Rust is a deal-breaker that photos can hide, so be systematic. High-risk areas to check: 1. Underbody and frame rails—surface rust is normal, but flaking or bubbling paint means advanced corrosion 2. Wheel arches and rocker panels—these trap mud and salt 3. Door bottoms and the trunk floor—water collects here; lift the trunk mat and look for dampness or repair welds 4. Around the windshield and sunroof drains—leaks cause hidden rust in the A-pillars Ask the inspector to do a magnet test: filler-repaired areas won't hold a magnet, indicating past accident repairs. A paint thickness gauge reveals resprayed sections—uniform readings around 80-150 microns are normal; spikes over 300 suggest bodywork. Cars from northern China (salted roads in winter) or coastal cities need extra scrutiny on the underbody. If structural members show corrosion, walk away—repairs rarely restore original strength.

Battery condition is the single most important — and most expensive — variable in a used EV. Ask for a State of Health (SOH) report: in China, dealers and authorized service centers can read it via the manufacturer diagnostic system. It shows remaining capacity as a percentage of the original. Rule of thumb: above 90% is excellent, 85-90% is acceptable for the price, below 80% needs a serious price cut or battery refurbishment. Also get the battery's full charge and discharge history (次数) — a 3-year-old car with 800 fast-charge cycles has lived a harder life than one with 200. Physically, inspect the battery pack enclosure on a lift for dents, corrosion, or coolant leaks. Check that DC fast charging works during a test charge. Finally, verify the battery is not covered by an open recall or replacement program — this is both a risk and sometimes a free upgrade.

It's extremely difficult. Unauthorized modifications can lead to module current overload protection, resulting in a lock. In China, you need to use the factory online engineer account to reprogram it. It's basically impossible to perform online decoding overseas. We strongly warn against blindly modifying the electrical systems of modern integrated circuit vehicles.