While in classic cars, the mileage and general condition of the car determine the resale value, in addition to the type of engine and gearbox, their type and combination, in electric cars there is an additional criterion: the so-called SoH or state of health the car.battery. This must be planned to avoid surprises.
Everyone knows that a car with a diesel or gasoline engine wears out the more kilometers it travels. This logic of course also applies to electric cars, but it is not the engine that wears out, but the battery. This battery loses some of its capacity as the number of charging cycles increases. This number of charges has a much greater impact than the number of kilometers traveled and even the life of the battery. But while today the mileage of a car is recorded by the car’s odometer and stated on the car’s pass, this is not the case with the condition of the driving battery.
Standardized testing is required
Since the battery is the most expensive part of an electric vehicle and replacing it is not at all straightforward, in the near future it will be necessary for the sales report of a used electric vehicle to also include a certificate stating the state of health (SoH) or the degree of health of the battery confirmed. Such a standardized test does not exist today. There are actually several options available for battery SoH testing, but these options are not included in any law or regulations and are therefore currently only performed at the request of the buyer or seller.
It would be desirable for such a brand-independent standardized test to be introduced under government control – preferably at the European level – and to be integrated, for example, into the mandatory inspection of (used) sales at national inspection centres. Electric vehicles will then receive a statement of the SoH results of the standardized test in the inspection document and vehicle pass. This way the buyer also knows he is not buying a pig in a poke.
Batteries wear out less quickly than expected
Multiple tests by independent bodies have now shown that the deterioration of the new generation of motor batteries is much slower than initially expected. VRT.nws reports on a test by Thomas More University of Applied Sciences in which a ten-year-old Renault Zoe with 40,000 kilometers on the odometer still retained 81 percent of its initial battery capacity.
Zoë is already an old model. New electric cars use the latest battery technology with a lower degradation rate. Count on about 2 percent annually. This means that even after 10 years, 80 percent of the initial capacity will still be available.
The Thomas More test and many others show that wear is slower than the pessimists declared. Also in case, if the battery retains less than 75 to 80 percent of its initial capacity after 8 years, most manufacturers will replace it under warranty. Toyota, Lexus and Mercedes-Benz (for larger models) have a 10-year warranty on the drive battery. A battery that is less than 80 percent of its initial capacity is considered “replaceable” or “repairable.” It is not always necessary to replace the entire battery, but it may be sufficient to replace some defective or less performing battery modules individually. This is usually under warranty up to 8 years if the capacity loss is not user caused.
A state of charge between 15% and 80% is ideal
The user impact is great. If possible, it is recommended to keep the battery between 15 and 80 percent charged as much as possible and recharge to 80 percent instead of reaching 100 percent every time. The latter should be reserved for charging sessions that follow the flight. Battery wear is primarily related to the number of complete charging cycles. If you partially charge the battery three times, this is equivalent to one full charging cycle so your battery will last longer. 
It has been said for some time that fast charging (at DC chargers along the highway, for example) is bad for the battery, but this has not been proven through testing. The current generation of batteries has little or no negative impact on this.
