Navcom PASSY 7.4V Replacement Battery 3400mAh Li-ion

Navcom PASSY / RT-3010S / SF-3040 / Ultra RTK — 7.4V Li-ion Replacement Battery

This is a 7.4V, 3400mAh Li-ion replacement battery for the Navcom PASSY, RT-3010S, SF-3040, and Ultra RTK handheld GPS and positioning units. These are professional survey instruments used in land surveying, construction stakeout, and RTK positioning work. Swap this pack when the original no longer holds charge through a full field session.

• PASSY, RT-3010S, SF-3040, Ultra RTK compatibility: These four Navcom models share the same 7.4V two-cell Li-ion pack form factor, connector pinout, and BMS handshake protocol. A single replacement covers all four without modification.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the bench, confirmed BMS communication with the host instrument, and verified that the protection circuit trips correctly on overcurrent and low-voltage cutoff events.
• Post-install calibration on the PASSY: After fitting a new pack, run a full calibration cycle through the instrument menu before heading into the field. The PASSY maps battery state during calibration. Skip this step and the unit will throw premature low-battery warnings during your first measurement session.

BMS cutoff when the PASSY initialises its GPS and RTK modules at power-up

At cold power-on, the PASSY spins up its GPS receiver, RTK modem, and internal data logger almost simultaneously. That initialisation sequence draws a short but sharp current spike — often 1.5A to 2A above steady-state operating draw. A degraded or deeply discharged original pack can trip the BMS protection circuit at exactly this moment, shutting the unit down before the home screen loads. This replacement pack's cells sustain the inrush without triggering the overcurrent threshold. If the issue persists after fitting, check that the battery contacts on the instrument are clean and making full contact.

Battery percentage jumping erratically on the PASSY display after a pack swap

New cells have a slightly different discharge curve than the aged pack the instrument calibrated against. The PASSY's voltage-threshold indicator reads that curve as inconsistent until it recalibrates to the new cells. You'll see the percentage jump — sometimes 20 to 30 points — between readings in the first one or two charge cycles. Run two full charge and discharge cycles and the indicator stabilises. If the display still shows erratic readings after two cycles, check the instrument firmware version and update if a release is available.