EV Battery Testing
The health of an EV battery is something you’ll want to keep an eye on and test – whether its your own car or you are thinking of buying a new onw. That’s because the high-voltage battery pack is not only responsible for powering the car, but also one of the most expensive components to repair or replace.
Over time, EV batteries naturally lose a bit of capacity. That means slightly fewer miles from a full charge as the years go by – a normal part of battery ageing. But if you’re buying a second-hand EV or noticing a drop in range, it’s helpful to know exactly how the battery is performing.
The good news? Testing an EV’s battery health is easier than you might think. From quick checks you can do on the dashboard to more advanced tools and apps, there are a range of ways to get a clearer picture of how well a battery is holding up. Let’s have a run through your different options:
Understanding EV Battery Health
Before we get into testing options, it’s worth getting clear on what we actually mean by “EV battery health” – and which battery we’re talking about.
Your EV Has Two Batteries!
Every electric car comes with two batteries:
- A 12-volt battery that powers things like the lights, radio, and central locking – just like you’d find in a petrol or diesel car.
- A much larger high-voltage battery (usually lithium-ion) that stores energy to drive the electric motor and move the car.
This guide is all about the second one – the high-voltage battery. It’s the most expensive component in an electric vehicle and the one that directly affects range, performance, and overall value.
What Is Battery Health?
When we talk about battery health, we’re referring to how much usable capacity the battery has left compared to when it was new. In simple terms, it’s a measure of how much energy the battery can still store and supply to the car.
Over time, all EV batteries lose a small amount of capacity due to the everyday use. You might start with a 64kWh battery that, after several years, only holds 58kWh when fully charged. That means fewer miles between charges, even if you’re still charging to 100%.
This is totally normal. Most EV batteries degrade by just 1–2% per year, although this can vary depending on driving habits, charging patterns, climate, and how well the battery has been looked after.
Typical Battery Sizes and What They Mean
Battery size in EVs is measured in kilowatt-hours (kWh), and different types of vehicles come with different capacities:
- Small hatchbacks: ~30–40kWh
- Mid-size crossovers: ~60–70kWh
- Premium/luxury EVs: 90kWh and up
Understanding the original battery size gives you a useful baseline when assessing a used EV. For example, if a car originally had a 62kWh battery and is now reporting only 55kWh usable, you’re looking at around 11% degradation – which might be fine depending on the age and mileage.
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At-Home Battery Testing Options
You don’t need specialist equipment or a trip to the garage to get a good sense of your EV’s battery health. In fact, your car already gives you several clues if you know where to look. Whether you’re an owner keeping an eye on things or taking a second-hand EV for a test drive, these quick checks are a great place to start.
Dashboard Range Estimations
The most obvious indicator is the estimated range your car displays when fully charged. This figure is based on battery capacity, recent driving habits, temperature, and terrain – so it’s not a perfect science. But it’s still a useful tool.
Try this: charge the car to 100%, then reset the trip meter and go for a drive. Compare the estimated range to the actual miles you’re getting. A healthy battery should deliver something close to what’s shown – allowing for conditions like cold weather or heavy use of the heater.
If the range drops sharply, is far lower than expected, or varies wildly from one charge to the next, it might be worth looking into further.
State of Charge (SOC) Monitoring
The State of Charge shows how much energy is left in the battery at any given time – often displayed as a percentage. This figure usually drops at a predictable rate as you drive, so sudden or steep declines can indicate an issue.
On a test drive, keep an eye on how quickly the SOC falls. If you’ve only driven a few miles and it’s already dropped by 10% or more, that could be a red flag. It’s not a definitive diagnosis, but it’s a quick way to spot unusually fast battery depletion.
Battery Management System (BMS) Readings
Many EVs come with a built-in Battery Management System, or BMS, which monitors the condition of the battery and helps prevent damage from overcharging or overheating. Some vehicles will show BMS data on the dashboard or infotainment screen – things like battery temperature, voltage, or health status.
If your car offers this, check for:
- Any warning messages about battery health
- Unusual temperature readings during normal use
- Variations between battery cell voltages (if shown)
While this data can be a little technical, any persistent irregularities could indicate wear or imbalance within the battery pack.
