The most important number about a used electric car has often required an on-site diagnostic: the car on a ramp, a technician and a cable. So it got measured on some cars and estimated on the rest. Good2Know now uses the VIN to retrieve the latest available recorded Battery State of Health, together with the date of the reading, for Volkswagen Group and Tesla vehicles.
What State of Health is
Every electric car's battery holds a little less charge over time than the day it left the factory. State of Health, SoH, describes a battery's condition compared with its initial state. It is commonly expressed as a percentage, although calculation methods can vary by manufacturer. A 90% reading generally indicates reduced usable energy capacity, but it does not guarantee exactly 10% less real-world range, which also depends on temperature, driving style, software and other factors.
Few other facts about a used EV carry as much of the price. The battery is the single most expensive component in the car, and its condition does not show on the odometer, the service book or the inspection certificate. Two cars of the same model and mileage can return noticeably different readings, and getting one has often required an on-site diagnostic.
Why it has been hard to get
An on-site diagnostic can provide a current reading, and it is also slow, local and costly. The car has to be present. Someone has to plug in a tool, run the diagnostic and record the result. That works for the one car a buyer is about to sign for. It does not work for a trade-in that arrives on a transporter, a fleet coming off lease in another country, or a forecourt of forty electric cars that all need a price today.
So the measurement gets done where it is cheap enough to justify, and elsewhere the battery is priced on assumption. Often the buyer's most cautious assumption, because the seller cannot show otherwise.
What changes now
Good2Know uses the VIN to retrieve the latest available recorded Battery State of Health, together with the date of the reading. No appointment, no cable, no owner login, and the car does not have to be anywhere near you. The value arrives alongside the rest of the vehicle's lifecycle data, through the same API and the same portal, and the date tells you how current it is.
That changes three things.
- Stock can be priced on a recorded battery value, not on the buyer's most cautious assumption. A car at 96% and a car at 84% stop looking like the same car.
- Buyers get an answer to the question they ask first. "How is the battery?" becomes a dated, source-attributed figure instead of a shrug or a promise.
- It can run on every eligible car on the forecourt, not just the ones worth paying a technician to test. The lookup can become part of the existing vehicle check at acquisition.
What it means for dealers, marketplaces, insurers, and finance providers
For a dealer, the value lands at acquisition. A trade-in offer or an auction bid on an electric car can take the recorded battery value into account before the car has moved. The same figure and date can then follow the car to the listing and the handover, so the customer sees what the dealer saw.
For a marketplace, it adds a dated, source-attributed battery value to the listing instead of relying solely on the seller's estimate.
For insurers and finance providers, it is an additional residual-value input. A leasing portfolio can be reviewed against recorded battery condition alongside age and mileage, and an end-of-contract return can be discussed on a reading rather than an argument.
Regulation is moving the same way. Since 18 August 2024, the EU Batteries Regulation has required the battery management system of an electric vehicle to contain current data for determining the battery's state of health and expected lifetime, with access rights defined for the legal purchaser and authorised parties for specified purposes. From 18 February 2027, EV batteries placed on the market or put into service must carry a digital battery passport. That applies from that date onward; it is not a retroactive requirement for every EV already on the road (EU Batteries Regulation, European Commission guidance). The direction is fixed: battery condition is becoming a documented, transferable fact about the car. The practical question for the trade is who can read it today, for the cars already on the road.
Coverage
Volkswagen Group and Tesla today.
- Volkswagen: ID.3, ID.4, ID.5, ID.7, ID.7 Tourer and ID. Buzz
- Škoda: Enyaq, Enyaq Coupé and Elroq
- Cupra: Born and Tavascan
- Audi: Q4 e-tron
- Tesla: vehicles from 2019 onward
More manufacturers are being added. Coverage is gated by brand and model before any request is made, so a lookup on a vehicle outside the list returns a clear "not covered" rather than a guess.
The data view
State of Health is a good example of what Good2Know is for. On its own it is one number from one source. Next to the rest of the vehicle's record it becomes a decision. As an illustrative example, a 2022 ID.4 with a recent 91% reading, a clean damage history and complete service records is a different purchase from the same car at 91% with a gap in the service book and a recorded damage claim. The value is not in displaying the number. It is in reading it alongside everything else about the vehicle, inside the workflow that already exists, so the decision gets faster and cleaner.
Available now
Battery State of Health is live for Good2Know customers on the portal and the API. If you already work with us, ask us to switch it on for your account. If you do not yet, book a demo or write to [email protected].
What we're watching next
- Manufacturer coverage: which brands open up battery data next, and how consistent the readings are across them.
- Pricing behaviour: how quickly used-EV prices start to separate by State of Health once the number is visible at acquisition.
- Battery passport, February 2027: how the passport format for batteries placed on the market from that date aligns with what manufacturers already expose for cars on the road today.
- Listings: which marketplaces are first to show a dated State of Health on the listing itself.