Globalstar BT-338 Replacement Battery 3.7V 1800mAh Li-ion

Globalstar BT-338 Series — 3.7V Li-ion Replacement Battery (NTA2236)

This 3.7V 1800mAh Li-ion cell replaces the original NTA2236 battery in the Globalstar BT-338, BT-318, BT-318X, and BT-335 satellite communicators. These devices provide two-way messaging and emergency SOS via satellite in areas with no cellular coverage. Fit this cell when your unit no longer holds a charge through a full day of off-grid use.

• BT-338 / BT-318 / BT-318X / BT-335 compatibility: All four models run the same 3.7V power rail and use the same NTA2236 cell format with a matching connector and BMS handshake, so one cell covers the full group.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a BT-338 unit. The BMS accepted the cell without fault flags, and the protection circuit tripped correctly at the low-voltage cutoff threshold.
• Cold-start satellite acquisition after swap: After fitting this cell, power the unit on outdoors before your trip and let it acquire a full satellite fix. A cold start after complete power removal takes 5–10 minutes for first lock — far longer than the under-one-minute warm starts the device normally performs.

Voltage-threshold indicator drift on the BT-338 after cell replacement

The BT-338 calibrates its fuel gauge against the original cell's discharge curve. A new cell can cause the indicator to read differently until the unit completes one or two full charge-discharge cycles. During this period the battery percentage shown on screen may not match actual remaining capacity. Run the unit down to auto-shutoff and then charge it fully twice to let the gauge recalibrate against the new cell's curve.

BT-338 shuts off without a low-battery warning

This happens when the fuel gauge threshold is uncalibrated and the cell voltage drops to the BMS cutoff — around 3.0V — before the device registers a low-battery alert. The unit sees enough voltage to run, then hits cutoff abruptly. It is not a fault with the cell itself. Complete two full charge-discharge cycles so the device can re-anchor its shutoff warning to the correct voltage point on the new cell's discharge curve.