Buy the battery, not the odometer. A car’s real value tracks its battery’s health — and that’s a number you can check before you commit.
What “battery health” actually means
State of health is the percentage of the battery’s original capacity it can still hold. A car at 92% SOH retains most of its original range; one at 75% has lost a meaningful chunk. It’s not the same as the range number on the dash, which can drift — SOH is the underlying truth, and it’s what a proper diagnostic measures.
Why it matters more than mileage or age
Two EVs of the same year and mileage can have very different batteries depending on how they were charged and where they lived. A well-treated, higher-mileage pack can be healthier than a low-mileage one that was abused. Degradation also isn’t linear — many EVs lose a little capacity early, then settle into a slow, gradual decline. That’s why odometer and model year alone can mislead you.
What affects battery degradation
- Heat — sustained high temperatures are hard on batteries.
- Frequent DC fast-charging — convenient, but heavy reliance on it can accelerate wear.
- Charging habits — routinely charging to 100% or running to near-empty is harder on a pack than staying in the middle.
- Age and cycles — time and total charge cycles both add up.
How battery health translates to dollars
Range sells. A used EV with a verified, healthy battery commands more because the buyer is getting more usable car — and dealers and private buyers price it in. For a buyer, confirming SOH protects you from overpaying for a tired pack. For a seller, a documented healthy battery is one of the best ways to justify your asking price.
How to check an EV’s battery health
Don’t rely on the dashboard range estimate alone. A proper state-of-health test reads the pack’s real remaining capacity and flags any issues. Ask the seller for it — and if they can’t provide one, get it done independently before you buy. We perform SOH testing, including on a car you’re considering from another seller.
Warranty still counts
Remaining battery and drivetrain warranty adds real value and peace of mind. Know how many years and miles are left and whether it transfers to you — it can offset the risk of future degradation. More on the buying side in What to Know Before Buying a Used Tesla.
The bottom line
A verified healthy pack is the difference between a used EV that serves you for years and one that disappoints — and it’s a number you can get before you commit. When in doubt, test it.
Quick answers
What’s a good battery state-of-health percentage?
Higher is better — many EVs still show strong SOH after several years of normal use. The right benchmark depends on the model and age, so it helps to know what’s normal for the specific car.
Does fast charging ruin an EV battery?
Occasional fast charging is fine — heavy, near-exclusive reliance on it can speed up wear over time.
Can you test a battery before I buy?
Yes — we perform state-of-health testing, even on a vehicle you’re considering from another seller.