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EVChargeCurve
Empirical Telemetry Standards

Testing Procedures & Protocol

How DC fast charging sessions are recorded, normalized, and validated using direct OBD-II CAN bus telemetry under documented thermal and electrical conditions.

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Standardized Test Session Criteria

Prerequisites for logging canonical charging curves

To ensure data comparability across vehicles, DC fast charging curve sessions adhere to strict testing parameters:

Starting State of Charge (SoC)

Sessions initiate at or below 10% SoC (optimally 4–8% SoC) to observe the initial voltage ramp and peak power acquisition phase.

Thermal Preconditioning

Baseline canonical curves require an active preconditioning cycle reaching optimum battery pack temperature (typically 25°C to 32°C).

Dispenser Headroom

Tested on DC fast chargers with rated output exceeding the vehicle's peak acceptance rate (e.g. 350 kW / 500A liquid-cooled dispensers for 800V vehicles).

Continuous Uninterrupted Dwell

Single session recording without cabin HVAC changes, mid-session station reboots, or shared-cabinet power throttling.

Telemetry Equipment & Software

Standard tools used by maintainers and community contributors

We record internal high-speed CAN-bus data rather than solely relying on the dispenser screen. This allows us to separate BMS limits from dispenser limits:

OBD-II Hardware Interfaces: OBDLink CX / MX+ Bluetooth 5.0 adapters, vLinker FD+ diagnostic interfaces, and direct CAN-logger harnesses configured for 500 kbps / 250 kbps vehicle bus baud rates.
Telemetry Software: CarScanner Pro (custom PID profiles), ScanMyTesla, Torque Pro, and self-hosted TeslaMate streaming telemetry loggers.
External Environmental Logging: Ambient temperature sensors, station dispenser nameplate rating, and cooling fluid inlet/outlet observations.

Recorded Telemetry Parameters

Standard time-series parameters captured at 1 Hz resolution

{
  "timestamp_iso": "2026-02-14T15:22:04Z",
  "soc_display_pct": 24.5,
  "soc_bms_actual_pct": 23.8,
  "pack_voltage_volts": 682.4,
  "pack_current_amps": 337.2,
  "calculated_power_kw": 230.1,
  "bms_requested_kw": 240.0,
  "battery_temp_min_c": 26.5,
  "battery_temp_max_c": 31.0,
  "ambient_temp_c": 18.0,
  "charger_type": "Alpitronic HYC300 (500A liquid-cooled)",
  "cumulative_kwh_added": 14.8
}

Known Limitations & Real-World Variance

Why your charging session may differ from canonical curves

Even under instrumented conditions, electric vehicle charging speed is governed by complex real-world variables:

  • BMS Firmware Differences: Automakers regularly modify battery thermal management and charging aggressive curves via over-the-air updates.
  • Cell Supplier Variations: The same vehicle model year may contain battery cells from different suppliers (e.g. LG, CATL, Panasonic, SK On) with slightly different internal resistance profiles.
  • Dispenser Current Throttling: If a station's liquid cooling cable derates due to a clogged filter or high ambient heat, dispenser output drops to ~200A regardless of what the vehicle can accept.
  • Utility Grid Limitations: Some charging hubs dynamically share a limited transformer capacity across multiple active stalls.
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