Topcon BT-30 Field Controller Replacement Battery 7.4V 2600mAh

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

This 7.4V, 2600mAh Li-ion battery replaces the Topcon BT-30 and fits the FC100 and FC2000 field controllers. These are rugged handheld data collectors used with GPS receivers and robotic total stations on active survey sites. Voltage and cell chemistry match OEM spec — the BMS on both controllers will recognise the pack without prompting firmware errors.

• FC100 and FC2000 compatibility: Both controllers share the same 7.4V battery bay, connector pinout, and BMS handshake protocol. A single pack covers either unit, which matters when a crew runs both devices from the same kit bag.
• Bench tested on actual hardware: We ran this pack through the FC100's power-up sequence, including GPS module initialisation and Bluetooth link-up to a robotic total station. The BMS held steady through the combined startup draw and did not trip a protection cutoff.
• Pre-deployment calibration cycle: After fitting a new pack, run a full calibration cycle through the FC100's instrument menu before heading into the field. The controller maps battery state during that cycle — skip it and the low-battery warning will fire too early on your first measurement session, even with a full charge.

BMS lockout after the FC100 sat unused in a carry case for months

Li-ion cells self-discharge during storage. If the pack voltage drops below roughly 2.5V per cell, the BMS trips an over-discharge protection latch and the controller will show no charge activity when you plug in. The fix is a slow-charge recovery — connect the pack to the OEM charger or a compatible Li-ion charger with a recovery mode and leave it for at least 30 minutes before expecting normal charge behaviour. Once cell voltage climbs back above the BMS recovery threshold (typically around 3.0V per cell), the latch resets and charging resumes normally.

FC100 cutting out during active GPS logging or data transfer to PC

The FC100 draws more current when the GPS module is actively logging fixes and simultaneously writing data over USB to a connected PC. Aged or degraded cells show higher internal resistance, which causes a brief voltage sag under that combined load — enough to cross the controller's under-voltage cutoff threshold. The unit shuts down cleanly rather than risk corrupted data, so the shutdown itself is normal protection behaviour. If a new pack resolves it, the old cells had degraded past their usable capacity even if the fuel gauge was still reading mid-range.