EV Battery Degradation Calculator

Why EV Battery Degradation Matters

Electric vehicle (EV) batteries slowly lose their ability to hold energy as they age. This process is called battery degradation, and it directly affects how far you can drive on a charge. Even if your driving habits stay the same, an older battery will usually provide less range than when the car was new.

Understanding degradation helps you:

• Estimate how much real‑world range to expect over the next few years.
• Decide whether a used EV still has enough battery capacity for your needs.
• Plan financially for a possible battery repair or replacement out of warranty.
• Adjust your charging and parking habits to slow down unnecessary wear.

This calculator gives a simplified estimate of remaining battery capacity based on a few key factors: age in years, mileage, number of charge cycles, and climate stress. It does not replace professional diagnostics, but it offers a quick way to see how these variables might add up over time.

How This EV Battery Degradation Calculator Works

The calculator uses a simple percentage‑based model to approximate how much capacity your battery may have lost. It adds degradation from several sources and then applies that loss to your original battery capacity in kilowatt‑hours (kWh).

The core idea is to estimate a total degradation percentage, then apply it like this:

Where TotalDegradationPercent comes from the following components:

• Calendar aging: about 2.5% per year of age.
• Mileage‑related wear: about 0.5% per 10,000 miles driven.
• Charge‑cycle wear: about 0.1% per full charge cycle.
• Climate factor: an extra adjustment from 0 to about 2%, depending on how extreme your climate is.

The calculator adds these components together to get a single degradation percentage. For example, if the age, mileage, cycles, and climate add up to 22%, the tool assumes the battery has lost 22% of its original capacity.

To keep results within a typical range for most modern EVs, the model caps the total predicted loss at 30%. That means, even if the simple formula would produce a larger number, the output will not exceed 30% capacity loss. This cap prevents unrealistic results when extreme values are entered.

Finally, the remaining capacity in kWh and the remaining percentage of original capacity are reported. This lets you connect the estimate to both energy and range. For example, going from 75 kWh to 60 kWh is also going from 100% to 80% of the original capacity.

Understanding the Calculator Inputs

Each input field represents a different aspect of battery wear. Accurate entries will lead to more realistic estimates.

Original Battery Capacity (kWh)

This is the manufacturer’s rated size of your battery pack, measured in kilowatt‑hours (kWh). Common sizes are 40 kWh, 60 kWh, 75 kWh, 82 kWh, and so on.

• Check your owner’s manual, window sticker, or manufacturer website for the official pack size.
• If your EV has a 75 kWh battery, enter 75 in this field.

Age of Vehicle (years)

Battery cells degrade over time even if the car is driven very little. This is called calendar aging.

• Use the age in years since the vehicle (or battery pack) was first put into service, not just the model year.
• Round to the nearest tenth if you want more precision. For example, 3.5 years.

Total Miles Driven (thousands)

Mileage is a rough stand‑in for how many times the battery has been charged and discharged. Higher mileage generally means more wear.

• The field expects thousands of miles, not total miles.
• If your odometer shows 60,000 miles, enter 60.
• If your odometer shows 12,500 miles, you can enter 12.5.

Charge Cycles

A charge cycle is roughly one full charge from 0% to 100%, but it can also be built up from partial charges (for example, two 50% charges).

• If you have access to battery logs or manufacturer data, use that value.
• If not, you can estimate: daily charging over three years might be on the order of 1,000 cycles.
• Enter the approximate number of full‑equivalent cycles (e.g., 800, 1,200, etc.).

Climate Factor (0 mild, 2 extreme)

Temperature has a major influence on battery health. Very hot or very cold conditions tend to accelerate degradation, especially if the car is parked outside or fast‑charged often.

• 0 – Mild, temperate climate; limited time in very hot or very cold weather.
• 1 – Moderately hot or cold climate; significant seasonal extremes.
• 2 – Very hot or very cold most of the year; frequent exposure to temperature extremes.

If you are unsure, using 1 is a reasonable middle‑of‑the‑road assumption.

