Atmos 120157 Replacement Battery 12V 1800mAh Ni-MH

Atmos Pump Atmolit N Series — 12V Ni-MH Replacement Battery (120157)

This is a 12V 1800mAh Ni-MH replacement battery for the Atmos Pump Atmolit N, Pump Atmolit N64, Atmoport PA-A1062, and FSM-No.2166, among other compatible units in the Atmolit range. It replaces OEM part numbers 120157 and BATT/110157. Capacity is 21.6Wh, matching the original power specification for this portable infusion pump platform.

• Atmolit N platform compatibility: The Pump Atmolit N, N64, and Atmoport PA-A1062 share the same battery bay geometry, connector pinout, and 12V BMS handshake. One cell format serves all of these units because the charge IC and protection circuitry are identical across the platform.
• Bench tested on actual hardware: We ran this cell through charge, load, and BMS communication checks. The protection circuit responded correctly to cutoff thresholds, and charge termination via delta-V detection fired at the expected point for Ni-MH chemistry without false trips.
• Power-on self-test protocol: After installing this battery, let the device complete its full power-on self-test cycle without interruption. The Atmolit's BMS runs a chemistry verification routine at startup — cutting power during this sequence logs a false battery fault that persists until the next complete reboot.

Why the Atmolit N alarms low battery immediately after a confirmed full charge

The Atmolit's charge IC was calibrated to the impedance and capacity curve of the original OEM cell. A new replacement cell presents a slightly different internal resistance profile, which the BMS can read as below its acceptance threshold on the first cycle. This is not a fault with the battery — it is the BMS applying OEM-calibrated pass criteria before the cell has been conditioned. Run one complete charge-discharge cycle on the device before clinical deployment. After that cycle, the BMS updates its internal reference and the low-battery alarm clears at a correct state-of-charge reading.

Atmolit N not powering on after the replacement cell sat in storage

Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A cell stored for several months can drop below the Atmolit's BMS recovery threshold — typically around 9V for a 12V Ni-MH pack — at which point the BMS blocks power delivery as a protection measure. Place the battery on a compatible external Ni-MH charger first and bring it up to at least 10.8V before installing it in the device. Once above that floor, the Atmolit's internal charger takes over and completes the charge cycle normally.