Bluetooth BT74R GPS Receiver Compatible Battery HXE-W01 3.7V 1000mAh

Bluetooth BT74R / BT77 GPS Receiver — 3.7V Li-ion Replacement Battery (HXE-W01)

This 3.7V 1000mAh Li-ion cell replaces part number HXE-W01 in the Bluetooth BT74R and BT77 GPS receivers. Both are compact portable GPS units used for outdoor navigation and field surveying. The cell powers the receiver's GPS module, wireless stack, and onboard memory during active use and standby.

• BT74R and BT77 compatibility: Both models share the same battery bay dimensions, connector pinout, and 3.7V supply rail. The BMS on each unit reads the same charge termination voltage, so one cell works across both without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the BT74R. The BMS accepted charge without fault flags, and the voltage held within spec across the discharge curve at GPS-active load.
• Cold-start satellite acquisition after fitting: After fitting this cell and powering on, take the unit outdoors immediately. A full power interruption triggers a cold start — the receiver must re-download almanac data, which can take 5 to 10 minutes for first fix. Subsequent warm starts drop back under a minute once the almanac is cached.

GPS accuracy dropping at low battery on the BT74R

When cell voltage falls below roughly 3.5V, some GPS receivers step down receiver sensitivity to reduce current draw. On the BT74R, this shows up as position drift or reduced fix accuracy before the low-battery indicator even triggers. The GPS module draws more current than the display, so the voltage sag at the receiver is larger than the system voltage reading suggests. Keeping the cell above 3.6V during active navigation maintains full receiver sensitivity.

BT74R shutting off without warning during navigation

This happens when the fuel gauge calibration drifts after the original cell has been replaced. The device reads more remaining charge than the cell actually holds, so the low-battery warning and the cutoff threshold hit almost simultaneously. The BMS hard-cuts the circuit at around 3.0V to protect the cell. Run one full discharge to cutoff and a complete recharge after fitting — this re-anchors the gauge to the new cell's actual capacity endpoints.