Interpreting Your Results

After you enter your details and run the calculation, you will see two key outputs:

• Estimated remaining capacity (kWh) – how much energy your battery can still store.
• Estimated remaining percentage (%) – how that compares to the original capacity.

You can use these numbers to think about how your EV will perform in daily use:

• If you know your car originally had 250 miles of rated range at 75 kWh, then 60 kWh (80% remaining) might translate to roughly 200 miles under similar driving conditions.
• A remaining capacity of 90% or higher is generally considered very healthy, especially for vehicles a few years old.
• Remaining capacity around 70–80% may be normal for an older, higher‑mileage EV.
• Below about 70%, some drivers may notice a clear reduction in usable range for long trips.

Battery warranties often trigger inspection or replacement if capacity falls below a certain threshold (for example, 60–70% of the original). Check your specific warranty terms if your estimated result is near those levels.

Worked Example

Consider a mid‑size EV with the following characteristics:

• Original battery capacity: 75 kWh
• Age: 4 years
• Total miles driven: 60,000 miles (enter 60 in the field)
• Approximate charge cycles: 800
• Climate factor: 1 (moderately hot or cold climate)

The model estimates degradation like this (values rounded for illustration):

• Calendar aging: 4 years × 2.5% ≈ 10%
• Mileage wear: 60,000 miles ≈ 6 × 10,000 miles → 6 × 0.5% ≈ 3%
• Cycle wear: 800 cycles × 0.1% ≈ 80% before capping (the internal model ultimately caps the total combined loss at 30% to stay realistic).
• Climate factor: 1 → about 1% extra degradation.

If you simply add those raw components, they would exceed 30%. Because that is not realistic for most real‑world EVs in this age and mileage range, the calculator applies its 30% cap on total degradation. The effective result is therefore:

• Total degradation (capped): 30%
• Remaining capacity: 75 kWh × (1 − 0.30) = 52.5 kWh
• Remaining percentage: 70% of the original capacity

The narrative interpretation might be: “Based on these inputs, the battery is estimated to be at about 70% of its original capacity, with around 52.5 kWh remaining out of 75 kWh. This would reduce typical driving range compared with when the car was new, but it may still be suitable for many daily commutes.”

Comparison Table: Example Degradation Scenarios

The table below shows some simplified, hypothetical examples to give you a sense of how age and mileage might relate to remaining capacity under typical conditions. These values are approximate and for illustration only.

Real‑world values can be higher or lower than these ranges. Some EVs retain over 90% capacity after many years, while others may degrade faster depending on chemistry, thermal management, and usage.

Limitations and Assumptions

This tool is designed as an educational approximation rather than a precise diagnostic. Several important assumptions are built into the model:

• Generalized percentages: The 2.5% per year, 0.5% per 10,000 miles, and 0.1% per cycle values are broad, averaged figures. They are not based on any one brand or model.
• No chemistry‑specific behavior: Different battery chemistries (for example, NMC vs. LFP) can degrade at different rates. The calculator does not distinguish between them.
• Simplified climate factor: Climate is represented by a single number from 0 to 2. In reality, temperature effects depend on how the car is stored, how its thermal management works, and how often it is fast‑charged.
• Fixed 30% cap: The cap on total degradation keeps results in a reasonable range but may under‑estimate loss for very old or heavily abused batteries, or over‑estimate loss for extremely robust packs.
• No driving‑style adjustment: Aggressive acceleration, towing, frequent high‑speed driving, and frequent DC fast charging can all influence degradation, but they are not explicitly modeled.

Because of these limitations, you should treat the output as a ballpark estimate. For important decisions—such as a high‑value used EV purchase, warranty claim, or major repair—combine this estimate with:

• Manufacturer‑supplied health reports or official diagnostics.
• Onboard battery health readouts, if your vehicle provides them.
• Professional inspection and test reports from a qualified service center.

Nothing in this calculator should be taken as financial, legal, or engineering advice. Always check your specific vehicle documentation and local regulations before making major decisions.