Sagem MY-X5 Replacement Battery 3.7V 1000mAh 188973731

Sagem MY-X5 / MY-X3 — 3.7V Li-ion Replacement Battery (188973731)

This 3.7V 1000mAh Li-ion cell replaces the original battery in the Sagem MY-X5 and MY-X3 flip phones. It matches OEM part numbers 188973731, SA-SNX, and 251165224. Dimensions are 56.28 × 36.59 × 5.51mm — verify your tray before ordering.

• MY-X5 and MY-X3 platform fit: Both models share the same battery tray geometry, connector pin-out, and 3.7V single-cell architecture. One cell covers the full X3/X5 line without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the MY-X5 chassis. The BMS accepted the charge IC handshake cleanly on the first cycle and held cutoff voltage correctly at both ends of the curve.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge down to auto-shutdown, then charge uninterrupted to 100%. The phone's fuel gauge IC calibrated to the old cell's discharge curve — it needs one full cycle against the new cell before percentage readings stabilise.

Sudden shutdown at 20–30% on the MY-X5 after a cell swap

A fresh Li-ion cell has a steeper voltage cliff near end-of-charge than a worn cell. The MY-X5's fuel gauge IC still carries the old discharge curve in memory, so it misjudges how much charge remains. When the modem fires during a call or the backlight peaks, current draw pulls the cell below the BMS cutoff threshold before the gauge hits zero. The fix is a single full discharge-to-shutdown followed by an uninterrupted charge — after that cycle, the gauge tracks the new curve accurately.

MY-X5 not powering on after sitting in storage

Li-ion cells that self-discharge below approximately 2.5V trigger a BMS lockout to prevent cell damage. The MY-X5 will show nothing on screen — no charge indicator, no vibration — because the BMS is blocking current to the phone entirely. Connect the charger and leave it for 15–20 minutes without pressing any button; the charge IC applies a trickle current that brings the cell above the BMS re-enable threshold. Once the screen shows a charging icon, the BMS has released and normal charging resumes.