Systronik 4-HXAAL Compatible Battery 4.8V 2000mAh Ni-MH

Systronik 4-HXAAL — 4.8V Ni-MH Replacement Battery (22996)

This is a 4.8V 2000mAh Ni-MH battery for the Systronik 4-HXAAL portable survey and test instrument. It replaces OEM part numbers 22996 and 91507801. Capacity matches original specification at 9.6Wh.

• 4-HXAAL power rail: The 4-HXAAL runs its sensor modules and display from a single 4.8V Ni-MH pack. The BMS monitors cell voltage across all four cells in series — one weak cell pulls the whole pack below cutoff threshold and the instrument shuts down even with remaining capacity.
• Bench tested on actual hardware: We cycled this pack through probe initialisation draws and sustained logging loads. The BMS held cutoff thresholds correctly and cell balance stayed within spec across repeated charge-discharge cycles.
• First-use calibration cycle: After installing this pack, run a full calibration cycle through the instrument's menu before going into the field. The 4-HXAAL maps battery state during calibration. Skipping this step causes premature low-battery warnings on your first measurement session even when the pack is fully charged.

BMS lockout after the 4-HXAAL sat unused in a carry case for months

Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. After several months in storage, cell voltage can drop below the BMS recovery threshold — typically around 0.9V per cell on a 4-cell pack. When the instrument's BMS reads voltage below that floor, it refuses to accept a charge and the device shows no response on the charge indicator. Place the pack on a compatible charger that supports trickle or recovery mode to bring cell voltage back above 1.0V per cell before attempting a standard charge cycle.

Readings drifting or resetting mid-session during sustained sensor logging

Under continuous sensor load, sustained current draw can cause voltage to sag across the pack, particularly as cells age or a new pack hasn't completed its first full calibration cycle. When pack voltage dips momentarily below the instrument's operating threshold, the 4-HXAAL resets its measurement session rather than shutting down cleanly — logs may appear incomplete or readings jump. Run the calibration cycle first, then confirm resting pack voltage sits above 5.0V before starting a long logging session.