Battery Telemetry

The electrical potential difference between the battery's terminals, measured in volts. Open Circuit Voltage (OCV) correlates with State of Charge after a relaxation period, while Terminal Voltage under load reflects internal resistance. A sudden voltage sag during high current draw indicates increased internal impedance, a key degradation marker. Monitoring individual cell voltages in a series pack is critical for detecting imbalances that can lead to thermal runaway.

The rate of electron flow into (charging) or out of (discharging) the battery, measured in amperes. Coulomb Counting integrates current over time to estimate State of Charge. Precise current sensing is essential for calculating energy throughput and tracking charge/discharge asymmetry. Bidirectional hall-effect sensors capture both regenerative braking energy and propulsion consumption, feeding directly into the Energy Consumption Model.

Distributed thermal measurements from multiple points on the battery pack, typically via thermistors. This telemetry feeds the Battery Thermal Model to prevent lithium plating during cold charging and thermal runaway during fast discharge. Key metrics include:

• Cell core temperature: The internal electrochemical temperature, often estimated via a thermal model.
• Surface temperature: Measured at cell tabs or casing.
• Coolant inlet/outlet temperature: For liquid-cooled packs, indicating heat rejection efficiency.

A derived metric, expressed as a percentage (0-100%), representing the remaining capacity relative to the current maximum. Unlike a simple fuel gauge, SoC is algorithmically estimated by the BMS using sensor fusion of coulomb counting and voltage-based correction. Accurate SoC telemetry is the primary input for the Minimum Charge Threshold and Charge Scheduling Algorithm, dictating when an agent must divert from its mission.

A derived metric, expressed as a percentage, comparing the battery's current maximum capacity and power capability to its factory specifications. SoH degrades due to calendar aging and cycle aging. Telemetry inputs for SoH estimation include tracked capacity fade over many charge/discharge cycles and the rise in internal resistance inferred from voltage drop under load. SoH directly informs the Remaining Useful Life (RUL) prediction.

The battery's opposition to direct current flow, measured in milliohms (mΩ). DC Internal Resistance (DCIR) is calculated by the BMS by measuring the instantaneous voltage drop (ΔV) for a known current pulse (ΔI) using Ohm's law (R = ΔV/ΔI). A rising DCIR trend is the primary indicator of power fade and aging. This metric is critical for the Fast Charging Protocol, as higher resistance generates more heat (I²R losses) during high-current charging.