About this replacement
Baxter Healthcare AS40 Series — 6V Ni-MH Replacement Battery (NH6211WC)
This is a 6V, 2000mAh Ni-MH replacement battery for Baxter Healthcare AS40, AS40A, AS41, and AS50 infusion pumps. It replaces OEM part numbers NH6211WC, MDE2910, OM10669, and B11056. The cell format and connector match the original battery compartment on this pump family.
- AS40 pump family compatibility: The AS40, AS40A, AS41, and AS50 share a common 6V battery rail and the same BMS handshake protocol. Any pump in this series drawing from that rail will accept this cell without modification to connectors or firmware thresholds.
- Bench tested on actual hardware: We ran this cell through the AS40's power-on self-test sequence and confirmed the BMS handshake completes correctly. The protection circuit held within spec under the pump's steady infusion load profile.
- Self-test cycle before clinical use: After installing this battery, allow the pump to complete one full charge-discharge cycle before placing it in clinical service. The BMS calibrates its capacity register on the first cycle — skipping this step causes the charge indicator to report incorrectly until the learn cycle finishes.
Device not completing boot sequence after battery swap
The AS40 runs a power-on self-test that checks battery voltage before the pump reaches the ready state. A new Ni-MH cell that has partially self-discharged in storage can sit just below the BMS's minimum boot threshold — enough charge to light the display, but not enough to pass the self-test gate. Charge the battery fully before the first power-on. If the pump still fails to boot after a confirmed full charge, leave it on charge for an additional two hours to let the cell settle above 7.0V open-circuit.
Low battery alarm triggering immediately after a confirmed full charge
This happens when the pump's BMS compares the new cell's voltage curve against the threshold it learned from the previous battery. Ni-MH cells peak at a slightly different voltage profile on the first few cycles, and the BMS reads that as a low-state-of-charge condition. Run one complete charge-discharge cycle — let the pump discharge to the automatic cutoff, then recharge fully to 100%. After that first cycle, the BMS recalibrates and the alarm clears.