Use Everyday Driving to Spot Clues
Even if you’re not digging into data, driving the car normally can reveal a lot. Try using the heating, air conditioning, or heated seats and see how that affects your available range. These systems all draw power from the main battery and can highlight how the battery performs under load.
It’s also worth comparing your experience with other drivers of the same model – via forums, owner groups or reviews – to get a sense of what’s typical. If your range seems significantly lower than others driving the same car, it might be time to investigate further.
Professional EV Battery Testing
While at-home checks can give you a general idea of how your EV battery is holding up, sometimes you’ll want a deeper, more technical analysis. Whether you’re assessing a second-hand car before buying, or looking for peace of mind as an owner, there are more advanced options available through garages, manufacturers, and dedicated software tools.
Service Centre Diagnostics
For the most accurate picture of battery health, you can take your car to a certified service centre or dealership. Technicians there use specialised diagnostic tools to measure:
- Battery capacity (how much energy it can store)
- Internal resistance (which can indicate cell degradation)
- Charge and discharge rates
- Individual cell performance
These tests can reveal underlying issues that aren’t obvious from range estimates alone – such as a few failing cells that drag down overall performance. You might also receive a battery health report, which is especially useful if you’re planning to sell the car or want documented proof of battery condition for EV insurance or warranty purposes.
The cost of these diagnostics varies, but for EV owners wanting real clarity, it’s often money well spent.
Manufacturer Apps & Software Tools
Many EV manufacturers offer official software tools or smartphone apps that give you insight into your battery’s performance. These are often more advanced than the basic dashboard display and can show:
- Battery degradation over time
- Charging patterns and history
- State of health (SoH) and state of charge (SoC)
- Alerts about battery efficiency or faults
In many cases, these tools connect to the car via Bluetooth or an OBD2 reader, which plugs into a port under the dashboard. Some apps are free, while others may require a subscription or one-off payment.
It’s worth checking what your car’s manufacturer provides. For example:
- Tesla owners can access a wealth of data through the Tesla app and vehicle interface.
- Nissan Leaf drivers often use apps like LeafSpy to dig deeper into battery metrics.
- Brands like BMW, Hyundai, and Kia also provide varying levels of diagnostic support.
These tools can be especially useful for spotting slow or unexpected changes in battery behaviour over time.
Diagnostic Tools for DIY Users
If you’re a hands-on EV owner or someone who likes to dive into the details, there are several diagnostic tools available that go beyond basic dashboard checks – without the need for a trip to the dealership. These tools range in complexity and cost, but many are perfectly accessible for everyday drivers.
OBD2 Readers & Scanners
Most modern vehicles – electric or otherwise – are fitted with an OBD2 (On-Board Diagnostics) port, which allows you to plug in a reader or scanner to access live data from the car’s internal systems.
When paired with the right app, an OBD2 reader can give you a detailed look at your EV’s battery performance, including:
- Remaining battery capacity (in kWh or %)
- Battery degradation over time
- Voltage levels of individual cells
- Charging and discharging behaviour
- Diagnostic Trouble Codes (DTCs) that point to faults
Basic OBD2 readers can cost as little as £15–£30, while more advanced Bluetooth-enabled scanners come in around £50–£150. Just make sure the app you want to use is compatible with your vehicle model before buying.
Multimeters
For those with some electrical know-how, a digital multimeter can be used to test the battery’s voltage, resistance, and current. This is more common in workshop environments or by owners who like to tinker with the technical side of EVs.
A multimeter can help confirm whether the battery is delivering consistent voltage and whether there’s any unusual resistance that could indicate damage or deterioration. That said, you’ll need to be confident working with high-voltage systems – EV batteries can be dangerous if handled incorrectly, so this isn’t a recommended route for casual users.
Multimeters suitable for EV diagnostics can cost anywhere from £100–£300+, depending on the features and accuracy required.
Specialist Battery Testers
There are also dedicated battery testing devices available – tools designed specifically for high-voltage EV battery packs. These can assess:
- State of charge
- Voltage across modules
- Internal resistance
- Temperature consistency
- General battery health and potential failure points
While highly effective, these tools are usually aimed at professional garages, EV enthusiasts, or fleet operators. Prices tend to run into the hundreds of pounds, making them overkill for the average driver – but if you maintain multiple EVs or want a deeper level of insight, they might be worth considering.
