Technical FAQ

Correct — not every battery gives an exact SoH value, but every battery provides some version of the remaining battery capacity (GM, for example, has no single parameter that states SoH outright, but instead provides the battery capacity in Ah).

Every battery management system (BMS) already runs its own long-term SoH estimate based on cycle count, temperatures, and usage history. The factory BMS value is our gold standard: the OEM has been collecting data over the entire life of the battery, while a diagnostic tool reads for roughly two minutes. We surface and normalize that OEM measurement.

We emulate the OEM factory diagnostic tools to read the same BMS data a service department would see — the equivalent of the GM factory tool for GM, FDRS for Ford, Techstream for Toyota, Xentry for Mercedes, and so on. We pull the BMS data and report it purely for state of health.

Manufacturers report capacity in different ways, and we normalize all of them so every VoltScore report reads the same way:

• Hyundai / Kia report SoH directly as a percentage (simplest).
• Tesla and most others report kilowatt-hours (the capacity number).
• GM (on some cars) reports amp-hours, not temperature-adjusted — we convert (amp-hours × voltage) and apply temperature correction to reach an equivalent capacity number.

Battery capacity reads differently at different battery temperatures. Most OEMs (including Tesla) already adjust for this. BMW is the notable exception — it reports capacity at the battery's current temperature, so we apply a standard, research-backed formula to normalize it. GM amp-hour readings also require temperature adjustment, which we perform.

Batteries have a larger gross capacity and a smaller usable capacity. The smaller usable capacity is what is used for range. The larger gross capacity is used by a BMS to maintain a buffer at the top and bottom of the battery, so you never truly hit 100% or 0% SOC, since both extremes can be damaging to the battery itself. Over time, the BMS can release more of the gross capacity into usable capacity, which slows down the perception of range loss. For a BMS, it is a balance between longevity and range.

Since range is the ultimate key value for drivers, we focus on measuring the usable capacity of the battery. Some OEMs offer large buffers, which allows the usable capacity to stay close to 100% for up to several years. Others have a much smaller buffer, and a driver will notice the range drop off by 5–10% in the first year. Our goal is to provide a SoH value that reflects this impact on range. This is also the same approach specified by CARA, the European certification body of battery health devices. On the report, click on the info icon next to the score for a full explanation.

VoltScore's core technology is CARA-certified. CARA is the European remarketing organization that tests battery health devices: it takes the top ~70 models sold in Europe (many of which are also sold in the US and Canada, with overlap growing) and compares the SoH from the OEM factory tool against the SoH from each tested tool.

To pass, our reading must be within 1% of the OEM value — and the certification is renewed every year.

Yes. A plug-in device (dongle) paired with an iOS/Android app. Here's the workflow:

• Launch the app and log in using Face ID or biometrics.
• Select the vehicle you're plugging into.
• Plug in — the device reads the data.
• The app prompts you to unplug the device (so devices don't get lost).
• Select the battery size (not always auto-detectable).
• The report is emailed to you.

It's designed as a two-minute, plug-and-play test.

Teslas don't have functional OBD ports, so they need an adapter cable — and the correct cable varies by model. When you select the Tesla model in the app, it tells you which cable to use (red, blue, or green). If you don't plug in within 10 seconds, the app shows a how-to video. The first time you test each Tesla model, figuring out where to plug the adapter cable will likely take between 2–5 minutes; after that, roughly 30 seconds.

It isn't tied to a single user or device. One main account holds the subscription, and you can add multiple user accounts (common in multi-device shops). The main account sees all reports; each sub-user sees only their own. A single device can be used by multiple accounts.

It layers cleanly into a used-vehicle inspection / reconditioning process. Instead of a qualified tech running factory tools and doing manual calculations, anyone from a porter up can run a two-minute test. It's especially valuable for off-brand EVs, where a store won't have the factory tools — and it gives the sales team a credible, standardized report to put buyers at ease.