Garmin Nuvi 2639LMT Compatible Battery 3.7V 1500mAh

Garmin Nuvi 2639LMT / 2689LMT — 3.7V Li-ion Replacement Battery (KI22BI31DI4G1)

This is a 3.7V, 1500mAh Li-ion cell for the Garmin Nuvi 2639LMT, 2639LMT 6-inch, 2689LMT, and 2689LMT 6-inch portable GPS navigators. It replaces OEM part KI22BI31DI4G1 and fits the same battery bay without modification. Swap it when the original cell no longer holds enough charge to support untethered navigation.

• Nuvi 2639LMT and 2689LMT platform fit: Both the 2639LMT and 2689LMT use the same 3.7V battery rail, connector pinout, and BMS handshake. The 6-inch display variants share the same internal battery bay dimensions — 64.42 × 41.90 × 5.10mm — so one cell covers the full cluster.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Nuvi platform. The BMS communicated correctly with the device, accepted a full charge without fault flags, and held the correct voltage under GPS receiver and display load.
• First fix after swap: After fitting this cell, power the unit on outdoors and let it acquire a satellite fix before driving. A full power interruption forces a cold start — first fix takes 5–10 minutes. Subsequent warm starts drop back under a minute once the almanac data is cached again.

GPS accuracy reduced at low battery on the Nuvi 2639LMT

As cell voltage drops toward the lower cutoff threshold, the Nuvi reduces power to the GPS receiver to extend operation. Lower receiver sensitivity means weaker satellite signals get dropped from the fix calculation. Position accuracy degrades — you may see the blue dot drift or jump between streets. Keeping the cell above 3.5V under load prevents the receiver from stepping down.

Nuvi 2639LMT shutting off without warning during navigation

An aged or deeply discharged cell loses capacity unevenly — the battery indicator reads 20–30% but voltage collapses under the combined load of the GPS receiver and backlit display. The device hits its hardware cutoff threshold before the visual warning fires. This is a calibration gap: the indicator was mapped to the original cell's discharge curve. After fitting the new cell, run two full charge-discharge cycles on the device to allow the indicator to re-map to the new cell's curve.