Diagnosing Power Module Failures Using ArduPilot CURR Logs

TL;DR: Diagnose power module failures using ERR Subsys=25 ECode=1 and CURR logs. Look for consistent maximum values in RCOU channels and increasing roll/pitch errors to identify issues, and adjust FS_THR_ENABLE=1 for RTL activation.

What Are ArduPilot CURR Logs?

The CURR log messages in ArduPilot provide vital information on the power consumption of your drone during flight. This log assists in diagnosing issues related to power modules and motor performance. The relevant fields in the CURR logs include:

CURR TimeUS Inst Volt Curr CurrTot EnrgTot Temp Res RemPct H

• TimeUS: Timestamp in microseconds.
• Inst: Instance number of the log entry.
• Volt: Voltage of the power module.
• Curr: Current drawn by the drone motors.
• CurrTot: Total current consumed in mAh.
• Temp: Temperature of the power module in °C × 100.

Confirming It in Mission Planner

To analyze CURR logs, you should first load them into Mission Planner. Follow these steps:

• Open Mission Planner and connect your drone.
• Navigate to the Flight Data tab.
• Select DataFlash Logs from the menu.
• Click on Review a Log.

Focus on plotting the following fields together:

• Curr against Volt to analyze power consumption.
• CurrTot for total current draw over time.
• Temp to monitor any overheating issues.

Confirming It in MAVExplorer

In MAVExplorer, you can further analyze the CURR logs using commands to visualize the data. Here’s how:

MAV> graph CURR.Volt CURR.Curr

This command will help you plot the voltage against current, allowing you to observe any significant drops or spikes that could indicate power module issues.

Why Power Module Failures Happen — Ranked by What We See Most Often

1. Consistent Maximum Readings: When RCOU channels show continuous maximum values, it indicates that the motors are drawing excessive current due to a power module failure.
2. Increased Roll/Pitch Errors: A rise in roll or pitch errors can be observed in the logs, often due to insufficient power to maintain attitude control.
3. Voltage Drops: Significant voltage drops recorded in Volt readings may indicate failing batteries or poor connections within the power module.
4. Thermal Overload: Elevated Temp readings suggest overheating, which can lead to power module failures.

Fixes for Power Module Issues

1. Ensure connections to the power module are secure and free from corrosion.
2. Replace the power module if Volt readings fall below specifications (e.g., 8V for a typical 3S LiPo).
3. Adjust FS_THR_ENABLE to 1 to ensure RTL is activated during low throttle situations.
4. Monitor the Temp readings and ensure they remain within safe limits; consider cooling solutions if overheating persists.
5. Run a calibration on the power module to ensure accurate voltage and current readings.

When This Isn't Actually a Power Module Failure

• High current readings might also indicate motor stalling or excessive payload, not just power module issues.
• Temperature spikes can be caused by environmental factors rather than an internal power module fault.
• Voltage drops can occur due to poor battery health rather than a malfunctioning power module.

When LogHat Helps — and When It Doesn't

LogHat analyzes CURR logs to provide insights on power module performance and identify potential issues. However, it doesn't directly diagnose physical hardware problems like loose connections or faulty components. For those, we still recommend a hands-on inspection.

What are the signs of a power module failure?

Look for consistent maximum readings in RCOU channels and increasing roll/pitch errors.

How can I access CURR logs?

CURR logs can be found on the SD card used in your ArduPilot setup.

What should I do if I see high current readings?

Check for motor stalling or excessive payload, and consider inspecting the power module for faults.

How can I monitor temperature during flight?

Use the Temp field in the CURR logs for temperature readings of the power module.

What voltage is considered safe for a power module?

A typical safe voltage for a 3S LiPo power module should be above 8V.

For further engagement, explore our analysis tools at LogHat to enhance your diagnostic capabilities. Understanding your logs is key to ensuring optimal drone performance.