SoH Value in EVs: Importance for Valuation and Battery Diagnostics

The State-of-Health (SoH) is a metric that describes the general state of health of a rechargeable battery. Unlike the State-of-Charge (SoC), which merely indicates the current charge level, the SoH value compares the battery's current capacity and performance with its original specifications when new. A brand-new battery has an SoH of 100 percent. Over time and with increasing use, this value decreases due to chemical aging processes and cyclical stress.

Determining the SoH value is complex, as it cannot be measured directly by a single sensor. It is the result of mathematical models that incorporate various parameters such as internal resistance, capacity in kilowatt-hours (kWh), and the voltage stability of the individual cells. For an appraiser, the SoH value is the central criterion for assessing the remaining service life and economic value of an electric vehicle. A low SoH value indicates advanced degradation, which directly reduces the vehicle's range and increases the risk of a costly battery failure.

DIAVAG uses the Premium Battery Test for this analysis. This does not merely read out the value provided by the battery management system (BMS). Instead, a deeper diagnosis of the cell balance and the charging curve is performed. This is necessary because manufacturer BMS values are often rounded optimistically. An independent appraisal ensures that the actual condition of the hardware is documented objectively, with experts controlling the final conclusions. This builds trust in transactions between private individuals as well as in commercial trade.

The focus in electric vehicle valuation has shifted. While mileage and the service booklet dominate for combustion engines, the battery is the value-determining element for an EV. Since the cost of a replacement battery can range between 10,000 and auf Anfrages depending on the model, any deviation in the SoH value significantly affects the market price. A vehicle with an SoH of 92 percent achieves a considerably higher price on the market than an identical model with a value of 84 percent.

For sellers, a DIAVAG value appraisal provides a solid basis for negotiation. It proves in black and white that the battery has been treated with care, for example through slow charging within the optimal window between 20 and 80 percent. Buyers, in turn, use the appraisal as protection against hidden defects. Purchasing a used EV without proof of SoH carries a high financial risk, since degradation is not visible from the outside.

Especially with high-value assets such as a Tesla Model S or a Porsche Taycan, measurement precision is crucial. DIAVAG integrates the Premium Battery Test as standard into the premium appraisal. This distinguishes the service from simple algorithm-based estimation tools that rely solely on statistical averages. An on-site appraisal by a BVSK-compliant expert takes into account the individual condition of the specific vehicle. This is particularly important in legal disputes, inheritance matters, or divorces, where a court-usable value must be determined.

DIAVAG's inspection process is designed for maximum efficiency and technical depth. The appraiser carries out a standardized workflow that begins with connecting an OBD2 scanner. This reads the fault memory and real-time parameters of the high-voltage system. But the diagnosis goes far beyond simply reading out data. The Premium Battery Test analyzes the cell voltages and identifies outliers in the cell balance. Uneven voltage between cells is often an early warning sign of a defect or accelerated aging.

In addition to the digital diagnosis, physical measuring instruments are used. A coating-thickness gauge checks the body for repainting and accident damage that could indirectly have affected the battery system as well. A digital multimeter is used to check the electrical auxiliary systems. The entire documentation is carried out via a standardized photo sequence that is captured in a tamper-proof manner. This process takes less than 15 minutes on site, making the service particularly attractive for busy private customers and dealers alike.

The result is a detailed PDF report signed by a senior inspector. It contains not only the SoH value as a percentage but also an assessment of the remaining capacity in kWh and a comparison with the manufacturer's specifications. Optionally, the report can be secured with a notarial hash on the Polygon blockchain. This guarantees that the data cannot be altered after creation. This technological combination of on-site expertise and digital security with full source traceability sets new standards in vehicle valuation.

An appraisal is only as valuable as its legal standing. DIAVAG therefore relies on appraisers qualified according to the standards of the BVSK (German Federal Association of Independent Vehicle Experts). This ensures that the appraisals are methodically correct and professionally sound. For lawyers and notaries, this is an essential criterion for using the documents in court disputes or estate administration.

Another distinguishing feature is the pursued inspection activity in accordance with ISO/IEC 17020 Type A. This standard represents the highest level of independence. As a Type A inspection body, DIAVAG may neither trade in vehicles nor carry out repairs nor broker insurance. This strict separation guarantees that the appraiser's judgment is not influenced by self-interest. Unlike purchase platforms that often set the value artificially low in order to acquire the vehicle cheaply, DIAVAG delivers an objective market value.

In legal matters, for example after accident damage to the high-voltage battery, independence is decisive for acceptance by insurers. The appraisal serves as proof of the replacement value or the diminished market value. For complex legal questions, DIAVAG always refers clients to cooperation with specialized lawyers or notaries, but provides the necessary data basis for their work through the technical findings. Compliance with the JVEG (Judicial Remuneration and Compensation Act) serves as a guiding framework for the remuneration and formal structure of the appraisals.

The regulatory landscape for EV batteries is changing drastically. From February 2027, the EU Battery Passport will become mandatory for all new batteries in electric vehicles and stationary storage systems. This digital passport is intended to contain information on the origin of the raw materials, the carbon footprint, and above all the current condition of the battery. DIAVAG is already prepared for these requirements today and integrates relevant data points into its appraisals.

