How to Check Battery Health When Buying a Used EV

• Understand the impact of factors like charge cycles, heat, and age on battery performance.
• Check the EV’s battery warranty coverage, including its transferability, and inspect the vehicle history report for accidents or issues that might affect the battery. Ensure the battery software is updated for optimal performance.
• Consider professional inspections for battery health data with a detailed and reliable assessment before purchase.

When you consider buying a used electric vehicle (EV), one of the most critical factors to assess is the health of its battery. The battery is an essential and expensive part of an EV, and its condition directly impacts the vehicle’s range, performance, and overall value. Here’s our guide on how to check the battery health of a used electric car before making your purchase.

• Understanding EV Battery Lifespan
• Methods to Check Used EV Battery Health
• Additional Considerations for Used EV Batteries

Understanding EV Battery Lifespan

Before diving into the assessment methods, it’s important to understand that EV batteries typically last between eight and 15 years. Most manufacturers offer battery warranties that cover eight years or 100,000 miles, the federally mandated minimum.

However, all EV batteries experience some capacity loss over time, which is typical and expected. A recent study from the SLAC-Stanford Battery Center suggests that the average electric car’s battery could last as much as 40% longer than today’s tests predict.

Why Do EV Batteries Degrade?

EV batteries, typically lithium-ion batteries, lose capacity over time due to chemical processes occurring during charging and discharging. This degradation reduces the amount of energy the battery pack can store and, therefore, the distance the car can travel on a single charge.

Reasons for EV battery degradation include:

• Charge and discharge cycles — Every time a driver charges and uses the battery, it undergoes a cycle. Each charging cycle slightly reduces its capacity.
• Heat — Excessive heat accelerates chemical reactions inside the battery, leading to faster wear.
• Age — As with other components, batteries degrade with age, regardless of use.

How Fast Do EV Batteries Degrade?

Battery degradation varies depending on the make and model, usage, and environmental factors. Most EV batteries lose about 2% to 3% of their capacity each year. For example, a 5-year-old EV might still retain around 85% to 90% of its original battery capacity if it has been cared for properly. However, this rate can be slower or faster depending on how well the battery is maintained.

RELATED: EV Battery Maintenance Guide

Methods to Check Battery Health of a Used EV

It’s essential to assess the battery to ensure you’re getting good value when buying a used electric car. Here are some steps you can take to get a sense of the EV’s battery health.

Battery Health Indicators

Most newer EVs come equipped with built-in battery management systems (BMS) that provide valuable information as a health report:

• Check the vehicle’s dashboard or infotainment system for battery health metrics.
• Look for indicators like battery capacity percentage or health status.
• Some models have specific battery health meters.

Autotrader Listings With Battery Health Data

Autotrader, along with our sister site Kelley Blue Book, has some VIN-specific battery health data on used EV listings on the site. Providing battery health on listings gives shoppers confidence when shopping for used electric cars online.

Range Comparison

One of the simplest ways to gauge battery health is by comparing its current range to the original EPA estimate:

• Fully charge the vehicle.
• Check the estimated range displayed on the dashboard.
• Compare this figure to the original EPA range for that specific model and year.

A healthy battery should provide a range close to the original estimate, accounting for a small percentage of degradation over time. Keep in mind that factors like weather conditions and driving habits can affect range estimates.

State of Charge (SOC) Observation

During a test drive, pay attention to the State of Charge indicator:

• Note the starting SOC percentage.
• Drive the vehicle for a reasonable distance.
• Observe how quickly the SOC drops.

If the SOC decreases abnormally fast during casual city driving, it could indicate a battery issue.

Ask About Charging History

Inquire whether the owner frequently used DC fast chargers. Relying heavily on fast charging can strain EV battery packs. Knowing the car owner’s charging habits can provide clues about the battery’s condition.

Inspect for software updates: Some manufacturers release updates to optimize battery performance. Check if the vehicle has received these updates. Ensuring the EV has the latest software updates can improve battery management and overall performance.

RELATED: Can You Overcharge an Electric Car Battery?

Professional Inspection

For a comprehensive assessment, consider having the vehicle inspected by professionals using specialized apps or manufacturer-specific diagnostic tools:

• Take the EV to a certified dealership or service center for a diagnostic scan.
• Trained technicians can provide detailed information about the battery’s condition.
• While this may come at a cost, it can offer peace of mind for a significant purchase.
• Ask the seller if they have a recent comprehensive battery health report.

Additional Considerations for Used EV Batteries

While battery prices have significantly decreased over the past 15 years, an EV’s battery pack can make up a third to a half of the value of a secondhand electric car.

• Always check the remaining battery warranty coverage. Understand the terms and conditions, including what percentage of capacity loss is covered. Even more importantly, be sure to check if the warranty is transferable.  
• Review a full vehicle history report to identify accidents that could have affected the battery.
• Avoid vehicles with salvage titles or frequent ownership changes.
• Check for any open recalls that might affect battery function.
• If buying from a different region, factor in how the new environment might impact the battery. Extreme temperatures can affect battery performance and longevity.
• MORE: Used Electric Car Buying: Is Mileage Important?

Checking a used electric car battery’s health involves a combination of methods, from simple range comparisons to specialized diagnostic scans and detailed reports. By thoroughly assessing the battery’s condition, you can make an informed decision and help ensure that your used EV purchase provides reliable performance for years to come. Remember that some battery degradation is expected, but significant loss of capacity or range should be a red flag. Don’t hesitate to seek professional assistance or opt for a certified pre-owned EV with a warranty for added peace of mind.