Honeywell Lumidor Micromax Plus 4.8V Ni-MH Replacement Battery

Honeywell Lumidor Micromax Plus / Micromax Pro — 4.8V Ni-MH Replacement Battery (4956 / MPRO-BPR)

This is a 4.8V, 2000mAh Ni-MH replacement battery for the Honeywell Lumidor Micromax Plus and Micromax Pro portable gas detectors. It slots into the battery compartment and powers the sensor array, display, and alarm circuitry during field monitoring sessions. Voltage and capacity match the OEM spec — 4.8V nominal, 9.6Wh.

• Micromax Plus and Micromax Pro compatibility: Both units run the same 4.8V four-cell Ni-MH configuration with an identical connector pinout and BMS handshake protocol. A single pack covers either instrument without modification.
• Bench tested on actual hardware: We cycled this pack through the Micromax Pro under continuous sensor load — pumped-draw mode with alarm circuit active. The BMS held voltage above the 4.2V cutoff threshold throughout the discharge curve with no mid-cycle dropout.
• Pre-deployment calibration cycle: After fitting this pack, run a full calibration cycle through the instrument menu before field use. The Micromax maps battery state during calibration — skipping this step causes premature low-battery warnings on the first measurement session even when the pack is fully charged.

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

Ni-MH cells self-discharge at roughly 1–3% per day. A pack stored for three or more months in a case will drop below the BMS recovery threshold — typically around 3.6V for a four-cell pack. When that happens, the charger sees a dead circuit and refuses to initiate a charge cycle. The fix is a trickle-charge at low current (100–150mA) for 30–60 minutes to bring cell voltage above the recovery floor before switching to normal charging. Most OEM chargers do this automatically if you leave the pack connected — the charger will click into fast-charge mode once the threshold is cleared.

Micromax Plus shutting down mid-measurement with a new pack installed

This usually isn't a faulty pack — it's a BMS trip caused by the current spike when the sensor module powers up or re-initialises during a session. The gas sensor draw in the Micromax can spike briefly above the BMS overcurrent threshold if the instrument hasn't mapped the new pack's internal resistance. Running one full discharge-to-cutoff cycle and then a full charge resets the BMS reference values. After that conditioning cycle, mid-session shutdowns typically stop — confirm the pack reads above 4.6V on a multimeter before the next deployment.