Is a SoH of 90 percent good or bad?

It depends on age and mileage. After one year that figure would look worryingly low; after six years and 120,000 km it is solid. What matters is the trend: a battery sitting steadily at 90 percent is a different thing from one that is dropping quickly.

Why do two measurements show different SoH values?

Because SoH is not a standardised metric with a single procedure. Depending on the method, temperature, state of charge and reference basis (catalogue value or the actual as-new capacity), results can differ by several percentage points. Reputable figures therefore give a range rather than a decimal place.

Can I read SoH off the range display?

Only very roughly. The display rests on the battery management system's estimate, which drifts without calibration, especially with [LFP batteries](/en/glossary#lfp), which are rarely run fully up and down. A low displayed figure can simply mean an uncalibrated BMS.

Battery Basics

Battery SoH explained: what the figure means for a used EV

Updated: 21 September 2026 · 4 min read

Anyone buying or selling a used EV soon runs into three letters: SoH, the State of Health. The figure appears in the listing, in the test report and in the negotiation. It is useful, and it comes with fine print. This guide explains both, without asking you to learn battery engineering.

What the SoH figure means

SoH describes how much usable capacity a battery still has compared with its as-new state. 90% SoH on a battery that started with 75 kWh net means around 67.5 kWh are available today. The figure falls over the battery's life, through age and through charge cycles. That is normal, not a defect.

What is a good SoH value?

It depends on age and mileage. As rules of thumb, with due caution about the false precision of a single number:

Above 95% is typical for young vehicles in their first two or three years.
90 to 95% is unremarkable for most used cars of middling age.
85 to 90% is normal at six-figure mileages: fleet analyses show around 87% on average after 300,000 km (more in our guide to EV battery lifespan).
Below 80% calls for context: how old, how driven, and is that a single measurement or a confirmed trend?

Then there is the direction. In the first year or two, capacity drops noticeably, often into the range of 93 to 97%, after which the curve flattens markedly. A three-year-old car at 94% is therefore the normal case, not a warning sign. A stable 89 tells a different story from a 92 that is falling fast. You can only see that with a history.

SoH is not range

Range also depends on consumption, weather, driving profile and software. A healthy battery can show little range in winter, an aged one plenty in summer. To judge battery condition you need capacity data. The range readout on the dashboard is no substitute.

Why two measurements show different values

SoH is not a standardised metric with a single procedure. The method, the temperature, the state of charge during measurement and the reference basis all shift the result. Many displayed values are also the vehicle's own estimate, which drifts without calibration, especially with LFP batteries. Two measurements on the same car can therefore sit several percentage points apart without anything about the battery having changed.

For you, that means a single figure with a decimal place is more precise than it can be. A dependable figure gives a range and says how it was arrived at. What shifts the number in detail is set out in the technical background just below.

For the technically minded

Technical background (optional)

Reference basis, measuring method, conditions and the vehicle's own estimate: what shifts a SoH figure, and what the warranty and Euro 7 lay down. You do not need this section to buy or sell.

Four things sit behind every SoH figure, and all four can shift the result.

The reference basis. Gross or net capacity? Catalogue value, or what the vehicle actually held when new? Manufacturers also build in buffers, some of which have been changed by software. The choice of reference alone shifts the percentage.

The measuring method. A full discharge cycle measures differently from a 3-minute pulse test, and both measure differently from the running estimate of the battery management system. Without a stated method, a SoH value is hard to place.

The state during measurement. Temperature and state of charge affect the result. The same battery can perform differently on a cold morning than after a motorway run.

The BMS itself. Many "SoH values" are not a measurement but the vehicle's self-assessment, and that drifts when it has not been calibrated for a long time. LFP batteries with their flat voltage curve are especially prone to this; that is why manufacturers recommend regular full charges for them.

The 70% threshold. Like most manufacturers, Tesla warrants the battery for eight years (depending on the variant, 160,000 to 240,000 km) to at least 70% capacity. The EU is following suit: Euro 7 anchors, for the first time, regulated minimum durability for the traction batteries of new vehicle types. SoH thus moves from a community number to a regulated metric.

A history over months softens these influences: jumps, BMS drift and measurement errors average out, and outliers stand out. That is what Akkubrief builds on, with a range and stated uncertainty rather than a falsely precise decimal place. How that works is set out openly in our methodology.

What you can do with the figure

If you are buying: ask for the figure, for the measuring method, and for how long it has been in this range. The last question costs nothing and separates listings with substance from listings with a number. Which testing routes exist and what they cost is covered in our comparison of ways to check a Tesla battery.

If you are selling: a good figure reassures, a stable history convinces. Akkubrief builds that history in everyday use: for supported vehicles you connect the car once with read-only access, and from then on the same quantity is determined again and again from real charging sessions, as a range with stated uncertainty. What a battery history built this way shows beyond a single figure, and why it cannot be caught up on later, is covered in its own guide.