Troubleshooting¶
LED blinks red continuously (5 Hz)
- Over-voltage or over-current fault detected
- Check power source specifications
- Verify battery connections
LED blinks red continuously (2 Hz) during OTG
- Battery voltage too low for discharging
- Recharge the battery
Charging doesn't start
- Check that power source supports USB PD, QC, or BC1.2
- Ensure KX2 is powered off (if charging while on is disabled)
OTG mode doesn't work
- Ensure battery voltage is above the discharge limit (default 9.0 V)
- Try disconnecting and reconnecting the device
- Check that the connected device can accept USB-C power input
Battery voltage not showing in KX2 menu
- Set "KXIBC2" option to "NOR" in KX2 configuration menu
QRM concerns
- QRM is minimal (typically S1 noise floor increase)
- No QRM when USB/DC is disconnected
- Charging is automatically disabled when KX2 is on (by default)
- Can be enabled in configuration if needed
Technical specifications¶
| Charger IC | BQ25792 buck-boost converter |
| USB-C controller | FUSB302B |
| Microcontroller | ATtiny3226 |
| Switching frequency | 1.5 MHz |
| Standby current | ~60 µA |
| Supported protocols | USB PD 3.0, QC, BC1.2 |
| Battery types | 3S Li-Ion (default), 4S LiFePO₄ (with configuration) |
Safety notes¶
Use at your own risk
- Always use batteries with built-in protection and balancing circuits
- The KXUSBC2 is an unofficial modification and may void your KX2 warranty
- Ensure proper grounding through the side panel mounting