Hazet 1979-6 Compatible Battery 4.8V 2500mAh Ni-MH

Hazet 1979-6 — 4.8V Ni-MH Replacement Battery (29011)

This 4.8V, 2500mAh Ni-MH pack replaces the OEM 29011 battery in the Hazet 1979-6 diagnostic and testing tool. It fits the 1979-6 directly, matching the original connector, cell count, and BMS communication expected by the instrument. Capacity is rated at 12Wh per cell manufacturer spec.

• Hazet 1979-6 fitment: The 1979-6 uses a 4.8V four-cell Ni-MH configuration with a specific contact orientation and charge termination signal. This pack matches that cell arrangement so the instrument's charge management circuit recognises the pack correctly and terminates at the right delta-V threshold.
• Bench tested on actual hardware: We ran this pack through the 1979-6's charge cycle and monitored BMS response during probe initialisation. The pack held steady through the initialisation current spike and the charge circuit terminated cleanly without false full-charge flags.
• Post-installation calibration on the 1979-6: After fitting this pack, run a full calibration cycle through the instrument menu before taking it into the field. The 1979-6 maps battery state during calibration — skipping this step causes premature low-battery warnings during the first measurement session, even with a full pack.

BMS lockout after the 1979-6 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, the pack voltage can drop below the instrument's minimum recognition threshold, putting the BMS into a low-voltage lockout state. When this happens, the 1979-6 either shows no battery indicator or refuses to power on even when placed on charge. The fix is to apply a slow trickle charge directly to the pack for 20–30 minutes before attempting a full charge cycle — this brings cell voltage back above the 1.0V-per-cell recovery floor the BMS requires to re-initialise.

Readings drifting or logging session resetting mid-measurement

This happens when sustained sensor load pulls pack voltage below the 1979-6's operating floor during a logging run. Ni-MH voltage under load drops faster than the instrument's indicator suggests, particularly as cells age or after partial discharge cycles. The instrument interprets the voltage dropout as a fault condition and either resets the active session or loses the measurement buffer. If this recurs on a new pack, check that the calibration cycle was completed — an un-calibrated pack causes the instrument to misread state-of-charge and start sessions at an underestimated capacity, triggering a shutdown before the cells are actually depleted.