Swissvoice MP03 Replacement Battery 3.7V 1050mAh

Swissvoice MP03 / MP22 / MP33 / BBM320 — 3.7V Li-ion Replacement Battery

This 3.7V 1050mAh Li-ion cell replaces the original battery in the Swissvoice MP03, MP22, MP33, and BBM320 mobile phones. It matches the stock voltage and capacity of the factory cell. Install it when the original no longer holds charge through a normal day.

• MP03 / MP22 / MP33 / BBM320 platform fit: These four Swissvoice handsets share the same battery bay dimensions (53.00 × 33.90 × 5.60mm), 3.7V nominal voltage rail, and connector pinout — which is why one cell covers the full set. No modification needed.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS held the correct 4.2V charge ceiling, and the protection circuit tripped cleanly at the low-voltage cutoff without latching — so the phone could recover normally.
• Fuel gauge recalibration after installation: On first use, run one full discharge down to automatic shutoff, then charge uninterrupted to 100% before normal use. The MP03's fuel gauge IC is calibrated to the old cell's discharge curve — one complete cycle resets the coulomb counter against the new cell and removes erratic percentage readings from the start.

Sudden shutdown at 20–30% on the Swissvoice MP03

The MP03 shuts off abruptly at 20–30% when the fuel gauge IC is still mapped to the old cell's discharge curve. The new cell has a slightly different internal impedance profile, so the IC misjudges the remaining voltage headroom under modem or screen load. At peak draw, the cell voltage briefly dips below the BMS cutoff threshold — the phone interprets this as a dead battery and cuts power. One full discharge-to-shutoff followed by an uninterrupted charge to 4.2V corrects the counter mapping and stops the premature shutdowns.

Phone feels warm near the battery on the first few charges

A fresh Li-ion cell has higher internal impedance than a broken-in cell. During the first one to three charge cycles, the charge IC pushes current into that higher-impedance cell, and some energy dissipates as heat rather than stored charge. This is normal and tapers off as the cell's impedance drops with cycling. If warmth persists beyond three full cycles or becomes hot to the touch, check that the phone's charge IC is not stuck in a high-current fast-charge mode — disabling fast charge for the first cycle keeps current demand in the 0.5C range where heat generation stays low.