How to Read Battery Health When Buying a Used EV?

Battery Technology
Creation: 19 October 2026

If the SoH value is clearly above the 70 percent warranty threshold, the heart of the used electric car is still young.

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The battery health of a used electric car is measured by the SoH (State of Health) value, which shows the percentage of energy the battery can still hold compared to its capacity when new. You can read this value from the vehicle's own menu, with an OBD scanner, or through a dealer diagnostic; as a rule of thumb, values clearly above the 70% threshold that the warranty references are considered healthy.

Key Takeaways

Most manufacturers warranty the EV battery to 8 years / 160,000 km for at least 70% capacity retention.
An analysis based on data from more than 22,700 vehicles puts the average battery loss at 2.3% per year .
A five-year-old EV retains an average of 95% of its range.
For LFP batteries, charging to 100% once a month is recommended; for NMC, the ideal is to stay within the 20-80% range.
Third-party OBD tools vary in their SoH readings from vehicle to vehicle; the result is an indicator, not a definitive assessment.

What Exactly Does the SoH Value Measure?

State of Health is the ratio between the battery's usable capacity on the day it left the factory and its usable capacity today. It is expressed as a percentage: A pack reading 92% SoH means it can still store 92% of its energy when new. The higher the value, the healthier the battery and the closer the vehicle's real range is to the manufacturer's figures.

Range loss and capacity loss are exactly the same thing: as capacity drops, the distance the car can travel on a single charge decreases proportionally. This is why SoH is the most important technical variable affecting price in the used car market; it determines the purchase decision just as much as the condition of a mechanical assembly like the engine or transmission.

There is one point to be aware of here: a standardized battery health reporting method has not yet emerged in the market. Different manufacturers and vehicles may calculate SoH in different ways, which fuels the trust problem especially in used car sales. Knowing under which conditions and by which definition the value you read was calculated is as important as the number itself.

How to Read Battery Health From Inside the Vehicle?

Tesla Model Y'nin Service menüsünde batarya sağlığını doğrudan gösteren ekran, ikinci el alımın en dürüst sörveyörüdür.

The most reliable way is what the vehicle's own system tells you. Some manufacturers put this information directly on the screen: for example, in a Tesla Model Ythe Controls > Service > Battery Health menu shows the battery's energy retention assessment on screen. Similar screen-based displays may be found under different menu names in other brands.

If your vehicle does not have such a menu, indirect methods come into play. In the new generation Nissan Leafmodels, NissanConnect EV the app allows you to remotely track charge level, range, and battery health. A practical capacity estimate can also be made from the range: comparing the range shown at full charge with the vehicle's official range gives a rough but useful ratio. Another community method is to calculate the total remaining capacity by dividing the distance entered by the vehicle's efficiency value and the battery percentage used; such calculations produce approximate values and are not certified measurements.

How to Approach the Figure Given by the Seller?

Verifying the SoH value stated by the seller comes down to checking it independently, via the vehicle's screen or your own measurement. If possible, have a reading done at an authorized dealer or a service that performs EV diagnostics before buying the vehicle; many dealers offer this service and some platforms issue an SoH certificate. The certificate is used to officially document how much of the original capacity is still usable.

Reading SoH via OBD: How Is It Done in Practice?

The second method is to use an adapter plugged into the vehicle's OBD II port along with a mobile app. The port is on the driver's side, at the lower left of the console, in left-hand drive vehicles. After plugging in the adapter, Car Scanner, LeafSpy or Scan My Tesla type apps transfer battery data to your phone, including cell-by-cell voltages, charging history, and SoH. These apps use parameter IDs called manufacturer-specific PIDs to access battery data.

However, engineering honesty requires drawing a line here: OBD-based third-party tools may not work on every vehicle. Some EV owners report that their scanners never read the SoH of the high-voltage battery at all; compatibility varies from model to model. For this reason, third-party results should be treated as an indicator, not a definitive assessment . Rather than turning the SoH figure you read in an app into a bargaining chip on its own, cross-check it against the vehicle's range behavior and, if available, a dealer diagnosis.

The ecosystem is evolving rapidly: in 2026, diagnostic software developers and app developers are adding EV battery diagnostics to their standard packages; some service chains offer SoH testing for free, while some apps analyze vehicle data to produce real-world range and battery health estimates. Battery health analyses that bring together more than 58,000 used EV listings and OEM and dealer diagnostic reports have also begun to be published.

Where Is the Line Between Good SoH and Bad SoH?

