Merck Millipore MAS-100 Air Sampler 10.8V Replacement Battery

Merck Millipore Air Sampler MAS-100 — 10.8V Ni-CD Replacement Battery (110518-U)

This is a 10.8V 1800mAh Ni-CD battery for the Merck Millipore MAS-100 portable microbial air sampler. It fits the MAS-100, MAS-AC-6009, and MAS-AC-7009 units used in pharmaceutical cleanrooms, hospital pharmacies, and controlled sterile environments. Capacity matches OEM at 1800mAh (19.44Wh).

• MAS-100 series compatibility: The MAS-AC-6009 and MAS-AC-7009 share the same 10.8V three-cell Ni-CD architecture and connector pinout as the base MAS-100. All three models use the same BMS handshake protocol and charge termination logic, so one battery covers the full platform.
• Bench tested on actual hardware: We cycled this battery through the MAS-100 charge sequence and confirmed the BMS accepted the cell pack without fault codes. Charge termination triggered correctly at full capacity, and the device passed its post-charge self-test on the first cycle.
• Post-swap self-test protocol: After installing this battery, let the MAS-100 complete its full power-on self-test without interruption. The BMS runs a verification routine at startup — cutting power during this window triggers a battery fault flag that persists until the next clean reboot cycle.

Why the MAS-100 BMS rejects a new Ni-CD cell on first contact

The MAS-100 charge controller uses delta-V peak detection tuned to a conditioned Ni-CD cell. A new, uncycled pack has a flatter voltage curve during the first charge, which can cause the controller to terminate early or flag a fault. This is not a defective battery — it is the charge IC applying conservative limits to an unfamiliar cell signature. One full charge-discharge cycle normalises the cell's internal resistance and delta-V response. After that cycle, the charge controller reads the pack correctly and accepts a full charge.

Charge indicator stalls below 100% after battery swap

A stalled charge indicator on the MAS-100 after a battery swap usually means the BMS has not yet completed its learn cycle on the new cell. Ni-CD cells from storage carry residual voltage, but their capacity profile is uncharacterised — the charge IC holds back until it maps the cell's actual charge acceptance curve. Run one uninterrupted full charge from below 20% to 100%, then discharge the unit through normal sampling use before recharging. After this single cycle, the indicator tracks accurately and the BMS updates its capacity registers.