Sagem OT860 Replacement Battery 3.7V 900mAh Li-ion

Sagem OT860 / OT890 — 3.7V Li-ion Replacement Battery (189950240)

This 3.7V, 900mAh Li-ion cell replaces the original battery in the Sagem OT860 and OT890 smartphones. It matches OEM part numbers 189950240, SAAM-SN0, and SAAM-SN1. The cell measures 53.00 × 34.00 × 4.80mm — verify those dimensions against your original before fitting.

• OT860 and OT890 compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol, which is why a single cell covers both. Voltage rail is 3.7V nominal across the platform.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS accepted charge current without tripping, and the protection circuit engaged correctly at low-voltage cutoff — no runaway events observed.
• Fuel gauge recalibration after fitting: On first use, run one full discharge down to automatic shutdown, then charge uninterrupted to 100% before enabling any fast-charge option. This gives the fuel gauge IC a clean reference curve against the new cell — skipping it causes erratic percentage readings for several cycles.

Sudden shutdown at 20–30% on the OT860 after a cell swap

This happens because the phone's fuel gauge IC is still calibrated to the discharge curve of the old, degraded cell. When the new cell hits a voltage point the IC associates with a safe state, it cuts power before the cell is actually empty. The modem radio drawing burst current during a call accelerates the voltage drop at that threshold. One full discharge-to-shutdown cycle followed by an uninterrupted charge resets the coulomb counter and clears the symptom.

Phone won't power on after the replacement battery sat in storage

Li-ion cells self-discharge in storage, and if the voltage drops below approximately 2.5V per cell, the BMS enters lockout mode to prevent damage. The phone will show no response — no boot screen, no charge indicator. Connect the phone to a charger and leave it for 15–20 minutes without pressing the power button; the charge IC needs time to trickle current into the cell and push voltage above the BMS re-enable threshold. Once the charge indicator appears, a normal charge cycle can begin.