Used electric car? SOH saves your money

Battery: “SOH” = state of health

During the analysis of a used electric car that at first glance looked like an extremely attractive offer, the car – despite its good visual condition, moderate mileage and fair price – turned out to be a dangerous sham. The examination of the vehicle’s battery showed a considerably worse state of health than expected. The key insight: the state of health (SOH) of an electric car battery is the decisive factor when buying a used electric car – far more important than mileage or outward condition.

The video explains that the SOH indicates how much capacity a battery still has compared with its new condition. A value of 85 % seems positive on the surface but, according to the analysis, already corresponds to roughly half of the realistic battery life. A critical range begins at around 70 % SOH, as batteries do not age linearly. As shown in the report, batteries initially lose capacity relatively quickly, then stabilise for a long time and finally reach a so-called knee point at which degradation increases abruptly.

The article further describes that as the SOH falls, the internal resistance of the battery rises, leading to more heat generation, lower power output and reduced fast-charging capability. As a result, a vehicle can already be economically worthless despite supposedly sufficient remaining capacity.

Difference between mileage and actual load

A central section of the content shows that mileage figures are of only limited value for assessing the condition of a battery. The report documents a case in which the vehicle, due to heavy trailer loads and frequent mountain driving, had in reality experienced a much higher load than the mileage suggested.

Despite its low official mileage, the battery of such a vehicle has in fact gone through considerably more energy cycles. These cycles – and not the mileage – determine the wear of a battery. Because of the load, the battery examined corresponded more to the condition of a battery with over 200,000 kilometres, although the odometer showed only about 85,000 kilometres.

Using a special evaluation tool

In the video, the author – known as “Der Akku Doktor” (the battery doctor) – highlights his free online tool, which uses community data and Tesla logger information to automatically assess whether a measured SOH is good or bad in relation to the mileage. This tool enables interested buyers to make a realistic assessment of the battery’s condition without in-depth expertise. The negative example examined in the video – a vehicle with 85 % SOH – was rated by the tool as significantly worse than the mileage would suggest. The data showed that the battery was outside the usual tolerance ranges.

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My conclusion Test, test, test …

I come to the conclusion that buying a used electric vehicle can be either an exceptionally good deal or a considerable financial mistake. As we see in the video, one very decisive factor is the state of health of the battery alone. By reading out the SOH and then evaluating it, I as a prospective buyer can determine independently and on an informed basis whether an electric car is a real bargain or a looming economic write-off – without having to rely solely on what a seller tells me.