You might think avoiding fast charging should protect an EV battery. But two high-mileage Tesla Model Ys tell a very different story — and the gap is striking. American EV commentator Branden Flasch bought a 2023 Model Y Long Range AWD that covered about 180,000 km in roughly three years. Tesla's built-in battery health test showed just 77% remaining capacity. In other words, the pack had lost about 23% from its original level.
The most curious part was hidden in the charging history. Only about 2 MWh came from fast DC stations, while the car took in more than 40 MWh through AC charging. That makes it hard to blame the degradation on constant Supercharger use. In fact, the third-party Tessie app was slightly more optimistic, estimating battery health at 80.95%.
Now for the real contrast. Another Model Y had previously been checked after 203,000 km of taxi duty — and its battery still retained about 89% of its capacity. More mileage, hardly gentle use, yet a noticeably healthier pack. That is exactly why mileage alone says surprisingly little about the true condition of a used EV.
A Recurrent study of roughly 13,000 Teslas dealt another blow to the simple theory that frequent fast charging is automatically bad for batteries. Researchers found no statistically significant difference in range degradation between cars with very high and very low shares of DC fast charging. But there is still no universal explanation: temperature, cycle depth and spending long periods at a high state of charge can all affect battery aging. With the available data, the exact cause of this Model Y's 23% loss cannot be determined.
