Fukuda FLE-444R Multiline Laser Replacement Battery 3.7V 3600mAh

Fukuda Multiline Laser Series — 3.7V Li-ion Replacement Battery (FLE-444R)

This is a 3.7V, 3600mAh Li-ion replacement battery for Fukuda multiline laser devices. It fits the FLE-444R, EK-189, EK-289, and related models used in construction leveling and surveying. Voltage and cell chemistry match the original pack specification.

• FLE-444R, EK-189, EK-289 platform fit: These models share the same 3.7V single-cell architecture, connector pinout, and BMS handshake protocol. One replacement pack covers the full group without modification.
• Bench tested on actual hardware: We ran this pack through power-on initialisation and line-projection cycles. The BMS held stable across repeated sensor activation events and showed no nuisance cutoffs during sustained laser output.
• First-use calibration on Fukuda multiline lasers: After installing this pack, run a full calibration cycle through the instrument menu before taking it to site. The laser maps battery state during calibration. Skip this step and the unit will flag premature low-battery warnings during your first alignment session, even with a full charge.

BMS lockout after a Fukuda laser sat unused in a carry case for months

Li-ion cells self-discharge during storage. If a Fukuda multiline laser sits unused long enough, the cell voltage can drop below the BMS's minimum recovery threshold — typically around 2.5V. At that point the BMS enters a protective sleep state and the instrument will not power on or accept a charge. To recover the pack, apply a trickle charge via a compatible Li-ion charger set to recovery mode and hold it there until the cell climbs above 2.8V. Once past that threshold the BMS re-initialises and normal charging resumes.

Readings drifting or resetting mid-session on the FLE-444R

Under sustained laser output, the draw on the cell is steady but non-trivial. If the cell has degraded or is partially discharged, voltage can sag enough mid-session for the instrument's processor to register an undervoltage event and reset — dropping your reference lines without warning. This is not a firmware fault. Check resting cell voltage before deployment: a healthy pack at full charge should read between 4.15V and 4.20V at the terminals. Anything below 4.0V at rest after a full charge indicates cell capacity loss and the pack should be replaced.