Ashtech MobileMapper CX GPS Replacement Battery 3.7V 3960mAh

Ashtech MobileMapper CX GIS-GPS Receiver — 3.7V Li-ion Replacement Battery

This 3.7V Li-ion cell at 3960mAh (14.65Wh) replaces the original battery in the Ashtech MobileMapper CX GIS-GPS Receiver. The MobileMapper CX is a professional field device used for GIS data collection and surveying. It draws continuous power from the GPS receiver, display, and onboard processing — a combination that demands a full-capacity cell.

• MobileMapper CX fit: The MobileMapper CX uses a single-cell 3.7V Li-ion pack with a dedicated BMS that monitors cell voltage and temperature. This replacement matches the original cell voltage rail and physical footprint — 72.50 × 53.00 × 15.00mm — so the pack seats correctly and the BMS handshake completes on first power-on.
• Bench tested on actual hardware: We cycled this cell through charge and discharge with the BMS active. The protection circuit responded correctly to end-of-charge at 4.2V and triggered low-voltage cutoff at the expected threshold without tripping prematurely under the combined GPS and display load.
• First fix after installation: After fitting this cell, power the MobileMapper CX on outdoors and let it run a full cold-start satellite acquisition before beginning fieldwork. A cold start following complete power removal typically takes 5–10 minutes to achieve a solid fix — plan for this before your first session in the field.

Why the MobileMapper CX shuts off without a low-battery warning

The MobileMapper CX estimates remaining charge using a fuel gauge calibrated to the original cell's discharge curve. After a battery swap, that calibration is reset and the device has no reliable state-of-charge reference. It can read 30% remaining and cut off seconds later because the actual cell voltage has already crossed the BMS protection threshold. To recalibrate, run the device from a full charge down to automatic shutdown once, then charge it to 100% without interruption. After one full cycle, the fuel gauge tracks remaining capacity accurately.

GPS accuracy dropping during long field sessions

Some GPS receivers scale back receiver sensitivity as cell voltage falls below roughly 3.5V — a power-saving measure that reduces the signal processing load on the processor. On the MobileMapper CX, this can appear as position drift or a drop in satellite count late in a session rather than a clean shutdown. If you notice accuracy degrading before the battery indicator shows critical, check the raw voltage in the device diagnostics menu. Keeping the cell above 3.6V during active data collection avoids this threshold.