Voltified Energy conducted its own audit of 100 public advertisements for used battery-electric passenger cars. In the sample, 19 advertisements stated SOH, 7 identified a test method or provider, 2 included the test date, and none provided, within the advertisement or through a linked page, a battery report that buyers could open and verify independently.
This is not another opinion about electric mobility. It is the result of analysing publicly available information that someone considering a used electric car actually received on the date of the study.
The study’s key findings at a glance
The audit was carried out on 22 August 2026 and covered 100 unique, active advertisements for used battery-electric passenger cars (BEVs) across 15 model groups.
The main finding: none of the 100 audited advertisements allowed buyers to open and verify a battery-condition report independently.
This result does not mean the cars examined had bad batteries. It shows something different: at the point of decision, buyers usually did not receive complete, verifiable evidence of the condition of one of an electric vehicle’s most important and expensive components.
We measure paint thickness and check the VIN, yet still buy the battery on someone’s word
Before buying a used car, drivers check its damage history, VIN, mileage, service records and paint thickness on individual body panels. This is natural: each piece of information can affect safety, maintenance costs and vehicle value.
For an electric car, the traction battery joins that list. Its condition affects usable capacity, real-world range, charging behaviour, future costs and the car’s residual value, among other things. Yet a battery cannot be reliably assessed from photographs, age, mileage or a short test drive.
Advertisements often feature detailed equipment lists, service history and dozens of photographs. Battery information, meanwhile, may be limited to nominal capacity, the published range or a single SOH figure without a date, method or source document.
This information asymmetry was the starting point for Voltified Energy’s original study.
How did we audit 100 advertisements for used electric cars?
The study was an exploratory audit of battery-information transparency. Its purpose was not to assess individual cars technically or rank brands. We examined only what battery information was publicly available to buyers.
Study methodology
The audit concerns a specific, purposively selected sample of 100 offers. It is neither a random survey of all OTOMOTO advertisements nor a statistical estimate of Poland’s entire used-electric-car market. It does, however, identify a measurable information gap and support hypotheses for further research.
Sample composition: 15 model groups
What do sellers disclose about the battery, and what is usually missing?
Basic vehicle specifications were the most commonly published information. Battery capacity appeared in 76 advertisements, and a claimed range in 53. These data help describe the vehicle variant, but are not the result of testing the battery’s current condition.
Information about the battery’s actual condition appeared much less often:
19 advertisements stated SOH,
13 mentioned a test or diagnostics,
7 identified a test method or provider,
2 included the test date,
0 provided a report that could be independently verified.
This reveals a clear difference between describing the car and documenting battery health. The market can provide a number, but shows where it came from much less often.
81 out of 100 advertisements did not even state SOH
To classify the level of information, we created a T0–T5 transparency scale. It does not assess the car’s technical condition. It shows only how complete the publicly available information in the advertisement is.
What exactly does the result of 0 reports out of 100 mean?
In none of the advertisements examined did we find a report in the text read or at the linked destination that would allow a buyer to move from a claim to a source document.
A verifiable report should at least make it possible to:
identify the vehicle or battery tested,
check the date of measurement,
identify the method, device or organisation performing the test,
read the result and the scope of parameters checked,
confirm that the document relates to a specific test rather than a general statement by the seller.
The 0/100 result does not prove that sellers had no documentation outside the advertisement. It does show, however, that buyers could not check it independently using the publicly available offer.
This is an important distinction. Our audit assesses information transparency, not sellers’ intentions or the technical condition of the vehicles concerned.
What is battery SOH, and why is the number alone not enough?
SOH, or State of Health, is an indicator describing battery condition relative to an adopted reference point. In simple terms, a value of 90% may suggest that the battery has retained around 90% of the capability defined by that method, compared with its initial condition.
The problem is that not every method determines SOH in the same way. The result may come from a manufacturer’s algorithm stored in the BMS, a capacity test, analysis of operational data or an external diagnostic tool. Different tools may use different data, conditions and reference points.
