Topcon BT-30 Field Controller FC100 Replacement Battery 7.4V 3400mAh

Topcon FC100 / FC2000 Field Controller — 7.4V Li-ion Replacement Battery (BT-30)

This 7.4V, 3400mAh Li-ion battery replaces the OEM BT-30, BT-62Q, BT-65Q, and BT-66Q packs used in Topcon FC100 and FC2000 Field Controllers. These handheld data collectors run GPS positioning, mapping, and real-time site measurement software in the field. Same voltage rail, same connector, same BMS handshake as the original pack.

• FC100 and FC2000 compatibility: Both controllers share the same battery bay geometry, 7.4V nominal rail, and OEM BMS communication protocol. The BT-30 form factor covers all hardware revisions of both models without modification.
• Bench tested on actual hardware: We ran this pack through a full charge and discharge cycle on an FC100 unit. The BMS correctly reported state of charge throughout, and the controller accepted the pack without a battery-fault flag at startup.
• Pre-deployment calibration cycle: After fitting this battery, run a full calibration cycle through the FC100's instrument menu before heading to site. The controller maps battery state during calibration — skipping this step causes premature low-battery warnings during your first measurement session in the field.

FC100 shutting down mid-session after months in the carry case

Li-ion cells self-discharge during storage. If an FC100 sits unused for several months, the pack voltage can drop below the BMS recovery threshold — typically around 2.5V per cell, or roughly 5.0V across the pack. At that point the BMS latches into a protective sleep state and the controller will not power on. Placing the battery on a charger that supports a trickle or recovery pre-charge mode will bring it back. Once cell voltage climbs above 3.0V per cell, the BMS exits sleep and a normal charge cycle completes.

GPS lock acquired, then FC100 resets or freezes during active data logging

Sustained sensor and radio load during active GPS logging draws significantly more current than the idle state. If the battery cells have aged or the pack has a weakened cell, voltage sags under this load and dips below the controller's cutoff threshold — triggering a mid-session reset. This is different from a BMS fault; the unit restarts rather than shutting off cleanly. Fit a fresh pack, run the calibration cycle, and check that the controller holds voltage above 7.0V during a live GPS lock session before returning to site.