Magellan Thales MMCE GPS Replacement Battery 3.7V 3960mAh

Magellan Thales MMCE / MobileMapper Series — 3.7V Li-ion Replacement Battery (111141)

This 3.7V, 3960mAh Li-ion cell replaces part number 111141 in the Magellan Thales MMCE and related portable GPS navigators. It fits the Thales CX, Promark 3, Thales MobileMapper, and five additional models that share the same connector and voltage rail. Capacity is sourced from product data — 14.65Wh per cell.

• Multi-model fit across the Thales GPS platform: The MMCE, CX, Promark 3, and MobileMapper lines share a common 3.7V single-cell architecture with the same physical connector and BMS handshake protocol — one cell covers the full platform without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Thales platform unit. The BMS accepted charge from the OEM cradle without fault flags, held the voltage curve through full draw, and hit the low-voltage cutoff cleanly at the expected threshold.
• Cold-start acquisition after power interruption: After fitting this cell, power the GPS on outdoors before driving. The unit loses its ephemeris data on full power removal and performs a cold start — first satellite fix takes 5–10 minutes. Subsequent warm starts drop to under a minute once almanac data is rebuilt.

GPS accuracy reduced when battery charge drops below 20%

Several Thales-platform GPS units step down receiver sensitivity as battery voltage falls to extend operating time. This pulls in fewer satellite signals and widens the position error radius. The device may still show a fix, but accuracy degrades noticeably. Keeping charge above 20% — roughly 3.6V under load — maintains full receiver gain.

Device shuts off without a low-battery warning after fitting a new cell

The battery indicator on Thales GPS units is calibrated to the charge curve of the original cell. A new cell with a slightly different internal resistance profile can cause the fuel gauge to read incorrectly, so the unit hits its voltage cutoff threshold before the warning icon appears. Run two full charge-and-discharge cycles through the OEM cradle — this allows the gauge to re-calibrate against the actual discharge curve of the new cell.