Vodafone 702NK Replacement Battery NKBF01 3.7V 750mAh

Vodafone 702NK Series — 3.7V Li-ion Replacement Battery (NKBF01)

This is a 3.7V, 750mAh Li-ion replacement battery for the Vodafone 702NK, 702NKII, and V804NK smartphones. It uses OEM part number NKBF01 and matches the original cell's dimensions at 53.00 × 33.90 × 5.70mm. It is a direct swap for a degraded or failed original cell.

• 702NK, 702NKII, and V804NK compatibility: These three models share the same battery bay geometry, connector pinout, and 3.7V nominal voltage rail. The BMS handshake protocol is identical across the series, so one cell covers all three.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the 702NK platform. The BMS accepted the cell without fault flags, held cutoff at the correct low-voltage threshold, and showed no thermal anomaly during a full charge cycle.
• Fuel gauge recalibration after cell swap: On first use, disable any fast-charge mode and run one complete discharge-to-charge cycle. This lets the phone's fuel gauge IC map its coulomb counter against the new cell's discharge curve before high-current charging begins on an uncalibrated cell.

Sudden shutdown at 20–30% on the 702NK after a cell replacement

This happens because the fuel gauge IC still holds the discharge curve from the old, degraded cell. A fresh cell has a steeper voltage cliff at low state-of-charge than a worn cell does. The phone's software reads the voltage drop as a critical low and forces shutdown — even though capacity remains. One full discharge-charge cycle rewrites the curve the IC uses, and the shutdowns stop.

Phone feels warm near the battery bay during the first charge cycle

A new cell starts with higher internal impedance than a broken-in one. The charge IC pushes current into that impedance, and some energy dissipates as heat. This is most noticeable on the first cycle and reduces significantly by the second or third charge. If the phone exceeds warm-to-touch or the charge IC throws an error, pull the charger and let the cell rest at room temperature before retrying at 3.9V or above.