Why Parking Conditions Matter More for Battery Degradation
- rory lee
- Oct 11
- 2 min read
When you think about it, most electric vehicles spend far more time parked than being driven or charged. It may sound surprising, but a battery continues to age even when the car is not moving.
It is similar to canned food or instant noodles with a long shelf life. They still slowly change over time. If we could freeze the battery, that would be ideal, but since that is impossible for EVs, the parking environment becomes important.
The graph below comes from a Nature Energy paper and provides two key insights.
When the average C-rate is below about 0.4, degradation becomes increasingly influenced by time-induced effects.
Even under identical conditions, some cells last longer while others degrade faster. This shows that cell-to-cell variation, or “luck of the draw,” still plays a role.
For reference, an average C-rate of 0.4 is rarely reached in city driving. It typically occurs only during sustained highway driving or fast charging. The study was conducted under continuous cycling, with charging and discharging repeated. In real-world use, where vehicles sit parked most of the time, time-induced degradation plays an even larger role.
It also helps explain why drivers who use their cars more frequently often see a longer mileage-to-degradation ratio.
Dr.EV data analysis shows that battery degradation is clearly related to the vehicle’s age.
As a personal hypothesis, one possible reason Tesla BMS issues have been unusually common in Korea this year could be related to changes after last year’s Mercedes fire incident, when many underground parking lots began restricting EV parking. As a result, more vehicles may have been left exposed to high ambient temperatures for long periods, which can accelerate degradation. This hypothesis would only hold true if the Tesla BMS issues were actually caused by cell-related problems.
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