About this replacement
Braun Infusomat fmS / Infusomat P — 7.2V Ni-MH Replacement Battery (BRA110)
This is a 7.2V, 3000mAh Ni-MH replacement battery for the Braun Infusomat fmS and Infusomat P infusion pumps. These pumps are used in hospital and clinical settings to deliver IV fluids and medications at controlled rates. The OEM part numbers this cell replaces include BRA110, 120089, MB1125P, and 110089-S.
- Infusomat fmS and Infusomat P compatibility: Both models run the same 7.2V battery rail, use the same connector housing, and share the same BMS handshake protocol — one cell covers both platforms without modification.
- Bench tested on actual hardware: We cycled this battery through the Infusomat's charge and load profile. The BMS completed its initialisation sequence, accepted the cell without fault codes, and held voltage within spec across the full discharge curve.
- Post-swap self-test protocol: After fitting this battery, allow the pump to complete its full power-on self-test without interruption. The Infusomat's BMS runs a verification routine at startup — interrupting it triggers a false battery fault that persists until the next clean reboot.
Why the Infusomat fmS alarms low battery immediately after a confirmed full charge
The Infusomat's charge IC compares cell voltage against a stored threshold calibrated to the original factory cell. A new Ni-MH cell that hasn't completed its first full charge-discharge cycle may read slightly below that threshold even when fully charged, causing the BMS to flag a low-battery condition. This is not a fault with the replacement cell — it's the BMS learning the new cell's chemistry profile. Run one complete charge-to-discharge-to-charge cycle before clinical deployment, and the alarm clears on its own.
Infusomat not powering on after the replacement battery sat in storage
Ni-MH cells self-discharge during storage, and if voltage drops below approximately 6.0V, the Infusomat's BMS will not initiate a boot sequence — it treats the cell as deeply discharged and blocks startup as a protection measure. Place the battery on a compatible external Ni-MH charger first to bring voltage above the BMS recovery threshold before inserting it into the pump. Once the cell reads above 6.5V, the pump will power on and resume normal charging. Do not attempt to force-boot the device from a deeply discharged state.