Key Takeaways
- The battery pack can represent 30-50% of a used EV's total value.
- Battery degradation below 80% capacity significantly impacts range and resale value.
- Fast-charging history and climate exposure directly affect battery longevity.
1. Understanding Battery Degradation
All lithium-ion batteries degrade over time. A brand new EV might have 300 miles of range, but after 5 years and 60,000 miles, that could drop to 250-270 miles. This is normal.
The key question is whether the degradation is within expected parameters. A 2020 Tesla Model 3 with 90% battery health is normal. One with 75% health at the same age is a red flag that suggests abuse, excessive fast charging, or a defective cell module.
2. How to Check State of Health (SOH)
State of Health is the most important metric for a used EV battery. It compares current capacity to the original factory capacity. Here's how to check it:
For Tesla: Use third-party apps like Recurrent or Tessie that can read battery data through the Tesla API. The onboard screen shows estimated range, but this can be misleading.
For other EVs: OBD-II diagnostic tools like the LeafSpy app (for Nissan Leaf) or dedicated EV diagnostic scanners can read actual SOH percentages. Our inspectors carry professional-grade diagnostic equipment for all major EV brands.
3. Fast Charging History Matters
DC fast charging (Level 3) generates significant heat in the battery pack. Occasional fast charging is fine, but a vehicle that was exclusively fast-charged — common with rideshare and delivery vehicles — will show accelerated degradation.
Ask the seller about their charging habits. If they can't answer, or if the vehicle was a fleet/rideshare car, assume heavy fast-charging usage and factor potential battery wear into your offer price.
4. Climate and Storage Conditions
Batteries degrade faster in extreme heat. A used EV from Phoenix, Arizona will likely have more degradation than the same model from Portland, Oregon — even with identical mileage.
In Houston's climate, heat exposure is a real concern. Check if the vehicle was garage-kept or parked outside. EVs left in extreme heat with high state of charge (above 90%) degrade faster than those stored at moderate charge levels in shade.
Houston Heat Warning
Houston's average summer temperature accelerates battery aging. Always request charging records and storage conditions for used EVs purchased locally.
5. Warranty and Replacement Costs
Most EV manufacturers warrant the battery for 8 years or 100,000 miles, typically to 70% capacity. Check if the warranty is still active and transferable.
Battery replacement costs range from $5,000 for a Nissan Leaf to $15,000+ for a Tesla Model S. Understanding remaining warranty coverage is critical to your purchase decision and negotiating leverage.