How we calculate your Tesla battery health

When you click Generate Passport, we call the official Tesla Fleet API endpoint /api/1/vehicles/{id}/vehicle_data with three endpoint groups:

• charge_state — battery_level (%), ideal_battery_range (mi), charge_limit_soc
• vehicle_state — odometer (mi)
• vehicle_config — car_type, trim_badging, exterior_color

Tesla reports the ideal_battery_range at your current state of charge. We linearly project that to a 100% charge:

range_at_100% = (ideal_battery_range / battery_level) × 100

Example: a Model 3 LR showing 220 mi at 65% projects to (220 / 65) × 100 = 338.5 mi at full charge.

We divide the projected full-charge range by the original EPA-rated range for your exact model, year, and trim:

SoH (%) = (range_at_100% / EPA_rated_range) × 100

On your dashboard, we display the SOC-weighted median of up to 180 days of snapshots — not a single live reading. Snapshots taken at SOC ≥ 80% are weighted 2×, SOC 50–79% at 1×, SOC 20–49% at 0.5×. The median resists outlier days caused by temperature or unusual driving. The live reading is shown separately so you can see both. Snapshots taken within 3 days of a Tesla OTA software update are excluded to avoid artificially shifting the trend.

EPA-rated values come from Tesla's filings (e.g. Model 3 LR 2021+ = 358 mi, Model Y LR 2024+ = 310 mi, Model S Plaid = 396 mi). Values below 75% are flagged as LOW rather than discarded — high-mileage cars can legitimately reach this range. Values outside 70–100% are flagged as sensor anomalies and excluded from the median — never clamped or adjusted.

Cycle count is derived from the actual energy you've put through the pack. We sum every kWh logged in your daily telemetry (home + Supercharger) and divide by usable pack capacity. If you have no telemetry yet, cycles is shown as '—' — never a guess from odometer.

cycles = Σ(kwh_charged_home + kwh_charged_supercharger) / pack_kWh_usable

Pack capacity (usable): Model 3 LR/Performance ≈ 78 kWh, Model Y LR ≈ 75 kWh, Model Y Standard (LFP) ≈ 57.5 kWh, Model S ≈ 100 kWh (Plaid 95), Model X ≈ 100 kWh (Plaid 95).

degradation_rate (%/yr) = (100 − SoH) / vehicle_age_years

Your SoH is benchmarked against the live mean of the latest health report from every Tesla in our database that matches your model, year, and 20,000-km mileage band. No external benchmark, no hardcoded number — if 18 other 2022 Model 3s with 60–80k km are in the fleet, we average those 18. When the same-segment cell has fewer than 5 cars we widen scope to same model + year, then same model, and label the comparison accordingly. The segment average is recomputed every time a new passport is generated.

fleet_avg = mean(latest_report.soh_pct for peers in same model + year + 20k-km mileage band)

When even the broadest cohort (model only) has fewer than 5 comparable cars, the certificate omits the fleet comparison entirely rather than show a fabricated number.

Each passport is written to our database with a unique public_slug and a tamper-evident URL at /passport/{slug}. Buyers can verify authenticity at any time via the public verify endpoint — /api/public/verify/{slug} — which returns the issuance timestamp and the original SoH reading.