About this replacement
Fukuda Multiline Laser FLE-444G / FLG-411QG — 7.4V Li-ion Replacement Battery (FLE-444G)
This 7.4V, 1800mAh Li-ion battery replaces the original pack in the Fukuda FLE-444G and FLG-411QG multiline laser levels. Both models use the same battery bay, connector, and BMS communication protocol. Voltage and capacity match the factory specification exactly.
- FLE-444G and FLG-411QG compatibility: Both models share the same 7.4V two-cell architecture, identical 75.26 × 57.20 × 28.97mm housing, and the same connector pinout. The BMS handshake runs on the same thermistor line, so the instrument reads charge state correctly on either unit without modification.
- Bench tested on actual hardware: We cycled this pack through the FLE-444G's laser initialisation sequence, which draws a short current spike when the diode array powers up. The BMS held without tripping, and the instrument reported accurate charge state throughout the test session.
- Pre-deployment calibration cycle: After fitting this battery, run a full calibration cycle through the instrument menu before taking it to site. The FLE-444G maps battery state during calibration — skip this step and the instrument will throw premature low-battery warnings during the first measurement session, even with a full pack.
FLE-444G shutting down mid-alignment when the laser plane switches axes
The FLE-444G fires multiple laser diodes in sequence when switching between horizontal and vertical planes. Each switch draws a brief but sharp current spike. An aged or deeply discharged cell cannot hold voltage through that spike, and the BMS interprets the drop as an under-voltage fault and cuts output. This is not a firmware issue — it is the cell failing to deliver instantaneous current. A fresh pack at full charge clears the fault immediately, and the instrument resumes normal plane-switching without dropout.
Instrument not recognising new pack after it sat in the carry case for months
Li-ion cells self-discharge during storage. If the pack drops below approximately 2.5V per cell, the BMS enters a deep-sleep lockout state and the instrument will not power on or acknowledge the battery at all. To recover, connect the battery to its charger and leave it for at least 30 minutes — most chargers apply a low-current recovery pulse before entering standard CC/CV mode. Once cell voltage climbs back above 3.0V per cell, the BMS re-initialises and the instrument recognises the pack normally.