Battery Test for EVs: Independent Diagnosis and SoH Report

DIAVAG's Premium Battery Test differs fundamentally from the simple fault-memory queries often carried out in workshops. The expert uses a specialized OBD2 scanner in combination with dedicated diagnostic software to communicate directly with the vehicle's battery management system (BMS). This retrieves not just superficial data points, but analyzes a wide range of parameters in real time.

A central aspect is determining the State of Health (SoH). This value indicates the remaining residual capacity of the battery compared to its original condition, expressed as a percentage. An SoH of 95 percent, for example, means the battery can still store 95 percent of its original energy. In addition to SoH, the expert checks cell balance. This examines whether the individual battery cells are charged and discharged evenly. Significant voltage differences between cells can indicate emerging defects or uneven aging, which affects the overall performance of the battery.

In addition, the cumulative charge cycles and the ratio between AC charging (alternating current) and DC fast charging (direct current) are read out. Frequent fast charging can accelerate the chemical aging of the cells. The DIAVAG test report documents these values precisely. Through the use of digital multimeters and a visual inspection of the housing components for external damage, a complete picture of the technical condition is created. The process provides the data basis for the subsequent PDF appraisal with full source traceability.

Independence is a valuable asset in the automotive industry. Many battery diagnostics are currently offered by authorized workshops or manufacturers themselves. However, this often involves a structural conflict of interest. A manufacturer who must decide on warranty claims may have an incentive to present the battery condition more optimistically than it actually is. DIAVAG, on the other hand, operates as a fully independent service provider in accordance with ISO/IEC 17020 Type A. This means that DIAVAG neither sells vehicles nor performs repairs nor brokers insurance.

This neutrality is the prerequisite for the legal usability of the appraisals. Whether in a divorce, an inheritance, or an insurance dispute: only an impartial expert can determine a market value that holds up in court or before authorities. DIAVAG's experts are qualified according to the standards of the BVSK (German Federal Association of Independent and Freelance Vehicle Experts). Each appraisal is also finally reviewed and signed by a senior inspector.

This ensures maximum security for the client. While platforms such as wirkaufendeinauto or mobile.de primarily aim for quick purchase or brokerage, DIAVAG delivers a pure condition assessment. The premium appraisal including battery test is offered at a fixed price, ensuring no hidden costs arise. The customer pays for expertise and objectivity, not for a sales pitch. This clear separation of inspection and trade is the core promise of the DIAVAG brand.

The battery is by far the most expensive component in an electric car, often accounting for up to 40 percent of the total vehicle cost. Therefore, the condition of the battery has a massive influence on the replacement value or sale price. A difference of just five percent in State of Health can mean price differences in the four-figure euro range for a high-value vehicle such as a Tesla Model S or a Porsche Taycan. Without a certified battery test, buyers and sellers are left in the dark.

A detailed appraisal serves as a price anchor in negotiations. Sellers can justify a higher price if they can prove in black and white that the battery has been well cared for and has high residual capacity. Buyers, in turn, protect themselves against costly bad purchases. A used EV with a degraded battery can incur high costs shortly after purchase if the range is no longer sufficient for the daily driving profile or if the manufacturer's warranty conditions have already been undercut.

DIAVAG offers a standardized solution here that goes beyond mere estimation. While algorithm-based services only extrapolate value based on age and mileage, the on-site inspection delivers real measured values. In the regions of Hamburg, Berlin, and Munich, the service is available within 24 hours. The PDF appraisal is delivered the same day, so transactions can be completed without delay and with maximum financial transparency.

An appraisal is only as valuable as the standards it is based on. DIAVAG consistently relies on recognized norms to ensure the highest possible acceptance by third parties. The qualification of experts according to BVSK guidelines ensures that the methodological approach corresponds to the current state of the art. Appraisals serve as essential evidence in legal disputes. In such cases, the JVEG (Judicial Remuneration and Compensation Act) often serves as a reference framework for compensating expert services.

Certification as an inspection body according to ISO/IEC 17020 Type A underscores organizational independence. This standard is internationally recognized and defines strict requirements for the impartiality and competence of inspection bodies. For lawyers and notaries, this is a decisive criterion when selecting an appraiser for clients. Whether it concerns the valuation of a home storage system in a real estate transaction or the residual-value determination of a fleet of electric vans, compliance with these standards minimizes the risk that appraisals will be challenged.

