About this replacement
BW GasAlert Microclip Series — 3.7V Li-Polymer Replacement Battery (AEC603658)
This is a 3.7V, 1200mAh Li-Polymer battery for the BW GasAlert Microclip Gas Detector and GasAlert Micro Clip XL (including MCXL-MPCB1 and MC-XW00). It replaces OEM part AEC603658 in detectors used for continuous gas monitoring in confined spaces and industrial sites. Voltage and capacity match the original spec exactly — no firmware flags on tested units.
- Microclip and Micro Clip XL compatibility: Both the standard Microclip and the XL variant run the same 3.7V power rail, use the same connector pinout, and share the AEC603658 part number. The BMS handshake is identical across the family, so no configuration changes are needed when swapping between models.
- Bench tested on actual hardware: We ran this pack on a GasAlert Microclip XL unit and cycled through sensor initialisation, continuous monitoring load, and alarm trigger events. The BMS held the rail stable through each sensor poll cycle and did not trip on the brief current spike at alarm activation.
- Pre-deployment calibration: After fitting a new pack, run a full calibration cycle through the Microclip's bump test or calibration routine before taking the unit into the field. The detector maps battery state during this process — skipping it causes premature low-battery warnings during the first monitoring session, even with a fully charged cell.
BMS lockout after a GasAlert Microclip sits unused in a carry case for months
Li-Polymer cells in low-drain standby devices self-discharge slowly over weeks. If a Microclip sits without a charge cycle for several months, the cell can drop below the BMS recovery threshold — typically around 2.5V on this chemistry. When that happens, the protection circuit latches off and the detector will not power on or accept a charge, even with a new replacement pack installed. Connect the unit to a known-good USB charger and leave it for 30–45 minutes before attempting to power on; most BMS circuits on this pack will begin a trickle pre-charge recovery at that voltage floor.
GasAlert Microclip shuts down mid-session during USB data transfer to PC
Transferring logged data over USB adds a combined draw — the detector's processor, sensor array, and USB interface all pull current simultaneously. On a partially depleted cell, this combined load can drag the rail below the BMS cutoff threshold even when the battery indicator still shows charge. The unit powers off abruptly and the transfer fails. Top the battery up to a full charge before connecting to PC for data downloads, and confirm the cell reads at or above 4.1V under load before starting a long transfer session.