Third-Party Battery Health Apps
A growing number of third-party services and apps aim to make battery testing easier and more objective. These typically work by gathering driving data via a smartphone, telematics device, or OBD2 reader, and using AI to evaluate the battery’s true performance.
Apps like ClearWatt or Recurrent (US-based but expanding) measure the real-world efficiency of your vehicle over several sample journeys, taking into account factors like:
- Environmental conditions
- Driving style
- Charging behaviour
These tools provide a normalised range estimate, which can be a more accurate reflection of battery health than your dashboard alone – especially if you’re comparing one car against others of the same make and model.
Making Sense of the Results
Whether you’ve done a few simple checks on the dashboard or dug deep with a diagnostic tool, the key question remains: what does it all mean? Understanding your battery data — and knowing what’s normal versus what’s concerning — is the final step in getting real value from your testing efforts.
Understanding Capacity Loss
The most important figure in most battery health tests is the remaining capacity compared to the original. If your EV launched with a 64kWh battery and your diagnostics suggest it now holds 58kWh, that’s about a 9% loss. For most vehicles, this kind of drop after a few years of driving is completely normal.
As a general guide:
- 0–10% loss: Typical for EVs under 5 years old with average mileage.
- 10–20% loss: Still within reason, especially for older or higher-mileage cars.
- 20%+ loss: Worth investigating further – the car may still be perfectly usable, but the reduced range could affect your day-to-day driving or resale value.
Keep in mind that range isn’t the only measure of battery health. Even with some degradation, many EVs still perform well and charge normally.
Spotting Warning Signs
Some indicators might suggest more serious issues:
- Inconsistent range estimates after charging
- Rapid drop in State of Charge during normal driving
- Unusual voltage readings across battery cells
- High internal resistance, which can point to ageing or damaged cells
- Trouble codes from your OBD2 scanner that relate to battery faults
If you’re seeing one or more of these — especially combined with performance issues or excessive heat during charging — it’s worth getting a professional assessment.
Comparing Against Other EVs
One of the best ways to interpret your results is by comparing them to the same model of a similar age. Many apps and forums share battery health data from real-world owners, making it easier to benchmark your EV.
For example:
- Is your estimated range noticeably lower than other 2019 Nissan Leafs with similar mileage?
- Are other owners seeing similar capacity loss or charge behaviour?
- Does your charging speed seem significantly slower?
These comparisons can help you determine whether your car is showing expected wear or something out of the ordinary.
What to Do If You’re Worried
If the results suggest your battery isn’t performing as it should:
- Check your EV battery warranty – many EV batteries are covered for 8 years or 100,000 miles, often including capacity loss beyond a certain threshold.
- Speak to a specialist – a service centre or EV-savvy technician can run more advanced diagnostics.
- Track the data over time – one test might show a blip, but patterns matter more than single results.
The Final Word on EV Battery Testing
Testing the health of an EV battery doesn’t have to be complicated — and it certainly doesn’t require a workshop full of tools. There’s a lot of battery testing options out there.
For most drivers, simple at-home checks using the dashboard, range estimates and state of charge monitoring will be more than enough to spot any early signs of wear. If you want a bit more insight, pairing an OBD2 reader with a trusted app can give you a much deeper view of the battery’s internal condition.
And when accuracy really matters — especially if you’re selling or buying second-hand — it’s worth investing in a professional diagnostic test or checking what your manufacturer offers in terms of software tools and battery reports.
Understanding your EV’s battery health helps you make smarter decisions, whether you’re managing your charging habits, planning a long journey, or evaluating a car’s long-term value.
Still have questions? Check out our Electric Car Maintenance Hub for more guides, tips and tools!
John is the Editor and Spokesperson for Electric Car Guide.
With over 20 years of writing experience, he has written for titles such as City AM, FE News and NerdWallet.com, covering various automotive and personal finance topics.
John’s market commentary has been covered by the likes of The Express, The Independent, Yahoo Finance and The Evening Standard.
