[TASK] Battery Management System

[forrisdahl]

Description:
The BMS MCU should provide core functionality for monitoring and communication.

Requirements

• Safty meachanism

  • Detect when either the systems voltage, current, temperature or pressure exceeds a safe threshold
  • Trigger appropriate fault/alert mechanism.
    • Regulate the voltage during charging
    • Trigger an Off-switch (Kill-switch) to initiate a power shutdown if safe threshold exceeds to

• Measurement

  • Read current consumption
  • Read voltage levels
  • Read the batteries temperature (Celsius)
  • Read the battery compartments pressure (bar)

• I2C communication *

  • Relevent external sensors transmit measured values (temperature and pressure) to the BMS MCU

• CAN communication

  • Transmit measured values (current, voltage, temperature, pressure fault status) over CAN bus
  • Support configurable message IDs

Acceptance Criteria

• Any problamatic events that may cause damage to the AUV are reliably detected and flagged
• Current, voltage, temperature and pressure data can be read and verified against test conditions
• CAN messages are sent at the specified interval with correct data formatting

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To-Do Checklist

• Research peripherals and sensors (e.g., ADCs, shunt resistors, current sensors, CAN transceivers)
• Assist electrical selecting components and confirm availability for MCU integration
• Implement drivers for each peripheral (ADC, current sensor, CAN)
• Integrate all peripherals into MCU firmware
• Verify functionality on development board (bench testing)
• Validate on final PCB hardware
• Document configuration parameters (thresholds, scaling, CAN message format)

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Contacts

• @forrisdahl
• @IbixD97

[Andrelimi]

👍 Lest 👍

[forrisdahl]

For much of the past year, we have had very limited data on the energy consumption of our drone. This has created a great deal of uncertainty. One of the main motivations for introducing a dedicated MCU for the BMS is to accurately track the drone’s energy consumption, enabling us to better estimate lifetime and detect when excessive current is being drawn.

Previously, the electrical team developed a Power Sense Module (PSM) to provide voltage and current measurements from the batteries. The module did not measure each cell individually, but rather the combined output of both batteries. In testing, the ADC readings were fairly accurate, and the system appeared to work well. However, integrating the PSM into the drone turned out to be far more challenging than expected.

The I²C communication between the Orin and the PSM proved to be very unstable and, in practice, did not work reliably at all. The exact cause of this instability is unknown, but I suspect it may be related to the PSM’s power supply. The PSM was powered from the Orin’s 3.3 V pin, which may not have been able to provide sufficient power. As a result, the PSM may have either failed to operate correctly or received an incorrect reference voltage. This instability on the PSM side caused significant issues on the I²C bus, leading to major problems both in sub-ops preparation and during Easter testing.