The battery is the most important and most expensive component in any electric vehicle. On a used EV, checking its health before you buy is not optional, it is the single most important thing you can do. Here is exactly how.
What battery health means
Battery health is measured as State of Health , SoH expressed as a percentage. 100% is a new battery at full original capacity. 85% means 85% of original capacity remains, delivering roughly 85% of the original advertised range.
Degradation is normal, gradual, and predictable. The question for used buyers is where a specific vehicle sits on that scale and whether it suits the price being asked.
What counts as a good result
85% or above is generally healthy for a used vehicle. 75–84% is acceptable on an older or lower-priced vehicle where the price reflects it.
Below 75% should prompt careful thought and meaningful price negotiation. Below 60% is rarely worth buying except at a very significant discount for a very specific purpose.
Always adjust the advertised WLTP range figure against the actual SoH, a car listed as "up to 245 miles" with 80% SoH will realistically deliver around 185 miles under equivalent conditions.
Four ways to check
First, the in-car display. Some EVs, particularly Nissan Leaf models show battery capacity bars on the dashboard. A quick, free, immediate rough indicator.
Second, the manufacturer app. Ask the seller to show the companion app during your visit. Some apps display battery health data directly. All at minimum show state of charge and range estimates.
Third, a third-party diagnostic app. Apps such as Leafspy (for Nissan Leaf), Car Scanner, and EV Battery Check connect via a Bluetooth OBD adaptor to read detailed battery data.
For supported vehicles this is the most detailed free or low-cost option. Research which app works with your specific model before visiting.
Fourth, a professional battery health report from an EV-qualified technician. The most thorough option, worth the cost on any significant purchase or where cheaper methods return ambiguous results.
Questions to ask the seller
How was the car primarily charged home overnight, workplace, or mainly rapid chargers?
What was the daily charge limit set to? How often was rapid charging used?
Have any battery warnings appeared during their ownership?
