For the Xiaomi Redmi 14C, if you're looking for a battery supporting fast charging with a large capacity, you would need to look for a compatible replacement battery that fits the specific model of the phone.

The BN5X battery you mentioned is likely referring to a standard battery model that supports certain charging capabilities. However, for a phone like the Redmi 14C, Xiaomi typically uses batteries specifically designed for their devices with certain voltage and charging speed ratings.

Here are some key factors to consider when looking for a battery replacement:

1. Battery Capacity: The Redmi 14C likely comes with a battery around 5000mAh, but you can opt for one with a larger capacity if available, provided it fits.

2. Fast Charging Support: Xiaomi phones, especially newer models, generally support 18W fast charging or higher. Make sure the battery you are considering supports fast charging (and that your charger supports the same charging standard).

3. Compatibility: Ensure the replacement battery is compatible with the Redmi 14C. This includes physical dimensions, battery type (Li-Po, Li-Ion, etc.), and voltage requirements.