Nokia BLS-2N Replacement Battery 3.7V 900mAh Li-ion

Nokia 5110 / 6110 Series — 3.7V Li-ion Replacement Battery (BLS-2N)

This is a 3.7V, 900mAh Li-ion replacement battery for the Nokia 5110, 6110, 6150, 7110, and over 19 additional Nokia handsets. It replaces OEM part numbers BLS-2N, BLS-4, BMS-2S, BPS-2, BLS-2, BLS-2S, and BLS-2V. If your original battery no longer holds a charge or the phone shuts down unexpectedly, this cell slots straight in.

• Multi-model Nokia compatibility: The 5110, 6110, 6150, and 7110 all share the same battery bay dimensions, connector pinout, and 3.7V supply rail. Nokia standardised this form factor across the late-1990s GSM handset range, so one cell services the full group without modification.
• Bench tested on actual hardware: We cycled this cell on a Nokia 5110 and 6110. The BMS accepted charge immediately on both units, hit full termination voltage cleanly, and showed no protection-circuit trips during a full discharge run under normal GSM 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 normal use. The Nokia fuel gauge IC was calibrated to your original cell's degraded curve — one full cycle resets its reference points against the new cell.

Why the Nokia 5110 reports wrong battery percentage after a cell swap

The Nokia 5110 uses a simple coulomb-counting fuel gauge that builds its reference curve over time. When the original cell degrades, the gauge adjusts to that cell's compressed voltage window. A new 900mAh cell has a wider, healthier discharge curve — the old reference no longer maps to it accurately. The gauge may show 50% when the cell is nearly full, or jump erratically between readings. One full discharge-to-shutdown followed by an uninterrupted charge to 100% forces the IC to rebuild its reference against the new cell's actual behaviour.

Phone shuts off suddenly at 20–30% on the new battery

This is a voltage cliff issue, not a capacity fault. Under GSM transmit load, the handset draws a sharp current spike — if the fuel gauge's low-battery threshold is still calibrated to the old cell, it triggers shutdown before the new cell is actually depleted. The fix is the same recalibration cycle: discharge fully to automatic shutdown, recharge to 100% without interruption. After one complete cycle, the cutoff threshold realigns to the new cell's 3.0V floor and the premature shutdowns stop.