Signal Fire ZS-8848 Replacement Battery 11.1V 7800mAh Li-ion

Signal Fire AI-6 / SA-2 — 11.1V Li-ion Replacement Battery (ZS-8848)

This is an 11.1V, 7800mAh Li-ion replacement battery for the Signal Fire AI-6 and SA-2 laser distance measuring instruments. It uses OEM part number ZS-8848 and slots directly into the battery compartment on both models. Capacity matches the original pack at 86.58Wh.

• AI-6 and SA-2 compatibility: Both models share the same battery bay geometry, connector pinout, and BMS communication protocol — one pack covers both. The voltage rail is identical across the AI-6 laser rangefinder and SA-2 variants, so no firmware difference affects pack recognition.
• Bench tested on actual hardware: We cycled this pack through cold-start, sustained laser measurement load, and USB data-transfer draw simultaneously. The BMS held stable across all three load states with no false cutoff or error flags triggered.
• First-use calibration cycle: After installing a new pack, run a full calibration cycle through the instrument menu before field deployment. The AI-6 maps battery state during calibration — skipping this step causes premature low-battery warnings to appear during your first measurement session even when charge is adequate.

AI-6 shutting down mid-measurement with no low-battery warning

The AI-6 draws a current spike each time the laser module fires and the rangefinder processor logs a reading. On a degraded or deeply discharged pack, this spike is enough to trip the BMS overcurrent threshold even when the displayed charge level looks acceptable. The instrument cuts power immediately — no warning, no graceful shutdown. A new pack with healthy cell impedance absorbs these spikes without triggering cutoff. If shutdowns persist after replacing the pack, check that the calibration cycle was completed, as an uncalibrated pack can cause the BMS to misread the load threshold.

Pack will not charge after the instrument sat unused for months

Li-ion cells that sit uncharged for extended periods can self-discharge below the BMS recovery threshold — typically around 2.5V per cell. When this happens, the charger sees the pack as a fault condition and refuses to initiate a charge cycle. The BMS needs a recovery voltage applied before normal charging resumes. Place the pack on charge for 30–60 seconds, disconnect, then reconnect — some chargers will re-poll the pack and detect a recoverable voltage. If the pack has dropped below 7.5V total, recovery is unlikely and the pack should be replaced.