About this replacement
Spectra Precision GL622 / GL612 Series — 4.8V Ni-MH Replacement Battery (Q104782)
This is a 4.8V Ni-MH replacement battery rated at 10000mAh (48Wh) for the Spectra Precision GL622 rotary laser level and related models. It fits the GL622, GL612, UL633N, and DG613 platforms. The battery powers the laser's rotating motor and onboard electronics during grading, levelling, and alignment work on job sites.
- GL622 / GL612 / UL633N / DG613 compatibility: These models share the same 4.8V cell configuration, physical housing dimensions, and connector pinout. The BMS handshake protocol is identical across the family, so one pack services the full platform without modification.
- Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on GL622 hardware. The BMS held stable voltage through motor spin-up, and the instrument's charge indicator tracked accurately from 100% to cutoff without false low-battery interrupts.
- Post-install calibration on the GL622: After fitting this battery, run a full self-level calibration cycle through the GL622's instrument menu before field use. The unit maps battery state during that cycle. Skipping it causes the low-battery warning to trip early on the first job, even with a fully charged pack.
GL622 BMS cutoff at motor spin-up
When the GL622 starts its rotating head, the motor draws a sharp current spike in the first half-second. A degraded or deeply discharged pack can't sustain that spike, so the BMS trips and the unit shuts off immediately after switching on. This isn't a fault with the instrument — it's the protection circuit responding to a cell that can't hold voltage under load. With a fresh pack at full charge (5.5V–5.8V resting on Ni-MH), the spin-up spike stays well inside the BMS threshold and the laser starts cleanly.
GL622 not recognising a new pack after months in storage
Ni-MH cells self-discharge during storage — this pack can drop below 3.5V if left unused for several months. At that voltage, the BMS enters sleep mode and the GL622 shows no charge state or fails to power on at all. The fix is a slow trickle charge at 0.1C for 2–4 hours before attempting a full charge cycle. Once the cells recover above 4.2V, the BMS wakes, the instrument recognises the pack, and normal charging resumes.