Fresenius 120209 Pump Applix Replacement Battery 4.8V 1200mAh

Fresenius Pump Applix — 4.8V Ni-MH Replacement Battery (120209)

This 4.8V, 1200mAh Ni-MH battery is the direct replacement cell for the Fresenius Pump Applix infusion pump and its variants, including the Applix Feeding Pump and Nutrition Applix Smart Long. It matches the OEM voltage rail and connector footprint to the original 120209 specification. The 87.75 x 28.30 x 15.06mm form factor fits within the existing battery bay without modification.

• Applix platform compatibility: The Pump Applix family shares a common 4.8V Ni-MH architecture and BMS handshake across its feeding and infusion variants. All listed models draw from the same battery bay, use the same connector pinout, and communicate state-of-charge through the same charge management circuit.
• Bench tested on actual hardware: We cycled this cell through a full charge-discharge sequence on the Applix platform and confirmed the BMS accepted the new cell, completed its verification pass, and reported charge status correctly after one full conditioning cycle.
• Post-installation self-test protocol: After fitting this battery, allow the pump to complete its full power-on self-test without interruption. The Applix BMS runs a verification sequence at startup — cutting power during this window logs a persistent battery fault that won't clear until the device completes a clean reboot from a full charge.

Why the Applix alarms low battery immediately after a confirmed full charge

The Applix charge management circuit stores calibration data from the previous cell. A new Ni-MH cell presents a different internal resistance profile, and the BMS interprets this mismatch as a partially depleted pack. This is not a fault with the replacement cell — it's a calibration gap. Run one complete charge-discharge-charge cycle and the BMS recalibrates its threshold to the new cell's actual capacity. After that cycle, the low battery alarm clears at the correct state-of-charge point.

Pump will not power on after battery sat in storage

Ni-MH cells self-discharge during storage — if the cell voltage drops below the BMS recovery threshold, the pump will not boot at all, even when connected to the charger. This is a protection cutoff, not a dead cell. Place the device on charge for a minimum of 30 minutes before attempting to power on; the charge IC needs enough voltage present to re-engage the BMS. If the pump still does not respond after 30 minutes on charge, check that the charger output is within the 4.8V nominal range before proceeding.