Diagnosing Power Module Failures with ArduPilot CURR Logs

TL;DR: Monitor your drone's CURR logs for anomalies, especially ERR Subsys=25 ECode=1 indicating potential thrust loss, and implement MOT_SAFE_DISARM for safety during motor failure detection.

What is the CURR Log in ArduPilot?

The CURR log, now referred to as the BAT log in versions 4.0 and above, contains critical information about the battery and power system's performance. It provides insights into current consumption and voltage levels, essential for diagnosing power module failures.

BAT TimeUS  Inst  Volt  VoltR  Curr  CurrTot  EnrgTot  Temp  Res  RemPct  H  SH

• TimeUS: Timestamp of the log entry in microseconds.
• Inst: Instance number of the battery being logged.
• Volt: Actual voltage being supplied to the system.
• Curr: Current draw in amperes.
• CurrTot: Total current consumed in milliamp-hours (mAh).

Key Takeaway: The BAT log is vital for monitoring battery health and diagnosing power module issues.

How to Confirm Power Module Issues in Mission Planner

To effectively diagnose power module failures using Mission Planner, follow these steps:

1. Open Mission Planner.
2. Navigate to Flight Data.
3. Go to DataFlash Logs and select Review a Log.
4. Choose the log file you want to analyze.
5. Plot the following fields together: BAT.Volt, BAT.Curr, BAT.CurrTot, BAT.RemPct.

Key Takeaway: Plotting critical parameters in Mission Planner can help identify power module issues early.

How to Analyze Power Module Logs in MAVExplorer

Using MAVExplorer provides a more detailed analysis of the BAT logs:

MAV> graph BAT.Volt BAT.Curr

This command will plot battery voltage against current draw. Anomalies such as significant dips in voltage while current consumption remains high can indicate power module failures.

Key Takeaway: MAVExplorer allows for precise visualization of power metrics that aid in diagnosing module failures.

Why Power Module Failures Happen — Ranked by Common Causes

1. Voltage Drops: Frequent voltage drops in the BAT.Volt logs can indicate a failing power module or battery.
2. High Current Draw: If BAT.Curr is consistently above expected levels, it may signal issues with the motors or ESCs.
3. Battery Health: A BAT.RemPct consistently low suggests that the battery is aging and may not supply adequate power.
4. Overheating: Elevated BAT.Temp readings can indicate overheating, which is often a precursor to module failure.

Key Takeaway: Understanding the common causes of power module failures can enhance troubleshooting efficiency.

What Are the Fixes for Power Module Failures?

1. Monitor BAT.Volt and ensure it remains above the threshold (often 3.5V per cell).
2. Check for consistent high values in BAT.Curr and investigate motor or ESC issues.
3. Consider using MOT_SAFE_DISARM to prevent crashes during suspected power module failures.
4. Replace aging batteries if BAT.RemPct shows consistently low values.
5. Ensure proper cooling to mitigate high temperatures indicated by BAT.Temp.

Key Takeaway: Implementing specific fixes based on log analysis can prevent potential failures.

When This Isn't Actually a Power Module Failure

• Occasional voltage spikes could be normal operational fluctuations and not indicative of failure.
• Motor failures may sometimes mimic power module issues; check motor logs for specific errors.
• Battery voltage dips during high load are common, but sustained drops warrant investigation.

Key Takeaway: Distinguishing between actual power module failures and operational quirks is crucial for accurate diagnostics.

When LogHat Helps — and When It Doesn't

LogHat excels at analyzing flight logs to identify anomalies in power module performance and can highlight specific log messages indicative of failures. However, it cannot diagnose issues if the logs are incomplete or corrupted, nor can it replace hands-on troubleshooting techniques.

Key Takeaway: LogHat is a powerful tool for log analysis but should be used alongside physical inspections and maintenance protocols.

How can I tell if my drone has a power module failure?

Look for consistent RCOU channel saturation and CURR log anomalies.

What should I do if I suspect a motor failure?

Check MOTB.LiftMax values and consider using MOT_SAFE_DISARM for safety.

How do I analyze CURR logs for anomalies?

Focus on voltage and current readings during critical flight phases and check for unexpected spikes or drops.

What tools can help in diagnosing power module issues?

Mission Planner and MAVExplorer are excellent tools for visualizing and interpreting logs.

What are the signs of overheating in log data?

Elevated temperature readings in the BAT.Temp field indicate potential overheating.

How often should I check my drone's power module logs?

Regular checks after significant flights or when experiencing performance issues are recommended.

What is the importance of monitoring BAT.RemPct?

It provides insight into battery health and can indicate when a replacement is necessary.

If you're facing challenges with power module diagnostics, consider using LogHat to gain deeper insights into your flight logs. Our platform can help streamline your troubleshooting process and enhance your understanding of potential issues.