Nokia BL-4B Replacement Battery 3.7V 700mAh Li-ion

Nokia 6111 / 7370 / 7373 Series — 3.7V Li-ion Replacement Battery (BL-4B)

This is a 3.7V, 700mAh Li-ion replacement battery for Nokia phones using the BL-4B or BL-4BA cell. It fits the 6111, 7370, 7360, 7373, and over a dozen additional models that share the same connector and form factor. Dimensions are 46.50 × 34.30 × 5.20mm — matching the original slot geometry.

• Multi-model fit — 6111, 7370, 7360, 7373 and more: All BL-4B and BL-4BA devices share the same voltage rail, physical footprint, and contact pinout. No adapter or modification needed — the connector seats the same way across the entire lineup.
• Bench tested on actual hardware: We cycled this cell on a Nokia 6111 unit. The BMS accepted the charge handshake on the first connection, held voltage above 3.5V through a full discharge, and showed no false-cutoff events before depletion.
• Fuel gauge recalibration on first use: After installation, let the phone discharge fully to auto-off, then charge uninterrupted to 100% before normal use. The fuel gauge IC on these Nokia models calibrates its coulomb counter against the first complete discharge curve — skipping this step causes the percentage to jump or read inaccurately for the first several days.

Why the Nokia 6111 reports wrong battery percentage after a cell swap

The 6111 uses a simple fuel gauge IC that stores a discharge curve from the previous cell. When a new cell goes in, the IC is still reading against the old curve — so the percentage it shows does not match the actual state of charge in the new cell. This mismatch shrinks after one or two full discharge-charge cycles as the IC rewrites its reference data. Until that recalibration completes, readings between 20% and 80% are the least accurate. Run two full cycles after installation and the gauge stabilises.

Sudden shutdown at 20–30% remaining on the new cell

This happens when the phone's modem or backlight pulls a brief current spike and the cell voltage dips below the BMS cutoff threshold — even though the gauge still shows charge remaining. A 700mAh cell at this voltage cliff cannot sustain the instantaneous load, so the BMS trips and the phone powers off. The fix is not a new battery — it is recalibration. Let the phone reach true zero (auto-off under load), then charge to 100% without interruption. After two full cycles the shutdown threshold and the gauge reading align, and the premature cutoff stops.