SOH is therefore useful information, but without context it is not a complete diagnosis or an independent battery certificate.
What does a standalone “SOH 93%” fail to explain?
Without additional data, buyers do not know:
when the reading was taken,
which method or device was used,
whether the result comes directly from the BMS or from an external test,
which parameters beyond SOH were checked,
whether voltage differences between cells or modules were assessed,
whether faults, temperature anomalies or charging problems were detected,
whether the document can be linked to a specific vehicle.
More comprehensive diagnostics — depending on the car model, available data and method used — may cover usable capacity, voltages and section balance, internal resistance, temperatures, stored faults, charging history and battery behaviour under load, among other parameters.
What SOH values appeared in the sample?
In the 19 advertisements stating SOH, the declared values ranged from 82% to 100%, with a median of 93%.
This should not be taken to mean that the average battery on the market has 93% SOH. These data concern only offers whose authors chose to publish the figure. More importantly, most lacked a date, method and report, so the claims had limited comparability.
The problem was not limited to private sellers
The sample contained 76 business advertisements, 21 private advertisements and 3 for which the seller type could not be clearly determined.
15 out of 76 businesses stated SOH, or 19.7%,
4 out of 21 private sellers stated SOH, or 19.0%,
6 businesses and 1 private seller named a method or provider,
both test dates found appeared in business offers,
no seller category provided a verifiable report.
In this sample, seller type explained virtually none of the gap in SOH disclosure itself. The comparison is descriptive and does not assess the entire market or individual seller groups.
The “Battery 4D” standard: four pieces of information that should accompany a used EV
In response to the audit results, we propose a simple information standard called “Battery 4D”. It is intended to help buyers assess the origin of a result and sellers present information in a comparable format.
An example entry in an advertisement could look like this:
BATTERY 4D: SOH 93% • tested 19.08.2026 • method: [method or provider name] • report: [link, QR code or identifier].
“Battery 4D” is a proposed standard for information completeness. Simply filling in the four fields is not an official or accredited certificate and does not guarantee future battery durability. The quality of a conclusion depends on the quality of the test performed and the credibility of the document.
What do the results mean for participants in the used-EV market?
For electric-car buyers
Before buying, ask not only for the SOH value, but also for the date, method, test provider and document. If there is no report, the statement should be treated as one piece of information requiring confirmation, not as a complete diagnosis.
A useful list of questions before purchase:
When was the battery tested?
Who performed the test, and how?
Does the result come only from the BMS or from broader diagnostics?
Which parameters beyond SOH were checked?
Can I receive the report and verify its authenticity?
For sellers, dealers and used-car traders
Documented battery health can reduce buyers’ uncertainty, bring structure to price discussions and distinguish a reliably described offer. The key, however, is to show the source alongside the result.
Companies interested in a repeatable process can explore Voltified’s solutions for diagnostic battery certification for businesses.
For classified-advertising platforms
Four comparable fields — result, date, method and document — could improve the quality of information in EV offers. The platform would not have to assess battery condition itself; it could enable sellers to show the source of their claims. More information about a possible cooperation model is available on the Voltified for sales platforms page.
For banks, leasing companies, insurers and fleets
A lack of comparable battery data increases uncertainty in end-value assessment, risk assessment, portfolio management and repair-versus-replacement decisions. Diagnostics do not remove all risk, but can replace some assumptions with measurable data.
Voltified is developing solutions for battery residual valuation and applications of battery data for insurers.
Why is battery data becoming increasingly important?
The used-EV market is developing alongside European regulations on battery traceability and data. Regulation (EU) 2023/1542 of the European Parliament and of the Council provides that, from 18 February 2027, every electric-vehicle battery placed on the market or put into service within the regulation’s scope will have an electronic record known as a battery passport.
The European Commission indicates that the passport is to include identification and technical characteristics, information about the responsible organisation, performance and durability data, and information supporting repair, reuse and recycling, among other things.