The aim of the EU regulation is to promote the circular economy and increase transparency in the used market. A standardized SoH value will become a mandatory disclosure. For owners of existing vehicles, this means that professional documentation of battery condition is becoming more important in order to remain competitive. DIAVAG offers a bridging solution here by evaluating existing batteries according to modern standards, even if they do not yet have a factory-issued digital passport.

In addition to the battery regulation, standards such as the EU Machinery Regulation 2023/1230 also play a role, particularly when it comes to assessing electric construction and agricultural machinery. DIAVAG covers a total of seven asset classes, including home storage systems and micromobility such as cargo bikes. This breadth is a unique selling point compared to classic inspection organizations such as TÜV or DEKRA. The standardization of the inspection workflow makes it possible to offer legally sound SoH analyses at a fixed price for these specialized assets as well.

The return of a leased electric vehicle often leads to disputes about the condition of the battery. Lessors frequently demand compensation for excessive wear. Without an independent appraisal, the lessee is in a weak position. A DIAVAG appraisal shortly before the return documents the exact SoH value and technical condition. If the value is within the normal range for the age and mileage, unjustified claims can be effectively rebuffed.

In insurance cases, especially after accidents involving ground contact, the integrity of the battery is the main concern. An externally undamaged housing does not guarantee internal safety. DIAVAG's Premium Battery Test can detect anomalies in cell voltage that indicate internal short circuits or mechanical deformation. Insurers use these appraisals to decide whether a repair is economically viable or whether the vehicle is a total loss. Since DIAVAG does not sell repairs, its judgment is credible to the insurer.

SoH measurement is also relevant for home storage systems used with photovoltaic installations. When selling a house, the value of the installed technology must be determined. A PV storage system with an SoH of 60 percent has little remaining value, while a well-maintained system increases the value of the property. DIAVAG offers the premium appraisal for this purpose, carried out on-site at the storage system's location. This gives both the buyer and the seller of the property certainty about the functionality of the energy technology.

Tamper resistance of documents is a central aspect. DIAVAG uses modern technologies to guarantee the integrity of its appraisals. Every PDF report created can optionally be secured with a cryptographic hash on the Polygon blockchain. This creates an immutable timestamp and proves that the document has not been modified since it was created by the senior inspector. For buyers of a vehicle, this is an important safety feature to rule out forged SoH certificates.

Data is stored in a GDPR-compliant manner on servers within the European Union. This is particularly important for commercial customers such as fleet operators and dealerships, who manage large amounts of vehicle data. The standardized photo documentation also ensures that the vehicle's condition at the time of inspection is fully documented. Each photo is linked to metadata such as time and location, which increases its evidentiary value in the event of a dispute.

The digital workflow enables DIAVAG to deliver the completed appraisal the same day. Once the appraiser has uploaded the data into the system on site, it is reviewed by a senior inspector at headquarters. This process guarantees consistently high quality, regardless of whether the inspection takes place in Hamburg, Berlin, or Munich. The combination of on-site human expertise and digital quality assurance minimizes sources of error and speeds up transaction processes for all parties involved.

For commercial players such as dealerships and fleet managers, DIAVAG offers specialized terms and technical interfaces. From a volume of 50 appraisals per month, individual prices are negotiated. A key advantage for dealers is the connection to existing Dealer Management Systems (DMS) via an API. This makes it possible to integrate appraisals directly into the inventory process and automatically transfer the SoH value into online listings.

Fleet operators use regular SoH measurement for residual value tracking. Since battery degradation varies greatly depending on the driving profile, continuous monitoring provides important data for optimal fleet management. A vehicle with faster degradation can be replaced early or transferred to a less demanding driving profile. This maximizes the overall value of the fleet and prevents unpleasant surprises at the end of the lease term.

DIAVAG also offers a partner program for independent appraisers. As part of the partner program, appraisers can purchase the hardware case including the necessary software. This allows them to incorporate the standardized DIAVAG workflow into their own service portfolio. The case contains all the necessary tools, such as an OBD2 scanner, a coating-thickness gauge, and the Premium Battery Test. This drives the professionalization of battery diagnostics across the entire industry.

The quality of an appraisal depends significantly on the hardware used. The DIAVAG hardware case is the result of years of experience in vehicle inspection. It contains calibrated measuring instruments specifically tailored to the requirements of electric vehicles and other modern assets. The centerpiece is the diagnostic interface for the Premium Battery Test, which enables in-depth communication with the battery management system. Unlike inexpensive consumer devices, this hardware delivers precise raw data that is essential for a BVSK-compliant appraisal.

In addition to battery diagnostics, the set includes a precise coating-thickness gauge for detecting accident damage on aluminum and steel bodies. A digital tread-depth gauge documents the condition of the tires, while a multimeter is available for testing the 12V onboard electrics and charging infrastructure. The hardware is robustly built and optimized for mobile use at the customer's location. This enables the appraiser to gain a complete picture of the vehicle's condition in the shortest possible time.

The accompanying software guides the user step by step through the inspection process. This ensures that no relevant inspection point is forgotten and that all data is recorded in the correct format. Automatic synchronization with the DIAVAG cloud enables rapid evaluation by senior inspectors. For self-employed appraisers, this investment represents an entry point into the growing market for e-mobility valuation, without them having to develop their own complex IT infrastructure.