Used electric car: how to assess battery health

Central question: how do you assess the battery health of a used electric car before buying? The answer involves understanding degradation, asking for objective data on the battery's condition, testing the car and reading the warranty. This text is informational and does not replace a professional's assessment.

Context

The traction battery is one of the most expensive parts of an electric car, and its capacity slowly decreases over time. This loss is degradation, and it is what reduces range (the distance the car travels on one charge). A figure often cited is the battery's state of health, which compares current capacity with the original.

Mechanisms

Degradation depends on factors such as:

• Age and mileage.
• Charging habits. Frequent fast charging and charging to 100% or draining to near zero can speed up wear, according to guidance from many manufacturers.
• Temperature. Extreme heat and cold affect the battery.
• Model and technology. Thermal management systems and different chemistries behave differently.

Checks

1. Ask for the battery health report. Some manufacturers and authorized workshops offer diagnostics, and there are third-party tools of varying quality.
2. Check the warranty. See whether the battery warranty is still valid, for how long or how many kilometers, and whether it is transferable.
3. Look at the history. Records of services, accidents and module replacements.
4. Compare range. See the range shown on the dashboard at full charge and compare it with the model's original figure, remembering that weather and driving style influence it.
5. Test charging. Check that the car charges normally on slow and fast chargers, and that there are no error messages.
6. Look for signs. Sudden drops in range, dashboard warnings or irregular charging deserve investigation.

Examples

Comparing two electric cars of the same age, one has a report indicating good battery health and remaining warranty; the other presents no documents, and the seller cannot say. The first tends to carry less uncertainty. This is an illustrative example.

Limits

Range varies with weather, route type and driving, and third-party diagnostics are not always accurate. No number replaces inspection by a qualified professional and reading the warranty contract. Degradation values vary greatly by model.

Sources

Consult manuals and official manufacturer channels, authorized workshops, consumer protection bodies and independent reports on battery degradation, noting date and methodology.