Nokia BL-5S 2330 Replacement Battery 3.7V 900mAh

Nokia 2330 / 2330 Classic — 3.7V Li-ion Replacement Battery (BL-5S)

This is a 3.7V, 900mAh Li-ion cell built to the BL-5S specification for the Nokia 2330 and 2330 Classic. Both are compact candybar phones from the mid-2000s that share the same battery bay dimensions and connector. The original BL-5S degrades over charge cycles, and this unit replaces it directly at the same voltage and capacity rating.

• 2330 and 2330 Classic compatibility: Both models use the identical BL-5S form factor — same 49.99 × 37.93 × 5.27mm footprint, same three-contact connector, same 3.7V nominal rail. No adapter or modification needed to fit either variant.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge runs on the 2330 platform. The BMS held the charge cutoff correctly at 4.2V and the low-voltage protection tripped cleanly before the cell dropped below 3.0V under load.
• Fuel gauge recalibration on first use: After installing this cell, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before normal use. The phone's fuel gauge IC was calibrated to the old cell's discharge curve and needs a full cycle against the new cell to report percentage accurately.

Why the 2330 reports wrong battery percentage after a cell swap

The Nokia 2330 tracks charge state using a simple fuel gauge IC that builds its percentage model from historical discharge data on the previous cell. When you install a fresh BL-5S, that stored curve no longer matches the new cell's actual voltage-to-capacity relationship. The phone may show 50% and shut down moments later, or sit at 100% long after it should have dropped. One full discharge-to-shutdown followed by a complete uninterrupted charge resets the reference points the gauge uses. After that cycle, percentage readings stabilise.

Sudden shutdown at 15–25% on the replacement cell

This happens when the cell voltage drops sharply under the load of an outgoing call or backlight activation — a voltage cliff the fuel gauge doesn't anticipate. The phone's protection circuit reads the sag as a critical low-voltage event and cuts power before the displayed percentage reaches zero. It is not a fault with the cell itself; it is the gauge firing on a voltage threshold rather than a capacity threshold. Charge the phone to 100%, then let it discharge naturally through normal use for two full cycles — by the second cycle the gauge IC has enough data to predict the sag and the shutdowns stop.