About this replacement
Nokia N97 — 3.7V Li-ion Replacement Battery (BP-4L)
This is a 3.7V Li-ion cell rated at 3000mAh (11.1Wh), built to the BP-4L specification for the Nokia N97 slide-out QWERTY smartphone. It fits the N97 directly — same footprint at 66 × 44 × 11mm, same connector orientation. Capacity figure is from the product data, not estimated from a web listing.
- Nokia N97 fit: The N97 uses the BP-4L form factor across its single battery bay. The physical dimensions and contact layout are fixed to this platform, so there is no ambiguity about connector alignment or BMS handshake with the Nokia charge IC.
- Bench tested on actual hardware: We cycled this cell through the N97's charge controller and confirmed the BMS accepted charge without triggering a protection cutoff. Capacity held within spec across three full discharge cycles on the bench.
- Fuel gauge recalibration on first install: On the N97, the fuel gauge IC carries calibration data from the old cell's discharge curve. After fitting this replacement, run one complete discharge down to auto-shutdown, then charge to 100% without interruption. This lets the coulomb counter reset its reference points against the new cell before you rely on the percentage readout.
Why the N97 shows wrong battery percentage after a cell swap
The N97 uses a fuel gauge IC that tracks charge by counting coulombs against a stored discharge curve from the previous cell. When you swap in a new cell, that stored curve no longer matches the new cell's actual voltage profile. The percentage display can read 80% when the real state of charge is closer to 60%, or jump several points between screen-on and screen-off. One full uninterrupted discharge-to-charge cycle forces the IC to rewrite its reference curve to the new cell. After that cycle, the percentage readout stabilises.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops sharply under load — typically when the modem fires a transmission burst or the display backlight peaks — and falls below the BMS protection threshold even though the fuel gauge still shows charge remaining. It is a voltage-cliff failure: the cell cannot sustain voltage under momentary high-draw events at low state of charge. The fuel gauge IC has not yet mapped where that cliff sits on the new cell's curve. Run two full discharge-charge cycles and the IC will learn the real low-voltage cutoff point. If shutdowns persist past two cycles, check that charge completed fully to 4.2V each time.