State of Health is the single most important number when buying, selling, or owning a used electric car. It tells you what percentage of the battery's original capacity remains — and directly determines the car's real range and real value.
What Does SOH Mean?
SOH is a percentage of original usable capacity. 100% means the battery is at full original capacity. 85% means 15% has been lost — roughly 15% less range than when new. It's not the same as State of Charge (how full it is now). SOH is the size of the tank; SOC is how much fuel is in it.
What's Normal by Model?
Nissan Leaf 40kWh: 85–92% (air-cooled, varies widely)
Tesla Model 3/Y: 90–95% (excellent thermal management)
Hyundai Ioniq 5 / Kia EV6: 93–97% (800V, minimal stress)
VW ID.3/ID.4: 91–95% (liquid-cooled MEB platform)
MG ZS EV: 88–94% (varies by chemistry version)
BMW i3: 88–92% (conservative battery management)
The SOH Ranges
95–100%: Excellent. Near-new performance. Under 2 years or 20,000 miles. Premium pricing justified.
90–95%: Very good. Normal for 2–4 years, moderate mileage. No concerns.
85–90%: Good. 10–15% range reduction. Most used EVs at 40,000–70,000 miles sit here. Price should reflect it.
80–85%: Negotiate. 15–20% range loss. A 200-mile car delivers 160–170 in ideal conditions. Still usable but the price must reflect reality.
75–80%: Caution. Significant loss. Winter range could be 40–50% below original. Check warranty — most guarantee 70% for 8 years.
Below 75%: Walk away — unless the price accounts for eventual replacement.
Why the Dashboard Isn't Proof
The SOH on your car's dashboard comes from the Battery Management System — an internal estimate that can drift from actual capacity by 3–8%. It's the car assessing itself. Not something a buyer should accept at face value when spending £10,000+.
An independent Aviloo certified test measures the battery separately from the car's own systems. The result is a certified, timestamped, QR-verifiable figure that any buyer, dealer, or insurer accepts as evidence.
Get Your SOH Measured
PAD offers Aviloo certified checks across Pontypridd, RCT, Cardiff, and South Wales. £79 for EVs, £89 for PHEVs. Mobile, certificate on site. Over 500 models covered.