Event Log of Bluetooth App

In most lithium battery Bluetooth apps, the “Log History” (or Event Log / History Log) function is a built-in record of what the BMS (Battery Management System) has detected and stored over time.

Think of it as a black box for the battery.

Here’s what you typically find inside:

? 1. Protection Events (Fault Logs)

Records whenever the BMS had to protect the battery, such as:

• Over-voltage protection
• Under-voltage protection
• Over-current (charge or discharge)
• Short-circuit detection
• Over-temperature (cells)
• Low-temperature charge cutoff
• MOSFET on/off events

Why useful:
 Helps identify abnormal usage or wiring problems.

Example entry:

2026-01-28 14:32  Discharge Overcurrent Protection

? 2. Temperature History

Some apps store min/max or timestamped values for:

• Cell temperature
• BMS temperature
• Ambient sensor temperature

Why useful:
 Confirms whether the battery has experienced extreme heat or freezing.

? 3. Voltage / Cell Imbalance Events

Logs when:

• Cell voltage exceeds limits
• Cell delta (difference between cells) becomes too large
• Balancing starts or stops

Why useful:
 Early indicator of cell aging or imbalance.

? 4. Charge / Discharge Status Changes

Tracks transitions such as:

• Started charging
• Charging completed
• Started discharging
• Load removed

Why useful:
 Shows real-world duty cycles and usage patterns.

? 5. Power Cycles & Resets

Logs when:

• Battery is powered on/off
• BMS resets
• Bluetooth module reconnects

Why useful:
 Helps troubleshoot intermittent issues.

? 6. Timestamped History (If RTC Supported)

Higher-end BMS units store:

• Date & time
• Event type
• Event code

Lower-end BMS units may store only:

• Event sequence number
• Event type (no timestamp)

? 7. Cycle Count Snapshots (Sometimes)

Some logs include when a cycle count increments or reaches certain thresholds.

Why useful:
 Confirms approximate battery aging.

What Log History is NOT

• It is not a continuous data recorder (not second-by-second graphs).
• It usually stores events, not full waveforms.
• Storage depth is limited (often last 50–500 events).

Why Manufacturers Use It

• Warranty evaluation
• Failure root-cause analysis
• Verifying misuse (overcurrent, freezing charge, etc.)

Practical Example Use Case

Customer says: “Battery suddenly stopped working.”
 You check Log History and see:

• Repeated Low-temperature charge protection
   → Root cause: charging below freezing, not battery defect.

Summary

The Log History function shows:

✔ Protection triggers
 ✔ Temperature excursions
 ✔ Voltage anomalies
 ✔ Usage transitions

It’s one of the most valuable diagnostic tools inside a Bluetooth BMS app.

If you can tell me which Bluetooth app or BMS model you’re using (Xiaoxiang/JBD, Daly, ANT, etc.), I can explain the exact log fields you’ll see and how to interpret each one.