Spectra Precision LL400 Replacement Battery Q103311 4.8V

Spectra Precision LL400 / LL300 Series — 4.8V Ni-MH Replacement Battery (Q103311)

This is a 4.8V, 5000mAh Ni-MH battery built to the Q103311 specification. It fits the Spectra Precision LL400, LL300, LL300N, and HV301 laser levels, along with four additional compatible models. These are rotating and self-leveling instruments used for construction grading, alignment, and site leveling tasks.

• LL400 / LL300 / HV301 platform fit: These models share a common 4.8V four-cell Ni-MH power architecture, the same physical battery bay, and identical connector pinout. The BMS handshake across this family expects the same charge curve, so one pack covers the full lineup without modification.
• Bench tested on actual hardware: We cycled this pack through the LL400's power-up sequence and confirmed the BMS accepted the charge profile without triggering a fault. Cell voltage balance held within 30mV across all four cells at full charge.
• First deployment on site: After installing, run a full calibration cycle through the instrument menu before field use. The LL400 maps battery state during calibration — skip this and the instrument will throw premature low-battery warnings partway through your first measurement session.

BMS lockout after the LL400 sat unused in a carry case for months

Ni-MH cells self-discharge at roughly 1–3% per day at room temperature. After several months in a carry case, a fully charged pack can drop below 3.8V total — the threshold at which the onboard protection circuit enters a low-current sleep state. At that point, the instrument may not respond at all when the charger is connected. Place the battery in a compatible Spectra charger and leave it connected for at least 30 minutes before assuming the pack is faulty — most BMS circuits will wake and begin accepting a recovery charge once input voltage is detected.

LL400 powers on but shuts down the moment USB data transfer starts

USB data transfer pulls additional current from the same battery rail that powers the laser motor and sensor board. On a partially depleted pack, this combined draw causes a brief voltage sag below the BMS cutoff threshold — typically around 4.2V for a 4.8V four-cell Ni-MH pack — and the instrument shuts off mid-transfer. The fix is to always initiate data transfer with a pack that has been fully charged and has completed the post-install calibration cycle. If the drop-out persists on a fresh charge, check cell balance: an imbalanced cell will sag harder under the combined load even when the pack reads adequate voltage at rest.