This does not mean that every current used-electric-car advertisement is already required to publish SOH or a full report. The #PokażBaterię campaign proposes a market transparency standard for selling used EVs; it does not replace legislation or extend its applicability.
Official sources:
#PokażBaterię — from claims to evidence
By publishing the results, we are launching the #PokażBaterię campaign. Its goal is to start a substantive discussion about what a used-electric-car advertisement should look like and what information buyers are entitled to expect.
This is not a campaign against electric cars, sellers or classified-advertising platforms. On the contrary, greater transparency can build trust in the used-EV market and make decisions easier for all parties to a transaction.
The campaign’s message is simple:
We measure the paint on every wing. Yet we still too often buy a battery worth tens of thousands of zlotys on someone’s word.
We want to move the market from asking “Is the battery good?” to four specific questions:
Conclusions from Voltified Energy’s original study
The audit of 100 advertisements shows three clear levels of information:
Vehicle specifications are relatively common. Battery capacity appeared in 76% of offers and a claimed range in 53%.
Information about current condition is much less common. SOH appeared in 19% of offers, and a mention of testing or diagnostics in 13%.
The ability to check the source of a result virtually disappeared. A method or provider was identified in 7% of the sample, a date in 2% and a report available for independent verification in 0%.
The most important gap, therefore, is not simply one missing number. It is the absence of a complete information chain: result → date → method → document.
Voltified Energy will continue conducting market research, developing its methodology and publishing further analyses of traction-battery diagnostics, residual value and transparency.
Q&A
Frequently asked questions
Does SOH show an electric-car battery’s actual condition?
SOH is a useful indicator, but its meaning depends on the calculation method, reference point and recency of the measurement. An SOH value alone, without a date, method and document, is not a complete battery diagnosis.
Is a BMS SOH reading enough before buying a used EV?
A BMS reading can be a valuable starting point, but it does not always reveal everything relevant to the buyer. Depending on the vehicle and tool, broader diagnostics may include usable capacity, voltage differences, temperatures, resistance, faults and usage history.
What SOH level is good?
There is no single universal threshold suitable for every model, age, mileage and usage pattern. A result should be interpreted in the context of the test method, the specific battery’s parameters, measurement conditions and the buyer’s needs.
What should an EV battery report include?
The report should identify the vehicle or battery, state the date, method and provider of the test, and present the scope of parameters checked and the result. It should be possible to link the document to a specific test, and it should be available for verification.
Do a battery certificate and SOH mean the same thing?
No. SOH is an indicator. A certificate or report is a document that should describe the result, method, date, scope of testing and vehicle identification. The certificate’s quality depends on the procedure and the credibility of its issuer.
Must a battery report be attached to a used-EV advertisement in Poland?
As of the date of the study, we do not identify a general obligation to attach such a report to every used-electric-car advertisement. “Battery 4D” is a proposed market standard intended to improve transparency in offers.
Does the 0/100 result mean that no seller had a report?
No. It means that neither the text read in the 100 advertisements examined nor the links provided gave buyers a report they could open and verify independently. A seller may have held a document outside the public offer.
Does a study of 100 advertisements describe Poland’s entire EV market?
No. This is an exploratory audit of a purposively selected sample of 100 offers from 15 model groups. The results describe only that sample and should not automatically be generalised to all advertisements in Poland. The study does, however, identify a specific information gap worth measuring further.
About Voltified Energy
Voltified Energy develops solutions for traction-battery diagnostics, certification of results and battery residual valuation using the BHV — Battery Health Value system. We combine technical data, engineering analysis and the needs of the used-EV market to support buyers, sellers, dealers, fleets, leasing companies, banks and insurers.
Would you like to test a battery before buying, document a car’s condition before selling, or discuss introducing a standard for your company or platform?
Contact Voltified Energy and join the campaign #PokażBaterię.
