BLD-3 Nokia 7250i Replacement Battery 3.7V 1000mAh

Nokia 7250i / 7210 / 6610 Series — 3.7V Li-ion Replacement Battery (BLD-3)

This is a 3.7V, 1000mAh Li-ion cell built to the BLD-3 specification. It fits the Nokia 7250i, 7210, 6610, and 6560, along with eleven additional Nokia models that share the same connector and voltage rail. When the original cell degrades and no longer holds a charge, this battery restores full operation to those devices.

• Multi-model BLD-3 platform: The 7250i, 7210, 6610, and 6560 all draw from the same 3.7V rail and use the same physical connector and BMS handshake protocol, which is why a single BLD-3 cell covers the full range. Voltage tolerance and contact spacing are matched across every supported model.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on Nokia BLD-3 compatible hardware. The BMS accepted the charge curve without fault flags, and cell voltage held stable under simulated display and cellular radio load.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge down to auto-shutdown, then charge uninterrupted to 100% before using the phone normally. The Nokia fuel gauge IC was calibrated against the old cell's discharge curve — one full cycle writes new reference points and stops erratic percentage readings.

Why the Nokia 7250i reports wrong battery percentage after a cell swap

Nokia's fuel gauge IC stores a discharge curve from the previous cell in non-volatile memory. When a new cell goes in, the IC reads voltage against that old curve and outputs an inaccurate state-of-charge figure. This shows up as the percentage jumping around or stalling at a fixed number for long periods. One complete discharge-to-shutdown followed by a full uninterrupted charge forces the IC to build a new reference curve against the actual cell. After that cycle, percentage readings track correctly.

Sudden shutdown at 20–30% on the replacement cell

The Nokia 7250i's modem and backlight create short, sharp current spikes that push the cell voltage below the BMS cutoff threshold — even when the fuel gauge still shows charge remaining. A new cell with a slightly higher internal impedance than the original is more vulnerable to this voltage sag. The BMS reads the momentary voltage drop as a depleted cell and trips a protective shutdown. Running one full discharge cycle lowers the cell's impedance slightly as the electrolyte settles, and the fuel gauge recalibrates its low-voltage cutoff reference to 3.2V — the correct floor for this chemistry.