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 Value Explained: What the State of Health Tells You

Updated: 22 August 2026 · 3 min read

Anyone buying or selling a used EV trips over three letters straight away: SoH, the State of Health. The number sounds objective: 91 percent, done. In truth it is an estimate with fine print. Know the fine print and you negotiate better.

What SoH means

SoH describes how much usable capacity a battery still has compared with its as-new state. 90 percent 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 calendar ageing and through charge cycles.

Why a single number can deceive

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 denominator alone shifts the percentage.

The measurement 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.

SoH is not range

Range also depends on consumption, weather, driving profile and software. A healthy battery can show little range in winter, a degraded one plenty in summer. To judge battery condition you need capacity data — not the range readout on the dashboard.

The typical curve: steep first, then flat

Fleet and community data show a recurring pattern: in the first year or two, capacity drops noticeably (often into the range of 93 to 97 percent), after which the curve flattens markedly. A three-year-old car at 94 percent is therefore not a warning sign but the normal case. It becomes notable when the trend deviates from the pattern — which you only see if you have a trend.

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

Before the threshold comes the direction: a stable 89 tells a different story from a 92 that is falling fast.

The 70 percent 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 percent capacity. And 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 — one more reason to insist on dependable figures when buying used.

Why history proves more than a snapshot

A single measurement says: this is how it was on this day, with this method. A trend over months says: this is how this battery really ages. Jumps, BMS drift and measurement errors average out, outliers stand out. That is what we build on at Akkubrief: calculating battery condition from the charging history across many charging sessions, as a range with stated uncertainty rather than a falsely precise decimal place. How that works is set out openly in our methodology.

A development recorded that way is called a battery history. It has one property that changes how you handle the SoH figure: a test can be caught up on at any time, a history cannot — it has to have come about when it came about. What it shows beyond a single figure is covered in its own guide.