Not Charging Reason¶

The "Not Charging Reason" is a diagnostic value that explains why your device is not charging when a charger is connected. This information is read from the Apple SMC (System Management Controller) and helps identify the root cause of charging issues.

Overview¶

The Not Charging Reason is stored in the SMC key CHNC (Charger Not Charging) and can have different formats depending on your device's generation:

• Version 0 (NonSMC): Legacy devices without SMC support
• Version 1 (Gibraltar/BNCR): Enum-based format used on specific Intel Mac models
• Version 2 (SMC/CHNC): Bitmask-based format used on Apple Silicon and most modern devices

The version is determined by reading the RGEN (Reason Generation) SMC key.

Version 2 (SMC/CHNC) - Modern Devices¶

Version 2 uses a bitmask format where multiple reasons can be active simultaneously. This is the format used on Apple Silicon Macs and most modern devices as of 2025.

Common Reasons¶

Presence Issues¶

Charging Inhibit Conditions¶

System Modes¶

Charging Control¶

System Controls¶

Permanent Faults¶

These indicate serious hardware or firmware issues that may require service:

When any permanent fault is detected, the system may display "Permanent Battery Failure" as the primary reason.

Version 1 (Gibraltar/BNCR) - Intel Mac Models¶

Version 1 uses an enum-based format where only one reason is active at a time. This format is used on specific Intel Mac models:

• J132, J137, J140, J152, J213, J214, J215, J680, J780

Common Reasons¶

Version 0 (NonSMC) - Legacy Devices¶

Version 0 is used on very old devices that don't have SMC support. Known devices include:

• D10, D11
• J71, J72, J73, J81, J82, J85, J86, J87, J96, J97, J98, J99, J120, J121, J127, J128, J171, J172, J207, J208
• N27, N28, N61, N66, N69, N71, N74, N75, N111, N121

NonSMC Specific Reasons¶

Interpreting the Value¶

The Not Charging Reason is typically displayed as a hexadecimal value (e.g., 0x00000001). In Version 2 (bitmask format), multiple bits can be set simultaneously, indicating multiple reasons.

Example Interpretations¶

• 0x00000001 - Fully Charged
• 0x00000002 - Too Cold
• 0x00000004 - Too Hot
• 0x00000003 - Fully Charged AND Too Cold (both bits set)

Troubleshooting Tips¶

1. Temperature Issues: If you see "Too Cold" or "Too Hot" reasons, allow the device to reach a normal operating temperature (typically 0-35°C).

2. Predictive Charging: If "Predictive Charging" is shown, this is normal behavior. The system is learning your usage patterns to optimize battery health.

3. Firmware Updates: "Gas Gauge FW Updating" is temporary and should resolve once the update completes.

4. Permanent Faults: If you see any permanent fault reasons, the battery or charging system may need service.

5. Multiple Reasons: In Version 2, multiple reasons can be active. Check all listed reasons to understand the complete charging state.

Technical Notes¶

• The Not Charging Reason is read from SMC key CHNC (8 bytes on most devices, 64 bytes on mobile devices)
• The generation/version is determined by SMC key RGEN