The clearest reference drawing that line is the warranty. The vast majority of manufacturers warrant the EV battery to retain at least 8 years / approximately 160,000 km of at least 70% of its original capacity; at some brands this period falls in the 8-10 year band. Excessive degradation is also technically defined by exactly this threshold: dropping below 70% of the original capacity. The replacement threshold varies by manufacturer and moves in the 70-75% range.

This threshold guides the used-car buyer in two ways. First, if the vehicle is still under warranty and the SoH has dropped below 70%, the battery can be evaluated under warranty; confirm whether the warranty is also valid for the second owner before purchasing. Second, for a vehicle out of warranty, an SoH below 70% means the range has lost roughly a third of the manufacturer's figures, which is usually grounds for serious negotiation or walking away.

Indicator	Comment
SoH of 90% and above	A young or well-preserved pack; range loss is barely noticeable
SoH of 80-90%	Normal aging; real range drops noticeably but remains acceptable
SoH of 70-80%	Careful evaluation needed; warranty period and remaining lifespan should be questioned
Below 70%	Below the manufacturer's threshold; warranty coverage and replacement cost must definitely be investigated

How realistic are the numbers? A large-scale analysis examining data from more than 22,700 vehicles puts average degradation at 2.3% per year and identifies high-power DC fast charging as the biggest risk factor. After roughly 25,000 miles, batteries typically lose 3-5% of their capacity, and after 100,000 miles, 85-90% of the original capacity is retained. An average EV retains 97% of its range after three years and 95% after five years. With NMC chemistry, the curve drops noticeably in the first year, then annual loss settles into the 1-1.5% band. In short, the battery of a good used EV ages far more slowly than most buyers fear. For vehicles that will be parked for long periods, small monthly charge losses are normal; a charge level of around 50% is recommended during storage.

LFP or NMC: How Does Battery Chemistry Change Your Interpretation?

Today, the majority of EVs on the road use one of two lithium-ion chemistries: LFP and NMC. Both speak the same SoH language, but their aging characteristics differ, and this difference requires the used-car buyer to view the same figure differently.

LFP stands out in terms of lifespan and safety: it generally offers superior cycle life and is more resistant to thermal runaway events. NMC, thanks to its higher energy density, fits the same capacity into a lighter and more compact pack; due to its nickel-cobalt content, its recycling value is also higher. In return, LFP is bulkier and heavier for the same capacity, and its cold-weather performance is the chemistry's weak point.

Practical conclusions for the buyer come down to two points. Charging habit: the LFP battery is recommended to be charged to 100% regularly - roughly once a month - while in NMC the 20-80% range is preferred. In other words, in an LFP vehicle, a habit of charging to 100% as seen on the gauge is a healthy sign, not neglect. Usage profile: current comparisons see LFP as better suited to short-distance, budget-focused use, and NMC to high-mileage use. When long-term durability is the priority, LFP is generally considered advantageous and offers a lifespan similar to or better than NMC. Also remember that different trims of the same model may use different chemistry; before purchasing, confirm which pack the specific vehicle you are looking at comes with.

Cold Weather Reduces Range but Does Not Age the Battery

A common mistake in used-car inspection is to assume that reduced range in cold weather means degradation. Cold does not directly affect the battery's lifespan; it only creates a temporary drop in range. If the test day is in winter and the vehicle's range is lower than expected, that alone is not proof of a bad battery. That said, remember that LFP has a weak point in the cold: in an LFP vehicle, winter performance loss can be more noticeable compared to NMC. For a fair comparison, evaluate the vehicle at similar temperatures and a similar charge level.

A Practical Checklist for Battery Checks on a Used EV

If the vehicle has a battery health screen in its own menu, read it from there; this is the primary source.
If there is no menu, check cell data with a compatible OBD adapter and an EV-supported app; evaluate the result as an indicator.
Compare the range shown at a full charge with the manufacturer's value; it is a rough but quick capacity test.
Confirm the warranty period and mileage limit, along with whether the warranty covers a second owner.
If possible, get a dealer diagnosis or an independent SoH report; do not accept the seller's figure on its own.
Find out the vehicle's battery chemistry (LFP/NMC); interpret charging habits and winter behavior accordingly.

Conclusion: Read the Number, but Also Ask How It Was Read

The formula for evaluating a used EV's battery consists of three steps: read the SoH value from the vehicle's own system or a reliable diagnosis, compare it with the 70-75% threshold referenced by the warranty, and interpret it according to the chemistry. An average annual loss of 2.3% and 95% range retention after five years show that the vast majority of healthy vehicles on the market are not a cause for concern. True professional rigor lies in asking about the measurement method and context of the number you read: since standardized reporting does not yet exist, the reliability of the value is as much a part of the negotiation as the value itself.