Used EV Battery Health: How to Check It Before Export

A used EV is only as good as its battery, so demand an SOH (state of health) report above 90% before you commit. SOH is a percentage: 100% is a factory-fresh pack, and each point lost is real range gone. On a small city EV, dropping from 95% to 85% can cut 40km from a 250km day.

The dashboard shows a range estimate, which is a guess based on the last drive. A BMS scan shows the truth: cell balance, internal resistance, and the pack’s actual capacity against its original rating.

Why is SOH more important than mileage?

Because a low-mileage car can still have a tired battery. A car that lived on fast chargers, or baked in a hot southern Chinese city, ages faster than a high-mileage car that charged slowly at home. A Changan Lumin with 20,000km and 94% SOH beats a 6,000km example at 86% every time.

• Above 93%: excellent, near-new condition.
• 90-93%: good, expected for a 2023-2024 car.
• 85-90%: usable, price it down.
• Below 85%: walk away unless the price is very low.

What exactly should I ask the seller for?

Ask for a BMS screenshot showing SOH percentage, cell voltage spread, and charge cycle count. Add a photo of the pack label with its manufacture date. Then ask for a DC fast-charge test record showing the peak kW actually delivered — a pack that once took 40kW and now takes 22kW is telling you something.

For LFP packs, used in the BYD Seagull, expect slower degradation and better tolerance of full charging. For NMC packs, used in larger cars like the GAC Aion Y 70, degradation is a little faster and high heat is the enemy.

What are the red flags?

Any seller who refuses an SOH scan is hiding something. Watch for mismatched cell counts after a repair, a missing pack label, or a car that was written off in an accident and rebuilt — those often carry compromised battery mounts. Also be wary of a pack that was “replaced” with no paperwork; you cannot verify its age.

On arrival, pay for your own independent scan. If the SOH differs from the seller’s report by more than two points, you have a conversation to have, and a strong position if you have the original documentation.

Key Takeaways

• Demand an SOH report above 90% on any used EV.
• Mileage matters less than battery health and charging history.
• Ask for BMS data, pack label date and a fast-charge test record.
• No SOH scan offered is itself a red flag.