Rand McNally TND-70 GPS Compatible Battery 3.7V 3500mAh

Rand McNally TND-70 — 3.7V Li-Polymer Replacement Battery (MLP604582)

This 3.7V, 3500mAh lithium-polymer cell replaces the original MLP604582 battery in the Rand McNally TND-70 GPS navigator. The TND-70 is a truck-focused navigation device with real-time traffic and route planning. Fitting this cell restores full power to the display, GPS receiver, and onboard storage.

• TND-70 compatibility: The TND-70 uses a single-cell Li-Polymer pack at 3.7V nominal. This replacement matches that voltage rail and the MLP604582 form factor — 83.00 × 44.80 × 5.70mm — so the cell seats correctly against the connector without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the TND-70 platform. The BMS accepted the cell without fault codes, charge termination triggered cleanly at 4.2V, and the low-voltage cutoff held at the expected threshold before shutdown.
• Cold-start satellite acquisition after fitting: After a full power interruption, the TND-70 loses its ephemeris data and must perform a cold start. Power the unit on outdoors in open sky and leave it stationary — first satellite fix typically takes 5 to 10 minutes. Subsequent warm starts drop to under a minute once the almanac rebuilds.

Why the TND-70 shuts off without showing a low-battery warning

The TND-70 reads battery state from a voltage curve calibrated to the original cell. When a degraded original battery is replaced, the fuel gauge has no reference point and may misread state-of-charge by a wide margin. The device hits its hardware cutoff voltage — around 3.0V — before the on-screen indicator reaches the empty icon. Running two full charge-discharge cycles recalibrates the curve and brings the warning back in line with actual capacity.

Saved routes and custom POIs missing after battery replacement

The TND-70 stores user routes and points of interest in internal flash memory, not in battery-backed RAM, so a clean power removal does not erase them. If routes are missing after a swap, the more likely cause is a firmware reset triggered by the device detecting an unexpected power-on sequence. Navigate to Settings → Restore and check whether a factory reset flag was set during the power interruption. Re-importing routes from a saved backup file on the SD card or via the Rand McNally Dock software is the fastest recovery path.