Used EV Battery Health: 6 Checks Before You Buy in 2026

Used EV battery health is the single number that decides whether a $12,000 car is a bargain or a $6,000 mistake. Anything above 90% state of health (SOH) is good; below 85% on a car under four years old means the pack had a hard life.

Chinese LFP packs are forgiving, which makes this easier than buying a used Nissan Leaf. It does not make it optional.

What is state of health and why does it matter?

SOH is remaining usable capacity as a percentage of the original. A 60 kWh pack at 90% SOH holds 54 kWh of usable energy. You lose range linearly, so a 510 km car becomes a 460 km car – tolerable. At 80% SOH it becomes a 408 km car and the owner starts noticing charging stops.

For LFP cells, degradation follows a slow curve: most of the loss happens in the first 30,000 km, then it flattens. That means a 2022 car with 80,000 km is often in better shape per kilometre than one with 15,000 km that was fast-charged daily.

How do you get a real SOH number?

• Manufacturer app screenshot – BYD, Leapmotor and GAC apps report capacity. Ask the seller to log in on video call, not send a photo.
• Dealer diagnostic printout – a 4S dealer will run the BMS scan for around 200 RMB and hand you a report.
• Full-charge range test – charge to 100%, note the estimated range, then compare to the original rated range.
• DC charging curve – a healthy pack accepts its rated peak. One that stalls at half the peak is derating.

Of those four, the dealer printout is the only one you should trust for a decision. App screenshots are easy to fake and range estimates are software guesses.

What are normal SOH numbers by age?

• 1 year, 15,000 km: 97-99%
• 2 years, 35,000 km: 94-97%
• 3 years, 60,000 km: 90-94%
• 4 years, 90,000 km: 86-91%
• 5 years, 130,000 km: 82-88%

A 2022 BYD at 84% SOH is below the curve and you should assume it was fast-charged hard or sat at 100% in the heat. A 2021 car at 92% is above the curve and worth a premium.

Which cars age best on the used market?

LFP chemistry wins. Every BYD Song Plus EV and Atto 3 uses Blade LFP cells that tolerate 3,000-plus full cycles. Smaller cars like the Leapmotor T03 also run LFP.

NMC packs – common in older premium EVs and some early Zeekr models – degrade faster and dislike being held at high charge. If you are buying NMC, subtract 4-5 percentage points from the expected SOH table above.

Is a low-SOH car ever worth buying?

Only with a discount that reflects the risk. A replacement LFP pack for a Chinese compact EV costs $3,500-$6,000 installed, depending on model and where you are. If a seller drops the price by $2,500 on an 80% SOH car, you are absorbing the risk, not being compensated for it.

There is one exception: a car at 80% SOH with 200,000 km that you plan to use locally for short trips. At the right price – 55% of a good example – it still makes sense.

Key Takeaways

• Above 90% SOH is good; below 85% on a car under four years old is a red flag.
• Get a dealer BMS printout, not a seller’s app screenshot.
• Expect 90-94% SOH at three years and 60,000 km for LFP packs.
• LFP Blade packs age better than NMC – factor 4-5 points for NMC cars.
• A replacement pack costs $3,500-$6,000, so discount low-SOH cars accordingly.