What's a Good Battery Health Percentage on a Used EV?

If you are shopping for a used electric car, one number tends to loom over every decision: the battery health percentage. It feels like the EV equivalent of a mileage reading, a single figure that tells you how much life is left. So the obvious question is, what counts as good?

The honest answer is that a number on its own tells you very little. A "good" percentage depends on the car's age, its mileage, and how the figure was measured in the first place. This guide gives you a practical way to judge a battery health reading, so you can walk into a viewing knowing whether the number in front of you is reassuring or a reason to pause.

What battery health percentage actually means

Battery health is usually expressed as State of Health, or SoH. It describes how much of the battery's original usable capacity remains. A car at 90% SoH can store roughly 90% of the energy it could when it left the factory, which broadly translates to about 90% of its original range.

So a healthy battery holds more charge, goes further, and behaves closer to a new car. A degraded one holds less, needs charging more often, and may feel noticeably weaker on longer trips.

The catch is that SoH is not measured or reported the same way everywhere. Two cars showing "92%" can have been assessed by completely different methods, which is why the number needs context before you trust it. We cover the technical side of this in State of Health explained, and why not all SoH readings are equal.

How EV batteries actually degrade

To judge whether a figure is good, it helps to know the normal shape of battery ageing.

Degradation is usually front-loaded. Most EVs lose a small chunk of capacity in the first year or so, often a few percent, as the battery settles. After that initial dip, the decline slows down and becomes much more gradual, following a roughly linear line over the following years.

Aggregated fleet data from telematics firm Geotab has shown average annual degradation in the low single digits per year across large numbers of vehicles. That figure is a fleet average across many makes and models, not a promise for any specific car. Your individual vehicle could be better or worse depending on how it was driven, charged, and stored.

The practical takeaway is this: a slightly lower percentage on an older, higher-mileage car is completely normal. The same percentage on a nearly new car with low miles would be a warning sign.

Why a number without context is misleading

Here is where buyers go wrong. They fixate on the percentage and ignore everything around it.

Consider two cars both reading 88% SoH:

• A five-year-old car with 60,000 miles at 88% is ageing exactly as you would expect. That is a normal, healthy result.
• A two-year-old car with 12,000 miles at 88% has degraded faster than it should. Something in its history, perhaps heavy rapid charging or hard use, has taken a toll.

Same number, very different stories. This is why you should never accept a battery health figure in isolation. Always weigh it against the car's age and mileage, and ask whether the level of wear matches the level of use.

A simple framework for judging a figure

You do not need a rigid table of pass or fail thresholds, and anyone who gives you one is oversimplifying. Instead, work through these questions:

1. Does the wear match the age and mileage?

A gentle decline that tracks the car's years and miles is the reassuring pattern. A steep drop on a young, low-mileage car is the thing to investigate.

2. Is there enough range left for how you drive?

A percentage only matters relative to your needs. If a car started with a long range and sits at 85%, it may still comfortably cover your daily driving with room to spare. If it started with a modest range and has dropped, the same percentage could leave you short. Think in real-world miles, not just percentages.

3. Is the figure past the early dip?

If the car is a few years old, the front-loaded first-year loss is already behind it, and the number you are looking at should be relatively stable from here. A very new car may still be settling.

4. Where did the number come from?

This is the one most buyers skip, and it matters more than any of the others.

Why an independent reading beats the dashboard

Many sellers will quote a percentage taken from the car's own dashboard or a phone app. Treat those figures with caution.

A manufacturer's on-board estimate is calculated by the car's own software using proprietary methods that vary between brands. It can be optimistic, it can lag behind the battery's real condition, and crucially it is not directly comparable between different makes. An 88% shown on one brand's dashboard is not necessarily the same as 88% on another.

There is also the simple matter of trust. A number the seller reads off the screen is a claim, not evidence. It has not been verified by anyone independent, and it does not come with anything you can rely on later if the battery turns out to be worse than described.

An independent, TÜV Certified battery test removes those doubts. It measures the battery directly at cell level rather than relying on the car's own estimate, produces a figure that is comparable across brands, and gives you a certificate you can keep. That is the difference between hearing a number and actually knowing it. We explain why independence matters so much on our why an independent test matters page.

Why SoH is becoming the number that counts

For petrol and diesel cars, mileage has always been the shorthand for condition. For EVs, battery health is taking that role. Two identical cars with the same mileage can have very different batteries, which is why SoH is quietly becoming the most important figure in a used EV's history. We explore that shift in SoH is the new mileage for used EVs.

Buyer expectations are moving the same way. In the Startline Motor Finance Used Car Tracker from August 2025, 88% of used EV buyers said they wanted an independent battery health assessment before buying. A verified percentage is fast becoming something buyers expect to see, not a nice-to-have.

The bottom line

A good battery health percentage is not a single magic number. It is one that makes sense for the car's age and mileage, leaves you enough real-world range for how you actually drive, and, above all, has been measured independently rather than read off a dashboard.

Judge the figure in context, ask where it came from, and do not let a healthy-looking percentage distract you from the question of who verified it.

If you want a battery health figure you can genuinely rely on, a £100 independent, TÜV Certified test gives you a verified State of Health reading and a certificate to keep, so you know exactly what you are buying before you commit.