharply when the state of charge is extremely low (near 0%) or extremely high (near 100%).
- High current and sudden acceleration may also contribute.
Unwanted Material Forms at Internal Interfaces
- This material accumulates over time even when the battery is not being used. The effect becomes more pronounced at a 100% state of charge or at high temperature.
- Fast charging may also accelerate this process.
Why “Recovery Driving” Cannot Restore the Battery
“Recovery driving” refers to a particular driving pattern claimed to revive the battery. With the Leaf, supporters point to an increase in the SOH value reported by the Leaf Spy app through a device connected to the OBD port. But that SOH figure is not a direct physical measurement; it is an estimate calculated by the vehicle’s computer.
My conclusion is that recovery driving is an urban legend. No pattern of charging or discharging can reverse the physical degradation mechanisms described above in the conventional lithium-ion battery used by the Leaf.
Recovery is not possible, but slowing further degradation is. The sensible approach is to follow these practices where they are convenient, without going to unreasonable lengths.
The following are the sources I used.
Sources
These are the main sources behind my conclusions.
1. A Video Explaining Battery Degradation Scientifically
Battery Degradation Scientifically Explained—EV Battery Tech Explained
The video has Japanese subtitles, but the subject matter is highly technical and the relationship between the narration and diagrams can be difficult to follow. I watched it three or four times.
2. Information from a Battery Manufacturer
Battery Manufacturer Information and Technical Notes on Batteries and Electric Power
Despite being described as “trivia,” the site provides quite specialized technical information.
3. SUPER Science: The Science of Batteries That Will Change the World
SUPER Science: The Science of Batteries That Will Change the World
I bought the book because I thought I needed a broader reference. The chemical formulas made it difficult to read straight through, but it explains battery mechanisms from the oldest batteries in history to new types that have not yet entered practical use.
4. Research Paper: “Simultaneous Estimation of State of Charge and Parameters for HEV/EV Lithium-Ion Batteries”
Simultaneous Estimation of State of Charge and Parameters for HEV/EV Lithium-Ion Batteries
The paper was extremely difficult for me to read, and I could not follow the equations at all. After going through it about three times, however, I understood just how difficult it is even to estimate a battery’s state of charge.
A copy can be requested from Japan’s National Diet Library, including by mail.
