AMOI MOS-1 Replacement Battery 3.7V 1000mAh Li-ion

AMOI MOS-1 — 3.7V Li-ion Replacement Battery (MOS-1)

This is a 3.7V Li-ion cell rated at 1000mAh (3.7Wh), built to fit the AMOI MOS-1 smartphone. It replaces the original battery when the existing cell no longer holds a charge or causes unexpected shutdowns. Physical dimensions are 42.00 × 71.00 × 7.00mm — confirm these against your existing cell before installing.

• AMOI MOS-1 fitment: The MOS-1 battery compartment uses a fixed connector and BMS handshake tied to this cell's voltage profile. A cell outside this voltage and form factor range will either fail to register or trigger a protection cutoff on first boot.
• Bench tested on actual hardware: We ran charge and discharge cycles through this cell and monitored the BMS response at low state-of-charge. The protection circuit engages cleanly at the undervoltage threshold — no false cutoffs above 3.0V per cell were recorded.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before any high-current charging session pushes current into an uncalibrated state.

Why the MOS-1 reports wrong battery percentage after a cell swap

The fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, the IC still references that old curve — so displayed percentage drifts against actual voltage. The fix is one full uninterrupted discharge down to auto-shutdown, followed by a full charge with the screen off. After that single cycle, the coulomb counter re-anchors to the new cell's real capacity and percentage accuracy returns.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the modem or display load threshold faster than the fuel gauge anticipates — a voltage cliff the IC hasn't yet mapped. The phone reads 25% but the cell is already sagging below 3.4V under the combined draw of the radio and screen backlight. Run one full calibration cycle first: discharge to zero, charge uninterrupted to 100%. If shutdowns persist after that, check that resting cell voltage reads at least 3.6V with a multimeter before reinserting.