About this replacement
Olympia Touch 2179 — 3.7V Li-ion Replacement Battery (MT423856)
This is a 3.7V, 1050mAh Li-ion replacement battery for the Olympia Touch (model 2179), using OEM part number MT423856. It fits directly into the battery bay of that handset and restores power to units where the original cell has aged or swollen. Voltage and capacity match factory spec.
- Touch 2179 fitment: The MT423856 cell is specific to the Olympia Touch 2179 form factor — the 60.00 × 38.12 × 4.60 mm footprint and connector orientation are matched to that handset's battery bay. Fitting a cell with different dimensions risks connector stress or case clearance issues.
- Bench tested on actual hardware: We ran charge and discharge cycles on this cell and confirmed the BMS communicates correctly with the charge IC, accepts a full charge without early termination, and holds voltage above the low-battery cutoff threshold under screen and modem load.
- Fuel gauge recalibration after install: On first use after fitting this cell, disable fast charging and complete one full discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before reporting state of charge — skipping this step causes erratic percentage readings early on.
Why the Olympia Touch reports wrong battery percentage after a cell swap
The fuel gauge IC on the Touch 2179 builds a model of cell capacity using coulomb counting calibrated to the original cell's charge curve. When a new cell goes in, that stored model no longer matches the actual cell chemistry. The IC reports percentage against outdated reference data, so the number on screen drifts from real charge state. One complete slow-charge cycle — charge to 100%, drain to cutoff, charge again without fast charge enabled — forces the IC to rebuild the curve against the new cell. After that cycle, percentage accuracy normalises.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops sharply under combined screen and modem load — a voltage cliff the fuel gauge IC didn't predict, because its curve was calibrated to the old cell. The phone's protection circuit reads voltage below the safe floor and shuts down immediately, even though the displayed percentage looked safe. The fix is the same recalibration cycle: one full discharge at standard load with fast charging off, then a full slow charge. After calibration, the IC anticipates the cliff and the 20–30% shutdown stops.