Question of the week: How can you check battery condition a used EV?
Fri, 19 Dec 2025
Dear Honest John,
"If you are buying a used electric car, how can you check the condition of the battery and how much charge it is holding when it is fully charged?"
- DL
Dear DL,
As the number of EVs on the secondhand market increases - along with the age - battery condition has become a key factor for buyers. But gaining access to that information is not as straightforward as looking at a service history.
The condition of an electric car battery is referred to as state of health (SOH) and is usually expressed as a percentage. So when new it would be at 100%. It's similar to how a mobile phone battery life works.
But it is important to distinguish SOH from state of charge (SOC). As an example, a brand-new 50kWh battery that is charged to 100% (SOC) would hold 50kWh, or very close to it.
However, an older 50kWh battery that has a SOH of 80% could only hold a maximum of 40kWh - 80% of 50kWh - even when charged to 100% SOC. This is why battery health is important information as it will give an indication of what range you can expect from a fully-charged battery.
If you are buying from a dealer they should provide this information for you or you can ask them for a test to be carried out where a diagnostic tool or specific device to connect to the vehicle and obtain the information. If you are buying used then we would suggest having the vehicle inspected so the battery can be tested, or there are options such as ClearWatt which is an app which can provide this information.
Don't simply trust the seller when they say it gives a certain mileage when fully charged as that does not illustrate the condition of the battery.
