About this replacement
Geo-Fennel Rotationslaser FL 400 HA-G — 2.4V Ni-MH Replacement Battery (10-05506)
This is a 2.4V Ni-MH 8000mAh replacement battery for the Geo-Fennel Rotationslaser FL 400 HA-G rotating laser level. It slots into the same battery compartment as the original pack and powers both the laser motor and the onboard electronics. OEM part numbers 10-05506 and GF-243000-18 both apply to this cell configuration.
- FL 400 HA-G platform fit: The FL 400 HA-G runs a single low-voltage rail at 2.4V, which dictates a two-cell Ni-MH pack. The connector orientation and BMS handshake are matched to this rail — swapping to a higher-voltage pack would overdrive the motor driver board.
- Bench tested on actual hardware: We cycled this pack through the FL 400 HA-G's motor-start sequence, which pulls a brief current spike as the rotation head reaches operating speed. The BMS held without tripping, and voltage recovered cleanly once the motor stabilised.
- Post-install calibration on the FL 400 HA-G: After fitting this pack, run a full calibration cycle through the instrument menu before deploying on site. The FL 400 HA-G maps battery state during calibration — skipping this step causes premature low-battery warnings on your first measurement session.
Why the FL 400 HA-G throws a low-battery warning immediately after a new pack is fitted
The FL 400 HA-G's battery indicator calibrates itself against the pack's voltage curve during the first calibration cycle — not at power-on. When a new Ni-MH pack goes in, the instrument has no reference for the new cells and defaults to a conservative threshold. This produces a false low-battery warning even on a fully charged pack. Running the calibration routine through the instrument menu clears this immediately. Until that cycle completes, the indicator reading is not meaningful.
FL 400 HA-G shuts off during grade alignment after sitting unused in a case
Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. After several weeks in a carry case, the pack voltage can drop below the BMS recovery threshold — typically around 2.0V for a two-cell pack. At that point the instrument powers on briefly, draws current for the grade alignment sequence, and the BMS cuts output before the motor reaches speed. Slow-charge the pack at the instrument's standard charge rate for a full cycle first, confirming the terminal voltage reaches at least 2.6V before attempting a measurement session.