Fuji TK7N6384 Survey Battery 7.4V 2200mAh Li-ion

Fuji Electric Systems — 7.4V Li-ion Replacement Battery (TK7N6384)

This 7.4V 2200mAh (16.28Wh) Li-ion battery replaces the OEM TK7N6384 pack used in Fuji Electric portable survey and test instruments. It fits equipment used in field diagnostics and measurement work. Voltage and capacity match the original specification exactly.

• Fuji Electric survey and test platform fit: These instruments share a common 7.4V dual-cell architecture with a matched BMS handshake. The connector pinout, cell configuration, and protection circuit all correspond to the TK7N6384 form factor, so the instrument's power management system reads the pack correctly on startup.
• Bench tested on actual hardware: We cycled this pack under sustained sensor load and confirmed the BMS holds voltage through probe initialisation spikes without tripping. Cell balance was verified across both charge and discharge phases before the pack ships.
• Calibration cycle after install: After fitting this battery, run a full calibration cycle through the instrument menu before field deployment. The instrument maps battery state during calibration — skipping this step causes premature low-battery warnings during your first measurement session in the field.

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

Li-ion cells in survey instruments self-discharge slowly during storage. If the pack voltage drops below approximately 2.5V per cell, the BMS enters a protection lockout state and the instrument will not power on or begin charging normally. At this point, standard charging via the instrument's dock or USB port may show no response at all. Most chargers capable of delivering a low-current pre-charge pulse — around 100mA — can bring the cells back above the 3.0V recovery threshold, after which normal charging resumes.

Instrument shuts down during USB data transfer to PC

USB data transfer adds a secondary load on top of active sensor circuits, and the combined draw can push current demand past the BMS cutoff threshold if the cells are already below 7.0V. The instrument cuts power to protect the cells, and the transfer session drops. Transfer data when the battery reads full, not partway through a workday. If shutdowns repeat, check that the USB cable is direct to the PC — unpowered hubs add impedance and increase voltage sag under load.