In addition, DIAVAG optionally offers to secure the appraisal using a notarial hash on the Polygon blockchain. This creates a tamper-proof digital fingerprint of the document. This allows it to be proven beyond doubt at any time that the appraisal has not been altered since its creation. This technological bridge between classic expert appraisal and modern cryptography offers a level of security that far exceeds conventional paper reports or simple PDF files.

Regulatory requirements for batteries in the European Union are steadily tightening. From February 2027, the EU Battery Passport will become mandatory for all new batteries in electric vehicles and for industrial storage systems with a capacity of 2 kWh or more. This digital documentation is intended to contain information about the origin of raw materials, the carbon footprint, and the current condition of the battery. DIAVAG is already preparing for these requirements today and integrates relevant data points into the inspection workflow.

The battery passport aims to promote the circular economy and create transparency for second-life scenarios. When a battery is no longer powerful enough for use in a vehicle, it can often still serve as a stationary home storage system for years. A precise battery test is the prerequisite for deciding whether a battery can be recycled or put to second-life use. DIAVAG provides the necessary data for this.

Through early adoption of these standards, DIAVAG positions itself as a partner for companies that want to manage their fleets in a future-proof way. Recording SoH values over a vehicle's entire lifecycle enables precise residual-value tracking. Leasing companies and large fleet operators benefit from this, allowing them to better calculate financial risk at the end of the contract term. Data storage is GDPR-compliant on servers within the European Union.

There are various ways to assess the condition of a battery. Mobile on-site inspection by an expert represents the most reliable method. Algorithm-based estimates, as offered by some online portals, only use statistical data. They do not take into account individual usage behavior or the thermal stress the battery has been exposed to. Such estimates are helpful for a rough orientation but insufficient for a legally sound valuation.

Workshop diagnosis usually requires an appointment and bringing the vehicle to the workshop, which involves time and logistics costs. In addition, specialized evaluation tools for detailed cell analysis are often lacking there. DIAVAG combines the depth of technical measurement with the flexibility of a mobile service. The expert comes to the asset's location, whether that's a private garage, a dealer's yard, or a harbor for boats. This saves the customer time while delivering a result at the highest technical level.

For commercial customers, DIAVAG offers scalable solutions that go beyond individual appraisals. Car dealerships increasingly purchasing used electric vehicles need a fast and reliable valuation method to minimize the risk of unsold vehicles with defective batteries. For commercial volumes, DIAVAG offers individual terms and seamless integration into existing dealer management systems (DMS) via API connection.

Fleet operators use regular battery diagnostics to monitor the wear of their vehicles. This enables improved deployment planning. Vehicles with lower SoH can be used on shorter routes, while fit vehicles are reserved for long distances. This active residual-value management protects the company's capital. Standardized documentation also facilitates the later decommissioning of vehicles from the fleet, as a complete condition report is available for each asset.

In addition, DIAVAG sells the hardware case, including the necessary software, to self-employed experts at list price. This allows partners to integrate the high DIAVAG standard into their own portfolio. The software guides the user through the standardized workflow, ensuring that appraisal quality remains consistent nationwide. This is an essential building block for the planned nationwide rollout in 2026.

A unique selling point of DIAVAG is its coverage of seven different asset classes. While classic testing organizations such as TÜV or DEKRA focus primarily on passenger cars, DIAVAG also assesses boats, construction and agricultural machinery, cargo bikes, e-scooters, and home storage systems. Battery diagnostics play a growing role in all these areas. In an electrically powered boat or a construction machine, the battery is an even more critical component than in a passenger car, as the stress profiles are often more extreme.

Especially in the field of home storage systems for photovoltaic installations, there is a great need for independent appraisals. In real estate transactions, the value of the installed technology must be precisely determined. A home storage system that already shows strong degradation after five years reduces the value of the overall system. DIAVAG uses the Premium Battery Test here to provide clarity for owners and buyers. Even in warranty disputes with storage system manufacturers, the independent appraisal serves as an objective basis for negotiation.

Mobile availability is a decisive factor here. A home storage system cannot be transported for inspection. The expert must come to the object. The same applies to boats in the harbor or construction machinery at the job site. Through the standardized use of OBD2 scanners and digital multimeters, DIAVAG can deliver consistently high appraisal quality across all these classes. DIAVAG thus acts as a universal point of contact for technical valuation reports in the age of electrification.