Nokia BL-5B 5300 XpressMusic Replacement Battery 3.7V 900mAh

Nokia 5300 XpressMusic — 3.7V Li-ion Replacement Battery (BL-5B)

This is a 3.7V, 900mAh Li-ion cell built to the BL-5B specification. It fits the Nokia 5300 XpressMusic along with a wide range of Nokia candybar phones from the same generation, including the 2610, 3220, and 3230. Physical dimensions are 46.20 × 34.14 × 5.68mm — same footprint as the original cell.

• Multi-model BL-5B platform: Nokia standardised the BL-5B across over two dozen models in this era. All share the same three-contact connector layout and 3.7V nominal voltage rail, so one cell spec covers the full range without any adaptation.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a 5300 XpressMusic. The BMS accepted charge without cutoff interruption, and the protection circuit responded correctly at low-voltage threshold — no false trips during normal load.
• Fuel gauge recalibration after swap: On first use, run the phone from a full charge down to automatic shutdown without interrupting the discharge. This gives the fuel gauge IC one complete reference cycle against the new cell's discharge curve before you rely on the percentage readout.

Why the 5300 XpressMusic reports wrong battery percentage after a cell swap

The 5300 uses a simple coulomb-counting fuel gauge that was calibrated against the original cell's discharge profile over many cycles. When you fit a new cell, that stored profile no longer matches the actual voltage-to-capacity curve of the fresh Li-ion. The phone reads voltage and maps it to a percentage using the old data, so the number displayed can be several points off — especially in the 40–70% range. One full uninterrupted discharge followed by a complete charge resets the reference points the gauge uses. After that cycle, percentage tracking tightens up noticeably.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — a behaviour called a voltage cliff. At around 20–30% state of charge, a Li-ion cell's internal resistance rises enough that driving the backlight or audio amplifier on the 5300 causes a sudden voltage sag below the BMS cutoff threshold, typically around 3.0V per cell. The phone sees an undervoltage event and shuts down even though the fuel gauge still shows charge remaining. Let the phone cool for two minutes, then power it back on — if it boots and immediately shows a low battery warning, the cell is discharging normally. Avoid letting charge drop below 15% until the fuel gauge completes its first full calibration cycle.