Battery certificates for electric cars: sometimes now mandatory at mobile.de

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Actually, buying a used electric car seems tempting. Perhaps as a second car for short trips to sports, to the office, or to the supermarket? A Renault Zoe for 7000 Euro, for example. Or a VW ID.3, which is now available for under 15,000 Euro. The question mark is the traction battery: What if the most valuable component, the battery, is worn out or damaged? To check this, there are certificates, and these must now be uploaded in the listing on the used car portal mobile.de if they are advertised as a feature.

So it is no longer enough to just claim that a certificate exists. Professional car dealers were informed of the change, which has been in effect since November 1st, via email. Under the heading “Strengthening customer trust and increasing visibility”, mobile.de clarified what it is about: Of course, it is not mandatory to offer a used electric car with a battery certificate. However, anyone who checks the box “with certificate” must also upload it transparently. This is an advantage for both buyers, who gain more clarity, and sellers, who can sell an electric car more easily this way.

Healthy, worn out, or defective

We have described in detail at heise Autos how to read a typical battery certificate: The State Of Health (SOH) indicates how many percent of the original energy content can still be drawn. This can be, for example, 96, 87, or 74 percent. Suspicion is warranted if 100 percent is shown; this is not credible for used cars. Almost more important than wear and tear is the assessment of the entire battery system: if individual cells in the pack are weakened or defective, that is a problem.

The nice thing about electric cars is that such limitations or defects can be precisely and reliably identified—provided the seller is willing to invest the money. A certified battery test can cost 100 euros. What does the provider do if a hidden defect becomes apparent in this way? Is it smarter not to do an analysis?

Small proportion of listings with battery certificate

The pressure to act comes from the market itself: Older electric cars are not fast movers, as particularly sought-after used cars are called in jargon. The portal mobile.de has made step-by-step improvements to change this situation: For some time now, you can check the box “only electric cars” in the quick search on the homepage. Of the almost 1.5 million listings, there were just under 82,000 left on the day this article was researched.

In the detailed search, searching for electric cars opens up another filter: the range can be defined, the battery capacity, or the charging time. Here, interested parties can also check the box “with battery certificate”. This leaves 17,503 vehicles, which corresponds to 21.4 percent at the time of the search. This proportion is steadily increasing; in August it was still 17.5 percent.

Few ownership changes

It is not a bold prediction that used electric cars without a battery certificate will be much harder to sell in the medium term. However, the market is still in the ramp-up and professionalization phase. In 2025, according to the Federal Motor Transport Authority, 2,110,348 passenger cars were newly registered up to and including September, of which 382,202 were electric cars (18.1 percent). In terms of ownership changes, which is the official term for used car purchases, there were 4,952,038 passenger cars in the same period, of which only 166,988 (3.4 percent) were electric. This clearly shows the statistical effect that electric cars were still a niche product ten years ago, and a slowly increasing number is added annually.

The market for used electric cars is just forming, and this is an ongoing process. A spot check on mobile.de, sorted by listing date, for example, yielded a 300 kW Volvo XC40 with first registration 8/2021, 121,800 km on the clock and an SOH of 95.3 percent. So the Volvo still has 71.4 of the original 75 kWh in its traction battery. That's a good value, especially since the cell voltage diagram indicates a healthy overall system. The asking price: 26,999 Euro. Or how about an Opel Mokka from 6/2021? The seller is asking 15,999 Euro, and with a mileage of 48,410 km, 41.1 kWh means 93.3 percent of the original condition is still present.

It should be noted with these figures: At Aviloo, 100 percent is only the 100 percent that the driver sees. The company is strict about these things. An ID.3 with 58 kWh net has only 54 kWh there, because the buffer below zero percent is not included, and it's like that everywhere.

Buyers must understand their power

Due to the November 1st deadline, many existing listings can be found where no certificate has been uploaded yet. This will resolve itself. While some sellers adhere to the rule, by no means all of them do. This needs to improve. mobile.de does not want to and cannot be too rigid, after all, the portal wants to be a partner for both sides: for sellers and buyers.

So it remains up to the buyer to decide whether they insist on a battery certificate or not. Theoretically, an interested party could also rely on the factory warranty, which lasts eight years for most manufacturers. Most used electric cars are within this period. In practice, however, it can be extremely tedious to prove battery damage and enforce warranty claims. The clear recommendation remains to prefer a used electric car with a transparent battery certificate.

Even on mobile.de's main competitor, the portal autoscout24.de, there is an option to filter for “battery certificate” in the equipment list. The results clearly show that less pressure is exerted on sellers here: the result of a battery test is in some cases published as part of the photo gallery or described in the body text. However, the usual case is that nothing is found, and the interested party has to ask the seller.

Electric cars are just cars

All in all, the realization remains that electric cars can offer a transparency in used car purchases that simply did not exist or does not exist with combustion engine cars. How long will the clutch last? How worn are the synchronizer rings in the gearbox? Is the camshaft worn? At least with the traction battery of an electric car, there is a technical possibility for clarity. In addition, used car buyers should of course pay attention to other components such as the charger (e.g., Hyundai ICCU or Stellantis) and all other components that make up a car. Without a thorough check of tires, brakes, and indications of previous damage, no candidate should be purchased, regardless of the drive.

(dmk)