Fresenius MCM 404 Replacement Battery 12V 1800mAh

Fresenius MCM 404 / Volumed VP 2000 Series — 12V Ni-MH Replacement Battery (120088-1)

This is a 12V 1800mAh Ni-MH battery for the Fresenius MCM 404 and MCM 504 infusion pumps, and the Volumed VP 2000 and VP 5000 volumetric pumps. It replaces OEM part numbers 120088-1, BATT/110088, 20022, 120022P, and BATT/110022. The battery provides backup power during patient transport and mains interruptions in clinical settings.

• MCM 404, MCM 504, VP 2000, VP 5000 compatibility: These models share the same 12V battery rail, connector pinout, and BMS handshake protocol, which is why a single cell pack covers all four pump platforms without modification.
• Bench tested on actual hardware: We ran this cell through full charge-discharge cycles on the MCM 404 platform. The BMS completed its verification handshake without fault flags and accepted the cell across the pump's expected load profile.
• Power-on self-test protocol: After installing this battery, let the pump complete its full startup self-test without interruption. Fresenius infusion pumps run a BMS verification sequence at boot — cutting power during this window triggers a false battery fault that persists until the next clean reboot cycle.

Why the MCM 404 shows a battery fault after a confirmed full charge

The MCM 404's charge IC uses chemistry-specific thresholds calibrated to a cell that has completed at least one full cycle. A new Ni-MH cell has a slightly higher internal resistance before the first cycle, which the BMS can interpret as a degraded or incompatible pack. The pump may flag a low-battery or fault alarm even when the indicator shows full. Running one complete charge-discharge cycle before clinical use allows the BMS to recalibrate its baseline and clear the fault.

Pump will not power on after the replacement battery sat in storage

Ni-MH cells self-discharge at roughly 1–2% per day during storage. If the battery arrived or sat unused for several weeks, its resting voltage may have dropped below the MCM 404's BMS recovery threshold — typically around 10.8V for a 12V pack — causing the pump to refuse to boot entirely. Connect the pump to mains power first and allow a supervised charge cycle to complete before attempting to run on battery alone. Once the cell reaches approximately 12.0V under charge, the BMS will re-initialise and the pump will boot normally.