The secondary market for electric cars in Poland is developing rapidly, which means more and more people are looking for deals in second-hand listings. However, unlike combustion engine cars, where we mainly check for oil leaks or suspension play, the key element here is the condition of the traction battery. If you are currently buying a used electric car, be sure to learn how to check the battery SOH in a used electric car and avoid a costly mistake that could turn your investment into a huge service expense. SOH, or State of Health, is an indicator that tells us how much of the battery’s factory capacity remains available to the driver.
Why is SOH more important than the car’s mileage?
In the world of electric cars, the odometer does not always tell the truth about the technical condition of the most important component. A lithium-ion battery degrades not only through driving, but primarily through the improper habits of the previous owner, such as frequently charging to 100% and leaving the car in the cold with a discharged battery. That is why, when you buy a used electric car, you must know how to check the battery SOH yourself, because a car with low mileage that was constantly charged only at fast DC stations may be in worse condition than a unit with higher mileage charged calmly at home from a wallbox.
The OBD2 method, or become your own diagnostician
The most accurate way to quickly verify the condition of the cells is to use a simple diagnostic interface plugged into the OBD2 port. This small device, which in combination with a suitable smartphone application, such as Car Scanner or one dedicated to specific brands like LeafSpy, extracts hidden data directly from the Battery Management System (BMS). Thanks to this, you can see not only the overall SOH percentage result, but also the differences in voltages between individual cells. If these differences are large, it may mean damage to a specific module, which is a warning sign before purchasing. This is the most effective method to check the battery SOH yourself and avoid a costly mistake before signing the contract.
Range test and “Guess-o-meter” – How to check the battery SOH in a used electric car in practice
If you don’t have an OBD2 reader on hand, you can perform a simplified road test. Charge the car to full and check what range the onboard computer predicts, often called by users the “Guess-o-meter”. Compare this value with the factory data for this model, taking into account the current ambient temperature – remember that in winter the range will naturally be smaller. It is also worth driving a dozen kilometers and observing whether the charge percentages drop linearly. Sudden jumps, for example, a drop from 20% to 5% in a minute, are clear proof that the battery has seen better days and its actual capacity deviates from the declared one.
Professional certificates and manufacturer’s warranty
For those who want to be 100% sure, there are professional certified tests that can be performed at specialized service centers. Companies like Aviloo offer advanced diagnostics that involve a full battery discharge cycle while driving, which gives the most objective SOH result. When buying, it is also worth checking the service book for the battery warranty – most manufacturers offer protection for up to 8 years or 160,000 kilometers, guaranteeing that the SOH will not drop below 70%. Having such a document is the best insurance policy when buying a second-hand car.
Common sense when buying
Remember that an electric car is a very durable construction, but its heart is the battery, which needs to be taken care of. If you take a moment to check the battery SOH yourself and avoid a costly mistake, you will gain confidence that your new purchase will serve you trouble-free for years. Good battery condition is not only a longer range, but also a higher value of the car when reselling later. Don’t be afraid to ask the seller about the possibility of connecting a computer or performing a longer road test – an honest owner will have no problem with this, and you will be able to enjoy driving without worrying about the condition of your cells.