What does SOH mean for an electric car?
A single percentage that carries half the value of the car. Below, you can read what this number tells you, what it does not, and why it matters who determined it.
SOH in one sentence, and what it is not
State of health expresses how much energy the battery pack can still store today, compared to the amount it started with when it rolled off the assembly line. One hundred percent is brand new, ninety percent means that a tenth of the capacity has disappeared.
What people mistakenly read into it is a judgment about the car as a whole. A battery pack at ninety-two percent can be perfectly balanced and last for years, while a pack at that same percentage with misaligned cells tells a completely different story. The figure is a summary, not a diagnosis.
Equally important: SOH is not the same as the state of charge that you see on the dashboard. That shows how full the battery currently is. SOH indicates how much capacity the battery still has.
Calculate for yourself what a percentage means
Choose a model and slide to a SOH value. The capacity and range come from the manufacturer's specifications that we record during our own measurements.
Gezond. Normale slijtage voor een auto die een paar jaar meedraait.
The range is the WLTP figure recalculated proportionally. You will achieve less than this in winter, and sometimes more on a quiet summer drive.
Why independence carries more weight here than elsewhere
With most car parts, you can diagnose something yourself. You hear a bearing, you see rust, you feel a clutch slipping. With a battery pack, you can't do anything. You are completely dependent on what the system says and who is reading that system.
That is why there is an issue with a measurement carried out by the party selling the car. Not because that party is necessarily unreliable, but because the buyer has no way of verifying it. We are not involved in any transaction: we do not sell cars and have no interest in the outcome.
What we measure, we publish unfiltered. Even if it is bad news for the person who commissioned it.
— THE RESULT
From measured value to something someone can build on
A percentage on a screen is not yet proof. It only becomes usable when it is linked to a vehicle, recorded at a specific moment, and established according to a verified method.
That is the difference between reading data and certifying it. Anyone with the right equipment can do the former, but the latter requires a standard that a third party commits to.
SOH certification: where the standard comes from
SOH certification means that a measurement is carried out according to an established method, and that a third party has verified that method. Without such a verification, any report is nothing more than the opinion of the person who drafted it.
Our method is CARA Approved. CARA tests whether a measurement method is reproducible: does another party with the same car get the same answer? That is the core of certification, and at the same time the point where stand-alone diagnostic software usually falls short.
For you as a buyer or seller, that means one thing: the number on the report is not ours, it belongs to the car. We have only made it visible.
Frequently asked questions about SOH
What exactly does the SOH value mean?
The ratio between the current capacity of the package and its capacity upon delivery, expressed as a percentage.
Why not just the dealer's test?
Because the selling party has an interest in the outcome. An independent measurement can be verified by both sides of the transaction.
What is a CARA-approved battery test?
A measurement method tested for reproducibility by CARA, the European standard for battery diagnostics.
Can I read the SOH myself?
With professional equipment, yes. Universal dongles cannot bypass the manufacturer's security.
Want to know more? View all frequently asked questions in the knowledge base.
Have it independently determined
Within three minutes you will know where the package is, with a report that a buyer or seller can read.